U.S. patent application number 10/435157 was filed with the patent office on 2003-11-06 for high speed data link and transmitter in the mid-infrared wavelength range.
Invention is credited to Puzey, Kenneth A..
Application Number | 20030206691 10/435157 |
Document ID | / |
Family ID | 32034261 |
Filed Date | 2003-11-06 |
United States Patent
Application |
20030206691 |
Kind Code |
A1 |
Puzey, Kenneth A. |
November 6, 2003 |
High speed data link and transmitter in the mid-infrared wavelength
range
Abstract
A mid-infrared transmitter for providing a light signal in a
free-space communication system includes an arrangement for
producing electromagnetic radiation having a certain wavelength in
a mid-infrared wavelength range. The mid-infrared transmitter
further includes an arrangement for modulating the electromagnetic
radiation so as to provide a train of light pulses having the
certain wavelength as the light signal.
Inventors: |
Puzey, Kenneth A.; (Essex
Junction, VT) |
Correspondence
Address: |
BOULDER PATENT SERVICE INC
1021 GAPTER ROAD
BOULDER
CO
803032924
|
Family ID: |
32034261 |
Appl. No.: |
10/435157 |
Filed: |
May 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10435157 |
May 10, 2003 |
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09815972 |
Mar 22, 2001 |
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6584245 |
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09815972 |
Mar 22, 2001 |
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09637098 |
Aug 10, 2000 |
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6285487 |
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09637098 |
Aug 10, 2000 |
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09208326 |
Dec 9, 1998 |
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6115170 |
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09208326 |
Dec 9, 1998 |
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08643642 |
May 6, 1996 |
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5768002 |
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Current U.S.
Class: |
385/24 |
Current CPC
Class: |
H04J 14/0227 20130101;
H01L 39/16 20130101; H04B 10/508 20130101; G02F 2203/54 20130101;
G02F 1/0147 20130101; H04B 10/505 20130101; H04J 14/0282 20130101;
G02F 2202/16 20130101; G02F 2203/585 20130101 |
Class at
Publication: |
385/24 |
International
Class: |
G02B 006/28 |
Claims
What is claimed is:
1. A mid-infrared transmitter for providing a light signal in a
free-space communication system, said transmitter comprising: means
for producing electromagnetic radiation, said electromagnetic
radiation having a certain wavelength in a mid-infrared wavelength
range; and means for modulating said electromagnetic radiation so
as to provide a train of light pulses having said certain
wavelength as said light signal.
2. The mid-infrared transmitter of claim 1 wherein said
electromagnetic radiation producing means includes a laser
diode.
3. The mid-infrared transmitter of claim 2 wherein said laser diode
is a quantum cascade laser.
4. The mid-infrared transmitter of claim 2 wherein said laser diode
is a germanium laser.
5. The mid-infrared transmitter of claim 2 wherein said laser diode
is an antimonide laser.
6. The mid-infrared transmitter of claim 1 wherein said
mid-infrared wavelength range includes wavelengths between 3 and 5
microns.
7. The mid-infrared transmitter of claim 1 wherein said
mid-infrared wavelength range includes wavelengths between 8 and 12
microns.
8. The mid-infrared transmitter of claim 1 wherein said modulating
means is configured to modulate said electromagnetic radiation
after said electromagnetic radiation has been produced by said
electromagnetic radiation producing means so as to produce said
train of light pulses.
9. The mid-infrared transmitter of claim 1 wherein said
electromagnetic radiation producing means is configured to accept
an electrical signal, and wherein said modulating means includes
means for providing said electrical signal so as to provide said
train of light pulses.
10. The mid-infrared transmitter of claim 9 wherein said input
signal is a driving voltage, and wherein said modulating means is
configured to modulate said driving voltage and to supply said
driving voltage, so modulated, to said electromagnetic radiation
producing means so as to provide said train of light pulses.
11. The mid-infrared transmitter of claim 9 wherein said input
signal is a driving current, and wherein said modulating means id
configured to modulate said driving current and to supply said
driving current, so modulated, to said electromagnetic radiation
producing means so as to provide said train of light pulses.
12. The mid-infrared transmitter of claim 1 wherein said
electromagnetic radiation producing means is tunable such that said
certain wavelength of said electromagnetic radiation is
consequently tunable over a range of wavelengths within said
mid-infrared wavelength range.
13. The mid-infrared transmitter of claim 1 further comprising: a
plurality of additional means for producing a plurality of
additional electromagnetic radiation, each of said plurality of
additional electromagnetic radiation having a distinct wavelength
in said mid-infrared wavelength range; and a plurality of
additional means, each cooperating with at least one of said
additional electromagnetic radiation producing means, for providing
a plurality of trains of light pulses as said light signal, each of
said plurality of trains of light pulses having said distinct
wavelength.
14. The mid-infrared transmitter of claim 1 further comprising
means for directing said train of light pulses toward a particular
location.
15. The mid-infrared transmitter of claim 14 wherein said directing
means is adjustable to compensate for possible distortion in said
light pulses, said distortion potentially being produced during
transmission of the light pulses toward said particular
location.
