Error rate evaluation method for optical communication system adopting photon-level energy receiver under periodic pulse interference

Abstract

The invention belongs to the technical field of optical communication system error rate evaluation. The invention provides a method for evaluating the error rate of an optical communication system adopting a photon-level energy receiver under periodic pulse interference. The method comprises the following steps: obtaining a probability density function of an interference signal according to a duty ratio, a periodic coefficient and an asynchronous time difference coefficient of the interference signal, and obtaining a value of the interference signal and a corresponding probability; determining a modulation mode, and determining a value of a legal signal; according to the value of the legal signal, the value of the interference signal and the corresponding probability, the average output photon number of the light receiving end in the time slot of the legal signal is obtained; and obtaining the average bit error rate of the light receiving end according to the average output photon number of the light receiving end in the legal signal time slot. According to the embodiment of the invention, the periodic coefficient is the integer or the reciprocal is the integer, the actual situation can be approximated, and a better error rate evaluation effect can be obtained. No matter whether the interference signal and the legal signal are synchronous or not, the error rate of the system in the presence of interference can be evaluated.

Description

Technical Field

[0001] The disclosed embodiments relate to the technical field of bit error rate evaluation of optical communication systems, and in particular to a method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference. Background Art

[0002] When the optical communication system is working, there may be potential illegal users around who want to interfere with the legal receiver and block the communication link. The optical communication system here is not limited to wired optical communication (including optical fiber communication) and wireless optical communication (such as free space optical communication, visible light communication, ultraviolet light communication, underwater optical communication, etc.). At this time, the research scenario can be expressed as Figure 1 .

[0003] At this time, the optical interference end (J) randomly sends a periodic pulse signal to interfere with the optical receiving end (R), hoping to block the link from the optical transmitting end (T) to the optical receiving end (R). In this case, this application proposes a bit error rate evaluation method to lay the foundation for the subsequent design of anti-interference methods.

[0004] Assume that the pulse sent by the optical interference end has a duty cycle of The methods used in existing literature all assume that the probability of an interference signal in a signal time slot at the optical receiving end is , the probability of no interference signal is . However, there are two ideal situations implied here: 1. The interference pulse and the legitimate signal are synchronized, that is, the starting point of the interference pulse is consistent with the starting point of the legitimate signal; 2. The duration of the pulse in the interference pulse is an integer multiple of the symbol period of the legitimate signal. In actual situations, the assumptions based on the bit error rate evaluation method in the presence of pulse interference are too harsh, because the conflict of interests between the interfering user and the legitimate user makes it difficult to meet the above two assumptions. Therefore, the bit error rate of the system evaluated by this method in the presence of interference is quite different from the actual situation.

[0005] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0006] It should be noted that this section is intended to provide background or context for the technical solutions of the present disclosure stated in the claims. The description herein is not admitted to be prior art by virtue of being included in this section. Summary of the invention

[0007] The purpose of the embodiments of the present disclosure is to provide a method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference, thereby overcoming one or more problems caused by the limitations and defects of related technologies at least to a certain extent.

[0008] According to an embodiment of the present disclosure, a method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference is provided, the method comprising: According to the duty cycle, period coefficient and asynchronous time difference coefficient of the interference signal, a probability density function of the interference signal is obtained, and according to the probability density function of the interference signal, a value of the interference signal and its corresponding probability are obtained; Determine the modulation method and determine the value of the legal signal; According to the value of the legal signal, the value of the interference signal and their corresponding probabilities, the average number of photons output by the optical receiving end in the legal signal time slot is obtained; According to the average number of photons output by the optical receiving end in the legal signal time slot, the average bit error rate of the optical receiving end is obtained.

[0009] Further, the step of obtaining the probability density function of the interference signal according to the duty cycle, period coefficient and asynchronous time difference coefficient of the interference signal includes: When the period coefficient hour, like ,but:

[0010] like ,and ,but:

[0011] like ,and ,but:

[0012] When the period coefficient hour,

[0013] in, is the probability density function of the interference signal, is the value of the interference signal, is the periodic coefficient, is the asynchronous time difference coefficient, is the duty cycle of the interference signal, Indicates the maximum integer. It means to take the smallest integer. Indicates taking the integer part.

