A reconfigurable large-bandwidth frequency hopping system and method based on optical frequency comb

Abstract

The application discloses a reconfigurable large-bandwidth frequency hopping system and method based on an optical frequency comb, and belongs to the technical field of communication. The system comprises a laser, a first microwave source, a second microwave source, a third microwave source, a first coupler, a second coupler, a first intensity modulator, a second intensity modulator, a first optical filter, a second optical filter, a third optical filter, a fourth optical filter, a high-speed optical switch, a double-parallel Mach-Zehnder intensity modulator, a controller, a 90-degree mixer, a photodetector and a doped fiber amplifier. The system can generate high-quality optical frequency combs by cascading intensity modulators, can provide rich spectrum resources for frequency hopping, can realize high-speed switching by combining a commercial high-speed optical switch, and can realize reconfigurable large-bandwidth frequency hopping signal generation by carrier-suppressed single sideband modulation of a double-parallel Mach-Zehnder modulator and heterodyne detection.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave photonics, communication technology and signal processing, and particularly relates to a reconfigurable large-bandwidth frequency hopping system and method based on an optical frequency comb. BACKGROUND

[0002] At present, the anti-interference communication system constructed by using traditional electronic technology cannot meet the application requirements in terms of bandwidth, parallel processing speed, dynamic range and real-time performance, and the frequency hopping speed thereof is only tens of thousands per second, and the frequency is only in the order of GHz, which is more and more difficult to meet the actual application requirements of battlefield communication anti-interference.

[0003] In view of this problem, the microwave photonics technology can combine microwave and photonics, utilize the advantages of uniform performance and high-speed processing in photonics in a large bandwidth, and through electric-optical and optical-electric conversion, modulate the radio frequency signal in the optical domain for frequency hopping processing, so as to generate a high-speed, ultra-wideband and tunable anti-interference frequency hopping signal through heterodyne detection. The microwave photonics technology has a wide application prospect in radar, satellite communication, electronic warfare and the like.

[0004] At present, the frequency hopping generation methods based on microwave photonics mainly include a bias point regulation frequency hopping generation method, an optical injection frequency hopping generation method and a frequency hopping generation method based on a microwave photonics filter. Among them, the frequency hopping generation method based on the bias point regulation can only generate a local frequency and a frequency multiplication double-frequency point frequency hopping signal, the frequency hopping frequency points are few, and the anti-interference capability is poor. The optical injection frequency hopping generation method needs to strictly control the frequency difference of master and slave lasers, the injection ratio and the temperature of the laser, the experimental conditions are harsh, the system structure stability is poor, and it is difficult to be applied in engineering. The frequency hopping generation method based on the microwave photonics filter needs to accurately control the temperature of the microcavity to realize the control of the filter channel, and it is difficult to be applied in engineering. Therefore, how to realize a reconfigurable, multi-frequency point, large-bandwidth, high hopping speed and high stability frequency hopping generation method based on the microwave photonics technology is a problem to be solved. SUMMARY

[0005] The application aims to provide a reconfigurable large-bandwidth frequency hopping system and method based on an optical frequency comb, which can solve the problems of bandwidth limitation and hopping speed limitation in the existing frequency hopping technology.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0007] A reconfigurable large-bandwidth frequency hopping system based on an optical frequency comb comprises a laser, a first microwave source, a second microwave source, a third microwave source, a first coupler, a second coupler, a first intensity modulator, a second intensity modulator, a first optical filter, a second optical filter, a third optical filter, a fourth optical filter, a high-speed optical switch, a double-parallel Mach-Zehnder intensity modulator, a controller, a 90-degree mixer, a photodetector and a doped fiber amplifier.

[0008] The optical carrier generated by the laser is input to a cascaded intensity modulator to generate a high-flatness, multi-tooth, high-quality optical frequency comb;

[0009] The local oscillator signal generated by the first microwave source is directly applied to the first intensity modulator;

[0010] The local oscillator signal generated by the second microwave source is directly applied to the second intensity modulator;

[0011] The first intensity modulator modulates the radio frequency signal generated by the first microwave source onto the optical carrier transmitted by the laser, and modulates ±1 and ±2 order sidebands with the optical carrier frequency as the center frequency to generate a high-flatness primary optical frequency comb, which then enters the second intensity modulator.