16. The mid-infrared transmitter of claim 15 wherein said directing
means includes a conformable mirror.
17. A mid-infrared free space data link comprising: a transmitter
arrangement producing a transmitter output, said transmitting
arrangement including a source of light having a certain wavelength
in a mid-infrared wavelength range, a modulator arrangement for
modulating said light so as to provide a train of light pulses
having said certain wavelength as said transmitter output; a
directing arrangement for directing said transmitter output to a
particular location; and at said particular location, a receiving
arrangement configured for receiving said transmitter output.
18. The mid-infrared free space data link of claim 17 wherein said
directing arrangement includes a conformable mirror.
19. The mid-infrared free space data link of claim 17 wherein said
mid-infrared wavelength range includes wavelengths between 3 and 5
microns.
20. The mid-infrared free space data link of claim 17 wherein said
mid-infrared wavelength range includes wavelengths between 8 and 12
microns.
21. The mid-infrared free space data link of claim 17 wherein said
source includes a laser diode.
22. The mid-infrared free space data link of claim 21 wherein said
laser diode is a quantum cascade laser.
23. The mid-infrared free space data link of claim 21 wherein said
laser diode is a germanium laser.
24. The mid-infrared free space data link of claim 21 wherein said
laser diode is an antimonide laser.
25. The mid-infrared free space data link of claim 17 wherein said
modulator arrangement is configured to modulate said light after
said light has been produced by said source so as to produce said
train of light pulses.
26. The mid-infrared free space data link of claim 17 wherein said
source is configured to accept an input signal, and wherein said
modulator arrangement is configured to modulate said input signal
so as to provide said train of light pulses.
27. The mid-infrared free space data link of claim 26 wherein said
input signal is a driving voltage and wherein said modulator
arrangement is configured to modulate said driving voltage so as to
provide said train of light pulses.
28. The mid-infrared free space data link of claim 26 wherein said
input signal is an input current and wherein said modulator
arrangement is configured to modulate said input current so as to
provide said train of light pulses
29. The mid-infrared free space data link of claim 17 wherein said
source is tunable such that said certain wavelength of said light
is consequently tunable over a range of wavelengths within said
mid-infrared range.
30. The mid-infrared free space data link of claim 17 wherein said
receiver further includes a plurality of additional sources of
additional light, each of said plurality of additional light having
a distinct wavelength in said mid-infrared wavelength range; and a
plurality of additional arrangements, each cooperating with at
least one of said additional sources, for providing a plurality of
trains of light pulses as said transmitter output, each of said
plurality of trains of light pulses having said distinct
wavelength.
31. A method for providing a mid-infrared free space data link,
said method comprising: transmitting a signal containing data, said
transmitting step including generating light having a certain
wavelength in a mid-infrared wavelength range, modulating light so
as to provide a train of light pulses having said certain
wavelength as said signal; directing said signal toward a
particular location; and at said particular location, receiving
said signal.
32. The method of claim 31 wherein said directing step includes
adjusting said directing means to compensate for possible
distortion in said signal, said distortion being potentially
produced during transmission of said signal toward said particular
location.
33. The method of claim 31 wherein said adjusting step includes
using a conformable mirror.
34. A method for providing a mid-infrared free space data link for
communicating a data signal, said method comprising: providing an
input signal, generating, in response to said input signal, light
having a certain wavelength in a mid-infrared wavelength range,
wherein said step of providing said input signal includes
configuring said input signal so as to provide a train of light
pulses having said certain wavelength as said signal; directing
said data signal toward a particular location; and at said
particular location, receiving said signal.
35. The method of claim 34 wherein said step of providing said
input signal includes the step of supplying an input voltage as
said input signal.
36. The method of claim 34 wherein said step of providing said
input signal includes the step of supplying an input current as
said input signal.
Description
BACKGROUND OF THE INVENTION
[0001] The present application is a continuation of copending U.S.
patent application Ser. No. 09/815,972 filed Mar. 22, 2001, which
is a continuation-in-part of U.S. patent application Ser. No.
09/637,098 filed Aug. 10, 2000 and issued Sep. 4, 2001 as U.S. Pat.
No. 6,285,487, which is a continuation of U.S. patent application
Ser. No. 09/208,326 filed Dec. 9, 1998 and issued Dec. 5, 2000 as
U.S. Pat. No. 6,115,170, which is a continuation of U.S. patent
application Ser. No. 08/643,642 filed May 6, 1996 and issued Jun.
16, 1998 as U.S. Pat. No. 5,768,00. All of the aforementioned
patent applications and patents are incorporated herein by
reference in their entirety.
[0002] The present invention relates generally to fiber optic
communications and, more particularly, to high speed data links for
use with light modulation systems including a superconductive plate
assembly in a data transmission scheme.
[0003] The light modulation system as disclosed in U.S. Pat. No.
5,768,002 is capable of transmitting optical data signals at high
data rates such as, for example, rates of terabits per second
(Tbit/s) at a given wavelength over a single optical fiber. For
example, the light modulation system can be used in a
wavelength-division multiplexing (WDM) system to provide the
optical data signal at a WDM channel.
