A method and apparatus for optical fiber condition detection of an all-fiber current transformer

Abstract

This invention discloses a method and apparatus for optical fiber condition detection in an all-fiber current transformer, relating to the field of optical fiber condition detection technology. The method includes: acquiring the actual pilot signal of the optical fiber link under test; separating the actual pilot signal from the pilot optical signal; receiving the pilot optical signal after transmission through the link from an injected coupling optical signal in the optical fiber link under test; obtaining the coupling optical signal from a preset pilot signal and a working optical signal; obtaining an actual health index based on the actual pilot signal and the preset pilot signal; acquiring a baseline health index; using the difference in health indices as a health index offset; statistically analyzing the actual health index to obtain the standard deviation of the health index and the short-term health index decrease; and determining the optical fiber condition based on the health index offset, the standard deviation of the health index, and the short-term health index decrease. By implementing this invention, the problem of existing optical fiber link condition detection relying on offline detection requiring link interruption or external equipment is solved, enabling online condition detection.

Description

Technical Field ,

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[0001] The present invention relates to the technical field of optical fiber state detection, and in particular to a method and device for detecting the optical fiber state of an all-optical fiber current transformer. Background Art

[0002] Optical measurement devices such as all-optical fiber current transformers (also known as pure optical CTs) are usually arranged in converter stations. Such devices transmit the optical signals collected on the high-potential side to the demodulation, metering or protection control unit on the low-potential side through an optical fiber link, so as to realize the isolated measurement of the operating current or related electrical parameters. Compared with conventional communication optical fibers, the optical fiber link supporting the pure optical CT in the converter station not only undertakes the signal transmission function, but also directly relates to the accuracy, continuity of the measurement result and the reliable operation of the protection control system. Therefore, its operating state is of high importance.

[0003] During the long-term operation process, the optical fiber link used in the pure optical CT device in the converter station will be affected by various on-site factors. For example, there are obvious temperature cycles, equipment vibrations, installation stresses, routing squeezes, electromagnetic transient impacts and local space limitations in the converter station. After long-term stress, the outer sheath, buffer layer and fixing structure of the optical fiber are prone to local flattening, surface wear, micro-cracks, reduction of bending radius, etc. The above factors will act on the optical fiber body, causing the optical fiber to generate micro-bends, local additional losses or transmission fluctuations, resulting in a decrease in received optical power, an increase in signal noise, and a deterioration in measurement stability. In severe cases, it may also cause link interruption or measurement error exceeding the limit.

[0004] Existing detection means for the state of the optical fiber link mostly use an optical time domain reflectometer, an insertion loss tester or an optical power meter for off-line detection. Although such methods can locate and identify link breakpoints, fusion loss points or sudden gain / loss positions, they generally require interrupting the original link, additionally accessing test equipment, or detecting in a non-operating state, and it is difficult to meet the requirements of long-term on-line, continuous and non-disturbing operation state monitoring of the pure optical CT link in the converter station. Summary of the Invention

[0005] The embodiments of the present invention provide a method and device for detecting the optical fiber state of an all-optical fiber current transformer, which can solve the problem that the existing optical fiber link state depends on off-line detection and requires interrupting the link or external equipment, and realizes the on-line state detection of the optical fiber link supporting the all-optical fiber current transformer in the converter station.

[0006] An embodiment of the present invention provides a method for detecting the optical fiber state of an all-optical fiber current transformer, which is applicable to a detection module in an optical fiber state detection device. The optical fiber state detection device further includes: a filter and a to-be-detected optical fiber link; The optical fiber state detection method includes: [[ID=2�]] The actual pilot signal of the fiber optic link under test is obtained; wherein the actual pilot signal is separated from the pilot optical signal by the filter; the pilot optical signal is obtained from the receiving end of the fiber optic link under test after the coupling optical signal is injected at the transmitting end and transmitted through the link; the coupling optical signal is obtained by coupling a preset pilot signal and a working optical signal. The actual health index is obtained by logarithmically normalizing the amplitude ratio of the actual pilot signal to the preset pilot signal. Obtain the baseline health index of the fiber optic link under test; The difference between the actual health index and the baseline health index is used as the health index offset. Statistical analysis was performed on the actual health index to obtain the standard deviation of the health index and the short-term decline in the health index. The fiber status of the fiber link under test is determined based on the health index offset, health index standard deviation, and short-term health index decline.

[0007] Furthermore, the fiber status includes: normal status, chronic degradation trend, abnormal fluctuation or sudden failure; The process of determining the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decline includes: If the health index offset is less than or equal to the preset chronic degradation threshold, the fiber condition of the fiber link under test is determined to be a chronic degradation trend. If the standard deviation of the health index is greater than or equal to the preset abnormal fluctuation threshold, the fiber status of the fiber link under test is determined to be abnormal fluctuation. If the short-term health index decrease is less than or equal to the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be a sudden fault. If the health index offset is greater than the preset chronic degradation threshold, the health index standard deviation is less than the preset abnormal fluctuation threshold, and the short-term health index decrease is greater than the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be normal.

[0008] Furthermore, after determining the fiber status of the fiber link under test, the process also includes: When the fiber condition of the fiber link under test shows a chronic degradation trend, a chronic degradation alarm signal is issued. When the fiber status of the fiber link under test is fluctuating abnormally, an alarm signal for abnormal link fluctuation is issued. When the fiber optic link under test experiences a sudden fault, a sudden link fault alarm signal is issued.

[0009] Furthermore, the baseline health index is determined in the following manner: The receiving pilot signal of the fiber optic link under test during stable operation is obtained; wherein, the receiving pilot signal is obtained by the filter from the composite optical signal; the composite optical signal is obtained by the injection optical signal injected at the transmitting end of the fiber optic link under test, which is transmitted through the link and received at the receiving end of the fiber optic link under test; the injection optical signal is obtained by coupling the reference pilot signal and the working optical signal. The baseline health index is obtained by logarithmically normalizing the amplitude ratio of the received pilot signal to the reference pilot signal.

[0010] Furthermore, the fiber optic status detection device also includes: a beam splitter; The coupled optical signal passes through a beam splitter, which adjusts the coupled optical signal according to the fiber type and link length of the fiber link under test, resulting in a split coupled optical signal.

[0011] Furthermore, the preset pilot signal is injected into the fiber optic link under test for a preset duration; The acquisition of the actual pilot signal at the receiving end of the fiber optic link under test includes: The actual pilot signal of the fiber optic link under test is acquired within a preset receiving window; wherein, the start time of the preset receiving window is set according to the link transmission delay, and the duration of the preset receiving window is at least equal to the preset duration; the link transmission delay is determined according to the fiber type and link length of the fiber optic link under test.