[0012] The second intensity modulator modulates the radio frequency signal generated by the second microwave source onto the primary optical frequency comb, and generates ±1 and ±2 order sidebands with each tooth of the output optical frequency comb as the center frequency, thus forming the optical frequency comb.

[0013] The first coupler divides the optical comb into frequency point number + 1 paths according to the actual required number of frequency points, and the extra path is the local oscillator optical path.

[0014] Under the control of the controller, the first to fourth optical filters select the required optical frequency comb sidebands as signal light according to the frequency hopping point and transmit them to the high-speed optical switch; the four optical filters select different frequencies.

[0015] The high-speed optical switch is controlled by the controller and switches the corresponding signal optical path output to the dual parallel Mach-Zehnder intensity modulator according to the frequency hopping pattern.

[0016] The third microwave source generates a baseband signal, which is converted into two radio frequency signals with a 90° phase difference after passing through a 90° mixer, and then transmitted to a dual parallel Mach-Zehnder intensity modulator.

[0017] The dual parallel Mach-Zehnder intensity modulator modulates the baseband signal onto the right sideband of the signal optical carrier through a carrier-suppressed single-sideband modulation mode;

[0018] Erbium-doped fiber amplifiers amplify the local oscillator light, increasing its optical power;

[0019] The second coupler couples the single-sideband modulation signal output from the dual parallel Mach-Zehnder intensity modulator with the local oscillator light from the erbium-doped fiber amplifier into a single path, which is then transmitted to the photodetector.

[0020] Photodetectors use optical heterodyne detection to beat a single-sideband signal with a local oscillator, achieving photo-to-electric conversion and generating a frequency-hopping signal.

[0021] A reconfigurable large-bandwidth frequency hopping method based on an optical frequency comb, implemented based on the reconfigurable large-bandwidth frequency hopping system based on an optical frequency comb as described above, includes the following steps:

[0022] The radio frequency signals generated by the first microwave source and the second microwave source in a frequency doubling relationship are respectively given to the first intensity modulator and the second intensity modulator;

[0023] The optical carrier generated by the laser is injected into the first intensity modulator to modulate the radio frequency signal onto the sideband, thereby generating a primary optical comb.

[0024] The primary optical comb is injected into the second intensity modulator, and a high-quality optical frequency comb is generated through secondary modulation.

[0025] Based on the actual number of frequency points, the high-quality optical frequency comb is split into multiple paths through the first coupler;

[0026] Under the control of the controller, the first to fourth optical filters select the required optical frequency comb sidebands as signal light according to the frequency hopping point and transmit them to the high-speed optical switch.

[0027] The optical filter selects the required optical comb in the local oscillator optical path and sends it to the erbium-doped fiber amplifier for amplification.

[0028] By using a high-speed optical switch, the optical path is selected according to the frequency hopping pattern to switch the signal light and transmit it to a dual parallel Mach-Zehnder intensity modulator.

[0029] The baseband signal generated by the third microwave source is split into beams, and then phase-shifted by a 90° mixer to generate a radio frequency signal with a 90° phase difference, which is then sent to a dual parallel Mach-Zehnder intensity modulator operating in carrier-suppressed single-sideband mode.

[0030] A single-sideband modulated signal is generated by modulating the baseband signal onto the right sideband of the signal light using a dual parallel Mach-Zehnder intensity modulator.

[0031] The single-sideband modulation signal is coupled to the local oscillator optical signal through a second coupler, and then input to a photodetector for optical heterodyne detection, thereby realizing the generation of frequency hopping signal and gainless amplification.

[0032] This invention brings about the following beneficial results:

[0033] 1. This invention generates a high-bandwidth, highly flat, reconfigurable, multi-tooth optical frequency comb by using frequency-doubled radio frequency to perform optical modulation on a cascaded modulator. This provides abundant optical spectrum resources for baseband signal frequency conversion, expands the frequency hopping bandwidth of the system, and realizes flexible and controllable frequency hopping points.

[0034] 2. This invention can achieve high-speed switching. By utilizing the large bandwidth and high-speed switching performance of currently commercial optical switches, 50ns-level switching can be achieved. By controlling the optical switch to switch channels according to the frequency hopping pattern through a microcontroller, nearly one million hops per second can be achieved.

[0035] 3. This invention can realize coherent detection reception. It utilizes the carrier suppression single-sideband operating mode of DPMZM to achieve single-sideband modulation, avoids the generation of redundant sidebands during the modulation process, and ensures the purity of the signal.

