Reverse modulation full duplex communication device and method based on phase and amplitude modulation

Abstract

The invention discloses a reverse modulation full-duplex communication device and method based on phase and amplitude modulation, and belongs to the technical field of wireless optical communication. The device comprises an inquiry end, a laser branching module, a phase modulation module, a phase modulation module and a phase modulation module, and the signal input end of the amplitude modulation module is connected with the signal output end of the laser branching module; the signal input end of the first propagation module is connected with the signal output end of the amplitude modulation module; the signal input end of the phase demodulation module is connected with the signal output ends of the laser branching module and the first propagation module; in the reverse modulation end, the second propagation module is in optical communication connection with the signal light beam splitting module, the signal light beam splitting module is in optical communication connection with the phase modulation module, and the signal input end of the amplitude demodulation module is connected with the signal output end of the signal light beam splitting module; the first propagation module and the second propagation module are in optical communication connection, full-duplex communication is completed by performing phase modulation and amplitude modulation on the same beam of optical signals, and better reverse modulation full-duplex communication is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless optical communication, and particularly relates to a reverse modulation full-duplex communication device and method based on phase and amplitude modulation. Background Technique

[0002] Free space optical communication is a wireless optical communication technology using laser as the carrier, which has the advantages of low cost, large capacity, good confidentiality, fast network construction, and no need to occupy spectrum resources. A free space optical communication system generally requires two terminals, namely an optical transmitter and an optical receiver, to be aligned, and is equipped with a PAT (Pointing, Acquisition and Tracking) system to achieve point-to-point communication. However, such a system has high cost, large volume, and heavy weight.

[0003] In a reverse modulation wireless optical communication system, the transmitter and the receiver are placed at the interrogation end, and the other end is a reverse modulation end composed of a reflector and a modulator. The working principle is as follows: the interrogation end emits an unmodulated light beam to the reverse modulation end, the reverse modulation end modulates the light beam and returns it along the original direction, and then the interrogation end demodulates the returned light beam to achieve unidirectional free space optical communication. This system does not require an automatic tracking system, which can greatly reduce the volume and weight of one end. It can be widely applied to small platforms such as small satellites, UAV reconnaissance, and ocean exploration.

[0004] As a special form of reverse modulation wireless optical communication, reverse modulation full-duplex communication can solve the problem that reverse modulation can only achieve one-way communication. The earliest research on reverse modulation full-duplex communication was a single-wavelength single-beam reverse modulation full-duplex communication achieved by a scholar in Mexico in 2004 using circular polarization keying (CPK) coding. In 2004, Shay Thomas M. et al. studied the modulating retro-reflector based free space optical (MRR FSO) system of reverse modulation. In 2015, Zhang Peng et al. proposed a full-duplex reverse modulation free space optical communication structure using dual-wavelength laser emission, and based on this structure, the intensity modulation and demodulation mode was simulated and analyzed for the full-duplex communication link between a ground station and a near-Earth small satellite at a communication distance of 300 km and a communication rate of 1 GHz. In the same year, Qiu Hao et al. proposed a single-source full-duplex MRR FSO scheme, where the on-off keying (OOK) modulation was used for the uplink and amplitude modulation was used for the downlink. In 2017, Chen Jing et al. proposed a reverse modulation system based on a lithium niobate phase modulator and a piezoelectric ceramic, using phase shift keying (PSK) / on-off keying (OOK), which can operate in a full-duplex mode, and its feasibility was verified through simulation experiments. In 2018, Zhang Huan proposed a full-duplex communication channel model based on indoor visible light, and through experiments, a full-duplex communication with a downlink rate of 5 Mbit / s and an uplink rate of 2 Kbit / s was stably achieved at a distance of 3 m. In 2018, Ke Xizheng et al. and in 2019, Yang Yufeng et al. both studied the full-duplex communication system based on a single source of indoor visible light, realizing the function of visible light for both lighting and communication, and the experiments proved that the communication of the uplink and downlink of the communication system does not interfere with each other and the communication effect is good. In 2019, Yin Xiaoli et al. proposed a full-duplex free space optical communication system based on reverse modulation of orbital angular momentum (OAM), which can perform high-order modulation and improve the frequency band utilization rate of the system.

