Non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment

Abstract

The application discloses a non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment, and belongs to the technical field of free space optical communication. The method is aimed at a single-transmitting and single-receiving scene, and comprises the following steps: M pieces of to-be-transmitted information are respectively encoded by using pre-defined and mutually different unique decodable code (UDC) code word sets, so that M code words are obtained; after being converted into M pieces of optical signals by intensity modulation, the M pieces of optical signals are combined into one composite optical signal by a mode combiner and are transmitted through an atmospheric channel; an optical signal received by a receiving end is directly photoelectrically converted without mode separation; a non-orthogonal weighted superposition relationship established by inter-mode crosstalk caused by atmospheric turbulence is used to jointly decode and judge the sampled electrical signal in the code word domain, and finally the original information is recovered. The application effectively utilizes the turbulence crosstalk, avoids mode separation loss, and significantly improves the capacity and stability of the system in the daytime strong turbulence environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of free space optical communication, in particular to a non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment. BACKGROUND

[0002] Under daytime conditions, atmospheric turbulence is particularly serious, resulting in more disturbances and wavefront distortions of optical signals during atmospheric propagation. Atmospheric turbulence is caused by uneven distribution of temperature and pressure, and is strongly affected by solar radiation during the day, resulting in drastic changes in ground temperature, thereby intensifying the spatial non-uniformity of the refractive index in the atmosphere. This strong turbulence can cause inter-mode crosstalk to intensify: turbulence causes wavefront distortion, which destroys the phase matching condition between different propagation modes. Mode multiplexing uses orthogonal spatial modes to cooperatively transmit information, and each mode can carry an independent data channel. Orthogonality enables effective multiplexing and demultiplexing between multiple modes. However, when the information carried by each mode passes through the atmospheric channel, the uneven distribution of atmospheric temperature and pressure causes the refractive index to change randomly along the transmission path, causing the phase of the light beam to distort. The distortion of the phase can cause the spectral efficiency to disperse when demodulated at the receiving end, causing serious crosstalk between adjacent modes, thereby degrading the system error performance.

[0003] To solve this problem, researchers have proposed correction methods such as channel coding and MIMO equalization. Channel coding encodes data redundantly before transmission, enhancing error detection and correction capabilities. Although coding techniques perform well in reducing error rates, they are complex to implement and require high computational resources. Channel coding requires the addition of redundant information before data transmission, resulting in a decrease in actual transmission efficiency. In addition, the effectiveness of coding techniques depends largely on the complexity of the encoding and decoding algorithms, and complex encoding algorithms require high-performance hardware support, which increases the cost and energy consumption of the system. MIMO equalization uses spatial multiplexing principles to simultaneously transmit and receive multiple independent signals through multiple transmit and receive antennas. The receiving end uses matrix decomposition and equalization algorithms to separate each independent signal, reducing inter-mode crosstalk and effectively reducing crosstalk caused by atmospheric turbulence, but the algorithm is complex.

[0004] In view of the two urgent problems of how to resist inter-mode crosstalk and avoid mode separation loss in the existing mode division multiplexing laser communication system. There is an urgent need for a signal transmission device and method under strong daytime turbulence and strong interference conditions. SUMMARY

[0005] The purpose of the present disclosure is to provide a non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment, which can solve at least one of the technical problems mentioned above. The specific scheme is as follows:

[0006] A non-orthogonal transmission method for daytime strong turbulence and strong interference environment, comprising the following steps:

[0007] M pieces of to-be-transmitted information are encoded by using a set of pre-defined and mutually different unique decodable code (UDC) words respectively, to obtain corresponding M code words;

[0008] The M code words are converted into M pieces of optical signals after intensity modulation;

[0009] The M pieces of optical signals are combined into one composite optical signal, which is transmitted through an atmospheric channel;

[0010] The transmission optical signal of the composite optical signal after transmission through the atmospheric channel is received, and the transmission optical signal is converted into an electrical signal through photoelectric conversion;

[0011] After sampling the electrical signal, joint decoding is performed in the code word domain by using a non-orthogonal weighted superposition relationship, to recover the M pieces of to-be-transmitted information.

