JP4014020B2 - Optical signal processing system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical communication system using a semiconductor device, and more particularly to an optical signal processing system and an optical signal processing for selecting and detecting a pulse train of a desired channel from an optical pulse train of a multi-channel signal arranged in time series with high sensitivity. The present invention relates to a device (optical integrated circuit) and an optical signal processing method.
[0002]
[Prior art]
In recent years, there has been a growing demand for higher capacity in optical fiber communication, and multi-channel communication that simultaneously transmits signals of a plurality of channels has become increasingly important. The multi-channel communication system has a great effect not only on an increase in capacity but also on expandability and flexibility of the system by expanding a network having a necessary capacity at a necessary place. In order to cope with future advanced networking, it is indispensable to further increase the amount of information by increasing the number of channels.
[0003]
For multi-channel communication, a method using a plurality of time-series arranged multi-channel signals and a wavelength multiplexing communication method using a plurality of wavelengths as a carrier wave are known.
[0004]
In such a high-density optical communication system, pulse light of a multi-channel signal propagates through a fiber and is sent to each receiver constituting the network. In order for each receiver to detect a pulse train of a specific channel from the weak multi-channel optical pulse train, it is first converted into a multi-channel electrical pulse by a pin photodiode, and then electrically specified by a silicon integrated circuit. It is necessary to select the pulse train of the channel signal. However, as the number of recipients increases, the light intensity decreases at each end of the network, which makes it difficult to receive high-speed pulses with high sensitivity and to select them without error.
[0005]
[Problems to be solved by the invention]
In the conventional method using a silicon integrated circuit, since it is governed by the operation speed of the silicon device, for example, high-sensitivity processing of a pulse train of several Gb / sec or more is not easy. In order to solve these difficulties, we have already proposed a circuit that can distribute signals on all channels using electrical and optical means using gallium arsenide (GaAs) static induction transistors (SIT), which are high-speed devices. Has been.
[0006]
In view of the above-described problems, the present invention does not use a high-speed large-scale integrated circuit (high-speed LSI), and only a pulse train of a single channel or a small number of channels among a large number of channels arranged in time series can be increased by optical means. It is to provide an optical signal processing system capable of accurately selecting with sensitivity.
[0007]
Another object of the present invention is to provide a wavelength division multiplexing optical system that can easily select and detect pulse light of a channel having a desired frequency without using a high-speed LSI that requires advanced microfabrication technology. It is to provide a signal processing system.
[0008]
Still another object of the present invention is to provide a compact optical signal processing device capable of selecting only a single or a small number of channel pulse trains from a large number of channels with high sensitivity.
[0009]
Still another object of the present invention is to provide an optical signal processing system method that allows a receiver to select and receive only one desired channel with high sensitivity.
[0010]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a Raman waveguide functioning as a semiconductor Raman amplifier, input signal incident means for inputting an optical signal consisting of a number of channels arranged in time series into the Raman waveguide, A sync pulse synchronized with a specific channel is generated, a pump light source that inputs the sync pulse to the Raman waveguide, and an optical signal of the specific channel that is synchronously amplified from the Raman waveguide by the pump light source A first feature is that the optical signal processing system includes at least a photoelectric conversion circuit that converts signals.
[0011]
In a semiconductor Raman amplifier, when the frequency of signal light, the frequency of pump light, and the frequency of phonons in the semiconductor are ω _s , ω _L , and ω _ph , respectively,
ω _L = ω _s + ω _ph (1)
If the above relationship is satisfied, the signal light ω _s is amplified by the pump light having the frequency ω _L. That is, if a multi-channel signal optical pulse train is introduced into a semiconductor Raman amplifier and pump light synchronized with a specific channel among the multi-channels is introduced, the pump among the multi-channel optical signals introduced into the semiconductor Raman amplifier. Only the pulse train synchronized with the optical pulse is amplified and its amplitude increases. Various values can be used for the frequency ω _ph of the phonon in the semiconductor by selecting the semiconductor material and its crystal orientation.
[0012]
Therefore, in the optical signal processing system according to the first aspect of the present invention, a semiconductor Raman amplifier is used to select and amplify a single channel from a multi-channel pulse train. The amplified signal is easily converted into an electric signal by the photoelectric conversion circuit and can be detected. In this way, a desired channel can be selected with a very simple circuit.
