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From: blog630 on 23 Apr 2008 13:20
Wholesale Headset Microphone - Chinese Headset Microphone Manufacturer

Headset Microphone WebSite Link:
http://www.chinese-microphone.com/Headset-Microphones.html

China GuangZhou TianTuo Microphone Manufacturing Co., Ltd WebSite:
http://www.chinese-microphone.com/


Microphone Products are: Wireless Microphones, Conference Microphones,
Headset Microphones, and Lapel Microphones, interview microphones,
wired microphones, musical instrument microphones, drum microphones,
teaching microphones, recording microphones, computer's USB
microphones and microphone accessories and So on.




Optically coupled headset and microphone - Patent 7072475 Login or
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| Data Services | Help Title: Optically coupled headset and microphone
Document Type and Number: United States Patent 7072475 Link to this
page: http://www.freepatentsonline.com/7072475.html Abstract:
Apparatus and methods for transferring audio between a headset and
electronic equipment over an optical link. The apparatus includes an
electro-optical interface for electrically connecting to the
electronic equipment, an optical link, and an electro-optical headset.
Audio from the electronic equipment modulates a light source in the
electro-optical interface. A modulated light signal is transmitted
through the optical link to the electro-optical headset where it is
demodulated and reproduced as the original audio in the ear of a user
wearing the headset. Also, another audio from the user's mouth
produces another modulated light signal in the electro-optical
headset. The other modulated light signal is transmitted through the
optical link to the electro-optical interface where it is demodulated
to provide the other audio to the electronic equipment. The non-
electrical optical link may improve audible communications between the
electronic equipment and the headset in radio-frequency noisy
environments. Also, the non-electrical optical link may prevent
coupling with an aerial of the electronic equipment and improve radio
propagation. Representative Image: Inventors: Denap, Frank A.
(Millbrae, CA, US) Roscoe, Timothy (San Francisco, CA, US) Evans,
Arvid (Suisun City, CA, US) Application Number: 09/893136 Filing Date:
06/27/2001 Publication Date: 07/04/2006 View Patent Images: Images are
available in PDF form when logged in. To view PDFs, Login or Create
Account (Free!) Referenced by: View patents that cite this patent
Export Citation: Click for automatic bibliography generation Assignee:
Sprint, Spectrum L. P. (US) Primary Class: 381/74 Other Classes:
455/569.100, 381/172, 398/141, 398/134 International Classes: H04R1/10
Field of Search: 381/375, 398/132-134, 381/74, 398/90, 700/94,
381/172, 381/370, 381/309-311, 398/140-142 US Patent References:
2835744May, 1958Harris381/172Microphone3781092December, 1973Sussman et
al.359/227MONITORING SYSTEM4543961October, 1985Brown600/480Data
transmission system4956877September, 1990Kroll et al.398/170Optical
fiber reflective signal modulation system5333205July, 1994Bogut et al.
381/172Microphone assembly5524275June, 1996LindellAveraged RF exposure
control http://www.chinese-microphone.com/Headset-Microphones.html
5812295September, 1998Kitasagami398/38Optical subscriber transmission
system and subscriber unit used in such5854970December,
1998KivelaAccessory RF unit for hand-held wireless telephone
systems6055500April, 2000Terui et al.704/270Information transfer,
recording and reproducing device6154301November,
2000Harvey398/213Fiber optic receiver6166707December, 2000Painter et
al.Antenna shroud for a portable communications
device20010034253October, 2001Ruschin455/569Headset based on optical
transmission and cellular communications system employing such a
headset Foreign References: JP3238936October, 1991METHOD AND DEVICE
FOR MANAGING OPERATION OF PLANTJP4220851August, 1992 Primary Examiner:
Le, Huyen Assistant Examiner: Chau, Corey Claims: We claim: 1. An
electro-optical headset comprising: an electro-optical interface for
receiving a first electrical signal representative of first audio and
for producing a first modulated light signal based on the first
electrical signal, and for receiving a second modulated light signal
and demodulating the second modulated light signal to produce a second
electrical signal representative of second audio; an optical link
having a first end and a second end, the first end being coupled to
the electro-optical interface for receiving the first modulated light
signal and for transmitting the second modulated light signal; an
optical receiver coupled to the second end of the optical link for
receiving the first modulated light signal, and for demodulating the
first modulated light signal to produce a third electrical signal
representative of the first audio; a headset speaker element
electrically connected with the optical receiver for receiving the
third electrical signal and producing first sound waves based on the
third electrical signal; and a microphone element coupled to the
second end of the optical link for receiving the first modulated light
signal and for transmitting the second modulated light signal, and for
modulating the first modulated light signal to produce the second
modulated light signal representative of the second audio; wherein the
microphone element comprises: an electrical microphone for receiving
second sound waves representative of the second audio and for
producing a fourth electrical signal based on the second sound waves;
an electro-optical shutter electrically connected to the electrical
microphone for receiving the first modulated light signal and
modulating the first modulated light signal to produce the second
modulated light signal, wherein the second modulated light signal is
representative of the fourth electrical signal; and a directional
optical coupler for receiving the first modulated light signal from
the second end of the optical link and directing the first modulated
light signal to the electro-optical shutter, and for receiving the
second modulated light signal from the electro-optical shutter and
directing the second modulated light signal to the second end of the
optical link. 2. The electro-optical headset of claim 1, further
comprising at least one electrical audio connector coupled with the
electro-optical interface for receiving the first electrical signal
from electronic equipment and for transmitting the second electrical
signal to the electronic equipment. 3. The electro-optical headset of
claim 1, wherein the optical receiver is a photo-voltaic cell. 4. The
electro-optical headset of claim 1, wherein the electro-optical
shutter is a liquid crystal display element. 5. The electro-optical
headset of claim 1, wherein the electrical microphone is a
piezoelectric microphone. 6. The electro-optical headset of claim 1
wherein the first modulated light signal is generated by a laser light
emitting diode. 7. The electro-optical headset of claim 1 further
comprising: a directional optical coupler for receiving the first
modulated light signal from the second end of the optical link and
directing the first modulated light signal to the optical receiver and
the microphone element, and for receiving the second modulated light
signal from the microphone element and directing the second modulated
light signal to the second end of the optical link. 8. The electro-
optical headset of claim 7 further comprising: an optical splitter for
receiving the first modulated light signal from the directional
optical coupler and directing the first modulated light signal to the
optical receiver along a first optical path and directing the first
modulated light signal to the microphone element along a second
optical path. 9. The electro-optical headset of claim 1, further
comprising: a directional optical coupler for receiving the first
modulated light signal from the electro-optical interface and
directing the first modulated light signal to the first end of the
optical link, and for receiving the second modulated light signal from
the first end of the optical link and directing the second modulated
light signal to the electro-optical interface. 10. The electro-optical
headset of claim 1, wherein the electro-optical interface comprises: a
pulse width modulation circuit for receiving the first electrical
signal and producing the first modulated light signal, wherein the
first modulated light signal is pulse width modulated based on the
first electrical signal; and a sample-and-hold circuit for receiving