[0012] Further, the joint decoding comprises:

[0013] The weight vector of inter-module crosstalk is estimated according to a training sequence;

[0014] The non-orthogonal weighted superposition result of all code words is calculated according to the weight vector, to construct a set of non-orthogonal weighted superposition code word constellation points;

[0015] The corresponding non-orthogonal weighted superposition code word constellation point is determined according to the minimum Euclidean distance criterion;

[0016] The M pieces of to-be-transmitted information are recovered by unique decodable inverse mapping according to the determination result.

[0017] Further, the M pieces of to-be-transmitted information are recovered by unique decodable inverse mapping according to the determination result, comprising:

[0018] The determination result is the corresponding non-orthogonal weighted superposition code word constellation point;

[0019] The M code words are inversely solved according to the non-orthogonal weighted superposition code word constellation point and the weight vector;

[0020] The M pieces of to-be-transmitted information are recovered by unique decodable inverse mapping of the M code words.

[0021] Further, the M pieces of to-be-transmitted information are encoded by using a set of pre-defined and mutually different unique decodable code (UDC) words respectively, to obtain corresponding M code words, comprising:

[0022] The predefined M unique decodable UDC code word sets respectively correspond to M different linear polarization LP modes in one-to-one correspondence;

[0023] The M pieces of to-be-transmitted information are encoded in the corresponding code word sets.

[0024] The application further provides a non-orthogonal transmission device for a daytime strong turbulence and strong interference environment, comprising:

[0025] a transmitting end and a receiving end;

[0026] The transmitting end comprises:

[0027] an encoder component comprising M encoders, respectively used for encoding M pieces of to-be-transmitted information in corresponding unique decodable UDC code word sets to obtain M code words;

[0028] an intensity modulator component comprising M intensity modulators, respectively connected to the M encoders, used for converting the M code words into M pieces of optical signals;

[0029] a mode combiner used for mode combining the M pieces of optical signals into one piece of composite optical signal;

[0030] a transmitting unit used for transmitting the composite optical signal through an atmospheric channel;

[0031] The receiving end comprises:

[0032] a detector used for receiving a transmission optical signal transmitted through the atmospheric channel and converting the transmission optical signal into an electrical signal;

[0033] a joint decoder used for, after sampling the electrical signal, performing joint decoding in a code word domain by using a non-orthogonal weighted superposition relationship to recover the M pieces of to-be-transmitted information.

[0034] Further, the joint decoder comprises:

[0035] a weight value estimation module used for estimating a weight value vector of inter-mode crosstalk according to a training sequence;

[0036] a non-orthogonal weighted superposition code word constellation point construction module used for calculating non-orthogonal weighted superposition results of all code words according to the weight value vector to construct a non-orthogonal weighted superposition code word constellation point set;

[0037] a decision module used for deciding corresponding non-orthogonal weighted superposition code word constellation points according to a minimum Euclidean distance criterion;

[0038] an inverse mapping module used for recovering the M pieces of to-be-transmitted information by unique decodable inverse mapping according to a decision result.

[0039] Further, the inverse mapping module comprises:

[0040] a reverse solution unit, configured to inversely solve M code words from the non-orthogonal weighted superposition code word constellation point and the weight vector;

[0041] a decoding unit, configured to recover the M paths of to-be-transmitted information through unique decodable inverse mapping of the M code words.

[0042] Further, each of the M paths of encoders is bound to one-to-one with M different linear polarization (LP) modes, and encoding is performed in a unique decodable (UDC) code word set of the bound.

[0043] Further, the mode combiner is a photon lantern, configured to couple M linear polarization (LP) modes of the M paths of optical signals into at least a mode fiber.

[0044] Further, the transmitting unit comprises a few-mode optical amplifier, arranged between the mode combiner and the atmospheric channel, and configured to perform power amplification on the composite optical signal and then send the composite optical signal into the atmospheric channel.

[0045] Compared with the prior art, the above scheme of the embodiment of the present application has at least the following beneficial effects:

[0046] 1. The non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment disclosed in the present application creatively utilize turbulence crosstalk to convert it from interference to be suppressed into effective weighted weights that can be used to distinguish information. In combination with the non-orthogonal transmission characteristics of UDC, the channel capacity with a spectral efficiency greater than 1 is realized, and the capacity limit of traditional orthogonal transmission is broken through.

