An optical domain self-interference cancellation and anti-dispersion transmission device and method

Abstract

Provided is an optical-domain self-interference cancellation and dispersion-resistant transmission method, including the following steps: An optical carrier is injected into a PDM-DPMZM (2), and is modulated by a received signal, a reference signal, and a local oscillator signal in the PDM-DPMZM (2) to generate an optical carrier radio frequency signal; After the optical carrier radio frequency signal is output from the PDM-DPMZM (2), it is introduced into a dispersion phase through a single-mode optical fiber (4) and undergoes long-distance transmission, and is injected into an optical power amplifier (5) to achieve power amplification; The optical carrier radio frequency signal after fiber transmission and optical power amplification undergoes polarization beam splitting, delay matching, and photoelectric conversion to achieve phase-intensity modulation conversion, eliminate the self-interference signal, and compensate for the dispersion-induced power fading effect. Also provided is an optical-domain self-interference cancellation and dispersion-resistant transmission device based on this method. The present invention utilizes double-sideband modulation and the dispersion effect to achieve phase-intensity modulation conversion, and can achieve self-interference cancellation without relying on electrical tuning devices, electrical couplers, and optical filters, and the cancellation performance is not affected by fiber transmission.

Description

Technical Field

[0001] The present invention relates to the field of microwave photonic signal processing, and particularly to an optical domain self-interference cancellation and anti-dispersion transmission device and method. Background Art

[0002] In-band full-duplex technology can achieve simultaneous transmission and reception of data within the same frequency band. Compared with traditional duplex technologies, it can theoretically improve spectrum utilization, network capacity, and system throughput, and is a key technology for the current fifth-generation mobile communication technology (5G) and future wireless communication systems. However, in-band full-duplex systems currently face the problem of self-interference or co-location interference. Due to limited antenna isolation capabilities, the receiving antenna will receive strong co-frequency interference signals emitted by adjacent transmitting antennas, resulting in the received signal being overwhelmed and the useful signal unable to be detected, greatly reducing communication performance. Since the leaked interference signal and the antenna received signal occupy the same frequency band, it cannot be simply filtered using narrowband filters or notch filters. If this co-frequency self-interference signal can be eliminated, the signal-to-noise ratio and system communication efficiency will be improved, further alleviating the current network congestion problem. Traditional radio frequency (RF) domain self-interference cancellation technologies include the antenna domain, analog domain, and digital domain. Among them, RF analog domain self-interference cancellation is one of the most effective methods and has been widely studied in recent years. However, due to problems such as limited bandwidth of traditional electronic devices, severe nonlinear effects, sensitivity to electromagnetic interference, and poor flexibility, the performance and development of RF self-interference systems are restricted.

[0003] Microwave photonics uses photonic methods to improve the generation, distribution, processing, and control capabilities of RF signals, and has inherent characteristics such as ultra-wide bandwidth, electromagnetic interference resistance, and flexible operation, playing a huge advantage in the field of wireless communication. Using microwave photonics technology to achieve self-interference cancellation can effectively solve the bottleneck problems existing in electrical RF self-interference systems and has become the focus of attention. Currently, some of the photonics-based analog domain self-interference cancellation schemes rely on electrical tuning devices with limited bandwidth and accuracy such as electrical delay lines and electrical attenuators, or use filtering devices with strong device parameter dependencies such as optical filters and wavelength division multiplexers, or are based on incoherent optical systems, which limit the stability of the system. Therefore, a self-interference cancellation scheme that does not rely on electrical tuning devices and filtering devices, has a simple structure, and a stable system will be more conducive to the practical and engineering development of self-interference cancellation systems. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides an optical domain self-interference cancellation and anti-dispersion transmission device, including a narrow linewidth laser 1, a polarization multiplexing - dual parallel - Mach - Zehnder modulator PDM-DPMZM 2, an electrical power splitter 3, a single-mode optical fiber 4, an optical power amplifier 5, a polarization beam splitter 6, an optical delay line 7, a first photodetector 8, a second photodetector 9, and an electrical combiner 10; wherein