the second modulated light signal and producing the second electrical
signal, wherein the second modulated light signal is amplitude
modulated based on the second audio. 11. The electro-optical headset
of claim 1 wherein the electro-optical interface comprises a
semiconductor device for receiving the second modulated light signal,
and wherein the semiconductor device is selected from the group
consisting of a photodiode and a phototransistor. 12. A system
comprising: a mobile station; an electro-optical interface for
receiving a first electrical signal from the mobile station
representative of first audio, and for producing a first modulated
light signal based on the first electrical signal, and for receiving a
second modulated light signal and demodulating the second modulated
light signal to produce a second electrical signal for transmission to
the mobile station representative of second audio; an optical link
having a first end and a second end, the first end being coupled to
the electro-optical interface for receiving the first modulated light
signal and for transmitting the second modulated light signal; an
optical receiver coupled to the second end of the optical link for
receiving the first modulated light signal, and for demodulating the
first modulated light signal to produce a third electrical signal
representative of the first audio; a headset speaker element
electrically connected with the optical receiver for receiving the
third electrical signal and producing first sound waves based on the
third electrical signal; and a microphone element coupled to the
second end of the optical link for receiving the first modulated light
signal and for transmitting the second modulated light signal, and for
modulating the first modulated light signal to produce the second
modulated light signal representative of the second audio; wherein the
microphone element comprises: an electrical microphone for receiving
second sound waves representative of the second audio and for
producing a fourth electrical signal based on the second sound waves;
an electro-optical shutter electrically connected to the electrical
microphone for receiving the first modulated light signal and
modulating the first modulated light signal to produce the second
modulated light signal wherein the second modulated light signal is
representative of the fourth electrical signal; and a directional
optical coupler for receiving the first modulated light signal from
the second end of the optical link and directing the first modulated
light signal to the electro-optical shutter, and for receiving the
second modulated light signal from the electro-optical shutter and
directing the second modulated light signal to the second end of the
optical link. 13. The system of claim 12, wherein the electro-optical
shutter is a liquid crystal display element. 14. The system of claim
12, wherein the electrical microphone is a piezoelectric microphone.
15. The system of claim 12 wherein the first modulated light signal is
generated by a laser light emitting diode. 16. An electro-optical
headset comprising; a pulse width modulation circuit for receiving a
first electrical signal representative of first audio and producing a
first modulated light signal from a laser light emitting diode,
wherein the first modulated light signal is pulse width modulated
based on the first electrical signal; a sample-and-hold circuit for
receiving a second modulated light signal in a photo-detector and
producing a second electrical signal representative of second audio,
wherein the second modulated light signal is amplitude modulated based
on the second audio; a first directional optical coupler for receiving
the first modulated light signal from the pulse width modulation
circuit and directing the first modulated light signal to the first
end of the optical link, and for receiving the second modulated light
signal from the first end of the optical link and directing the second
modulated light signal to the photo-detector in the sample-and-hold
circuit; an optical link having a first end and a second end, the
first end being coupled to first directional optical coupler for
receiving the first modulated light signal and for transmitting the
second modulated light signal; a second directional optical coupler
coupled to the second end of the optical link for receiving the first
modulated light signal from the second end of the optical link and for
transmitting the second modulated light signal to the second end of
the optical link; a photo-voltaic cell coupled to the second
directional optical coupler for receiving the first modulated light
signal, and for demodulating the first modulated light signal to
produce a third electrical signal representative of the first audio; a
headset speaker element electrically connected with the photo-voltaic
cell for receiving the third electrical signal and produci

ng first sound waves based on the third electrical signal, an optical
splitter for receiving the first modulated light signal from the
second directional optical coupler and directing the first modulated
light signal to the photo-voltaic cell along a first optical path; an
electrical microphone for receiving second sound waves representative
of the second audio and for producing a fourth electrical signal based
on the second sound waves representative of the second audio; and a
liquid crystal display element electrically connected to the
electrical microphone for receiving the first modulated light signal
along a second optical path from the optical splitter and modulating
the first modulated light signal to produce the second modulated light
signal, wherein the second modulated light signal is representative of
the fourth electrical signal, and wherein the second modulated light
signal traverses a third optical path and is received by the second
directional optical coupler for transmission to the second end of the
optical link. Description: FIELD OF INVENTION The present invention
relates to electronic equipment having an audio output and/or input.
More specifically, it relates to a headset and/or microphone that are
optically coupled to the electronic equipment. BACKGROUND OF THE
INVENTION Many pieces of electronic equipment produce an audio output,
receive an audio input, or both. For example, conventional or cellular
telephones, walkie-talkies, compact disc players, home audio
equipment, portable radio receivers, and micro-cassette recorders
involve providing audible communications to a user, or involve
accepting audible communications from the user. In order to reduce the
effects of ambient audible noise interfering with the audible
communications, or to increase the user's privacy, the user may
connect an headset and/or microphone to the equipment. In this manner,
the user may hear the audible communications through the headset and/
or speak the audible communications into the microphone. The headset
may integrate the microphone into a single unit for wearing by the
user. The headset typically connects electrically to the electrical
equipment through a conductive wire. An audio signal that is an
electrical representation of the audible communications travels from
the electrical equipment to the headset through the conductive wire.
The headset is typically an electromagnetic or piezoelectric device
that responds to the current or voltage on the conductive wire, and
vibrates in response to the audio signal to reproduce the audible
communication. Similarly, the microphone also typically connects
electrically to the electrical equipment through a conductive wire.
The microphone is typically a piezoelectric or ribbon magnetic device
that responds to the audible communications from the user, and
converts the audible communications into an audio signal that is an
electrical representation of the audible communications. The audio
signal travels from the microphone to the electrical equipment through
another conductive wire. SUMMARY OF THE INVENTION An electrical
coupling such as conductive wires, however, may introduce interference
that degrades the audio signals. External radio-frequency (“RFâ€?
sources may induce interference into an electrical coupling. For
example, in an aircraft cockpit, whether civilian or military,
external RF sources may induce currents in the lengthy sheathing of
the conductive wires from the electrical equipment to the pilot's
headset. The induced currents degrade the audio signals going to the
headset or interfere with front-end electronics on the equipment side.