[0047] 2. The non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment disclosed in the present application do not require any mode demultiplexing device at the receiving end, and directly detect the composite optical signal, thereby fundamentally avoiding the optical power loss caused by mode separation, improving the receiving sensitivity and power budget of the system, and saving the expensive and precise mode demultiplexing device and subsequent multi-channel parallel receiving processing circuit, greatly simplifying the optical and hardware structures of the receiver, and reducing the system cost, volume and power consumption.

[0048] 3. The non-orthogonal transmission method and device for daytime strong turbulence and strong interference environment disclosed in the present application are designed for the harsh environment of daytime strong turbulence, and its performance does not depend on the suppression of turbulence, but utilizes the characteristics of turbulence, and therefore shows stronger robustness and stability in this environment.

[0049] 4. The application discloses a non-orthogonal transmission method and device for a daytime strong-turbulence and strong-interference environment, avoids a complex real-time MIMO equalization algorithm, and mainly completes a decoding process by calculating a weighted superposition constellation diagram in a code word domain, so that algorithm complexity is relatively low and engineering implementation is easier. BRIEF DESCRIPTION OF DRAWINGS

[0050] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments consistent with the present disclosure and, together with the specification, serve to explain the principles of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and all other embodiments obtained by those of ordinary skill in the art without creative labor on the basis of these drawings are within the scope of protection of the present disclosure.

[0051] Figure 1 A data transmission and processing schematic diagram of a non-orthogonal transmission device for a daytime strong-turbulence and strong-interference environment is provided for an embodiment of the present application.

[0052] Figure 2 A flowchart of a non-orthogonal transmission method for a daytime strong-turbulence and strong-interference environment is provided for an embodiment of the present application.

[0053] Figure 3 A flowchart of joint decoding in a non-orthogonal transmission method for a daytime strong-turbulence and strong-interference environment is provided for an embodiment of the present application.

[0054] Figure 4 A code word constellation point oscilloscope acquisition result schematic diagram of non-orthogonal weighted superposition in a joint decoding step is provided for an embodiment of the present application.

[0055] Figure 5 A channel capacity curve schematic diagram is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0056] In order to make the purposes, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only some embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present disclosure.

[0057] It is also to be noted that the terms "comprising", "comprises" or any other variation thereof are intended to cover a non-exclusive inclusion, such that a composition or method that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such composition or method. An element proceeded by "comprises a" does not, without further constraints, exclude the presence of additional identical elements in the composition or method that contains the element.

[0058] The accompanying drawings are incorporated in and constitute a part of this specification. Figures 1-5 Detailed description of the alternative embodiments of the application.

[0059] According to the specific embodiment of the application, the present embodiment takes mode number M=3 as an example, i.e. "three-shot" mode. The selected UDC code word set is , , The device uses three linear polarization modes LP01, LP11a and LP11b for transmission. The application only takes mode number 3 as an example for explanation, and the selection of mode number 6 or other values in practical application is the same. The schematic diagram of data transmission and processing is shown in Figure 1 .

[0060] The embodiment of the application provides a non-orthogonal transmission device for a strong daytime turbulence and strong interference environment, and a method for a single-transmission and single-reception scene, comprising a transmitting end and a receiving end.

[0061] The transmitting end comprises:

[0062] An encoder component comprising a 3-way encoder, which can use a digital signal processor (DSP) or a special encoding chip in the prior art, is respectively used for encoding 3-way to-be-transmitted information in a corresponding unique decodable UDC code word set, and outputs 3-way code word signals.

[0063] A strength modulator component comprising 3-way strength modulators, the radio frequency input end of each modulator is connected to the output of one-way encoder, and the optical input end is commonly connected to one laser. Each modulator is configured to modulate one-way code word signal to optical carrier, and output optical signal of specific linear polarization LP mode.

[0064] A mode combiner is used for mode merging of 3-way optical signals, and merging into one-way composite optical signal. In the embodiment of the application, a three-mode photonic lantern is used. The three input ends of the photonic lantern are respectively connected to the optical output ends of the 3-way strength modulators, which are used for efficiently merging 3-way optical signals of different modes, and coupling into a few-mode optical fiber to output one-way composite optical signal.

[0065] The transmitting unit is configured to transmit the composite optical signal through an atmospheric channel. In the embodiment of the present application, the transmitting unit comprises a few-mode optical amplifier and a transmitting telescope antenna. The few-mode optical amplifier is connected to the output end of the photonic lantern, and is configured to amplify the power of the composite optical signal. The transmitting telescope antenna is connected to the few-mode optical amplifier, and is configured to collimate and transmit the amplified composite optical signal into the atmospheric channel.

