90-degree optical hybrid, and optical decoding device

Abstract

To provide a 90-degree optical hybrid capable of reducing loss of light intensity than before.SOLUTION: A 90-degree optical hybrid 100 includes: four input ports; an optical coupler 150; and four output ports 160, 170, 180, and 190. The four input ports include two inner input ports 120 and 130 and two outer input ports 110, and 140. Four input ports are configured so as to be capable of inputting first signal light, local oscillation light, and second signal light. The optical coupler is placed between the four input ports and the four output ports and connected to the four input ports and the four output ports. The optical coupler generates complex signal light based on the first signal light, the local oscillation light, and the second signal light. The first output port as one of the four output ports outputs the complex signal light in which loss relative to the total optical power input to the four input ports is 0 to 1.3 dB.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a 90-degree optical hybrid and an optical decoding device. [Background technology]

[0002] Patent Document 1 discloses a 90-degree optical hybrid.

[0003] This 90-degree optical hybrid will be described below. On each of the TE optical signal side and the TM optical signal side, an optical path length difference is provided between a pair of a signal optical waveguide arm and a local oscillator optical waveguide arm on either the I-phase side or the Q-phase side, and an inter-phase phase difference is provided between the I-phase side signal and the Q-phase side signal, and the output phase difference, which is the sum of the phase difference between the output interference characteristics of the I-phase side coupler and the Q-phase side coupler, and the inter-phase phase difference, is set to π / 2, so that the output signals of the eight output ports are arranged from the top in the order of Ip, In, Qp, Qn on the TE optical signal side and Ip, In, Qp, Qn on the TM optical signal side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-197433 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the loss of conventional 90-degree optical hybrids, such as the 90-degree optical hybrid disclosed in Patent Document 1, was 3 dB including the interference effect with local oscillator light. Therefore, a technology to reduce the loss of 90-degree optical hybrids was required.

[0006] In view of the above circumstances, the present invention provides a 90-degree optical hybrid or the like that can reduce the loss of optical intensity more than ever before. [Means for solving the problem]

[0007] According to one aspect of the present invention, a 90-degree optical hybrid is provided. The 90-degree optical hybrid includes four input ports, an optical coupler, and four output ports. The four input ports include two inner input ports adjacent to each other, and two outer input ports provided outside the two inner input ports and adjacent to the two inner input ports, respectively. The four input ports are configured to be able to input a first signal light, a local oscillator light, and a second signal light. The first signal light is a signal light that has been quadrature phase-shift keyed. The phase of the local oscillator light is π / 4 or 5π / 4. The second signal light is a signal light that has a predetermined relationship with the first signal light. The electric field intensities of the first signal light, the local oscillator light, and the second signal light are each the same. The first signal light is input to the first inner input port or the first outer input port. The first inner input port is one of the two inner input ports. The first outer input port is one of the two outer input ports. The local oscillator light is input to one of the first inner input port and the first outer input port, which is different from the port to which the first signal light is input. The second signal light is input to at least one of the second inner input port and the second outer input port. The second inner input port is a port of the two inner input ports that is different from the first inner input port. The second outer input port is a port of the two outer input ports that is different from the first outer input port. The optical coupler is provided between the four input ports and the four output ports, and is connected to the four input ports and the four output ports. The optical coupler generates complex signal light based on the first signal light, the local oscillator light, and the second signal light. The first output port, which is one of the four output ports, outputs complex signal light having a loss of 0 to 1.3 dB with respect to the total value of the optical intensity of the light input to the four input ports.

[0008] According to this embodiment, the loss of light intensity can be reduced more than ever before. [Brief description of the drawings]

[0009] [Figure 1]1 is a diagram showing an example of the configuration of an information processing system including a 90-degree optical hybrid 100 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating a hardware configuration of a 90-degree optical hybrid 100. [Diagram 3] 1 is a diagram showing a constellation when a first signal light, a local oscillator light, and a second signal light are input to a 90-degree optical hybrid 100. FIG. [Figure 4] FIG. 2 is a diagram showing the light intensity distribution in the 90-degree optical hybrid 100. [Diagram 5] FIG. 11 is a diagram showing the optical intensity at each output port relative to the phase of the locally-oscillated light. [Figure 6] 1 is a diagram showing a constellation when a first signal light, a local oscillator light, and a second signal light are input to a 90-degree optical hybrid 100. FIG. [Figure 7] FIG. 2 is a diagram showing the light intensity distribution in the 90-degree optical hybrid 100. [Figure 8] 1 is a diagram showing a constellation when a first signal light, a local oscillator light, and two second signal lights are input to a 90-degree optical hybrid 100. FIG. [Figure 9] FIG. 2 is a diagram showing the light intensity distribution in the 90-degree optical hybrid 100. [Figure 10] FIG. 13 is a diagram illustrating an example of the configuration of an information processing system including an optical decoding device 400 according to a second embodiment of the present invention. [Figure 11] FIG. 4 is a diagram showing a hardware configuration of an optical decoding device 400. [Figure 12] 13 is a diagram showing a constellation when a third signal light, a probe light, and a fourth signal light are input to an optical decoding device 400. FIG. [Figure 13] 13 is a diagram showing a light intensity distribution in the optical decoding device 400. FIG. [Figure 14] 13 is a diagram showing a constellation when a third signal light, a probe light, a fourth signal light, and a sum frequency light are input to an optical decoding device 400. FIG. [Figure 15] 13 is a diagram showing a light intensity distribution in the optical decoding device 400. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 1. First embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Various characteristic features shown in the following embodiments can be combined with each other.