[0005] There is less research on the full-duplex MRR FSO communication link abroad. In domestic research, it mainly focuses on experimental research on indoor visible light, with certain experimental limitations. In the experiment of realizing MRR full-duplex through dual wavelengths, there is a problem that the focal points of the same lens for different wavelengths are inconsistent, and the requirements for devices are relatively high. Achieving full-duplex based on OAM can reach high-order modulation of any OAM mode, but OAM beams are sensitive and easily damaged, and wavefront distortion is likely to occur. Based on the current research status of MRRFSO at home and abroad, it is still necessary to further study and solve the problem of the simplex communication limitation of the reverse modulation free space optical communication system. Summary of the Invention

[0006] The present invention aims to overcome the deficiencies in the prior art and provides a reverse modulation full-duplex communication device and method based on phase and amplitude modulation. Amplitude modulation and phase modulation are respectively performed at the interrogation end and the reverse modulation end to achieve reverse modulation full-duplex communication, further solving the problem of simplex communication limitation in the reverse modulation space optical communication system.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions:

[0008] In a first aspect, the present invention provides a reverse modulation full-duplex communication device based on phase and amplitude modulation, including an interrogation end and a reverse modulation end;

[0009] The interrogation end includes: a laser splitting module, an amplitude modulation module, a phase demodulation module, and a first propagation module;

[0010] The signal input ends of the amplitude modulation module and the phase demodulation module are respectively connected to the signal output end of the laser splitting module. The signal input end of the first propagation module is connected to the signal output end of the amplitude modulation module, and the signal input end of the phase demodulation module is also connected to the signal output end of the first propagation module;

[0011] The reverse modulation end includes: a second propagation module, a signal light splitting module, a phase modulation module, and an amplitude demodulation module;

[0012] The second propagation module is optically communicatively connected to the signal light splitting module. The signal light splitting module is optically communicatively connected to the phase modulation module. The signal input end of the amplitude demodulation module is connected to the signal output end of the signal light splitting module;

[0013] The first propagation module is optically communicatively connected to the second propagation module.

[0014] Optionally, the first propagation module includes an optical fiber circulator and an optical antenna 1;

[0015] The second propagation module includes an optical antenna 2;

[0016] The signal transmission end of the optical antenna 1 is connected to the signal transmission end of the optical fiber circulator;

[0017] The optical fiber circulator is used to send the signal light of the amplitude modulation module to the optical antenna 1 and send the signal light from the optical antenna 2 to the phase demodulation module;

[0018] The emission angles of the optical antenna 1 and the optical antenna 2 correspond to each other.

[0019] Optionally, the laser splitting module includes a laser and an optical fiber splitter;

[0020] The signal input end of the optical fiber splitter is connected to the signal output end of the laser, and the signal output ends are respectively connected to the amplitude modulation module and the phase demodulation module;

[0021] The signal light beam splitting module includes a beam splitter, and the beam splitter is placed on the side of optical antenna two away from optical antenna one.

[0022] Optionally, the amplitude modulation module includes: an acousto-optic modulator, a first driver, and an optical fiber amplifier;

[0023] The signal input end of the acousto-optic modulator is respectively connected to the optical fiber splitter and the signal output end of the first driver, and the signal output end is connected to the signal input end of the optical fiber amplifier;

[0024] A first modulation signal is input to the signal input end of the first driver;

[0025] The amplitude demodulation module includes: a first erbium-doped optical fiber amplifier and a first optical detector;

[0026] The first erbium-doped optical fiber amplifier is arranged in the direction of one path of signal light of the beam splitter;

[0027] The signal input end of the first erbium-doped optical fiber amplifier is connected to the signal output end of the beam splitter, and the signal output end is connected to the signal input end of the first optical detector;

[0028] The signal output end of the first optical detector outputs a first modulation signal.

[0029] Optionally, the phase modulation module includes: a focusing lens, a piezoelectric ceramic, and a second driver;

[0030] The focusing lens and the optical antenna two are respectively arranged on both sides of the beam splitter, and the piezoelectric ceramic is arranged at the focal point of the focusing lens on the side away from the beam splitter;

[0031] The signal input end of the focusing lens is respectively connected to the beam splitter and the signal output end of the piezoelectric ceramic;

[0032] The signal input end of the piezoelectric ceramic is respectively connected to the focusing lens and the signal output end of the second driver, and the signal output end is connected to the signal input end of the focusing lens;

[0033] A second modulation signal is input to the signal input end of the second driver;

[0034] The phase demodulation module includes: a second erbium-doped optical fiber amplifier, a polarization controller, an optical coupler, a second optical detector, and a signal processing unit;

[0035] The signal input end of the second erbium-doped optical fiber amplifier is connected to the signal output end of the optical fiber circulator, and the signal output end is connected to the signal input end of the optical coupler;

[0036] The signal output end of the polarization controller is connected to the signal input end of the optical coupler, and the signal input end is connected to the signal output end of the optical fiber splitter;

[0037] The signal input end of the second optical detector is connected to the signal output end of the optical coupler, and the signal output end is connected to the signal input end of the signal processing unit;

[0038] The signal output end of the signal processing unit outputs a second modulation signal.