Also, because the microphone in the pilot's headset is a piezoelectric
or ribbon microphone whose small voltage or current is not amplified
before it goes through the conductive wires to the equipment, the
external RF source may induce voltages or currents that overwhelm the
audio signal. Also, for devices such as portable radio receivers, the
conductive wires may act as extensions of the receiver's aerial. The
proximity of the conductive wires with the user may alter
characteristics of the aerial and degrade RF reception by the
receiver. Thus electrical coupling of the headset and/or the
microphone to the electrical equipment may impair the performance of
the electrical equipment and the transfer of the audible
communications. It is therefore desirable to provide an non-electrical
connection between the electronic equipment and the headset and/or
microphone that reduces induced currents and voltages due to external
radio-frequency sources. The non-electrical connection may improve
audible communications between the electronic equipment and the
headset and/or microphone. The non-electrical connection may also
prevent coupling with the aeria http://www.chinese-microphone.com/Headset-Microphones.html
l of electronic equipment operating at radio frequencies. One aspect
of the invention relates to an electro-optical headset. The electro-
optical headset includes an optical driver for receiving a first
electrical signal representative of audio and for producing a
modulated light signal based on the first electrical signal. The
electro-optical headset also includes an optical link having a first
end and a second end. The first end is coupled to the optical driver
for receiving the modulated light signal. The electro-optical headset
further includes an optical receiver coupled to the second end of the
optical link for receiving the modulated light signal and demodulating
the modulated light signal to produce a second electrical signal
representative of the audio. The electro-optical headset yet further
includes a headset speaker element electrically connected with the
optical receiver for receiving the second electrical signal and
producing sound waves based on the second electrical signal. Another
aspect of the invention relates to an electro-optical microphone. The
electro-optical microphone includes an optical transceiver for
producing a source light and for receiving a modulated light signal,
and for producing a first electrical signal representative of audio
based on the modulated light signal. The electro-optical microphone
also includes an optical link having a first end and a second end. The
first end is coupled to the optical transceiver for receiving the
source light and for transmitting the modulated light signal. The
electro-optical microphone further includes a microphone element
coupled to the second end of the optical link for receiving the source
light and modulating the source light to produce the modulated light
signal representative of the audio. The microphone element is coupled
to the second end of the optical link for transmitting the modulated
light signal. Yet a further aspect of the present invention relates to
a method for reproducing audio in an electro-optical headset. The
method includes receiving a first electrical signal representative of
the audio and producing a modulated light signal based on the first
electrical signal. The method also includes transporting the modulated
light signal through an optical link to an optical receiver and
demodulating the modulated light signal in the optical receiver to
produce a second electrical signal representative of the audio. The
method further includes reproducing the audio in a headset speaker
element by applying the second electrical signal to the headset
speaker element. Another aspect of the present invention relates to a
method for receiving audio from an electro-optical microphone. The
method includes producing a source light in an optical transceiver and
transporting the source light through an optical link from the optical
transceiver to a microphone element. The method also includes
modulating the source light in the microphone element to produce a
modulated light signal representative of the audio and transporting
the modulated light signal through the optical link from the
microphone element to the optical transceiver. The method further
includes demodulating the modulated light signal in the optical
transceiver to produce a first electrical signal representative of the
audio. The foregoing and other features and advantages of preferred
embodiments of the present invention will be more readily apparent
from the following detailed description, which proceeds with
references to the accompanying drawings. BRIEF DESCRIPTION OF THE
DRAWINGS Preferred embodiments of the present invention are described
with reference to the following drawings, wherein: FIG. 1 is a block
diagram illustrating components of an electrical coupling between
electronic equipment and a headset and/or microphone; FIG. 2 is a
block diagram illustrating a preferred electro-optical headset
apparatus and a preferred electro-optical microphone apparatus; FIG. 3
is a block diagram illustrating a preferred embodiment of the electro-
optical headset apparatus of FIG. 2; FIG. 4 is a block diagram
illustrating preferred embodiments of the electro-optical headset
apparatus of FIG. 2; FIG. 5 is a block diagram illustrating a
preferred embodiment of the electro-optical microphone apparatus of
FIG. 2; FIG. 6 is a block diagram illustrating a preferred embodiment
of a microphone element in the electro-optical microphone apparatus of
FIG. 2; FIG. 7 is a block diagram illustrating another preferred
embodiment of the microphone element in the electro-optical microphone
apparatus of FIG. 2; FIG. 8 is a block diagram illustrating a
preferred embodiment of an electro-optical headset; FIG. 9 is a block
diagram illustrating preferred embodiments of an optical receiver and
a microphone element in the electro-optical headset of FIG. 8; and
FIG. 10 is a block diagram illustrating a preferred embodiment of an
electro-optical interface in the electro-optical headset of FIG. 8.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 is a block
diagram illustrating components of an electrical coupling 10 between
electronic equipment 12 and a headset 14 and/or microphone 16 , 18 .
In an integrated configuration, the microphone 16 may suspend from the
headset 14 by a boom 20 . A user 22 places the headset on his head,
locating the headset 14 proximate to or within his ear, and locating
the microphone 16 proximate to his mouth. Alternatively, a mounting 24
along the electrical coupling 10 may have an integrated microphone
18 . The mounting 24 hangs from the headset 14 such that the
integrated microphone 18 is level with the mouth of the user 22 . It
should be understood, however, that the configuration and relationship
of the headset 14 and microphones 16 , 18 of FIG. 1 are for
illustrative purposes. Other configurations are possible, such as a
hand-held microphone, a lapel microphone, or integrated earpieces in a
flight helmet. In general, the microphone 16 , 18 may be wearable on
clothing or accessories such as spectacles, integrated into wearable
headgear, or mechanically connected to the headset 14 . The electrical
coupling 10 is typically shielded cable whose core includes a wire for
conducting audio signals from the electronic equipment 12 to the
headset 14 , another wire for conducting audio signals from the
microphone 16 , 18 to the electronic equipment 12 , and independent or
common sheathing that acts as a return conductive path, also known to
those of ordinary skill in the art as a “groundâ€?path, for either or
both the headset 14 and/or the microphone 16 , 18 . External RF
sources, however, may induce currents in the sheathing of the
electrical coupling 10 that degrade the audio signals or interfere
with front-end electronics in the electronic equipment 12 .
