Optical computing device

Abstract

To calculate exclusive OR of an input light signal of multiple bits.SOLUTION: Branching devices 11-1 to 11-4 generate first and second intermediate light signals by dividing an input light signal. Intermediate waveguides 31-1 to 31-4 transmit the first intermediate light signal and inputs the same to a star coupler 13-1. Phase shifters 12-1, 12-2 change the phase of an intermediate light signal transmitted via the intermediate waveguides 31-1, 31-2. Output waveguides 33-1, 33-2 transmit the output light signal of the star coupler 13-1. The intermediate waveguides 32-1 to 32-4 transmit the second intermediate light signal and input the same to the star coupler 13-2. Phase shifters 12-3, 12-4 change the phase of an intermediate light signal transmitted via the intermediate waveguides 32-1, 32-4. Output waveguides 34-1, 34-2 transmit the output light signal of the star coupler 13-2. An output circuit 20 computes exclusive OR of an input light signal by computing AND of an output light signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical computing device.

Background Art

[0002] The capacity of information communication and the processing power of computer systems have increased significantly, and the requirements for functions have continued to become more sophisticated. In such a situation, conventional computing technologies based on silicon integrated circuits are beginning to show limitations in terms of processing speed and power consumption due to the limitations of semiconductor miniaturization.

[0003] Photonic computing is a promising candidate for a new computing technology to replace conventional computing technologies due to the excellent properties of light such as interference, broadband, multiplicity, and quantum nature.

[0004] For example, Patent Document 1 discloses an optical orthogonal frequency division multiplexing signal separation circuit including a slab-type star coupler.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] According to conventional photonic computing technologies, optical computing circuits perform operations two bits at a time. To process a larger number of bits, multi-stage connection of optical computing circuits is required, but as the number of connected devices increases, the size, delay time, and power consumption increase. Therefore, it is required to process multiple bits without causing excessive increases in size, delay time, and power consumption.

[0007] An object of the present disclosure is to provide an optical arithmetic device that can calculate the exclusive logical sum of multi-bit input optical signals without causing excessive increases in size, delay time, and power consumption.

Means for Solving the Problems

[0008] The optical arithmetic device according to the first aspect of the present disclosure includes first and second star couplers each having N (N is a power of 2 and an integer of 4 or more) input ports and N output ports, N input optical waveguides each transmitting one of the N input optical signals, N splitters that generate N first intermediate optical signals and N second intermediate optical signals by splitting each of the N input optical signals into first and second intermediate optical signals, N first intermediate optical waveguides each transmitting one of the N first intermediate optical signals and inputting them to the N input ports of the first star coupler, N / 2 first phase shifters each inserted into N / 2 of the first intermediate optical waveguides and changing the phase of the first intermediate optical signal transmitted through the N / 2 first intermediate optical waveguides by 180 degrees, two first output optical waveguides each transmitting one of the two first output optical signals output from the two output ports of the first star coupler, N second intermediate optical waveguides each transmitting one of the N second intermediate optical signals and inputting them to the N input ports of the second star coupler, N / 2 second phase shifters each inserted into N / 2 of the second intermediate optical waveguides and changing the phase of the second intermediate optical signal transmitted through the N / 2 second intermediate optical waveguides by 180 degrees, two second output optical waveguides each transmitting one of the two second output optical signals output from the two output ports of the second star coupler, and an output circuit that calculates the exclusive logical sum of the N input optical signals by calculating the logical product of the two first output optical signals and the two second output optical signals and outputs the result. The first and second phase shifters are inserted into the first and second intermediate optical waveguides such that the first and second intermediate optical signals divided by N / 2 of the splitters have different phase shift amounts from each other.

[0009] According to the optical arithmetic device according to the second aspect of the present disclosure, in the optical arithmetic device according to the first aspect, Each of the first and second star couplers has an incident surface formed along an arc centered on a first point and having a predetermined radius, and an exit surface formed along an arc centered on a second point on the incident surface and having the predetermined radius, the first to Nth input ports among the N input ports are arranged in order on the incident surface, the first to Nth output ports among the N output ports are arranged in order on the exit surface corresponding to the first to Nth input ports respectively and symmetrically with respect to the first to Nth input ports with respect to the midpoint of the first and second points, the positions of the N input ports and the N output ports are based on the phase shift amount when an optical signal propagates over a distance equal to the predetermined radius in the first or second star coupler, and the relative phase shift amount φ(k, n) when an optical signal propagates from the kth input port to the nth output port (1 ≦ k ≦ N, 1 ≦ n ≦ N) is φ(k, n) = (2π / N)(k - (N + 1) / 2)(n - (N + 1) / 2) is set to satisfy the first and second intermediate optical signals input to the kth input port (1 ≦ k ≦ N) among the N input ports have a phase offset α(k) = (π / N)(N - 1)(k - 1).

[0010] According to the optical arithmetic device according to the third aspect of the present disclosure, in the optical arithmetic device according to the second aspect, The first N / 2 phase shifters are respectively inserted into the N / 2 first intermediate waveguides connected to half of the input ports having odd numbers and half of the input ports having even numbers among the first to Nth input ports of the first star coupler. The second N / 2 phase shifters are respectively inserted into the N / 2 second intermediate waveguides connected to half of the input ports having odd numbers and half of the input ports having even numbers among the first to Nth input ports of the second star coupler.