[0039] In a second aspect, the present invention provides a reverse modulation full-duplex communication method based on phase and amplitude modulation, which applies the reverse modulation full-duplex communication device described in any step of the first aspect, and includes:

[0040] In the simplex communication from the interrogation end to the reverse modulation end:

[0041] At the interrogation end,

[0042] The first beam of light and the second beam of light are obtained through the laser beam splitting module;

[0043] The first beam of light is amplitude-modulated according to the first modulation signal through the amplitude modulation module, and the amplitude-modulated signal light is transmitted to the second propagation module at the reverse modulation end through the first propagation module;

[0044] At the reverse modulation end,

[0045] The amplitude-modulated signal light is split through the signal light splitting module to obtain the first beam of signal light and the second beam of signal light;

[0046] The first beam of signal light is photoelectrically detected through the amplitude demodulation module to obtain the restored first modulation signal;

[0047] In the simplex communication from the reverse modulation end to the interrogation end:

[0048] At the reverse modulation end,

[0049] The second beam of signal light is phase-modulated according to the second modulation signal through the phase modulation module, and the phase-amplitude-modulated signal light is reflected back to the first propagation module at the interrogation end through the second propagation module;

[0050] At the interrogation end,

[0051] The phase-amplitude-modulated signal light is phase-demodulated according to the second beam of light through the phase demodulation module to obtain the restored second modulation signal.

[0052] Optionally, the step of amplitude-modulating the first beam of light according to the first modulation signal through the amplitude modulation module includes:

[0053] The first acousto-optic modulator is driven by the first driver according to the magnitude of the first modulation signal to perform amplitude modulation on the first beam of light, and the photoelectric field intensity after amplitude modulation The expression is as follows:

[0054] ,

[0055] where is the phase constant of the light after amplitude modulation, is the frequency of the light after amplitude modulation, is the amplitude constant of the light after amplitude modulation, is the first modulation signal.

[0056] Optionally, the first beam of signal light is subjected to photoelectric detection by the amplitude demodulation module to obtain the restored first modulation signal, including:

[0057] The first erbium-doped fiber amplifier amplifies the first beam of signal light and emits it into the first photodetector;

[0058] The first photodetector performs photoelectric detection on the first beam of signal light, and the expression of the output photocurrent is as follows:

[0059] ,

[0060] where is the photocurrent output by the first photodetector, is the responsivity of the photodetector, with the unit of A / W, is a constant;

[0061] The output of the first modulation signal is obtained according to the output photocurrent.

[0062] Optionally, the second beam of signal light is phase-modulated by the phase modulation module according to the second modulation signal, including:

[0063] The second driver drives the piezoelectric ceramic to vibrate according to the magnitude of the second modulation signal to perform phase modulation on the second beam of signal light, and the photoelectric field intensity after phase-amplitude modulation The expression is as follows:

[0064] ,

[0065] where is the second modulation signal.

[0066] Optionally, the phase demodulation module performs phase demodulation on the signal light after phase-amplitude modulation according to the second beam of light to obtain the restored second modulation signal, including:

[0067] The amplified signal light after phase - amplitude modulation is amplified by the second erbium - doped fiber amplifier and emitted into an optical coupler;

[0068] The polarization state of the incident second - path light beam is adjusted by the polarization controller to be the same as that of the signal light after phase - amplitude modulation, and the adjusted laser light beam is emitted into the optical coupler. Among them, the optical - electric field intensity of the second - path light beam after polarization - state adjustment has the following expression;

[0069] ,

[0070] where, is the phase constant of the second - path light beam after polarization - state adjustment, is the frequency of the second - path light beam after polarization - state adjustment, is the amplitude constant of the second - path light beam after polarization - state adjustment;

[0071] The amplified signal light after phase - amplitude modulation and the second - path light beam after polarization - state adjustment are coupled by the optical coupler, and the coupled signal light is emitted into a second optical detector. The power of the coupled signal light has the following expression:

