Signal generation device

Abstract

This signal generation device comprises: a light source that outputs reference light having a reference optical frequency; a light-splitting unit that splits the reference light outputted from the light source into two paths; a first modulation unit that modulates the reference light split by the light-splitting unit by using a first frequency; at least one second modulation unit that modulates the modulated optical signals modulated by the first modulation unit by using a second frequency equal to the frequency interval in a frequency band; and at least one photodiode that generates a plurality of local signals in a desired frequency band by photo-mixing the light subjected to frequency modulation by the at least one second modulation unit and the reference light split by the light-splitting unit.　

Description

signal generator

[0001] The present invention relates to a signal generating device.

[0002] The use of millimeter waves and sub-terahertz waves is being considered for mobile communications beyond 6G (generation 6G). Utilizing a wide range of frequencies, from low to high, will enable higher-capacity communications. To accommodate this wide range of frequencies, base stations must be equipped with RF (Radio Frequency) circuits for multiple frequency bands. However, this requires a local oscillator (LO) and frequency converter for each frequency, complicating the RF circuitry. To address this issue, a method has been proposed that uses difference frequency generation between two optical waves to generate a signal (LO signal) output by a local oscillator (see, for example, Non-Patent Documents 1 and 2).

[0003] Mario Weiss, et al., “60-GHz Photonic Millimeter-Wave Link for Short- to Medium-Range Wireless Transmission Up to 12.5 Gb / s”, Journal of Lightwave Technology, Volume: 26, Issue: 15, August 2008. Song Yu, Wanyi Gu, Aiying Yang, Tao Jiang, and Chonggang Wang, “A Frequency Quadrupling Optical mm-Wave Generation for Hybrid Fiber-Wireless Systems”, IEEE Journal on Selected Areas in Communications, Volume: 31, Issue: 12, Dec. 2013.

[0004] However, the above-mentioned method can only generate an LO signal of a single frequency. While it is possible to generate local signals of different frequencies using a PLL (Phase Lock Loop) circuit, this method has the drawback of requiring time to change the operating frequency of the local oscillator and of not being able to generate LO signals of multiple frequencies simultaneously. Thus, the conventional method has the drawback of not being able to simultaneously generate LO signals of multiple frequencies.

[0005] In view of the above circumstances, an object of the present invention is to provide a technique that can simultaneously generate LO signals of multiple frequencies.

[0006] One aspect of the present invention is a signal generating device comprising: a light source that outputs reference light having a reference optical frequency; an optical branching unit that branches the reference light output from the light source into two paths; a first modulation unit that modulates the reference light branched by the optical branching unit at a first frequency; one or more second modulation units that modulate the modulated optical signal modulated by the first modulation unit at a second frequency equal to a frequency interval within a frequency band; and one or more photodiodes that generate multiple local signals within a desired frequency band by photomixing light that has been frequency-modulated by the one or more second modulation units with the reference light branched by the optical branching unit.

[0007] The present invention makes it possible to generate LO signals of multiple frequencies together.

[0008] FIG. 1 is a diagram showing an example of the configuration of a signal generating device according to a first embodiment; FIG. 2 is a diagram showing an outline of the processing flow of the signal generating device according to the first embodiment; FIG. 3 is a flowchart showing the processing flow of the signal generating device according to the first embodiment; FIG. 4 is a diagram showing an example of the configuration of a signal generating device according to a second embodiment; FIG. 5 is a diagram showing an outline of the processing flow of the signal generating device according to the second embodiment; FIG. 6 is a diagram showing an example of the configuration of a signal generating device according to a third embodiment; and FIG. 7 is a diagram showing an example of the configuration of a signal generating device according to a fourth embodiment.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] First Embodiment FIG. 1 is a diagram illustrating an example of the configuration of a signal generating device 10 according to a first embodiment. FIG. 2 is a diagram illustrating an outline of the processing flow of the signal generating device 10 according to the first embodiment. The signal generating device 10 is a device that generates multiple local signals in a wide frequency range. For example, the signal generating device 10 can generate a CW (Continuous Wave) having any frequency by using photomixing technology to generate a difference frequency between two light waves with different wavelengths. Therefore, the signal generating device 10 uses this technology to generate high-frequency local signals ranging from several GHz to several hundred GHz.

[0011] The signal generating device 10 includes a laser light source 101 , an optical branching unit 102 , a local oscillator 103 , an LN modulator 104 , a BPF 105 , a local oscillator 106 , an LN modulator 107 , a PD 108 , and a wavelength distributor 109 .