[0011] Incidentally, the program for realizing the software appearing in this embodiment may be provided as a non-temporary computer-readable recording medium, or may be provided so as to be downloadable from an external server, or may be provided so that the program is started on an external computer and its functions are realized on a client terminal (so-called cloud computing).

[0012] In addition, in this embodiment, the term "unit" may include, for example, a combination of hardware resources implemented by a circuit in the broad sense and software information processing that can be specifically realized by these hardware resources. In addition, in this embodiment, various information is handled, and this information is represented, for example, by physical values ​​of signal values ​​representing voltage and current, high and low signal values ​​as a binary bit collection consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculation can be performed on the circuit in the broad sense.

[0013] In addition, a circuit in the broad sense is a circuit realized by at least appropriately combining a circuit, circuitry, a processor, a memory, etc. In other words, it includes an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)), etc.

[0014] 1-1. Overall structure Fig. 1 is a diagram showing an example of the configuration of an information processing system including a 90-degree optical hybrid 100 according to an embodiment of the present invention. As shown in Fig. 1, the 90-degree optical hybrid 100 is disposed between an optical processing system 200 and an electrical processing system 300, and decodes a signal input from the optical processing system 200 and outputs the decoded signal to the electrical processing system 300. In addition, a signal is transmitted from the electrical processing system 300 to the optical processing system 200 via an optical encoding device (not shown) or the like.

[0015] 1-2.90 Degree Optical Hybrid 100 2 is a diagram showing a hardware configuration of the 90-degree optical hybrid 100. The 90-degree optical hybrid 100 includes four input ports (input port 110, input port 120, input port 130, and input port 140), an optical coupler 150, and four output ports (output port 160, output port 170, output port 180, and output port 190).

[0016] Here, the four input ports include two inner input ports (input port 120 and input port 130) adjacent to each other, and two outer input ports (input port 110 and input port 140) that are provided outside the two inner input ports and adjacent to the two inner input ports, respectively. The optical coupler 150 may be, for example, a multimode interferometer (MMI) or a Mach-Zehnder interferometer (MZI), and in particular, in this embodiment, a 4:4 MMI is used.

[0017] The 90-degree optical hybrid 100 is used in a digital coherent system suitable for long-distance transmission and large-capacity transmission. In the digital coherent system, a first signal light, which is a signal light modulated by Quadrature Phase Shift Keying (QPSK), a locally-oscillated light, and a second signal light are input to the 90-degree optical hybrid 100. The first signal light, the locally-oscillated light, and the second signal light will be described in detail later.

[0018] That is, the first signal light, the local oscillator light, and the second signal light are each input to one of four input ports (input port 110, input port 120, input port 130, and input port 140). The optical coupler 150 is provided between the four input ports (input port 110, input port 120, input port 130, and input port 140) and four output ports (output port 160, output port 170, output port 180, and output port 190) and is connected to the four input ports and the four output ports. Then, the optical coupler 150 causes interference between the first signal light, the local oscillator light, and the second signal light, and distributes the interference to four output ports (output port 160, output port 170, output port 180, and output port 190). That is, the optical coupler 150 generates a complex signal light based on the first signal light, the local oscillator light, and the second signal light.

[0019] Here, a description will be given of the phase of light at output port 160, output port 170, output port 180, and output port 190 when input light (first signal light or local oscillator light) is input to each of input port 110, input port 120, input port 130, and input port 140. In the description of Section 1-2, the phase of the input light is set to 0.

[0020] The phases of the complex signal light at output port 160, output port 170, output port 180, and output port 190 relative to the phase of the input light incident on input port 110 are 0, 3π / 4, -π / 4, and 0, respectively. The phases of the complex signal light at output port 160, output port 170, output port 180, and output port 190 relative to input port 120 are 3π / 4, 0, 0, and -π / 4, respectively. The phases of the complex signal light at output port 160, output port 170, output port 180, and output port 190 relative to input port 130 are -π / 4, 0, 0, and 3π / 4, respectively. The phases of the complex signal light at output port 160, output port 170, output port 180, and output port 190 relative to input port 140 are 0, -π / 4, 3π / 4, and 0, respectively.

[0021] The electric field amplitudes of the input light input to input port 110, input port 120, input port 130, and input port 140 are I1, I2, I3, and I4, respectively, and the electric field amplitudes of the complex signal lights output from output port 160, output port 170, output port 180, and output port 190 are O1, O2, O3, and O4, respectively. The above relationship is expressed by using a matrix as shown in the following equation (1).

[0022]

number

[0023] Here, when input light is input to two input ports (for example, input port 110 and input port 130) that are asymmetrically positioned with respect to the center position in the width direction of the input end, the phase differences at output port 160, output port 170, output port 180, and output port 190 are π / 4, -3π / 4, π / 4, and -3π / 4, respectively. In the output channel in which output port 160 and output port 190 are paired, the phase difference is π, and the input light interferes in anti-phase. In the output channel in which output port 170 and output port 180 are paired, the phase difference is also π, and the input light interferes in anti-phase. However, in the latter output channel, the phase differs from that of the former output channel by π / 2. Therefore, the characteristics of a 90-degree optical hybrid are obtained.

[0024] For example, in equation (1), the first signal light E S , local oscillator light E is input to input port 130. L , a second signal light E S † When is input, it is expressed as the following equation (2).

[0025]

number

[0026] 1-3. Optical interference method 3 is a diagram showing a constellation when the first signal light, the local oscillator light, and the second signal light are input to the 90-degree optical hybrid 100. The four input ports (input port 110, input port 120, input port 130, and input port 140) are configured to be able to input the first signal light, the local oscillator light, and the second signal light. The first signal light is a signal light that has been quadrature phase shift modulated. The phase of the local oscillator light is assumed to be π / 4. The second signal light is a phase conjugate light that is in a phase conjugate relationship with the first signal light. The electric field intensities of the first signal light, the local oscillator light, and the second signal light are assumed to be the same.