Additionally, the sheathing of the electrical coupling 10 may act as
an aerial when connected to electronic equipment 12 operating at radio
frequencies and interfere with RF transmission from an aerial 26
attached to the electronic equipment 12 . The problems with the
electrical coupling 10 may be overcome by optically coupling the
headset and/or microphone to the electronic equipment 12 . FIG. 2 is a
block diagram illustrating a preferred electro-optical apparatus for
transferring audio from electronic equipment 12 to a headset speaker
element 30 , herein termed an “electro-optical headset,â€?and a
preferred electro-optical apparatus for transferring audio from a
microphone 36 to the electronic equipment 12 , herein termed an “e
lectro-optical microphone.�The electro-optical headset transports
modulated light that is representative of the audio from the
electronic equipment 12 , through an optical link 32 , to an optical
receiver 42 . Similarly, the electro-optical microphone transports
modulated light that is representative of the audio from the
microphone 36 , through another optical link 38 , to the electronic
equipment 12 . The optical links 32 , 38 may improve audible
communications between the electronic equipment 12 and the headset
speaker element 30 and/or microphone 36 , and may also prevent
coupling with the aerial of electronic equipment 12 operating at radio
frequencies. It should be understood, however, that the configuration
and relationship of the headset speaker element 30 and microphone 36
shown in FIG. 2 are for illustrative purposes. Other configurations
are possible, such as a hand-held microphone, a lapel microphone, or a
headset integrated into a flight helmet. In general, the microphone 36
may be wearable on clothing or accessories, such as spectacles. The
microphone 36 may also be integrated into wearable headgear, or
mechanically connected to the headset speaker element 30 , and the
present invention is not limited to the preferred embodiments
described herein and illustrated in FIG. 2. Electro-Optical Headset
The electro-optical headset apparatus 30 �34 , 42 includes an optical
driver 34 for receiving a first electrical signal representative of
audio and for producing a modulated light signal based on the first
electrical signal. The electro-optical headset 30 �34 , 42 also
includes an optical link 32 that is coupled to the optical driver 34
for receiving the modulated light signal. An optical receiver 42 in
the apparatus receives the modulated light signal from the optical
link 32 and demodulates the modulated light signal to produce a second
electrical signal representative of the audio. The apparatus also
includes a headset speaker element 30 that is electrically connected
with the optical receiver 42 and that receives the second electrical
signal to produce sound waves based on the second electrical signal.
FIG. 3 is a block diagram illustrating a preferred embodiment of the
electro-optical headset 30 �34 , 42 of FIG. 2. The optical driver 34
receives electrical signals from the electronic equipment 12 . The
optical driver 34 may electrically couple to the electronic equipment
12 by an electrical audio connector 50 that inserts into a
corresponding connector in the electrical equipment 12 . For example,
the electrical audio connector 50 may be an audio jack plug, familiar
to those of ordinary skill in the art, that inserts into a
corresponding socket in the electronic equipment 12 . The audio signal
to be transferred to the optical receiver 42 and headset speaker
element exits in the form of the first electrical signal from the
electronic equipment 12 through the connector 50 and modulates a light
source 54 , such as a light emitting diode (“LEDâ€? 54 . In a preferred
embodiment, the light source 54 is a coherent light or laser LED. The
first electrical signal from the electronic equipment 12 modulates the
light source 54 , for example by a modulation circuit 52 . The
modulation circuit 52 may vary the light source 54 in response to the
first electrical signal under a variety of modulation schemes. For
example, as illustrated in FIG. 3, the modulation circuit 52 may vary
the intensity of the light source 54 in response to the first
electrical signal, a process commonly referred to as amplitude
modulation by those of ordinary skill in the art. In another example,
the modulation circuit 52 may vary the frequency of pulses from the
light source 54 in response to the first electrical signal, a process
commonly referred to as frequency modulation by those of ordinary
skill in the art. In yet another example, the modulation circuit 52
may vary the duration of pulses from the light source 54 in response
to the first electrical signal, a process commonly referred to as
pulse width modulation by those of ordinary skill in the art. In a
preferred embodiment, the light source 54 is a laser LED whose
luminance varies in response to the first electrical signal according
to a pulse width modulation scheme. The modulation circuit 52 may also
amplify the first electrical signal before modulation or match
impedance between the electrical equipment 12 and the light source
54 . It should be understood, however, that the preferred embodiments
are not limited to the circuit elements illustrated in FIG. 3 and that
other circuit elements are possible. For example, the light source 54
may be an infra-red, visible light, or laser LED. Alternatively, the
light source 54 may be an incandescent, fluorescent, or bioluminescent
light source. Additionally, the modulator circuit 52 may include an
operational amplifier, transistor, or other active circuit element or
elements that may amplify or match impedance as is familiar to those
of ordinary skill in the art. The output from the light source 54
enters one end of the optical link 32 where it is transported to the
other end of the optical link 32 . In a preferred embodiment, the
optical link 32 is an optical fiber or an optical pipe. Optical fibers
are typically composed of silica or other glassy material that guide
light from one end to the other without significant attenuation in the
intensity of the light. Optical pipes, on the other hand, are
typically composed of plastic material that similarly guide light from
one end to the other. Both types of optical link 32 transmit light
without significant attenuation under a wide range of mechanical
bending that deviates from a straight line. In this manner, the
optical link 32 transports light from the position of the optical
driver 34 at the electronic equipment 12 to the position of the
headset 30 substantially regardless of the physical shape of the
optical link 32 . Also, due to the dielectric material of which it is
constructed, the optical link 32 does not conduct electricity, is
immune to RF interference, and can operate in RF-noisy environments,
such as the cockpit of an airplane, without degrading the quality of
the audio signal. Additionally, in the proximity to electronic
equipment 12 with an aerial 26 that operates at radio frequencies, the
optical link 32 does not provide any conducting paths that may
interact with the aerial 26 and may alter the RF characteristics of
the aerial 26 . In a preferred embodiment, the optical receiver 42 is
a photo-voltaic cell 56 that produces a voltage in response to the
intensity of light that the photo-voltaic cell 56 receives. The photo-
voltaic cell 56 receives modulated light from the other end of the
optical link 32 and produces a voltage at its terminals. The photo-
voltaic cell 56 connects to the headset speaker element 30 that vib

rates in response to the voltage of the photo-voltaic cell 56 . In a
preferred embodiment, the headset speaker element 30 is a
piezoelectric headset speaker element 58 . The voltage across the
terminals of the photo-voltaic cell 56 represents a preferred
embodiment of the second electrical signal, which causes the
piezoelectric headset speaker element 58 to vibrate and produce sound