[0011] According to the optical arithmetic device according to the fourth aspect of the present disclosure, in the optical arithmetic device according to the third aspect, When N = 4, The first and second phase shifters The first intermediate optical signal input to the first input port of the first star coupler has a phase shift amount different from the phase shift amount of the second intermediate optical signal input to the first input port of the second star coupler, and the first intermediate optical signal input to the third input port of the first star coupler has a phase shift amount different from the phase shift amount of the second intermediate optical signal input to the third input port of the second star coupler, or The first intermediate optical signal input to the second input port of the first star coupler has a phase shift amount different from the phase shift amount of the second intermediate optical signal input to the second input port of the second star coupler, and the first intermediate optical signal input to the fourth input port of the first star coupler has a phase shift amount different from the phase shift amount of the second intermediate optical signal input to the fourth input port of the second star coupler, and are inserted into the first and second intermediate waveguides.

[0012] According to the optical arithmetic device according to the fifth aspect of the present disclosure, in the optical arithmetic device according to the third aspect, When N ≥ 8, The first and second phase shifters The first intermediate optical signal input to 1 / 4 of the input ports with odd numbers of the first star coupler has a phase shift of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with odd numbers of the second star coupler has a phase shift of π, and The first intermediate optical signal input to the other 1 / 4 of the input ports with odd numbers of the first star coupler has a phase shift of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with odd numbers of the second star coupler has a phase shift of 0, and The first intermediate optical signal input to yet another 1 / 4 of the input ports with odd numbers of the first star coupler has a phase shift of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with odd numbers of the second star coupler has a phase shift of π, and The first intermediate optical signal input to the remaining 1 / 4 of the input ports with odd numbers of the first star coupler has a phase shift of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with odd numbers of the second star coupler has a phase shift of 0, and The first intermediate optical signal input to 1 / 4 of the input ports with even numbers of the first star coupler has a phase shift of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with even numbers of the second star coupler has a phase shift of π, and The first intermediate optical signal input to the other 1 / 4 of the input ports with even numbers of the first star coupler has a phase shift of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with even numbers of the second star coupler has a phase shift of 0, and The first intermediate optical signal input to yet another 1 / 4 of the input ports with even numbers of the first star coupler has a phase shift of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports with even numbers of the second star coupler has a phase shift of π, and The first intermediate optical signal input to the remaining 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of 0, such that they are inserted into the first and second intermediate waveguides.

[0013] According to the optical computing device according to the sixth aspect of the present disclosure, in the optical computing device according to one of the second to fifth aspects, the first output waveguide transmits the first output optical signals output from the first output port and the (N / 2 + 1)-th output port of the first star coupler, and the second output waveguide transmits the second output optical signals output from the first output port and the (N / 2 + 1)-th output port of the second star coupler.

[0014] According to the optical computing device according to the seventh aspect of the present disclosure, in the optical computing device according to one of the first to sixth aspects, the output circuit includes four converters that respectively convert the two first output optical signals and the two second output optical signals into four electrical signals, and a logical product circuit that calculates the logical product of the four electrical signals.

[0015] The optical computing device according to the eighth aspect of the present disclosure includes a star coupler having four input ports and four output ports, four input waveguides that respectively transmit four input optical signals, two phase shifters that are respectively inserted into two of the input waveguides and change the phase of the input optical signals transmitted through the two input waveguides by 180 degrees, two output waveguides that respectively transmit two output optical signals output from two output ports of the star coupler, and an output circuit that calculates the exclusive logical sum of the four input optical signals by calculating the logical product of the two output optical signals and outputs the result.

Advantages of the Invention

[0016] According to one aspect of the present disclosure, it is possible to calculate the exclusive logical sum of multi-bit input optical signals without causing an excessive increase in size, delay time, and power consumption.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0018] Hereinafter, with reference to the drawings, an optical computing device according to each embodiment of the present disclosure will be described. Throughout the drawings, the same reference numerals denote the same components.

[0019] [First Embodiment] FIG. 1 is a diagram showing the configuration of an optical arithmetic device according to the first embodiment. The optical arithmetic device shown in FIG. 1 includes an optical arithmetic circuit 10 and an output circuit 20. The optical arithmetic device calculates and outputs the exclusive OR of 4-bit input optical signals.

[0020] The optical arithmetic circuit 10 includes input waveguides 30-1 to 30-4, splitters 11-1 to 11-4, intermediate waveguides 31-1 to 31-4, 32-1 to 32-4, phase shifters 12-1 to 12-4, star couplers 13-1, 13-2, and output waveguides 33-1, 33-2, 34-1, 34-2. Each component of the optical arithmetic circuit 10 is formed on an optical waveguide substrate.

[0021] The star couplers 13-1, 13-2 are slab-type star couplers formed on the optical waveguide substrate. Each of the star couplers 13-1, 13-2 has four input ports p1 to p4 and four output ports q1 to q4, respectively. Each of the star couplers 13-1, 13-2 performs a discrete Fourier transform on the four optical signals input from the input ports p1 to p4 and outputs the four optical signals from the output ports q1 to q4. In the example of FIG. 1, as will be described later, only the optical signals output from the output ports q1 and q3 among the output ports q1 to q4 are used.

[0022] The input waveguides 30-1 to 30-4 transmit each bit b1 to b4 of the input optical signal, respectively. The bits b1 to b4 are in-phase pulses with respect to each other, and their non-zero amplitude represents "1", and their zero amplitude represents "0".

[0023] The splitters 11-1 to 11-4 generate four first intermediate optical signals and four second intermediate optical signals by splitting each bit b1 to b4 of the input optical signal into first and second intermediate optical signals.