[0005] A narrow linewidth laser 1 outputs narrow linewidth laser as an optical carrier, and its output end is connected to the optical input end of a polarization multiplexing - dual parallel - Mach - Zehnder modulator PDM - DPMZM 2;

[0006] The polarization multiplexing - dual parallel - Mach - Zehnder modulator PDM - DPMZM 2 receives the optical carrier output by the narrow linewidth laser 1, and outputs an optical carrier radio frequency signal after electro - optical modulation;

[0007] The input end of the power splitter 3 receives the local oscillator signal from the local oscillator signal generator, splits the local oscillator signal, and outputs two paths with equal power and the same phase, which are respectively input to one radio frequency input port of the upper and lower paths of the PDM - DPMZM 2;

[0008] A single - mode fiber 4 receives the optical carrier radio frequency signal output by the PDM - DPMZM 2 and performs long - distance transmission on it;

[0009] An optical power amplifier 5 receives the optical carrier radio frequency signal transmitted by the single - mode fiber 4, amplifies the optical power of the optical carrier radio frequency signal, and outputs the amplified optical carrier radio frequency signal;

[0010] A polarization beam splitter 6 receives the amplified optical carrier radio frequency signal output by the optical power amplifier 5, performs polarization beam splitting on it, and outputs two optical carrier radio frequency signals with orthogonal polarizations;

[0011] An optical delay line 7 receives the first path of the optical carrier radio frequency signal containing the reference signal and the local oscillator signal output by the polarization beam splitter 6, performs delay adjustment on it, and outputs the delayed and adjusted signal;

[0012] A first photodetector 8 receives the second path of the optical carrier radio frequency signal containing the mixed received signal and the local oscillator signal output by the polarization beam splitter 6, performs photoelectric conversion on it, and outputs an electrical signal;

[0013] A second photodetector 9 receives the delayed and adjusted signal output by the optical delay line 7, performs photoelectric conversion on it, and outputs another electrical signal;

[0014] An electrical combiner 10 receives the electrical signals after photoelectric conversion output by the first photodetector 8 and the second photodetector 9, combines the two electrical signals, and outputs the combined electrical signal.

[0015] There is also provided an optical - domain self - interference cancellation and anti - dispersion transmission method, which is based on the above - mentioned optical - domain self - interference cancellation and anti - dispersion transmission device, and specifically includes the following steps:

[0016] Step 1: Inject the optical carrier into the PDM - DPMZM 2, where it is modulated by the received signal, the reference signal, and the local oscillator signal in the PDM - DPMZM 2 to generate an optical carrier radio frequency signal;

[0017] The optical carrier generated by the narrow linewidth laser 1 is injected into the PDM-DPMZM 2, and the optical carrier is represented as E c (t) = E c exp(jω c t), where E c and ω c respectively represent the amplitude and the central angular frequency of the optical carrier, and j represents the imaginary unit; the mixed received signal V RF (t) containing the self-interference signal and the useful signal received from the outside is expressed as V RF (t) = V SOI expjω SOI (t + τ SOI ) + V SI expjω SI (t + τ SI ), where V SOI , ω SOI , and τ SOI are the amplitude, angular frequency, and initial time delay of the useful signal in the mixed received signal, and V SI , ω SI , and τ SI are the amplitude, angular frequency, and initial time delay of the self-interference signal in the mixed received signal; the local oscillator signal V LO (t) is expressed as V LO (t) = V LO expjω LO (t + τ LO ), where V LO , ω LO , and τ LO are respectively the amplitude, angular frequency, and initial time delay of the local oscillator signal; the reference signal V REF (t) is expressed as V REF (t) = V REF expjω REF (t + τ REF ), where V REF , ω REF , and τ REF are respectively the amplitude, angular frequency, and initial time delay of the reference signal;