[0014] Furthermore, the steps of determining the modulation mode and determining the value of the legal signal include: Determine a modulation mode; wherein the modulation mode includes at least on-off keying modulation, pulse position modulation and quaternary pulse amplitude modulation; If the modulation mode is on-off keying modulation and pulse position modulation, the value of the legal signal is 0 or 1; If the modulation mode is quaternary pulse amplitude modulation, the value of the legal signal is 0, , or 1.

[0015] Further, the step of obtaining the average number of photons output by the optical receiving end in the legitimate signal time slot according to the value of the legitimate signal, the value of the interference signal and their corresponding probabilities includes: Based on the value of the legitimate signal, the value of the interference signal and their corresponding probabilities, combined with the coefficient of the TR link, the coefficient of the JR link, the peak optical power of the optical transmitter, the peak optical power of the optical interference end and the average number of background photons in the legitimate signal time slot, the average output photon number of the optical receiving end in the legitimate signal time slot is obtained; among which, the JR link is the link from the optical interference end J to the optical receiving end R, and the TR link is the link from the optical transmitter T to the optical receiving end R.

[0016] Furthermore, the expression for the average number of photons output by the optical receiving end in the legal signal time slot is:

[0017] in, is the coefficient of the TR link, is the coefficient of the JR link, and , , is the link gain of the TR link, is the link gain of the JR link, is the energy of a photon, To set the time slot of the legal signal, is Planck's constant, is the light frequency, is the peak optical power at the optical transmitter, is the peak optical power at the optical interference end, is the average number of background photons in the legal signal time slot.

[0018] Further, the step of obtaining the average bit error rate of the optical receiving end according to the average number of photons output by the optical receiving end in the legal signal time slot includes: According to the relationship between the average number of photons output by the optical receiving end in the legal signal time slot and the actual number of photons received by the optical receiving end, the probability density function and the cumulative distribution function are obtained; According to the probability density function, the cumulative distribution function and the value of the legal signal, the conditional bit error rate of the optical receiving end is obtained; According to the conditional bit error rate of the optical receiving end, the average bit error rate of the optical receiving end is obtained.

[0019] Furthermore, the expression of the probability density function is:

[0020] in, The actual number of photons received by the optical receiving end; The expression of the cumulative distribution function is:

[0021] in, is the summation coefficient; The expression of the average bit error rate of the optical receiver is:

[0022] in, is the conditional bit error rate at the optical receiver, is the probability density function of the asynchronous time difference coefficient.

[0023] The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects: In the embodiment of the present disclosure, the bit error rate evaluation method of the optical communication system using the photon-level energy receiver under the periodic pulse interference is used. On the one hand, compared with the existing scheme Based on The probability density function of . This method innovatively introduces an approximate method in which the periodic coefficient is an integer or its reciprocal is an integer, so as to be closer to the actual scenario. Through this method, we can obtain a more accurate bit error rate related probability density function, thereby significantly improving the accuracy and reliability of bit error rate evaluation. On the other hand, this method also deeply considers the antagonistic relationship between interfering users and legitimate users, and pays special attention to the asynchronous scenarios that may exist between interfering signals and legitimate signals. In view of this complex situation, the proposed The probability density function of can fully reflect the impact of the asynchronous time difference coefficient on the system bit error rate. This feature enables this method to more accurately evaluate the system bit error rate in a complex interference environment, providing strong support for system design and performance optimization. The relevant content of this method provides an important theoretical basis and practical guidance for the design of optical communication systems in the presence of interference, especially systems using photon-level energy receivers, and the establishment of interference suppression methods. This will help promote the further development of optical communication technology and enhance the anti-interference ability and overall performance of communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0025] Figure 1 A schematic diagram of an optical communication system in an exemplary embodiment of the present disclosure is shown; Figure 2 A step diagram showing a method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference in an exemplary embodiment of the present disclosure; Figure 3 A schematic diagram showing the relationship between an interference signal and a legitimate signal in an exemplary embodiment of the present disclosure; Figure 4 The bit error rate of the ultraviolet light communication system in the exemplary embodiment of the present disclosure when interference exists is shown. DETAILED DESCRIPTION

[0026] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0027] In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0028] This example embodiment provides a method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference. Figure 2 As shown in , the method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference may include: steps S101 to S104.