[0024] The intermediate waveguides 31-1 to 31-4 each transmit the first intermediate optical signal and input it into the input ports p4 to p1 of the star coupler 13-1, respectively. Two of the intermediate waveguides 31-1 to 31-4, in the example of FIG. 1, the intermediate waveguides 31-1 and 31-2, the phase shifters 12-1 and 12-2 are inserted respectively. The phase shifters 12-1 and 12-2 change the phase of the intermediate optical signal transmitted through the intermediate waveguides 31-1 and 31-2 by 180 degrees. The output waveguides 33-1 and 33-2 each transmit the two output optical signals output from the two output ports q1 and q3 of the star coupler 13-1.

[0025] The intermediate waveguides 32-1 to 32-4 each transmit the second intermediate optical signal and input it into the input ports p4 to p1 of the star coupler 13-2, respectively. Two of the intermediate waveguides 32-1 to 32-4, in the example of FIG. 1, the intermediate waveguides 32-1 and 32-4, the phase shifters 12-3 and 12-4 are inserted respectively. The phase shifters 12-3 and 12-4 change the phase of the intermediate optical signal transmitted through the intermediate waveguides 32-1 and 32-4 by 180 degrees. The output waveguides 34-1 and 34-2 each transmit the two output optical signals output from the two output ports q1 and q3 of the star coupler 13-2.

[0026] Thereby, the phase shifters 12-1 to 12-4 are inserted into the intermediate waveguides 31-1, 31-2, 32-1, and 32-4 so that the first and second intermediate optical signals divided by two of the splitters 11-1 to 11-4, in the example of FIG. 1, the splitters 11-2 and 11-4, have different phase shifts from each other.

[0027] The output circuit 20 includes converters 21-1 to 21-4 and an AND circuit 22. The four converters 21-1 to 21-4 convert the two output optical signals of the star coupler 13-1 and the two output optical signals of the star coupler 13-2 into four electrical signals b11 to b14, respectively. The AND circuit 22 calculates the logical product of the four electrical signals b11 to b14. Thereby, the output circuit 20 calculates the exclusive OR of the bits b1 to b4 of the input optical signal by calculating the logical product of the output optical signals of the star couplers 13-1 and 13-2 and outputs it as an output XOR value.

[0028] The lengths of the input waveguides 30-1 to 30-4 are equal to each other. Also, the lengths of the intermediate waveguides 31-1 to 31-4 and 32-1 to 32-4 are equal to each other. Further, the lengths of the output waveguides 33-1, 33-2, 34-1, and 34-2 are equal to each other. Note that, as will be described later, the lengths of the intermediate waveguides 31-1 to 31-4 and 32-1 to 32-4 may be different from each other in order to impart a phase offset to the intermediate optical signals input to the input ports p1 to p4 of each star coupler 13-1, 13-2.

[0029] In FIG. 1, the thick solid lines indicate the paths of the optical signals, and the thick dashed lines indicate the paths of the electrical signals.

[0030] FIG. 2 is a diagram for explaining the operation of the star couplers 13-1 and 13-2 in FIG. 1. In the example of FIG. 2, for the sake of explanation, a star coupler 13 having N (N is a power of 2 and an integer of 4 or more) input ports p1 to pN and N output ports q1 to qN is referred to.

[0031] In FIG. 2, reference numerals 41-1 to 41-N indicate intermediate waveguides, corresponding to the intermediate waveguides 31-1 to 31-4 or the intermediate waveguides 32-1 to 32-4 in FIG. 1. Also, reference numerals 42-1 to 42-N indicate output waveguides, corresponding to the output waveguides 33-1 to 33-4 or the output waveguides 34-1 to 34-4 in FIG. 1.

[0032] The star coupler 13 has an incident surface S1 formed along an arc centered on a first point P1 and having a predetermined radius R, and an exit surface S2 formed along an arc centered on a second point P2 on the incident surface S1 and having a radius R. The first to Nth input ports p1 to pN are arranged in order on the incident surface S1. The first to Nth output ports q1 to qN are arranged in order on the exit surface S2 corresponding to the first to Nth input ports p1 to pN respectively, and at positions symmetric to the first to Nth input ports p1 to pN with respect to the midpoint P3 of the first point P1 and the second point P2. The positions of the N input ports and the N output ports q1 to qN are based on the phase shift amount when an optical signal propagates over a distance equal to the radius R in the star coupler 13, such that the relative phase shift amount φ(k, n) from the kth input port pk to the nth output port qn (1 ≤ k ≤ N, 1 ≤ n ≤ N) satisfies the following equation.

[0033]

Equation

[0034] Also, the relative phase shift amount φ(k, n) satisfies the following equation.

[0035]

Equation

[0036] Here, n s is the refractive index of the optical waveguide substrate, λ is the wavelength of light, and D is the distance from the input port pk to the output port qn. θ n is the angle between the line passing through points P2 and P1 and the line passing through points P2 and the output port qn. ψ k is the angle between the line passing through points P1 and P2 and the line passing through points P1 and the input port pk.

[0037] The positions of the input ports p1 to pN and the output ports q1 to qN are set such that the left side of Equation (1) is equal to the left side of Equation (2).

[0038] Further, phase shifters 43-1 to 43-N are respectively inserted into the intermediate waveguides 41-1 to 41-N, whereby a phase offset α(k) = (π / N)(N - 1)(k - 1) is imparted to the intermediate optical signal input to the input port pk.

[0039] The phase offset may be imparted by, for example, changing the refractive index of the waveguide by increasing or decreasing the length of the waveguide, the thermo-optical effect, the electro-optical effect, ultraviolet light trimming, trimming using the photoelastic effect, and the like.