[0018] The local oscillator signal is first input into the power divider 3 and divided into two signals with equal power and phase, which are respectively injected into the upper and lower paths of the PDM-DPMZM 2 as a radio frequency drive signal for one of the upper and lower sub-modulators; the mixed received signal and the reference signal are directly injected into the upper and lower paths of the PDM-DPMZM 2 as the other radio frequency drive signal for the upper and lower sub-modulators respectively;

[0019] Adjust the DC bias voltage of the input PDM-DPMZM 2 so that the sub-modulators in the PDM-DPMZM 2 all operate at the minimum bias point, thereby generating double-sideband modulation signals with carrier suppression for the useful signal, self-interference signal, reference signal, and local oscillator signal; therefore, the radio-over-fiber signal output by the PDM-DPMZM 2 is expressed as

[0020]

[0021] where β SOI =πV SOI / V π , β SI =πV SI / V π , β REF =πV REF / V π , β LO =πV LO / V π are the modulation coefficients of the useful signal, self-interference signal, reference signal, and local oscillator signal respectively, V π is the half-wave voltage of the PDM-DPMZM 2, J 0 / 1 (β i ) is the 0th or 1st order Bessel function of the first kind of the corresponding signal, where i represents SOI, SI, REF, or LO, and are the unit vectors in the X polarization direction and Y polarization direction respectively, and are the adjustable phase shifts introduced by the DC bias points of the upper and lower main modulators;

[0022] Step 2: After the radio-over-fiber signal is output from the PDM-DPMZM 2, it is introduced into the single-mode fiber 4 to introduce the dispersion phase and perform long-distance transmission, and then injected into the optical power amplifier 5 to achieve power amplification;

[0023] The two polarization-orthogonal radio-over-fiber modulation signals output by the PDM-DPMZM 2 are transmitted over a long distance through the single-mode fiber 4, and at the same time, the dispersion phase is introduced. Then, the radio-over-microwave signal with the dispersion phase output by the single-mode fiber 4 is injected into the optical power amplifier 5 for power amplification, and its output signal is expressed as

[0024]

[0025] where α, L, and β 2 are the attenuation coefficient, length, and second-order dispersion coefficient of the single-mode fiber respectively, and G is the gain of the optical power amplifier 5;

[0026] Step 3: The radio-over-fiber signal after optical fiber transmission and optical power amplification is subjected to polarization beam splitting, delay matching, and optoelectronic conversion to achieve phase-intensity modulation conversion, eliminate the self-interference signal, and compensate for the dispersion-induced power fading effect;

[0027] The radio-over-fiber signal output by the optical power amplifier 5 is first input into the polarization beam splitter 6 to separate the signals in two orthogonally polarized directions. One radio-over-fiber signal modulated with the useful signal, self-interference signal, and local oscillator signal directly enters the first photodetector 8 through the polarization beam splitter 6 for optoelectronic conversion. The other radio-over-fiber signal modulated with the reference signal and local oscillator signal is output by the polarization beam splitter 6 and then enters the optical delay line 7. An adjustable delay is introduced by the optical delay line 7, and then it is output to the second photodetector 9 for optoelectronic conversion. The two electrical signals are coupled by the electrical combiner 10 and output, expressed as:

[0028]

[0029] where \(i\) represents the coupled electrical signal output by the electrical combiner 10, \(R\) is the responsivity of the first photodetector 8 and the second photodetector 9. Assuming their responsivities are the same, \(A\), \(B\), and \(C\) are the amplitude coefficients of the useful intermediate-frequency component, self-interference intermediate-frequency component, and reference intermediate-frequency component in the coupled electrical signal output by the electrical combiner 10 respectively, and \(\tau\) is the adjustable delay introduced by the optical delay line 7 on the reference branch signal;

