CN116527156A - Coherent laser communication diversity receiving system and method of self-adaptive atmosphere channel - Google Patents
Coherent laser communication diversity receiving system and method of self-adaptive atmosphere channel Download PDFInfo
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Abstract
The invention relates to the technical field of atmospheric laser communication, and discloses a coherent laser communication diversity receiving system and method of a self-adaptive atmospheric channel, wherein the system comprises N optical amplifiers and N90 optical amplifiers 0 Optical mixer, N phase error modules, a phase error selection module, an optical phase-locked loop, a residual phase noise compensation module, a coherent combining module, each 90 0 The optical mixer is used for receiving one path of signal light, the output end of the ith path of optical amplifier and the ith path 90 0 The optical mixer, the ith phase error module, the phase error selection module, the optical phase-locked loop and the input end of the ith optical amplifier are sequentially connected, and the ith optical amplifier are sequentially connected with the input end of the ith optical amplifier and the ith optical amplifier 90 0 The optical mixer, the ith path of phase error module, the residual phase noise compensation module and the coherent combining module are sequentially connected. The invention solves the problems of the prior art that the coherent laser communication is optically phase-locked under the atmosphere channelLow stability, poor robustness of diversity reception, etc.
Description
Technical Field
The invention relates to the technical field of atmospheric laser communication, in particular to a coherent laser communication diversity receiving system and method of a self-adaptive atmospheric channel.
Background
The laser communication has the advantages of high communication speed, strong anti-interference capability, no need of spectrum application, high confidentiality and the like, and has wide application prospect in the fields of satellite communication, stratosphere communication, 5G/6G communication, laser radio frequency integrated communication, near-earth building communication and the like. Different from a low orbit channel, a space environment and the like which are ideal for satellite communication, when a laser signal is transmitted in an atmosphere channel, the laser signal is influenced by factors such as atmosphere turbulence, atmosphere scattering and absorption, cloud and fog and the like, so that the optical signal generates random fading and attenuation. For channel attenuation, this can be overcome by increasing the transmit optical power, increasing the receive sensitivity, etc. However, random fading and fluctuation caused by atmospheric turbulence reach about 10-40dB, which is extremely easy to cause link interruption and reduces the transmission reliability of laser communication in an atmospheric channel.
Generally, although fluctuation of the air channel is remarkable, the air channel is weaker in channel correlation than wireless communication, microwave communication, and the like, and is also advantageous. Taking a typical near-earth atmospheric channel (a 1km link at moderate turbulence) as an example, the coherence length of an atmospheric channel is of the order of 5-10cm, which means that the different paths of the atmospheric channel exhibit independent, uncorrelated, low crosstalk characteristics. Therefore, the receiver can adopt a plurality of receiving antennas to realize diversity reception, thereby inhibiting the influence of atmospheric turbulence and further improving the reliability of atmospheric laser communication. Therefore, the diversity receiving system based on single-shot multi-receiver has been widely studied in atmospheric laser communication due to the advantages of simple structure, mature signal combining algorithm and the like.
In recent years, laser communication based on a coherent system has been widely studied, and transmission verification has been performed in remote atmospheric laser communication. Theoretical research [ 1 ] (n.Perlot. Turbo-induced fading probability in coherent optical communication through the atm sphere. Applied Optics,2007,46 (29)) discusses the feasibility of atmospheric dry laser communication (BPSK signals) under small aperture reception. Theoretical research [ 2 ] (Jing Sun, purifying Huang, zhushi Yao, jingzhong Guo.adaptive digital combining for coherent free space optical communications with spatial diversity receptivity. Optics communications.2019, 44.) simulates diversity reception performance of atmospheric coherent laser communication, but the adopted digital coherence technique has the disadvantages of weaker anti-frequency difference, higher power consumption and the like. The prior art [ 3 ] (Zhou Zunzhen, zhou Haijun, xie Weilin, qin Jie, dong Yi.10-Gb/s homodyne receiver based on Costas loop with enhanced dynamic performance.IEEE International Conference on Optical Communications and Networks (ICOCN), 2017.) adopts an optical phase locking technique to realize homodyne coherent reception of BPSK signals, and can compensate a large frequency difference (40 GHz range) between signal light and local oscillator light in real time, but does not consider the influence of an atmospheric channel, how to apply to a diversity receiving system, and the like. Experimental studies [ 4 ] (Robert Lange, berry Smutny, bernhard Wandernoth, reinhard Czichy, dirk giggenbach.142km,5.625Gbps Free-space optical link based on homodyne BPSK modulation. Process of SPIE,2006,6105.) demonstrate the feasibility of remote coherent laser communication under an atmospheric channel, but observe that the optical power fluctuation under an atmospheric channel is more pronounced (20-40 dB), instability of optical phase locking, burst interruption of the laser communication link, etc. Therefore, the problems of improving the stability of optical phase locking of coherent laser communication under an atmospheric channel, the robustness of diversity reception and the like are particularly urgent, and the problems are also the problems to be solved in long-distance atmospheric laser communication.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a coherent laser communication diversity receiving system and method of a self-adaptive atmosphere channel, which solve the problems of low stability of optical phase lock of coherent laser communication under the atmosphere channel, poor robustness of diversity reception and the like in the prior art.