[0036] 4. This invention uses heterodyne detection to achieve gain-free amplification. It utilizes the local oscillator light amplified by the erbium-doped fiber amplifier to increase the gain of the frequency hopping signal generated after the beat frequency, thereby increasing the power of the frequency hopping signal. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a reconfigurable high-bandwidth frequency hopping system based on an optical frequency comb, as described in an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of a reconfigurable large bandwidth frequency hopping method based on an optical frequency comb, as described in an embodiment of the present invention.

[0039] Figure 3 This is a sideband diagram generated by single MZM modulation in an embodiment of the present invention.

[0040] Figure 4 This is a sideband diagram generated by cascaded MZM modulation in an embodiment of the present invention.

[0041] Figure 5 This is a schematic diagram of the frequency hopping signal in an embodiment of the present invention. Detailed Implementation

[0042] To enable those skilled in the art to understand the specific content of the present invention more concisely and clearly, the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] A reconfigurable wide-bandwidth frequency hopping system based on an optical frequency comb includes a laser, a first microwave source, a second microwave source, a third microwave source, a first coupler, a second coupler, a first intensity modulator, a second intensity modulator, a first optical filter, a second optical filter, a third optical filter, a fourth optical filter, a high-speed optical switch, a dual parallel Mach-Zehnder intensity modulator, a controller, a 90° mixer, a photodetector, and an erbium-doped fiber amplifier.

[0044] The optical carrier generated by the laser is input to a cascaded intensity modulator to generate a high-flatness, multi-tooth, high-quality optical frequency comb;

[0045] The local oscillator signal generated by the first microwave source is directly applied to the first intensity modulator;

[0046] The local oscillator signal generated by the second microwave source is directly applied to the second intensity modulator;

[0047] The first intensity modulator modulates the radio frequency signal generated by the first microwave source onto the optical carrier transmitted by the laser, and modulates ±1 and ±2 order sidebands with the optical carrier frequency as the center frequency to generate a high-flatness primary optical frequency comb, which then enters the second intensity modulator.

[0048] The second intensity modulator modulates the radio frequency signal generated by the second microwave source onto the primary optical frequency comb, and generates ±1 and ±2 order sidebands with each tooth of the output optical frequency comb as the center frequency, thus forming the optical frequency comb.

[0049] The first coupler divides the optical comb into frequency point number + 1 paths according to the actual required number of frequency points, and the extra path is the local oscillator optical path.

[0050] Under the control of the controller, the first to fourth optical filters select the required optical frequency comb sidebands as signal light according to the frequency hopping point and transmit them to the high-speed optical switch; the four optical filters select different frequencies.

[0051] The high-speed optical switch is controlled by the controller and switches the corresponding signal optical path output to the dual parallel Mach-Zehnder intensity modulator according to the frequency hopping pattern.

[0052] The third microwave source generates a baseband signal, which is converted into two radio frequency signals with a 90° phase difference after passing through a 90° mixer, and then transmitted to a dual parallel Mach-Zehnder intensity modulator.

[0053] The dual parallel Mach-Zehnder intensity modulator modulates the baseband signal onto the right sideband of the signal optical carrier through a carrier-suppressed single-sideband modulation mode;

[0054] Erbium-doped fiber amplifiers amplify the local oscillator light, increasing its optical power;

[0055] The second coupler couples the single-sideband modulation signal output from the dual parallel Mach-Zehnder intensity modulator with the local oscillator light from the erbium-doped fiber amplifier into a single path, which is then transmitted to the photodetector.

[0056] Photodetectors use optical heterodyne detection to beat a single-sideband signal with a local oscillator, achieving photo-to-electric conversion and generating a frequency-hopping signal.

[0057] This system generates high-quality optical frequency combs through cascaded intensity modulators, providing abundant spectrum resources for frequency hopping. Combined with commercial high-speed optical switches, it enables high-speed switching. Utilizing carrier-suppressed single-sideband modulation and heterodyne detection with dual parallel Mach-Zehnder modulators, it can generate reconfigurable, large-bandwidth frequency hopping signals.