[0040] The phase difference Δφ between the optical signal propagating from the k-th input port pk to the n-th output port qn and the optical signal propagating from the (k + 1)-th input port p(k + 1) to the n-th output port qn is represented by Δφ = {φ(k + 1, n) + α(k + 1)} - {φ(k, n) + α(k)} = 2π(n - 1) / N. Therefore, when an optical signal I k (t) is input to the input port pk, the optical signal O n (t) output from the output port qn is represented by the following equation.

[0041] [Equation]

[0042] According to Equation (3), it can be seen that the output optical signal is the discrete Fourier transform of the input optical signal.

[0043] To the output port q1, the intermediate optical signals input to the input ports p1 to pN arrive in phase as they are. To the output port q(N / 2 + 1), the phases of the intermediate optical signals input to the input ports p1 to pN change by 180 degrees each and arrive.

[0044] Next, with reference to FIGS. 3 to 8, the operation of the optical arithmetic unit of FIG. 1 will be further described.

[0045] FIG. 3 is a table showing the operation of a first exemplary input optical signal by the optical arithmetic unit of FIG. 1. FIG. 3 shows a case where input optical signals (b1, b2, b3, b4) = (0, 0, 1, 1) are input to the optical computing device. As described above, the bit value "1" is represented by a pulse having a non-zero amplitude, and the bit value "0" is represented by a zero amplitude. The input optical signals of bits b3 and b4 are directly input to the input ports p2 and p1 of the star coupler 13-1. Also, the input optical signal of bit b3 is directly input to the input port p2 of the star coupler 13-2, and the input optical signal of bit b4 having a phase changed by 180 degrees by the phase shifter 12-4 is input to the input port p1 of the star coupler 13-2. The input optical signals input to the input ports p2 and p1 directly arrive at the output port q1 of each of the star couplers 13-1 and 13-2, and an output optical signal obtained by superimposing these input optical signals on each other is output. The input optical signals input to the input port p2 directly arrive at the output port q3 of each of the star couplers 13-1 and 13-2 with a phase changed by 180 degrees, and the input optical signals input to the input port p1 directly arrive, and an output optical signal obtained by superimposing these input optical signals on each other is output. The output optical signals output from the output port q1 of the star coupler 13-1 include components in the same phase with each other, and the converter 21-1 converts the output optical signal into an electrical signal b11 having a bit value "1". The output optical signals output from the output port q3 of the star coupler 13-1 include components in opposite phases with each other and cancel each other out, and the converter 21-2 converts the output optical signal into an electrical signal b12 having a bit value "0". The output optical signals output from the output port q1 of the star coupler 13-2 include components in opposite phases with each other and cancel each other out, and the converter 21-3 converts the output optical signal into an electrical signal b13 having a bit value "0". The output optical signals output from the output port q3 of the star coupler 13-2 include components in the same phase with each other, and the converter 21-4 converts the output optical signal into an electrical signal b14 having a bit value "1". By calculating the logical product of the bit values (1, 0, 0, 1) output from the converters 21-1 to 21-4, the exclusive OR "0" of the input optical signals (0, 0, 1, 1) is obtained.

[0046] FIG. 4 is a table showing the operation of a second exemplary input optical signal by the optical arithmetic unit of FIG. 1. FIG. 4 shows the case where an input optical signal (b1, b2, b3, b4) = (1, 1, 1, 0) is input to the optical arithmetic unit. Input optical signals of bits b1 and b2 having phases changed by 180 degrees by phase shifters 12-1 and 12-2 are input to input ports p4 and p3 of star coupler 13-1, respectively, and an input optical signal of bit b3 is input as it is to input port p2 of star coupler 13-1. An input optical signal of bit b1 having a phase changed by 180 degrees by phase shifter 12-1 is input to input port p4 of star coupler 13-2, and input optical signals of bits b2 and b3 are input as they are to input ports p3 and p2 of star coupler 13-2, respectively. Input optical signals input to input ports p4 to p2 arrive as they are at output port q1 of each of star couplers 13-1 and 13-2, and output optical signals obtained by superimposing these input optical signals on each other are output. Input optical signals input to input ports p4 and p2 arrive at output port q3 of each of star couplers 13-1 and 13-2 with a phase changed by 180 degrees, and an input optical signal input to input port p3 arrives as it is, and output optical signals obtained by superimposing these input optical signals on each other are output. The output optical signals output from output ports q1 and q3 of each of star couplers 13-1 and 13-2 partially cancel each other out, including a certain component, a component in phase therewith, and a component in antiphase, and converters 21-1 to 21-4 convert each output optical signal into electrical signals b11 to b14 having a bit value of "1", respectively. By calculating the logical product of the bit values (1, 1, 1, 1) output from converters 21-1 to 21-4, the exclusive OR "1" of the input optical signal (1, 1, 1, 0) is obtained.

[0047] Figures 5 to 8 are tables showing the operations by the optical arithmetic device of FIG. 1. Figures 5 to 8 show cases where input optical signals (0, 0, 0, 0) to (1, 1, 1, 1) are respectively input to the optical arithmetic device. "1(0)" indicates that the signal having the bit value "1" is in phase with the corresponding input optical signal, and "1(π)" indicates that the signal having the bit value "1" is out of phase with the corresponding input optical signal. Regarding the output optical signals at the output ports q1 and q3 of each star coupler 13-1 and 13-2, the thick frame line indicates that the bit value output from the converters 21-1 to 21-4 becomes "1", and the shaded area indicates that the bit value output from the converters 21-1 to 21-4 becomes "0". When the input optical signal has an even number of bit values "1", at least one of the output optical signals (especially when N = 4, at least two of the output optical signals) has a bit value "0" due to interference. In this case, the output XOR value becomes "0". When the input optical signal has an odd number of bit values "1", all the output optical signals have a bit value "1". In this case, the output XOR value becomes "1". Therefore, it can be seen that the optical arithmetic device of FIG. 1 correctly calculates the exclusive OR of the input optical signals.

