Method for identifying model of optical fiber in optical fiber link

Abstract

The invention discloses a method for identifying the type of an optical fiber in an optical fiber link, which comprises the following steps of: injecting a group of high-energy narrow pulse optical signals into an optical fiber to be identified; then, Fresnel reflection signals generated in the optical fiber to be identified are collected, Fourier transform is carried out on the collected data after multiple times of time division multiplexing, and an optical fiber transmission characteristic curve is formed; and finally, finding out each distortion point of the optical fiber link and calculating the loss of each section of optical fiber based on the formed optical fiber transmission characteristic curve. According to the optical fiber model identification scheme provided by the invention, the optical fiber model of each point in the optical fiber link can be effectively identified under the condition of not cutting off the optical fiber by utilizing the transmission characteristics of the Fresnel reflection signal and different optical fiber models based on the OTDR technology.

Description

Technical Field

[0001] The invention relates to optical fiber communication technology, and in particular to an effective optical fiber model identification technology. Background Art

[0002] With the vigorous development of fiber-optic communication technology, optical fiber has been widely used in the communication field. People's demand for network bandwidth is also growing rapidly, and new applications and network services are also developing continuously.

[0003] Therefore, different types of optical fibers are widely used in places with different needs, especially G652 and G655 optical fibers, which are widely used in communication links.

[0004] Among them, G.652 optical fiber, also known as standard single-mode fiber (SMF), has a dispersion zero point near 1310nm. This type of optical fiber was successfully developed in 1980 and began to be commercialized in 1983. G.652 optical fiber is currently the most widely used optical fiber type, and most of the optical fibers and optical cables laid in China are of this type.

[0005] G655 fiber, also known as non-zero dispersion-shifted single-mode fiber, was proposed by ITU-T in 1996 and began to be widely used in 1998. ITU-T revised the G.655 recommendation at the Geneva conference in April 2000. The World Telecommunication Standards Conference (WTSC) held in Montreal, Canada on October 6 adopted the new standard for G.655 fiber.

[0006] In actual applications, due to the segmented construction of the network, the asynchronous improvement of each network, and the irregular operation, G652 and G655 optical fibers are often mixed in actual applications, that is, a communication link contains multiple sections of G652 and G655 optical fibers mixed in use. This problem has a certain impact on data communication and also increases the maintenance cost for subsequent maintenance.

[0007] Therefore, how to accurately analyze which types of optical fibers exist in a fiber optic link and which section is of what type of optical fiber is the problem that needs to be solved at present.

[0008] Currently, fusion splicers and fiber core diameter analyzers can accurately identify the type of optical fiber, but they both require cutting the optical fiber and using the fiber core diameter to determine the type of optical fiber. This method is not advisable for an already built optical fiber link.

[0009] Therefore, how to effectively identify the optical fiber model in the optical fiber network without damaging the optical fiber is an urgent problem to be solved in this field. Summary of the invention

[0010] In view of the problem that the optical fiber model identification scheme in the existing optical fiber network needs to cut the optical fiber, the present invention provides a method for identifying the optical fiber model in an optical fiber link. The identification method is based on OTDR technology and utilizes Fresnel reflection signals. It can effectively determine the optical fiber model of each point in the optical fiber link by analyzing the transmission characteristics of different optical fiber models without cutting the optical fiber.

[0011] In order to achieve the above object, the present invention provides a method for identifying the type of optical fiber in an optical fiber link. The identification method first injects a group of high-energy narrow pulse optical signals into the optical fiber to be identified;

[0012] Then, the Fresnel reflection signal generated in the optical fiber to be identified is collected, and after multiple time division multiplexing, the collected data is Fourier transformed to form an optical fiber transmission characteristic curve;

[0013] Finally, based on the formed optical fiber transmission characteristic curve, the various distortion points of the optical fiber link are found and the loss of each section of optical fiber is calculated.

[0014] In some embodiments of the present invention, the identification method uses a narrow pulse light signal with a wavelength of 1310 nm and / or 1550 nm.

