Device and method for generating optical single-side-band frequency shift with ultrahigh rejection ratio

Abstract

The invention provides an optical single-sideband frequency shift generation device and method with an ultrahigh rejection ratio, and the device comprises an optical frequency shift unit, an optical sideband phase modulation interference unit and a control unit, and employs an orthogonal Mach-Zehnder modulation structure to achieve the optical sideband frequency shift of 1.5 [mu] m waveband light waves. The optical signal after frequency shift contains a residual carrier and a residual sideband, and enters an optical sideband phase modulation interference unit at the moment. The optical sideband phase modulation interference unit adopts a two-stage phase modulation structure to respectively realize cancellation suppression of odd and even sidebands, the first stage adopts an optical fiber phase shifter and an adjustable optical fiber delay line to suppress an even-order sideband, and the second stage adopts an optical fiber phase shifter and an adjustable optical fiber delay line to suppress an odd-order sideband. And the control unit respectively adjusts the phase change amount of the optical fiber phase shifter and the delay amount of the adjustable optical fiber delay, and finally outputs an optical single side band frequency shift signal with an ultrahigh suppression ratio. According to the invention, the suppression ratio of each sideband of a radio frequency signal in any modulation format can be increased by more than 20dB.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of space large dynamic light information transmission, and particularly relates to an optical single sideband frequency shift generation device and a generation method with super-high suppression ratio. BACKGROUND

[0002] 6G information network is the next generation of national strategic information infrastructure, and can realize high-speed interconnection and intercommunication between space, sky, land and sea information nodes. Laser is used as a carrier to realize information transmission, which is an important means for realizing high-speed interconnection and intercommunication between nodes. Satellite laser communication technology is developed by various countries in the world as a means of high-speed interconnection of space information nodes. For example, a large number of laser communication terminals are deployed on the “Starlink” constellation of the United States to realize space high-speed information data transmission. The EDRS relay link system of Europe also establishes laser communication between high-orbit constellation and low-orbit constellation. China will also build a laser communication transmission network in the construction of the Star Network constellation to realize high data rate and large capacity space information transmission.

[0003] Then, since the space nodes (such as satellites, air platforms, aircrafts) are not fixed nodes in the space network, they always move along the orbit route, so that the relative motion speed causes the Doppler frequency shift effect of the laser light wave when laser communication or laser detection is carried out between two space nodes. Therefore, when the space laser communication terminal is tested on the ground, the Doppler frequency shift condition in space needs to be simulated for equivalent test. At present, single sideband frequency shift can be realized based on Mach-Zehnder interference structure. This method uses a Mach-Zehnder modulator as a core device. Since the extinction ratio of the device can only reach about 20 dB, after single sideband frequency shift is generated, the carrier and the remaining sideband suppression ratio is usually about 20 dB. At the same time, if the carrier suppression ratio is improved, the remaining sideband suppression ratio will be reduced, and the carrier suppression ratio and the remaining sideband suppression ratio cannot be improved at the same time. This has a great influence on the carrier tracking and transmission sensitivity of the whole communication system. SUMMARY

[0004] In order to solve the above problems in the prior art, the application provides an optical single sideband frequency shift generation device and a generation method with super-high suppression ratio. The technical problems to be solved by the application are solved by the following technical scheme: An optical single sideband frequency shift generation device with super-high suppression ratio comprises an optical frequency shift unit, an optical sideband phase modulation interference unit and a control unit. The optical frequency shift unit is used for performing optical sideband frequency shift on an input radio frequency signal based on a quadrature Mach-Zehnder modulation structure under the control of the control unit, to obtain a frequency-shifted optical signal; wherein the frequency-shifted optical signal contains a residual carrier and a residual sideband. The optical sideband phase modulation interference unit is used for suppressing the residual carrier and the residual sideband contained in the frequency-shifted optical signal by adopting a two-stage phase modulation structure under the control of the control unit, so as to obtain an optical single sideband signal.