[0072] ,

[0073] where, is a constant, is the power of the signal light after phase - amplitude modulation, is the power of the second - path light beam after polarization - state adjustment;

[0074] The coupled signal light is coherently detected by the second optical detector to output a photocurrent, and the photocurrent is sent to a signal processing unit. Among them, the expression of the output photocurrent is:

[0075] ,

[0076] where, is the photocurrent output by the second optical detector, is the responsivity of the optical detector, with the unit of A / W;

[0077] The signal processing unit obtains the output of the second modulation signal according to the photocurrent, and the calculation formula is as follows:

[0078] .

[0079] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: By setting an amplitude modulation module and a phase demodulation module at the interrogation end, and a phase modulation module and an amplitude demodulation module at the reverse modulation end, full-duplex communication is completed at the interrogation end and the reverse modulation end using the same beam of signal light. There is no need for high requirements on lens devices, nor is it necessary to pay attention to the problem that the OAM beam is sensitive and easily damaged, realizing reverse modulation full-duplex communication with fewer restrictions and better effects; The beam emitted by the laser is amplitude-modulated for the optical signal through an acousto-optic modulator at the interrogation end. After reaching the reverse modulation end through the atmospheric channel, the phase of the optical signal is modulated by controlling the vibration of the piezoelectric ceramic. At the same time, the amplitude change of the demodulation signal is directly detected. Then, after the echo-reflected optical signal reaches the interrogation end, the phase information of the signal is demodulated through coherent detection and the signal processing unit. Reverse modulation full-duplex communication is completed through the propagation of a beam of signal light between various devices, solving the problem of simplex communication limitation in the reverse modulation free-space optical communication system. Description of the Drawings

[0080] Figure 1 The figure shows a schematic structural diagram of a reverse modulation full-duplex communication device based on phase and amplitude modulation in an embodiment of the present invention;

[0081] Figure 2 The figure shows a flowchart of a reverse modulation full-duplex communication method based on phase and amplitude modulation in an embodiment of the present invention.

[0082] Figure 1 In the figure: 1. Laser; 2. Optical fiber splitter; 3. Acousto-optic modulator; 4. First driver; 5. Optical fiber amplifier; 6. Optical fiber circulator; 7. Beam splitter; 8. Focusing lens; 9. Piezoelectric ceramic; 10. Second driver; 11. First erbium-doped optical fiber amplifier; 12. First optical detector; 13. Second erbium-doped optical fiber amplifier; 14. Polarization controller; 15. Optical coupler; 16. Second optical detector; 17. Signal processing unit. Detailed Embodiments

[0083] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0084] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0085] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present invention can be understood according to specific circumstances.

[0086] Embodiment 1

[0087] This embodiment provides a reverse modulation full-duplex communication device based on phase and amplitude modulation, including an interrogation end and a reverse modulation end;

[0088] The interrogation end includes: a laser splitting module for generating multiple paths of lasers to be communicated, an amplitude modulation module for amplitude modulating one of the split lasers, a phase demodulation module for phase demodulating the phase-amplitude modulated signal light reflected from the reverse modulation end according to the other split laser, and a first propagation module for transmitting the amplitude modulated signal light to the reverse modulation end and receiving the phase-amplitude modulated signal light reflected back from the reverse modulation end;

[0089] The signal input ends of the amplitude modulation module and the phase demodulation module are respectively fiber-connected to the signal output end of the laser splitting module. The signal input end of the first propagation module is fiber-connected to the signal output end of the amplitude modulation module, and the signal input end of the phase demodulation module is also fiber-connected to the signal output end of the first propagation module;

[0090] The reverse modulation end includes: a second propagation module for receiving the amplitude-modulated signal light emitted by the interrogation end and reflecting the phase-amplitude-modulated signal light to the interrogation end, a signal light splitting module for splitting the amplitude-modulated signal light, a phase modulation module for performing phase modulation on the amplitude-modulated signal light, and an amplitude demodulation module for performing amplitude demodulation on the amplitude-modulated signal light;

[0091] The signal transmission end of the second propagation module and the signal light splitting module are connected by two-way optical communication through an atmospheric channel. The signal transmission end of the signal light splitting module and the phase modulation module are connected by two-way optical communication through an atmospheric channel. The signal input end of the amplitude demodulation module and the signal output end of the signal light splitting module are connected by one-way optical communication through an atmospheric channel;

[0092] The signal transmission ends of the first propagation module and the second propagation module are connected by two-way optical communication through an atmospheric channel.