[0013]
In the first aspect of the present invention, the Raman waveguide includes a gallium phosphide (GaP) core layer, and gallium phosphide / aluminum phosphide disposed on the lower, upper, and side surfaces of the gallium phosphide (GaP) core layer, respectively. Preferably, the heterostructure is at least composed of an (Al _x Ga _1-x P) cladding layer. This is because GaP has a large Raman scattering cross-sectional area and a very small half-value width of the Raman scattering spectrum. In addition, GaP has no absorption based on crystal defects in the near-infrared wavelength region used in optical communication.
[0014]
In the first feature of the present invention, a first optical waveguide coupled to a light incident end of a Raman waveguide, a wavelength selecting fiber coupler provided in a part of the first optical waveguide, and a wavelength selecting fiber coupler. It is preferable to further include a second optical waveguide that is coupled to the first optical waveguide and inputs light from the pump light source to the Raman waveguide. Furthermore, it has the 3rd and 4th optical waveguide couple | bonded with the 1st optical waveguide via the optical circulator, The pin photodiode which couple | bonded the photoelectric conversion circuit with this 3rd optical waveguide, and this pin photo If a gate circuit that inputs the output of the diode and a reference voltage generator that supplies a reference voltage for discriminating the pulse amplitude to the gate circuit, the influence of noise can be greatly reduced.
[0015]
Alternatively, the first pin photodiode coupled to the third optical waveguide, the branch provided in the fourth optical waveguide, the fifth optical waveguide branched from the fourth optical waveguide by this branch, and the It is preferable to further include a second pin photodiode coupled to the fifth optical waveguide and a differential amplifier connected to the first and second pin photodiodes. This is effective even in a wavelength multiplexing communication system in which signal light does not have a single optical frequency but uses a plurality of optical frequencies. In this case, the pump optical frequency is tuned to one optical frequency and synchronized to the pulse train of one channel within that frequency.
[0016]
The first to fifth optical waveguides described above may be optical fibers or semiconductor waveguides.
[0017]
The second feature of the present invention relates to a wavelength division multiplexing communication system using light of a plurality of wavelengths as a carrier wave. That is, the second feature of the present invention is that a Raman waveguide functioning as a semiconductor Raman amplifier, input signal incident means for inputting a plurality of optical signals having different frequencies to the Raman waveguide, and a plurality of optical signals Generates a synchronization pulse synchronized with an optical signal of a specific frequency, and inputs the synchronization pulse to the Raman waveguide. The optical signal of the specific frequency synchronously amplified from the Raman waveguide is converted into an electrical signal. An optical signal processing system including at least a photoelectric conversion circuit.
[0018]
In the wavelength division multiplexing communication system, when the frequency of the signal light is ω _s1 , ω _s2 , ω _s3 ,... Ω _sn , the frequency ω _{Lj of the} pump light is ω _Lj = ω _sj + ω _ph (j = 1 , 2, 3, ..., n) ... (2)
If the above relationship is satisfied, the signal light having the frequency ω _sj is amplified by the pump light having the frequency ω _Lj . That is, if a plurality of optical signals having different frequencies are introduced into the semiconductor Raman amplifier and a frequency ω _Lj pump light synchronized with an optical signal having a specific frequency among the plurality of optical signals is introduced, the semiconductor Raman amplifier can be introduced. Of the introduced optical signals, only the signal light having the frequency ω _sj synchronized with the pump light pulse is amplified, and the amplitude thereof increases. Therefore, in the optical signal processing system according to the second aspect of the present invention, the semiconductor Raman amplifier selects and amplifies signal light having a specific single frequency ω _sj from optical signals having a plurality of frequencies. Used for. Various values can be used for the frequency ω _ph of the phonon in the semiconductor by selecting the semiconductor material and its crystal orientation. The amplified signal is easily converted into an electric signal by the photoelectric conversion circuit and can be detected. In this way, a channel having a desired frequency ω _sj can be selected with a very simple circuit. As described in the first feature, the Raman waveguide is composed of at least a GaP core layer and Al _x Ga _1-x P cladding layers respectively disposed on the lower, upper, and side surfaces of the GaP core layer. A heterostructure is preferable. This is because GaP has a large Raman scattering cross section, a very small half width of the Raman scattering spectrum, and no absorption based on crystal defects in the near infrared wavelength region.