[0005] An optical single sideband frequency shift generation method with super-high suppression ratio, which is implemented by using an optical single sideband frequency shift generation device with super-high suppression ratio, comprises the following steps of: The control unit is used for generating a control voltage for controlling the optical frequency shift unit and the optical sideband phase modulation interference unit; The optical frequency shift unit is used for performing optical sideband frequency shift on an input radio frequency signal based on a quadrature Mach-Zehnder modulation structure under the action of the control voltage, so as to obtain a frequency-shifted optical signal; wherein the frequency-shifted optical signal contains a residual carrier and a residual sideband; The optical sideband phase modulation interference unit is used for suppressing the residual carrier and the residual sideband contained in the frequency-shifted optical signal by adopting a two-stage phase modulation structure under the action of the control voltage, so as to obtain an optical single sideband signal. 1) The present application can realize optical single sideband frequency shift with super-high suppression ratio and extremely high precision simulation of spatial laser Doppler frequency shift process. Limited by the extinction ratio performance of conventional optical modulators, the use of a quadrature Mach-Zehnder modulator to realize single sideband frequency shift at a wavelength of 1.5 μm will carry a residual carrier and multiple residual sidebands. Therefore, the present application takes the required +1 order frequency shift as a reference wavelength, and through a first-stage optical sideband phase modulation interference, the odd-order sideband wavelengths can be greatly suppressed, and through a second-stage optical sideband phase modulation interference, the even-order sideband wavelengths can be greatly suppressed. After two-stage optical sideband phase modulation interference, the optical power of the +1 order frequency shift is theoretically lost, and the optical power of the residual carrier and multiple residual sidebands is greatly attenuated, so that an optical single sideband signal with super-high suppression ratio can be completely realized. Compared with the traditional method of using only a quadrature Mach-Zehnder modulator for frequency shift, the device of the present application can improve the suppression ratio of the +1 order frequency shift to the carrier and the remaining sidebands by more than 30 dB.

[0006] 2) The present application can simulate the Doppler effect of spatial relative motion under strong background noise conditions. Since the suppression ratio of the present application to the carrier and the residual sideband is extremely high, effective Doppler frequency optical signal detection can still be realized under strong background noise, and the Doppler simulation can be adapted to a wide range of distances and large-scale spatial motion.

[0007] 3) The present application can support optical single sideband frequency shift simulation with super-high suppression ratio for multiple modulation formats. Since the present application adopts a sideband frequency shift method, the modulation information will not be lost, so the input 1.5 μm wavelength optical signal can be continuous wave or contain any modulation format signal.

[0008] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of an optical single-sideband frequency shifter with ultra-high suppression ratio provided by the present invention; Figure 2 This is a schematic diagram of the internal structure of the orthogonal Mach-Zehnder modulator provided by the present invention; Figure 3 This is a schematic diagram of the spectrum before and after residual carrier and residual sideband suppression provided by the present invention. Detailed Implementation

[0010] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0011] In order for laser communication systems to operate normally under space optical Doppler simulation conditions, it is necessary to achieve high suppression ratios for both the carrier and other sidebands during optical single-sideband frequency shifting. However, there is currently no optical single-sideband frequency shifting generation device or method that can simultaneously achieve high suppression ratios for both the carrier and other sidebands.

[0012] refer to Figure 1 and Figure 2 In a first aspect, the present invention provides an optical single-sideband frequency shifting generation device with ultra-high suppression ratio, comprising an optical frequency shifting unit, an optical sideband phase modulation interference unit, and a control unit; The optical frequency shifting unit is used, under the control of the control unit, to perform optical sideband shifting on the input radio frequency signal based on an orthogonal Mach-Zehnder modulation structure to obtain a frequency-shifted optical signal; wherein the frequency-shifted optical signal contains a residual carrier and a residual sideband. The optical sideband phase modulation interference unit is used, under the control of the control unit, to suppress the residual carrier and residual sideband contained in the frequency-shifted optical signal using a two-stage phase modulation structure, thereby obtaining an optical single-sideband signal.

[0013] refer to Figure 1 As shown, the optical frequency shifting unit of the present invention includes a tunable laser, a frequency shift signal source, a radio frequency phase shifter, a first analog amplifier, a second analog amplifier, a quadrature Mach-Zehnder modulator, and a DC voltage converter; in Figure 1 The first and second analog amplifiers are denoted as analog amplifier A and analog amplifier B, respectively.