[0093] Full-duplex communication is completed by performing phase modulation and amplitude modulation on the same optical signal at the interrogation end and the reverse modulation end respectively, achieving better reverse modulation full-duplex communication.

[0094] Embodiment 2

[0095] On the basis of Embodiment 1, the following design is also made in this embodiment.

[0096] The interrogation end is used to split the laser beam to be communicated, generate amplitude-modulated signal light according to one of the laser beams and send it to the reverse modulation end, and is used to perform phase demodulation on the amplitude-phase-modulated signal light reflected back by the reverse modulation end according to the other laser beam. As Figure 1 shown, in the interrogation end, the laser beam splitting module includes a laser 1 and an optical fiber splitter 2; the amplitude modulation module includes an acousto-optic modulator 3, a first driver 4, and an optical fiber amplifier 5; the first propagation module includes an optical fiber circulator 6 and an optical antenna 1; the phase demodulation module includes a second erbium-doped optical fiber amplifier 13, a polarization controller 14, an optical coupler 15, a second optical detector 16, and a signal processing unit 17.

[0097] The reverse modulation end is used to split the amplitude-modulated signal light emitted by the interrogation end, perform amplitude demodulation according to one of the amplitude-modulated signal lights, and is used to generate phase-amplitude-modulated signal light according to the other amplitude-modulated signal light and reflect it back to the interrogation end. As Figure 1As shown, in the reverse modulation terminal, the second propagation module includes optical antenna two, and the signal light beam splitting module includes beam splitter 7; the amplitude demodulation module includes the first erbium-doped fiber amplifier 11 and the first optical detector 12; the phase modulation module includes focusing lens 8, piezoelectric ceramic 9, and the second driver 10.

[0098] The optical fiber splitter 2 is used to split the laser beam to be communicated generated by the laser 1, and respectively emit the split lasers to the acousto-optic modulator 3 and the polarization controller 14. The acousto-optic modulator 3 is used to perform amplitude modulation on the incident laser beam. The first driver 4 is used to drive the acousto-optic modulator 3 to perform amplitude modulation on the incident light according to the magnitude of the first modulation signal. The optical fiber amplifier 5 is used to amplify the amplitude-modulated signal light and emit it to optical antenna one through the optical fiber circulator 6. Optical antenna one and optical antenna two propagate optical signals through the atmospheric channel. Among them, the incident laser beam of the acousto-optic modulator 3 comes from the optical fiber splitter 2.

[0099] Taking the direction of the amplitude-modulated signal light incident on optical antenna two as the front, the beam splitter 7 is placed obliquely behind optical antenna two, and is used to split the amplitude-modulated signal light emitted by optical antenna two. One beam enters the first erbium-doped fiber amplifier 11, and the other beam enters the focusing lens 8. Both the first erbium-doped fiber amplifier 11 and the first optical detector 12 are arranged in the transmission direction of one path of signal light of the beam splitter 7. The first erbium-doped fiber amplifier 11 is used to amplify the incident amplitude-modulated signal light and emit it into the first optical detector 12. The first optical detector 12 is used to perform photoelectric detection on the amplitude-modulated signal light to obtain the amplitude information of the signal light. Among them, the incident signal light of the first erbium-doped fiber amplifier 11 comes from the beam splitter 7.

[0100] The focusing lens 8 and optical antenna two are respectively arranged on both sides of the beam splitter 7, and the piezoelectric ceramic 9 is arranged at the focal point behind the focusing lens 8. The focusing lens 8 is used to converge the incident amplitude-modulated signal light onto the piezoelectric ceramic 9 and emit the phase-amplitude-modulated signal light. The piezoelectric ceramic 9 is used to generate a phase shift to perform phase modulation on the signal light. The second driver 10 is used to drive the piezoelectric ceramic 9 to vibrate according to the magnitude of the first modulation signal. Among them, the incident signal light of the focusing lens 8 comes from the beam splitter 7, and the emitted signal light comes from the piezoelectric ceramic 9.