[0019]
For this reason, in the optical signal processing system according to the second feature of the present invention, the pump light source has a plurality of different _values corresponding to a plurality of frequencies ω _s1 , ω _s2 , ω _s3,. A plurality of synchronous pulses having frequencies ω _L1 , ω _L2 , ω _L3 ,..., Ω _Ln may be arranged. Furthermore, each optical signal having a plurality of frequencies is composed of a number of channels arranged in time series, and the synchronization pulse is synchronized with a specific channel among the plurality of channels. For example, the same processing as the first feature of the present invention can be performed for each wavelength (frequency).
[0020]
Specifically, in the second feature of the present invention, a first optical waveguide coupled to the light incident end of the Raman waveguide, a wavelength selecting fiber coupler provided in a part of the first optical waveguide, A plurality of second optical waveguides coupled to the first optical waveguide through the wavelength selecting fiber coupler and inputting light from the plurality of pump light sources to the Raman waveguide, and an optical circulator connected to the first optical waveguide. A plurality of coupled third optical waveguides, a fourth optical waveguide coupled to the first optical waveguide via an optical circulator, and a plurality of first pins respectively coupled to the plurality of third optical waveguides A photodiode, a branch provided in the fourth optical waveguide, a plurality of fifth optical waveguides branched from the fourth optical waveguide by the branching, and a plurality coupled to each of the plurality of fifth optical waveguides The second pin of And preparative diode may be further have a configuration a plurality of first and second pin photodiode connected to a plurality of differential amplifiers. Here, the first to fifth optical waveguides may be optical fibers or semiconductor waveguides such as a ridge structure.
[0021]
A third feature of the present invention relates to an optical integrated circuit. That is, the third feature of the present invention is that the substrate, the Raman waveguide disposed on the substrate, and the input signal incident means for inputting an optical signal composed of a number of channels arranged in time series to the Raman waveguide. And a pump light source for generating a synchronization pulse synchronized with a specific channel among a number of channels and inputting the synchronization pulse to the Raman waveguide; and a pump light source disposed on the substrate to The optical signal processing device (optical integrated circuit) includes at least a photoelectric conversion circuit that converts an optical signal of a specific channel synchronously amplified by a waveguide into an electric signal.
[0022]
In the third feature of the present invention, the “substrate” may be a semiconductor substrate or an organic substrate such as a glass epoxy substrate. A substrate such as an alumina (Al ₂ O ₃ ) substrate or an insulating metal substrate may also be used. An optical signal according to the third aspect of the present invention can be obtained by integrating a heterostructure Raman waveguide composed of at least a GaP core layer and an Al _x Ga _1-x P cladding layer on a semiconductor substrate such as GaP. Processing devices can be monolithically integrated. In this case, a semiconductor waveguide having a similar ridge structure may be used as an input waveguide for input signal incident means or a pump light source. These Raman waveguides and other semiconductor waveguides can be easily manufactured by using epitaxial growth technology, photolithography technology, reactive ion etching (RIE), and the like. Alternatively, the input signal incident means and the input waveguide of the pump light source may be integrated in a hybrid on an insulating substrate using an optical fiber. In any case, a compact optical signal processing device (optical integrated circuit) can be provided with a simple structure.
[0023]
The fourth feature of the present invention is that a step of inputting an optical signal consisting of a number of channels arranged in time series at a frequency ω _s into a Raman waveguide having a semiconductor phonon frequency ω _ph , A step of inputting pump light that is synchronized with a specific channel and satisfies a condition of ω _L = ω _s + ω _ph into a Raman waveguide, and a step of Raman-amplifying only an optical signal of the specific channel that is synchronized with the pump light, The optical signal processing method comprises at least a step of converting only the Raman-amplified optical signal into an electrical signal.