[0014] The output end of the tunable laser is connected with the input end of the quadrature Mach-Zehnder modulator, the output end of the frequency shift signal source is connected with the input end of the radio frequency phase shifter, the input end of the analog amplifier A and the input end of the analog amplifier B, the output ends of the analog amplifier A and the analog amplifier B are connected with two radio frequency ports of the quadrature Mach-Zehnder modulator, the input end of the quadrature Mach-Zehnder modulator is connected with the output end of the direct current voltage device, and the input end of the radio frequency phase shifter is connected with the output end of the control unit.

[0015] The function of the optical frequency shift unit is to realize optical single sideband frequency shift of 1.5 mu m wave band.

[0016] Specifically, the frequency shift signal source generates a radio frequency signal changing with time under the control of the control unit and sends the radio frequency signal into the radio frequency phase shifter. The radio frequency phase shifter carries out phase shift on the radio frequency signal to obtain two quadrature frequency shift signals, and sends one of the two frequency shift signals into the analog amplifier A and the other frequency shift signal into the analog amplifier B. The analog amplifier A and the analog amplifier B both carry out analog amplification on the input frequency shift signals to obtain two amplified signals, and synchronously send the two amplified signals into the quadrature Mach-Zehnder modulator. The direct current voltage device provides a bias voltage for the quadrature Mach-Zehnder modulator. The quadrature Mach-Zehnder modulator modulates the two amplified signals to obtain a frequency shifted optical signal and sends the frequency shifted optical signal into the optical sideband phase modulation interference unit.

[0017] The direct current voltage device can provide a voltage adapting a phase working point for the quadrature Mach-Zehnder modulator. The 1.5 mu m wave band optical wave with a center wavelength of 1.5 mu m passes through the quadrature Mach-Zehnder modulator and realizes optical sideband frequency shift based on the quadrature Mach-Zehnder modulation structure. The frequency shifted optical signal is

[0018] The application can support optical single sideband frequency shift analog with super high suppression ratio of multiple modulation formats. Since the application adopts sideband frequency shift mode, the input 1.5 mu m wave band optical signal can be continuous wave or can contain signals with arbitrary modulation formats, such as intensity optical signal (OOK), phase optical signal (BPSK) and high-order modulation optical signal (QPSK, 16QAM, 64QAM). Reference Figure 1The optical sideband phase modulation interference unit of the present invention includes a first optical coupler, a first fiber phase shifter, a first adjustable fiber delay line, a second optical coupler, a third optical coupler, a second adjustable fiber delay line, a second fiber phase shifter, and a fourth optical coupler. The first to fourth optical couplers are in Figure 2 In the diagram, optical coupler 1, optical coupler 2, optical coupler 3 and optical coupler 4 are respectively referred to as optical coupler 1 and optical coupler 2, the first fiber phase shifter and the second fiber phase shifter are respectively referred to as fiber phase shifter 1 and fiber phase shifter 2, the first adjustable fiber delay line and the second adjustable fiber delay line are respectively referred to as adjustable fiber delay line 1 and adjustable fiber delay line 2.

[0019] The output of the optical frequency shifting unit is connected to the input of the optical coupler 1. The optical coupler 1 outputs two optical waves to the fiber phase shifter 1 and the adjustable fiber delay line 1, respectively. The outputs of the fiber phase shifter 1 and the adjustable fiber delay line 1 are connected to the input of the optical coupler 2. The output of the optical coupler 2 is connected to the input of the optical coupler 3. The output of the optical coupler 3 is connected to the input of the fiber phase shifter 2 and the adjustable fiber delay line 2. The outputs of the fiber phase shifter 2 and the adjustable fiber delay line 2 are connected to the input of the optical coupler 4. The output of the optical coupler outputs an optical single-sideband signal.

[0020] Specifically, the optical coupler 1 splits the frequency-shifted optical signal into two optical waves, path A and path B; The fiber phase shifter 1 shifts the phase of the A-path light wave to obtain the C-path light wave; The adjustable fiber delay line 1 delays the B-path light wave to obtain the D-path light wave. The optical coupler 2 couples the C-path and D-path light waves to obtain the E-path light wave; The optical coupler 3 divides the E-path light wave into the F-path and H-path light waves; The fiber phase shifter 2 shifts the phase of the F-path light wave to obtain the I-path light wave; The adjustable fiber delay line 2 delays the H-path light wave to obtain the G-path light wave. The optical coupler 4 couples the I-path and G-path light waves to obtain an optical single-sideband signal.