waves. The sound waves correlate with the audio received by the
optical driver 34 from the electronic equipment 12 , and reproduce the
audio in the ear of the user 22 . In an alternative preferred
embodiment, the headset speaker element 30 is an electromagnetic
headset speaker element (not shown). The voltage across the terminals
of the photo-voltaic cell 56 produces a current that flows through the
electromagnetic headset speaker element. The current represents
another preferred embodiment of the second electrical signal that
causes the electromagnetic headset speaker element to vibrate and
produce the sound waves. In another preferred embodiment, the optical
receiver 42 includes demodulation circuitry. FIG. 4A is a block
diagram illustrating an alternative preferred embodiment of the
optical receiver 42 and headset speaker element 30 . The modulated
light signal from the optical link 32 illuminates a photo-detector 72
in the optical receiver 42 . The photo-detector 72 may be a
photodiode, photo-voltaic cell 56 , or other semiconductor device that
is responsive to light, for example a phototransistor. A third
electrical signal that is present across the photo-detector 72
corresponds to the modulated light signal received from the optical
link 32 . The demodulator circuit 70 converts the third electrical
signal across the photo-detector 72 into the second electrical signal
that is representative of the original audio received by the optical
driver 34 from the electronic equipment 12 . The demodulator circuit
70 may also amplify the third electrical signal. The headset speaker
element 30 receives the second electrical signal and reproduces the
audio in the user's 22 ear. In this preferred embodiment, the headset
speaker element 30 may be a piezoelectric headset speaker element 58
or an electromagnetic headset speaker element (not shown) and the
optical receiver 30 may include one or more batteries (not shown) to
provide power to the amplifier circuit 70 . In another alternative
preferred embodiment, the optical receiver 42 includes demodulation
circuitry 70 that is powered by a photo-voltaic cell 56 . FIG. 4B is a
block diagram illustrating the alternative preferred embodiment of the
optical receiver 42 and headset speaker element 30 . The photo-voltaic
cell 56 receives the modulated light signal from the optical driver 34
through the optical link 32 . The modulated light signal represents
the audio and produces the third electrical signal across the photo-
voltaic cell 56 . A capacitor 76 or similar device separates the
alternating current (“ACâ€? component of the third electrical signal
from a direct current (“DCâ€? voltage of the photo-voltaic cell 56 .
The demodulator circuit 70 converts the AC electrical signal into the
second electrical signal that is representative of the original audio
received by the optical driver 34 from the electronic equipment 12 .
The demodulator circuit 70 may also amplify the third electrical
signal. The piezoelectric speaker element 58 or electromagnetic
speaker element receives the second electrical signal and reproduces
the audio from the electronic equipment 12 in the user's 22 ear.
Additionally, a regulator circuit 78 regulates the DC voltage across
the photo-voltaic cell 56 to provide a substantially constant DC
voltage that powers the demodulator circuit 70 . In order to power the
optical receiver 42 in this manner, the light source 54 in the optical
driver 34 sends sufficient light through the optical link 32 to
maintain an operable DC voltage across the photo-voltaic cell 56 . To
power the embodiment of FIG. 4B, the light source 54 of FIG. 3 is
preferably a laser LED that produces a quiescent light intensity when
the optical driver 34 receives no electrical signals from the
electronic equipment 12 . For example, in the embodiment of the
optical driver 34 of FIG. 3, the laser LED 54 is forward biased and
produces this quiescent light when the optical driver 34 receives no
electrical signals. The quiescent light powers the demodulator circuit
70 in the absence of a first electrical signal from the electronic
equipment 12 . When the first electrical signal from the electronic
equipment 12 arrives in the optical driver 34 , it modulates the light
from the laser LED 54 . In operation, the average intensity of the
modulated light is sufficient illumination of the photo-voltaic cell
56 to provide a DC voltage that powers the demodulator circuit 70
after regulation by the regulator circuit 78 . In the preferred
embodiments described above, the demodulation circuit 70 may include
one or more operational amplifiers, transistors, or other active
circuit element that are familiar to those of ordinary skill in the
art. The demodulator circuit 70 may also comprise discrete electronic
components, monolithic integrated circuits, or a combination of both.
Also, the regulator circuit 78 may be constructed according to methods
and components familiar to those of ordinary skill in the art. For
example, the regulator circuit 78 may comprise a capacitor and Zener
diode (not shown) or may comprise a monolithic integrated circuit that
produces a constant output voltage over a wide range of variable input
voltages. In operation, the electro-optical headset 30 �34 , 42 of
FIG. 2 to FIG. 4 receives a first http://www.chinese-microphone.com/Headset-Microphones.html
electrical signal representative of the audio and produces a modulated
light signal based on the first electrical signal. The electro-optical
headset 30 �34 , 42 transports the modulated light signal through the
optical link 32 to the optical receiver 42 . The electro-optical
headset 30 �34 , 42 demodulates the modulated light signal in the
optical receiver 42 to produce a second electrical signal
representative of the audio and reproduces the audio in a headset
speaker element 30 by applying the second electrical signal to the
headset speaker element 30 . Electro-Optical Microphone The electro-
optical microphone apparatus 36 �40 includes an optical transceiver
40 for producing a source light and for receiving a modulated light
signal. The optical transceiver 40 also produces a first electrical
signal representative of audio based on the modulated light signal.
The electro-optical microphone 36 �40 also includes an optical link
38 , one end of which is coupled to the optical transceiver 40 . The
end receives the source light from, and transmits the modulated light
signal to, the optical transceiver 40 . The electro-optical microphone
36 �40 also includes a microphone element 36 coupled to the other end
of the optical link 38 for receiving the source light and modulating
the source light to produce the modulated light signal representative
of the audio. The microphone element 36 is also coupled to the other
end of the optical link 38 for transmitting the modulated light
signal. FIG. 5 is a block diagram illustrating a preferred embodiment
of the electro-optical microphone 36 �40 of FIG. 2. The optical
transceiver 40 includes a light source 90 producing the source light
that the optical link 38 transports to the microphone element 36 . The
source light is modulated by the microphone element 36 to produce the
returned light. The optical link 38 also transports the returned
modulated light signal to the optical transceiver 40 where it is
received by an photo-detector 94 and demodulated by a demodulator
circuit 96 . The photo-detector 94 may be a phototransistor,
photodiode, or other semiconductor device whose electrical
characteristics vary with respect to illumination. The demodulator
circuit 96 may also produce the first electrical signal that is
representative of the audio. In addition, the electronic equipment 12
may receive the first electrical signal through an electrical audio
connector 50 , such as an audio jack plug, that inserts into a
corresponding socket in the electronic equipment 12 as is familiar to
those of ordinary skill in the art. In one preferred embodiment, the
microphone element 36 is a diaphragm 92 with a reflective surface.