[0012] Based on the above method embodiments, the present invention provides corresponding device embodiments, including: a filter, an optical fiber link under test, and a detection module; The fiber optic link under test is used to inject a coupling optical signal at the transmitting end so that the coupling optical signal forms a pilot optical signal at the receiving end after being transmitted through the link; the coupling optical signal is obtained by coupling a preset pilot signal and a working optical signal. The filter is used to separate the actual pilot signal from the pilot optical signal; The detection module is used to acquire the actual pilot signal of the fiber optic link under test; logarithmically normalize the amplitude ratio of the actual pilot signal to the preset pilot signal to obtain the actual health index; acquire the baseline health index of the fiber optic link under test; use the difference between the actual health index and the baseline health index as the health index offset; perform statistical analysis on the actual health index to obtain the standard deviation of the health index and the short-term health index decrease; and determine the fiber status of the fiber optic link under test based on the health index offset, the standard deviation of the health index, and the short-term health index decrease.

[0013] Furthermore, the fiber status includes: normal status, chronic degradation trend, abnormal fluctuation or sudden failure; The process of determining the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decline includes: If the health index offset is less than or equal to the preset chronic degradation threshold, the fiber condition of the fiber link under test is determined to be a chronic degradation trend. If the standard deviation of the health index is greater than or equal to the preset abnormal fluctuation threshold, the fiber status of the fiber link under test is determined to be abnormal fluctuation. If the short-term health index decrease is less than or equal to the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be a sudden fault. If the health index offset is greater than the preset chronic degradation threshold, the health index standard deviation is less than the preset abnormal fluctuation threshold, and the short-term health index decrease is greater than the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be normal.

[0014] Furthermore, the fiber optic status detection device also includes an alarm module; the alarm module includes a link chronic degradation alarm unit, a link fluctuation anomaly alarm unit, and a link sudden failure alarm unit. The link chronic degradation alarm unit is used to issue a link chronic degradation alarm signal when the fiber condition of the fiber link under test is showing a chronic degradation trend. The link fluctuation anomaly alarm unit is used to issue a link fluctuation anomaly alarm signal when the fiber status of the fiber link under test is fluctuating abnormally. The link burst fault alarm unit is used to issue a link burst fault alarm signal when the optical fiber status of the optical fiber link under test is a sudden fault.

[0015] Furthermore, the baseline health index is determined in the following manner: The receiving pilot signal of the fiber optic link under test during stable operation is obtained; wherein, the receiving pilot signal is obtained by the filter from the composite optical signal; the composite optical signal is obtained by the injection optical signal injected at the transmitting end of the fiber optic link under test, which is transmitted through the link and received at the receiving end of the fiber optic link under test; the injection optical signal is obtained by coupling the reference pilot signal and the working optical signal. The baseline health index is obtained by logarithmically normalizing the amplitude ratio of the received pilot signal to the reference pilot signal.

[0016] Furthermore, the fiber optic condition detection device also includes: a beam splitter; The coupled optical signal passes through a beam splitter, which adjusts the coupled optical signal according to the fiber type and link length of the fiber link under test, resulting in a split coupled optical signal.

[0017] Further, the preset pilot signal is injected into the fiber optic link under test for a preset duration; The obtaining of the actual pilot signal at the receiving end of the fiber optic link under test includes: Obtaining the actual pilot signal of the fiber optic link under test within a preset receiving window; wherein, the start time of the preset receiving window is set according to the link transmission delay, and the time length of the preset receiving window is at least equal to the preset duration; the link transmission delay is determined according to the fiber type and link length of the fiber optic link under test.

[0018] Compared with the prior art, the beneficial effects of the embodiments of this solution are as follows: In this invention, a coupled optical signal is obtained by coupling a preset pilot signal and a working optical signal, and is injected into the transmitting end of the fiber optic link under test. After transmission, a pilot optical signal is obtained at the receiving end, and an actual pilot signal is separated from the pilot optical signal through a filter. There is no need to interrupt the link or externally connect a testing device, and online signal acquisition of the fiber optic link can be achieved. Next, considering that during the actual operation process, the output power of the light source, the response characteristics of the device, and the electronic gain may drift over time, in order to reduce the influence of the above drift factors on the discrimination of the link state, this invention performs logarithmic normalization processing on the amplitude ratio of the actual pilot signal and the preset pilot signal to obtain an actual health index, which can make the common-mode interference components such as the light source power drift, the device characteristic drift, and the electronic gain drift cancel each other out in the ratio operation. On this basis, the baseline health index of the fiber optic link under test is obtained, and the difference between the actual health index and the baseline health index is used as the health index offset to eliminate the inherent error of the device. Statistical analysis is performed on the actual health index to obtain the health index standard deviation and the short-term health index decrease amount; according to the health index offset, the health index standard deviation, and the short-term health index decrease amount, the fiber state of the fiber optic link under test is determined.

[0019] In summary, this invention online collects the actual pilot signal formed by the transmission of the preset pilot signal at the transmitting end at the receiving end, and constructs a health index based on the pilot signal, so that the link state detection can be completed without interrupting the operation of the fiber optic link and without externally connecting a dedicated testing device, solving the problem that the existing fiber optic link state depends on offline detection and requires interrupting the link or externally connecting a device, and realizing the online state detection of the fiber optic link supporting the fully fiber optic current transformer in the converter station. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic flowchart of a method for detecting the fiber state of a fully fiber optic current transformer provided by an embodiment of this invention; Figure 2 is a schematic structural diagram of a device for detecting the fiber state of a fully fiber optic current transformer provided by an embodiment of this invention; Figure 3This is another structural schematic diagram of the fiber optic condition detection device for an all-fiber current transformer provided in one embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0023] like Figure 1 As shown, to address the issue that existing fiber optic link status detection relies on offline methods requiring link interruption or external equipment, an embodiment of this invention provides a fiber optic status detection method using an all-fiber optic current transformer. This method is applicable to the detection module in a fiber optic status detection device, such as... Figure 2 As shown, the optical fiber status detection device further includes: a filter and the optical fiber link under test; The fiber optic condition detection method includes at least the following steps: Step S1: Obtain the actual pilot signal of the fiber optic link under test; wherein, the actual pilot signal is obtained by the filter separating it from the pilot optical signal; the pilot optical signal is obtained by the fiber optic link under test receiving the receiving end after the coupled optical signal is injected at the transmitting end and transmitted through the link; the coupled optical signal is obtained by coupling a preset pilot signal and a working optical signal. For step S1, in the fiber optic condition detection device, the detection module first acquires the actual pilot signal of the fiber optic link under test. To achieve this process, the fiber optic condition detection device further includes: a pilot signal generation module and a coupler; wherein, the pilot signal generation module is connected to the transmitting end of the fiber optic link under test through the coupler.