[0024]
As described in the first feature, when the relationship of ω _L = ω _s + ω _ph is satisfied, the signal light ω _s is Raman amplified by the pump light having the frequency ω _L. Therefore, in the fourth feature, when pump light synchronized with a specific channel among a large number of channels is introduced, only the pulse train synchronized with the pump light pulse is amplified and the amplitude thereof is increased. Various values can be used for the frequency ω _ph of the phonon in the semiconductor by selecting the semiconductor material and its crystal orientation. The amplified signal can be easily converted into an electric signal by a photoelectric conversion circuit and detected. For this reason, according to the fourth feature of the present invention, a desired channel can be selected very easily.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0026]
(First embodiment)
FIG. 1 is a block diagram showing an outline of an optical signal processing system according to a first embodiment of the present invention. As shown in FIG. 1, the optical signal processing system according to the first embodiment of the present invention includes a Raman waveguide 11 functioning as a semiconductor Raman amplifier, and a number of time-series aligned Raman Raman waveguides 11. An input signal input means (10, 12) for inputting an optical signal composed of channels, and a pump light source 4 for generating a synchronization pulse synchronized with a specific channel among a large number of channels and inputting it to the Raman waveguide 11; And a photoelectric conversion circuit 6 that converts an optical signal of a specific channel synchronously amplified by the pump light source 4 from the Raman waveguide 11 into an electric signal. The Raman waveguide 11 that functions as a semiconductor Raman amplifier has, for example, a semiconductor waveguide structure composed of a gallium phosphide (GaP) core layer and a gallium phosphide-aluminum phosphide (Al _x Ga _1-x P) cladding layer. The signal light of frequency ω _s and the pump light of frequency ω _L propagate through the core layer. More specifically, the Raman waveguide 11 according to the first embodiment of the present invention includes an Al _x Ga _1-x P first cladding layer formed on a GaP substrate, and this Al _x Ga _1-x P A GaP core layer formed on the first cladding layer, an Al _x Ga _1-x P second cladding layer formed on the top and side surfaces of the GaP core layer, and an Al _x Ga _1-x P second cladding layer What is necessary is just to comprise by the heterostructure which consists of a GaP protective layer etc. which coat | covered and formed. The light incident end 12 of the Raman waveguide 11 is coated with antireflection, and the reflection end 13 is formed with a multilayer reflective film having a reflectance close to 100%. The multilayer reflective film may be formed by depositing 10 to 20 layers of silicon oxide film (SiO ₂ ) / titanium oxide film (TiO ₂ ) or the like. In consideration of the Raman scattering cross section, the crystal orientation of the GaP core layer may be selected so that the light incident end 12 and the reflection end 13 are the (100) plane. The distance between the light incident end 12 and the reflection end 13 may be selected from 0.5 mm to 20 mm, preferably about 3 mm to 10 mm.
[0027]
In the first embodiment of the present invention, a first optical waveguide (first optical fiber) 10 is coupled to the light incident end 12 of the Raman waveguide 11, and the first optical waveguide 10 includes A wavelength selecting fiber coupler 9 is provided. The “input signal incident means” of the present invention includes the light incident end 12 and the first optical waveguide (first optical fiber) 10.
[0028]
Further, a second optical waveguide (second optical fiber) 31 that is coupled to the first optical waveguide 10 via the wavelength selection fiber coupler 9 and inputs the light of the pump light source 4 to the Raman waveguide 11 is provided. Yes. The semiconductor laser diode serving as the pump light source 4 is pulse-driven by the pulse generator 5. Alternatively, the semiconductor laser diode 4 may be driven using a mode synchronization signal generator instead of the pulse generator 5. The pump light having the frequency ω _L from the semiconductor laser diode 4 and the multi-channel pulse signal light having the frequency ω _s sent by the first optical fiber 10 are combined by the wavelength selecting fiber coupler 9 to be combined with the first optical fiber. 10 is introduced into the light incident end 12 of the Raman waveguide 11.
[0029]
The first optical waveguide (first optical fiber) 10 is further connected to third and fourth optical waveguides (third and fourth optical fibers) 32 and 34 coupled via the optical circulator 8. Yes. The signal light reflected by the reflection end 13 while being Raman-amplified in the Raman waveguide 11 is transmitted to the third optical waveguide (third optical fiber) 32 via the optical circulator 8 and sent to the photoelectric conversion circuit 6 to be electrically Converted to a signal.