[0015] In some embodiments of the present invention, the identification method, when performing data collection, includes: first, collecting random noise data in the corresponding identification circuit without injecting a narrow pulse optical signal into the optical fiber to be identified;

[0016] Next, when a narrow pulse optical signal is injected into the optical fiber to be identified, the reflected signal data in the optical fiber to be identified is collected;

[0017] Finally, the two sets of collected data are logarithmically processed to form a logarithmic data set.

[0018] In some embodiments of the present invention, when the optical fiber transmission characteristic curve is identified in the method, the distribution distance of each sampling point on the optical fiber is first calculated based on the collected logarithmic data set, and then the optical fiber transmission characteristic curve is constructed based on the calculated distribution distance of each sampling point on the optical fiber.

[0019] In some embodiments of the present invention, a guide optical fiber is further introduced into the identification method, and the model and transmission parameters of each optical fiber segment of the optical fiber link under test are analyzed by comparing the differences between each optical fiber segment to be tested and the guide optical fiber.

[0020] In some embodiments of the present invention, the identification method uses a dual-wavelength unidirectional measurement and analysis method to completely and accurately identify the optical fiber model of the entire optical fiber link.

[0021] The optical fiber model identification method provided by the present invention is based on OTDR technology and utilizes Fresnel reflection signals to effectively identify the optical fiber model of each point in the optical fiber link without cutting the optical fiber under the transmission characteristics of different optical fiber models.

[0022] Furthermore, the optical fiber model identification method provided by the present invention has high accuracy when implemented, and the distance resolution can be accurate to within one meter. As long as it is measured at the machine room end, the optical fiber model of each point of a 100km optical fiber link can be measured at one time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0024] Figure 1 This is a schematic diagram of the structure of the optical fiber model identification device in the present invention;

[0025] Figure 2 It is a schematic diagram of optical signal transmission in the present invention;

[0026] Figure 3 This is a test example diagram of an optical fiber model identification device in an example of the present invention;

[0027] Figure 4 This is an example of a test curve of a 1550nm wavelength and a 100ns pulse measured from A->B in an example of the present invention;

[0028] Figure 5 This is an example of a test curve of a 1310nm wavelength and a 100ns pulse measured from A->B in an example of the present invention;

[0029] Figure 6 This is an example diagram of bidirectional analysis at a wavelength of 1550nm in an example of the present invention;

[0030] Figure 7 This is an example diagram of bidirectional analysis at a wavelength of 1310 nm in an example of the present invention;

[0031] Figure 8 This is an example diagram of one-way measurement analysis of 1310nm wavelength and 1550nm wavelength in the example of the present invention;

[0032] Fig. 9 This is an example diagram of unidirectional reverse direction measurement analysis of 1310nm wavelength and 1550nm wavelength in an example of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0034] To facilitate the description of this solution, the connection method between optical fibers in the optical fiber link is described here.

[0035] There are several ways of connecting and splicing in optical fiber links: the first is fusion splicing; the second is flange butt splicing; and the third is cold splicing.

[0036] Among them, the fusion splicing method is to use a fusion splicer to melt the optical fiber at high temperature, so that the two fusion splicing points are fused together, which can ensure very small mechanical loss.

[0037] Flange connection is usually found in the machine room and optical cross-connect box or secondary splitter and household end.

[0038] The cold connection method is to connect the optical fibers by using matching fluid and a fixing box.

[0039] For the built optical fiber link, in order to identify the optical fiber model and the distribution area of ​​each type of optical fiber included in the optical fiber link without damaging the optical fiber. The optical fiber model identification scheme provided by the present invention is based on the principle of optical time domain reflectometry, by injecting a high-energy narrow pulse optical signal with a wavelength of 1310nm and 1550nm into the optical fiber to be identified, and then using high-speed sampling to sample its Fresnel reflection signal, and after multiple time division multiplexing, the collected data is Fourier transformed to form an optical fiber transmission characteristic curve, and then based on the formed optical fiber transmission characteristic curve, the various distortion points of the optical fiber link are found and the loss of each section of the optical fiber is calculated; finally, by comparing the differences between each section of the optical fiber and the guide optical fiber, the model and transmission parameters of each section of the optical fiber in the optical fiber link under test are analyzed.

