A method for locating faults in optical fiber communication links

Abstract

The present invention proposes a fault locating method for an optical fiber communication link, which relates to the technical field of optical fiber communication. The method comprises the following steps: transmitting the same detection pulse signal to each branch of the optical fiber communication link; installing a reflector with different coding modes at the end of each branch of the optical fiber communication link to encode the detection pulse signal transmitted to the reflector and reflect the coded detection pulse signal; processing and analyzing the coded detection pulse signal reflected back from each branch, and calculating the total coded pulse and photocurrent density; establishing a link fault judgment model based on the photocurrent density, calculating the failure probability of the optical fiber communication link, and judging the occurrence of a fault when the failure probability exceeds a threshold; and when it is judged that a fault has occurred, locating the fault of the branch where the reflector that has not received the detection pulse signal is located, and feeding back the fault position to the system, thereby improving the accuracy of fault judgment of the optical fiber communication link, reducing the cost of misjudgment, and improving maintenance efficiency.

Description

Technical Field

[0001] The invention provides a method for locating a fault of an optical fiber communication link, and relates to the technical field of optical fiber communications. Background Art

[0002] Since its advent in the 1970s, fiber-optic communication technology has experienced rapid development and has become a mainstay of global communications networks. With its advantages of high speed, large capacity, low loss, and resistance to electromagnetic interference, fiber-optic communication technology has been widely used in telecom operator networks, data center interconnection, 5G, and future 6G networks. As the demand for data transmission continues to grow, fiber-optic communication technology continues to innovate, with transmission rates increasing from a few megabits per second (Mbps) to tens of terabits per second (Tbps), significantly advancing the communications industry.

[0003] Despite the many advantages of fiber-optic communication technology, failures are still difficult to avoid in practical applications. Fiber-optic communication failures can lead to signal interruptions, data loss, communication delays, and other problems, seriously affecting the normal operation of the communication network and user experience. Therefore, in-depth research on fiber-optic communication failures and the development of effective fault location and repair optimization technologies are of great significance for improving the stability and reliability of communication networks. However, existing methods for locating faults in fiber-optic communication links have some shortcomings, mainly including the following aspects:

[0004] Cost and equipment requirements: Some fault location techniques, such as OTDR (Optical Time Domain Reflectometer), may require expensive specialized equipment, which increases the cost of maintenance and fault location.

[0005] Operational complexity: Some fault location methods may require professional personnel to perform operations and data analysis, which limits the speed and convenience of fault location.

[0006] Blind spots and limitations: OTDR technology has blind spots near both ends of the fiber link, which makes it difficult to locate faults at the beginning and end of the fiber link.

[0007] Data processing complexity: The detection pulse signal transmitted in the optical fiber link may be affected by various factors during the reflection process, such as the nonlinear effect of the optical fiber and signal attenuation, which increases the complexity of data processing.

[0008] Fault type identification: Some fault location technologies may have difficulty distinguishing between different types of faults, such as fiber breaks, connector issues, or fiber bends.

[0009] Fault location accuracy: In some cases, the accuracy of fault location may not be sufficient to quickly find the fault point, especially when the fiber link is too long or the terrain is complex. Summary of the Invention

[0010] In order to solve the above technical problems, the present invention proposes a method for locating a fault in an optical fiber communication link, comprising the following steps:

[0011] S1. Transmitting the same detection pulse signal to each branch of the optical fiber communication link. Installing a reflector with a different encoding mode at the end of each branch of the optical fiber communication link to encode the detection pulse signal transmitted to the reflector and reflect the encoded detection pulse signal.

[0012] S2. Process and analyze the coded detection pulse signals reflected from each branch, and calculate the total coded pulse and photocurrent density;

[0013] S3. Based on the photocurrent density, a link fault judgment model is established to calculate the failure probability of the optical fiber communication link. When the failure probability exceeds the threshold, it is determined that a fault has occurred.

[0014] S4. When it is determined that a fault has occurred, the fault is located on the branch where the reflector that has not received the detection pulse signal is located, and the fault position is fed back to the system.

[0015] Furthermore, in step S2, the total coded pulse E(t,λ) received at time t is expressed as:

[0016]

[0017] Where λ is the initial wavelength of the detection pulse signal, A is the initial amplitude of the detection pulse signal, and a e is the insertion loss of the reflector, exp(-α e ) represents the amplitude attenuation after passing through the i-th reflector, λ i is the central wavelength of the i-th reflected coded detection pulse signal, τ i is the time delay, δ(λ-λ i ) is the Dirichlet function, p(t-τ i ) is the pulse shape function.