[0024] The pilot signal generation module generates a preset pilot signal with a preset wavelength, modulation frequency, timing characteristics and power parameters. In this embodiment, the preset pilot signal generated by the pilot signal generation module can be a single-frequency sinusoidal modulation signal, or it can be a continuous wave, pulse envelope wave, sweep frequency signal or multi-tone combination signal with multiple predetermined frequencies. If necessary, it can also be implemented by time-division injection or multi-frequency combination.

[0025] The aforementioned preset pilot signal is transmitted to the coupler and coupled with the working optical signal to obtain a coupled optical signal. The coupled optical signal is injected into the fiber optic link under test through the transmitting end of the fiber optic link under test. The injected preset pilot signal is transmitted along the fiber optic link under test. During the transmission process, it is affected by the inherent attenuation of the fiber optic link, joint loss, bending loss, polarization disturbance, and external environmental factors (such as temperature, vibration, etc.), and its light intensity, phase, and amplitude characteristics change accordingly. Finally, the receiving end of the fiber optic link under test outputs the pilot optical signal.

[0026] It should be noted that the working optical signal is the normal operating signal of the fiber optic link under test in the all-fiber current transformer, which undertakes the core function of current measurement; the preset pilot signal is an additional monitoring signal coupled into the link, which does not undertake the original measurement function, but is only used to characterize the changes in the transmission characteristics of the fiber optic link.

[0027] The above-mentioned pilot optical signal is filtered to remove the working optical signal component that carries the current measurement function. The extracted pilot component is the actual pilot signal.

[0028] Since the pilot signal is transmitted in the link as an optical signal, it needs to be converted into an electrical signal to facilitate subsequent digital analysis of the signal's amplitude, phase, frequency, and other characteristics. Therefore, preferably, the fiber optic state detection device also includes a reference photodetector and a receiving photodetector. The reference photodetector is connected to the pilot signal generation module to obtain the amplitude corresponding to the preset pilot signal before the preset pilot signal is injected into the link; the receiving photodetector is connected to the filter to obtain the amplitude corresponding to the filtered actual pilot signal.

[0029] It should be noted that the amplitude values ​​obtained from the reference photodetector and the receiving photodetector are transmitted to the detection module, providing a direct basis for the subsequent calculation of the baseline health index, the actual health index, and related state characteristics.

[0030] Preferably, in this invention, the low-voltage side of the fiber optic link under test is set as the transmitting end, and the high-voltage side of the fiber optic link under test is set as the receiving end. The main reason for adopting this arrangement is that the propagation direction of the preset pilot signal in the fiber optic link under test is opposite to the propagation direction of the original working optical signal of the all-fiber current transformer. Thus, the independent transmission and identification of additional monitoring signals can be achieved without changing the original measurement function and main signal transmission path of the all-fiber current transformer.

[0031] Furthermore, by pre-setting the pilot signal and the working optical signal to form a reverse separation in the transmission direction, the impact of the pilot injection process on the stability of the original measurement signal can be reduced, and the disturbance to the normal measurement accuracy of the all-fiber current transformer can be decreased. At the same time, it is convenient to selectively extract and analyze the pilot signal at the receiving end, thereby improving the accuracy and anti-interference capability of the link status monitoring results. Especially in the high-voltage, strong electromagnetic transient, and complex equipment layout environment of converter stations, the above-mentioned low-voltage side injection and high-voltage side monitoring structure is beneficial to suppressing additional coupling interference and improving the stability and engineering applicability of the device during long-term online operation.

[0032] In a preferred embodiment, the preset pilot signal is injected into the transmitter of the fiber optic link under test for a preset duration; The acquisition of the actual pilot signal at the receiving end of the fiber optic link under test includes: The actual pilot signal of the fiber optic link under test at the receiving end is acquired within a preset receiving window; wherein, the start time of the preset receiving window is set according to the link transmission delay, and the duration of the preset receiving window is at least equal to the preset duration; the link transmission delay is determined according to the fiber type and link length of the fiber optic link under test.

[0033] In one embodiment of the present invention, the transmitting end and the receiving end of the optical fiber status detection device each have an independent built-in clock module. The clock module enables the timing transmission of the preset pilot signal and the timing reception of the actual pilot signal, reducing the additional structure introduced by the cross-end communication module and improving the device's independent operation capability and engineering applicability in the complex electromagnetic environment of the converter station.

[0034] To reduce the time deviation between transmission and reception caused by internal clock accumulation errors, device response delays, or long-term operational drift, this invention coordinates the transmission duration of the preset pilot signal with the reception window. Specifically, the preset pilot signal is injected into the transmitting end of the fiber optic link under test for a preset duration, and the receiving end collects the actual pilot signal within the preset reception window. The start time of the preset reception window is set according to the link transmission delay, and the window length is at least equal to the preset duration. The link transmission delay is predetermined according to the fiber type and link length of the fiber optic link under test, thereby ensuring that the reception window can completely cover the expected time range of signal transmission.

[0035] In this embodiment, the duration of each optical signal occurrence is set to 1 millisecond. This duration can fully cover the transmission delay fluctuation range of conventional optical fiber links, enabling the receiver to stably capture the pilot optical signal within a preset receiving window.

[0036] In a preferred embodiment, the fiber optic status detection device further includes: a beam splitter; The coupled optical signal passes through a beam splitter, which adjusts the coupled optical signal according to the fiber type and link length of the fiber link under test, resulting in a split coupled optical signal.

[0037] In one embodiment of the present invention, it should be noted that when replacing the fiber optic link under test, the differences in key parameters such as inherent transmission loss, dispersion characteristics, and polarization sensitivity of different types or specifications of optical fibers will directly affect the transmission attenuation and waveform characteristics of the pilot signal. Therefore, when replacing the fiber optic link under test, it is necessary to reset the relevant parameters of the pilot signal to adapt to the transmission characteristics of the new link and ensure the accuracy of subsequent monitoring results.

[0038] To improve applicability to different field conditions and different fiber optic configurations, this invention fixes the frequency of a preset pilot signal to address transmission differences caused by different fiber types, link lengths, or additional loss conditions. Before the coupled optical signal enters the fiber optic link under test, the injection intensity of the coupled optical signal is adjusted by a beam splitter.