[0066] The receiving end comprises:

[0067] The detector is configured to receive the transmission optical signal transmitted through the atmospheric channel, and convert the transmission optical signal into an electrical signal. In the embodiment of the present application, a high-speed PIN photodiode is used, which is configured to receive the optical signal transmitted through the atmospheric channel, and directly perform photoelectric conversion to output an electrical signal. In the embodiment of the present application, the optical part of the receiving end device does not contain any mode demultiplexing device, and does not need mode separation, so that the optical power loss caused by mode separation is fundamentally avoided, and the receiving sensitivity and power budget of the system are improved. The expensive and precise mode demultiplexing device and the subsequent multi-channel parallel receiving processing circuit are omitted, so that the optical and hardware structures of the receiver are greatly simplified, and the system cost, volume and power consumption are reduced.

[0068] The joint decoder is configured to, after sampling the electrical signal, perform joint decoding in the code word domain by using the non-orthogonal weighted superposition relationship, and recover the three pieces of to-be-transmitted information. In the embodiment of the present application, a high-speed digital signal processor (DSP) or a field programmable gate array (FPGA) is used to realize the joint decoder, which is connected to the output end of the photodetector, and completes the joint decoding function by executing an algorithm program.

[0069] In the embodiment of the present application, the joint decoder comprises:

[0070] The weight estimation module is configured to estimate the weight vector of the inter-mode crosstalk according to the training sequence.

[0071] The code word constellation point construction module of non-orthogonal weighted superposition is configured to calculate the non-orthogonal weighted superposition result of all code words according to the weight vector, so as to construct a set of code word constellation points of non-orthogonal weighted superposition.

[0072] The decision module is configured to determine the corresponding code word constellation point of non-orthogonal weighted superposition according to the minimum Euclidean distance criterion.

[0073] The inverse mapping module is configured to recover the M pieces of to-be-transmitted information according to the decision result through a uniquely decodable inverse mapping.

[0074] In the embodiment of the present application, the inverse mapping module comprises:

[0075] a reverse solution unit, configured to reversely solve M code words from the non-orthogonal weighted superimposed code word constellation point and the weight vector;

[0076] a decoding unit, configured to recover the M paths of to-be-transmitted information through unique decodable inverse mapping.

[0077] The non-orthogonal transmission device for the daytime strong turbulence and strong interference environment in the embodiment of the application creatively utilizes turbulence crosstalk to convert the interference to be suppressed into effective weighted weights that can be used to distinguish information. In combination with the non-orthogonal transmission characteristics of UDC, the channel capacity with a spectrum efficiency greater than 1 is realized, and the capacity limit of the traditional orthogonal transmission is broken through.

[0078] The non-orthogonal transmission device for the daytime strong turbulence and strong interference environment in the embodiment of the application does not need any mode demultiplexing device at the receiving end, directly detects the composite optical signal, fundamentally avoids the optical power loss caused by mode separation, improves the receiving sensitivity and power budget of the system, saves the expensive and precise mode demultiplexing device and subsequent multi-channel parallel receiving processing circuit, greatly simplifies the optical and hardware structure of the receiver, and reduces the system cost, volume and power consumption.

[0079] As shown in Figure 2 , the application provides a non-orthogonal transmission method for a daytime strong turbulence and strong interference environment, including the following steps:

[0080] S1, encoding M paths of to-be-transmitted information by using pre-defined, mutually different unique decodable UDC code word sets respectively, to obtain corresponding M code words.

[0081] , the M paths of to-be-transmitted information, indicate the mth path of to-be-transmitted information. Let the mth code word set be , correspondingly, the code word set contains code words. The code words in the code word set are of the same length, and are all L. Therefore, the are encoded by using mutually different unique decodable UDC code word sets, and the encoding result is . The M paths of to-be-transmitted information are 3 paths of to-be-transmitted information, each path of information is encoded in a pre-defined and uniquely bound unique decodable (UDC) code word set. m indicates 1 m any mth element in M; M indicates the number of modes applied.

[0082] The pre-defined three unique decodable UDC code word sets are one-to-one corresponding to three different linear polarization LP modes respectively, that is, the code word set , 、 respectively bound to three linear polarization modes of LP01, LP11a and LP11b.