[0040] See also Figure 1 In order to implement the above-mentioned optical fiber model identification solution, the present invention provides an optical fiber model identification device.

[0041] Based on the diagram, the optical fiber model identification device 100 is mainly composed of a pulse laser 110, a pulse laser driving module 120, a photoelectric conversion module 130, a TIA amplification module 140, a sampling module 150, a signal processing module 160 and a power management module 170.

[0042] The pulse laser 11 in the present device is configured to generate narrow pulse optical signals of different wavelengths as a measurement signal source.

[0043] Furthermore, the output end of the pulse laser 110 is configured to be connected to one end of the optical fiber 200 to be identified, and the input end is configured to be connected to the pulse laser driving module 120; the pulse laser 110 can transmit the generated high-energy narrow pulse light signal to the optical fiber 200 to be identified.

[0044] The input end of the pulse laser driving module 120 in the device is configured to drive the pulse laser 110, and is used to generate a driving signal to drive the working state of the pulse laser 110, such as starting and shutting down, generating the energy and wavelength of the narrow pulse light signal, etc.

[0045] The input end of the photoelectric conversion module 130 in the present device is configured to be connected to one end of the optical fiber 200 to be identified, and to obtain the Leary scattering and Fresnel reflection signals (i.e., optical signals) generated by the narrow pulse light signal injected by the pulse laser 110 in the optical fiber 200 to be identified and perform photoelectric conversion to convert the received optical signal into a corresponding electrical signal.

[0046] The input end of the TIA amplification module 140 in the present device is configured to be connected to the output end of the photoelectric conversion module 130, and is used to amplify the electrical signal converted by the photoelectric conversion module 130 to ensure the accuracy of subsequent data sampling.

[0047] The input end of the sampling module 150 in the present device is configured to be connected to the output end of the TIA amplification module 140 , so as to sample the electrical signal amplified by the TIA amplification module 140 and transmit the sampled data to the signal processing module 160 .

[0048] The output end of the signal processing module 160 in the present device is configured to be connected to the input end of the pulse laser driving module 120 , while the input end is connected to the output end of the sampling module 150 .

[0049] Furthermore, the signal processing module 160 is also configured to control the pulse laser driving module 120 to drive the pulse laser 110 to inject a high-energy narrow pulse light signal into the optical fiber 200 to be identified; and control the sampling module 150, the TIA amplification module 140 and the optoelectronic conversion module 130 to synchronously sample the Leary scattering and Fresnel reflection signals generated in the optical fiber 200 to be identified, and after multiple time division multiplexing, perform Fourier transform on the collected data to form an optical fiber transmission characteristic curve, and then use the algorithm to find out the various distortion points of the optical fiber link and the loss of each section of the optical fiber.

[0050] The power management module 170 in the device is configured to be electrically connected to the pulse laser 110, the pulse laser driving module 120, the photoelectric conversion module 130, the TIA amplification module 140, the sampling module 150 and the signal processing module 160 to provide a stable working power supply for each functional module unit in the device.

[0051] The following describes in detail the specific implementation scheme and corresponding technical features of the optical fiber model identification device.

[0052] In some embodiments of the present invention, the pulse laser 110 in the identification device is specifically configured to emit a light pulse with a wavelength of 1310 nm and 1550 nm into the optical fiber.

[0053] Furthermore, the pulse lasers 110 may be connected together through a wavelength division multiplexer to form a dual-wavelength laser assembly.

[0054] In some embodiments of the present invention, the pulse laser driving module 120 in the identification device is preferably a laser driving circuit composed of a high-speed MOS tube and a high-speed switching circuit, wherein the high-speed switching circuit is controlled by the signal processing module 160 and can control the state of the pulse laser 110 to emit light pulses.