[0039] Specifically, while connecting to the fiber optic link under test, the splitting ratio of the beam splitter is determined based on the fiber type and link length of the fiber optic link, combined with a preset mapping table. The fiber type determines the inherent attenuation coefficient and dispersion characteristics of the signal transmission, while the link length determines the total cumulative attenuation of the signal. Then, the intensity of the coupled optical signal is adjusted by the beam splitter according to the determined splitting ratio to obtain a split coupled optical signal. The split coupled optical signal is then injected into the fiber optic link under test, so that the device can maintain good detection sensitivity, dynamic range, and identification accuracy under different types, specifications, or loss levels of fiber optic applications.

[0040] It should be noted that before the fiber optic condition detection device is put into operation, the operating wavelength, frequency range, modulation characteristics, receiving sensitivity range, and allowable additional power range of the working optical signal of the fiber optic link under test in the all-fiber current transformer should be read or detected so that pilot signal parameters that will not have a significant impact on the measurement process of the original all-fiber current transformer can be selected in the future.

[0041] like Figure 3The diagram shows another structural schematic of the fiber optic condition detection device, including a pilot signal generation module, a reference photodetector, a coupler, the fiber optic link under test, a filter, a receiving photodetector, and a detection module. The pilot signal generation module generates a preset pilot signal, which is directly acquired and output by the reference photodetector. Simultaneously, the preset pilot signal is transmitted to the coupler and coupled with the working optical signal of the all-fiber current transformer to obtain a coupled optical signal. The coupled optical signal is then split by a beam splitter according to a preset splitting ratio and injected into the transmitting end of the fiber optic link under test. After transmission through the fiber optic cable, the pilot optical signal is obtained at the receiving end of the fiber optic link under test. The pilot optical signal is filtered to remove the working optical signal, resulting in the actual pilot signal. The actual pilot signal is acquired by the receiving photodetector and then transmitted to the detection module.

[0042] Step S2: Logarithmically normalize the amplitude ratio of the actual pilot signal to the preset pilot signal to obtain the actual health index; For step S2, the present invention characterizes the link status by the change in the transmission amplitude of a preset pilot signal in the optical fiber link under test.

[0043] For the fiber optic link under test, at the pilot frequency At this point, its equivalent transmission characteristic can be expressed as a pilot amplitude attenuation process. Let the fiber baseline attenuation coefficient be... The unit is dB / km, and the link length of the fiber optic link under test is... The unit is km, and the additional attenuation caused by outer skin extrusion, local bending, micro-bending loss, or other defects is... The unit is dB / km, then at time The amplitude of the actual pilot signal measured at the receiving end It can be represented as: ; in, This indicates the amplitude corresponding to the preset pilot signal. Indicates the pilot frequency The corresponding fixed transmission term comprehensively characterizes the fixed gain or fixed loss formed by the injection structure, coupling devices, beam splitting devices, receiver-detector link, and front-end gain circuitry. This represents the amplitude corresponding to the actual pilot signal.

[0044] Considering that the output power of the light source, the response characteristics of the device, and the electronic gain may drift over time during actual operation, in order to reduce the impact of the above drift factors on the link status judgment, this invention adopts a source reference normalization method to construct a health index. Specifically, the ratio of the amplitude of the actual pilot signal to that of the preset pilot signal is logarithmically normalized to obtain the actual health index. The specific formula is as follows: ; in, Indicates at time The actual health index of the fiber optic link to be tested.

[0045] It should be noted that the actual health index Essentially, it reflects the normalized transmission level of the preset pilot signal during the transmission to reception process. Compared with directly using the received amplitude for discrimination, the above normalization method can effectively reduce the errors caused by the fluctuation of the transmitting optical power and the electronic drift of the front-end.

[0046] Step S3: Obtain the baseline health index of the fiber optic link under test; For step S3, retrieve the baseline health index of the fiber optic link to be tested from the database.

[0047] It should be noted that the baseline health index is calculated by collecting the amplitude of the reference pilot signal and the amplitude of the received pilot signal under normal operating conditions with no faults and no additional losses before the fiber optic link under test is put into operation.

[0048] In a preferred embodiment, the baseline health index is determined in the following manner: The receiving pilot signal of the fiber optic link under test during stable operation is obtained; wherein, the receiving pilot signal is obtained by the filter from the composite optical signal; the composite optical signal is obtained by the injection optical signal injected at the transmitting end of the fiber optic link under test, which is transmitted through the link and received at the receiving end of the fiber optic link under test; the injection optical signal is obtained by coupling the reference pilot signal and the working optical signal. The baseline health index is obtained by logarithmically normalizing the amplitude ratio of the received pilot signal to the reference pilot signal.

[0049] In one embodiment of the present invention, before the fiber optic link under test is put into operation, when the fiber optic link under test is running stably, a reference pilot signal is transmitted to a coupler; the coupler couples the reference pilot signal with the working optical signal to obtain an injected optical signal; the injected optical signal is injected into the transmitting end of the fiber optic link under test, transmitted through the fiber optic link, and a composite optical signal is obtained from the receiving end of the fiber optic link under test; the composite optical signal is transmitted to a filter so that the filter filters out the working optical signal in the composite optical signal and separates the receiving pilot signal.

[0050] Next, the amplitude ratio of the received pilot signal to the reference pilot signal is logarithmically normalized to obtain the baseline health index, as shown in the following formula: ; in, Indicates baseline health index, This indicates the amplitude corresponding to the received pilot signal. This indicates the amplitude corresponding to the reference pilot signal.

[0051] It should be noted that before re-commissioning a fiber optic link after a complete overhaul or replacement of the fiber, the reference pilot signal and the received pilot signal must be re-acquired according to the same procedure as before re-commissioning, and the baseline health index of the link must be calculated and updated, under the condition that the link has returned to stable operation.

[0052] Step S4: Use the difference between the actual health index and the baseline health index as the health index offset. For step S4, the difference between the actual health index of the fiber optic link under test and the pre-measured baseline health index is used to obtain the health index offset, and the specific formula is as follows: ; in, This indicates the offset of the health index.

[0053] When the health index offset When the loss continues to decrease, it indicates that the additional loss of the fiber optic link under test has increased compared to the baseline state, suggesting that the fiber optic link under test may have gradually developing problems such as compression, microbending, uneven stress, or local damage.

[0054] Step S5: Perform statistical analysis on the actual health index to obtain the standard deviation of the health index and the short-term decline in the health index; For step S5, in order to reflect the time-varying fluctuation characteristics of the fiber optic link under test within a certain time range, the present invention uses a time window... The actual health index is statistically analyzed within the time window. Internal collection A sample of actual health index First, calculate the time window. Inside A sample of actual health index The average value is then used to calculate the standard deviation of the health index by taking the square root of the variance. The specific formula is as follows: ; in, Indicates the standard deviation of the health index. Indicates time window Inside A sample of actual health index The average value.