[0004] However, in order to achieve a complete data link capable of
handling optical data signals at a single wavelength at Tbit/s
rates, an optical receiver in the data link must be able to detect
the optical data signals at Tbit/s rates. Such an optical receiver
singly capable of detecting Tbit/s optical data signals of a single
wavelength is not commercially available at the present time to the
applicant's knowledge. Although optical detectors capable of
detecting optical signals at a rate of 750 GHz or with response
times on the order of picoseconds or less are known in the art,
these devices are still in their experimental stages hence are not
yet commercialized.
[0005] Prior art data links have not had to deal with this problem
of the unavailability of Tbit/s rate optical receivers because
light modulation systems capable of transmitting optical data
signals at Tbit/s rates at a given wavelength are not currently
known at this time to the applicant's knowledge, with the exception
of the light modulation system disclosed in U.S. Pat. No.
5,768,002. Existing high speed light modulation systems generally
consist of a series of N light modulators, each light modulator
corresponding to one channel out of N channels and producing
optical data signals at rates of less than Tbit/s at a unique
wavelength corresponding to a particular WDM channel out of a range
of wavelengths .lambda..sub.1-.lambda..sub.N. The multitude of
optical data signals over the range of wavelengths, each optical
data signal having its own unique wavelength, are multiplexed onto
an optical fiber. The multiplexed signal is received by a
demultiplexer which separates the multiplexed signal into the
separate optical data signals according to wavelength. The
separated optical data signals are then detected by a plurality of
optical detectors, each operating at less than Tbit/s rates.
[0006] The prior art data link as a whole can be made to transmit
data at Tbit/s rates by using a plurality of data sources, optical
sources and optical detectors all operating at Gbit/s rates. For
example, if a hundred optical sources are provided (i.e., N=100),
with each optical source generating an optical signal at 10 Gbit/s
and at a distinct wavelength out of the wavelength range
.lambda..sub.1 through .lambda..sub.100, then the aggregate optical
data rate is one Tbit/s. Following transmission through an optical
fiber, a WDM multiplexer combines the one hundred optical signals
such that the resulting multiplexed signal contains all optical
signals of the wavelength range .lambda..sub.1 through
.lambda..sub.100. The WDM demultiplexer then separates the
multiplexed signal into distinct wavelengths to be detected by a
hundred optical detectors, each detector operating at 10 Gbits/s.
As a result, it is possible to transmit data using the prior art
data link at an aggregate rate of 1 Tbit/s.
[0007] It is submitted, however, the aforedescribed prior art data
link has a number of disadvantages. In order to increase the total
data transmission rate of the prior art data link above
approximately 1 Tbit/s, the number of channels, and hence the
number of data sources and optical sources used in the data link,
must be increased. This condition may be satisfied by narrowing the
wavelength differences between channels thus fitting more channels
into a given wavelength range .lambda..sub.1 through .lambda..sub.N
and/or widening the wavelength range between .lambda..sub.1 and
.lambda..sub.N. However, narrowing the wavelength differences
between the channels increases the probability of data transmission
error due to potential optical signal overlap and crosstalk and
puts a greater demand on the WDM demultiplexer to accurately
separate the optical signals into the distinct wavelengths. As is
well known in the art, there is only a finite range available for
use as the wavelength range .lambda..sub.1 through .lambda..sub.N,
outside of which significant optical signal loss occurs due to the
material properties of the optical fiber as well as other
components of an optical communication system, such as repeaters
and amplifiers. Therefore, the wavelength range cannot be widened
indefinitely using currently available technology, hence it is
difficult to increase the number of channels to increase the data
transmission rate. Furthermore, increasing the number of different
wavelengths traveling simultaneously through the optical fiber also
increases the probability of occurrence of undesired, nonlinear
optical effects during transmission. Care must be taken to avoid
such nonlinear optical effects, thus adding to the overall
complexity and cost of this prior art data link at faster data
transmission rates. Still further, WDM channels require a guard
band on either side of the specific channel wavelength in order to
reduce wavelength overlap and crosstalk between channels. Since no
data can be transmitted on the guard band, the wavelengths used in
the guard band are essentially wasted bandwidth.
[0008] The present invention provides a high speed data link which
serves to resolve the problems described above with regard to prior
art data links in a heretofore unseen- and highly advantageous way
and which provides still further advantages.
SUMMARY OF THE INVENTION
[0009] As will be described in more detail hereinafter, there is
disclosed herein a mid-infrared transmitter for providing a light
signal in a free-space communication system. In one aspect of the
invention, the mid-infrared transmitter includes an arrangement for
producing electromagnetic radiation having a certain wavelength in
a mid-infrared wavelength range. The mid-infrared transmitter
further includes an arrangement for modulating the electromagnetic
radiation so as to provide a train of light pulses having the
certain wavelength as the light signal.
[0010] In another aspect of the invention, a mid-infrared free
space data link includes a transmitter arrangement producing a
transmitter output. The transmitting arrangement includes a source
of light, which light has a certain wavelength in a mid-infrared
wavelength range, and a modulator arrangement for modulating the
light so as to provide a train of light pulses having the certain
wavelength as the transmitter output. The mid-infrared free space
data link further includes a directing arrangement for directing
the transmitter output to a particular location and, at the
particular location, a receiving arrangement configured for
receiving the transmitter output.