[0030] It can be seen from Equation (3) that due to the double-sideband modulation and fiber dispersion effect, the phase modulation is converted into intensity modulation after optoelectronic detection. By adjusting the phase shift introduced by the optical delay line 7 and the DC bias points of the two main modulators, the conditions that the amplitudes of the self-interference intermediate-frequency component and the reference intermediate-frequency component are equal, the delay is matched, and the phases are opposite, as well as the compensation condition for the dispersion-induced power fading of the useful intermediate-frequency signal, can be simultaneously satisfied, that is, satisfying:

[0031]

[0032] Therefore, self-interference cancellation and compensation for the dispersion-induced power fading effect can be simultaneously achieved. At this time, the finally obtained output signal is:

[0033] i = 8RGE c 2 e -αL J 1 (β SOI )J 0 (β SI )J 1 (β LO )cos[ω SOI (t + τ SOI ) - ω LO (t + τ LO )] (5)

[0034] The device of the present invention is based on a coherent light source system, with a relatively simple and compact structure. It uses double-sideband modulation and dispersion effect to realize the conversion of phase-intensity modulation, and can achieve self-interference cancellation without relying on electrical tuning devices, electrical couplers, and optical filters. The cancellation performance is not affected by optical fiber transmission. Moreover, by adjusting the DC bias point of the main modulator, the compensation for the dispersion-induced power fading effect can be realized, and it can be applied to the radio-over-fiber system compatible with optical fiber transmission under the in-band full-duplex system, improving the system transmission rate and communication capacity. Brief Description of the Drawings

[0035] Figure 1 It is a schematic structural diagram of the optical self-interference cancellation and anti-dispersion transmission device based on the present invention. Specific Embodiment Method

[0036] The present invention will be further described below with reference to the drawings:

[0037] Figure 1 It is a schematic structural diagram of the optical domain self-interference cancellation and anti-dispersion transmission device of the present invention, including a narrow linewidth laser 1, a polarization multiplexing - dual parallel - Mach-Zehnder modulator PDM-DPMZM 2, an electrical power splitter 3, a single-mode optical fiber 4, an optical power amplifier 5, a polarization beam splitter 6, an optical delay line 7, a first photodetector 8, a second photodetector 9, and an electrical combiner 10.

[0038] The narrow linewidth laser 1 outputs narrow linewidth laser as an optical carrier, and its output end is connected to the optical input end of the polarization multiplexing - dual parallel - Mach-Zehnder modulator PDM-DPMZM 2;

[0039] The polarization multiplexing - dual parallel - Mach-Zehnder modulator PDM-DPMZM 2 receives the optical carrier output by the narrow linewidth laser 1 and outputs an optical carrier radio frequency signal after electro-optic modulation;

[0040] The input end of the electrical power splitter 3 receives the local oscillator signal from the local oscillator signal generator, splits the local oscillator signal, and outputs two paths with equal power and the same phase, which are respectively input to one radio frequency input port of the upper and lower paths of the PDM-DPMZM 2;

[0041] The single-mode optical fiber 4 receives the optical carrier radio frequency signal output by the PDM-DPMZM 2 and transmits it over a long distance;

[0042] The optical power amplifier 5 receives the optical carrier radio frequency signal transmitted by the single-mode optical fiber 4, amplifies the optical power of the optical carrier radio frequency signal, and outputs the amplified optical carrier radio frequency signal;

[0043] A polarization beam splitter 6, which receives the optically modulated radio frequency signal with amplified power output by the optical power amplifier 5, performs polarization beam splitting on it, and outputs two optically modulated radio frequency signals with orthogonal polarizations;

[0044] An optical delay line 7, which receives the first optically modulated radio frequency signal containing the reference signal and the local oscillator signal output by the polarization beam splitter 6, performs delay adjustment on it and outputs the signal after delay adjustment;

[0045] A first optoelectronic detector 8, which receives the second optically modulated radio frequency signal containing the mixed received signal and the local oscillator signal output by the polarization beam splitter 6, performs optoelectronic conversion on it, and outputs an electrical signal;

[0046] A second optoelectronic detector 9, which receives the signal after delay adjustment output by the optical delay line 7, performs optoelectronic conversion on it, and outputs another electrical signal;

[0047] An electrical beam combiner 10, which receives the electrical signals after optoelectronic conversion output by the first optoelectronic detector 8 and the second optoelectronic detector 9, combines the two electrical signals, and outputs the combined electrical signal.