[0055] It should be noted that the standard deviation of the health index This indicator reflects the fluctuation of the actual pilot signal over a short time period. When the fiber optic link under test has unstable contact, local loosening, intermittent pressure, or minor structural changes caused by thermal expansion and contraction, the amplitude of the actual pilot signal will usually exhibit significant time-varying fluctuations. Therefore, the standard deviation of the pilot signal can be used to reflect these fluctuations. Identify this type of abnormal state.

[0056] Furthermore, in order to capture sudden changes and short-term degradation trends in the health status of the fiber optic link under test, this invention calculates the short-term health index decrease by comparing the actual health index at the current moment with that at the previous moment. The specific formula is as follows: ; in, Indicates at time The short-term health index decline of the fiber optic link under test. Indicates at time The actual health index of the fiber optic link under test. This indicates the preset short-time analysis interval. Set to a smaller value to ensure that the calculation results can reflect the rapid changes in the link in a short period of time, thereby enabling rapid identification of abnormal conditions such as sudden loss, vibration or loose joints in the fiber optic link.

[0057] When the short-term health index decreases A rapid increase indicates that the link health index at the current moment has dropped significantly compared to the previous moment, suggesting that the fiber optic link has experienced sudden additional losses or transmission performance degradation, such as loose connectors, fiber micro-bending, external impacts or vibrations, or other abnormal operating conditions.

[0058] Step S6: Determine the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decrease.

[0059] In a preferred embodiment, the fiber status includes: normal status, chronic degradation trend, fluctuating abnormality, or sudden failure; The process of determining the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decline includes: If the health index offset is less than or equal to the preset chronic degradation threshold, the fiber condition of the fiber link under test is determined to be a chronic degradation trend. If the standard deviation of the health index is greater than or equal to the preset abnormal fluctuation threshold, the fiber status of the fiber link under test is determined to be abnormal fluctuation. If the short-term health index decrease is less than or equal to the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be a sudden fault. If the health index offset is greater than the preset chronic degradation threshold, the health index standard deviation is less than the preset abnormal fluctuation threshold, and the short-term health index decrease is greater than the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be normal.

[0060] For step S6, the preset chronic degradation threshold is set in advance. The preset fluctuation anomaly threshold and the preset mutation failure threshold .

[0061] It should be noted that the above thresholds can be adjusted according to the power margin of the fiber optic link under test, the on-site operating environment, the false alarm tolerance, and the operation and maintenance strategy, so as to meet the application requirements of different converter station scenarios.

[0062] During continuous real-time monitoring of the fiber optic link, the health index offset is continuously calculated and updated. When the health index offset of the fiber optic link under test Less than or equal to the preset chronic degradation threshold ,Right now When the fiber condition of the fiber link under test is determined to be a chronic degradation trend, this criterion is mainly used to identify abnormal states such as slow increase of additional loss, long-term pressure or gradual aggravation of micro-bending.

[0063] Continuously update the standard deviation of the health index When the standard deviation of the health index of the fiber optic link under test Greater than or equal to the preset abnormal fluctuation threshold ,Right now When the fiber optic link under test is determined to be in an abnormal state of fluctuation, this criterion is mainly used to identify abnormal states such as loose connection, intermittent stress, unstable local contact, or significant impact from environmental changes.

[0064] Continuously update the short-term health index decline. ,Right now When the short-term health index decrease of the fiber optic link under test is less than or equal to the preset sudden fault threshold, ,Right now When the fiber optic link under test is determined to be in a sudden fault state, this criterion is mainly used to identify situations such as sudden compression, severe bending, connector abnormality, or rapid development of local damage to the link.

[0065] In addition, when the health index offset is met simultaneously Greater than the preset chronic degradation threshold Health index standard deviation Less than the preset abnormal fluctuation threshold And the short-term decline in health index Greater than the preset sudden failure threshold Under the condition that the fiber status of the fiber link under test is normal, the transmission loss of the fiber link under test does not increase continuously, the signal fluctuation amplitude is within the normal range and there is no sudden drop in the health index, the pilot signal transmission is stable, and it can be confirmed that the fiber link under test is currently free from chronic degradation, abnormal fluctuations and sudden failures, and the overall operating status is good.

[0066] In a preferred embodiment, after determining the fiber status of the fiber link under test, the method further includes: When the fiber condition of the fiber link under test shows a chronic degradation trend, a chronic degradation alarm signal is issued. When the fiber status of the fiber link under test is fluctuating abnormally, an alarm signal for abnormal link fluctuation is issued. When the fiber optic link under test experiences a sudden fault, a sudden link fault alarm signal is issued.

[0067] In one embodiment of the present invention, after step S6, when the fiber condition of the fiber link under test is determined to be a chronic degradation trend, the fiber condition detection device issues a chronic degradation alarm signal through the alarm module, indicating that the additional loss of the link is slowly increasing, which may be caused by long-term pressure, micro-bending, or connector aging. When the fiber condition of the fiber link under test is determined to be abnormal fluctuation, the alarm module issues an abnormal fluctuation alarm signal, indicating that the pilot signal has unexpected short-term amplitude fluctuations during transmission, which may be caused by external vibration, electromagnetic interference, or unstable connector contact. When the fiber condition of the fiber link under test is determined to be a sudden fault, the alarm module issues a sudden fault alarm signal, indicating that the link has experienced severe additional loss or transmission interruption, which usually corresponds to sudden faults such as fiber breakage, connector detachment, or severe compression.

[0068] It should be noted that different types of alarm signals can be set with different priorities. This allows for the priority processing and push of higher-priority alarms when multiple anomalies occur simultaneously or multiple alarm signals are triggered at the same time. This ensures that maintenance personnel can pay attention to and handle fault alarms with greater impact as soon as possible, thereby improving overall maintenance efficiency and the timeliness of fault handling.

[0069] Preferably, the actual pilot signal, preset pilot signal, actual health index, baseline health index, health index offset, health index standard deviation, short-term health index decrease, and fiber status of the fiber link under test obtained during the fiber status detection process of the present invention are uploaded in real time to the monitoring platform or operation and maintenance backend through the communication unit to realize remote visualization of the health status of the fiber link.

[0070] Preferably, when the optical fiber is in a state of chronic degradation, abnormal fluctuation, or sudden failure, a power outage inspection, replacement of the optical fiber link, or switching to a backup link should be performed.

[0071] During the long-term operation of the converter station, the optical fiber inside the all-fiber current transformer may be affected by factors such as compression from the outer sheath, stress concentration during installation, loosening of the fixing structure, reduction of local bending radius, repeated thermal expansion and contraction, or local mechanical deformation. This can lead to phenomena such as micro-bending additional attenuation, increased additional loss at the splice point, or enhanced short-term fluctuations in the optical fiber link.