[0048] According to the optical arithmetic device according to the first embodiment, without the need for multi-stage connection of optical arithmetic circuits, the exclusive OR of multi-bit input optical signals can be calculated by a relatively small-scale circuit.

[0049] Also, in the optical arithmetic circuit 10, signals are processed at the speed of light. Therefore, according to the optical arithmetic device according to the first embodiment, it can be calculated at a higher speed than when calculating the exclusive OR by an electric circuit, and the delay time due to the calculation can be shortened.

[0050] Also, according to the optical arithmetic device according to the first embodiment, since the circuit scale is small, it can operate with low power consumption.

[0051] Thus, according to the optical arithmetic device according to the first embodiment, the exclusive OR of 4-bit input optical signals can be calculated without causing an excessive increase in size, delay time, and power consumption.

[0052] Also, according to the optical computing device according to the first embodiment, as will be described later, an input optical signal including a larger number of bits than 4 bits can be processed in the same manner.

[0053] [First Modification Example] The phase shifters 12-1 to 12-4 are not limited to the arrangement in FIG. 1 and may have other arrangements. The phase shifters 12-1 and 12-2 are inserted into two of the intermediate waveguides 31-1 to 31-4 that are connected to one of the input ports p1 and p3 having odd numbers and one of the input ports p2 and p4 having even numbers among the first to fourth input ports p1 to p4 of the star coupler 13-1, respectively. The phase shifters 12-3 and 12-4 are inserted into two of the intermediate waveguides 32-1 to 32-4 that are connected to one of the input ports p1 and p3 having odd numbers and one of the input ports p2 and p4 having even numbers among the first to fourth input ports p1 to p4 of the star coupler 13-2, respectively. The phase shifters 12-1 to 12-4 are inserted into the intermediate waveguides 31-1 to 31-4 and 32-1 to 32-4 so as to satisfy either of the following conditions (1) and (2).

[0054] (1) The intermediate optical signal input to the input port p1 of the star coupler 13-1 has a phase shift amount different from that of the intermediate optical signal input to the input port p1 of the star coupler 13-2, and the intermediate optical signal input to the input port p3 of the star coupler 13-1 has a phase shift amount different from that of the intermediate optical signal input to the input port p3 of the star coupler 13-2. (2) The intermediate optical signal input to the input port p2 of the star coupler 13-1 has a phase shift amount different from that of the intermediate optical signal input to the input port p2 of the star coupler 13-2, and the intermediate optical signal input to the input port p4 of the star coupler 13-1 has a phase shift amount different from that of the intermediate optical signal input to the input port p4 of the star coupler 13-2.

[0055] By arranging the phase shifters 12-1 to 12-4 so as to satisfy these conditions, it is possible to calculate the exclusive logical sum of 4-bit input optical signals, similarly to the optical arithmetic unit of FIG. 1.

[0056] [Second Modification Example] The optical arithmetic unit according to the embodiment may process an input optical signal including a larger number of N bits (N is an integer that is a power of 2 and greater than 4) than 4 bits.

[0057] FIG. 9 is a diagram showing the configuration of the optical arithmetic circuit 10A of the optical arithmetic unit according to the first modification example of the first embodiment. The optical arithmetic circuit 10A processes an 8-bit input optical signal.

[0058] The optical arithmetic circuit 10A includes input waveguides 30-1 to 30-8, splitters 11-1 to 11-8, intermediate waveguides 31-1 to 31-8, 32-1 to 32-8, phase shifters 12-1 to 12-8, star couplers 13A-1, 13A-2, and output waveguides 33-1, 33-2, 34-1, 34-2. Each component of the optical arithmetic circuit 10A is formed on an optical waveguide substrate.

[0059] The star couplers 13A-1 and 13A-2 are slab-type star couplers formed on the optical waveguide substrate. Each of the star couplers 13A-1 and 13A-2 has eight input ports p1 to p8 and eight output ports q1 to q8, respectively. Each of the star couplers 13A-1 and 13A-2 performs a discrete Fourier transform on the eight optical signals input from the input ports p1 to p8 and outputs the eight optical signals from the output ports q1 to q8. In the example of FIG. 9, as will be described later, only the optical signals output from the output ports q1 and q5 among the output ports q1 to q8 are used.

[0060] The input waveguides 30-1 to 30-8 transmit each bit b1 to b8 of the input optical signal. The bits b1 to b8 are pulses in the same phase with each other.

[0061] The splitters 11-1 to 11-8 generate eight first intermediate optical signals and eight second intermediate optical signals by splitting each bit b1 to b8 of the input optical signal into the first and second intermediate optical signals.

[0062] The intermediate waveguides 31-1 to 31-8 respectively transmit the first intermediate optical signals and input them into the input ports p8 to p1 of the star coupler 13A-1. Four of the intermediate waveguides 31-1 to 31-8, in the example of FIG. 9, the intermediate waveguides 31-3 to 31-6, have phase shifters 12-1 to 12-4 respectively inserted therein. The phase shifters 12-1 to 12-4 change the phase of the intermediate optical signal transmitted through the intermediate waveguides 31-3 to 31-6 by 180 degrees. The output waveguides 33-1 and 33-2 respectively transmit the two output optical signals output from the two output ports q1 and q5 of the star coupler 13A-1.