[0012] The laser light source 101 emits a reference optical frequency f ０ The light of the reference light f ０ Output as

[0013] The optical branching unit 102 branches the reference light f ０ The reference light f output from the optical branching unit 102 is branched into a first path and a second path. The first path is connected to an LN modulator 104, and the second path is connected to a PD 108. ０ is input to the LN modulator 104 and the PD 108.

[0014] The local oscillator 103 outputs an LO signal of a preset frequency. For example, the local oscillator 103 outputs an LO signal of a frequency of 80 GHz. Note that, although a configuration in which the local oscillator 103 outputs an LO signal of 80 GHz is shown as an example here, the LO signal output by the local oscillator 103 is not limited to this and may have any frequency as long as it has a center frequency of a desired radio frequency band.

[0015] The LN modulator 104 converts the optical frequency f ０ The reference light f is modulated using an LO signal (for example, an 80 GHz LO signal) output from the local oscillator 103. ０In addition, sidebands are generated at 80 GHz intervals. For the sake of simplicity, in FIG. 2A, the optical frequency f ０ Only the side band at +80 is shown. The LN modulator 104 is one aspect of the first modulation section.

[0016] The BPF 105 is a band-pass filter that passes components of a preset frequency band. For example, the BPF 105 is set to pass a frequency band of the side band generated by modulation by the LN modulator 104. As a result, the BPF 105 passes a frequency band of the optical frequency f ０ Allows +80 light to pass through.

[0017] The local oscillator 106 outputs an LO signal of a preset frequency. For example, the local oscillator 106 outputs an LO signal of a frequency of 0.5 GHz. Note that, although a configuration in which the local oscillator 106 outputs an LO signal of 0.5 GHz is shown as an example here, the LO signal output by the local oscillator 106 is not limited to this and may have a frequency equal to the frequency interval within a desired radio frequency band.

[0018] The LN modulator 107 converts the light (e.g., optical frequency f ０ The LN modulator 107 modulates the optical frequency f ０ The LN modulator 107 modulates the optical frequency f ０ It generates multiple narrowly spaced sidebands centered around +80 light. For example, optical frequency f ０ In addition to the +80 light, the light frequency f ０ +80±0.5 position, f ０ For ease of understanding, in FIG. 2B, the optical frequency f that is not extracted by the BPF 105 is not shown. ０ The LN modulator 107 is one aspect of the second modulation section.

[0019] The PD 108 divides the reference light output from the optical branching unit 102 and a plurality of lights (for example, light frequencies f ０ +80 light and light frequency f ０ The PD 108 mixes the received signal with the sidebands generated by modulating the +80 light. This allows the PD 108 to generate multiple LO signals using difference frequency generation, as shown in FIG. 2C.

[0020] The wavelength distributor 109 extracts an LO signal in a frequency band to be used (for example, a frequency band of 80 GHz or higher) from the plurality of LO signals generated by the PD 108 as shown in FIG. 2C.

[0021] 3 is a flowchart showing the process flow of the signal generating device 10 according to the first embodiment. ０ (Step S101). The reference light f output from the laser light source 101 ０ is input to the optical branching unit 102. The optical branching unit 102 divides the input reference light f ０ is branched to the LN modulator 104 and the PD 108 (step S102).

[0022] The LN modulator 104 receives the reference light f ０ with the LO signal output from the local oscillator 103 (step S103). The BPF 105 passes the frequency band of the side band generated by the modulation by the LN modulator 104 (step S104). Thereafter, the LN modulator 107 modulates the light of the side band that has passed through the BPF 105 with the LO signal output from the local oscillator 106 (step S105).

[0023] The PD 108 divides the light obtained by modulation of the LN modulator 107 and the reference light f ０ The PD 108 generates a plurality of LO signals by mixing the LO signals and the PD 108 (step S106). The PD 108 outputs the generated plurality of LO signals to the wavelength distributor 109. The wavelength distributor 109 extracts an LO signal of a frequency band to be used from the plurality of LO signals output from the PD 108 (step S107).