[0021] The delay amount of the adjustable fiber delay line 1 With the frequency of the radio frequency signal f s satisfy relation; The phase change of the fiber phase shifter 1 Phase change introduced by tunable fiber delay line 1 Same; the delay amount of the adjustable fiber delay line 2 and f s satisfy relation; The phase change of the fiber phase shifter 2 Phase change introduced by tunable fiber delay line 2 The optical path difference between the optical path from path B to path D and the optical path from path A to path C is equal to the optical delay of adjustable fiber delay line 1; the optical path difference between the optical path from path H to path G and the optical path from path F to path I is equal to the optical delay of adjustable fiber delay line 2.

[0022] The power coupling ratios of optical couplers 1, 2, 3, and 4 are all between 49.5% and 50.5%.

[0023] The delay adjustment range of adjustable fiber delay line 1 and adjustable fiber delay line 2 is between 0 and 1 μs.

[0024] The phase change of fiber phase shifter 1 and fiber phase shifter 2 is between 0° and 360°.

[0025] The phase imbalance range of the RF phase shifter is within ±10°.

[0026] The 1.5μm band tunable laser outputs linearly polarized light with a wavelength tuned between 1.52μm and 1.58μm. The adjustable fiber delay line 1 and the adjustable fiber delay line 2 can be either fiber-type or spatial structure. The fiber phase shifter 1 and the fiber phase shifter 2 are any one of a phase modulator, a fiber stretcher, and an optical delay line.

[0027] The working process of the optical sideband phase modulation interferometer unit is as follows: the frequency-shifted optical signal The light waves are split into two paths, A and B, by optical coupler 1. Using the reference wavelength, the remaining residual carrier and residual sideband wavelengths can be considered as sidebands. Path A light wave reaches path C through fiber phase shifter 1, and path B light wave reaches path D through adjustable fiber delay line 1. The odd-numbered sidebands are matched by adjusting adjustable fiber delay line 1, and simultaneously adjusting fiber phase shifter 1 to match... The reference wavelength is used. At this point, the C-path and D-path optical waves, after coupling through optical coupler 2, will have a destructive interference suppression effect on the odd-numbered sidebands. The coupled output E-path optical wave enters optical coupler 3 and is split into F-path and H-path optical waves. The F-path optical wave reaches path I after passing through fiber phase shifter 2, and the H-path optical wave reaches path G after passing through adjustable fiber delay line 2. The even-numbered sidebands are matched by adjusting the adjustable fiber delay line 2, and simultaneously adjusting the fiber phase shifter 2 to match... Using the reference wavelength, the I-path and G-path optical waves are coupled through optical coupler 4. This coupling process will cause destructive interference to the even-order sidebands. Therefore, through two optical sideband phase modulation interferences, the even-order and odd-order sidebands can be suppressed respectively, while the required... Using two reference wavelengths, and with both processes involving constructive interference, an ultra-high suppression ratio optical single-sideband signal is achieved.

[0028] In addition, the control unit controls the delay of adjustable fiber delay line 1 and adjustable fiber delay line 2 to adapt to odd and even sidebands, and controls fiber phase shifter 1 to achieve precise phase adjustment between C-path and D-path optical waves, and controls fiber phase shifter 2 to achieve precise phase adjustment between I-path and G-path optical waves, ultimately achieving ultra-high suppression ratio optical single-sideband signal output.