[0048] Using Figure 1 the structure shown, the optical self-interference cancellation and dispersion-resistant transmission process based on intensity modulation and dispersion effect are completed as follows:

[0049] Step 1: Inject the optical carrier into the PDM-DPMZM 2, where it is modulated by the received signal, the reference signal and the local oscillator signal to generate an optically modulated radio frequency signal;

[0050] Inject the optical carrier generated by the narrow linewidth laser 1 into the PDM-DPMZM 2. The optical carrier is represented as E c (t) = E c exp(jω c t), where E c and ω c respectively represent the amplitude and the central angular frequency of the optical carrier, and j represents the imaginary unit. The mixed received signal V RF (t) received by the device of the present invention from the outside and containing the self-interference signal and the useful signal can be expressed as V RF (t) = V SOI expjω SOI (t + τ SOI ) + V SI expjω SI (t + τ SI ), where V SOI , ω SOI , τ SOI are the amplitude, angular frequency, and initial time delay of the useful signal in the mixed received signal, and V SI , ω SI, τ SI are the amplitude, angular frequency, and initial time delay of the self-interference signal in the mixed received signal. The local oscillator signal V LO (t) can be expressed as V LO (t) = V LO exp(jω LO (t + τ LO ), where V LO , ω LO , τ LO are the amplitude, angular frequency, and initial time delay of the local oscillator signal respectively. The reference signal V REF (t) can be expressed as V REF (t) = V REF exp(jω REF (t + τ REF ), where V REF , ω REF , τ REF are the amplitude, angular frequency, and initial time delay of the reference signal respectively.

[0051] The local oscillator signal is first input into the power divider 3 and divided into two signals with equal power and phase, which are respectively injected into the upper and lower paths of the PDM-DPMZM 2 as one of the RF drive signals for the upper and lower sub-modulators. The mixed received signal and the reference signal are directly injected into the upper and lower paths of the PDM-DPMZM 2 as the other RF drive signals for the upper and lower sub-modulators respectively.

[0052] Adjust the DC bias voltage input to the PDM-DPMZM 2 so that the sub-modulators in the PDM-DPMZM 2 all operate at the minimum bias point, thereby generating the carrier-suppressed double-sideband modulation signals of the useful signal, self-interference signal, reference signal, and local oscillator signal. Therefore, the optical carrier RF signal output by the PDM-DPMZM 2 can be expressed as

[0053]

[0054] where, β SOI = πV SOI / V π , β SI = πV SI / V π , β REF = πV EEF / V π , β LO = πV LO / V π are the modulation coefficients of the useful signal, self-interference signal, reference signal, and local oscillator signal respectively, V π is the half-wave voltage of the PDM-DPMZM 2, J 0 / 1 (β iis the Bessel function of the first kind of order 0 or 1 for the corresponding signal, where i represents SOI, SI, REF, or LO. and are the unit vectors in the X and Y polarization directions respectively. and are the adjustable phase shifts introduced by the DC bias points of the upper and lower main modulators.

[0055] Step 2: After the optically - carried RF signal is output from PDM - DPMZM 2, it passes through a single - mode fiber 4 to introduce a dispersion phase and is transmitted over a long distance, and then is injected into an optical power amplifier 5 to achieve power amplification.

[0056] The two polarization - orthogonal optically - carried RF modulation signals output from PDM - DPMZM 2 are transmitted over a long distance through a single - mode fiber 4, and at the same time, a dispersion phase is introduced. Then, the optically - carried microwave signal with the dispersion phase output from the single - mode fiber 4 is injected into the optical power amplifier 5 for power amplification. Its output signal can be expressed as

[0057]

[0058] where α, L, and β 2 are respectively the attenuation coefficient, length, and second - order dispersion coefficient of the single - mode fiber, and G is the gain of the optical power amplifier 5.