[0063] The intermediate waveguides 32-1 to 32-8 respectively transmit the second intermediate optical signals and input them into the input ports p8 to p1 of the star coupler 13A-2. Four of the intermediate waveguides 32-1 to 32-8, in the example of FIG. 9, the intermediate waveguides 32-1, 32-4, 32-5, and 32-8, have phase shifters 12-5 to 12-8 respectively inserted therein. The phase shifters 12-5 to 12-8 change the phase of the intermediate optical signal transmitted through the intermediate waveguides 32-1, 32-4, 32-5, and 32-8 by 180 degrees. The output waveguides 34-1 and 34-2 respectively transmit the two output optical signals output from the two output ports q1 and q5 of the star coupler 13A-2.

[0064] Accordingly, the phase shifters 12-1 to 12-8 are inserted into the intermediate waveguides 31-3 to 31-6, 32-1, 32-4, 32-5, and 32-8 such that the first and second intermediate optical signals split by four of the splitters 11-1 to 11-8, in the example of FIG. 9, the splitters 11-1, 11-3, 11-6, and 11-8, have different phase shift amounts from each other.

[0065] The lengths of the input waveguides 30-1 to 30-8 are equal to each other. Also, the lengths of the intermediate waveguides 31-1 to 31-8 and 32-1 to 32-8 are equal to each other. Further, the lengths of the output waveguides 33-1, 33-2, 34-1, and 34-2 are equal to each other.

[0066] The two output optical signals of the star coupler 13A-1 and the two output optical signals of the star coupler 13A-2 are sent to the output circuit 20 of FIG. 1. The output circuit 20 calculates the exclusive logical sum of the input optical signal bits b1 to b8 by calculating the logical product of the output optical signals of the star couplers 13A-1 and 13A-2 and outputs it as the output XOR value.

[0067] The optical computing device including the optical computing circuit 10A of FIG. 9 can calculate the exclusive logical sum of 8-bit input optical signals without causing an excessive increase in size, delay time, and power consumption, similar to the optical computing device of FIG. 1.

[0068] [Third Modification Example] FIG. 10 is a diagram showing the configuration of the optical computing circuit 10B of the optical computing device according to the second modification example of the first embodiment. In the optical computing circuit 10B, the phase shifters 12-1 to 12-8 are inserted into intermediate waveguides different from those in the case of FIG. 9 among the intermediate waveguides 31-1 to 31-8 and 32-1 to 32-8.

[0069] Four of the intermediate waveguides 31-1 to 31-8, in the example of FIG. 10, the phase shifters 12-1 to 12-4 are respectively inserted into the intermediate waveguides 31-1 to 31-4. The phase shifters 12-1 to 12-4 change the phase of the intermediate optical signal transmitted through the intermediate waveguides 31-1 to 31-4 by 180 degrees.

[0070] Four of the intermediate waveguides 32-1 to 32-8, in the example of FIG. 10, the phase shifters 12-5 to 12-8 are respectively inserted into the intermediate waveguides 32-1, 32-2, 32-7, and 32-8. The phase shifters 12-5 to 12-8 change the phase of the intermediate optical signal transmitted through the intermediate waveguides 32-1, 32-2, 32-7, and 32-8 by 180 degrees.

[0071] As a result, the phase shifters 12-1 to 12-8 are inserted into the intermediate waveguides 31-1 to 31-4, 32-1, 32-2, 32-7, 32-8 so that the first and second intermediate optical signals divided by four of the splitters 11-1 to 11-8, in the example of FIG. 10, the splitters 11-3, 11-4, 11-7, 11-8 have different phase shift amounts from each other.

[0072] The optical computing device including the optical computing circuit 10B in FIG. 10 can compute the exclusive OR of 8-bit input optical signals, similar to the optical computing device including the optical computing circuit 10A in FIG. 9.

[0073] [Fourth Modification Example] The optical computing device according to the embodiment may be configured to process input optical signals of 8 bits or more. When N is an integer that is a power of 2 and 8 or more, the optical computing device includes first and second star couplers, N input waveguides, N splitters, N first intermediate waveguides, N / 2 first phase shifters, two first output waveguides, N second intermediate waveguides, N / 2 second phase shifters, two second output waveguides, and an output circuit.

[0074] The first and second star couplers each have N input ports and N output ports.

[0075] The N input waveguides each transmit N input optical signals.

[0076] The N splitters generate N first intermediate optical signals and N second intermediate optical signals by dividing each of the N input optical signals into first and second intermediate optical signals.

[0077] N first intermediate waveguides each transmit N first intermediate optical signals and input them into N input ports of a first star coupler respectively. N / 2 first phase shifters are respectively inserted into N / 2 of the first intermediate waveguides to change the phase of the first intermediate optical signals transmitted through the N / 2 first intermediate waveguides by 180 degrees. Two first output waveguides respectively transmit two first output optical signals output from two output ports of the first star coupler.

[0078] N second intermediate waveguides each transmit N second intermediate optical signals and input them into N input ports of a second star coupler respectively. N / 2 second phase shifters are respectively inserted into N / 2 of the second intermediate waveguides to change the phase of the second intermediate optical signals transmitted through the N / 2 second intermediate waveguides by 180 degrees. Two second output waveguides respectively transmit two second output optical signals output from two output ports of the second star coupler.

[0079] The output circuit calculates the exclusive OR of N input optical signals by calculating the logical product of two first output optical signals and two second output optical signals and outputs the result.