The invention solves the problems by adopting the following technical scheme:
a coherent laser communication diversity receiving system of self-adaptive atmosphere channel comprises N optical amplifiers, N900 optical mixers, N phase error modules, a phase error selection module, an optical phase-locked loop, a residual phase noise compensation module and a coherent combining module, wherein each 900 optical mixer is used for receiving one path of signal light, the output end of the ith optical amplifier, the ith 900 optical mixer, the ith phase error module, the phase error selection module and the optical phase-locked loopThe input ends of the loop and the ith optical amplifier are sequentially connected, and the ith optical amplifier are sequentially connected with the 90 th optical amplifier 0 The optical mixer, the ith path of phase error module, the residual phase noise compensation module and the coherent combining module are connected in sequence; wherein i is more than or equal to 1 and less than or equal to N, i is an integer, N is more than or equal to 2, and N is an integer.
As a preferable technical scheme, the phase error module comprises two balance detectors and a phase frequency detector, wherein the two balance detectors are respectively marked as a first balance detector and a second balance detector, the first balance detector and the second balance detector are respectively connected with a 900 optical mixer, and the first balance detector, the phase frequency detector and the second balance detector are sequentially connected.
As a preferred solution, the phase error module further comprises a first low-pass filter connected to the phase frequency detector.
As a preferred solution, the phase error selection module comprises a channel selector connected to the first low-pass filter.
As a preferred solution, the phase error selection module further comprises a second low pass filter connected to the channel selector.
As a preferable technical scheme, the residual phase noise compensation module comprises N data selectors, N third low-pass filters, a fanout device and N-1 phase difference compensation modules, wherein the 1 st data selector is connected with the second low-pass filter, the 1 st data selector, the 1 st third low-pass filter and the fanout device are sequentially connected, the i th data selector, the i th third low-pass filter and the i th phase difference compensation module are sequentially connected, and the fanout device is connected with the i th phase difference compensation module; wherein i is not less than 2.
As a preferred technical solution, the coherent combining module includes a maximum signal-to-noise ratio combiner, where the maximum signal-to-noise ratio combiner is used for diversity combining of the digital signals output by each phase difference compensating module.
As a preferable technical scheme, the filter further comprises a matched filter, and the residual phase noise compensation module, the matched filter and the maximum signal-to-noise ratio combiner are sequentially connected.
As a preferable technical scheme, the system further comprises a channel estimator, and a residual phase noise compensation module, the channel estimator, a matched filter and a maximum signal-to-noise ratio combiner are sequentially connected.
A coherent laser communication diversity receiving method of a self-adaptive atmosphere channel adopts the coherent laser communication diversity receiving system of the self-adaptive atmosphere channel, which comprises the following steps:
s1, framing the transmitted baseband data and pilot frequency data according to the slow-changing characteristic of an atmospheric channel;
s2, receiving signal light, carrying out coherent mixing on each branch signal light and local oscillation light on a 900 optical mixer, converting the signal light and the local oscillation light into two paths of data with phase errors and phase errors through a phase error module, then accessing the phase errors into a phase error selection module, feeding back and controlling an optical phase-locked loop, accessing the two paths of data into a residual phase noise compensation module for processing, and generating a digital signal;
s3, the digital signals generated by the branches are respectively connected to a coherent combination module for processing and then output, and diversity reception of the atmospheric coherent laser communication is realized.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention can be applied to the scenes of atmosphere laser communication, laser radio frequency integrated communication, satellite laser communication, stratospheric laser communication and the like, and fully utilizes the diversity gain of the laser communication, thereby improving the reliability of the atmosphere laser communication;
(2) In the invention, only one path of optical phase-locked loop is needed to compensate the large frequency difference (GHz magnitude) existing in the coherent laser communication, and the outputted local oscillation light is distributed to be used for the coherent demodulation of other branch signal lights, so that the use of multiple paths of optical phase-locked loops is avoided, and the complexity of a coherent laser communication diversity receiving system is greatly reduced.