[0083] The three pieces of information to be transmitted are encoded in their corresponding sets of code words, and finally three code words are obtained.

[0084] S2, the M code words are converted into M light signals after intensity modulation.

[0085] The three code words after encoding pass through intensity modulators and become three light signals, a total of three modes are applied, so three intensity modulators are needed, in order to ensure that the wavelengths after modulation are the same, the reference light of each intensity modulator needs to come from the same laser. In the embodiment of the application, a laser with a center wavelength of 1550nm is used as a light source. The light signal output by each modulator is physically shaped into a specific linear polarization LP mode bound to its code word set, thereby obtaining three mode light signals.

[0086] S3, the M light signals are combined into a composite light signal, which is transmitted through an atmospheric channel.

[0087] A three-mode photon lantern is used to combine the above-mentioned three different mode light signals, and coupled into a few-mode fiber to form a composite light signal containing multiple modes. The composite light signal can be represented as the superposition of each mode signal. Subsequently, the signal is amplified by a few-mode amplifier and transmitted into a daytime strong turbulent atmospheric channel in free space.

[0088] S4, receiving the transmission light signal of the composite light signal after transmission through the atmospheric channel, and photoelectrically converting the transmission light signal to obtain an electrical signal.

[0089] In the embodiment of the application, the optical path of the receiving end does not contain any mode demultiplexing device. The light signal is directly focused on a photodetector for photoelectric conversion to obtain a corresponding electrical signal.

[0090] In the daytime strong turbulent atmospheric channel, the intermodal crosstalk effect in the channel makes the received light signal show a weighted superposition signal of the three code words, that is, the turbulence effect causes serious intermodal crosstalk and atmospheric attenuation, which all affect the weighting coefficients. At any moment, the transmitting end light signal is an L-element vector, which can be regarded as the weighted superposition of each mode, and the weight is generated by the photon lantern combination and few-mode amplification.

[0091] The expression of the transmitting end light signal is:

[0092]

[0093] wherein, represents the weight row vector of each code word of the transmitting end, represents is the mth element in the matrix, i.e., the weight of the mth mode information. U is an M-row L-column matrix, representing all mode information of the transmitting end after UDC encoding at this moment, represents is the mth row element in the matrix, i.e., the code word transmitted by the mth mode.

[0094] After the composite optical signal passes through a strong turbulent atmosphere channel during the day, intermodal crosstalk and intensity fluctuation will be generated. Since the intensity modulator is used before transmission, the detector at the receiving end mainly responds to the change in light intensity, and the influence of wavefront distortion is reflected in the light intensity fluctuation and intermodal crosstalk.

[0095] The expression of the light signal intensity received by the receiving end after passing through a strong turbulent atmosphere channel is as follows:

[0096]

[0097] wherein, is an M-row M-column array, representing an intermodal crosstalk matrix, and the ith row jth column element represents the crosstalk coefficient between the ith mode and the jth mode at the receiving end after being affected by the turbulence. represents an attenuation vector, the elements in the matrix respectively represent the channel gains of the modes. represents multiplication of corresponding items. is an L-element vector, representing noise in the transmission process.

[0098] S4, receiving a transmission optical signal of the composite optical signal after the transmission through the atmosphere channel, and performing photoelectric conversion on the transmission optical signal to obtain an electrical signal.

[0099] The expression of the electrical signal collected after the transmission optical signal is photoelectrically converted and subjected to AD collection is as follows:

[0100]

[0101] wherein, represents a photoelectric conversion coefficient. As can be seen from the formula, the received information can still be written in the form of weighted code words Since and the elements thereof are positive numbers, it can be inferred that the weight values of each code word are positive.

[0102] S5, performing joint decoding in the code word domain on the collected electrical signal using a non-orthogonal weighted superposition relationship to recover the M pieces of information to be transmitted.​​

[0103] This invention provides a preferred embodiment, such as... Figure 3 As shown, joint decoding includes:

[0104] S501. Estimate the weight vector of intermodal crosstalk based on the training sequence.

[0105] Due to the quasi-static characteristics of atmospheric turbulence, the weight vector can be estimated. In the initial stage of establishing the communication link, the transmitter sends a known training sequence. The receiver, based on the received training sequence and the locally known sequence, uses algorithms from existing technologies such as minimum mean square error or least squares to estimate the equivalent weight vector under the current channel conditions.