Sound waves from the user's 22 mouth, representative of the audio,
cause the diaphragm 92 to vibrate. The reflective surface of the
diaphragm 92 reflects the source light from the optical link 38 in
different directions corresponding to the degree of deformation to
produce the modulated light signal. The optical link 38 accepts the
modulated light signal whose intensity varies with the degree of
deformation of the reflective diaphragm 92 i.e. the reflective
diaphragm 92 amplitude modulates the source light to produce the
modulated light signal. The optical transceiver 40 accepts the
returned light from the optical link 38 and demodulates the modulated
light signal to produce the first electrical signal that is
representative of the audio. FIG. 6 is a block diagram illustrating
another preferred embodiment 100 of the microphone element 36 . The
source light from the optical link 38 enters a directional optical
coupler 102 , which directs the source light through a first optical
path 104 . A diaphragm 106 has a translucent or semi-transparent wedge
108 attached to its back surface. Sound waves from the user's 22
mouth, representative of the audio, deform the diaphragm 106 . The
deformed diaphragm 106 interposes the wedge 108 between the first
optical path 104 and a second optical path 110 . As the wedge 108 is
further interposed between the optical paths, the wedge 108 further
attenuates the source light as it crosses from the first optical path
104 to the second optical path 110 because the source light has to
pass through more of the translucent or semi-transparent material of
which the wedge 108 is made. The degree of attenuation of the source
light is representative of the audio. In this manner, the light in the
second optical path 110 is amplitude modulated by the sound waves. The
directional optical coupler 102 accepts the modulated light signal
from the second optical path 110 and directs the modulated light
signal to the optical link 38 where it is transported to the optical
transceiver 40 for conversion to the first electrical signal that is
representative of the audio. The wedge 108 may be constructed of
plastic or other material that is translucent or semi-transparent. The
wedge 108 may have a trapezoidal cross section in the plane of the
optical paths 104 , 110 , or the cross section of the wedge 108 may be
shaped to compensate for a non-linear response of the diaphragm 106
and wedge 108 to the sound waves. The first optical path 104 between
the directional optical coupler 102 and the wedge 108 and/or the
second optical path 110 between the wedge 108 and the directional
optical coupler 102 may be defined by reflection off mirrors (not
shown) or by a refractive medium. The refractive medium may be a prism
or other dielectric device that alters light propagating through it,
or the refractive medium may be an optical fiber or optical pipe of
the same or different material as the optical link 38 . It should be
understood, however, that the optical paths 104 , 110 need not be
defined wholly or partially within solid refractive media but may be
defined in vacuum, liquid, or gaseous media, such as air. FIG. 7 is a
block diagram illustrating another preferred embodiment 120 of the
microphone element 36 . The source light from the optical link 38
enters the directional optical coupler 102 , which directs the source
light through the first optical path 104 . An electrical microphone
122 , such as a piezoelectric microphone, generates a voltage that
modulates the opacity of an electro-optical shutter 124 . The opacity
of the electro-optical shutter 124 varies in response to the voltage
across the electro-optical shutter 124 . As sound waves from the
user's 22 mouth cause a second electrical signal across the electrical
microphone 122 that is representative of the audio, the second
electric signal varies the opacity of the electro-optical shutter 124
and correspondingly attenuates the source light. The degree of
attenuation of the source light is representative of the audio. In
this manner, the light in the second optical path 110 is amplitude
modulated by the second electrical signal. The directional optical
coupler 102 accepts the modulated light signal from the second optical
path 110 and directs the modulated light signal to the optical link 38
where it is transported to the optical transceiver 40 for conversion
to the first electrical signal that is representative of the audio. In
a preferred embodiment, the electro-optical shutter 124 is a liquid
crystal display (“LCDâ€? element familiar to those of ordinary skill in
the art. The electrical microphone 122 may require resistor and/or
capacitor circuit elements (not shown) in series and/or in parallel to
match the response characteristics of the LCD element. The resistor
and/or capacitor circuit elements may also be required to permit the
discharge of any capacitor effect that the LCD element may have, as is
known to those of ordinary skill in the art. It should be understood,
however, that the preferred embodiments are not limited to the
optical, electrical, and/or mechanical elements illustrated in FIG. 5
to FIG. 7 and that other elements are possible. For example, the light
source 90 may be an infra-red, visible light, or laser/coherent light
LED. Alternatively, the light source 90 may be an incandescent,
fluorescent, or bioluminescent light source. The demodulator circuit
96 may include an operational amplifier, transistor, or other active
circuit element or elements that may amplify or match impedance as is
familiar to those of ordinary skill in the art. Additionally, the
optical link 38 may comprise two or more optical pipes or optical
fibers. One of the two optical pipes of fibers transports the source
light from the light source 90 to the microphone element 36 ,
regardless of whether the microphone element 36 contains the diaphragm
92 of FIG. 5, the wedge 108 of FIG. 6, or the electro-optical shutter
124 of FIG. 7. The other optical pipe or fiber transports the
modulated light signal from these optical modulators 92 , 108 , 124 to
the optical transceiver 40 . In such a configuration with two optical
pipes of fibers, the microphone element 36 need not include the
directional optical coupler 102 , and the first 104 and second 110
optical paths may each comprise the optical pipe or optical fiber
coming from or returning to the optical transceiver 40 . Further,
reflective microphone elements 36 are not limited to the diaphragms
with reflective back surfaces 92 of FIG. 5 or the diaphragm 106 with
the translucent or semi-transparent wedge 108 of FIG. 6. Other
embodiments of the microphone element 36 are possible, such a Bragg
grating, familiar to those of ordinary skill in the art, attached to a
diaphragm that modulates the source light to produce the modulated
light signal. Another embodiment of the microphone element 36 is a
Bragg grating or Surface Acoustic Wave device that is electro-
mechanically vibrated by an amplified voltage from a piezoelectric or
electromagnetic microphone. In a preferred embodiment, the directional
optical coupler 102 of FIG. 6 and FIG. 7 is a bifurcated optical
fiber, familiar to those of ordinary skill in the art, with one bi-
directional input for attaching to the optical link 38 , a
unidirectional input for receiving the modulated light signal from the
optical modulators 92 , 108 , 124 , and a uni-directional output for
transmitting the source light to the optical modulators 92 , 108 ,
124 . In alternative preferred embodiments, the directional optical
coupler 102 is a prismatic optical device or a half-silvered mirror
optical device for outputting the source light from the optical link
38 and inputting the modulated light signal to the optical link 38 .