[0011] In still another aspect of the invention, a method for
providing a mid-infrared free space data link includes transmitting
a signal containing data. The transmitting step includes generating
light having a certain wavelength in a mid-infrared wavelength
range, and modulating the light so as to provide a train of light
pulses having the certain wavelength as the signal. The method
further includes directing the signal toward a particular location
and, at the particular location, receiving the signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention may be understood by reference to the
following detailed description taken in conjunction he drawings
briefly described below.
[0013] FIG. 1 is a diagrammatic illustration of a data link
designed in accordance with the present invention and employing a
superconducting layer and a wavelength converting device to
modulate light.
[0014] FIG. 2 is a diagrammatic illustration of an alternative
embodiment of a data link designed in accordance with the present
invention.
[0015] FIG. 3 is a diagrammatic illustration of yet another
embodiment of a data link manufactured in accordance with the
present invention.
[0016] FIGS. 4A and 4B are diagrammatic illustrations of
alternative embodiments of an optical transmitter as shown in FIG.
3.
[0017] FIGS. 5A, 5B and 5C are diagrammatic illustrations of
alternative embodiments of an optical communication system designed
in accordance with the present invention.
[0018] FIG. 6 is a diagrammatic illustration of an embodiment of an
electrical receiver suitable for use in the present invention.
DETAILED DESCRIPTION
[0019] Turning now to the drawings, wherein like components are
indicated by like reference numbers throughout the various figures,
attention is immediately directed to FIG. 1, which illustrates one
embodiment of a high speed data link, generally indicated by the
reference numeral 100, fabricated in accordance with the present
invention. Data link 100 includes a transmitter arrangement 112,
optical fiber 113 and receiver arrangement 114. Transmitter
arrangement 112 includes a data source 116 which provides data
input 117 to a superconducting arrangement 118. Data source 116 can
be, for example, a high speed modulating circuit, electronic signal
generator, serializer, SONET Add/Drop multiplexer, ATM switch or a
combination thereof. Superconducting arrangement 118 is switched
between a normal state and a superconducting state according to
data input 117. A light source 120 is used to generate light 122 at
a wavelength .lambda..sub.0 directed toward superconducting
arrangement 118. Light source 120 may be a laser, light emitting
diode, etc., as is commonly known in the art. By way of example and
not a limitation, a quantum cascade (QC) laser is suitable for use
as light source 120. QC lasers are capable of emitting light over a
variety of infrared wavelengths that are compatible with
superconducting arrangement 118, ranging from a few microns to tens
of microns at high peak powers of hundreds of milliwatts (See, for
example, A. Tredicucci, et al, "High-power inter-miniband lasing in
intrinsic superlattices," Applied Physics Letters, 72 (19), pp.
2388-2390). QC lasers are also tunable, thus allowing more
flexibility in the specification of superconducting arrangement
118. Other examples of appropriate light sources include a bismuth
antimony BiSb laser (see, for example, A. G. Alksanyan, et al,
"Semiconductor laser made of Bi.sub.1-xSb.sub.x," Soviet Journal of
Quantum Electronics, vol. 14, no. 3, pp. 336-8), germanium laser
and gas lasers, such as a laser including a carbon dioxide-pumped
cavity with methanol.
[0020] Continuing to refer to FIG. 1, superconducting arrangement
118 is designed in such a way that it is transparent to light of
wavelength .lambda..sub.0 when it is in its normal state, and
blocks the transmission of light of wavelength .lambda..sub.0 when
it is in its superconducting state. As a result, light 122 is
blocked or transmitted according to data input 117, and light 122
is modulated by superconducting arrangement 118 to produce a series
of optical pulses 123 at wavelength .lambda..sub.0. The details of
the switching mechanism of superconducting arrangement 118 are
described in detail in U.S. Pat. No. 5,768,002.
[0021] Still referring to FIG. 1, it should be noted that the
wavelength .lambda..sub.0 of light 122 and optical pulses 123 is
chosen such that wavelength .lambda..sub.0 is transmitted or
blocked by superconducting arrangement 118 depending on whether
superconducting arrangement 118 is in its normal or superconducting
state. As described in U.S. Pat. No. 5,768,002, superconducting
arrangement 118 can perform the function of encoding data input 117
as optical pulses 123 when the wavelength .lambda..sub.0 is in the
far infrared (IR) range (approximately 14 .mu.m or greater). For
example, the wavelength .lambda..sub.0=25 .mu.m is chosen in the
embodiment of the present invention shown in FIG. 1. Unfortunately,
since light of far IR wavelengths attenuate rapidly during
transmission through conventional, silica glass optical fiber, it
is not practical to directly transmit optical pulses of far IR
wavelengths through the optical fiber 113. To counter this problem,
optical pulses 123 are directed into a wavelength converting device
125, which converts optical pulses 123 at the wavelength
.lambda..sub.0 into optical pulses 126 at a shorter wavelength
.lambda..sub.conv. The wavelength .lambda..sub.conv are in the
range of approximately 0.5 to 2 .mu.m, preferably on the order of
1.3 or 1.5 .mu.m so as to be compatible with conventional optical
fibers. Optical pulses 126 are then directed into one end of
optical fiber 113.