[0101] The second erbium-doped fiber amplifier 13 is used to amplify the incident phase-amplitude modulated optical signal and emit it into the optical coupler 15; the polarization controller 14 is used to adjust the polarization state of the incident laser beam so that its polarization state is consistent with that of the phase-amplitude modulated optical signal, and emit the adjusted laser beam into the optical coupler 15; the optical coupler 15 is used to couple the amplified phase-amplitude modulated optical signal and the laser beam with adjusted polarization state, and emit the coupled optical signal into the second optical detector 16, and the second optical detector 16 is used to perform coherent detection on the coupled optical signal and send the coherent detection result to the signal processing unit 17, and the signal processing unit 17 is used to output phase information. Among them, the incident optical signal of the second erbium-doped fiber amplifier 13 comes from the first optical antenna, and the incident laser beam of the polarization controller 14 comes from the fiber splitter 2.

[0102] Embodiment 3

[0103] As Figure 2 shown, this embodiment provides a reverse modulation full-duplex communication method based on phase and amplitude modulation, and the specific steps are as follows:

[0104] At the interrogation end, the laser generated by the laser 1 is split into two by the fiber splitter 2. One path enters the acousto-optic modulator 3 for amplitude modulation at the interrogation end according to the first modulation signal, and then is sent after passing through the fiber circulator 6 and the first optical antenna, and is transmitted in the atmospheric channel. The other path is transmitted to the polarization controller 14. The optical field strength of the unmodulated light at the interrogation end is:

[0105] ,

[0106] In the formula, is the phase constant, is the frequency of light, is the amplitude constant.

[0107] The first driver 4 drives the acousto-optic modulator 3 to modulate the amplitude of the incident optical signal according to the magnitude of the first modulation signal , so the optical field strength after amplitude modulation is:

[0108] .

[0109] The optical signal amplitude-modulated at the interrogation end is amplified by the fiber amplifier 5, output by the fiber circulator 6 and reaches the first optical antenna, and is transmitted in the atmospheric channel.

[0110] The light beam transmitted from the interrogation end is received by the optical antenna 2 at the reverse modulation end, and is split into two at the beam splitter 7. One path reaches the focusing lens 8; the other path of light enters the first erbium-doped fiber amplifier 11 for optical signal amplification; the amplified optical signal enters the first photodetector 12 for direct detection. The first photodetector 12 for direct detection responds to the change in the optical signal power, and can only respond to the change in the optical signal power. The first photocurrent generated by it corresponds to the demodulated

[0111] signal:

[0112] wherein, is the responsivity of the photodetector, with the unit of A / W, is a constant; for light waves, the photodetector outputs an amplitude value. Since this frequency cannot be clearly observed in the first photodetector 12, the optical high-frequency term is omitted. Therefore, the above formula can be written as:

[0113]

[0114] Thus, the output of the signal can be obtained.

[0115] The piezoelectric ceramic 9 is arranged at the focal point of the focusing lens 8. The light signal after the first modulation passes through the atmospheric channel and is converged by the focusing lens 8 onto the piezoelectric ceramic 9. Driven by the second driver 10, the piezoelectric ceramic 9 vibrates back and forth with the magnitude of the externally applied signal to generate a phase shift, thereby modulating the phase of the light signal.

[0116] The amplitude-phase modulated optical electric field intensity obtained after the second modulation by the piezoelectric ceramic 9 is:

[0117]

[0118] Thus, the signal is loaded onto the phase of the light, and the laser is phase-modulated at the reverse modulation end.

[0119] Due to the "cat's eye" effect, the light beam transmitted from the interrogation end is reflected by the reverse modulation end and returns to the interrogation end in the original direction. After passing through the optical antenna 1 and the fiber optic circulator 6 at the interrogation end, it enters the second erbium-doped fiber amplifier 13 from the fiber input end face to amplify the optical signal, and then outputs and enters the optical coupler 15. At the same time, the local oscillator light passing through the fiber splitter 2 and the polarization controller 14 also enters the optical coupler 15. The polarization controller 14 adjusts the polarization state of the local oscillator light.

[0120] The optical electric field intensity of the local oscillator It can be written as:

[0121] ,

[0122] wherein, is the phase constant of the local oscillator light, is the frequency of the local oscillator light, is the amplitude constant of the local oscillator light.

[0123] After passing through the polarization controller 14, assuming that the polarization directions of the signal light and the local oscillator light are the same, according to the theory of coherent detection, the intensity of the optical signal projected onto the second optical detector 16 through the optical coupler 15 is , and the detected optical power is , is a constant, is the power of the amplitude-phase modulated light, is the power of the local oscillator light.