[0027] Referring to FIG. 3, E S The first signal light, E L is the local oscillator light, E S † is defined as phase conjugate light. The first signal light is input to input port 110 (first outer input port), the local oscillator light is input to input port 130 (first inner input port), and the phase conjugate light is input to input port 140 (second outer input port).

[0028] 3(a) shows a case where the phase of the first signal light is 0. As a result, the output port 160 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4). The output port 170 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 180 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 190 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4).

[0029] 3(b) shows the case where the phase of the first signal light is π / 2. As a result, the output port 160 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 170 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 180 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4). The output port 190 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4).

[0030] 3(c) shows the case where the phase of the first signal light is π. As a result, the output port 160 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 170 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 180 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 190 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4).

[0031] 3(d) shows the case where the phase of the first signal light is 3π / 2. As a result, the output port 160 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 170 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4). The output port 180 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 190 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4).

[0032] That is, the first output port, which is one of the four output ports, outputs a complex signal light with a loss reduced to 1.3 dB relative to the total optical intensity of the light input to the four input ports.

[0033] FIG. 4 is a diagram showing the optical intensity distribution in the 90-degree optical hybrid 100. The optical intensity distribution in FIG. 4 was measured under the same conditions as those in FIG. 3. As shown in FIG. 4, it was found that when the phase of the first signal light is 0, strong light is output from the output port 160. Similarly, it was found that when the phase of the first signal light is π / 2, strong light is output from the output port 180. It was also found that when the phase of the first signal light is π, strong light is output from the output port 190. It was also found that when the phase of the first signal light is 3π / 2, strong light is output from the output port 170.

[0034] Alternatively, the first signal light may be input to the input port 140, and the phase conjugate light may be input to the input port 110. Alternatively, the local oscillator light may be input to the input port 120. Furthermore, when the local oscillator light is input to the input port 110 or the input port 140, the first signal light and the phase conjugate light may be input to the input port 120 or the input port 130, respectively.

[0035] That is, the first signal light is input to the first inner input port or the first outer input port. Here, the first inner input port is one of the two inner input ports. Also, the first outer input port is one of the two outer input ports.

[0036] The phase of the locally oscillated light may be 5π / 4. The locally oscillated light is input to one of the first inner input port and the first outer input port, which is different from the port to which the first signal light is input.

[0037] When the first signal light is input to the first inner input port, the phase conjugate light is input to the second inner input port. Also, when the first signal light is input to the first outer input port, the phase conjugate light is input to the second outer input port. That is, the phase conjugate light (second signal light) is input to at least one of the second inner input port and the second outer input port. Here, the second inner input port is a port of the two inner input ports that is different from the first inner input port. Also, the second outer input port is a port of the two outer input ports that is different from the first outer input port.

[0038] According to this embodiment, by additionally inputting signal light having a phase conjugate relationship, it is possible to reduce the loss of light intensity compared to the conventional art.

[0039] 1-4. Effect Fig. 5 is a diagram showing the optical intensity at each output port relative to the phase of the local oscillator light. As shown in Fig. 5(a), when the phase of the first signal light is 0, the optical intensity is maximum at output port 160 when the phase of the local oscillator light is π / 4, and when the phase of the local oscillator light is 5π / 4, the optical intensity is maximum at output port 190. As shown in Fig. 5(b), when the phase of the first signal light is π / 2, the optical intensity is maximum at output port 180 when the phase of the local oscillator light is π / 4, and when the phase of the local oscillator light is 5π / 4, the optical intensity is maximum at output port 170.

[0040] As shown in Fig. 5(c), when the phase of the first signal light is π, the optical intensity is maximum at output port 190 when the phase of the local oscillator light is π / 4, and when the phase of the local oscillator light is 5π / 4, the optical intensity is maximum at output port 160. As shown in Fig. 5(d), when the phase of the first signal light is 3π / 2, the optical intensity is maximum at output port 170 when the phase of the local oscillator light is π / 4, and the optical intensity is maximum at output port 180 when the phase of the local oscillator light is 5π / 4.

[0041] Due to the above-mentioned action, the loss in the 90-degree optical hybrid 100 can be reduced to 1.3 dB or less, whereas the loss in the conventional 90-degree optical hybrid was 3 dB including the effect of interference with the locally-oscillated light.

[0042] 2. Modification 1 of the First Embodiment Section 2 describes Modification 1 of the first embodiment. In Modification 1, descriptions that overlap with the description of the first embodiment will be omitted.

[0043] 6 is a diagram showing a constellation when the first signal light, the local oscillator light, and the second signal light are input to the 90-degree optical hybrid 100. Here, the second signal light is high-frequency light, and is a signal light having a phase twice as high as that of the first signal light. The high-frequency light is generated, for example, by inputting the first signal light to a nonlinear optical crystal and interacting with the crystal. The phase shift of the high-frequency light is assumed to be 5π / 4. The high-frequency light is phase-shifted, for example, by a known phase shifter.

[0044] Referring to FIG. 6, E S The first signal light, E L is the local oscillator light, E S (2) is high frequency light. The first signal light is input to the input port 110 (first outer input port), the local oscillator light is input to the input port 130 (first inner input port), and the high frequency light is input to the input port 120 (second inner input port).

[0045] 6(a) shows a case where the phase of the first signal light is 0. As a result, the output port 160 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4). The output port 170 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 180 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 190 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4).