[0058] like Figure 1As shown, the system can be divided into a high-quality optical comb generation module, a high-speed switching and selection module, and a coherent detection and receiving module. Among them:

[0059] The high-quality optical comb generation module utilizes cascaded modulators to generate optical frequency combs. A unique aspect of this generation method is that the radio frequency signals applied to the two cascaded MZMs (intensity modulators) are in a multiple relationship, achieving "slot-insertion" modulation. This generates a high-flatness, multi-tooth optical comb, solving the problems of poor tooth flatness and limited tooth count in same-frequency cascaded modulation. The process is as follows: When the laser emits an optical carrier with frequency f0, it is modulated by a high-frequency radio frequency signal f1 as it passes through the first MZM. By adjusting its bias point and radio frequency power, ±1 and ±2 order sidebands are generated with f0 as the center frequency and f1 as the repetition frequency, resulting in an optical frequency comb with 0.1dB flatness and 5 teeth. Subsequently, it passes through the second intensity modulator, where it is modulated by a low-frequency radio frequency signal f2. Adjusting its bias point and radio frequency power, ±1 and ±2 order sidebands are generated with f2 as the repetition frequency, resulting in an optical frequency comb with 3.5dB flatness and 25 teeth. By adjusting the frequencies of f1 and f2, the repetition rate of the optical frequency comb can be arbitrarily adjusted according to actual needs. For example, to achieve a 4GHz hopping step, f2 can be set to 4GHz and f1 to 20GHz. Considering that the maximum bandwidth of currently commercial intensity modulators is 70GHz, a maximum hopping step of 70GHz can be achieved, which fully meets the bandwidth requirements of different application scenarios. Regarding the number of hopping points, the number of intensity modulators can be reduced or increased according to actual needs to support different hopping points. For example, using only one MZM can achieve 5 frequency points, using three MZMs can achieve up to 125 frequency points, and so on. Therefore, the large bandwidth, reconfigurable optical frequency comb signal frequency hopping generated by this solution provides a rich frequency resource pool.

[0060] The high-quality optical comb is then input into the high-speed switching selection module. Based on the required number of frequency hopping points N, the corresponding number of channels N is selected. Optical filters are set on each channel to filter out the corresponding optical comb sidebands according to the frequency requirements of different frequency points. This then enters the high-speed optical switch, where a microcontroller controls the switch to select channels according to the frequency hopping pattern. Different optical comb teeth selected at different times are then sent to the coherent detection and receiving module. The bottom channel of this module is the local oscillator path. Similarly, optical filters are used to filter out suitable sidebands of the optical comb based on the required frequency difference of the frequency hopping signal, and these are then sent to the coherent detection and receiving module.

[0061] The coherent detection and receiving module transmits the optical carrier selected by the optical switch to a DPMZM (Dual Parallel Mach-Zehnder Modulator) operating in carrier-suppressed single-sideband mode, modulating the baseband signal onto the right sideband to complete the electro-optical conversion and obtain the signal light. Simultaneously, the optical comb selected by the local oscillator is amplified by an erbium-doped fiber amplifier to increase its power. Finally, the local oscillator and signal light are coupled together and input to a PD (Photodetector) for heterodyne detection to obtain a frequency-hopping signal and achieve gain-free amplification. In this module, an erbium-doped fiber amplifier can be added before the DPMZM to further enhance the gain.

[0062] A reconfigurable, high-bandwidth frequency hopping method based on optical frequency combs, such as... Figure 2 As shown, it includes the following steps:

[0063] The radio frequency signals generated by the first microwave source and the second microwave source in a frequency doubling relationship are respectively given to the first intensity modulator and the second intensity modulator;

[0064] The optical carrier generated by the laser is injected into the first intensity modulator to modulate the radio frequency signal onto the sideband, thereby generating a primary optical comb.

[0065] The primary optical comb is injected into the second intensity modulator, and a high-quality optical frequency comb is generated through secondary modulation.

[0066] Based on the actual number of frequency points, the high-quality optical frequency comb is split into multiple paths through the first coupler;

[0067] Under the control of the controller, the first to fourth optical filters select the required optical frequency comb sidebands as signal light according to the frequency hopping point and transmit them to the high-speed optical switch.

[0068] The optical filter selects the required optical comb in the local oscillator optical path and sends it to the erbium-doped fiber amplifier for amplification.

[0069] By using a high-speed optical switch, the optical path is selected according to the frequency hopping pattern to switch the signal light and transmit it to a dual parallel Mach-Zehnder intensity modulator.