[0024] According to the signal generating device 10 configured as above, the reference optical frequency f ０ The reference light f ０ and a laser light source 101 that outputs a reference light f ０ a light branching unit 102 that branches the reference light f into two paths, and ０ at the center frequency of a desired radio frequency band, an LN modulator 107 that modulates the modulated optical signal modulated by the LN modulator 104 at a frequency equal to the frequency interval within the frequency band, and a light frequency modulated by the LN modulator 107 and a reference light f branched by the optical branching unit 102. ０ and a PD 108 that generates a plurality of local signals within a desired frequency band by photomixing with the

[0025] In this way, the signal generating device 10 receives the reference light f output from the single laser light source 101. ０ The LN modulator 107 modulates the reference frequency f ０ The light having this narrow pulse and the reference light f output from the single laser light source 101 are pulsed at narrow intervals. ０ By photomixing these two waves, multiple LO signals are generated, which makes it possible to simultaneously generate LO signals of multiple frequencies.

[0026] Second Embodiment In the first embodiment, a configuration was described in which multiple LO signals are generated within a specific frequency band. In the second embodiment, a configuration will be described in which multiple LO signals are generated in each of multiple frequency bands. Here, the multiple frequency bands are bands assigned to different radio frequency bands, such as V band, E band, W band, and D band. Note that the multiple frequency bands are not limited to these, but the following description will be given using the above four bands as an example.

[0027] As described above, when generating multiple LO signals in multiple frequency bands, the optical frequency interval comb generated based on the laser light source 101 needs to have a wide comb interval. Then, the light of the optical frequency interval comb is passed through multiple bandpass filters that pass frequency bands corresponding to each frequency band, and is finely modulated from the center of the band as in the first embodiment, and then multiple LO signals are generated for each frequency band by photomixing. A specific configuration for realizing the above processing will be described below.

[0028] Fig. 4 is a diagram showing an example of the configuration of a signal generating device 10a according to the second embodiment. Fig. 5 is a diagram showing an outline of the processing flow of the signal generating device 10a according to the first embodiment. The signal generating device 10a includes a laser light source 101, an optical branching unit 102, a local oscillator 103, an LN modulator 104, multiple BPFs 105, a local oscillator 106, multiple LN modulators 107, multiple PDs 108, multiple wavelength distributors 109, and an optical branching unit 110a. The signal generating device 10a differs in configuration from the signal generating device 10 in that it includes multiple BPFs 105, LN modulators 107, PDs 108, and wavelength distributors 109, and in that it newly includes an optical branching unit 110a. The following description will focus on the differences from the signal generating device 10.

[0029] 4 illustrates a configuration in which the signal generating device 10a generates a plurality of LO signals in each of four radio frequency bands (e.g., V band, E band, W band, and D band), and shows a case in which the signal generating device 10a includes four BPFs 105, LN modulators 107, PDs 108, and wavelength distributors 109. Since the signal generating device 10a is only required to be able to generate a plurality of LO signals in each of the different radio frequency bands, it is sufficient for the signal generating device 10a to include two or more BPFs 105, LN modulators 107, PDs 108, and wavelength distributors 109.

[0030] The laser light source 101 emits light at a frequency f ｃｅｏ The light of the reference light f ｃｅｏ Output as

[0031] The optical branching unit 102 branches the reference light f ｃｅｏThe reference light f output from the optical branching unit 102 is branched into a first path and a second path. The first path is connected to an LN modulator 104, and the second path is connected to a PD 108. ｃｅｏ is input to the LN modulator 104 and the PD 108.

[0032] The local oscillator 103 outputs an LO signal of a preset frequency. For example, in the signal generating device 10a, the local oscillator 103 outputs an LO signal of a frequency of 10 GHz. Note that, although a configuration in which the local oscillator 103 outputs an LO signal of 10 GHz is shown as an example here, the LO signal output by the local oscillator 103 is not limited to this.

[0033] The LN modulator 104 receives the reference light f output from the optical branching unit 102. ｃｅｏ is modulated using an LO signal (for example, a 10 GHz LO signal) output from the local oscillator 103. As a result, the reference light f ｃｅｏ In addition, sidebands are generated at 10 GHz intervals. For the sake of simplicity, in FIG. 5A, the center frequencies of the four frequency bands (optical frequency f ｃｅｏ +60, optical frequency f ｃｅｏ +80, optical frequency f ｃｅｏ +100, optical frequency f ｃｅｏ +130). For example, the optical frequency f ｃｅｏ The position of +60 represents the center frequency of the V band, and the optical frequency f ｃｅｏ The position of +80 represents the center frequency of the E band, and the optical frequency f ｃｅｏ The position of +100 represents the center frequency of the W band, and the optical frequency f ｃｅｏ The position of +130 represents the center frequency of the D band. The LN modulator 104 outputs the modulation result to the optical branching unit 110a.