[0072] This invention, by performing pilot injection and pilot detection at both ends of the optical fiber link, enables continuous acquisition of pilot transmission characteristics without interrupting operation, and combines this with actual health indices. Health index offset Health index standard deviation and the amount of short-term health index decline These characteristic parameters are used to determine whether there are any abnormal conditions in the optical fibers inside the all-fiber current transformer.

[0073] Compared to offline inspections only after link failure, this invention is more suitable for online early warning scenarios of fiber optic links within all-fiber current transformers in converter stations. This method does not require precise spatial location of the defect; instead, it directly determines whether a power outage inspection, link replacement, or switching to a backup link is necessary based on changes in link transmission status. Therefore, it better meets the application needs of converter stations, which prioritize early warning and operational decision-making.

[0074] Based on the above method embodiments, corresponding apparatus embodiments are provided; One embodiment of the present invention provides an optical fiber condition detection device for an all-fiber current transformer, comprising: a filter, an optical fiber link under test, and a detection module; The fiber optic link under test is used to inject a coupling optical signal at the transmitting end so that the coupling optical signal forms a pilot optical signal at the receiving end after being transmitted through the link; the coupling optical signal is obtained by coupling a preset pilot signal and a working optical signal. The filter is used to separate the actual pilot signal from the pilot optical signal; The detection module is used to acquire the actual pilot signal of the fiber optic link under test; logarithmically normalize the amplitude ratio of the actual pilot signal to the preset pilot signal to obtain the actual health index; acquire the baseline health index of the fiber optic link under test; use the difference between the actual health index and the baseline health index as the health index offset; perform statistical analysis on the actual health index to obtain the standard deviation of the health index and the short-term health index decrease; and determine the fiber status of the fiber optic link under test based on the health index offset, the standard deviation of the health index, and the short-term health index decrease.

[0075] In one embodiment of the present invention, the optical fiber status detection device further includes: a pilot signal generation module and a coupler; wherein the pilot signal generation module is connected to the transmitting end of the optical fiber link under test via the coupler.

[0076] The pilot signal generation module generates a preset pilot signal, which is transmitted to the coupler and coupled with the working optical signal to obtain a coupled optical signal. The coupled optical signal is injected into the fiber optic link under test through the transmitting end. The injected preset pilot signal is transmitted along the fiber optic link under test. During the transmission process, it is affected by the inherent attenuation of the fiber optic link, joint loss, bending loss, polarization disturbance, and external environmental factors (such as temperature and vibration), and its light intensity, phase, and amplitude characteristics change accordingly. Finally, the receiving end of the fiber optic link under test outputs the pilot optical signal.

[0077] The above-mentioned pilot optical signal is filtered to remove the working optical signal component that carries the current measurement function. The extracted pilot component is the actual pilot signal.

[0078] Considering that the output power of the light source, the response characteristics of the device, and the electronic gain may drift over time during actual operation, in order to reduce the impact of the above drift factors on the link status judgment, after the detection module obtains the actual pilot signal of the fiber optic link under test, it constructs a health index using a transmitter reference normalization method. Specifically, the ratio of the amplitude of the actual pilot signal to that of the preset pilot signal is logarithmically normalized to obtain the actual health index. The specific formula is as follows: ; in, Indicates at time The actual health index of the fiber optic link to be tested.

[0079] The baseline health index of the fiber optic link under test is retrieved from the database, and the difference between the actual health index of the fiber optic link under test and the pre-measured baseline health index is calculated to obtain the health index offset. The specific formula is as follows: ; in, This indicates the offset of the health index.

[0080] To reflect the time-varying fluctuation characteristics of the fiber optic link under test within a certain time range, the detection module uses a time window... The actual health index is statistically analyzed within the time window. Internal collection A sample of actual health index First, calculate the time window. Inside A sample of actual health index The average value is then used to calculate the standard deviation of the health index by taking the square root of the variance. The specific formula is as follows: ; in, Indicates the standard deviation of the health index. Indicates time window Inside A sample of actual health index The average value.

[0081] In addition, to capture sudden changes and short-term degradation trends in the health status of the fiber optic link under test, the detection module calculates the short-term decrease in the health index by comparing the actual health index at the current moment with that at the previous moment. The specific formula is as follows: ; in, Indicates at time The short-term health index decline of the fiber optic link under test. Indicates at time The actual health index of the fiber optic link under test. This indicates the preset short-time analysis interval. Set to a smaller value to ensure that the calculation results can reflect the rapid changes in the link in a short period of time, thereby enabling rapid identification of abnormal conditions such as sudden loss, vibration or loose joints in the fiber optic link.

[0082] Finally, the health index offset, health index standard deviation, and short-term health index decrease are compared with their respective preset thresholds to determine the fiber status of the fiber link under test.

[0083] In a preferred embodiment, the fiber status includes: normal status, chronic degradation trend, fluctuating abnormality, or sudden failure; The process of determining the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decline includes: If the health index offset is less than or equal to the preset chronic degradation threshold, the fiber condition of the fiber link under test is determined to be a chronic degradation trend. If the standard deviation of the health index is greater than or equal to the preset abnormal fluctuation threshold, the fiber status of the fiber link under test is determined to be abnormal fluctuation. If the short-term health index decrease is less than or equal to the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be a sudden fault. If the health index offset is greater than the preset chronic degradation threshold, the health index standard deviation is less than the preset abnormal fluctuation threshold, and the short-term health index decrease is greater than the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be normal.

[0084] In one embodiment of the present invention, the preset chronic degradation threshold is set in advance. The preset fluctuation anomaly threshold and the preset mutation failure threshold .

[0085] During continuous real-time monitoring of the fiber optic link, the health index offset is continuously calculated and updated. When the health index offset of the fiber optic link under test Less than or equal to the preset chronic degradation threshold ,Right now When the fiber condition of the fiber link under test is determined to be a chronic degradation trend, this criterion is mainly used to identify abnormal states such as slow increase of additional loss, long-term pressure or gradual aggravation of micro-bending.

[0086] Continuously update the standard deviation of the health index When the standard deviation of the health index of the fiber optic link under test Greater than or equal to the preset abnormal fluctuation threshold ,Right now When the fiber optic link under test is determined to be in an abnormal state of fluctuation, this criterion is mainly used to identify abnormal states such as loose connection, intermittent stress, unstable local contact, or significant impact from environmental changes.

[0087] Continuously update the short-term health index decline. ,Right now When the short-term health index decrease of the fiber optic link under test is less than or equal to the preset sudden fault threshold, ,Right now When the fiber optic link under test is determined to be in a sudden fault state, this criterion is mainly used to identify situations such as sudden compression, severe bending, connector abnormality, or rapid development of local damage to the link.