[0029] The working principle of the optical single-sideband frequency shifter with ultra-high suppression ratio provided by this invention is as follows: In the optical frequency shifting unit, a 1.5μm band tunable laser is set to output a continuous optical carrier, the wavelength of which is defined as λ1 (corresponding to a frequency of...). f 1. Angular frequency is The frequency of the radio frequency signal generated by the frequency shift signal source is set to... f s (angular frequency is) Since the 1.5μm laser outputs a continuous optical carrier, its optical field expression can be given as: (1) in, This represents the amplitude of the light field. For example... Figure 3 As shown, the quadrature Mach-Zehnder modulator contains two sub-modulators, 1 and 2, and an optical phase shifter. To achieve carrier-suppressed single-sideband frequency shift, the two sub-modulators operate at the minimum power transmission point. The DC voltage converter outputs three voltages, two of which are applied to the two sub-modulators, and the DC bias voltage is equal to the half-wave voltage. V π The RF phase shifter outputs two RF signals of the same frequency with a 90° phase difference. One of these signals, after being amplified by analog amplifier A, has a voltage of... V A The electrical signal loaded onto the upper arm of sub-modulator 1 is: (2) The voltage produces its phase change as: (3) where, is the modulation index. After the upper arm modulation of the sub-modulator 1, the output light field expression is: (4) According to the identity of the Bessel function as follows: (5) Substitute equation (5) into equation (4) and simplify, by considering smaller order (n n less than 3), other can be ignored, the light field expression is as follows: (6) Similarly, for the lower arm of the sub-modulator 1 to sample the same way to expand, the lower arm of the voltage applied , its phase change is: (7) The output light field is: (8) Generally, the extinction ratio of the quadrature Mach-Zehnder modulator is about 15~25dB, the extinction ratios of the main modulator, the sub-modulator 1 and the sub-modulator 2 are defined as , and , the splitting ratios are , and The splitting ratio and the extinction ratio have the following relationship: (9) Therefore, the output light signals of the sub-modulator 1 and the sub-modulator 2 and can be expressed as: (10) (11) At the same time, the phase shift between the sub-modulator 1 and the sub-modulator 2 is set as , the final superposition light field expression is as follows: (12) Substitute equation (10), (11) into equation (12), use the Bessel function expansion, ignore the high-order sidebands greater than 4, the light field output by the quadrature Mach-Zehnder modulator can be expressed as: (13) wherein, is a Bessel function of the first kind, is a modulation index.

[0030] As can be seen from equation (13), the frequency shift process produces not only the desired +1st order, but also extra 0th order (carrier), -1st order, ±2nd order, ±3rd order, etc. sidebands. When the optical field is split into A-path and B-path optical waves by optical coupler 1, the phase change introduced by the A-path optical wave passing through the fiber phase shifter 1 is and the A-path optical wave reaches the C-path. The delay introduced by the B-path optical wave passing through the tunable fiber delay line 1 is and the phase change introduced by the B-path optical wave is The two-port optical field output by the C-path and D-path optical waves after coupling by optical coupler 2 can be expressed as follows: (14) wherein, is the splitting ratio of fiber coupler 1, is the splitting ratio of fiber coupler 2. is the frequency corresponding to the aforementioned +1st order frequency-shifted sideband. is the frequency of other order sidebands, wherein n can take values of 0, -1, ±2, ±3, ±4. Further simplification can be obtained as follows: (15) Since the E-path optical wave is a single-port, the upper part factor in equation (14) is taken as the optical field of the E-path optical wave, i.e.: (16) When the frequency shift signal source outputs a radio frequency signal with a frequency of f s the interval between the +1st order sideband frequency is f s Even multiple sidebands are defined as the first type of sidebands, with a frequency of ignoring high-order sidebands, wherein k can take values of -2, -1, 1, 2, etc.; similarly, the interval between the +1st order sideband frequency is f s Odd multiple sidebands are defined as the second type of sidebands, with a frequency of ignoring high-order sidebands, wherein k can take values of -3, -2, -1, 0, 1, 2, etc. Adjusting the delay of the tunable fiber delay line 1 and fs satisfies the phase change amount of the optical fiber phase shifter 1 the phase change amount introduced by the adjustable optical fiber delay line 1 the same, the first type and the second type of sideband frequency are respectively brought into the formula (16) , the following formula is obtained: (17) (18) Since the splitting ratio and are close to 50%, the following can be obtained: (19) (20) It can be seen that the first type of sideband light field is almost equal to 0, and the second type of sideband light field almost does not change, so the E path light field formed by coupling after the optical fiber phase shifter 1 and the adjustable optical fiber delay line 1 suppresses the first type of sideband. Similarly, by adjusting the delay amount of the adjustable optical fiber delay line 2 f s satisfies , the phase change amount of the optical fiber phase shifter 2 and the phase change amount introduced by the adjustable optical fiber delay line 2 are simultaneously adjusted, the light field output by the optical coupler 4 will suppress the second type of sideband, that is . Therefore, by two-stage phase modulation interference, the first type of sideband and the second type of sideband are suppressed in turn, only the required +1 order sideband is reserved, and the sideband suppression ratio is improved comprehensively.