[0034] The optical branching unit 110a branches the output of the LN modulator 104 to each BPF 105. The optical branching unit 110a is one aspect of an output unit.

[0035] The BPF 105 is a bandpass filter that passes components of a preset frequency band. The BPF 105-1 is set to pass, for example, components of the V-band frequency band. The BPF 105-2 is set to pass, for example, components of the E-band frequency band. The BPF 105-3 is set to pass, for example, components of the W-band frequency band. The BPF 105-4 is set to pass, for example, components of the D-band frequency band.

[0036] As a result, each BPF 105 passes light of a different frequency band, as shown in Fig. 5A. BPF 105-1 passes, for example, V-band frequency components. BPF 105-2 passes, for example, E-band frequency components. BPF 105-3 passes, for example, W-band frequency components. BPF 105-4 passes, for example, D-band frequency components.

[0037] The LN modulator 107 modulates the light that has passed through the BPF 105 using the LO signal (LO signal of 0.5 GHz) output from the local oscillator 106. The LN modulator 107-1 modulates the light of the optical frequency f ０ The LN modulator 107-1 modulates the optical frequency f ｃｅｏ The LN modulator 107-2 generates a plurality of narrowly spaced side bands centered on the light of +60. For example, the LN modulator 107-2 generates the optical frequency f ０ The LN modulator 107-2 modulates the optical frequency f ｃｅｏ It generates multiple closely spaced sidebands centered around +80 light.

[0038] The LN modulator 107-3 converts, for example, the optical frequency f ０ The LN modulator 107-3 modulates the optical frequency f ｃｅｏ The LN modulator 107-4 generates a plurality of narrowly spaced side bands centered around +100 light. ０The LN modulator 107-4 modulates the optical frequency f ｃｅｏ As an example, multiple sidebands with narrow intervals are generated around the light of +130. ｃｅｏ As shown in FIG. 5B, the optical frequency f ｃｅｏ Pulses occur at closely spaced intervals around the +80 light.

[0039] The PD 108 receives the reference light f output from the optical branching unit 102. ｃｅｏ The PD 108-1 mixes the reference light f output from the optical branching unit 102 with a plurality of lights in each frequency band generated by modulation by the LN modulator 107. ｃｅｏ and a plurality of lights in the V band (for example, optical frequencies f ｃｅｏ +60 light and f ｃｅｏ +60±0.5 GHz interval light). This allows the PD 108-1 to generate multiple LO signals. In this way, the PD 108-1 generates multiple LO signals within the V-band.

[0040] The PD 108-2 receives, for example, the reference light f output from the optical branching unit 102. ｃｅｏ and a plurality of lights in the E band (e.g., optical frequencies f ｃｅｏ +80 light and f ｃｅｏ +80±0.5 GHz interval light). As a result, the PD 108-2 generates a plurality of LO signals. In this way, the PD 108-2 generates a plurality of LO signals in the E band.

[0041] The PD 108-3 receives the reference light f output from the optical branching unit 102, for example. ｃｅｏ and a plurality of lights in the W band (for example, optical frequencies f ｃｅｏ +100 light and f ｃｅｏ+100±0.5 GHz interval light). This allows the PD 108-3 to generate multiple LO signals. In this way, the PD 108-3 generates multiple LO signals in the W band.

[0042] The PD 108-4 receives, for example, the reference light f output from the optical branching unit 102. ｃｅｏ and a plurality of lights in the D band (e.g., optical frequencies f ｃｅｏ +130 light and f ｃｅｏ +130±0.5 GHz interval light). This allows the PD 108-4 to generate multiple LO signals. In this way, the PD 108-4 generates multiple LO signals within the D band.

[0043] 5C shows a plurality of LO signals (LO signals in the E band) generated by the PD 108-2. In this manner, each PD 108 generates a plurality of LO signals for each frequency band by utilizing difference frequency generation.

[0044] The wavelength distributor 109 extracts an LO signal of a desired frequency band from the multiple LO signals for each frequency band generated by the PD 108. The wavelength distributor 109-1 extracts an LO signal of a desired frequency band from the multiple LO signals for the V band generated by the PD 108-1. The wavelength distributor 109-2 extracts an LO signal of a desired frequency band from the multiple LO signals for the E band generated by the PD 108-2. The wavelength distributor 109-3 extracts an LO signal of a desired frequency band from the multiple LO signals for the W band generated by the PD 108-3. The wavelength distributor 109-4 extracts an LO signal of a desired frequency band from the multiple LO signals for the D band generated by the PD 108-4. The wavelength distributor 109 is one aspect of multiple local signal acquisition units.