[0088] In addition, when the health index offset is met simultaneously Greater than the preset chronic degradation threshold Health index standard deviation Less than the preset abnormal fluctuation threshold And the short-term decline in health index Greater than the preset sudden failure threshold Under the condition that the fiber status of the fiber link under test is normal, the transmission loss of the fiber link under test does not increase continuously, the signal fluctuation amplitude is within the normal range and there is no sudden drop in the health index, the pilot signal transmission is stable, and it can be confirmed that the fiber link under test is currently free from chronic degradation, abnormal fluctuations and sudden failures, and the overall operating status is good.

[0089] In a preferred embodiment, the fiber optic status detection device further includes: an alarm module; the alarm module includes: a link chronic degradation alarm unit, a link fluctuation anomaly alarm unit, and a link sudden failure alarm unit; The link chronic degradation alarm unit is used to issue a link chronic degradation alarm signal when the fiber condition of the fiber link under test is showing a chronic degradation trend. The link fluctuation anomaly alarm unit is used to issue a link fluctuation anomaly alarm signal when the fiber status of the fiber link under test is fluctuating abnormally. The link burst fault alarm unit is used to issue a link burst fault alarm signal when the optical fiber status of the optical fiber link under test is a sudden fault.

[0090] In one embodiment of the present invention, when the fiber condition of the fiber link under test is determined to be a chronic degradation trend, the link chronic degradation alarm unit in the alarm module is triggered, and a link chronic degradation alarm signal is issued, indicating that the additional loss of the link is slowly increasing, which may be caused by long-term pressure, micro-bending, or connector aging. When the fiber condition of the fiber link under test is determined to be abnormal fluctuation, the link fluctuation abnormality alarm unit in the alarm module is triggered, and a link fluctuation abnormality alarm signal is issued, indicating that the pilot signal has unexpected short-term amplitude fluctuations during transmission, which may be caused by external vibration, electromagnetic interference, or unstable connector contact. When the fiber condition of the fiber link under test is determined to be a sudden fault, the link sudden fault alarm unit in the alarm module is triggered, and a link sudden fault alarm signal is issued, indicating that the link has experienced severe additional loss or transmission interruption, which usually corresponds to sudden faults such as fiber breakage, connector detachment, or severe compression.

[0091] In a preferred embodiment, the baseline health index is determined in the following manner: The receiving pilot signal of the fiber optic link under test during stable operation is obtained; wherein, the receiving pilot signal is obtained by the filter from the composite optical signal; the composite optical signal is obtained by the injection optical signal injected at the transmitting end of the fiber optic link under test, which is transmitted through the link and received at the receiving end of the fiber optic link under test; the injection optical signal is obtained by coupling the reference pilot signal and the working optical signal. The baseline health index is obtained by logarithmically normalizing the amplitude ratio of the received pilot signal to the reference pilot signal.

[0092] In one embodiment of the present invention, before the fiber optic link under test is put into operation, when the fiber optic link under test is running stably, a reference pilot signal is transmitted to a coupler; the coupler couples the reference pilot signal with the working optical signal to obtain an injected optical signal; the injected optical signal is injected into the transmitting end of the fiber optic link under test, transmitted through the fiber optic link, and a composite optical signal is obtained from the receiving end of the fiber optic link under test; the composite optical signal is transmitted to a filter so that the filter filters out the working optical signal in the composite optical signal and separates the receiving pilot signal.

[0093] Next, the amplitude ratio of the received pilot signal to the reference pilot signal is logarithmically normalized to obtain the baseline health index, as shown in the following formula: ; in, Indicates baseline health index, This indicates the amplitude corresponding to the received pilot signal. This indicates the amplitude corresponding to the reference pilot signal.

[0094] In a preferred embodiment, the fiber optic status detection device further includes: a beam splitter; The coupled optical signal passes through a beam splitter, which adjusts the coupled optical signal according to the fiber type and link length of the fiber link under test, resulting in a split coupled optical signal.

[0095] In one embodiment of the present invention, in order to improve the applicability to different field conditions and different fiber configurations, a beam splitter is introduced into the fiber condition detection device. For the transmission differences caused by different fiber types, different link lengths or different additional loss conditions, the frequency of the preset pilot signal is fixed, and the injection intensity of the coupled optical signal is adjusted by the beam splitter before the coupled optical signal enters the fiber link under test.

[0096] Specifically, while connecting to the fiber optic link under test, the splitting ratio of the beam splitter is determined based on the fiber type and link length of the fiber optic link, combined with a preset mapping table. The fiber type determines the inherent attenuation coefficient and dispersion characteristics of the signal transmission, while the link length determines the total cumulative attenuation of the signal. Then, the intensity of the coupled optical signal is adjusted by the beam splitter according to the determined splitting ratio to obtain a split coupled optical signal. The split coupled optical signal is then injected into the fiber optic link under test, so that the device can maintain good detection sensitivity, dynamic range, and identification accuracy under different types, specifications, or loss levels of fiber optic applications.

[0097] In a preferred embodiment, the preset pilot signal is injected into the fiber optic link under test for a preset duration; The acquisition of the actual pilot signal at the receiving end of the fiber optic link under test includes: The actual pilot signal of the fiber optic link under test is acquired within a preset receiving window; wherein, the start time of the preset receiving window is set according to the link transmission delay, and the duration of the preset receiving window is at least equal to the preset duration; the link transmission delay is determined according to the fiber type and link length of the fiber optic link under test.

[0098] In one embodiment of the present invention, the transmitting end and the receiving end of the optical fiber status detection device each have an independent built-in clock module. The clock module enables the timing transmission of the preset pilot signal and the timing reception of the actual pilot signal, reducing the additional structure introduced by the cross-end communication module and improving the device's independent operation capability and engineering applicability in the complex electromagnetic environment of the converter station.

[0099] To reduce the time deviation between transmission and reception caused by internal clock cumulative errors, device response delays, or long-term operational drift, the fiber optic condition detection device of the present invention coordinates the transmission duration of the preset pilot signal with the reception window. Specifically, the preset pilot signal is injected into the transmitting end of the fiber optic link under test for a preset duration, and the receiving end collects the actual pilot signal within the preset reception window. The start time of the preset reception window is set according to the link transmission delay, and the window length is at least equal to the preset duration. The link transmission delay is predetermined according to the fiber type and link length of the fiber optic link under test, thereby ensuring that the reception window can completely cover the expected time range of signal transmission.