[0018] Furthermore, the photocurrent i at time t PD (t) is expressed as:

[0019] i PD (t)=G|E(t,λ)| 2 +i n (t)

[0020] Where |E(t,λ)| 2 is the power of the total coded pulse signal, i n (t) is the noise current;

[0021] The photocurrent density γ is expressed as:

[0022]

[0023] Among them, the detection period is T c .

[0024] Furthermore, when a fiber optic communication link fails, the expected value is a and the variance is σ a , when the link is normal, the expectation is b and the variance is σ b , then P D is the probability of correctly detecting a failure in an optical fiber communication link, P FA is the false alarm probability when the optical fiber communication link is normal, and the expression is as follows:

[0025]

[0026] Among them, μ is the threshold current of the judgment comparator.

[0027] Furthermore, the link failure judgment model for judging the failure probability is defined as:

[0028]

[0029] When the failure probability P ODP When the threshold is exceeded, it is determined that a fault has occurred.

[0030] Furthermore, suppose that the initial fault wave surge propagates from the fault point F along the line to the detection points at both ends of MN at the same wave speed v and the time when it reaches the detection points at both ends of M and N is T respectively. M 、T N , then the distance L from the M end and the N end to the fault point F is obtained MF and L NF for:

[0031]

[0032] Wherein, L is the length between the M end and the N end.

[0033] Furthermore, in step S1, the reflector is a fiber Bragg grating reflector, and the number of Bragg gratings in each reflector is equal to the code weight of the codeword.

[0034] Compared with the prior art, the present invention has the following beneficial technical effects:

[0035] Improve fault location accuracy: Based on photocurrent density, a link fault judgment model is established to calculate the failure probability of the optical fiber communication link. When the failure probability exceeds the threshold, the fault is judged to have occurred. The accuracy of fault judgment is the highest, which helps to reduce false alarms.

[0036] The coded detection pulse signals reflected from each branch are processed and analyzed, and the total coded pulse and photocurrent density are calculated to provide corresponding data for fault judgment, increase data processing efficiency, and reduce the impact of interference on fault judgment. This helps to reduce the time and computing resources required for data processing and improve the response speed and efficiency of the entire verification system.

[0037] Improve user experience: Because this method can quickly and accurately locate faults in optical fiber communication links, the alarm is timely and accurate, which improves maintenance efficiency, reduces the cost of troubleshooting false alarms, and further improves communication user satisfaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 Schematic diagram of the process of locating a fault in an optical fiber communication link according to the present invention;

[0040] Figure 2 Schematic diagram of Bragg grating reflector;

[0041] Figure 3 This is a schematic diagram of the distance between the fault point and the detection points at both ends of the line according to the present invention. DETAILED DESCRIPTION

[0042] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0043] In the drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of the various components in the system, the connection relationship of the various parts in the device is shown, which only clearly distinguishes the relative position relationship between the various components, and does not constitute a limitation on the signal transmission direction, connection sequence and structural size, size and shape of each part within the component or structure.

[0044] like Figure 1 FIG. 1 is a flow chart of a method for locating a fault in an optical fiber communication link according to the present invention. The method for locating a fault in an optical fiber communication link comprises the following steps:

[0045] S1. The same detection pulse signal is transmitted to each branch of the optical fiber communication link. A reflector with different encoding methods is installed at the end of each branch of the optical fiber communication link to encode the detection pulse signal transmitted to the reflector and reflect the encoded detection pulse signal.

[0046] Specifically, it is necessary to send a detection pulse signal with the same characteristics (such as power, wavelength, and pulse width) to each branch of the optical fiber communication link.

[0047] A reflector with a unique coding method is installed at the end of each optical fiber communication link branch. When the detection pulse signal reaches the end of the optical fiber, it will be encoded by the reflector and reflected back.

[0048] Preferably, the reflectors are fiber Bragg grating (FBG) reflectors, which reflect specific wavelengths of light, such as probe light, while allowing other wavelengths, such as normal communication signals, to pass through. When the probe pulse reaches the end of the optical fiber, it is encoded by these reflectors and reflected back, enabling real-time monitoring of the optical fiber link.

[0049] like Figure 2 The figure shows a schematic diagram of a Bragg grating reflector. The wavelength at which the incident light is reflected is called the Bragg wavelength. Optical signals of other wavelengths are hardly affected by the Bragg grating and continue to be transmitted through the fiber Bragg grating.

[0050] In a preferred embodiment, the reflected coded detection pulse signal can be optically amplified and the power loss of the coded detection pulse signal in the optical fiber link can be compensated. After the photoelectric conversion is performed through the optical detector, information such as the pulse amplitude and wavelength of the received coded detection pulse signal can be extracted simultaneously, so as to carry out the next step of data analysis and calculation.

[0051] S2. Process and analyze the coded detection pulse signals reflected from each branch, calculate the total coded pulse and photocurrent density, and provide corresponding data for fault diagnosis.