[0045] FIG. 5C shows an example in which the wavelength distributor 109-2 extracts an LO signal in a desired frequency band from among a plurality of LO signals in the E band.

[0046] The signal generating device 10a configured as described above can generate multiple LO signals in multiple bands. This allows a single signal generating device 10 to provide LO signals with consistent phases across frequencies when performing communications over multiple frequency bands. This improves convenience.

[0047] (Third Embodiment) As shown in the second embodiment, multiple LO signals are generated for each frequency band. In the second embodiment, a desired LO signal is extracted from the multiple generated LO signals by a wavelength distributor. In contrast, in the third embodiment, a configuration will be described in which the output from a PD is separated by frequency and the desired LO signal is selected by an electrical switch.

[0048] To realize the above configuration, the PD needs to have a function to demultiplex multiple LO signals by frequency and a function to output an LO signal of a desired frequency from the demultiplexed LO signals. A specific configuration for realizing the above processing is described below.

[0049] 6 is a diagram showing an example of the configuration of a signal generating device 10b according to the third embodiment. The signal generating device 10b includes a laser light source 101, an optical branching unit 102, a local oscillator 103, an LN modulator 104, multiple BPFs 105, a local oscillator 106, multiple LN modulators 107, multiple PDs 108, a wavelength multiplexing / demultiplexing unit 111b, multiple demultiplexing units 112b, and multiple switches 113b. The signal generating device 10b differs from the signal generating device 10a in configuration in that it includes a wavelength multiplexing / demultiplexing unit 111b instead of the optical branching unit 110a, and in that it includes multiple demultiplexing units 112b and multiple switches 113b instead of the multiple wavelength distributors 109. The following description will focus on the differences from the signal generating device 10a.

[0050] The wavelength multiplexing / demultiplexing unit 111b demultiplexes the output from the LN modulator 104 by wavelength. The wavelength multiplexing / demultiplexing unit 111b is, for example, an AWG (Arrayed Waveguide Grating). As described in the second embodiment, the LN modulator 104 generates an optical frequency interval comb with a wide comb spacing. Therefore, the wavelength multiplexing / demultiplexing unit 111b demultiplexes the optical frequency interval comb generated by the LN modulator 104 by wavelength and outputs the demultiplexed signals from each output port corresponding to the wavelength. From the output of the wavelength multiplexing / demultiplexing unit 111b, components of desired frequency bands are extracted by a plurality of BPFs 105 that pass frequency band components of each frequency band. The wavelength multiplexing / demultiplexing unit 111b is one aspect of an output unit.

[0051] The demultiplexing unit 112b is connected to the PD 108. The demultiplexing unit 112b has multiple output ports. The demultiplexing unit 112b demultiplexes multiple LO signals output from the PD 108 by frequency and outputs the signals from the corresponding output ports. The demultiplexing unit 112b-1 demultiplexes multiple LO signals in, for example, the V band by frequency. The demultiplexing unit 112b-2 demultiplexes multiple LO signals in, for example, the E band by frequency. The demultiplexing unit 112b-3 demultiplexes multiple LO signals in, for example, the W band by frequency. The demultiplexing unit 112b-4 demultiplexes multiple LO signals in, for example, the D band by frequency.

[0052] The switch 113b is connected to one of the multiple output ports of the demultiplexing unit 112b. The switch 113b selects the LO signal of the desired frequency by connecting to an output port that outputs the LO signal of the desired frequency from the multiple output ports of the demultiplexing unit 112b. In this way, the switch 113b selects the LO signal of the desired frequency by switching the connection with the demultiplexing unit 112b. The switch 113b is one aspect of the multiple local signal acquisition units.

[0053] According to the signal generating device 10b configured as above, it is possible to obtain the same effects as those of the second embodiment.

[0054] A conventional method for generating multiple LO signals is to use a PLL (Phase Lock Loop) circuit. However, when changing the LO operating frequency using a PLL circuit, the multiplication rate must be changed, which poses a problem of taking time for the frequency to stabilize. In contrast, the signal generating device 10b can switch the frequency of the LO signal to be used simply by switching using switch 113b (an electrical switch). This shortens the time it takes for operation to stabilize.