[0070] The baseband signal generated by the third microwave source is split into beams, and then phase-shifted by a 90° mixer to generate a radio frequency signal with a 90° phase difference, which is then sent to a dual parallel Mach-Zehnder intensity modulator operating in carrier-suppressed single-sideband mode.

[0071] A single-sideband modulated signal is generated by modulating the baseband signal onto the right sideband of the signal light using a dual parallel Mach-Zehnder intensity modulator.

[0072] The single-sideband modulation signal is coupled to the local oscillator optical signal through a second coupler, and then input to a photodetector for optical heterodyne detection, thereby realizing the generation of frequency hopping signal and gainless amplification.

[0073] The system was simulated using Optisystem simulation software. The specific operation procedure is as follows:

[0074] Step 1: Determine the parameters of the laser, microwave source, MZM, power divider, etc.: Design the system with a maximum of 20 frequency points and a frequency hopping interval of 4 GHz. Select 4 frequency points, namely 8, 12, 16, and 20 GHz, for frequency hopping. The laser is in the 193 THz band with a power of 10 dB. The high-frequency and low-frequency microwave source signals are 25 GHz and 5 GHz, respectively, with normalized power, controlled by setting the bias voltage of the lithium niobate MZM. The half-wave voltage of both MZMs is 3.5 V, the bias point is set to ±0.55 V, and the modulation voltage is ±4.101. The baseband signal is 200 MHz with normalized power. The optical filters are set to 193.0082 THz, 193.0122 THz, 193.0162 THz, 193.0202 THz, and 193 THz from top to bottom. The frequency hopping rate of the optical switch is set to 50 ns. Observe the frequency hopping output pattern using an oscilloscope.

[0075] Step 2: An optical carrier is emitted using a 193THz laser, enters the first MZM, and after modulation by a 20GHz high-frequency radio frequency signal, generates highly flat ±1 and ±2 order sidebands with a repetition rate of 20GHz, which serve as the primary optical comb. Figure 3 As shown, the flatness of the optical frequency comb is 0.1dB and the number of comb teeth is 5.

[0076] Step 3: Using a second MZM modulator, modulate with a 4GHz low-frequency radio frequency signal, and expand ±1 and ±2 order sidebands centered on each tooth of the primary optical comb, thereby generating a highly flat optical comb tooth with a repetition rate of 4GHz. This serves as the optical domain spectrum resource pool for the frequency-hopping signal. Figure 4 As shown, the flatness of the optical frequency comb is 3.5dB and the number of comb teeth is 25.

[0077] Step 4: For the signal optical path, a tunable optical filter is used to select the corresponding sideband. A commercially available 50ns-level optical switch is used to quickly switch according to the frequency hopping pattern, achieving non-selective switching of the signal optical frequency. Subsequently, a dual parallel Mach-Zehnder intensity modulator operating in carrier-suppressed single-sideband mode is used to modulate the 200MHz baseband signal to the corresponding optical sideband via electro-optical conversion. In the local oscillator path, an optical filter is used to determine the selected sideband to be filtered out according to the required frequency hopping frequency, and then the power is amplified by an erbium-doped fiber amplifier.

[0078] Step 5: First, the signal optical path after carrier-suppressed single-sideband modulation and the local oscillator optical path after erbium-doped fiber amplifier amplification are combined using a coupler. Then, coherent reception is performed using a photodetector, and optical-to-electric conversion of the signal is achieved using optical heterodyne detection. Since the frequency of the output signal light switches depending on the selected channel of the optical switch, the RF signal obtained by heterodyne detection is also in a switching state, thereby realizing the generation of a frequency-hopping signal, such as... Figure 5 As shown, the different RF powers are distinguished by introducing different optical attenuations in different channels, thus representing 8.2 GHz, 12.2 GHz, 16.2 GHz, and 20.2 GHz respectively.

[0079] In summary, this invention provides frequency hopping points through a multi-tooth optical comb generated by a cascaded modulator, giving the structure the characteristics of reconfigurability, multiple frequency points, and large bandwidth; it utilizes a high-speed optical switch to achieve gating and switching of the signal optical channel, giving the structure the characteristics of high hopping speed; and all the components used in this system are commercially available, giving the structure high stability and good prospects for engineering applications.