[0031] As shown in Figure 3 , the residual carrier and the residual sideband suppression before and after the spectrum are shown in Figure 3 , which can verify that the super-high suppression ratio optical single sideband frequency shift generation device of the application can effectively suppress the residual carrier and the residual sideband.

[0032] In a second aspect, the application provides a super-high suppression ratio optical single sideband frequency shift generation method, which is realized by using the super-high suppression ratio optical single sideband frequency shift generation device of the first aspect, and the super-high suppression ratio optical single sideband frequency shift generation method comprises: generating a control voltage for controlling the optical frequency shift unit and the optical sideband phase modulation interference unit by using the control unit; The light frequency shift unit is used to perform optical sideband frequency shift on the input radio frequency signal based on the orthogonal Mach-Zehnder modulation structure under the action of the control voltage, and a frequency-shifted optical signal is obtained; wherein the frequency-shifted optical signal contains residual carrier and residual sideband; The optical sideband phase modulation interference unit is used to suppress the residual carrier and residual sideband contained in the frequency-shifted optical signal by adopting a two-stage phase modulation structure under the action of the control voltage, and an optical single sideband signal is obtained.

[0033] The super-high suppression ratio optical single sideband frequency shift generation method of the application uses a super-high suppression ratio optical single sideband frequency shift generation device, and the process is as follows: in the optical frequency shift unit, 1.5 μm band optical waves with a center wavelength of are passed through an orthogonal Mach-Zehnder modulator, and a time-varying frequency signal output by a frequency shift signal source is shifted to two orthogonal frequency shift signals after passing through a radio frequency phase shifter. The two orthogonal frequency shift signals are synchronously sent into the orthogonal Mach-Zehnder modulator after passing through an analog amplifier A and an analog amplifier B. A direct current voltage device provides an adaptive phase operating point voltage for the orthogonal Mach-Zehnder modulator, and on this basis, the output end of the orthogonal Mach-Zehnder modulator generates an optical single sideband frequency shift process containing residual sideband and residual carrier. In the optical sideband phase modulation interference unit, the frequency-shifted optical waves are equally divided into two paths, i.e. A path and B path, after passing through an optical coupler 1, wherein the A path reaches the C path after passing through a fiber phase shifter 1, and the B path reaches the D path after passing through an adjustable fiber delay line 1. The C path and the D path are coupled by an optical coupler 2 and output from the E path. The E path reaches an optical coupler 3 and is divided into two optical waves, i.e. F path and H path, wherein the F path reaches the I path after passing through a fiber phase shifter 2, and the H path reaches the G path after passing through an adjustable fiber delay line 2. The I path and the G path are coupled by an optical coupler 4 and output, i.e. output a super-high suppression ratio optical single sideband signal. The control unit controls the frequency shift signal source to simulate the current frequency shift value and the change rate, controls the frequency of the 1.5 μm band tunable laser, and controls the phase change amount of the fiber phase shifter and the delay amount of the adjustable fiber delay line.

[0034] The method of the application can be implemented according to the following steps: Step 1, the control unit sets the frequency shift value output by the frequency shift signal source, and can also set the frequency shift change rate and change direction. In addition, the control unit controls the 1.5 μm band tunable laser to output continuous light with a wavelength of .