[0059] Step 3: The optically - carried RF signal after fiber transmission and optical power amplification undergoes polarization beam splitting, delay matching, and optoelectronic conversion to achieve phase - intensity modulation conversion, eliminate self - interference signals, and compensate for the dispersion - induced power fading effect.

[0060] The optically - carried RF signal output from the optical power amplifier 5 is first input into a polarization beam splitter 6 to separate the signals in two polarization - orthogonal directions. One optically - carried RF signal that modulates the useful signal, self - interference signal, and local oscillator signal directly enters the first photodetector 8 through the polarization beam splitter 6 for optoelectronic conversion. The other optically - carried RF signal that modulates the reference signal and local oscillator signal is output from the polarization beam splitter 6 and then enters an optical delay line 7. An adjustable delay is introduced by the optical delay line 7, and then it is output to the second photodetector 9 for optoelectronic conversion. The two electrical signals are coupled through an electrical combiner 10 and output, which can be expressed as:

[0061]

[0062] where i represents the coupled electrical signal output from the electrical combiner 10, R is the responsivity of the first photodetector 8 and the second photodetector 9. Assuming their responsivities are the same, A, B, and C are respectively the amplitude coefficients of the useful intermediate - frequency component, self - interference intermediate - frequency component, and reference intermediate - frequency component in the coupled electrical signal output from the electrical combiner 10, and τ is the adjustable delay introduced by the optical delay line 7 on the reference - branch signal.

[0063] As can be seen from Equation (3), due to double-sideband modulation and fiber dispersion effects, the phase modulation is converted into intensity modulation after photoelectric detection. By adjusting the phase shifts introduced by the optical delay line 7 and the DC bias points of the two main modulators, the conditions that the amplitudes of the self-interference intermediate-frequency component and the reference intermediate-frequency component are equal, the delay is matched, and the phases are opposite, as well as the compensation condition for the dispersion-induced power fading of the useful intermediate-frequency signal can be simultaneously satisfied, that is:

[0064]

[0065] Therefore, self-interference cancellation and compensation for the dispersion-induced power fading effect can be simultaneously achieved. At this time, the finally obtained output signal is:

[0066] i = 8RGE c 2 e -αL J 1 (β SOI )J 0 (β SI )J 1 (β LO )cos[ω SOI (t + τ SOI ) - ω LO (t + τ LO )] (5)

[0067] Therefore, compared with the traditional double-sideband modulation link, the present invention can achieve down-conversion of the input microwave signal, and can simultaneously achieve self-interference cancellation and compensation for the dispersion-induced power fading effect.

[0068] The present invention proposes an optical-domain self-interference cancellation and anti-dispersion transmission device and method. The device is based on a coherent light source system and has a relatively simple and compact structure. It uses double-sideband modulation and dispersion effects to realize phase-intensity modulation conversion. Self-interference cancellation can be achieved without relying on electrical tuning devices, electrical couplers, and optical filters, and the cancellation performance is not affected by fiber transmission; moreover, by adjusting the DC bias point of the main modulator, compensation for the dispersion-induced power fading effect can be achieved, and it can be applied to an optical wireless system compatible with fiber transmission under an in-band full-duplex system, improving the system transmission rate and communication capacity.