[0052] The detection pulse signal passes through the trunk input optical fiber, enters the distribution optical fiber of each branch, and reaches the reflector with a unique coding method at the corresponding end of each branch for encoding. The encoded detection pulse signal is reflected back to the receiving end of the trunk.

[0053] Specifically, there are w reflected coded detection pulse signals, each coded detection pulse signal has a different wavelength and time delay, then the total coded pulse received by the receiving end of the trunk can be expressed as the superposition of multiple reflected coded detection pulse signals.

[0054] The total coded pulse E(t,λ) received at time t is expressed as:

[0055]

[0056] Where λ is the initial wavelength of the detection pulse signal, A is the initial amplitude of the detection pulse signal, and a e is the insertion loss of the reflector, which is a parameter that describes the power reduction of the detection pulse signal when it passes through the reflector. It is related to the material and design of the reflector and the wavelength of the detection pulse signal; exp(-α e ) represents the amplitude attenuation after passing through the i-th reflector, λ i is the central wavelength of the i-th reflected coded detection pulse signal, τ i is the time delay, δ(λ-λ i ) is the Dirichlet function, which is used to ensure that only the wavelength components matching the central wavelength of the i-th reflector are considered; P(t-τ i ) is the pulse shape function, which represents the pulse shape at time t.

[0057] It's important to explain that the number of Bragg gratings in each reflector is equal to the code weight of the codeword. These two parameters are key. The number of Bragg gratings determines the number of unique wavelengths that can be encoded, while the code weight of the codeword affects system capacity and performance. Code weight refers to the number of non-zero elements in the codeword, which is directly related to the system's user capacity and multi-user interference management. For example, in an OCDMA system, a higher code weight allows the system to support more users, but it may also increase multi-user interference.

[0058] When a branch distribution fiber fails, no coded detection pulse signal is returned. When other branch distribution fibers are working normally, the detection pulse signal transmitted in the fiber link is encoded and reflected back to the receiving end for decoding and analysis.

[0059] The decoded total coded pulse signal is converted into an electrical signal by a photodetector with a gain of G, and the photocurrent i at time t PD (t) can be expressed as:

[0060] i PD (t)=G|E(t,λ)| 2 +i n (t)

[0061] Where |E(t,λ)| 2 is the power of the total coded pulse signal, i n (t) is the noise current. Assuming that the polarization effect is ignored, all light pulse currents detected by the photodetector have consistent and independent statistics, so the noise terms can be linearly superimposed.

[0062] In order to evaluate the status of the optical fiber link, the detection period is T c The current signal of the photodetector is filtered and sampled within the observation window interval to calculate the photocurrent density.

[0063] The photocurrent density γ can be expressed as:

[0064]

[0065] S3. Based on the photocurrent density, a link fault judgment model is established to calculate the failure probability of the optical fiber communication link. When the failure probability exceeds the threshold, it is determined that a fault has occurred.

[0066] The probability of correctly reporting a fiber optic communication link failure and the probability of incorrectly reporting a fiber optic communication link failure are both very important in detecting failures, and the two probabilities are inherently related.

[0067] Define P D is the probability of correctly detecting a fault in the optical fiber communication link, μ is the threshold current of the judgment comparator; P FA is the false alarm probability when the optical fiber communication link is normal.

[0068] Assume that the photocurrent density γ obeys the Gaussian distribution of expectation and variance. When the optical fiber communication link fails, the expectation is a and the variance is σ a , when the link is normal, the expectation is b and the variance is σ b , then the expression is as follows:

[0069]

[0070] Among them, μ is the threshold current of the judgment comparator.

[0071] In an ideal detection system, P D The larger the value, the greater the FA As small as possible can achieve the desired result. The link fault judgment model for judging the failure probability can be defined as follows:

[0072]

[0073] When the failure probability P ODP When the threshold is exceeded, it is judged that a fault has occurred, and the resulting fault judgment is the most accurate, which can reduce false alarms or missed alarms of fault points, reduce operating costs, and improve user satisfaction.

[0074] S4. Based on the result of the fault probability determination in step S3, the fault is located on the branch where the reflector that has not received the detection pulse signal is located, and the fault location is fed back to the system.

[0075] like Figure 3 As shown, the absolute time difference between the initial wave surge generated at the fault location in the optical fiber communication link and the detection points at both ends of the line is used to calculate the distance between the fault point and the detection points at both ends of the line.

[0076] Specifically, in a fiber optic communication link, when a fault occurs, the initial wave surge generated by the fault point will propagate at a certain speed to the detection points at both ends of the line. By calculating the absolute time difference between the two detection points receiving the wave surge, the distance between the fault point and the detection points at both ends of the line can be inferred.