(3) In the invention, the phase error information of the feedback optical phase-locked loop is not provided by a certain fixed branch, but is provided by a branch with the highest signal-to-noise ratio output by monitoring the state of each branch by the phase error selection module, thereby avoiding the problems of optical phase locking failure, instability and the like caused by deep fading (10-40 dB) of a channel.
(4) In the invention, the residual phase difference compensation of each branch does not take the demodulation data of a certain fixed branch as a reference, but selects the branch data with the maximum signal-to-noise ratio in the residual phase noise compensation module as a phase reference, thereby avoiding the influence of extra phase noise introduced by the optical phase lock of the fixed branch under an atmospheric channel and improving the robustness of diversity reception.
(5) In the invention, the coherent combining module adopts the technologies of channel estimation, matched filtering, maximum signal to noise ratio combining and the like to realize the coherent combining of multipath signals, and has strong environmental adaptability.
(6) The invention can flexibly adjust the pilot frequency quantity of the transmitted data frame to adapt to diversity reception under different atmosphere channel (weak-medium-strong atmosphere turbulence) conditions.
(7) The invention is transparent to the modulation format of the signal, and is compatible with the coherent diversity reception of modulation formats such as on-off keying (OOK), binary phase keying modulation (BPSK), differential Phase Shift Keying (DPSK), quaternary Quadrature Phase Shift Keying (QPSK) and the like.
(8) The invention adopts mixed analog coherent receiving (optical phase-locked loop to realize homodyne coherent) and digital combining technology (residual phase noise compensation and coherent combining), compared with a pure digital phase-locked loop, the invention greatly reduces the system power consumption of coherent laser and is easy to popularize to a multi-channel (N > 4) coherent diversity receiving system.
Drawings
Fig. 1 is a schematic structural diagram of a coherent laser communication diversity receiving system of an adaptive atmosphere channel;
FIG. 2 is a schematic diagram of a phase error module;
FIG. 3 is a schematic diagram of a phase error selection module;
FIG. 4 is a schematic diagram of a residual phase noise compensation module;
fig. 5 is a schematic structural diagram of a coherent combining module.
The reference numerals in the drawings and their corresponding names: 1. the optical amplifier comprises an optical amplifier, 2, 900 optical mixers, 3, a phase error module, 4, a phase error selection module, 5, an optical phase-locked loop, 6, a residual phase noise compensation module, 7, a coherent combination module, 31, a balance detector, 32, a phase frequency detector, 33, a first low-pass filter, 41, a channel selector, 42, a second low-pass filter, 61, a data selector, 62, a third low-pass filter, 63, a fan-out device, 64, a phase difference compensation module, 71, a channel estimator, 72, a matched filter, 73, a maximum signal-to-noise ratio combiner, 311, a first balance detector, 312 and a second balance detector.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
Example 1
As shown in fig. 1 to 5, the present invention aims to improve the stability of coherent laser communication under an atmospheric channel, and proposes a coherent laser communication diversity receiving system with an adaptive atmospheric channel. The system is characterized in that only one optical phase-locked loop is used for compensating large frequency difference faced by coherent laser communication, and the local oscillation light is output for homodyne coherent demodulation of each branch, so that each branch is prevented from using one optical phase-locked loop. The system is characterized in that the phase error information of the optical phase-locked loop is not provided by a certain fixed branch, but is provided by a branch which is monitored by the phase error selection module in real time and outputs the highest signal-to-noise ratio, thereby avoiding failure, instability and the like of the optical phase-locking caused by an atmospheric channel. The system is characterized in that the residual phase difference compensation of each branch is not based on the demodulation data of a certain fixed branch, but the branch data with the maximum signal-to-noise ratio is selected as the phase reference in the residual phase noise compensation module to compensate the phase difference of other branches, thereby improving the robustness of diversity reception. Because only one path of optical phase-locked loop, a highly reliable phase error selection module, a high-robustness residual phase noise compensation module, a multi-path signal synchronization and combination algorithm and the like are needed, the reliability of atmospheric coherent laser communication is improved.