[0046] 6(b) shows the case where the phase of the first signal light is π / 2. As a result, the output port 160 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 170 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 180 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4). The output port 190 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4).

[0047] 6(c) shows the case where the phase of the first signal light is π. As a result, the output port 160 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 170 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 180 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 190 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4).

[0048] 6(d) shows the case where the phase of the first signal light is 3π / 2. As a result, the output port 160 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 170 (first output port) outputs a complex signal light with an amplitude of 3 / 2 (optical intensity: 9 / 4). The output port 180 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4). The output port 190 outputs a complex signal light with an amplitude of 1 / 2 (optical intensity: 1 / 4).

[0049] That is, the first output port, which is one of the four output ports, outputs a complex signal light with a loss reduced to 1.3 dB relative to the total optical intensity of the light input to the four input ports.

[0050] FIG. 7 is a diagram showing the optical intensity distribution in the 90-degree optical hybrid 100. The optical intensity distribution in FIG. 7 was measured under the same conditions as those in FIG. 6. As shown in FIG. 7, it was found that when the phase of the first signal light is 0, strong light is output from the output port 160. Similarly, it was found that when the phase of the first signal light is π / 2, strong light is output from the output port 180. It was also found that when the phase of the first signal light is π, strong light is output from the output port 190. It was also found that when the phase of the first signal light is 3π / 2, strong light is output from the output port 170.

[0051] The phase of the local oscillator light may be 5π / 4. In this case, the phase shift of the high frequency light is set to π / 4. Alternatively, the local oscillator light may be input to the input port 120, and the high frequency light may be input to the input port 130. Furthermore, the first signal light may be input to the input port 140. Alternatively, when the first signal light is input to the input port 120 or the input port 130, the local oscillator light and the high frequency light may be input to the input port 110 or the input port 140, respectively.

[0052] That is, the phase shift of the high frequency light may be π / 4. Moreover, when the first signal light is input to the first inner input port, the high frequency light is input to the second outer input port. Moreover, when the first signal light is input to the first outer input port, the high frequency light is input to the second inner input port.

[0053] According to this aspect, by additionally inputting a signal light having a phase twice as large as that of the first signal light, it is possible to reduce loss of optical intensity more than in the past.

[0054] 3. Modification 2 of the First Embodiment In Section 3, a second modified example of the first embodiment will be described. In the second modified example, the description overlapping with the description of the first embodiment will be omitted.

[0055] 8 is a diagram showing a constellation when a first signal light, a local oscillator light, and two second signal lights are input to a 90-degree optical hybrid 100. Here, the second signal light is assumed to be phase conjugate light and high-frequency light. The phase conjugate light is signal light that has a phase conjugate relationship with the first signal light. The high-frequency light is signal light that has a phase twice as large as that of the first signal light.

[0056] Referring now to FIG. 8, E S The first signal light, E L is the local oscillator light, E S † is the phase conjugate light, E S (2)is high frequency light. The first signal light is input to the input port 110 (first outer input port), the local oscillator light is input to the input port 130 (first inner input port), the phase conjugate light is input to the input port 140 (second outer input port), and the high frequency light is input to the input port 120 (second inner input port).

[0057] 8(a) shows a case where the phase of the first signal light is 0. As a result, the output port 160 (first output port) outputs a complex signal light with an amplitude of 2 (optical intensity: 4). The output ports 170, 180, and 190 do not output any complex signal light.

[0058] 8(b) shows a case where the phase of the first signal light is π / 2. As a result, the output port 180 (first output port) outputs a complex signal light with an amplitude of 2 (optical intensity: 4). The output ports 160, 170, and 190 do not output any complex signal light.

[0059] 8(c) shows the case where the phase of the first signal light is π. As a result, the output port 190 (first output port) outputs a complex signal light with an amplitude of 2 (optical intensity: 4). The output ports 160, 170, and 180 do not output any complex signal light.

[0060] 8(d) shows a case where the phase of the first signal light is 3π / 2. As a result, the output port 170 (first output port) outputs a complex signal light with an amplitude of 2 (optical intensity: 4). The output ports 160, 180, and 190 do not output any complex signal light.

[0061] That is, the first output port, which is one of the four output ports, outputs a complex signal light in which the loss relative to the total optical intensity of the light input to the four input ports is reduced to 0 dB.

[0062] FIG. 9 is a diagram showing the optical intensity distribution in the 90-degree optical hybrid 100. The optical intensity distribution in FIG. 9 was measured under the same conditions as those in FIG. 8. As shown in FIG. 9, when the phase of the first signal light is 0, it was found that light is output only from the output port 160. Similarly, when the phase of the first signal light is π / 2, it was found that light is output only from the output port 180. Furthermore, it was found that when the phase of the first signal light is π, light is output only from the output port 190. Furthermore, it was found that when the phase of the first signal light is 3π / 2, light is output only from the output port 170.

[0063] The phase of the local oscillator light may be 5π / 4. In this case, the phase shift of the high frequency light is set to π / 4. Alternatively, the local oscillator light may be input to the input port 120, and the high frequency light may be input to the input port 130. Furthermore, the first signal light may be input to the input port 140, and the phase conjugate light may be input to the input port 110. Alternatively, when the first signal light and the phase conjugate light are input to the input port 120 or the input port 130, respectively, the local oscillator light and the high frequency light may be input to the input port 110 or the input port 140, respectively.