[0029] Step S101: obtaining a probability density function of the interference signal according to the duty cycle, period coefficient and asynchronous time difference coefficient of the interference signal, and obtaining a value of the interference signal and its corresponding probability according to the probability density function of the interference signal; Step S102: Determine the modulation mode and the value of the legal signal; Step S103: according to the value of the legitimate signal, the value of the interference signal and their corresponding probabilities, the average number of photons output by the optical receiving end in the legitimate signal time slot is obtained; Step S104: according to the average number of photons output by the optical receiving end in the legal signal time slot, the average bit error rate of the optical receiving end is obtained.

[0030] Through the above-mentioned periodic pulse interference optical communication system bit error rate evaluation method using photon-level energy receiver, on the one hand, compared with the existing scheme Based on The probability density function of . This method innovatively introduces an approximate method in which the periodic coefficient is an integer or its reciprocal is an integer, so as to be closer to the actual scenario. Through this method, we can obtain a more accurate bit error rate related probability density function, thereby significantly improving the accuracy and reliability of bit error rate evaluation. On the other hand, this method also deeply considers the antagonistic relationship between interfering users and legitimate users, and pays special attention to the asynchronous scenarios that may exist between interfering signals and legitimate signals. In view of this complex situation, the proposed The probability density function of can fully reflect the impact of the asynchronous time difference coefficient on the system bit error rate. This feature enables this method to more accurately evaluate the system bit error rate in a complex interference environment, providing strong support for system design and performance optimization. The relevant content of this method provides an important theoretical basis and practical guidance for the design of optical communication systems in the presence of interference, especially systems using photon-level energy receivers, and the establishment of interference suppression methods. This will help promote the further development of optical communication technology and enhance the anti-interference ability and overall performance of communication systems.

[0031] Next, we will refer to Figures 1 to 4 The various steps of the method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under the above-mentioned periodic pulse interference in this example implementation are described in more detail.

[0032] In step S101 to step S103, the optical communication system includes an optical transmitting end and an optical receiving end, such as Figure 1 The communication link between the two is a TR link, and the signal sent is a legal signal, such as Figure 3 As shown, pulse modulation is adopted, including but not limited to on-off keying (OOK) modulation, pulse position modulation (PPM) modulation, etc. Assume that the time slot of the legal signal is The optical interference end sends periodic pulses to interfere with legitimate users. The duty cycle of the interference signal is , the period of an interference pulse is ,in Since the interference pulse transmission time is random, the time difference between the time when the optical receiving end receives the interference signal and the start of the current legal signal time slot is ,in Here we assume is an integer or its reciprocal is an integer. That is, the period of the interference pulse is an integer multiple of the legitimate signal time slot, or the legitimate signal time slot is an integer multiple of the interference pulse period. At this time, this method can accurately evaluate the bit error rate of the system when the above assumptions are true, and can also be used for situations that do not meet the above assumptions. or its reciprocal. For example, When or Approximate calculation, , then take or Approximate calculation.

[0033] Since the receiving end uses a receiving end photon-level energy receiver, the signal output by the receiving end in the legal signal time slot is the number of photons arriving in the time slot (for example, using a photon counting receiver) or the sum of random electrical signals generated by photons (for example, using a photomultiplier tube (PMT), avalanche diode (APD), etc.). Therefore, the focus is essentially on determining the number of photons arriving in the legal signal time slot. For ease of expression, this application uses a photon counting receiver as a demonstration. Signal output models using receivers such as photomultiplier tubes (PMTs) and avalanche diodes (APDs) are also available, and the methods are similar, so they will not be described in detail here.