[0035] Step 2, the frequency shift signal source outputs a radio frequency signal and inputs to the input end of the radio frequency phase shifter, the radio frequency phase shifter outputs two paths of quadrature radio frequency signals with a phase difference of 90°, the two paths of quadrature radio frequency signals are amplified by the analog amplifier A and the analog amplifier B respectively, and then are connected to the radio frequency port of the quadrature Mach-Zehnder modulator Continuous light is also connected to the optical input port of the quadrature Mach-Zehnder modulator. The DC voltage output by the DC voltage generator is connected to the DC port of the quadrature Mach-Zehnder modulator, so that it works in a single sideband frequency shift mode to generate a frequency shift light wave And carries a residual carrier and a residual sideband.

[0036] Step 3, the frequency shift light wave is equally divided into two paths of light waves, i.e. A path and B path, wherein the A path reaches the C path after passing through the optical fiber phase shifter 1, and the B path reaches the D path after passing through the adjustable optical fiber delay line 1. The C path and the D path are coupled by the optical coupler 2 and output from the E path.

[0037] Step 4, the E path light wave reaches the optical coupler 3 and is divided into two paths of light waves, i.e. F path and H path, the F path light wave reaches the I path after passing through the optical fiber phase shifter 2, and the H path reaches the G path after passing through the adjustable optical fiber delay line 2. The I path and the G path are coupled by the optical coupler 4 and output a path of light signals.

[0038] Step 5, the control unit controls the phase change amount of the optical fiber phase shifter 1 and the delay amount of the optical fiber adjustable optical fiber delay line 1 to realize suppression of even sidebands, controls the phase change amount of the optical fiber phase shifter 2 and the delay amount of the adjustable optical fiber delay line 2 to suppress odd sidebands, and finally realizes an ultra-high suppression ratio optical single sideband signal output.

[0039] It is worth noting that the terms "first" and "second" in the present application are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0040] The above is a further detailed description of the present application in combination with specific preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be considered as falling within the protection scope of the present application.

Claims

1. An optical single sideband frequency shift generation apparatus with ultra-high suppression ratio, characterized by, The device comprises a light frequency shift unit, an optical sideband phase modulation interference unit and a control unit. The light frequency shift unit is configured to perform optical sideband frequency shift on an input radio frequency signal based on a quadrature Mach-Zehnder modulation structure under the control of the control unit to obtain a frequency-shifted light signal, wherein the frequency-shifted light signal contains a residual carrier and a residual sideband. The optical sideband phase modulation interference unit is configured to suppress the residual carrier and the residual sideband contained in the frequency-shifted light signal by using a two-stage phase modulation structure under the control of the control unit to obtain an optical single sideband signal.

2. The super-high suppression ratio optical single sideband frequency shift generation apparatus according to claim 1, wherein The light frequency shift unit comprises a tunable laser, a frequency shift signal source, a radio frequency phase shifter, a first analog amplifier, a second analog amplifier, a quadrature Mach-Zehnder modulator and a direct current voltage device. The output end of the tunable laser is connected to the input end of the quadrature Mach-Zehnder modulator, the output end of the frequency shift signal source is connected to the input end of the radio frequency phase shifter, the input end of the first analog amplifier and the input end of the second analog amplifier, the output ends of the first analog amplifier and the second analog amplifier are connected to the two radio frequency ports of the quadrature Mach-Zehnder modulator, the input end of the quadrature Mach-Zehnder modulator is connected to the output end of the direct current voltage device, and the input end of the radio frequency phase shifter is connected to the output end of the control unit.

3. The optical single sideband frequency shift generation device with ultra-high suppression ratio according to claim 2, wherein The frequency shift signal source generates a radio frequency signal varying with time under the control of the control unit and sends it to the radio frequency phase shifter; The radio frequency phase shifter performs phase shift on the radio frequency signal to obtain two quadrature frequency shift signals, and sends one of the two frequency shift signals to the first analog amplifier and the other to the second analog amplifier; The first analog amplifier and the second analog amplifier both perform analog amplification on the input frequency shift signal to obtain two amplified signals, and send the two amplified signals to the quadrature Mach-Zehnder modulator synchronously; The direct current voltage device provides a bias voltage for the quadrature Mach-Zehnder modulator; The quadrature Mach-Zehnder modulator modulates the two amplified signals to obtain a frequency-shifted light signal and sends it to the optical sideband phase modulation interference unit.