A coherent laser communication diversity receiving system of a self-adaptive atmosphere channel comprises an optical coherent receiving branch, an optical phase-locked loop, a phase error selection module, a residual phase noise compensation module and a coherent combining module.
Further, the optical coherent reception and reception component is composed of an optical amplifier, a 90 DEG optical mixer and a phase error module. The output port of the optical amplifier is connected with the local oscillation optical input port of the 90-degree optical mixer, and the output port of the 90-degree optical mixer is connected with the input port of the phase error module.
Further, the connection relation between the optical coherent receiving branch and other modules is as follows: one path of the output port of the phase error module of each branch is connected with the input port of the phase error selection module, the other path of the output port of the phase error selection module is connected with the input port of the residual phase noise compensation module, the output port of the phase error selection module is connected with the input port of the optical phase-locked loop, the output port (local oscillation light) of the optical phase-locked loop is connected with the input port of the optical amplifier, and the output end (digital signal) of the residual phase noise compensation module is connected with the coherent combining module to output a digital signal received by diversity, so that the diversity reception of coherent laser communication is realized.
The light field scalar of signal light 1, signal light 2, …, signal light N-1, and signal light N are respectively:
wherein the frequencies of the signal lights are omega s The method comprises the steps of carrying out a first treatment on the surface of the The optical powers are respectively The optical phases are phi respectively s，1 (t)、φ s，2 (t)、φ s,N-1 (t)、φ s,N (t). Due to the influence of the atmospheric channel, each optical signal undergoes slow-changing and mutually independent random channel fading, and the optical phase undergoes slow-changing and mutually independent phase distortion and fluctuation.
The light field scalar of the local oscillation light output by the optical phase-locked loop is:
wherein the optical power isOptical phase is phi LO (t)。
The signal light of each branch is mixed with local oscillation light in a coherent mode, and the phase error of the signal light 1 is output and fed back to the optical phase-locked loop by the phase error selection module under the assumption that the phase difference signal-to-noise ratio of the corresponding branch of the signal light 1 is highest in a certain time period. Therefore, the optical phase-locked loop keeps the frequency and phase of the local oscillation light consistent with the signal light 1, namely:
at this time, the phase error module demodulates the digital baseband signal corresponding to the signal light 1, and the local oscillation light output by the optical phase-locked loop is used for coherent detection of the signal light 2, …, the signal light N-1 and the signal light N after being split. Correspondingly, the photocurrent signals output by the phase error modules (taking in-phase I path as an example) of each branch are
Wherein R is the responsivity of the balanced detector, phi 2,0 (t)、φ N-1,0 (t)、φ N,0 And (t) is the phase offset generated by the local oscillation light after passing through an optical fiber, an optical amplifier, a 90-degree optical mixer and the like and the signal light 2, the signal light N-1 and the signal light N respectively.
The invention relates to a coherent laser communication diversity receiving method of a self-adaptive atmosphere channel, which comprises the following steps:
step one: and framing the transmitted baseband data and pilot data according to the slow-changing characteristic of the atmospheric channel.
Step two: taking the receiving signal light k (k epsilon (1, 2, the first, N-1, N)) as an example, the branch signal light k and the local oscillator light are subjected to coherent mixing on a 900 optical mixer, are converted into I/Q path data with phase errors and phase errors through a phase error module, then the phase errors are connected into a phase error selection module and then are fed back to control an optical phase-locked loop, and the I/Q path data are connected into a residual phase noise compensation module to carry out low-pass filtering, phase noise compensation and other processes, and stable digital signals are generated.
Step three: the digital signals generated by each branch are respectively connected to a coherent combining module, channel estimation and matched filtering of each signal are carried out according to pilot frequency of each frame of data, and finally digital signals are output through maximum signal-to-noise ratio combination, so that diversity reception of atmospheric coherent laser communication is realized.