[0055] In some embodiments of the present invention, the photoelectric conversion module 130 in the identification device is preferably composed of an APD avalanche photodiode, which can perform photoelectric conversion on the received Leary scattered and Fresnel reflected light, and perform signal processing after converting it into an electrical signal.

[0056] In some embodiments of the present invention, the TIA amplification module 140 in the identification device is preferably composed of an AD4817 chip and an ADG904 chip, wherein the AD4817 chip is configured to perform signal amplification, and the ADG904 chip is configured to perform gain switching.

[0057] In some embodiments of the present invention, the sampling module 150 in the recognition device is preferably composed of an analog signal processing module 151 and an ADC acquisition module 152 .

[0058] The input end of the analog signal processing module 151 is configured to be connected to the output end of the TIA amplification module 140 , and the output end is configured to be connected to the input end of the ADC acquisition module 152 .

[0059] Furthermore, the analog signal processing module 151 specifically includes a bandpass filter circuit and a signal amplification circuit that are interconnected and coordinated, wherein the bandpass filter circuit is used to filter the electrical signal flowing through, and the signal amplification circuit is used to amplify the signal filtered by the bandpass filter circuit and convert the single-ended signal into a differential signal.

[0060] The input end of the ADC acquisition module 152 is configured to be connected to the output end of the analog signal processing module 151 , and the output end is configured to be connected to the input end of the signal processing module 160 .

[0061] Furthermore, the ADC acquisition module 152 is specifically composed of an AD9235-65 chip and is configured to be able to convert analog signals into digital signals, so that the FPGA can read the digital signals and then process them.

[0062] As a further illustration, the ADC sampling module is configured to use a speed of 65M. Such an ADC sampling module is also configured to cooperate with the signal processing module 160, and the FPGA in the signal processing module 160 time-division multiplexes it to synthesize the sampling frequency into 800M samples, so that the sampling resolution can reach more than 0.125 meters.

[0063] In some embodiments of the present invention, the signal processing module 160 in the identification device is preferably composed of an embedded CPU mainboard and an FPGA, wherein an ARM processor is preferably provided on the embedded CPU mainboard; the FPGA is further configured to complete the pulse driving of the laser, cooperate with the ADC to complete time division multiplexing sampling, and perform Fourier transform on the collected signal and deliver it to the ARM processor for processing.

[0064] In some embodiments of the present invention, the power management module 170 in the identification device is specifically configured to convert the battery voltage into various power supplies required by the device hardware system; such as +5V, -5V, +60V, +3.3V, etc.

[0065] The following specifically describes an implementation scheme of the optical fiber model identification device provided by the present invention, which identifies the optical fiber models included in an optical fiber link and the distribution area of ​​each optical fiber model without damaging the optical fiber.

[0066] See also Figure 2 The transmission of light in the optical fiber is forward transmission by total reflection. Due to the impurities in the optical fiber, part of the light will be reflected back in the opposite direction, which forms Leary scattering. By collecting and analyzing the Leary scattered light, the transmission status of light in the optical fiber can be analyzed.

[0067] When encountering flange docking, since the two optical fibers are docked through the flange, it is impossible to achieve a 100% tight connection, so there is air in the middle. When light enters from one medium into another, there is Fresnel reflection at the critical point. After the Fresnel reflected light is reflected back, a reflection peak will be formed when it is detected.

[0068] Accordingly, when the optical fiber model identification device is used to identify the optical fiber model in the optical fiber link, the identification end in the device 100 is connected to the optical fiber link 200 to be identified, such as Figure 3 shown.

[0069] On this basis, the signal processing module 160 in the optical fiber model identification device controls the pulse laser driving module 120 to drive the pulse laser 110 to inject a high-energy narrow pulse light signal into one end of the optical fiber 200 to be identified; and controls the sampling module 150, the TIA amplification module 140 and the optoelectronic conversion module 130 to synchronously sample the Fresnel reflection signal generated in the optical fiber 200 to be identified from the same end of the optical fiber 200 to be identified.