[0077] Assume that the initial fault wave surge propagates from the fault point F along the line to the detection points at both ends of MN at the same wave speed and the time when it reaches the detection points at both ends of M and N is T respectively. M 、T N . According to the line relationship, it can be expressed as follows:

[0078]

[0079] Among them, L MF is the distance from the detection point at end M to the fault point F, L NF is the distance from the detection point at the N end to the fault point F. L is the length between the lines MN, and v is the wave speed.

[0080] The distance from the M and N terminals to the fault point F can be calculated using the above formula:

[0081]

[0082] Finally, the fault location is fed back to the system.

[0083] This distance measurement method is not affected by other impedance discontinuities in the line or reflected waves from non-fault lines, and has high distance measurement reliability. After the above method determines the specific fault location in the fault line, it will trigger a fault alarm in the system.

[0084] In a preferred embodiment, during the fault location process of the optical fiber communication link, to ensure that the transmitted pulse signal does not affect normal communication, a low-power detection pulse signal may be used to reduce interference with normal communication.

[0085] Choose an appropriate test time, such as performing fault location testing during idle communication hours, to avoid affecting normal communication traffic.

[0086] Preferably, wavelength division multiplexing (WDM) technology can be used to send the probe pulse signal and normal communication signal on different wavelengths to avoid mutual interference. If the fiber optic network is designed with a backup channel, the probe pulse signal can be sent on the backup channel without affecting the normal communication of the service channel.

[0087] In a preferred embodiment, during the fault location process of an optical fiber communication link, if a false alarm occurs, it can be achieved by using a variety of detection tools and methods, such as using an optical power meter to measure the optical power, or using an OTDR (Optical Time Domain Reflectometer) to perform a more detailed link test.

[0088] Analyze the causes of false alarms to determine whether they are due to environmental factors (such as temperature and humidity changes), equipment configuration errors, or excessive sensitivity of the detection system.

[0089] Check the fiber link's environment for changes, such as new construction or vegetation growth, that could affect detection results. Also, check the cleanliness of fiber connectors and equipment, as dirt can cause false alarms. Continue monitoring areas suspected of false alarms for persistent or recurring alarm signals.

[0090] In one embodiment, a computer device is further provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0091] In one embodiment, a computer-readable storage medium is provided, storing a computer program, which implements the steps in the above-mentioned method embodiments when executed by a processor.

[0092] In one embodiment, a computer program product or computer program is provided, the computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the steps of each of the above-described method embodiments.

[0093] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0094] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for locating a fault in an optical fiber communication link, characterized in that: The steps include: S1. Transmitting the same detection pulse signal to each branch of the optical fiber communication link. Installing a reflector with a different encoding mode at the end of each branch of the optical fiber communication link to encode the detection pulse signal transmitted to the reflector and reflect the encoded detection pulse signal. S2, process and analyze the w reflected coded detection pulse signals, calculate the total coded pulse and photocurrent density; the total coded pulse received at time t Expressed as: in, is the initial wavelength of the detection pulse signal, A is the initial amplitude of the detection pulse signal, is the insertion loss of the i-th reflector, represents the amplitude attenuation after passing through the i-th reflector, is the central wavelength of the i-th reflected coded detection pulse signal, is the time delay, is the Dirichlet function, is the pulse shape function; S3, based on the photocurrent density, establish a link fault judgment model to calculate the optical fiber communication link failure probability. When the threshold is exceeded, a fault is determined to have occurred. The link fault judgment model is: The photocurrent density is , P FA is the false alarm probability when the optical fiber communication link is normal, P D is the probability of correctly detecting a failure in an optical fiber communication link. To judge the threshold current of the comparator; when the optical fiber communication link fails, the expectation is a and the variance is , when the link is normal, the expectation is b and the variance is ; S4. When a fault is detected, locate the branch where the reflector that did not receive the detection pulse signal is located, and report the fault location to the system. Assume that the initial fault wave surge propagates from the fault point F along the line to the detection points at both ends of MN at the same wave speed v and the time when it reaches the detection points at both ends of M and N is T respectively. M 、T N , then the distance L from the M end and the N end to the fault point F is obtained MF and L NF for: Wherein, L is the length between the M end and the N end.

2. The fault location method according to claim 1, characterized in that: The total coded pulse signal is converted into an electrical signal by a photodetector with a gain of G, and the photocurrent at time t Expressed as: in, is the power of the total coded pulse signal, is the noise current; Expressed as: Among them, the detection period is T c .

3. The fault location method according to claim 1, wherein: In step S1, the reflector is a fiber Bragg grating reflector, and the number of Bragg gratings in each reflector is equal to the code weight of the codeword.

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