[0080] The first and second phase shifters are inserted into the first and second intermediate waveguides such that the first and second intermediate optical signals divided by N / 2 of the splitters have different phase shift amounts.

[0081] N / 2 first phase shifters are respectively inserted into N / 2 first intermediate waveguides connected to half of the input ports with odd numbers and half of the input ports with even numbers among the first to Nth input ports of the first star coupler. N / 2 second phase shifters are respectively inserted into N / 2 second intermediate waveguides connected to half of the input ports with odd numbers and half of the input ports with even numbers among the first to Nth input ports of the second star coupler.

[0082] The first and second phase shifters are inserted into the first and second intermediate waveguides so as to further satisfy all of the following conditions (1) to (8).

[0083] (1) The first intermediate optical signal input to 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of π. (2) The first intermediate optical signal input to the other 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of 0. (3) The first intermediate optical signal input to yet another 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of π. (4) The first intermediate optical signal input to the remaining 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of 0. (5) The first intermediate optical signal input to 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of π. (6) The first intermediate optical signal input to the other 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of 0. (7) The first intermediate optical signal input to yet another 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of π. (8) The first intermediate optical signal input to the remaining 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of 0.

[0084] The first output waveguide transmits the first output optical signal output from the first output port and the (N / 2 + 1)-th output port of the first star coupler. The second output waveguide transmits the second output optical signal output from the first output port and the (N / 2 + 1)-th output port of the second star coupler.

[0085] Thus, even when the input optical signal has a number of bits that is a power of 2 and 8 or more, the exclusive logical sum of a multi-bit input optical signal can be calculated without causing an excessive increase in size, delay time, and power consumption.

[0086] [Second Embodiment] FIG. 11 is a diagram showing the configuration of an optical arithmetic device according to the second embodiment. When the input optical signal is 4 bits, the configuration of the optical arithmetic device can be simplified compared to the case of FIG. 1.

[0087] The optical arithmetic device in FIG. 11 includes an optical arithmetic circuit 10C and an output circuit 20C.

[0088] The optical arithmetic circuit 10C includes a star coupler 13, four input waveguides 30C-1 to 30C-4, two phase shifters 12-1 and 12-2, and two output waveguides 33-1 and 33-2. The star coupler 13 has four input ports p1 to p4 and four output ports q1 to q4. The four input waveguides 30C-1 to 30C-4 transmit each bit b1 to b4 of the input optical signal. Two of the input waveguides 30C-1 to 30C-4, in the example of FIG. 11, the input waveguides 30C-1 and 30C-2, the phase shifters 12-1 and 12-2 are respectively inserted. The phase shifters 12-1 and 12-2 change the phase of the input optical signal transmitted through the input waveguides 30C-1 and 30C-2 by 180 degrees. The two output waveguides 33-1 and 33-2 transmit the two output optical signals output from the two output ports q1 and q3 of the star coupler respectively.

[0089] The output circuit 20C includes converters 21-1 and 21-2 and a logical product circuit 22. The two converters 21-1 and 21-2 respectively convert the two output optical signals of the star coupler 13 into two electrical signals b11 and b12. The logical product circuit 22 calculates the logical product of the two electrical signals b11 and b12. Thereby, the output circuit 20C calculates the exclusive OR of the bits b1 to b4 of the input optical signal by calculating the logical product of the output optical signals of the star coupler 13 and outputs it as an output XOR value.

[0090] In FIG. 11, the thick solid line indicates the path of the optical signal, and the thick dashed line indicates the path of the electrical signal.

[0091] The phase shifters 12-1 and 12-2 are not limited to the arrangement in FIG. 11 and may have other arrangements. The phase shifters 12-1 and 12-2 may be respectively inserted into two of the input waveguides 30C-1 to 30C-4 connected to one of the input ports p1 and p3 having odd numbers and one of the input ports p2 and p4 having even numbers among the first to fourth input ports p1 to p4 of the star coupler 13.

[0092] According to the optical arithmetic unit according to the second embodiment, similar to the optical arithmetic unit according to the first embodiment, it is possible to calculate the exclusive logical sum of 4-bit input optical signals without causing an excessive increase in size, delay time, and power consumption.

[0093] [Other Embodiments] The optical arithmetic unit according to the embodiment is applicable to, for example, signal encryption and decryption, pseudo-random number generation, signal error detection, and the like. By calculating the exclusive logical sum of multiple bits, the security of these processes can be improved.

[0094] By combining a plurality of optical arithmetic units (XOR circuits), an arbitrary logic circuit may be configured.

Industrial Applicability

[0095] The optical arithmetic unit according to one aspect of the present disclosure is applicable to the field of photonic computing, particularly the field of optoelectronic integrated logic circuits.