[0124] ,

[0125] Usually , then the photocurrent generated by the second optical detector 16 for coherent detection is:

[0126] ,

[0127] Omitting the DC term:

[0128] ,

[0129] After being processed by the signal processing unit 17, we get:

[0130] ,

[0131] wherein, , , , are all constants, eliminating them, and then performing an inverse cosine operation, so that the signal can be output.

[0132] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media including but not limited to disk memories, CD-ROMs, optical memories, etc. that contain computer-usable program code.

[0133] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatus systems, and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0134] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0135] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0136] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the present invention and the claims. All of these are within the protection scope of the present invention.

Claims

1. A reverse modulation full-duplex communication device based on phase and amplitude modulation, characterized in that: It includes an inquiry end and a reverse modulation end; The inquiry end includes: a laser splitting module, an amplitude modulation module, a phase demodulation module and a first propagation module; The signal input ends of the amplitude modulation module and the phase demodulation module are respectively connected to the signal output end of the laser splitter module, the signal input end of the first propagation module is connected to the signal output end of the amplitude modulation module, and the signal input end of the phase demodulation module is also connected to the signal output end of the first propagation module; The reverse modulation end includes: a second propagation module, a signal light beam splitting module, a phase modulation module and an amplitude demodulation module; The second propagation module is optically connected to the signal light splitting module, the signal light splitting module is optically connected to the phase modulation module, and the signal input end of the amplitude demodulation module is connected to the signal output end of the signal light splitting module; The first propagation module is connected to the second propagation module in optical communication.

2. The reverse modulation full-duplex communication device based on phase and amplitude modulation according to claim 1, characterized in that: The first propagation module includes an optical fiber circulator and an optical antenna 1; The second propagation module includes an optical antenna 2; The signal transmission end of the optical antenna 1 is connected to the signal transmission end of the optical fiber circulator; The optical fiber circulator is used to send the signal light from the amplitude modulation module to the optical antenna 1, and send the signal light from the optical antenna 2 to the phase demodulation module; The emission angles of the optical antenna 1 and the optical antenna 2 correspond.

3. The reverse modulation full-duplex communication device based on phase and amplitude modulation according to claim 2, characterized in that: The laser splitting module includes a laser and an optical fiber splitter; The signal input end of the optical fiber splitter is connected to the signal output end of the laser, and the signal output end is connected to the amplitude modulation module and the phase demodulation module respectively; The signal light beam splitting module comprises a beam splitter, and the beam splitter is arranged on a side of the optical antenna 2 away from the optical antenna 1.

4. The reverse modulation full-duplex communication device based on phase and amplitude modulation according to claim 3, characterized in that: The amplitude modulation module includes: an acousto-optic modulator, a first driver and a fiber amplifier; The signal input end of the acousto-optic modulator is respectively connected to the signal output end of the optical fiber splitter and the first driver, and the signal output end is connected to the signal input end of the optical fiber amplifier; The signal input terminal of the first driver inputs a first modulation signal; The amplitude demodulation module includes: a first erbium-doped fiber amplifier and a first optical detector; The first erbium-doped fiber amplifier is arranged in the signal light direction of the beam splitter; The signal input end of the first erbium-doped fiber amplifier is connected to the signal output end of the beam splitter, and the signal output end is connected to the signal input end of the first photodetector; The signal output terminal of the first light detector outputs a first modulated signal.

5. The reverse modulation full-duplex communication device based on phase and amplitude modulation according to claim 3, characterized in that: The phase modulation module includes: a focusing lens, a piezoelectric ceramic and a second driver; The focusing lens and the second optical antenna are respectively arranged on both sides of the beam splitter, and the piezoelectric ceramic is arranged at the focus of the focusing lens away from the side of the beam splitter; The signal input end of the focusing lens is connected to the signal output end of the beam splitter and the piezoelectric ceramic respectively; The signal input end of the piezoelectric ceramic is respectively connected to the focusing lens and the signal output end of the second driver, and the signal output end is connected to the signal input end of the focusing lens; The signal input terminal of the second driver inputs a second modulation signal; The phase demodulation module includes: a second erbium-doped fiber amplifier, a polarization controller, an optical coupler, a second optical detector and a signal processing unit; The signal input end of the second erbium-doped fiber amplifier is connected to the signal output end of the fiber circulator, and the signal output end is connected to the signal input end of the optical coupler; The signal output end of the polarization controller is connected to the signal input end of the optical coupler, and the signal input end is connected to the signal output end of the optical fiber splitter; The signal input end of the second light detector is connected to the signal output end of the optical coupler, and the signal output end is connected to the signal input end of the signal processing unit; The signal output terminal of the signal processing unit outputs a second modulated signal.