Compared with the prior art, the invention has the advantages that:
(1) The invention can be applied to the scenes of atmosphere laser communication, laser radio frequency integrated communication, satellite laser communication, stratospheric laser communication and the like, and fully utilizes the diversity gain of the laser communication, thereby improving the reliability of the atmosphere laser communication;
(2) In the invention, only one path of optical phase-locked loop is needed to compensate the large frequency difference (GHz magnitude) existing in the coherent laser communication, and the outputted local oscillation light is distributed to be used for the coherent demodulation of other branch signal lights, so that the use of multiple paths of optical phase-locked loops is avoided, and the complexity of a coherent laser communication diversity receiving system is greatly reduced.
(3) In the invention, the phase error information of the feedback optical phase-locked loop is not provided by a certain fixed branch, but is provided by a branch with the highest signal-to-noise ratio output by monitoring the state of each branch by the phase error selection module, thereby avoiding the problems of optical phase locking failure, instability and the like caused by deep fading (10-40 dB) of a channel.
(4) In the invention, the residual phase difference compensation of each branch does not take the demodulation data of a certain fixed branch as a reference, but selects the branch data with the maximum signal-to-noise ratio in the residual phase noise compensation module as a phase reference, thereby avoiding the influence of extra phase noise introduced by the optical phase lock of the fixed branch under an atmospheric channel and improving the robustness of diversity reception.
(5) In the invention, the coherent combining module adopts the technologies of channel estimation, matched filtering, maximum signal to noise ratio combining and the like to realize the coherent combining of multipath signals, and has strong environmental adaptability.
(6) The invention can flexibly adjust the pilot frequency quantity of the transmitted data frame to adapt to diversity reception under different atmosphere channel (weak-medium-strong atmosphere turbulence) conditions.
(7) The invention is transparent to the modulation format of the signal, and is compatible with the coherent diversity reception of modulation formats such as on-off keying (OOK), binary phase keying modulation (BPSK), differential Phase Shift Keying (DPSK), quaternary Quadrature Phase Shift Keying (QPSK) and the like.
(8) The invention adopts mixed analog coherent receiving (optical phase-locked loop to realize homodyne coherent) and digital combining technology (residual phase noise compensation and coherent combining), compared with a pure digital phase-locked loop, the invention greatly reduces the system power consumption of coherent laser and is easy to popularize to a multi-channel (N > 4) coherent diversity receiving system.
Example 2
As further optimization of embodiment 1, as shown in fig. 1 to 5, this embodiment further includes the following technical features on the basis of embodiment 1:
referring to fig. 1, the present invention proposes a coherent laser communication diversity receiving system of adaptive atmospheric channel, which comprises an optical amplifier 1, 900, an optical mixer 2, a phase error module 3, a phase error selection module 4, an optical phase-locked loop 5, a residual phase noise compensation module 6 and a coherent combining module 7. In this example, the laser wavelength is 1550nm, the modulation format is BPSK, the total length of each frame of data is 2048 bits, the communication rate is 10Gbps, the output optical power of the optical amplifier 1 is 48mw, the 900 optical mixer 2 outputs I, Q two paths of optical signals, and the phase error module 3, the phase error selection module 4, the residual phase noise compensation module 6 and the coherent combining module all support high-speed signal transmission of DC-10 Gbps.
The phase error module 3 outputs phase error and I/Q path data, and is mainly composed of a balance detector 31 (including a first balance detector 311 and a second balance detector 312), a phase frequency detector 32 and a first low-pass filter 33. The balance detector 31 (bandwidth is 10 GHz) is respectively located in two paths I, Q and generates I/Q path data, and the phase frequency detector 32 generates error information including a frequency difference and a phase difference and generates phase error information after smoothing by the first low-pass filter 33.
The phase error selection module 4 mainly comprises a channel selector 41 and a second low-pass filter 42. Due to random deep fading (10-40 dB) of the atmospheric channel, single-branch signal light is easily interrupted, which also results in unstable optical phase lock state of the single branch, deterioration of residual phase noise, and the like. The probability of simultaneous deep fade or disruption of multiple signal light is low due to the coherent nature of the atmospheric channel. Therefore, in the present module, instead of using the phase error of a certain fixed branch, the phase error information of all branches is collected into the channel selector 41, the signal to noise ratio of the phase error of each branch is monitored in real time, the phase error of the branch with the largest signal to noise ratio is selected through the gating information S0 and S1, and the phase error is fed back to the optical phase-locked loop after being smoothed by the second low-pass filter 42. For BPSK signals on the order of Gbps, the atmospheric channel, phase error, etc. can be considered a slow-varying process. Therefore, in the ms-magnitude time, the signal light power and the amplitude of the phase error can be considered to be almost unchanged, and frequent selection and switching of the phase error signal are avoided. In the scheme, the channel selector adopts high-speed AD/DA and FPGA to realize the functions of phase error signal acquisition, signal-to-noise ratio comparison, phase error gating and the like, and compares the signal-to-noise ratio of the phase error of each branch every 5ms, so that the problems of optical phase locking failure, instability and the like caused by an atmospheric channel are avoided.