[0055] (Fourth Embodiment) In the second embodiment, a configuration was shown in which an optical frequency interval comb having a wide comb spacing is branched by a branching unit. In the second embodiment, because the optical frequency interval comb is branched by a branching unit, the same light is input to all of the subsequent BPFs. In contrast, in the fourth embodiment, a configuration will be described in which an optical frequency interval comb having a wide comb spacing is branched by using a wavelength multiplexer / demultiplexer that branches the optical frequency interval comb by wavelength, such as an AWG.

[0056] 7 is a diagram showing an example of the configuration of a signal generating device 10c according to the fourth embodiment. The signal generating device 10b includes a laser light source 101, an optical branching unit 102, a local oscillator 103, an LN modulator 104, multiple BPFs 105, a local oscillator 106, multiple LN modulators 107, multiple PDs 108, multiple wavelength distributors 109, and a wavelength multiplexing / demultiplexing unit 111c. The signal generating device 10c differs in configuration from the signal generating device 10a in that it includes the wavelength multiplexing / demultiplexing unit 111c instead of the optical branching unit 110a. The following description will focus on the differences from the signal generating device 10a.

[0057] The wavelength multiplexing / demultiplexing unit 111c demultiplexes the output from the LN modulator 104 by wavelength. The wavelength multiplexing / demultiplexing unit 111c is, for example, an AWG. As described in the second embodiment, the LN modulator 104 generates an optical frequency interval comb with a wide comb spacing. Therefore, the wavelength multiplexing / demultiplexing unit 111c demultiplexes the optical frequency interval comb generated by the LN modulator 104 by wavelength and outputs the demultiplexed signals from each output port corresponding to the wavelength. From the output of the wavelength multiplexing / demultiplexing unit 111c, components of desired frequency bands are extracted by a plurality of BPFs 105 that pass frequency band components of each frequency band.

[0058] According to the signal generating device 10c configured as above, it is possible to obtain the same effects as those of the second embodiment.

[0059] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0060] The present invention is applicable to a technique for generating a high-frequency signal by photomixing.

[0061] 10, 10a, 10b, 10c... signal generating device, 101... laser light source, 102... optical branching section, 103... local oscillator, 104... LN modulator, 105, 105-1 to 105-4... BPF, 106... local oscillator, 107, 107-1 to 107-4... LN modulator, 108, 108-1 to 108-4... PD, 109, 109-1 to 109-4... wavelength distributor, 110a... optical branching section, 111b, 111c... wavelength multiplexing / demultiplexing section, 112b, 112b-1 to 112b-4... demultiplexing section, 113b, 113b-1 to 113b-4... switch

Claims

1. A signal generating device comprising: a light source that outputs reference light having a reference optical frequency; an optical branching unit that branches the reference light output from the light source into two paths; a first modulation unit that modulates the reference light branched by the optical branching unit at a first frequency; one or more second modulation units that modulate the modulated optical signal modulated by the first modulation unit at a second frequency equal to the frequency interval within a frequency band; and one or more photodiodes that generate multiple local signals within a desired frequency band by photomixing the light that has been frequency-modulated by the one or more second modulation units with the reference light branched by the optical branching unit.

2. The signal generating device according to claim 1, further comprising a plurality of filters that extract frequency components of different frequency bands from the modulated optical signal modulated by the first modulation unit, wherein the one or more second modulation units and the one or more photodiodes are a plurality of second modulation units and a plurality of photodiodes, wherein the first modulation unit generates an optical frequency interval comb having a wide comb interval as the modulated optical signal by modulating the reference light at a first frequency, wherein the plurality of second modulation units are connected to different filters of the plurality of filters and modulate the frequency components of the frequency band extracted by the filters at the second frequency, and wherein the plurality of photodiodes generate a plurality of local signals in each of the different frequency bands by photomixing the light that has been frequency modulated by the plurality of second modulation units and the reference light branched by the optical branching unit.

3. The signal generating device according to claim 2, further comprising an output section that branches the modulated optical signal obtained by the first modulation section and outputs it to the plurality of filters, or that demultiplexes the modulated optical signal according to wavelength and outputs it to the plurality of filters.

4. The signal generating device according to claim 2 or 3, further comprising a plurality of local signal acquiring units that extract or select a local signal of a desired frequency from the plurality of local signals generated in different frequency bands by the plurality of photodiodes.

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