6. A reverse modulation full-duplex communication method based on phase and amplitude modulation, using the reverse modulation full-duplex communication device based on phase and amplitude modulation according to any one of claims 1 to 5, characterized in that: include: In simplex communication from the interrogator to the reverse modulator: On the inquiry side, Obtain a first light beam and a second light beam through a laser splitting module; The amplitude modulation module performs amplitude modulation on the first light beam according to the first modulation signal, and transmits the amplitude modulated signal light to the second propagation module at the reverse modulation end through the first propagation module; At the reverse modulation end, The signal light after amplitude modulation is split by a signal light splitting module to obtain a first signal light beam and a second signal light beam; Performing photoelectric detection on the first signal light through an amplitude demodulation module to obtain a restored first modulation signal; In simplex communication from the reverse modulating end to the interrogating end: At the reverse modulation end, Phase modulating the second signal light according to the second modulation signal through the phase modulation module, and reflecting the phase-amplitude modulated signal light back to the first propagation module at the interrogation end through the second propagation module; On the inquiry side, The phase demodulation module performs phase demodulation on the phase-amplitude modulated signal light according to the second light beam to obtain a restored second modulated signal.

7. The reverse modulation full-duplex communication method based on phase and amplitude modulation according to claim 6, characterized in that: The amplitude modulation of the first light beam according to the first modulation signal by the amplitude modulation module includes: The first driver drives the acousto-optic modulator according to the magnitude of the first modulation signal to perform amplitude modulation on the first light beam. The expression is as follows: ， in, is the phase constant of the amplitude modulated light, is the frequency of the amplitude modulated light, is the amplitude constant of the amplitude modulated light, is the first modulation signal.

8. The reverse modulation full-duplex communication method based on phase and amplitude modulation according to claim 7, characterized in that: The step of performing photoelectric detection on the first signal light beam through the amplitude demodulation module to obtain a restored first modulation signal includes: amplifying the first signal light by the first erbium-doped fiber amplifier and transmitting the amplified signal light to the first light detector; The first light signal beam is photoelectrically detected by the first light detector, and the expression of the output photocurrent is as follows: ， in, is the photocurrent output by the first photodetector, is the photodetector responsivity in A / W, is a constant; The output of the first modulation signal is obtained according to the output photocurrent.

9. The reverse modulation full-duplex communication method based on phase and amplitude modulation according to claim 7, characterized in that: The phase modulation of the second signal light beam according to the second modulation signal by the phase modulation module includes: The second driver drives the piezoelectric ceramic to vibrate according to the magnitude of the second modulation signal, and phase-modulates the second signal light. The intensity of the optical field after phase-amplitude modulation The expression is as follows: ， in, is the second modulation signal.

10. The reverse modulation full-duplex communication method based on phase and amplitude modulation according to claim 9, characterized in that: The method of performing phase demodulation on the phase-amplitude modulated signal light according to the second light beam by the phase demodulation module to obtain the restored second modulated signal includes: amplifying the incident phase-amplitude modulated signal light through the second erbium-doped fiber amplifier and transmitting it to the optical coupler; The polarization controller adjusts the polarization state of the incident second light beam so that its polarization state is consistent with the signal light after phase-amplitude modulation, and the adjusted laser beam is emitted to the optical coupler, wherein the optical electric field intensity of the second light beam after the polarization state adjustment is The expression is as follows; ， in, is the phase constant of the second beam after polarization state adjustment, is the frequency of the second beam after polarization state adjustment, is the amplitude constant of the second light beam after polarization state adjustment; The amplified phase-amplitude modulated signal light and the second light beam after polarization state adjustment are coupled by the optical coupler, and the coupled signal light is emitted to the second light detector. The expression is as follows: ， in, is a constant, is the signal optical power after phase-amplitude modulation, is the power of the second light beam after polarization state adjustment; The coupled signal light is coherently detected by the second photodetector to output a photocurrent, and the photocurrent is sent to a signal processing unit, wherein the expression of the output photocurrent is: ， in, is the photocurrent output by the second photodetector, is the photodetector responsivity, in A / W; The signal processing unit obtains the output of the second modulation signal according to the photocurrent, and the calculation formula is as follows: 。

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