4. The super-high suppression ratio optical single sideband frequency shift generation apparatus according to claim 2, wherein The optical sideband phase modulation interference unit comprises a first optical coupler, a first optical fiber phase shifter, a first adjustable optical fiber delay line, a second optical coupler, a third optical coupler, a second adjustable optical fiber delay line, a second optical fiber phase shifter and a fourth optical coupler. The output end of the light frequency shift unit is connected to the input end of the first optical coupler, the first optical coupler outputs two light waves to the first optical fiber phase shifter and the first adjustable optical fiber delay line, the output ends of the first optical fiber phase shifter and the first adjustable optical fiber delay line are correspondingly connected to the input ends of the second optical coupler, the output end of the second optical coupler is connected to the input end of the third optical coupler, the output end of the third optical coupler is correspondingly connected to the input ends of the second optical fiber phase shifter and the second adjustable optical fiber delay line, and the output ends of the second optical fiber phase shifter and the second adjustable optical fiber delay line are connected to the input end of the fourth optical coupler, and the output end of the optical coupler outputs an optical single sideband signal.

5. The optical single sideband frequency shift generation device with ultra-high suppression ratio according to claim 4, wherein the first optical coupler divides the frequency-shifted optical signal into two light waves of A path and B path; the first optical fiber phase shifter phase-shifts the A path light wave to obtain C path light wave; the first adjustable optical fiber delay line time delays the B path light wave to obtain D path light wave; the second optical coupler couples the C path and D path light waves to obtain E path light wave; the third optical coupler divides the E path light wave into F path and H path light waves; the second optical fiber phase shifter phase-shifts the F path light wave to obtain I path light wave; the second adjustable optical fiber delay line time delays the H path light wave to obtain G path light wave; and the fourth optical coupler couples the I path and G path light waves to obtain an optical single sideband signal.

6. The optical single sideband frequency shift generation device with ultra-high suppression ratio according to claim 4, wherein the optical path difference between the optical path of B path to D path and the optical path of A path to C path is equal to the optical delay of the first adjustable optical fiber delay line; and the optical path difference between the optical path of H path to G path and the optical path of F path to I path is equal to the optical delay of the second adjustable optical fiber delay line. The power coupling ratios of the first optical coupler, the second optical coupler, the third optical coupler and the fourth optical coupler are all between 49.5% and 50.5%. The first adjustable optical fiber delay line and the second adjustable optical fiber delay line are any one of fiber type and space type structure; and the first optical fiber phase shifter and the second optical fiber phase shifter are any one of phase modulator, fiber stretcher and optical delay line. The optical single sideband frequency shift generation method using the optical single sideband frequency shift generation device with ultra-high suppression ratio according to any one of claims 1 to 9 comprises: generating, by the control unit, control voltage for controlling the light frequency shift unit and the optical sideband phase modulation interference unit; under the action of the control voltage, performing, by the light frequency shift unit, optical sideband frequency shift on the input radio frequency signal based on a quadrature Mach-Zehnder modulation structure to obtain a frequency-shifted optical signal; wherein the frequency-shifted optical signal contains residual carrier and residual sideband. ​ ​ ​ a delay of the first tunable fiber delay line a frequency of the radio frequency signal f s satisfies a relationship The phase change amount of the optical fiber phase shifter 1 The phase change amount introduced by the first tunable optical fiber delay line The same; the delay amount of the second tunable optical fiber delay line The phase change amount introduced by the second tunable optical fiber delay line f s Satisfies The relationship; The phase change amount of the optical fiber phase shifter 2 The phase change amount introduced by the second tunable optical fiber delay line is the same.

7. The super-high suppression ratio optical single sideband frequency shift generation apparatus according to claim 4, wherein ​ 8. The super-high suppression ratio optical single sideband frequency shift generation apparatus according to claim 4, wherein ​ 9. The super-high suppression ratio optical single sideband frequency shift generation apparatus according to claim 4, wherein ​ 10. A method for optical single sideband frequency shift generation with ultra-high suppression ratio, characterized in that, ​ ​ ​ The optical sideband phase modulation interference unit is used to suppress the residual carrier and the residual sideband contained in the frequency-shifted optical signal by using a two-stage phase modulation structure under the action of the control voltage, so as to obtain an optical single sideband signal.

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