[0022] Optical pulses 126 shown in FIG. 1 are received at an
opposing end of optical fiber 113 by receiving arrangement 114.
Receiving arrangement 114 includes an all-optical (AO)
demultiplexer 132. AO demultiplexer 132 divides optical pulses 126
into a plurality of low data rate, optical pulses 126' also with
wavelength .lambda..sub.conv. Then, each set of divided, low data
rate, optical pulses 126' are detected by an optical detector 134.
For example, AO demultiplexer 132 can be designed to divide optical
pulses 126 such that a first data bit goes to a first optical
detector, a second data bit goes to a second optical detector, and
so on. The optical detectors are, for example, a plurality of
interchangeable, generic detectors designed to be sensitive to
light of wavelength .lambda..sub.conv. Therefore, while transmitter
arrangement 112 generates optical data signals at Tbit/s rates at
wavelength .lambda..sub.conv receiver arrangement 114 is able to
detect the Tbit/s rate optical data signals using Gbit/s detectors
by dividing optical pulses 126 into slower optical pulses 126',
thus achieving Tbit/s rate transmission through data link 100.
[0023] Data link 100 takes advantage of the high data rate that is
possible with a transmitter arrangement based on a superconducting
arrangement to provide a complete, high speed data link.
Transmitter arrangement 112 as shown in FIG. 1 is capable of
encoding data input 117 onto optical pulses 126 of wavelength
.lambda..sub.conv at data rates of approximately 1 Tbit/s. Unlike
the aforementioned prior art data link which requires a plurality
of data sources and optical sources operating simultaneously at
different wavelengths to achieve an aggregate data transmission
rate of 1 Tbit/s, transmitter arrangement 112 is singly capable of
transmitting optical data in the form of optical pulses at 1 Tbit/s
rates at a single wavelength. It is submitted that this feature of
optical source 10 is highly advantageous in at least one respect
since, by splitting optical pulses 126 into low data rate, optical
pulses 126', receiver arrangement 114 is able to detect the high
data rate, optical pulses 126 using a series of low speed detectors
without the need to use multiple wavelengths and a WDM
demultiplexer.
[0024] It should also be understood that only one wavelength,
wavelength .lambda..sub.conv is transmitted through optical fiber
113 of data link 100 illustrated in FIG. 1. Therefore, potential
problems associated with the prior art data such as crosstalk and
nonlinear optical effects due to the presence of multiple
wavelengths in the optical fiber are eliminated in data link 100.
Furthermore, data link 100 does not require the use of a guard
band, thus the available bandwidth outside of wavelength
.lambda..sub.conv is not wasted.
[0025] An additional advantage associated with data link 100
resides in the fact that data link 100 is readily up-scalable.
Since the overall, data transmission rate depends mainly on the
speed at which superconducting arrangement 118 can be modulated, as
faster materials or switching schemes are developed for the
superconducting arrangement such that transmitter arrangement 112
produces higher rate optical pulses 126, additional optical
detectors 134 can be added in receiver arrangement 114 to
accommodate the increased data rate without a need to develop
faster optical detectors than are currently available commercially
today. As faster optical detectors do become available, the number
of optical detectors may be accordingly decreased, thus potentially
simplifying the high speed data link of the present invention.
[0026] Attention is now directed to FIG. 2 in conjunction with FIG.
1. FIG. 2 illustrates another data link produced in accordance with
the present invention, generally indicated by the reference number
200. Data link 200 includes a transmitter arrangement 212 as well
as optical fiber 113 and receiver arrangement 114, the latter two
components being essentially identical to the corresponding
components of data link 100 illustrated in FIG. 1 with like
reference numbers. Therefore, the discussion of data link 200 will
concentrate on transmitter arrangement 212 which is modified with
respect to transmitter arrangement 112 of data link 100.
[0027] Like transmitter arrangement 112 of FIG. 1, transmitter
arrangement 212 shown in FIG. 2 includes light source 120 which
generates light 122 of wavelength .lambda..sub.0 directed towards
superconducting arrangement 118. Superconducting arrangement 118 is
switched between its normal and superconducting states according to
data input 117, thus generating optical pulses 123 of wavelength
.lambda..sub.0. Optical pulses 123 are directed into wavelength
converting device 125 which converts optical pulses 123 of
wavelength .lambda..sub.0 into optical pulses 126 of wavelength
.lambda..sub.conv.
[0028] However, the way in which data input 117 is generated is
different in transmitter arrangement 212 as compared to that of
transmitter arrangement 112. Transmitter arrangement 212 includes a
plurality of optical transmitters 150 and 152 arranged to transmit
optical modulation pulses in parallel into an optoelectronic (OE)
multiplexer 154. OE multiplexer 154 reads the optical modulation
pulses in parallel then serializes the electrical data from the
optical modulation pulses, thus generating data input 117. It
should be noted that data input 117 is a serial, electrical signal.
