JP-7856171-B2 - Photoprocessing apparatus, photoprocessing system, and photoprocessing method

JP7856171B2JP 7856171 B2JP7856171 B2JP 7856171B2JP-7856171-B2

Inventors

北翔太
納富雅也
新家昭彦
池田幸平

Assignees

ＮＴＴ株式会社

Dates

Publication Date: 20260511
Application Date: 20230130

Claims (8)

An optical branching element that splits the input light, One of the branched light beams propagates through one of the optical paths, and an electro-optic converter is provided in which the light beam is modulated by an input electrical signal. The other optical path through which the other of the branched light propagates is provided with a first phase shifter for adjusting the phase of the other light and a delayed waveguide. The system includes a photoelectric conversion unit that outputs the difference between the output of one optical path and the output of the other optical path, The length of the delay waveguide is the difference in optical path lengths between the one optical path and the other optical path. A photoprocessing apparatus in which the wavelength of the input light is set such that the wavelength dependence of the output of the photoelectric conversion unit corresponding to a predetermined input electrical signal is suppressed .
An optical branching element that splits the input light, One of the branched light beams propagates through one of the optical paths, and an electro-optic converter is provided in which the light beam is modulated by an input electrical signal. The other optical path through which the other of the branched light propagates is provided with a first phase shifter for adjusting the phase of the other light and a delayed waveguide. The system includes a photoelectric conversion unit that outputs the difference between the output of one optical path and the output of the other optical path, The length of the delay waveguide is the difference in optical path lengths between the one optical path and the other optical path. The wavelength of the input light is set such that the output of the photoelectric conversion unit corresponding to a predetermined input electrical signal substantially matches the desired output corresponding to the predetermined input electrical signal. A photoprocessing apparatus in which the R2 coefficient of determination characteristic based on the difference between the output of the photoelectric conversion unit and the desired output has multiple peaks, and the wavelength intervals between the peaks are equal .
An optical branching element that splits the input light, One of the branched light beams propagates through one of the optical paths, and an electro-optic converter is provided in which the light beam is modulated by an input electrical signal. The other optical path through which the other of the branched light propagates is provided with a first phase shifter for adjusting the phase of the other light and a delayed waveguide. The system includes a photoelectric conversion unit that outputs the difference between the output of one optical path and the output of the other optical path, The length of the delay waveguide is the difference in optical path lengths between the one optical path and the other optical path. The wavelength of the input light is set such that the output of the photoelectric conversion unit corresponding to a predetermined input electrical signal substantially matches the desired output corresponding to the predetermined input electrical signal. A photoprocessing apparatus in which the input light has multiple wavelengths, and the interval Δλ between the multiple wavelengths is represented by equation (A). Δλ = 2πn eff ΔL/δφ (A) Here, n eff is the effective refractive index of the waveguide including wavelength dependence, ΔL is the optical path length difference, and δφ is the phase error of the optical path.
An optical branching element that splits the input light, One of the branched light beams propagates through one of the optical paths, and an electro-optic converter is provided in which the light beam is modulated by an input electrical signal. The other optical path through which the other of the branched light propagates is provided with a first phase shifter for adjusting the phase of the other light and a delayed waveguide. The system includes a photoelectric conversion unit that outputs the difference between the output of one optical path and the output of the other optical path, The length of the delay waveguide is the difference in optical path lengths between the one optical path and the other optical path. The wavelength of the input light is set such that the output of the photoelectric conversion unit corresponding to a predetermined input electrical signal substantially matches a desired output corresponding to the predetermined input electrical signal. An optical processing apparatus comprising an optical analog arithmetic circuit between the electro-optic converter and the photoelectric conversion unit in one of the aforementioned optical paths.
The aforementioned optical path has M waveguides, The optical analog arithmetic circuit is an M×N optical analog arithmetic circuit, The other optical path has N waveguides, The N outputs of the M×N optical analog arithmetic circuit are connected to the photoelectric conversion unit. The optical apparatus according to claim 4 , wherein the delayed waveguide consists of N waveguides.
The aforementioned electro-optic converter n Y-branch elements connected in cascades, n Y-junction elements connected in cascades, The system comprises n waveguide arms connecting one output of each of the n Y-branch elements to one input of each of the n Y-junction elements, The waveguide arm, starting from the Y-branch element side, The second phase shifter, The optical apparatus according to claim 1 or claim 2, comprising a phase modulator.
Light source and Electrical signal generation unit, A photoprocessing device to which light output from the light source and an electrical signal output from the electrical signal generation unit are input, A measuring unit for measuring the output of the aforementioned photoprocessing device, The system comprises a wavelength selection unit to which the output of the measurement unit is input, The output of the wavelength selection unit is input to the light source . The aforementioned photoprocessing apparatus is An optical branching element that splits the input light, One of the branched light beams propagates through one of the optical paths, and an electro-optic converter is provided in which the light beam is modulated by an input electrical signal. The other optical path through which the other of the branched light propagates is provided with a first phase shifter for adjusting the phase of the other light and a delayed waveguide. The system includes a photoelectric conversion unit that outputs the difference between the output of one optical path and the output of the other optical path, The length of the delay waveguide is the difference in optical path lengths between the one optical path and the other optical path. An optical processing system in which the wavelength of the input light is set to substantially coincide with the output of the photoelectric conversion unit corresponding to a predetermined input electrical signal and a desired output corresponding to the predetermined input electrical signal .
An optical processing method in an optical processing system comprising a light source, an electrical signal generation unit, an optical processing device, a measurement unit, and a wavelength selection unit, wherein the optical processing device comprises one optical path through which one of the input light beams propagates and another optical path through which the other light beam propagates, and the one optical path and the other optical path have a difference in optical path length, The light source provides a first light by sweeping the wavelength of light, The electrical signal generation unit outputs a first electrical signal, The optical processing apparatus outputs a first processing result in accordance with the first light and the first electrical signal, The measurement unit performs the step of measuring the first processing result, The wavelength selection unit compares the measured first processing result with a desired processing result corresponding to the first electrical signal and selects a wavelength in which the measured first processing result and the desired processing result substantially coincide. The light source outputs a second light having the selected wavelength, The steps include: the electrical signal generation unit outputs a second electrical signal; A photoprocessing method comprising the step of the photoprocessing device performing processing using the second light and the second electrical signal.