[0070] Specifically, the photoelectric conversion module 130 in the optical fiber model identification device first obtains the Fresnel reflected light signal generated in the optical fiber 200 to be identified, and photoelectrically converts it into a corresponding current signal, and transmits it to the TIA amplification module 140 .

[0071] The TIA amplification module 140 then converts the weak current signal generated by the photoelectric conversion module 130 into a voltage signal for subsequent signal processing and analysis.

[0072] The analog signal processing module 151 performs bandpass filtering and signal amplification processing on the voltage signal processed and converted by the TIA amplification module 140, and converts the single-ended signal into a differential signal.

[0073] The ADC acquisition module 152 performs ADC sampling on the signal processed by the analog signal processing module 151 , and transmits the sampled data to the signal processing module 160 for processing.

[0074] To ensure that the signal processing module 160 can effectively and accurately identify the optical fiber model included in the optical fiber link based on the collected data signal, the signal processing module 160 specifically controls the corresponding functional modules in the device to perform data collection according to the following collection scheme:

[0075] Step 1: Sampling data for the first time: Control the pulse laser to turn off, do not send pulse laser, and collect circuit random noise data.

[0076] Specifically, in this step, data collection is performed N times, and each collection forms a corresponding data set:

[0077] The first sampling data set: data.1[A0,A1,A2,…An];

[0078] The second sampling data set: data.2[B0,B1,B2,…Bn];

[0079] …

[0080] The Nth sampling data set: data.n[N0,N1,N2,…Nn];

[0081] Next, the weighted average of the N sampled data is taken to obtain the average value set: Noise[X0,X1,X2,…,Xn];

[0082] X0=(A0+B0+……N0) / N;

[0083] X1=(A1+B1+……N1) / N;

[0084] …

[0085] Xn=(An+Bn+……Nn) / N;

[0086] Since the pulse laser does not emit pulses, X0~Xn can be considered as random circuit noise;

[0087] Step 2: Collect Leary scattering signal.

[0088] The pulse laser is controlled to start and emit a laser signal with a certain pulse width, and the ADC sampling is randomly started to collect the Leary scattering signal generated in the optical fiber to be identified.

[0089] Specifically, in this step, data collection is also performed N times, and each collection forms a corresponding data set:

[0090] The first sampling data set: data.1[A0,A1,A2,…An];

[0091] The second sampling data set: data.2[B0,B1,B2,…Bn];

[0092] …

[0093] The Nth sampling data set: data.n[N0,N1,N2,…Nn].

[0094] Next, the weighted average of the N sampled data is taken to obtain the average value set: AVG[X0,X1,X2,…,Xn];

[0095] X0=(A0+B0+……N0) / N;

[0096] X1=(A1+B1+……N1) / N;

[0097] …

[0098] Xn=(An+Bn+……Nn) / N.

[0099] Step 3: Perform logarithmic calculation on the data set collected in step (1) and the data set collected in step (2) to obtain a logarithmic data set: L[L0, L1, L2...Ln].

[0100] Specifically, the corresponding logarithm is calculated as follows:

[0101] L 0 =10×log(|AVG[0]-Noise[0]|, 10);

[0102] L 1 =10×log(|AVG[1]-Noise[1]|, 10);

[0103] L 2 =10×log(|AVG[2]-Noise[2]|, 10);

[0104] …

[0105] L n =10×log(|AVG[n]-Noise[n]|, 10).

[0106] Step 4: Distance calculation and curve drawing.

[0107] This step first calculates the distribution distance of each sampling point on the optical fiber based on the data set processed in step (3). The specific calculation scheme here is as follows:

[0108] The distance between two sampling points is set to d;

[0109] d=(C 0 / n)×(1 / F) / 2;

[0110] Among them, C 0 is the speed of light in vacuum, and F is the sampling frequency of the device.