For example, commercially-available, 10 Gbit/s optical
transmitters, which are well-known in the art, are suitable for use
as optical transmitters 150 and 152. OE multiplexer 154 can be
designed to generate data input 117 at rates of one Tbit/s or
higher depending on the number of optical transmitters used. In
this way, slower optical transmitters can be multiplexed to
generate high speed data signals for switching superconducting
arrangement 118, and optical pulses 126 are generated at rates of
Tbit/s or higher. OE multiplexer 154 is, for instance, a
multiplexer based on Josephson Junction circuitry. Alternatively,
the plurality of optical transmitters 150 and 152 and OE
multiplexer 154 is replaceable by a system of a plurality of fiber
optic transmitters, receivers, optical fibers and a high speed
shift register, as described in U.S. Pat. No. 5,768,002.
[0029] Referring now to FIG. 3, a diagrammatic illustration of
still another embodiment of a data link manufactured in accordance
with the present invention, generally indicated by reference
numeral 300, is shown. Data link 300 includes a transmitter
arrangement 312, an optical fiber 313 and a receiver arrangement
314. Transmitter arrangement 312 includes a series of optical
transmitters 212'. Each optical transmitter 212' is identical to
transmitter arrangement 212 illustrated in FIG. 2 with a
modification that optical transmitter 212' is designed to generate
optical pulses 126' of a particular wavelength out of the
wavelength range .lambda..sub.conv1 to .lambda..sub.convN in such a
way that no two optical transmitters generate optical pulses 126'
at the same wavelength. As described in the discussion of FIG. 2,
each optical transmitter 212' is capable of generating optical
pulses 126' at rates of Tbit/s or higher.
[0030] The series of optical pulses 126' are directed into a WDM
multiplexer 324 which combines the series of optical pulses 126'
such that the series of optical pulses 126', each set of optical
pulses 126' having a distinct wavelength out of the wavelength
range .lambda..sub.conv1 to .lambda..sub.convN, are together
directed into optical fiber 313 as optical pulses 326. Optical
pulses 326 contains all sets of optical pulses 126' such that all
optical data encoded into the series of optical pulses 126' are
transmitted down optical fiber 313 simultaneously. In this way,
optical pulses 326 carries optical data signals at an aggregate
rate which is greater than Tbit/s.
[0031] Optical pulses 326 are transmitted through optical fiber 313
and into receiver arrangement 314, where optical pulses 326 are
received by a WDM demultiplexer 332. WDM demultiplexer 332
separates optical pulses 326 back into the series of optical pulses
126' according to wavelength. Each set of optical pulses 126' is
directed into an optical receiver 114', which is identical to
receiver arrangement 114 of FIG. 1 with a modification that AO
demultiplexer 132 is designed to divide a set of optical pulses
126' of at least one particular wavelength out of the wavelength
range .lambda..sub.conv1 to .lambda..sub.convN into a plurality of
low data rate, optical pulses 126". Thus, each optical receiver
114' is capable of receiving optical pulses 126' at rates of Tbit/s
or higher. Furthermore, by using a WDM demultiplexer and a
plurality of wavelengths with each wavelength carrying optical data
at rates of Tbit/s, receiver arrangement 314 is able to receive
optical data at an aggregate rate of much higher than Tbit/s.
[0032] Turning to FIGS. 4A and 4B, two possible alternatives for
the optical transmitter 212' are illustrated. Although two specific
schemes for the optical transmitter are shown, these configurations
are not to be considered as limiting. Various modifications may be
made to the optical transmitter alternatives shown in FIGS. 4A and
4B while keeping with the spirit of the present invention.
[0033] FIG. 4A is a diagrammatic illustration of an optical
transmitter 212'A, which is the X.sup.th optical transmitter in a
series of N optical transmitters. Optical transmitter 212'A
includes a wavelength converting device 125' with a pump laser 340
and a nonlinear optical crystal 342. Pump laser 340 provides a pump
beam 344 of a predetermined wavelength .lambda..sub.pX directed at
nonlinear optical crystal 342. Optical pulses 123 from
superconducting arrangement 118 are also incident on nonlinear
optical crystal 342. Since the specific wavelength generated by the
wavelength converting device 125' depends on the material
characteristics of nonlinear optical crystal 342 and the wavelength
of pump laser 340, the predetermined wavelength .lambda..sub.pX of
pump beam 344 is selected such that optical pulses 123 of
wavelength .lambda..sub.0 are converted into optical pulses of a
particular wavelength .lambda..sub.convX out of the wavelength
range .lambda..sub.conv1 to .lambda..sub.convN By using identical
nonlinear optical crystals 342 in all optical transmitters 212' and
selecting a suitable pump laser wavelength .lambda..sub.pX for each
wavelength converting device 125', the series of optical
transmitters 212' are designed in such a way that each optical
transmitter 212' generates optical pulses 126' of a particular
wavelength out of the wavelength range .lambda..sub.conv1 to
.lambda..sub.convN and no two optical transmitters generate optical
pulses 126' at the same wavelength. For example, each optical
transmitter 212' is equipped with a distinct pump laser which lases
at the specific pump wavelength .lambda..sub.pX. Alternatively,
every optical transmitter 212' is equipped with an identical,
tunable pump laser and each tunable pump laser is programmed at the
factory or in the field to the appropriate wavelength
.lambda..sub.pX. In yet another implementation, all wavelength
converting devices includes identical pump lasers and a suitable
nonlinear optical crystal can be selected for each wavelength
converting device 125' such that each optical transmitter 212'
generates optical pulses 126' of wavelength .lambda..sub.convX out
of the wavelength range .lambda..sub.conv1 to .lambda..sub.convN
and no two optical transmitters generate optical pulses 126' at the
same wavelength. As another possibility, all wavelength converting
devices may include identical pump lasers and nonlinear optical
crystals, with each nonlinear optical crystal being provided with,
for example, a temperature and/or current control device to tune
the material properties of the nonlinear optical crystal such that
that each optical transmitter 212' generates optical pulses 126' of
wavelength .lambda..sub.convX out of the wavelength range
.lambda..sub.conv1 to .lambda.convN and no two optical transmitters
212'A generate optical pulses 126' at the same wavelength. It
should be noted that all components (other than wavelength
converting device 125') of optical transmitter 212'A are
essentially the same as those of optical transmitter 212 shown in
FIG. 2.