Explanation of Signs

[0096] 10, 10A~10C Optical arithmetic circuit 11-1~11-8 Divider 12-1~12-8 Phase shifter 13, 13-1, 13-2, 13A-1, 13A-2 Star coupler 20, 20C Output circuit 21-1~21-4 Converter 22, 22C AND circuit 30-1~30-8, 30C-1~30C-4 Input waveguide 31-1~31-8, 32-1~32-8 Intermediate waveguide 33-1, 33-2, 34-1, 34-2 Output waveguide 41-1~41-N Intermediate waveguide 42-1~42-N Output waveguide 43-1~43-N Phase shifter

Claims

1. first and second star couplers each having N input ports (where N is an integer that is a power of 2 and 4 or more) and N output ports, N input waveguides each transmitting one of the N input optical signals, N splitters that generate N first intermediate optical signals and N second intermediate optical signals by splitting each of the N input optical signals into first and second intermediate optical signals, N first intermediate waveguides each transmitting one of the N first intermediate optical signals and inputting them to the N input ports of the first star coupler, N / 2 first phase shifters each inserted into N / 2 of the first intermediate waveguides and changing the phase of the first intermediate optical signal transmitted through the N / 2 first intermediate waveguides by 180 degrees, two first output waveguides each transmitting one of the two first output optical signals output from the two output ports of the first star coupler, N second intermediate waveguides each transmitting one of the N second intermediate optical signals and inputting them to the N input ports of the second star coupler, N / 2 second phase shifters each inserted into N / 2 of the second intermediate waveguides and changing the phase of the second intermediate optical signal transmitted through the N / 2 second intermediate waveguides by 180 degrees, two second output waveguides each transmitting one of the two second output optical signals output from the two output ports of the second star coupler, an output circuit that calculates the exclusive OR of the N input optical signals by calculating the logical product of the two first output optical signals and the two second output optical signals and outputs the result, wherein the first and second phase shifters are inserted into the first and second intermediate waveguides such that the first and second intermediate optical signals split by N / 2 of the splitters have different phase shift amounts, an optical arithmetic device.

2. each of the first and second star couplers has an incident surface formed along an arc centered on a first point and having a predetermined radius, and an exit surface formed along an arc centered on a second point on the incident surface and having the predetermined radius, wherein the first to Nth input ports among the N input ports are arranged in order on the incident surface, Of the N output ports, the first to Nth output ports are arranged in order at positions on the emission surface that respectively correspond to the first to Nth input ports and are symmetric with respect to the first to Nth input ports with respect to the midpoint between the first and second points. The positions of the N input ports and the N output ports are based on the phase shift amount when an optical signal propagates over a distance equal to the predetermined radius in the first or second star coupler. When an optical signal propagates from the kth input port to the nth output port (1 ≤ k ≤ N, 1 ≤ n ≤ N), the relative phase shift amount φ(k, n) is φ(k, n) = (2π / N)(k - (N + 1) / 2)(n - (N + 1) / 2) set so as to satisfy The first and second intermediate optical signals input to the kth input port (1 ≤ k ≤ N) among the N input ports have a phase offset α(k) = (π / N)(N - 1)(k - 1). The optical computing device according to claim 1.

3. The N / 2 first phase shifters are respectively inserted into the N / 2 first intermediate waveguides connected to half of the input ports having odd numbers and half of the input ports having even numbers among the first to Nth input ports of the first star coupler. The N / 2 second phase shifters are respectively inserted into the N / 2 second intermediate waveguides connected to half of the input ports having odd numbers and half of the input ports having even numbers among the first to Nth input ports of the second star coupler. The optical computing device according to claim 2.

4. When N = 4, the first and second phase shifters are such that the first intermediate optical signal input to the first input port of the first star coupler has a phase shift amount different from that of the second intermediate optical signal input to the first input port of the second star coupler, and the first intermediate optical signal input to the third input port of the first star coupler has a phase shift amount different from that of the second intermediate optical signal input to the third input port of the second star coupler, or The first intermediate optical signal input to the second input port of the first star coupler has a phase shift amount different from that of the second intermediate optical signal input to the second input port of the second star coupler, and the first intermediate optical signal input to the fourth input port of the first star coupler has a phase shift amount different from that of the second intermediate optical signal input to the fourth input port of the second star coupler, such that inserted into the first and second intermediate optical waveguides The optical arithmetic device according to claim 3.

5. When N≥8 The first and second phase shifters The first intermediate optical signal input to 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of π, and The first intermediate optical signal input to the other 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of 0, and The first intermediate optical signal input to still another 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of π, and The first intermediate optical signal input to the remaining 1 / 4 of the input ports having odd numbers of the first star coupler has a phase shift amount of 0, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having odd numbers of the second star coupler has a phase shift amount of 0, and The first intermediate optical signal input to 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of π, and The first intermediate optical signal input to the other 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of π, and the second intermediate optical signal input to the corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of 0, and A first intermediate optical signal input to yet another 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of 0, and a second intermediate optical signal input to a corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of π, and a first intermediate optical signal input to the remaining 1 / 4 of the input ports having even numbers of the first star coupler has a phase shift amount of 0, and a second intermediate optical signal input to a corresponding 1 / 4 of the input ports having even numbers of the second star coupler has a phase shift amount of 0, inserted into the first and second intermediate waveguides, The optical arithmetic device according to claim 3.

6. The first output waveguide transmits the first output optical signals output from the first output port and the (N / 2 + 1)-th output port of the first star coupler, The second output waveguide transmits the second output optical signals output from the first output port and the (N / 2 + 1)-th output port of the second star coupler, The optical arithmetic device according to any one of claims 2 to 5.

7. The output circuit includes four converters that respectively convert the two first output optical signals and the two second output optical signals into four electrical signals, and a logical product circuit that calculates the logical product of the four electrical signals. The optical arithmetic device according to claim 1.

8. A star coupler having four input ports and four output ports, Four input waveguides that respectively transmit four input optical signals, Two phase shifters inserted into two of the input waveguides respectively, which change the phase of the input optical signals transmitted through the two input waveguides by 180 degrees, Two output waveguides that respectively transmit two output optical signals output from two output ports of the star coupler, and an output circuit that calculates the exclusive logical sum of the four input optical signals by calculating the logical product of the two output optical signals and outputs the result. Optical arithmetic device.

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