[0030]
The phonon frequency ω _{ph of} GaP constituting the core layer of the Raman waveguide 11 functioning as a semiconductor Raman amplifier is 12 THz. Therefore, for example, when the frequency ω _{s of the} signal light is 350 THz (857 nm), 362 THz (829 nm) is selected as the frequency ω _{L of the} pump light from the equation (1).
[0031]
FIG. 2A shows a pulse train of input signal light, FIG. 2B shows a pulse train of pump light, and FIG. 2C shows a pulse train of output signal light. As shown in FIG. 2A, the pulse train of the input signal light has a large number of channels C ₁ , C ₂ , C ₃ , C ₄ , C ₅ , C ₆ ,.
[0032]
In the first embodiment of the present invention, the following description will be given on the assumption that all the signal light pulses have the same optical frequency ω _s . FIG. 2 shows a case where all channels are bit 1 for simplicity.
[0033]
When the channel C ₁ is selected, the pulse P _{1 of the} pump light is synchronized with the pulse of the optical channel C ₁ as shown in FIG. As a result, as shown in FIG. 2C, only the pulse of channel O ₁ corresponding to the pulse of channel C ₁ is amplified as the output signal. As shown in FIG. 2 (c), the output signal is
・ "0" state with no signal,
-A state of "1" that is not amplified,
-"2" state where the signal strength is stronger than this "1" state,
One of the three-valued states consisting of Here, the state of “2” does not necessarily have twice the strength of “1”. Any signal that has a level that can be clearly distinguished from the “1” state and is Raman-amplified so that the signal intensity is stronger than the “1” state may be used. Similarly, for each of the other channels, the pulse (pulse train) of any one channel is amplified by synchronizing the pulse (pulse train) of the pump light with the pulse (pulse train) of the desired channel. 2 "state. In the case of a GaP semiconductor Raman amplifier, the amplification bandwidth is 25 GHz, so that one desired pulse train can be selected from a high-speed multichannel optical pulse train of 10 Gb / sec or more. For example, the amplification degree is 10 dB, which is a level that can be detected sufficiently without error.
[0034]
The Raman waveguide 11 has a taper structure. Even when an optical fiber is used as the first optical waveguide 10, the light incident end 12 of the Raman waveguide 11 is easily made highly efficient by making it a cross section having a dimension close to the core diameter of the first optical fiber 10. Thus, the first optical fiber 10 and the Raman waveguide 11 can be coupled. In addition, Raman amplification by the Raman waveguide 11 amplifies only a desired optical frequency, and therefore does not operate unstable as an amplifier. When the semiconductor laser diode 4 of the pump light source is driven by current pulses, so-called chirping occurs and the optical frequency fluctuates. In the first embodiment of the present invention, a bias current is given to the semiconductor laser diode 4 in advance. It is possible to keep the frequency chirping at or below the bandwidth of Raman amplification by the Raman waveguide 11. Since the light incident end 12 is coated without reflection, no resonance occurs. For this reason, stable operation without temperature fluctuation is possible.
[0035]
FIG. 3 is a block diagram showing a photoelectric conversion circuit 6 having a pulse amplitude discrimination circuit 100 for discriminating only an electric signal corresponding to a desired optical pulse Raman-amplified from the output pulse train. A signal from the Raman amplification system 200 is transmitted to the third optical fiber via the optical circulator 8 and input to the pin photodiode 14. The electrical signal pulse detected by the pin photodiode 14 is a ternary value of “0” where there is no signal, “1” which is not amplified, or “2” which is amplified at a higher voltage. (It should be noted that “2” means a state different from “1” as described above, and does not necessarily have twice the strength of “1”. ). Therefore, if the gate circuit 15 for inputting the output of the pin photodiode 14 is configured to have a threshold value with a pulse voltage of “1” or more and “2” or less, the gate circuit 15 performs Raman amplification. Only the state “2” of the selected channel is output from the gate circuit 15 as a pulse. In FIG. 3, reference numeral 16 denotes a reference voltage generator for providing a threshold value of the gate circuit. Pulses that are not amplified are weak but cause errors, and must be removed. By providing the pulse amplitude discrimination circuit 100, the influence of noise is greatly reduced and the error rate is improved. For example, when the level of “1” that is not amplified is a weak value close to the limit of the S / N ratio of the photodetector, the influence of noise is set by setting the reference voltage larger than that and smaller than the amplified level. Is greatly reduced.