[0111] On this basis, the distribution distance of each sampling point on the optical fiber is L n ;

[0112] L n =n×d;

[0113] Where n is the refractive index of the optical fiber.

[0114] Then, a curve is constructed based on the calculated distribution distance of each sampling point on the optical fiber:

[0115] With the distance distribution of each sampling point as the horizontal axis and the dB value L data calculated in the third step as the vertical axis, the spatial distribution curve of the Leary scattering signal in the optical fiber link is depicted, as shown in Figure 4 and Figure 5 shown.

[0116] Step 5: Find the locations of the distortion points on the curve and calculate the average loss between each section.

[0117] Based on the constructed spatial distribution curve of Leary scattering signal in the optical fiber link, the short-time Fourier transform and wavelet transform algorithms are further used to find the positions of various distortion points on the curve and calculate the average loss between each section.

[0118] Specifically, the time domain signal is converted into a frequency domain signal through short-time Fourier transform, thereby clearly showing the distortion point in the frequency domain, and then the position of the distortion point is found and located through the wavelet transform algorithm.

[0119] Step 6: Identify the fiber model.

[0120] On the basis of the above identification scheme, the guide optical fiber 300 is further introduced as a reference standard in this step, and the model and transmission parameters of each optical fiber segment of the optical fiber link under test are analyzed by comparing the differences between each optical fiber segment and the guide optical fiber.

[0121] Specifically, the guide optical fiber 300 is arranged between the optical fiber model identification device 100 and the optical fiber 200 under test, that is, one end of the guide optical fiber 300 is connected to the optical fiber model identification device 100, and the other end is connected to one end of the optical fiber 200 under test.

[0122] Preferably, in the solution of the present invention, a section of G652 optical fiber is used as a guide optical fiber as a reference standard, and is connected to the optical fiber under test through a flange.

[0123] In this way, based on the introduced guide optical fiber 300 as a reference standard, the positions of the various distortion points on the curve found in step five and the characteristics of the distortion points are used as segmentation points of the optical fiber. The attenuation characteristics of each segment are compared with the spatial distribution curve formed by the guide optical fiber 300, thereby distinguishing the optical fiber type at each end.

[0124] In this way, when the optical fiber model in the optical fiber link is identified based on the optical fiber model identification device 100, a laser pulse light signal is injected into the guide optical fiber 300 through the optical fiber model identification device 100, and the laser pulse light signal is then transmitted to the optical fiber 200 under test via the guide optical fiber 300. In this way, the optical fiber model identification device 100 can collect the Fresnel reflection signals generated by the guide optical fiber 300 and the optical fiber 200 under test, and on this basis, form a corresponding spatial distribution curve, and then compare the differences in the spatial distribution curves formed by the tested sections of the optical fiber 200 and the guide optical fiber 300, so as to analyze the models and transmission parameters of each section of the optical fiber in the tested optical fiber link.

[0125] As a further illustration, the present invention further preferably adopts a dual-wavelength unidirectional analysis method to completely and accurately identify the optical fiber model of the entire optical fiber link.

[0126] Specifically, first, two test narrow pulse optical signals of different wavelengths are formed by the optical fiber model identification device, and are respectively injected into the same end of the optical fiber 200 to be identified; then, based on the above identification scheme, the two different wavelengths are tested once respectively; finally, the test results of the two different wavelengths are compared and analyzed to finally determine the optical fiber model of the entire optical fiber link.

[0127] The implementation process of the solution of the present invention is further illustrated below through specific application examples.

[0128] like Figure 3 As shown, the entire optical fiber link in this example is: standard fiber G652: 985 meters + G652: 1031 meters + G655: 1001 meters + G652: 322 meters.

[0129] The respective connection points: a: flange butt connection; b: fusion connection; c: flange butt connection; d: optical fiber end.