[0106] The expression for the weight vector is:

[0107]

[0108]

[0109] in, Let be an M-element vector, representing the weight vector; This indicates an estimated correlation coefficient; Indicates an uncertain standard deviation; Let be an M-ary vector, representing a weighted estimate of the codewords. The elements in the equation represent the weighted estimates of the m-th codeword.

[0110] S502. Based on the weight vector, calculate the non-orthogonal weighted superposition result of all codewords, and construct a set of non-orthogonal weighted superposition codeword constellation points. . express The m-th element. The set of non-orthogonal weighted superposition codeword constellation points has a total of There are elements, and the elements are respectively . . This represents the number of elements in the set of codeword constellation points for non-orthogonal weighted superposition. For M=3, this represents the set of codeword constellation points for non-orthogonal weighted superposition. Total The superimposed pattern of each codeword corresponds to 8 different non-orthogonal weighted superimposed codeword constellation points. In this embodiment of the invention, the codeword set... , , The superposition coefficients are respectively , , The set of codeword constellation points, constructed using a non-orthogonal weighted superposition, is shown in Table 1:

[0111] Table 1 uniquely decodable code words and non-orthogonal weighted superimposed code word constellation points

[0112]

[0113] S503, according to the minimum Euclidean distance criterion, the corresponding non-orthogonal weighted superimposed code word constellation point is determined. First, according to the non-orthogonal weighted superimposed code word constellation point and the weight vector, M code words are inversely solved, specifically, according to the minimum Euclidean distance criterion, the most likely code word weighted superimposed non-orthogonal weighted superimposed code word constellation point is determined , according to the code word weighted superimposed non-orthogonal weighted superimposed code word constellation point and the estimation result of the weight vector The relationship , the code word of each mode is inversely solved .

[0114] S504, according to the determined code word , the code word and information mapping mode agreed with the transmitting end is used to determine the information to be transmitted . Indicates the information demodulated by the receiver. That is, according to the determination result, the three-way information to be transmitted is recovered by unique decodable inverse mapping.

[0115] As shown in Figure 4 , the collection result of the oscilloscope of the embodiment of the application, each non-orthogonal weighted superimposed code word constellation point is clear and distinguishable. It can be seen that the signal collected by the receiver oscilloscope has not been mode separated, and also does not need to be interference eliminated, but can use the non-orthogonal weighted superimposed code word constellation point to complete the data distinction of each mode, thereby avoiding the mode separation loss.

[0116] As shown in Figure 5 , the channel capacity curve of the embodiment of the application. After applying the unique decodable code, the non-orthogonal transmission characteristics are used to make the receiving end have a channel capacity greater than 1, which proves the effectiveness of the technical scheme of the embodiment of the application. In addition, since the sum rate of the code word set 、 、 of the applied unique decodable code is 1.5 bits / symbol. Therefore, at high signal-to-noise ratio, the channel capacity can reach the upper bound of the code word sum rate.

[0117] The technical scheme provided by the embodiment of the present application is different from the traditional mode division multiplexing laser communication method. The traditional mode division multiplexing laser communication method needs a mode separation step at the receiving end, and the data of each mode separated has crosstalk of other modes, and needs to be uniformly processed for interference cancellation and the like. The algorithm of the technical scheme provided by the embodiment of the present application makes the code words still distinguishable after weighted superposition by virtue of the non-orthogonal transmission characteristics of the unique decodable code word domain. Therefore, the technical scheme provided by the embodiment of the present application does not need mode separation at the receiving end, and does not need to perform interference cancellation.

[0118] Finally, it should be noted that: each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the method part.

[0119] The above embodiments are only used to illustrate the technical scheme of the present disclosure, but not limit it; although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical scheme recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the corresponding technical scheme deviate from the spirit and scope of the technical scheme of the embodiments of the present disclosure.

Claims

1. A non-orthogonal transmission method for a daytime strong turbulence and strong interference environment, characterized in that, The method comprises the following steps: M pieces of to-be-transmitted information are respectively encoded by using a set of predefined and mutually different unique decodable code (UDC) words to obtain corresponding M code words; The M code words are converted into M pieces of optical signals after intensity modulation; The M pieces of optical signals are mode-merged into a composite optical signal, which is transmitted through an atmospheric channel; A transmission optical signal is received after the composite optical signal is transmitted through the atmospheric channel, and the transmission optical signal is converted into an electrical signal through photoelectric conversion; After the electrical signal is sampled, joint decoding is performed in the code word domain by using a non-orthogonal weighted superposition relationship to recover the M pieces of to-be-transmitted information.