[0036]
(Second Embodiment)
FIG. 4 is a block diagram showing an outline of an optical signal processing system according to the second embodiment of the present invention, and shows an example in which a photoelectric conversion circuit different from that in FIG. 3 is used. A signal from the Raman amplification system 200 is transmitted through the third optical fiber via the optical circulator 8, input to the first pin photodiode 14, and detected by the first pin diode 14. The signal light from the optical fiber is taken out as a reference signal by the branch 20 and detected by the second pin photodiode 19. Output pulses of the first photodiode 14 and the second pin photodiode 19 are compared by a differential amplifier 23. Only the amplified pulse is taken out as an output electric signal O _{D of the} differential amplifier. Compared with FIG. 3, the example of FIG. 4 requires a reference branch 20 and thus has a drawback that the signal light intensity is reduced. However, the signal light is not a single optical frequency, a plurality of optical frequencies _{ω s1, ω s2, ω s3} , even in the wavelength multiplexing communication system · · · · · omega _sn is used, the method of FIG. 4 is valid is there. In this case, if the pump optical frequency ω _Lj is tuned to one optical frequency ω _sj and is synchronized with the pulse train of one channel within the frequency, the frequency ω that satisfies the condition of the above-mentioned formula (2). Only the signal light of _sj is amplified and its amplitude increases.
[0037]
In the optical signal processing system according to a second embodiment of the present invention, the pump light source, a plurality of frequencies _{ω s1, ω s2, ω s3} , in response to · · · · · omega _sn, a plurality of different frequencies omega _L1, ω _L2, ω _L3, may be a plurality arranged to generate a sync pulse · · · · · omega _Ln. That is, the first optical waveguide 10 coupled to the light incident end of the Raman waveguide, the wavelength selecting fiber coupler provided in a part of the first optical waveguide 10, and the first via the wavelength selecting fiber coupler. And a plurality of second optical waveguides for inputting light from a plurality of pump light sources to the Raman waveguide. Further, in FIG. 4, a plurality of third optical waveguides 32 coupled to the first optical waveguide 10 via the optical circulator 8, and a fourth optical waveguide coupled to the first optical waveguide 10 via the optical circulator. 34, a plurality of first pin photodiodes 14 respectively coupled to the plurality of third optical waveguides 32, a branch 20 provided in the fourth optical waveguide 34, and a branch 20, thereby A plurality of fifth optical waveguides 35 branched from the waveguide 34, a plurality of second pin photodiodes 19 respectively coupled to the plurality of fifth optical waveguides 35, and a plurality of first and second pin photos What is necessary is just to comprise so that it may have the some differential amplifier 23 connected to the diodes 14 and 19. FIG.
[0038]
(Other embodiments)
Although the present invention has been described by the first and second embodiments described above, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.
[0039]
For example, in the description of the first and second embodiments, the pump light having the frequency ω _L and the multi-channel pulse signal light having the frequency ω _s are incident on the Raman waveguide 11 by the first optical fiber 10. Although the case where it is introduced into the end 12 has been described, a semiconductor waveguide having a ridge structure or a diffusion layer structure may be used instead of the first optical fiber 10. Similarly, it goes without saying that at least one of the second to fifth optical fibers 10 may be a semiconductor waveguide. Furthermore, if all of the first to fourth or first to fifth optical fibers are semiconductor waveguides and these are monolithically integrated on a semiconductor substrate such as GaP, an optical integrated circuit can be configured. It is. Instead of monolithic integration, a hybrid integration on an organic substrate such as a glass epoxy substrate or a substrate such as alumina (Al ₂ O ₃ ) or an insulating metal substrate may be used.
[0040]
In addition to the above GaP, various semiconductors such as gallium arsenide (GaAs) and indium phosphide (InP) can be used as the semiconductor Raman amplifier.