The optical phase-locked loop 5 adopts an optical phase locking technology, the frequency and the phase of the output local oscillation light are the same as those of the signal light to be locked, the frequency difference existing in the coherent laser communication can be compensated in real time, and the local oscillation light is distributed to be used for coherent demodulation of other branch signal light. The center wavelength of the local oscillation laser output by the optical phase-locked loop is 1550nm, the tuning range is up to 40GHz, and the frequency difference range of laser communication is covered. Because the capturing time of the phase-locked loop is 3-10ms, in order to avoid frequent unlocking and locking processes, the phase error selection module 4 can also adopt the technologies of holding, delay comparison and the like at the algorithm level, so that frequent switching is avoided as much as possible.
The residual phase noise compensation module 6 is composed of a data selector 61, a third low-pass filter 62, a fanout 63 and a phase difference compensation module 64. When the optical phase-locked loop and the signal light of a certain branch are locked, the frequency of the output local oscillation light is the same as that of the signal light of other branches, but the phases of the signal lights of all the branches show certain randomness under the atmosphere channel, and the distributed local oscillation light also introduces additional random phases through different optical amplifiers, 900 optical mixers, optical fiber devices and the like. Therefore, residual phase noise still exists between other paths of signal light and local oscillation light, and the demodulated digital signal also presents larger random fluctuation and needs to be compensated for the second time. In general, the optical phase-locked loop 5 can implement homodyne coherent demodulation of signal light of a certain branch, that is, the signal-to-noise ratio of the digital signal of the branch is maximum, and the residual phase noise is about 0. The gating information S0 and S1 output by the phase error selection module 4 is used to select the digital signal of the branch in the data selector 61, and the digital signal is input as a reference to the phase difference compensation module 64 through the third low-pass filter 62 and the fanout 63 to compensate the residual phase noise in the digital signals of other branches.
In order to reduce the complexity of the system, the phase difference compensation module 64 of the present invention adopts a classical phase noise compensation algorithm (maximum likelihood phase estimation, M times of multiplication, etc.) to correct the phase deviation existing in other branch digital signals, so as to realize the stable output of each branch digital signal. In this example, the bandwidths of the data selector 61, the third low-pass filter 62 and the fanout 63 are 10GHz, and the phase difference compensation module 64 adopts 2 multiplications, a digital domain phase-locked loop and a soft decision mode.
The coherent combining module 7 is composed of a channel estimator 71, a matched filter 72 and a maximum signal to noise ratio combiner 73. The module is used for coherent combination of multipath baseband digital signals so as to realize multipath signal synchronization and diversity reception of coherent laser communication. In the channel estimator 71, the atmospheric channel estimation is performed using pilots of each frame of data, and the length of the pilot sequence is approximately 1/10 to 1/5 of the length of the data, so as to satisfy both high-precision atmospheric channel estimation and high-speed transmission requirements. Because the coherence time of the atmosphere channel is in the order of ms and the communication speed is up to the order of Gbps, high-precision atmosphere channel estimation can be realized according to 5ms intervals. The matched filter 72 not only realizes the maximum signal-to-noise ratio output of the digital signals of each path, but also extracts time synchronization information to facilitate the maximum signal-to-noise ratio combiner 73 to realize the coherent combining output of the multiple paths of signals, thereby realizing the optimal diversity receiving gain.
As described above, the present invention can be preferably implemented.
All of the features disclosed in all of the embodiments of this specification, or all of the steps in any method or process disclosed implicitly, except for the mutually exclusive features and/or steps, may be combined and/or expanded and substituted in any way.
