Reservoir Computing Device

Abstract

To subject a light region to masking treatment without using an ultrashort optical pulse light source.SOLUTION: A reservoir computing device includes generation means for generating a plurality of carrier light, modulation means for modulating light including the plurality of carrier light by a combined signal obtained by combining an input signal with a sinusoidal signal, and thereby generating modulation light, a dispersive medium, an optical member which is provided on the downstream side of the dispersive medium and optically achieves a reservoir layer, and processing means for allowing the modulation means to input the modulation light to the dispersive medium, and thereby processing output light output from the optical member, wherein the processing means has reception means for performing coherent reception of the output light, and converting the output light into an electric signal, and compensation means for compensating an output signal corresponding to the input signal included in the electric signal, on the basis of a pilot signal corresponding to the sinusoidal signal included in the electric signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to reservoir computing technology. [Background technology]

[0002] A recurrent neural network (RNN) consists of an input layer, a recurrent layer (reservoir layer), and an output layer. Generally, when an RNN is trained, the weights (coefficients) of the input layer, recurrent layer, and output layer are updated. Reservoir computing is a type of RNN that only updates the weights of the output layer during training, and does not update the weights of the input layer or recurrent layer. In reservoir computing, the weights of the input layer and recurrent layer are set to, for example, randomly generated fixed values. Instead of updating only the weights of the output layer, reservoir computing increases the number of neurons in the recurrent layer.

[0003] A hardware implementation of the recurrent layer (reservoir layer) of this reservoir computing is called "physical reservoir computing." Non-Patent Documents 1 to 3 disclose physical reservoir computing. In physical reservoir computing, in order to express the random weight of the reservoir layer, a masking process is performed on input data and then input to the reservoir layer. Non-Patent Documents 1 and 2 implement the masking process in the digital domain. On the other hand, Non-Patent Document 3 discloses a configuration in which the masking process is implemented in the optical domain. By implementing the masking process in the optical domain, it is possible to perform the masking process faster than when implemented in the digital domain. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Appeltant,L.,et.al.,Constructing optimized binary masks for reservoir computing with delay systems.Sci Rep 4,3629,2014 [Non-patent document 2] Quentin Vinckier,et.al.,"High-performance photonic reservoir computer based on a coherently driven passive cavity",Optica 2,438-446,2015 [Non-patent document 3] Nakajima,M.,et.al.,"Scalable reservoir computing on coherent linear photonic processor"Commun Phys4,20,2021 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Non-Patent Document 3 requires an ultrafast light source such as an ultrashort optical pulse light source, which makes the configuration complicated.

[0006] The present disclosure provides a technique for performing masking in the optical domain without using an ultrashort optical pulse light source. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a reservoir computing device includes a generating means for generating a plurality of carrier lights, a modulating means for generating modulated light by modulating light including the plurality of carrier lights with a composite signal obtained by combining an input signal and a sinusoidal signal, a dispersive medium, an optical element that optically realizes a reservoir layer and is arranged downstream of the dispersive medium, and a processing means for processing output light output from the optical element when the modulating means inputs the modulated light into the dispersive medium, wherein the processing means includes a receiving means for coherently receiving the output light and converting it into an electrical signal, and a compensating means for compensating an output signal corresponding to the input signal contained in the electrical signal based on a pilot signal corresponding to the sinusoidal signal contained in the electrical signal. [Effects of the Invention]

[0008] According to the present disclosure, masking can be performed in the optical domain without using an ultrashort optical pulse light source. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a reservoir computing device, according to one embodiment. [Figure 2] 4 is an illustration of internal signals of a reservoir computing device, according to one embodiment. [Figure 3] FIG. 2 is a block diagram of a processing unit according to one embodiment. [Figure 4] FIG. 2 is a block diagram of a processing unit according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0011] FIG. 1 is a configuration diagram of a reservoir computing device according to this embodiment. A multi-wavelength light source 1 generates and outputs continuous light (carrier light) of multiple different frequencies. FIG. 2A shows the frequency components of the light output by the multi-wavelength light source 1. In FIG. 2A, reference numeral 90 denotes a carrier light. Each carrier light 90 may be generated individually by an independent light source included in the multi-wavelength light source 1. Alternatively, some of the multiple carrier lights 90 may be generated by a single light source in a phase-locked state. The frequency spacing of the multiple carrier lights 90 may be, for example, on the order of terahertz (THz). For example, if all of the multiple carrier lights 90 satisfy the mode-locking condition, the time waveform of the light including the multiple carrier lights will be an ultrashort pulse. However, as described above, in this embodiment, it is not necessary to satisfy the mode-locking condition. The multiple carrier lights 90 generated by the multi-wavelength light source 1 are input to a modulator 2.

[0012] An input signal indicating data to be input to the reservoir computing device is input to the combiner 6. The oscillator 7 generates a sine wave signal of a predetermined frequency and outputs it to the combiner 6. The frequency of the sine wave signal is outside the band of the input signal. The combiner 6 combines the input signal and the sine wave signal and outputs the combined signal to the modulator 2.

[0013] The modulator 2 collectively modulates a plurality of carrier lights 90 from the multi-wavelength light source 1 with a composite signal. FIG. 2(B) shows the frequency components of the modulated light output by the modulator 2. Reference numeral 80 denotes a component corresponding to the input signal (input signal component 80), and reference numeral 81 denotes a component corresponding to the sine wave signal (sine wave signal component 81). A set 82 of the input signal component 80 and the sine wave signal component 81 is generated for each carrier light 90. In other words, the modulated light includes a set 82 of the input signal component 80 and the sine wave signal component 81 corresponding to each of the plurality of carrier lights 90.