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) Published on the following website posted on February 25, 2022: https://confit.atlas.jp/guide/event-img/jsap2022s/22p-E303-9/public/pdf?type=in (2) Published on the following website posted on July 31, 2022: https://confit.atlas.jp/guide/event/cleopr2022/participant_login?eventCode=cleopr2022 The present invention relates to an optical processing apparatus, an optical processing system, and an optical processing method that perform optical processing (calculations) using wavelength division multiplexing. In recent years, advances in silicon photonics technology have enabled the mass production of on-chip optical devices with low loss and high yield. These on-chip optical devices primarily include passive optical devices such as waveguides, branching, merging, and crossing, as well as active optical devices such as phase modulators and photodetectors. Consequently, large-scale optical integrated circuits and their application technologies, such as optical processing units (optical analog computing units) including optical neural network accelerators, are being researched and developed. Optical analog arithmetic units have the following features: (1) Analog complex number calculations can be performed with zero energy consumption using optical interference (energy saving). (2) Calculation delay can be reduced by the propagation of light (low latency). (3) Multiple calculations can be realized with a single linear circuit by division multiplexing based on spacetime and wavelength (high throughput). On-chip optical analog arithmetic units utilize optical interference. Therefore, if energy is not required to maintain the state of a specific optical interference system—that is, if a fixed phase shifter that does not carry current can be used—the energy required for linear operations such as matrix operations can be reduced to zero. Matrix operations account for the majority of power consumption in neural network computations. Therefore, power consumption can be significantly reduced by performing matrix operations using optical methods (Non-Patent Literature 1). On the other hand, on-chip optical computing units have limitations on the input data size. For example, controlling one phase shifter, which is an elemental device of an optical computing unit, requires one electrical analog input. Therefore, if the size of the matrix is M, then M² - M control electrodes are required, and it is thought that the limit for electrically implementable devices is around 100 elements (~9900 electrodes). In this way, the number of elemental devices of an optical computing unit is limited, which limits the size of the matrix that can be computed using light at once. Therefore, the application of on-chip optical computing units to convolutional neural networks, which can be used even with small matrix sizes, is considered important. In the case of convolutional neural networks, the input data can be divided and input while fixing the matrix elements to predetermined values, and calculations can be performed. Here, input data can be divided into multiple wavelength channels for computation (wavelength division multiplexing). In wavelength division multiplexing, data from different regions is assigned to each wavelength and simultaneously input to an optical matrix calculation circuit. By demultiplexing and detecting the output of the optical matrix calculation circuit, the computation results for each region can be obtained at once. In other words, the matrix operations required for a convolutional neural network can be executed simultaneously in a single circuit. This increases throughput by the number of wavelength channels. In wavelength division multiplexing (WDM), suppressing the wavelength dependence of the optical computing circuit is crucial to increase the number of wavelength channels that can be multiplexed and to enable the optical computing circuit to operate over a wide wavelength range. Therefore, it is necessary to (1) suppress the wavelength dependence of the optical elements (mainly 1x2 or 2x2 couplers) used in the circuit, and (2) ensure that the lengths of each optical waveguide (optical path length) are equal in a configuration where multiple optical waveguides are arranged in parallel within the optical circuit (hereinafter referred to as "equality"). Here, equality is necessary for all paths resulting from the ON/OFF combinations of switches that switch the path of signal light within the circuit. As a result, even if the wavelength changes, the relative phase difference between each path does not change, thus maintaining wavelength independence in the optical computing circuit. The calculations within the optical analog arithmetic unit are performed using complex numbers based on optical interference, and therefore the results are also complex numbers. Homodyne detection allows the complex number calculation results to be extracted as an electrica