[0064] That is, when the first signal light is input to the first inner input port, the phase conjugate light is input to the second inner input port. Moreover, when the first signal light is input to the first inner input port, the high frequency light is input to the second outer input port. Moreover, when the first signal light is input to the first outer input port, the phase conjugate light is input to the second outer input port. Moreover, when the first signal light is input to the first outer input port, the high frequency light is input to the second inner input port. Moreover, the phase shift of the high frequency light is π / 4 when the phase of the local oscillator light is 5π / 4.

[0065] According to this embodiment, by additionally inputting two signal lights having a predetermined relationship and by setting the conditions appropriately, it is possible to reduce the loss of optical intensity more than ever before.

[0066] 4.Summary The 90-degree optical hybrid 100 is characterized in that two or more signal lights are input to one local oscillator light.

[0067] According to the first embodiment, the second signal light may be any signal light having a predetermined relationship with the first signal light. Also, the first output port, which is one of the four output ports, outputs a complex signal light having a loss of 0 to 1.3 dB relative to the total value of the optical intensities of the lights input to the four input ports. Specifically, for example, the loss may be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, or 1.3 dB, or may be within a range between any two of the numerical values ​​exemplified here.

[0068] That is, while a conventional 90-degree optical hybrid outputs a complex signal light with a loss of 3 dB relative to the total optical intensity of the light input to the four input ports, the 90-degree optical hybrid 100 of this embodiment is configured to output a complex signal light with a loss of 0 to 1.3 dB relative to the total optical intensity of the light input to the four input ports.

[0069] Therefore, the 90-degree optical hybrid 100 of this embodiment can be suitably used for long-distance transmission due to its configuration for efficiently outputting the power of signal light.

[0070] 5. Second embodiment A second embodiment of the present invention will be described in Section 5. In the second embodiment, the description overlapping with the description of the first embodiment will be omitted.

[0071] 5-1. Overall structure Fig. 10 is a diagram showing an example of the configuration of an information processing system including an optical decoding device 400 according to the second embodiment of the present invention. As shown in Fig. 10, the optical decoding device 400 is disposed between the optical processing system 200 and the electrical processing system 300, and decodes a signal input from the optical processing system 200 and outputs the decoded signal to the electrical processing system 300. In addition, a signal is transmitted from the electrical processing system 300 to the optical processing system 200 via an optical encoding device (not shown) and the like.

[0072] 5-2, optical decoding device 400 11 is a diagram showing a hardware configuration of the optical decoding device 400. The optical decoding device 400 includes four input ports (input port 410, input port 420, input port 430, and input port 440), an optical coupler 450, and four output ports (output port 460, output port 470, output port 480, and output port 490).

[0073] Here, the four input ports include two inner input ports (input port 420 and input port 430) that are adjacent to each other, and two outer input ports (input port 410 and input port 440) that are located outside the two inner input ports and adjacent to the two inner input ports, respectively.

[0074] Moreover, the optical coupler 450 is provided between four input ports (input port 410, input port 420, input port 430, and input port 440) and four output ports (output port 460, output port 470, output port 480, and output port 490), and is connected to the four input ports and the four output ports. Furthermore, the optical coupler 450 generates a complex signal light based on the third signal light, the probe light, and the fourth signal light. The third signal light, the probe light, and the fourth signal light will be described later.

[0075] 5-3. Optical interference method 12 is a diagram showing a constellation when the third signal light, the probe light, and the fourth signal light are input to the optical decoding device 400. The four input ports (input port 410, input port 420, input port 430, and input port 440) are configured to be able to input the third signal light, the probe light, and the fourth signal light. The third signal light is a binary phase-shift keyed signal light. The phase of the probe light is assumed to be 0. The fourth signal light is a binary phase-shift keyed signal light that is different from the third signal light. The electric field intensity of the probe light is assumed to be set to √2 times the electric field intensity of the third signal light.

[0076] Here, the third signal light and the fourth signal light are binary phase shift keyed signal lights, and therefore each has 1 bit of information. In this embodiment, the third signal light and the fourth signal light are input to form a combination of 2 bits of signal light. The third signal light and the fourth signal light may be multiplexed, for example, by wavelength division multiplexing, time division multiplexing, polarization division multiplexing, etc.

[0077] Fig. 12 will be described. In Fig. 12, Signal A is the third signal light, Probe is the probe light, and Signal B is the fourth signal light. The third signal light is input to input port 420 (third inner input port), the probe light is input to input port 440 (third outer input port), and the fourth signal light is input to input port 430 (fourth inner input port).

[0078] 12(a) shows a case where the phase of the third signal light is 0 and the phase of the fourth signal light is 0. As a result, the output port 460 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 470 (second output port) outputs a complex signal light with an amplitude of √10 / 4 (optical intensity: 5 / 8). The output port 480 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 490 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8).

[0079] 12(b) shows a case where the phase of the third signal light is 0 and the phase of the fourth signal light is π. As a result, the output port 460 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 470 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 480 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 490 (second output port) outputs a complex signal light with an amplitude of √10 / 4 (optical intensity: 5 / 8).

[0080] 12(c) shows a case where the phase of the third signal light is π and the phase of the fourth signal light is 0. As a result, the output port 460 (second output port) outputs a complex signal light with an amplitude of √10 / 4 (optical intensity: 5 / 8). The output port 470 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 480 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 490 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8).

[0081] 12(d) shows a case where the third signal light has a phase of π and the fourth signal light has a phase of π. As a result, the output port 460 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 470 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8). The output port 480 (second output port) outputs a complex signal light with an amplitude of √10 / 4 (optical intensity: 5 / 8). The output port 490 outputs a complex signal light with an amplitude of √2 / 4 (optical intensity: 1 / 8).