Claims

1. An optical-domain self-interference cancellation and anti-dispersion transmission device, characterized in that, it includes a narrow-linewidth laser (1), a polarization multiplexing - dual parallel - Mach - Zehnder modulator PDM-DPMZM (2), an electrical power splitter (3), a single-mode optical fiber (4), an optical power amplifier (5), a polarization beam splitter (6), an optical delay line (7), a first photodetector (8), a second photodetector (9), and an electrical combiner (10); The narrow-linewidth laser (1) outputs narrow-linewidth laser as an optical carrier, and its output end is connected to the optical input end of the polarization multiplexing - dual parallel - Mach - Zehnder modulator PDM-DPMZM (2); The polarization multiplexing - dual parallel - Mach - Zehnder modulator PDM-DPMZM (2) receives the optical carrier output by the narrow-linewidth laser (1), and outputs an optical carrier radio frequency signal after electro-optical modulation; by adjusting the DC bias voltage input to the PDM-DPMZM (2), the sub-modulators in the PDM-DPMZM (2) all work at the minimum bias point, thereby generating carrier-suppressed double-sideband modulation signals of useful signals, self-interference signals, reference signals, and local oscillator signals; The input end of the electrical power splitter (3) receives the local oscillator signal from the local oscillator signal generator, splits the local oscillator signal, and outputs two paths with equal power and the same phase, which are respectively input to one radio frequency input port of the upper and lower paths of the PDM-DPMZM (2); The single-mode optical fiber (4) receives the optical carrier radio frequency signal output by the PDM-DPMZM (2) and performs long-distance transmission on it; The optical power amplifier (5) receives the optical carrier radio frequency signal transmitted by the single-mode optical fiber (4), amplifies the optical power of the optical carrier radio frequency signal, and outputs the optical carrier radio frequency signal with amplified power; The polarization beam splitter (6) receives the optical carrier radio frequency signal with amplified power output by the optical power amplifier (5), performs polarization beam splitting on it, and outputs two paths of optical carrier radio frequency signals with orthogonal polarizations; The optical delay line (7) receives the first path of optical carrier radio frequency signal containing the reference signal and the local oscillator signal output by the polarization beam splitter (6), performs delay adjustment on it, and outputs the signal after delay adjustment; The first photodetector (8) receives the second path of optical carrier radio frequency signal containing the mixed received signal and the local oscillator signal output by the polarization beam splitter (6), performs photoelectric conversion on it, and outputs an electrical signal; The second photodetector (9) receives the signal after delay adjustment output by the optical delay line (7), performs photoelectric conversion on it, and outputs another electrical signal; The electrical combiner (10) receives the electrical signals after photoelectric conversion output by the first photodetector (8) and the second photodetector (9), combines the two electrical signals, and outputs the combined electrical signal.