[0080] The above description is merely a specific implementation of the present invention in the embodiments, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A reconfigurable, high-bandwidth frequency-hopping system based on an optical frequency comb, characterized in that, It includes a laser, a first microwave source, a second microwave source, a third microwave source, a first coupler, a second coupler, a first intensity modulator, a second intensity modulator, a first optical filter, a second optical filter, a third optical filter, a fourth optical filter, a high-speed optical switch, a dual parallel Mach-Zehnder intensity modulator, a controller, a 90° mixer, a photodetector, and an erbium-doped fiber amplifier. The optical carrier generated by the laser is input to a cascaded intensity modulator to generate a high-flatness, multi-tooth, high-quality optical frequency comb; The local oscillator signal generated by the first microwave source is directly applied to the first intensity modulator; The local oscillator signal generated by the second microwave source is directly applied to the second intensity modulator; The first intensity modulator modulates the radio frequency signal generated by the first microwave source onto the optical carrier transmitted by the laser, and modulates ±1 and ±2 order sidebands with the optical carrier frequency as the center frequency to generate a high-flatness primary optical frequency comb, which then enters the second intensity modulator. The second intensity modulator modulates the radio frequency signal generated by the second microwave source onto the primary optical frequency comb, and generates ±1 and ±2 order sidebands with each tooth of the output optical frequency comb as the center frequency, thus forming the optical frequency comb. The first coupler divides the optical frequency comb into the number of frequency points + 1 path according to the actual required number of frequency points. The extra path is the local oscillator optical path. Under the control of the controller, the first to fourth optical filters select the required optical frequency comb sidebands as signal light according to the frequency hopping point and transmit them to the high-speed optical switch. The four optical filters are selected with different frequencies; The high-speed optical switch is controlled by the controller and switches the corresponding signal optical path output to the dual parallel Mach-Zehnder intensity modulator according to the frequency hopping pattern. The third microwave source generates a baseband signal, which is converted into two radio frequency signals with a 90° phase difference after passing through a 90° mixer, and then transmitted to a dual parallel Mach-Zehnder intensity modulator. The dual parallel Mach-Zehnder intensity modulator modulates the baseband signal onto the right sideband of the signal optical carrier through a carrier-suppressed single-sideband modulation mode; Erbium-doped fiber amplifiers amplify the local oscillator light, increasing its optical power; The second coupler couples the single-sideband modulation signal output from the dual parallel Mach-Zehnder intensity modulator with the local oscillator light from the erbium-doped fiber amplifier into a single path, which is then transmitted to the photodetector. Photodetectors use optical heterodyne detection to beat a single-sideband signal with a local oscillator, achieving photo-to-electric conversion and generating a frequency-hopping signal.

2. A reconfigurable large-bandwidth frequency hopping method based on an optical frequency comb, characterized in that, The implementation based on the reconfigurable large-bandwidth frequency hopping system based on optical frequency comb as described in claim 1 includes the following steps: The radio frequency signals generated by the first microwave source and the second microwave source in a frequency doubling relationship are respectively given to the first intensity modulator and the second intensity modulator; The optical carrier generated by the laser is injected into the first intensity modulator to modulate the radio frequency signal onto the sideband, thereby generating a primary optical comb. The primary optical comb is injected into the second intensity modulator, and a high-quality optical frequency comb is generated through secondary modulation. Based on the actual number of frequency points, the high-quality optical frequency comb is split into multiple paths through the first coupler; Under the control of the controller, the first to fourth optical filters select the required optical frequency comb sidebands as signal light according to the frequency hopping point and transmit them to the high-speed optical switch. The optical filter selects the required optical comb in the local oscillator optical path and sends it to the erbium-doped fiber amplifier for amplification. By using a high-speed optical switch, the optical path is selected according to the frequency hopping pattern to switch the signal light and transmit it to a dual parallel Mach-Zehnder intensity modulator. The baseband signal generated by the third microwave source is split into beams, and then phase-shifted by a 90° mixer to generate a radio frequency signal with a 90° phase difference, which is then sent to a dual parallel Mach-Zehnder intensity modulator operating in carrier-suppressed single-sideband mode. A single-sideband modulated signal is generated by modulating the baseband signal onto the right sideband of the signal light using a dual parallel Mach-Zehnder intensity modulator. The single-sideband modulation signal is coupled to the local oscillator optical signal through a second coupler, and then input to a photodetector for optical heterodyne detection, thereby realizing the generation of frequency hopping signal and gainless amplification.

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