[0034] At this time, the average number of photons output by the optical receiving end in the legal signal time slot is: (1) in and denote the coefficients of TR link and JR link respectively. , , and are the link gains of the TR link and the JR link, including factors such as path loss, transmitting antenna gain, receiving antenna gain, and detector quantum efficiency. is the energy of a photon, is Planck's constant, is the light frequency. It is the peak optical power at the optical transmitter, which is determined by the characteristics of the light source at the optical transmitter. It is the peak optical power at the optical interference end, which is determined by the light source characteristics of the optical interference section. It is the optical signal value sent by the optical transmitter in the legal time slot. The specific value of depends on the modulation method used and the information sent, such as OOK and PPM. Can be 0 or 1; for quaternary pulse amplitude modulation (4-PAM), Can be 0, , , 1. However, the present application is not limited to the above modulation methods. is the average number of background photons in the legal signal time slot. It is determined by how long the high level of the interference pulse affects the legal time slot.

[0035] This application gives The probability density function of as follows: 1. When hour: 1.1 If , then (2) 1.2 If , then 1.2.1 If

[0036] (3) 1.2.2 If

[0037] (4) 2. When hour (5) in, Indicates less than The largest integer, Indicates greater than The smallest integer of Indicates taking The integer part of the probability density function The form of can be transformed into other forms through mathematical transformation, but it does not change the final calculation result. This application will not list them one by one.

[0038] Then, the actual number of photons received by the optical receiver is Obey is a Poisson distribution with the mean as follows: (6) In step S104, OOK modulation is taken as an example to illustrate how to calculate the average bit error rate. The methods for calculating the average bit error rate of other modulation modes are all existing technologies and will not be described in detail here.

[0039] when hour, , It is defined as; when hour, Then, the conditional bit error rate at the optical receiving end is: (7) in, It is the decision threshold, which is determined by the optical receiver and is related to the optical receiver's ability to detect interference signals. , indicating that the optical receiver can detect the average power of the interfering optical signal through accumulation over a period of time. The setting is not unique. Its setting only affects the calculation results but does not affect the implementation of this patent. Expressed in natural logarithm. Cumulative distribution function representing the Poisson distribution: (8) Considering that the jammer will shut down after a period of time and then turn on again to protect itself, is also a random variable, assuming its distribution is Then, the average bit error rate at the optical receiving end is: (9) The calculation result of formula (9) can be obtained by existing numerical integration methods, including but not limited to numerical integration formulas such as the rectangle method, Newton's method, and Gaussian method.

[0040] In a specific embodiment, taking the ultraviolet light communication system as an example, setting , each curve is guaranteed to be compared under the same conditions, and the calculation results are as follows Figure 4 The “existing approximate method” assumes that the probability of an interference signal in a signal time slot at the optical receiving end is , the probability of no interference signal is It can be seen that when When increases, the existing approximate methods can achieve good results. When is small, the existing approximation method is quite different from the simulation results.

[0041] The method proposed by the present invention can accurately calculate is an integer or When the reciprocal of is an integer, Figure 3 The theoretical and simulation results are consistent, which verifies the effectiveness of the theoretical method proposed in this invention. Not an integer or The reciprocal of is not an integer, for example Figure 3 middle or , we can take the integer part to approximate the calculation, for example, Approximate calculation The BER results of , the difference between the two is better than that of the existing approximate methods. When the simulation is The BER is about , the BER of the existing approximate method is The result of the present invention is For example, Approximate calculation The BER results of , the difference between the two is better than that of the existing approximate methods. When the simulation is The BER is almost the same as the result of the present invention, which is about , the BER of the existing approximate method is .

[0042] Through the above-mentioned periodic pulse interference optical communication system bit error rate evaluation method using photon-level energy receiver, on the one hand, compared with the existing scheme Based on The probability density function of . This method innovatively introduces an approximate method in which the periodic coefficient is an integer or its reciprocal is an integer, so as to be closer to the actual scenario. Through this method, we can obtain a more accurate bit error rate related probability density function, thereby significantly improving the accuracy and reliability of bit error rate evaluation. On the other hand, this method also deeply considers the antagonistic relationship between interfering users and legitimate users, and pays special attention to the asynchronous scenarios that may exist between interfering signals and legitimate signals. In view of this complex situation, the proposed The probability density function of can fully reflect the impact of the asynchronous time difference coefficient on the system bit error rate. This feature enables this method to more accurately evaluate the system bit error rate in a complex interference environment, providing strong support for system design and performance optimization. The relevant content of this method provides an important theoretical basis and practical guidance for the design of optical communication systems in the presence of interference, especially systems using photon-level energy receivers, and the establishment of interference suppression methods. This will help promote the further development of optical communication technology and enhance the anti-interference ability and overall performance of communication systems.