[0014] The output light from the modulator 2 is input to the dispersive medium 3. The dispersive medium 3 applies dispersion to the modulated light from the modulator 2 according to the frequency. As a result, masking is performed on each component of the modulated light according to the dispersion applied by the dispersive medium 3. In this embodiment, multiple carrier lights 90 with wide frequency intervals are used, so high-speed masking is performed in the dispersive medium 3. A reservoir section 4 is provided downstream of the dispersive medium 3. The reservoir section 4 includes an optical circuit (optical component) that optically realizes a reservoir layer. As an example, the reservoir section 4 has a delay loop configuration. Processing corresponding to the connections between neurons is performed in the reservoir section 4. The modulated light input to the dispersive medium 3 passes through the dispersive medium 3 and the reservoir section 4 and is input to the processing section 5 as output light.

[0015] 3 is a configuration diagram of the processing unit 5. The coherent receiver 51 of the processing unit 5 has a local light source, and coherently receives the output light from the reservoir unit 4 to generate an electrical signal, which is then output to the compensation unit 52. The electrical signal includes a set of output signal components corresponding to the input signal components 80 and pilot signal components corresponding to the sinusoidal signal components 81 in FIG. 2(B). The set of output signal components and pilot signal components each correspond to the carrier light 90.

[0016] In this embodiment, the multiple carrier lights 90 are not mode-locked and therefore have relative phase noise, etc. Therefore, the output light passing through the dispersive medium 3 also fluctuates depending on the phase noise, etc. This corresponds to the fact that the content of the masking process in the dispersive medium 3 changes over time. Because the content of the masking process needs to be constant regardless of the passage of time, it is necessary to compensate for the effects of phase noise, etc. to keep the content of the masking process constant. Furthermore, the local light source of the compensation unit 52 also contains phase noise, etc. In other words, the output signal component is affected not only by the phase noise, etc. of the carrier light 90 but also by the phase noise, etc. of the local light source. Therefore, the compensation unit 52 compensates the output signal component based on the pilot signal component to compensate for the effects of phase noise, etc. contained in the output signal component. Specifically, the compensation unit 52 multiplies the complex conjugate component of the pilot signal component by the corresponding output signal component, i.e., the output signal component corresponding to the same carrier light 90. This makes it possible to compensate for the effects of phase noise, etc. contained in the output signal component. Each output signal component compensated by the compensation unit 52 is also compensated for the fact that the content of the masking process changes over time.

[0017] For example, when some of the plurality of first carrier lights among the plurality of carrier lights 90 are generated so as to satisfy the mode locking condition, it is possible to configure the output signal components corresponding to each of the plurality of first carrier lights to be compensated collectively based on the pilot signal component corresponding to one of the plurality of first carrier lights.

[0018] Each output signal component compensated by the compensation unit 52 is input to the post-processing unit 53. The post-processing unit 53 performs processing on each output signal component according to the application of the reservoir computing device.

[0019] The processing unit 5 can also be configured as shown in FIG. 4. The frequency separation unit 54 in FIG. 4 separates the output light from the reservoir unit 4 into first to third output lights according to the frequency band. The number of separations is not limited to three and can be any value equal to or greater than two. Each of the first to third output lights includes one or more sets of output signal components and pilot signal components. The frequency separation unit 54 outputs the first output light to the first path, the second output light to the second path, and the third output light to the third path. A coherent receiver 51 and a compensation unit 52 are provided in each of the first to third paths. By separating the output light from the reservoir unit 4 according to the frequency band, the bandwidth to be processed by the compensation unit 52 can be narrowed.

[0020] As described above, according to this embodiment, masking processing can be performed in the optical domain without using an ultrashort optical pulse light source.

[0021] The above configuration makes it possible to perform masking in the optical domain without using an ultrashort optical pulse light source, thereby contributing to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization, and foster innovation." [Explanation of symbols]

[0022] 1: multi-wavelength light source, 2: modulator, 3: dispersive medium, 4: reservoir section, 5: processing section, 51: coherent receiver, 52: compensation section

Claims

1. generating means for generating a plurality of carrier lights; a modulation means for generating modulated light by modulating the light including the plurality of carrier lights with a combined signal obtained by combining an input signal and a sinusoidal signal; a dispersive medium; an optical element that optically embodies a reservoir layer, disposed downstream of the dispersive medium; a processing unit that processes output light output from the optical element by inputting the modulated light into the dispersive medium by the modulation unit; Equipped with The processing means a receiving means for coherently receiving the output light and converting it into an electrical signal; a compensation means for compensating an output signal corresponding to the input signal included in the electrical signal based on a pilot signal corresponding to the sinusoidal signal included in the electrical signal; 1. A reservoir computing device comprising:

2. the processing means further includes frequency separation means for separating the output light into a plurality of output lights according to frequency bands; The reservoir computing device of claim 1 , wherein the receiving means and the compensating means are provided for each of the plurality of output lights.

3. The reservoir computing device of claim 1, wherein the compensation means compensates the output signal corresponding to the first carrier light included in the electrical signal based on the pilot signal corresponding to the first carrier light among the plurality of carrier lights included in the electrical signal.

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