It should be understood, however, that the directional optical coupler
102 of the present invention is not limited to these embodiments and
that other embodiments of the directional optical coupler 102 are
possible, such as dielectric, dichromatic, or polarization directional
optical devices. In operation, the electro-optical microphone 36 �40
of FIGS. 5� produces a source light in an optical transceiver 40 and
transports the source light through an optical link 38 from the
optical transceiver 40 to a microphone element 36 . The electro-
optical microphone 36 �40 modulates the source light in the
microphone element 36 to produce a modulated light signal
representative of the audio and transports the modulated light signal
through the optical link 38 from the microphone element 36 to the
optical transceiver 40 . The electro-optical microphone 36 �40
demodulates the modulated light signal in the optical tr

ansceiver 40 to produce a first electrical signal representative of
the audio. Electro-Optical Headset The electro-optical headset 30 �
34 , 42 and electro-optical microphone 36 �40 are presented in FIG. 2
as having separate optical links 32 , 38 . A single optical link may
transport audio in the form of light signals both to and from the
headset. FIG. 8 is a block diagram illustrating a preferred embodiment
of an electro-optical headset 130 . The electro-optical headset 130
includes an electro-optical interface 132 for receiving a first
electrical signal representative of first audio and for producing a
first modulated light signal based on the first electrical signal. The
electro-optical interface 132 is also for receiving a second modulated
light signal and demodulating the second modulated light signal to
produce a second electrical signal representative of second audio. The
electro-optical headset 130 also includes an optical link 134 having a
first end and a second end. The first end is coupled to the electro-
optical interface 132 for receiving the first modulated light signal
and for transmitting the second modulated light signal. Also included
in the electro-optical headset 130 is an optical receiver 136 ,
coupled to the second end of the optical link 134 , for receiving the
first modulated light signal and for demodulating the first modulated
light signal to produce a third electrical signal representative of
the first audio. The electro-optical headset 130 further includes a
headset speaker element 138 electrically connected with the optical
receiver for receiving the third electrical signal and producing first
sound waves based on the third electrical signal. Additionally, the
electro-optical headset 130 includes a microphone element 140 coupled
to the second end of the optical link 134 for receiving the first
modulated light signal and for transmitting the second modulated light
signal. The microphone element 140 is also for modulating the first
modulated light signal to produce the second modulated light signal
representative of the second audio. The electro-optical headset 130
may also electrically connect to the electronic equipment 12 through
at least one electrical audio connector. The first audio, to be heard
by the user 22 in the speaker element 138 , passes through one
electrical audio connector in the form of the first electrical signal
from the electronic equipment 12 to the electro-optical interface
132 . As is familiar to thos http://www.chinese-microphone.com/Headset-Microphones.html
e of ordinary skill in the art, the electronic equipment 12 , such as
a mobile station, e.g. a walkie-talkie or a cellular telephone, may
have an audio jack socket for connecting to an earpiece or headset and
providing the first audio received (“Rxâ€? by the electronic equipment
12 to the electro-optical headset 130 . The electronic equipment 12 ,
such as the mobile station, may also have another audio jack socket
for connecting to an external microphone, for example the integrated
microphone 18 in the mounting 24 of FIG. 1. The other audio jack
socket receives the second audio from the electro-optical headset 130
to be transmitted (“Txâ€? by the walkie-talkie of cellular telephone.
The electro-optical headset 130 connects to the audio jack sockets by
corresponding audio jack plugs. Alternatively, both audio jack sockets
may be combined into a dual audio jack socket, familiar to those of
ordinary skill in the art, and the electro-optical headset 130 has a
dual audio jack plug for connecting to the electronic equipment 12 .
FIG. 9 is a block diagram illustrating preferred embodiments of the
optical receiver 136 and the microphone element 140 in the electro-
optical headset 130 of FIG. 8. In a preferred embodiment, the optical
receiver 136 is a photo-voltaic cell 142 that produces a voltage in
response to the intensity of the first modulated light signal that the
photo-voltaic cell 142 receives. The photo-voltaic cell 56 receives
the first modulated light signal from the second end of the optical
link 134 and produces a voltage at its terminals. The photo-voltaic
cell 142 connects to the headset speaker element 138 that vibrates in
response to the voltage of the photo-voltaic cell 142 . In a preferred
embodiment, the headset speaker element 138 is piezoelectric. The
voltage across the terminals of the photo-voltaic cell 142 represents
the third electrical signal that causes the piezoelectric headset
speaker element 138 to vibrate and produce the first sound waves. The
first sound waves correlate with the first audio received by the
electro-optical interface 132 from the electronic equipment 12 , and
reproduce the first audio in the ear of the user 22 . In an
alternative preferred embodiment, the headset speaker element 138 is
electromagnetic. The voltage across the terminals of the photo-voltaic
cell 142 produces a current that flows through the electromagnetic
headset speaker element 138 . The current represents the third
electrical signal that causes the electromagnetic headset speaker
element 58 to vibrate and produce the first sound waves. A preferred
embodiment of the microphone element 140 includes an electrical
microphone 144 , an electro-optical shutter 146 and a directional
optical coupler 148 . The first modulated light signal from the
optical link 134 enters the directional optical coupler 148 , which
directs the first modulated light signal through an input optical path
150 to the electro-optical shutter 146 . The electrical microphone
144 , such as a piezoelectric microphone, generates a voltage that
modulates the opacity of the electro-optical shutter 146 . The opacity
of the electro-optical shutter 146 varies in response to the voltage
across the electro-optical shutter 146 . As the second sound waves
from the user's 22 mouth cause a fourth electrical signal across the
electrical microphone 144 that is representative of the second audio,
the fourth electric signal varies the opacity of the electro-optical
shutter 146 and correspondingly attenuates the first modulated light
signal. The degree of attenuation of the first modulated light signal
is representative of the second audio. In this manner, the light in an
output optical path 152 is amplitude modulated by the fourth
electrical signal. The directional optical coupler 148 accepts the
second modulated light signal from the output optical path 152 and
directs the second modulated light signal to the optical link 134
where it is transported to the electro-optical interface 132 for