The foregoing description of the preferred embodiment of the invention is not intended to limit the invention in any way, but rather to cover all modifications, equivalents, improvements and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. A coherent laser communication diversity receiving system of a self-adaptive atmosphere channel is characterized by comprising N optical amplifiers (1) and N90 optical amplifiers 0 An optical mixer (2), N phase error modules (3), a phase error selection module (4), an optical phase-locked loop (5), a residual phase noise compensation module (6), a coherent combining module (7), each 90 0 The optical mixer (2) is used for receiving one path of signal light, the output end of the ith path of optical amplifier (1) and the ith path of optical amplifier (90) 0 The optical mixer (2), the ith phase error module (3), the phase error selection module (4), the optical phase-locked loop (5) and the input end of the ith optical amplifier (1) are sequentially connected, and the ith optical amplifier (1) and the ith optical amplifier (90) 0 The optical mixer (2), the ith phase error module (3), the residual phase noise compensation module (6) and the coherent combination module (7) are connected in sequence; wherein i is more than or equal to 1 and less than or equal to N, i is an integer, N is more than or equal to 2, and N is an integer.
2. A coherent laser communication diversity reception system of an adaptive atmospheric channel according to claim 1, characterized in that the phase error module (3) comprises two balanced detectors (31), a phase frequency detector (32), the two balanced detectors (31) being denoted as a first balanced detector (311) and a second balanced detector (312), respectively, the first balanced detector (311) and the second balanced detector (312) being denoted as a first balanced detector (311) and a second balanced detector (312), respectively, being denoted as a third balanced detector (90) 0 The optical mixer (2) is connected, and the first balance detector (311), the phase frequency detector (32) and the second balance detector (312) are sequentially connected.
3. A coherent laser communication diversity reception system of an adaptive atmospheric channel according to claim 2, characterized in that the phase error module (3) further comprises a first low pass filter (33) connected to the phase frequency detector (32).
4. A coherent laser communication diversity reception system of an adaptive atmospheric channel according to claim 3, characterized in that the phase error selection module (4) comprises a channel selector (41) connected to the first low-pass filter (33).
5. A coherent laser communication diversity reception system of an adaptive atmospheric channel according to claim 4, characterized in that the phase error selection module (4) further comprises a second low pass filter (42) connected to the channel selector (41).
6. The adaptive atmospheric channel coherent laser communication diversity receiving system according to claim 5, wherein the residual phase noise compensation module (6) comprises N data selectors (61), N third low pass filters (62), a fanout (63), N-1 phase difference compensation modules (64), the 1 st data selector (61) is connected with the second low pass filter (42), the 1 st data selector (61), the 1 st third low pass filter (62), the fanout (63) are sequentially connected, the i th data selector (61), the i th third low pass filter (62), the i th phase difference compensation module (64) are sequentially connected, and the fanout (63) is connected with the i th phase difference compensation module (64); wherein i is not less than 2.
7. A coherent laser communication diversity reception system of an adaptive atmospheric channel according to claim 6, characterized in that the coherent combining module (7) comprises a maximum signal-to-noise ratio combiner (73), the maximum signal-to-noise ratio combiner (73) being used for diversity combining of the digital signals output by the respective phase difference compensation modules (64).
8. A coherent laser communication diversity reception system of an adaptive atmospheric channel according to claim 7, further comprising a matched filter (72), the residual phase noise compensation module (6), the matched filter (72) and the maximum signal to noise combiner (73) being connected in sequence.
9. A coherent laser communication diversity reception system according to claim 8, further comprising a channel estimator (71), wherein the residual phase noise compensation module (6), the channel estimator (71), the matched filter (72) and the maximum signal to noise ratio combiner (73) are connected in sequence.
10. A coherent laser communication diversity reception method of an adaptive atmosphere channel, characterized in that a coherent laser communication diversity reception system of an adaptive atmosphere channel according to any one of claims 1 to 9 is employed, comprising the steps of:
s1, framing the transmitted baseband data and pilot frequency data according to the slow-changing characteristic of an atmospheric channel;
s2, receiving the signal light, and enabling the signal light and the local oscillation light of each branch to be in 90 degrees 0 The optical mixer (2) carries out coherent mixing, the two paths of data with phase errors and the phase errors are converted by the phase error module (3), then the phase errors are connected into the phase error selection module (4) and then the optical phase-locked loop (5) is controlled in a feedback manner, and the two paths of data are connected into the residual phase noise compensation module (6) for processing, and digital signals are generated;
s3, the digital signals generated by the branches are respectively connected to a coherent combining module (7) for processing and then output, so that diversity reception of the atmospheric coherent laser communication is realized.
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