[0043] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. in the above description indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present disclosure.

[0044] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0045] In the embodiments of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0046] In the embodiments of the present disclosure, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0048] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference, characterized in that: The method includes: According to the duty cycle, period coefficient and asynchronous time difference coefficient of the interference signal, a probability density function of the interference signal is obtained, and according to the probability density function of the interference signal, a value of the interference signal and its corresponding probability are obtained; Determine the modulation method and determine the value of the legal signal; According to the value of the legal signal, the value of the interference signal and their corresponding probabilities, the average number of photons output by the optical receiving end in the legal signal time slot is obtained; According to the average number of photons output by the optical receiving end in the legal signal time slot, the average bit error rate of the optical receiving end is obtained.

2. The method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference according to claim 1 is characterized in that: The step of obtaining a probability density function of the interference signal according to the duty cycle, period coefficient and asynchronous time difference coefficient of the interference signal comprises: When the period coefficient hour, like ,but: like ,and ,but: like ,and ,but: When the period coefficient hour, in, is the probability density function of the interference signal, is the value of the interference signal, is the periodic coefficient, is the asynchronous time difference coefficient, is the duty cycle of the interference signal, Indicates the maximum integer. It means to take the smallest integer. Indicates taking the integer part.

3. The method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference according to claim 2 is characterized in that: The steps of determining the modulation mode and determining the value of the legal signal include: Determine a modulation mode; wherein the modulation mode includes at least on-off keying modulation, pulse position modulation and quaternary pulse amplitude modulation; If the modulation mode is on-off keying modulation and pulse position modulation, the value of the legal signal is 0 or 1; If the modulation mode is quaternary pulse amplitude modulation, the value of the legal signal is 0, , or 1.

4. The method for evaluating bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference according to claim 3 is characterized in that: The step of obtaining the average number of photons output by the optical receiving end in the legitimate signal time slot according to the value of the legitimate signal, the value of the interference signal and the corresponding probabilities thereof comprises: Based on the value of the legitimate signal, the value of the interference signal and their corresponding probabilities, combined with the coefficient of the TR link, the coefficient of the JR link, the peak optical power of the optical transmitter, the peak optical power of the optical interference end and the average number of background photons in the legitimate signal time slot, the average output photon number of the optical receiving end in the legitimate signal time slot is obtained; among which, the JR link is the link from the optical interference end J to the optical receiving end R, and the TR link is the link from the optical transmitter T to the optical receiving end R.

5. The method for evaluating the bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference according to claim 4 is characterized in that: The expression of the average number of photons output by the optical receiving end in the legal signal time slot is: in, is the coefficient of the TR link, is the coefficient of the JR link, and , , is the link gain of the TR link, is the link gain of the JR link, is the energy of a photon, To set the time slot of the legal signal, is Planck's constant, is the light frequency, is the peak optical power at the optical transmitter, is the peak optical power at the optical interference end, is the average number of background photons in the legal signal time slot.

6. The method for evaluating bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference according to claim 5, characterized in that: The step of obtaining an average bit error rate of the optical receiving end according to the average number of photons output by the optical receiving end in the legal signal time slot includes: According to the relationship between the average number of photons output by the optical receiving end in the legal signal time slot and the actual number of photons received by the optical receiving end, the probability density function and the cumulative distribution function are obtained; According to the probability density function, the cumulative distribution function and the value of the legal signal, the conditional bit error rate of the optical receiving end is obtained; According to the conditional bit error rate of the optical receiving end, the average bit error rate of the optical receiving end is obtained.

7. The method for evaluating bit error rate of an optical communication system using a photon-level energy receiver under periodic pulse interference according to claim 6, characterized in that: The expression of the probability density function is: in, The actual number of photons received by the optical receiving end; The expression of the cumulative distribution function is: in, is the summation coefficient; The expression of the average bit error rate of the optical receiver is: in, is the conditional bit error rate at the optical receiver, is the probability density function of the asynchronous time difference coefficient.

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