[0082] That is, the second output port, which is one of the four output ports, outputs a complex signal light having an extinction ratio of 7 dB with respect to any output port other than the second output port.

[0083] FIG. 13 is a diagram showing the light intensity distribution in the optical decoding device 400. The light intensity distribution in FIG. 13 was measured under the same conditions as those in FIG. 12. As shown in FIG. 13, it was found that when the phase of the third signal light is 0 and the phase of the fourth signal light is 0, strong light is output from the output port 470. Similarly, it was found that when the phase of the third signal light is 0 and the phase of the fourth signal light is π, strong light is output from the output port 490. It was also found that when the phase of the third signal light is π and the phase of the fourth signal light is 0, strong light is output from the output port 460. It was also found that when the phase of the third signal light is π and the phase of the fourth signal light is π, strong light is output from the output port 480.

[0084] The third signal light may be input to the input port 430, and the fourth signal light may be input to the input port 420. The probe light may be input to the input port 410. Furthermore, when the probe light is input to the input port 420 or the input port 430, the third signal light and the fourth signal light may be input to the input port 410 or the input port 440, respectively.

[0085] That is, the third signal light is input to the third inner input port or the third outer input port. Here, the third inner input port is one of the two inner input ports. Also, the third outer input port is one of the two outer input ports.

[0086] The phase of the probe light may be π. The electric field intensity of the probe light may be set to be the same as that of the third signal light. The probe light is input to one of the third inner input port and the third outer input port, which is different from the port to which the third signal light is input.

[0087] The fourth signal light is input to the fourth inner input port when the third signal light is input to the third inner input port. Also, the fourth signal light is input to the fourth outer input port when the third signal light is input to the third outer input port. Here, the fourth inner input port is a port different from the third inner input port among the two inner input ports. Also, the fourth outer input port is a port different from the third outer input port among the two outer input ports.

[0088] According to this embodiment, it is possible to output signal light only from a specific output port in accordance with the phase pattern of each light.

[0089] 6. Modification of the Second Embodiment Section 6 describes a modification of the second embodiment. In this modification, descriptions that overlap with the description of the second embodiment will be omitted.

[0090] 14 is a diagram showing a constellation when the third signal light, the probe light, the fourth signal light, and the sum frequency light are input to the optical decoding device 400. The four input ports (input port 410, input port 420, input port 430, and input port 440) are configured to further allow the input of sum frequency light. The sum frequency light is a signal light that is in an exclusive OR relationship with the third signal light and the fourth signal light.

[0091] Fig. 14 will be described. In Fig. 14, Signal A is the third signal light, Probe is the probe light, Signal B is the fourth signal light, and A xor B is the sum frequency light. The third signal light is input to input port 420 (third inner input port), the probe light is input to input port 440 (third outer input port), the fourth signal light is input to input port 430 (fourth inner input port), and the sum frequency light is input to input port 410 (fourth outer port).

[0092] 14(a) shows a case where the phase of the third signal light is 0 and the phase of the fourth signal light is 0. As a result, the output port 460 and the output port 490 did not output a complex signal. The output port 470 output a complex signal light with an amplitude of √(2-√2) (optical intensity: 2-√2). The output port 480 (second output port) output a complex signal light with an amplitude of √(2+√2) (optical intensity: 2+√2).

[0093] 14(b) shows a case where the phase of the third signal light is 0 and the phase of the fourth signal light is π. As a result, the output port 460 (second output port) output a complex signal light with an amplitude of √(2+√2) (optical intensity: 2+√2). The output ports 470 and 480 did not output a complex signal. The output port 490 (second output port) output a complex signal light with an amplitude of √(2-√2) (optical intensity: 2-√2).

[0094] 14(c) shows a case where the phase of the third signal light is π and the phase of the fourth signal light is 0. As a result, the output port 460 outputted a complex signal light with an amplitude of √(2-√2) (optical intensity: 2-√2). The output ports 470 and 480 did not output a complex signal light. The output port 490 (second output port) outputted a complex signal light with an amplitude of √(2+√2) (optical intensity: 2+√2).

[0095] 14(d) shows a case where the third signal light has a phase of π and the fourth signal light has a phase of π. As a result, the output port 460 and the output port 490 did not output complex signal light. The output port 470 (second output port) outputted a complex signal light with an amplitude of √(2+√2) (optical intensity: 2+√2). The output port 480 outputted a complex signal light with an amplitude of √(2-√2) (optical intensity: 2-√2).

[0096] That is, the second output port, which is one of the four output ports, outputs a complex signal light with an extinction ratio of 12.4 dB relative to any output port other than the second output port.

[0097] FIG. 15 is a diagram showing the light intensity distribution in the optical decoding device 400. The light intensity distribution in FIG. 15 was measured under the same conditions as those in FIG. 14. As shown in FIG. 15, it was found that when the phase of the third signal light is 0 and the phase of the fourth signal light is 0, strong light is output from the output port 480. Similarly, it was found that when the phase of the third signal light is 0 and the phase of the fourth signal light is π, strong light is output from the output port 460. It was also found that when the phase of the third signal light is π and the phase of the fourth signal light is 0, strong light is output from the output port 490. It was also found that when the phase of the third signal light is π and the phase of the fourth signal light is π, strong light is output from the output port 470.

[0098] The third signal light may be input to the input port 430, and the fourth signal light may be input to the input port 420. The probe light may be input to the input port 410, and the sum frequency light may be input to the input port 440. Furthermore, when the third signal light and the fourth signal light are input to the input port 410 or the input port 440, respectively, the probe light and the sum frequency light may be input to the input port 420 or the input port 430, respectively.