[0041]
As described above, the present invention naturally includes various embodiments not described herein. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.
[0042]
【The invention's effect】
According to the present invention, it is possible to provide an optical signal processing system that can easily select and detect pulse light of a desired channel without using a high-speed LSI due to the amplification effect of the semiconductor Raman amplifier.
[0043]
According to the present invention, there is provided an optical signal processing system of a wavelength multiplexing communication system that can easily select and detect pulse light of a desired channel without using a high-speed LSI that requires advanced fine processing technology. Can be provided.
[0044]
According to the present invention, it is possible to provide an optical signal processing device that can easily select and detect pulse light of a desired channel with a compact structure without using an advanced high-speed LSI.
[0045]
According to the present invention, it is possible to provide an optical signal processing system method that can select and receive only a desired channel with high sensitivity in a simple and error-free manner.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of an optical signal processing system according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating an optical pulse synchronization method according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a means for converting an optical pulse into an electric pulse in the optical signal processing system according to the first embodiment of the present invention.
FIG. 4 is a block diagram showing an outline of an optical signal processing system according to a second embodiment of the present invention, and is a diagram showing another means for converting an optical pulse into an electric pulse.
[Explanation of symbols]
4 Pump light source (semiconductor laser diode)
5 Pulse Generator 6 Photoelectric Conversion Circuit 8 Optical Circulator 10 First Optical Waveguide (First Optical Fiber)
11 Raman waveguide 12 Light incident end 13 Reflecting end 14 pin photodiode (first pin photodiode)
19 Second pin photodiode 15 Gate circuit 16 Reference voltage generator 20 Branch 23 Differential amplifier 31 Second optical waveguide (second optical fiber)
32 Third optical waveguide (third optical fiber)
34 Fourth optical waveguide (fourth optical fiber)
35 fifth optical waveguide (fifth optical fiber)
100 Pulse amplitude discriminating circuit 200 Raman amplifier system

Claims (3)

A Raman waveguide that functions as a semiconductor Raman amplifier having a unique phonon frequency and a constant amplification bandwidth ;
Input signal incident means for inputting a frequency-multiplexed optical signal composed of a number of channels, each having a different frequency and arranged in time series at each frequency, to the Raman waveguide,
Corresponding to the respective frequencies, wherein one of the multiple channels, a specific frequency, and a specific time-series signal pulse synchronized with the synchronizing pulses generated respectively, the phonons from each synchronous pulses each frequency number has a frequency shifted by frequency, the respective synchronization pulse is input to the Raman waveguide, so that only the optical signal of a specific frequency is amplified, frequency variations at each frequency is less than the amplification bandwidth A plurality of pump light sources each kept and frequency tuned;
At least composed optical signal processing system and a photoelectric conversion circuit for converting an optical signal of the particular channel which has been amplified respectively synchronized from the Raman waveguide to each electrical signal. The Raman waveguide includes a gallium phosphide (GaP) core layer and gallium phosphide aluminum (Al _x Ga _1-x P) disposed on the lower, upper, and side surfaces of the gallium phosphide (GaP) core layer. 2. The optical signal processing system according to claim 1, comprising at least a clad layer. A first optical waveguide coupled to a light incident end of the Raman waveguide;
A wavelength selecting fiber coupler provided in a part of the first optical waveguide;
A plurality of second optical waveguides coupled to the first optical waveguide via the wavelength selecting fiber coupler, and inputting light from the plurality of pump light sources respectively to the Raman waveguide;
A plurality of third optical waveguides coupled to the first optical waveguide via an optical circulator;
A fourth optical waveguide coupled to the first optical waveguide via an optical circulator;
A plurality of first pin photodiodes respectively coupled to the plurality of third optical waveguides;
A branch provided in the fourth optical waveguide;
A plurality of fifth optical waveguides branched from the fourth optical waveguide by the branch;
A plurality of second pin photodiodes respectively coupled to the plurality of fifth optical waveguides;
3. The optical signal processing system according to claim 1, further comprising a plurality of differential amplifiers connected to the plurality of first and second pin photodiodes.

Images