[0100] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can implement the fiber optic status detection method for the all-fiber current transformer provided by any of the above-described method embodiments of the present invention.

[0101] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0102] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for optical fiber condition detection in an all-fiber current transformer, characterized in that, A detection module suitable for use in an optical fiber condition detection device, the optical fiber condition detection device further comprising: a filter and an optical fiber link under test; The optical fiber status detection method includes: The actual pilot signal of the fiber optic link under test is obtained; wherein the actual pilot signal is separated from the pilot optical signal by the filter; the pilot optical signal is obtained from the receiving end of the fiber optic link under test after the coupling optical signal is injected at the transmitting end and transmitted through the link; the coupling optical signal is obtained by coupling a preset pilot signal and a working optical signal. The actual health index is obtained by logarithmically normalizing the amplitude ratio of the actual pilot signal to the preset pilot signal. Obtain the baseline health index of the fiber optic link under test; The difference between the actual health index and the baseline health index is used as the health index offset. Statistical analysis was performed on the actual health index to obtain the standard deviation of the health index and the short-term decline in the health index. The fiber status of the fiber link under test is determined based on the health index offset, health index standard deviation, and short-term health index decline.

2. The fiber optic condition detection method for an all-fiber current transformer according to claim 1, characterized in that, The fiber status includes: normal status, chronic degradation trend, abnormal fluctuation or sudden failure; The process of determining the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decline includes: If the health index offset is less than or equal to the preset chronic degradation threshold, the fiber condition of the fiber link under test is determined to be a chronic degradation trend. If the standard deviation of the health index is greater than or equal to the preset abnormal fluctuation threshold, the fiber status of the fiber link under test is determined to be abnormal fluctuation. If the short-term health index decrease is less than or equal to the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be a sudden fault. If the health index offset is greater than the preset chronic degradation threshold, the health index standard deviation is less than the preset abnormal fluctuation threshold, and the short-term health index decrease is greater than the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be normal.

3. The fiber optic condition detection method for an all-fiber current transformer according to claim 2, characterized in that, After determining the fiber status of the fiber link under test, the following steps are also included: When the fiber condition of the fiber link under test shows a chronic degradation trend, a chronic degradation alarm signal is issued. When the fiber status of the fiber link under test is fluctuating abnormally, an alarm signal for abnormal link fluctuation is issued. When the fiber optic link under test experiences a sudden fault, a sudden link fault alarm signal is issued.

4. The fiber optic condition detection method for an all-fiber current transformer according to claim 1, characterized in that, The baseline health index is determined in the following way: The receiving pilot signal of the fiber optic link under test during stable operation is obtained; wherein, the receiving pilot signal is obtained by the filter from the composite optical signal; the composite optical signal is obtained by the injection optical signal injected at the transmitting end of the fiber optic link under test, which is transmitted through the link and received at the receiving end of the fiber optic link under test; the injection optical signal is obtained by coupling the reference pilot signal and the working optical signal. The baseline health index is obtained by logarithmically normalizing the amplitude ratio of the received pilot signal to the reference pilot signal.

5. The fiber optic condition detection method for an all-fiber current transformer according to claim 1, characterized in that, The fiber optic status detection device further includes: a beam splitter; The coupled optical signal passes through a beam splitter, which adjusts the coupled optical signal according to the fiber type and link length of the fiber link under test, resulting in a split coupled optical signal.

6. The fiber optic condition detection method for an all-fiber current transformer according to claim 1, characterized in that, The preset pilot signal is injected into the fiber optic link under test for a preset duration; The acquisition of the actual pilot signal at the receiving end of the fiber optic link under test includes: The actual pilot signal of the fiber optic link under test is acquired within a preset receiving window; wherein, the start time of the preset receiving window is set according to the link transmission delay, and the duration of the preset receiving window is at least equal to the preset duration; the link transmission delay is determined according to the fiber type and link length of the fiber optic link under test.

7. A fiber optic condition detection device for an all-fiber optic current transformer, characterized in that, include: Filter, fiber optic link under test, and detection module; The fiber optic link under test is used to inject a coupling optical signal at the transmitting end so that the coupling optical signal forms a pilot optical signal at the receiving end after being transmitted through the link; the coupling optical signal is obtained by coupling a preset pilot signal and a working optical signal. The filter is used to separate the actual pilot signal from the pilot optical signal; The detection module is used to acquire the actual pilot signal of the fiber optic link under test; The actual health index is obtained by logarithmically normalizing the amplitude ratio of the actual pilot signal to the preset pilot signal. Obtain the baseline health index of the fiber optic link under test; The difference between the actual health index and the baseline health index is used as the health index offset. Statistical analysis is performed on the actual health index to obtain the standard deviation of the health index and the short-term decrease in the health index; based on the health index offset, the standard deviation of the health index, and the short-term decrease in the health index, the fiber status of the fiber link under test is determined.

8. The fiber optic condition detection device for an all-fiber current transformer according to claim 7, characterized in that, The fiber status includes: normal status, chronic degradation trend, abnormal fluctuation or sudden failure; The process of determining the fiber status of the fiber link under test based on the health index offset, health index standard deviation, and short-term health index decline includes: If the health index offset is less than or equal to the preset chronic degradation threshold, the fiber condition of the fiber link under test is determined to be a chronic degradation trend. If the standard deviation of the health index is greater than or equal to the preset abnormal fluctuation threshold, the fiber status of the fiber link under test is determined to be abnormal fluctuation. If the short-term health index decrease is less than or equal to the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be a sudden fault. If the health index offset is greater than the preset chronic degradation threshold, the health index standard deviation is less than the preset abnormal fluctuation threshold, and the short-term health index decrease is greater than the preset sudden fault threshold, the fiber status of the fiber link under test is determined to be normal.

9. The fiber optic condition detection device for an all-fiber current transformer according to claim 8, characterized in that, Also includes: Alarm module; The alarm module includes: a link chronic degradation alarm unit, a link fluctuation abnormality alarm unit, and a link sudden failure alarm unit; The link chronic degradation alarm unit is used to issue a link chronic degradation alarm signal when the fiber condition of the fiber link under test is showing a chronic degradation trend. The link fluctuation anomaly alarm unit is used to issue a link fluctuation anomaly alarm signal when the fiber status of the fiber link under test is fluctuating abnormally. The link burst fault alarm unit is used to issue a link burst fault alarm signal when the optical fiber status of the optical fiber link under test is a sudden fault.

10. The fiber optic condition detection device for an all-fiber current transformer according to claim 7, characterized in that, Also includes: Spectrometer; The coupled optical signal passes through a beam splitter, which adjusts the coupled optical signal according to the fiber type and link length of the fiber link under test, resulting in a split coupled optical signal.

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