conversion to the second electrical signal that is representative of
the second audio. In a preferred embodiment, the electro-optical
shutter 146 is a LCD element. The electrical microphone 144 may
require resistor and/or capacitor circuit elements (not shown) in
series and/or in parallel to match the response characteristics of the
LCD element. The resistor and/or capacitor circuit elements may also
be required to permit the discharge of any capacitor effect that the
LCD element may have, as is known to those of ordinary skill in the
art. In another preferred embodiment, the electro-optical headset 130
includes an optical splitter 154 as illustrated in FIG. 9. Instead of
directing the first modulated light signal along the input optical
path 150 to the electro-optical shutter 146 of the microphone element
140 , the directional optical coupler 148 directs the first modulated
light signal to the optical splitter 154 along an alternative input
optical path 156 . The optical splitter 154 receives the first
modulated light signal from the directional optical coupler 148 along
the alternative input optical path 156 , and directs the first
modulated light signal along a first optical path 158 to the optical
receiver 136 and along a second optical path 160 to the microphone
element 140 . In this manner, the optical splitter 154 provides the
first modulated light signal to the optical receiver 136 for
reproduction of the first audio, and provides the first modulated
light signal to the microphone element 140 for further modulation by
the second audio. In a preferred embodiment, the optical splitter 154
is a bifurcated optical fiber, familiar to those of ordinary skill in
the art, with one input for receiving the first modulated light signal
from the directional optical coupler 148 , and two outputs for
transmitting the first modulated light signal to the microphone
element 140 and the optical receiver 136 . In alternative preferred
embodiments, the optical splitter 154 is a prismatic optical device or
a half-silvered mirror optical device. It should be understood,
however, that the optical splitter 154 of the present invention is not
limited to these embodiments and that other embodiments of the optical
splitter 154 are possible, such as dielectric, dichromatic, or
polarization optical devices. FIG. 10 is a block diagram illustrating
a preferred embodiment of the electro-optical interface 132 in the
electro-optical headset 130 of FIG. 8. The electro-optical interface
132 includes a pulse width modulation circuit 176 and a sample-and-
hold circuit 188 . Also included in the electro-optical interface 132
is a pulse train oscillator circuit 180 for synchronizing the
beginning of each pulse of the first modulated light signal, and for
controlling the sampling of the sample-and-hold circuit 188 to
demodulate the second modulated light signal to provide the second
electrical signal. In operation, the pulse train oscillator circuit
180 triggers the pulse width modulation circuit 176 to provide an
electrical pulse whose duration is proportional to the amplitude of
the first electrical signal received from the electrical equipment
12 , which is representative of Rx, the first audio received from the
electrical equipment 12 . For example, the pulse width modulation
circuit 176 may include a one-shot multivibrator circuit, familiar to
those of ordinary skill in the art. The electrical pulse from the
pulse width modulation circuit 176 drives a laser LED 182 to produce
the first modulated light signal. In a preferred embodiment, the pulse
train oscillator circuit 180 provides triggering pulses at a frequency
of far above audio frequencies, such as at 40 kiloHertz (“kHzâ€?.. The
laser LED 182 transmits the light pulses of the first modulated light
signal to a directional optical coupler 168 through a receiving
optical path 170 . The intensity of the first modulated light signal
varies in proportion to the first electrical signal because each light
pulse from the laser LED 182 is longer in duration in proportion to
the first electrical signal. The directional optical coupler 168
receives the first modulated light signal and directs it to the first
end of the optical link 132 through a two-way optical path 174 . At
the second end of the optical link 132 , the optical receiver 136 ,
such as the photo-voltaic cell 142 of FIG. 9, responds to the
intensity of the first modulated light signal by providing the third
electrical signal, which is approximately proportional to the
intensity of the first modulated light signal. Due to the response of
the photo-voltaic cell 142 to light pulses at a rate above audio
frequencies, the third electrical signal is substantially similar to
the first electrical signal. The directional optical coupler 168
receives the second modulated light signal from the optical link 134
through the two-way optical path 174 . The directional optical coupler
168 directs the second modulated light signal through a transmitting
optical path 172 to a photo-detector 184 whose electrical properties
change in proportion to the intensity of incident light. In a
preferred embodiment, the photo-detector 184 is a semiconductor
device, such as a photodiode or a phototransistor. The electro-optical
interface 132 may include an amplifier circuit 186 for amplifying the
electrical signal across the semiconductor device 184 before
processing by the sample-and-hold circuit 188 . As is known to those
of ordinary skill in the art, the output of the sample-and-hold
circuit 188 responds to the amplitude modulated characteristics of the
second modulated light signal and does not respond to the pulse width
modulated characteristics of the second modulated light signal. The
pulses of light of the second modulated light signal synchronize with
the pulses from the pulse train oscillator circuit 180 . The amplitude
of each pulse, however, is proportional to the amplitude of the fourth
electrical signal in the microphone element 140 of FIG. 9. Each
triggering pulse from the pulse train oscillator circuit 180 causes
the sample-and-hold circuit 188 to sample the output voltage of the
amplifier circuit 186 . Between triggering pulses, a holding capacitor
190 holds the output of the sample-and-hold circuit 188 at the last
sampled output voltage of the amplifier. In this manner, the output of
the sample-and-hold circuit 188 , the second electrical signal, is
proportional to the amplitude of the second modulated light signal,
which in turn is proportional to the fourth electrical signal from the
electrical microphone 144 of FIG. 9. In a preferred embodiment, the
directional optical coupler 148 of FIG. 9 and the directional optical
coupler 168 of FIG. 10 are bifurcated optical fibers, familiar to
those of ordinary skill in the art, each with one bi-directional input
for attaching to the optical link 134 . The directional optical
coupler 148 of FIG. 9 has a uni-directional input for receiving the
second modulated light signal from the electro-optical shutter 146 ,
and a uni-directional output for transmitting the first modulated
light signal to the electro-optical shutter 146 or the optical
splitter 154 . The directional optical coupler 168 of FIG. 10 has a
uni-directional input for receiving the first modulated light signal
from the electro-optical interface 132 , and a uni-directional output
for transmitting the second modulated light signal to the
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