[0099] That is, when the third signal light is input to the third inner input port, the sum frequency light is input to the fourth outer input port, and when the third signal light is input to the third outer input port, the sum frequency light is input to the fourth inner input port.

[0100] 7.Summary The optical decoding device 400 is characterized in that it inputs two or more signal lights for one probe light.

[0101] According to the second embodiment, the second output port, which is one of the four output ports, outputs a complex signal light having an extinction ratio of 7 to 13 dB relative to any output port other than the second output port. Here, the extinction ratio can be used as a threshold value when performing photoelectric conversion, etc. Specifically, for example, the extinction ratio is 7, 8, 9, 10, 11, 12, or 13 dB, and may be within a range between any two of the numerical values ​​exemplified here.

[0102] According to this embodiment, the optical intensity of the signal light output according to the phase pattern of each light can be further increased.

[0103] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention.

[0104] 8.Other It may be provided in any of the following ways:

[0105] (1) A 90-degree optical hybrid comprising four input ports, an optical coupler, and four output ports, the four input ports including two inner input ports adjacent to each other and two outer input ports provided outside the two inner input ports and adjacent to the two inner input ports, the four input ports being configured to be able to input a first signal light, a local oscillator light, and a second signal light, the first signal light being a signal light that has been quadrature phase-shift keyed, the phase of the local oscillator light being π / 4 or 5π / 4, the second signal light being a signal light having a predetermined relationship with the first signal light, the first signal light, the local oscillator light, and the second signal light having the same electric field intensity, the first signal light being input to a first inner input port or a first outer input port, the first inner input port being one of the two inner input ports, the first outer input port being one of the two outer input ports, and the local oscillator light being one of the two outer input ports. a first output port that is one of the four output ports and outputs the complex signal light having a loss of 0 to 1.3 dB with respect to a total optical intensity of the light input to the four input ports, the first output port being one of the four output ports and the four input ports being connected to the four input ports, the first output port being one of the four output ports and the four input ports being connected to the four output ... output ports being connected to the four output ports, the first output port being one of the four output ports and the four input ports being connected to the four output ports,

[0106] According to this embodiment, the loss of light intensity can be reduced more than ever before.

[0107] (2) In the 90-degree optical hybrid described in (1) above, the second signal light is a phase conjugate light, the phase conjugate light is a signal light having a phase conjugate relationship with the first signal light, the phase conjugate light is input to the second inner input port when the first signal light is input to the first inner input port, and the phase conjugate light is input to the second outer input port when the first signal light is input to the first outer input port.

[0108] According to this embodiment, by additionally inputting signal light having a phase conjugate relationship, it is possible to reduce the loss of light intensity compared to the conventional art.

[0109] (3) In the 90-degree optical hybrid described in (1) or (2) above, the second signal light is high-frequency light, the high-frequency light is signal light having a phase twice that of the first signal light, a phase shift of the high-frequency light is π / 4 or 5π / 4, the high-frequency light is input to the second outer input port when the first signal light is input to the first inner input port, and the high-frequency light is input to the second inner input port when the first signal light is input to the first outer input port.

[0110] According to this aspect, by additionally inputting a signal light having a phase twice as large as that of the first signal light, it is possible to reduce loss of optical intensity more than in the past.

[0111] (4) In the 90-degree optical hybrid described in any one of (1) to (3) above, the second signal light is phase conjugate light and high-frequency light, the phase conjugate light is signal light in a phase conjugate relationship with the first signal light, the high-frequency light is signal light having a phase twice that of the first signal light, the phase conjugate light is input to the second inner input port when the first signal light is input to the first inner input port, the high-frequency light is input to the second outer input port when the first signal light is input to the first inner input port, the phase conjugate light is input to the second outer input port when the first signal light is input to the first outer input port, and the high-frequency light is input to the second inner input port when the first signal light is input to the first outer input port.

[0112] According to this embodiment, by additionally inputting two signal lights having a predetermined relationship, it is possible to reduce the loss of optical intensity more than ever before.

[0113] (5) The 90-degree optical hybrid according to (3) or (4) above, wherein the phase shift of the high-frequency light is set to π / 4 when the phase of the locally-oscillated light is 5π / 4.

[0114] According to this embodiment, by appropriately setting the conditions, it is possible to reduce the loss of light intensity more than ever before.

[0115] (6) An optical decoding device comprising four input ports, an optical coupler, and four output ports, the four input ports including two inner input ports adjacent to each other and two outer input ports provided outside the two inner input ports and adjacent to the two inner input ports, the four input ports being configured to be able to input a third signal light, a probe light, and a fourth signal light, the third signal light being a binary phase-shift keyed signal light, a phase of the probe light being 0 or π, the fourth signal light being a binary phase-shift keyed signal light and different from the third signal light, an electric field intensity of the probe light being set to be the same as or √2 times the electric field intensity of the third signal light, the third signal light being input to a third inner input port or a third outer input port, the third inner input port being one of the two inner input ports, the third outer input port being one of the two outer input ports, and the probe light being input to the third inner input port and the third outer input port. an optical decoding device comprising: an input port, a second output port, a third input port, a fourth input port, a fourth inner input port, a second output port, a fourth outer input port, a fourth inner input port, a fourth outer input port, a fourth inner input port, a fourth outer input port, a fourth outer input port, a fourth inner input port, a fourth outer input port, a fourth outer input port,

[0116] According to this embodiment, it is possible to output signal light only from a specific output port in accordance with the phase pattern of each light.

[0117] (7) In the optical decoding device described above in (6), the four input ports are further configured to be able to input sum frequency light, the sum frequency light being a signal light in an exclusive OR relationship with the third signal light and the fourth signal light, the sum frequency light being input to the fourth outer input port when the third signal light is input to the third inner input port, and the sum frequency light being input to the fourth inner input port when the third signal light is input to the third outer input port.