2. An optical-domain self-interference cancellation and anti-dispersion transmission method, which is based on the optical-domain self-interference cancellation and anti-dispersion transmission device as described in claim 1, characterized in that, it specifically includes the following steps: Step 1: Inject the optical carrier into the PDM-DPMZM (2), and it is modulated by the received signal, reference signal, and local oscillator signal in the PDM-DPMZM (2) to generate an optical carrier radio frequency signal; Inject the optical carrier generated by the narrow linewidth laser (1) into the PDM-DPMZM (2). The optical carrier is expressed as E c (t) = E c exp(jω c t), where E c and ω c represent the amplitude and central angular frequency of the optical carrier respectively, and j represents the imaginary unit; The mixed received signal V RF (t) containing the self-interference signal and the useful signal received from the outside is expressed as V RF (t) = V SOI expjω SOI (t + τ SOI ) + V SI expjω SI (t + τ SI ), where V SOI , ω SOI , and τ SOI are the amplitude, angular frequency, and initial time delay of the useful signal in the mixed received signal, and V SI , ω SI , and τ SI are the amplitude, angular frequency, and initial time delay of the self-interference signal in the mixed received signal; The local oscillator signal V LO (t) is expressed as V LO (t) = V LO expjω LO (t + τ LO ), where V LO , ω LO , and τ LO are the amplitude, angular frequency, and initial time delay of the local oscillator signal respectively; The reference signal V REF (t) is expressed as V REF (t) = V REF expjω REF (t + τ REF ), where V REF , ω REF , and τ REF are the amplitude, angular frequency, and initial time delay of the reference signal respectively; The local oscillator signal is first input into the power divider (3) and divided into two signals with equal power and phase, which are respectively injected into the upper and lower paths of the PDM-DPMZM (2) as a radio frequency drive signal for one of the upper and lower sub-modulators; the mixed received signal and the reference signal are directly injected into the upper and lower paths of the PDM-DPMZM (2) as the other radio frequency drive signal for the upper and lower sub-modulators; Therefore, the radio over fiber signal output by the PDM-DPMZM (2) is expressed as Among them, β SOI = πV SOI / V π 、β SI = πV SI / V π 、β REF = πV REF / V π 、β LO = πV LO / V π are the modulation coefficients of the useful signal, self-interference signal, reference signal, and local oscillator signal respectively. V π is the half-wave voltage of PDM-DPMZM(2). J 0 / 1 (β 1 ) is the Bessel function of the first kind of order 0 or 1 of the corresponding signal, where i represents SOI, SI, REF, or LO. and are the unit vectors in the X polarization direction and Y polarization direction respectively. and are the adjustable phase shifts introduced by the DC bias points of the upper and lower main modulators. Step 2: After the radio over fiber signal is output from the PDM-DPMZM (2), it is introduced into the dispersion phase through the single-mode fiber (4) and transmitted over a long distance, and then injected into the optical power amplifier (5) to achieve power amplification; The two polarization-orthogonal radio over fiber modulation signals output by the PDM-DPMZM (2) are transmitted over a long distance through the single-mode fiber (4), and the dispersion phase is introduced at the same time. Then, the radio over microwave signal with the dispersion phase output by the single-mode fiber (4) is injected into the optical power amplifier (5) for power amplification, and its output signal is expressed as Among them, α, L, and β 2 are respectively the attenuation coefficient, length, and second-order dispersion coefficient of the single-mode optical fiber, and G is the gain of the optical power amplifier (5); Step 3: The radio over fiber signal after fiber transmission and optical power amplification is subjected to polarization beam splitting, delay matching and optoelectronic conversion to achieve phase-intensity modulation conversion, eliminate the self-interference signal, and compensate for the dispersion-induced power fading effect; The radio over fiber signal output by the optical power amplifier (5) is first input into the polarization beam splitter (6) to separate the signals in two polarization-orthogonal directions. One radio over fiber signal modulating the useful signal, the self-interference signal and the local oscillator signal directly enters the first photodetector (8) through the polarization beam splitter (6) for optoelectronic conversion. The other radio over fiber signal modulating the reference signal and the local oscillator signal is output by the polarization beam splitter (6) and then enters the optical delay line (7). An adjustable delay is introduced by the optical delay line (7), and then it is output to the second photodetector (9) for optoelectronic conversion. The two electrical signals are coupled by the electrical combiner (10) and output, which is expressed as: Where, i represents the coupled electrical signal output by the electrical combiner (10), R is the responsivity of the first photodetector (8) and the second photodetector (9). Assuming that their responsivities are the same, A, B, and C are the amplitude coefficients of the useful intermediate frequency component, the self-interference intermediate frequency component, and the reference intermediate frequency component in the coupled electrical signal output by the electrical combiner (10) respectively, and τ is the adjustable delay introduced by the optical delay line (7) on the reference branch signal; It can be seen from Equation (3) that due to the double-sideband modulation and the fiber dispersion effect, the phase modulation is converted into intensity modulation after photodetection. By adjusting the phase shift introduced by the optical delay line (7) and the DC bias points of the two main modulators, the conditions that the amplitudes of the self-interference intermediate frequency component and the reference intermediate frequency component are equal, the delay is matched, and the phases are opposite, as well as the compensation condition for the dispersion-induced power fading of the useful intermediate frequency signal can be simultaneously satisfied, that is, it satisfies: Therefore, self-interference cancellation and compensation for the dispersion-induced power fading effect can be simultaneously achieved. At this time, the finally obtained output signal is: i = 8RGE c 2 e -αL J 1 (β SOI )J 0 (β SI )J 1 (β LO )cos[ω SOI (t + τ SOI ) - ω LO (t + τ LO )] (5).

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