2. The non-orthogonal transmission method of claim 1, wherein, The joint decoding comprises: estimating a weight vector of inter-mode crosstalk according to a training sequence; calculating non-orthogonal weighted superposition results of all code words according to the weight vector to construct a set of non-orthogonal weighted superposition code word constellation points; judging corresponding non-orthogonal weighted superposition code word constellation points according to a minimum Euclidean distance criterion; recovering the M pieces of to-be-transmitted information through unique decodable inverse mapping according to the judgment result.

3. The non-orthogonal transmission method of claim 2, wherein, The judgment result is recovered into the M pieces of to-be-transmitted information through unique decodable inverse mapping, which comprises: the judgment result is corresponding non-orthogonal weighted superposition code word constellation points; M code words are inversely solved from the non-orthogonal weighted superposition code word constellation points and the weight vector; the M code words are recovered into the M pieces of to-be-transmitted information through unique decodable inverse mapping.

4. The non-orthogonal transmission method of claim 1, wherein, The M pieces of to-be-transmitted information are respectively encoded by using a set of predefined and mutually different unique decodable code (UDC) words to obtain corresponding M code words, which comprises: the set of M unique decodable UDC code words respectively correspond to M different linear polarization (LP) modes one by one; the M pieces of to-be-transmitted information are encoded in the corresponding code word set.

5. A non-orthogonal transmission apparatus for a daytime strong turbulence and strong interference environment, for implementing the non-orthogonal transmission method according to any one of claims 1 to 4, characterized in that, It comprises: a transmitting end and a receiving end; the transmitting end comprises: an encoder component comprising M encoders, which are respectively used for encoding M pieces of to-be-transmitted information in a corresponding set of unique decodable code (UDC) words to obtain M code words; an intensity modulator component comprising M intensity modulators, which are respectively connected to the M encoders and are used for converting the M code words into M pieces of optical signals; a mode merger, which is used for mode-merging the M pieces of optical signals into a composite optical signal; a transmitting unit, which is used for transmitting the composite optical signal through an atmospheric channel; the receiving end comprises: a detector, which is used for receiving a transmission optical signal after the composite optical signal is transmitted through the atmospheric channel and converting the transmission optical signal into an electrical signal; a joint decoder, which is used for recovering the M pieces of to-be-transmitted information by performing joint decoding in the code word domain after the electrical signal is sampled by using a non-orthogonal weighted superposition relationship.

6. The non-orthogonal transmission apparatus of claim 5, wherein, The joint decoder comprises: a weight estimation module, which is used for estimating a weight vector of inter-mode crosstalk according to a training sequence; a non-orthogonal weighted superposition code word constellation point construction module, which is used for calculating non-orthogonal weighted superposition results of all code words according to the weight vector to construct a set of non-orthogonal weighted superposition code word constellation points; A decision module is configured to determine the code word constellation point of the corresponding non-orthogonal weighted superposition according to the minimum Euclidean distance criterion; An inverse mapping module is configured to recover the M pieces of to-be-transmitted information through unique decodable inverse mapping according to the determination result.

7. The non-orthogonal transmission apparatus of claim 6, wherein, The inverse mapping module comprises: An inverse solution unit is configured to inversely solve M code words from the code word constellation point of the non-orthogonal weighted superposition and the weight vector; A decoding unit is configured to recover the M pieces of to-be-transmitted information through unique decodable inverse mapping from the M code words.

8. The non-orthogonal transmission apparatus of claim 5, wherein, Each of the M encoders is bound to one of M different linear polarization (LP) modes one by one, and performs encoding in a bound unique decodable code (UDC) code word set.

9. The non-orthogonal transmission apparatus of claim 8, wherein, The mode combiner is a photonic lantern, configured to couple M linear polarization (LP) modes of the M pieces of optical signals into at least a multi-mode optical fiber.

10. The non-orthogonal transmission apparatus of claim 9, wherein, The transmitting unit comprises a few-mode optical amplifier, which is arranged between the mode combiner and the atmospheric channel, and is configured to perform power amplification on the composite optical signal and then send the composite optical signal into the atmospheric channel.

Images