[0118] According to this embodiment, the optical intensity of the signal light output according to the phase pattern of each light can be further increased. Of course, this is not the case. [Explanation of symbols]

[0119] 110: Input port 120: Input port 130: Input port 140: Input port 150: Optical coupler 160: Output port 170: Output port 180: Output port 190: Output port 200: Optical processing system 300: Electrical processing system 400: Optical decoding device 410: Input port 420: Input port 430: Input port 440: Input port 450: Optical coupler 460: Output port 470: Output port 480: Output port 490: Output port

Claims

1. A 90 degree optical hybrid, Four input ports, an optical coupler, and four output ports; the four input ports include two inner input ports adjacent to each other, and two outer input ports provided outside the two inner input ports and adjacent to the two inner input ports, respectively; the four input ports are configured to be capable of inputting a first signal light, a local oscillator light, and a second signal light; the first signal light is a quadrature phase-shift keyed signal light, the phase of the local oscillator light is π / 4 or 5π / 4, the second signal light is a signal light having a predetermined relationship with the first signal light, the electric field intensities of the first signal light, the local oscillator light, and the second signal light are all equal to each other; the first signal light is input to a first inner input port or a first outer input port; the first inner input port is one of the two inner input ports; the first outer input port is one of the two outer input ports, the local oscillator light is input to one of the first inner input port and the first outer input port, which is different from a port to which the first signal light is input; the second signal light is input to at least one of a second inner input port and a second outer input port; the second inner input port is one of the two inner input ports that is different from the first inner input port, the second outer input port is one of the two outer input ports that is different from the first outer input port, the optical coupler is provided between the four input ports and the four output ports and is connected to the four input ports and the four output ports; the optical coupler generates a complex signal light based on the first signal light, the local oscillator light, and the second signal light; a first output port which is one of the four output ports outputs the complex signal light having a loss of 0 to 1.3 dB with respect to a total value of the optical intensities of the lights input to the four input ports; 90 degree optical hybrid.

2. 2. The 90 degree optical hybrid according to claim 1, the second signal light is a phase conjugate light, the phase conjugate light is a signal light that is in a phase conjugate relationship with the first signal light, the phase conjugate light is input to the second inner input port when the first signal light is input to the first inner input port; the phase conjugate light is input to the second outer input port when the first signal light is input to the first outer input port; 90 degree optical hybrid.

3. 2. The 90 degree optical hybrid according to claim 1, the second signal light is a high-frequency light, the high frequency light is a signal light having a phase twice as high as that of the first signal light, the phase shift of the high-frequency light is π / 4 or 5π / 4; the high frequency light is input to the second outer input port when the first signal light is input to the first inner input port; the high frequency light is input to the second inner input port when the first signal light is input to the first outer input port; 90 degree optical hybrid.

4. 2. The 90 degree optical hybrid according to claim 1, the second signal light is a phase conjugate light and a high frequency light, the phase conjugate light is a signal light that is in a phase conjugate relationship with the first signal light, the high frequency light is a signal light having a phase twice as high as that of the first signal light, the phase conjugate light is input to the second inner input port when the first signal light is input to the first inner input port; the high frequency light is input to the second outer input port when the first signal light is input to the first inner input port; the phase conjugate light is input to the second outer input port when the first signal light is input to the first outer input port; the high frequency light is input to the second inner input port when the first signal light is input to the first outer input port; 90 degree optical hybrid.

5. 4. The 90 degree optical hybrid according to claim 3, The phase shift of the high frequency light is set to π / 4 when the phase of the local oscillator light is 5π / 4. 90 degree optical hybrid.

6. An optical decoding device, Four input ports, an optical coupler, and four output ports; the four input ports include two inner input ports adjacent to each other, and two outer input ports provided outside the two inner input ports and adjacent to the two inner input ports, respectively; the four input ports are configured to be capable of inputting a third signal light, a probe light, and a fourth signal light; the third signal light is a binary phase shift keyed signal light, the phase of the probe light is 0 or π; the fourth signal light is a binary phase-shift keyed signal light different from the third signal light, the electric field intensity of the probe light is set to be equal to or √2 times the electric field intensity of the third signal light, the third signal light is input to a third inner input port or a third outer input port; the third inner input port is one of the two inner input ports, the third outer input port is one of the two outer input ports, the probe light is input to one of the third inner input port and the third outer input port, which is different from a port to which the third signal light is input; the fourth signal light is input to a fourth inner input port when the third signal light is input to the third inner input port; the fourth signal light is input to a fourth outer input port when the third signal light is input to the third outer input port; the fourth inner input port is one of the two inner input ports that is different from the third inner input port, the fourth outer input port is one of the two outer input ports that is different from the third outer input port, the optical coupler is provided between the four input ports and the four output ports and is connected to the four input ports and the four output ports; the optical coupler generates a complex signal light based on the third signal light, the probe light, and the fourth signal light; a second output port which is one of the four output ports outputs the complex signal light having an extinction ratio of 7 to 13 dB with respect to any output port other than the second output port; Optical decoding device.

7. 7. The optical decoding device according to claim 6, the four input ports are further configured to be capable of inputting sum frequency light; the sum frequency light is a signal light in an exclusive OR relationship with the third signal light and the fourth signal light, the sum frequency light is input to the fourth outer input port when the third signal light is input to the third inner input port; the sum frequency light is input to the fourth inner input port when the third signal light is input to the third outer input port; Optical decoding device.

Images