[0130] The above fiber link simulates all situations where G652 fiber and G655 fiber are mixed:

[0131] 1) G652 optical fiber is fusion spliced ​​to G655 optical fiber;

[0132] 2) G652 fiber optic flange is connected to G655 fiber optic;

[0133] 3) G655 optical fiber is fusion spliced ​​to G652 optical fiber;

[0134] 4) G655 optical fiber flange is connected to G652 optical fiber.

[0135] For this optical fiber link, a section of G652 optical fiber is used as a guide optical fiber 300 as a reference standard, and the guide optical fiber 300 is connected through the optical fiber model identification device 100, and then the guide optical fiber 300 is connected to one end of the optical fiber link 200. After such connection and deployment, the optical fiber model identification device injects a high-energy narrow pulse optical signal; and synchronously collects and processes the Fresnel reflection signal generated in the optical fiber link, which can depict the spatial distribution curve of the Leary scattering signal in the optical fiber link, find the positions of each distortion point on the curve, and calculate the average loss between each section.

[0136] Since an optical cable has two ends AB, there are differences in the directionality of light from A to B and from B to A. The connection between two different optical fibers exhibits different characteristics for the direction of light, and different wavelengths exhibit different characteristics. In combination with various situations, this example uses a single-wavelength bidirectional analysis method and a dual-wavelength unidirectional analysis method respectively.

[0137] 1) 1550nm single wavelength bidirectional analysis method:

[0138] In this example, for the convenience of curve comparison, the guide optical fiber is not considered in this mode.

[0139] Using the optical fiber model identification device 100, a 1550nm 100ns pulse laser is injected from the A end of the optical cable 200 to test the curve m, and then a 1550nm 100ns pulse laser is injected from the B end of the optical cable in the same way to test the curve n; then two corresponding curves are drawn based on this, as shown in FIG. Figure 6 shown.

[0140] based on Figure 6 By comparing the two curves shown, we can conclude that:

[0141] The characteristics of the G652 fiber segment are very similar, and no difference can be seen. However, in the G655 fiber segment, the same fusion splice and flange splice points show different phenomena. When measured from end A to end B, the flange splice loss at point a1 is much smaller than the flange splice loss measured from end B to end A. At the same time, there is a big difference at the fusion splice point a2.

[0142] There is almost no loss when measuring from end A to end B, but there is a relatively obvious loss point when measuring from end B to end A. In the pulse injection direction, if the G652 fiber is in the front and the G655 fiber is in the back, the G655 fiber segment will be the same as or slightly higher than the G652 fiber segment.

[0143] 2) 1310nm single wavelength bidirectional analysis method:

[0144] In this example, for the convenience of curve comparison, the guide optical fiber is not considered in this mode.

[0145] Using the optical fiber model identification device 100, a 100ns pulse laser of 1310nm is injected from the A end of the optical cable 200 to test the curve m; then a 100ns pulse laser of 1310nm is injected from the B end of the optical cable in the same way to test the curve n; and then two corresponding curves are drawn accordingly, as shown in FIG. Figure 7 shown.

[0146] based on Figure 7 By comparing the two 1310nm test curves shown, we can conclude that:

[0147] For the fusion splicing points and flange butt splicing points in the optical cable, the G655 fiber segment must be higher than the front and rear G652 fiber segments. If the G652 fiber segment is in the front, the G655 fiber segment is one step higher. If the G655 fiber segment is in the front and the G652 fiber segment is in the back, a very large loss attenuation point will be formed. The loss of this attenuation point is much greater than the conventional fusion loss and flange butt loss.

[0148] 3) 1550nm and 1310nm dual wavelength unidirectional analysis method:

[0149] A guide fiber 300 is made of G652 fiber between the fiber model identification device 100 and the fiber under test 200, and then a 100ns pulse laser with a wavelength of 1550nm and 1310nm is injected from end A->end B twice, respectively, to obtain two Leary scattering curves, such as Figure 8 shown.