[0034] An alternative scheme for an optical transmitter is shown in
FIG. 4B, generally indicated by reference numeral 212'B. Each
optical transmitter 212'B in this case is equipped with a generic,
tunable laser as light source 120' which emits light 122' of
wavelength .lambda..sub.X, where X=an integer between 1 and N
corresponding to the X.sup.th optical transmitter 212'B. All
components (other than light source 120') of optical transmitter
212'B are identical to those of optical transmitter 212 shown in
FIG. 2. Light 122' is directed at superconducting arrangement 118,
which in turn produces optical pulses 123' of wavelength
.lambda..sub.X. Each optical transmitter 212'B in the series of
optical transmitters is provided with a generic wavelength
converting device 125. The wavelength .lambda..sub.X of light 122'
produced at tunable laser of each optical transmitter 212'B is then
tuned to provide light of a distinct wavelength such that
wavelength converting device 125 converts the wavelength
.lambda..sub.X of optical pulses 123' into optical pulses 126' of a
particular wavelength .lambda..sub.convX out of the wavelength
range .lambda..sub.conv1 to .lambda..sub.convN and no two optical
transmitters 212'B generate optical pulses 126' at the same
wavelength. The aforementioned QC laser is an example of a light
source which is suitable for use as the tunable laser in this
configuration. A bismuth laser, antimonide laser, germanium laser
or a gas laser, such as a laser including a carbon dioxide-pumped
cavity with methanol, may also be used in conjunction with an
appropriate tuning mechanism (such as a temperature, current and/or
magnetic field controller).
[0035] It should be noted that the use of a tunable pump laser as
pump laser 340 as shown in FIG. 4A or a tunable laser as light
source 120' as shown in FIG. 4B adds a routing capability to data
link 300 of FIG. 3. By tuning the output wavelength of the series
of optical transmitters 212' in data link 300, it is possible to
direct data from any optical transmitter 212' to any optical
receiver 114', thus routing the transmitted data to the desired
recipient.
[0036] Returning to FIG. 3, although data link 300 uses a plurality
of wavelengths as in the aforedescribed prior art data link, it is
submitted that data link 300 has advantages over the prior art data
link. Since data link 300 is capable of transmitting at Tbit/s data
rates on each train of wavelength converted optical pulses 126',
the selection of specific wavelengths out of the wavelength range
.lambda..sub.conv1 to .lambda..sub.convN is more flexible than in
prior art data links, which depend on the packing of as many
channels as possible into the limited wavelength range. Data link
300 can achieve multiple Tbit/s data rates with fewer constraints
on the wavelengths chosen such that the wavelengths and channel
spacings used can be specifically selected to reduce problems such
as cross talk and nonlinear optical effects. In addition, although
data link 300 requires the use of a guard band on either side of
each channel wavelength, the fast data rate capability at each
channel and the flexibility in wavelength selection allow more
efficient use of the available bandwidth and higher data rates as
compared to prior art WDM data links.
[0037] Attention is now directed to FIGS. 5A-5C, which illustrate
alternative embodiments of an optical communication system designed
in accordance with the present invention. FIGS. 5A-5C show optical
communication systems 400A-400C, which correspond to high speed
data links 100, 200 and 300 of FIGS. 1-3, respectively, where
optical fiber 113 is generally replaced by a satellite transmission
system 413 in each of FIGS. 1-3. The transmitter and receiver
arrangements of FIGS. 5A-5C are essentially the same as those shown
in FIGS. 1-3, respectively, therefore explanation of FIGS. 5A-5C is
restricted to the details of the satellite transmission system.
[0038] Satellite transmission system 413 in FIGS. 5A-5C includes a
reflector 415A, which directs the optical pulses from the
corresponding transmitter arrangement toward a satellite 417.
Satellite 417 then redirects the optical pulses toward a desired
location where the redirected optical pulses are intercepted by an
interceptor arrangement 415B. The optical pulses intercepted by
interceptor arrangement 415B are received by the corresponding
receiving arrangement. Reflector 415A and interceptor arrangement
415B are, for example, conformable mirrors (such as the
micro-machined membrane mirror manufactured by SY Technology).
Conformable mirrors are useful in the satellite transmission system
of FIGS. 5A-5C because they can be used to compensate for possible
distortion of the optical pulses. Such distortion in the optical
pulses are potentially produced during transmission to and from the
satellite due to, for example, atmospheric disturbances. In the
case of the embodiments of the optical communication systems shown
in FIGS. 5A-5C, wavelength converting device 125 in each of the
transmitter arrangements may be adjusted to produce optical pulses
at wavelengths appropriate for satellite communications, such as in
the far-infrared wavelengths. Moreover, reflector 415A, interceptor
arrangement 415B and/or satellite 417 can include an off-axis
paraboloid (may be conformable) for focusing or collimating the
optical pulses. The conformable mirror and/or off-axis paraboloid
as well as other components used in satellite transmission system
413 should be compatible with wavelengths used in free space
communication systems such as, for example, wavelengths in the
mid-infrared range (3 to 5 .mu.m, 8 to 12 .mu.m, etc.). For
example, wavelength converting device 125 can be configured to
generate optical pulses 126 in the aforementioned mid-infrared
range. Alternatively, a light source capable of producing light 122
in the mid-infrared range can be used as light source 120 in
combination with a superconducting material compatible with the
mid-infrared range as superconducting arrangement 118 such that
frequency converting device 125 may be eliminated altogether. In
other words, if light source 120 produces light in the mid-infrared
range, superconducting arrangement 118 can be used to produce
optical pulses 123 in the mid-infrared range such that optical
pulses 123 may be directed toward satellite 417 without the need
for frequency converting device 125. An example of suitable
superconducting materials include mercury-based superconductor
materials, which have critical temperatures of 134.degree. K and
164.degree. K under pressure. According to the Bardeen Cooper
Schreiffer theory a superconductor with a critical temperature of
164.degree. K would have a critical wavelength of 11 .mu.m.
Therefore a superconductor arrangement 118 made form strained
mercury cuprates can be used with light 122 with wavelengths
greater than 11 .mu.m. In this way, the high speed data link of the
present invention is applicable to free-space communication systems
as well as for optical fiber-based systems.
[0039] Turning now to FIG. 6, an alternative option to the
aforedescribed optical receivers 114 and 114' is shown. FIG. 6
illustrates a receiver 514, which is based on a superconducting
detector 540 and is suitable for use in the high speed data link of
the present invention. Such use of superconducting films as
bolometers or photodetectors are known in the art (see, for
example, U.S. Pat. No. 5,155,093 issued to Den et al., U.S. Pat.
No. 5,600,172 issued to McDevitt et al. and Roman Soblewski,
"Ultrafast dynamics of nonequilibrium quasiparticles in
high-temperature superconductors," Superconducting and Related
Oxides: Physics and Nanoengineering III, ed. by I. Bozovic and D.
Pavuna, Proc. SPIE, 3481, 480-491 (1998)). When a train of light
pulses containing optical data, such as optical pulses 126 of FIG.
1, is incident on superconducting detector 540, optical pulses 126
are converted into a train of voltage spikes 542. Voltage spikes
542 are received by an electrical demultiplexer 544. Electrical
demultiplexer 544 performs a task analogous to AO demultiplexer 132
of FIG. 1 in that, where as AO demultiplexer 132 divides optical
pulses 126 into a plurality of low data rate, optical pulses 126',
electrical demultiplexer 544 divides voltage spikes 542 into a
plurality of low data rate, voltage spikes 542'. Voltage spikes
542' are received by a plurality of electrical detectors 548, which
can be low speed electrical detectors that are commercially
available. Receiver 514 of FIG. 6 is usable in situations in which
it may be desirable to use an electrical signal detection scheme
rather than an optical signal detection scheme.
[0040] Since the high speed data link and associated method
disclosed herein may be provided in a variety of different
configurations and the method may be practiced in a variety of
different ways, it should be understood that the present invention
may be embodied in many other specific ways without departing from
the spirit or scope of the invention. For example, an optical
detector may be configured in essentially unlimited number of ways
to cooperate with an AO demultiplexer in such a way that a series
of optical pulses are divided into lower rate, optical pulses by
the AO demultiplexer and detected by the optical detector.
Furthermore, additional optical devices such as, but not limited
to, optical amplifiers, switches, routers, and repeaters may be
inserted in-line with an optical fiber for transmitting optical
pulses from a transmitter arrangement to a receiver arrangement.
Still further, the optical fiber may be eliminated as the
transmission medium between the transmitter and receiver
arrangements. In this way, wavelengths outside of the optical fiber
transmission window can be used and the data link of the present
invention becomes applicable to data transmission using
electromagnetic waves outside of the optical wavelength range
(microwave data transmission, for example). Such modifications are
considered to be within the scope of the present invention so long
as the teachings herein are applied. Therefore, the present
examples are to be considered as illustrative and not restrictive,
and the invention is not to be limited to the details given herein,
but may be modified within the scope of the appended claims.
* * * * *