[0150] based on Figure 8 As shown in the figure, the test curve corresponding to the 1550nm wave is almost the same as that of the optical fiber link of the same model; while the test curve corresponding to the 1310nm wavelength has obvious differences at positions a1 and a2. Between these two points is the G655 optical fiber. Going forward, G655 is obviously higher than the front end. Going backward, there is a large loss in the G652 and G655 sections, and the loss shown at 1310nm is much greater than the loss at 1550nm.

[0151] In order to verify the dual-wavelength unidirectional feature, this example further injects 100ns pulse lasers of 1310 and 1550nm from end B->end A, and also forms Leary scattering curves, such as Fig. 9 shown.

[0152] based on Fig. 9 As shown, the test curve formed by measuring from end B -> end A has the same phenomenon as the test curve formed by measuring from end A -> end B.

[0153] From the above test results, we can see that the wavelength of the pulsed laser used for measurement has the following influence on the measurement results:

[0154] (1) When the 1550nm wavelength is used as the measurement wavelength, the direction of light enters the G655 fiber from the G652 fiber, and no obvious features can be seen. However, when the light enters the G652 fiber from the G655 fiber, a loss point is formed.

[0155] (2) When the 1310nm wavelength is used as the measurement wavelength, the direction of light from the G652 fiber to the G655 fiber will form a relatively obvious pseudo loss of the rising step. However, when the light enters the G652 fiber from the G655 fiber, a loss slightly smaller than 1550nm will be formed.

[0156] The impact of different measurement and analysis methods on measurement results:

[0157] (1) It is difficult to compare the differences between the G655 and G652 ends using the 1550nm single wavelength bidirectional analysis method. The biggest difference is that when G655 is at the back, light enters G655 from G652, and no difference can be seen. When G655 is at the front, light enters G652 from G655, forming a downward step (loss point), which is also in line with the actual optical path connection situation. Therefore, using the 1550nm single wavelength bidirectional analysis method will have a certain misjudgment rate, and bidirectional testing is required, which is a large measurement workload.

[0158] (2) 1310nm single wavelength bidirectional analysis method: no matter which direction is measured, the G655 segment will form an upward step (pseudo loss) at the connection of the G652 segment. Therefore, the 1310nm single wavelength bidirectional analysis method can be used to determine the difference between the fiber model and the standard fiber model, and can determine the fiber model of each segment in the fiber line. This measurement and analysis method has high accuracy and can make full use of the characteristics of G655 in the 1310nm window, but it requires bidirectional testing and has a large measurement workload.

[0159] (3) 1550nm / 1310nm dual-wavelength unidirectional analysis method. This method uses the difference in transmission characteristics of G652 and G655 in these two wavelength windows. G655 is at the back end of G652. There is no abnormality in the 1550nm wavelength, but there is an abnormality in the 1310nm wavelength. G655 is at the front end of G652. The G652 at the back end of G655 will have a relatively large attenuation, and the slope will be larger than that of G652 and G655. Therefore, by using this measurement and analysis method, as long as one end uses two wavelengths for testing once, the fiber model of the entire link can be accurately determined. The accuracy is high and the measurement workload is small.

[0160] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for identifying optical fiber type in an optical fiber link, characterized in that: The identification method firstly injects a group of high-energy narrow pulse optical signals into the optical fiber to be identified; Then, the Fresnel reflection signal generated in the optical fiber to be identified is collected, and after multiple time division multiplexing, the collected data is Fourier transformed to form an optical fiber transmission characteristic curve; Finally, based on the formed optical fiber transmission characteristic curve, the various distortion points of the optical fiber link are found and the loss of each section of optical fiber is calculated.

2. The method for identifying optical fiber type in an optical fiber link according to claim 1, characterized in that: The identification method adopts a narrow pulse optical signal with a wavelength of 1310nm and / or 1550nm.

3. The method for identifying optical fiber type in an optical fiber link according to claim 1, characterized in that: The identification method includes the following steps when performing data collection: first, collecting random noise data in a corresponding identification circuit without injecting a narrow pulse optical signal into the optical fiber to be identified; Next, when a narrow pulse optical signal is injected into the optical fiber to be identified, the reflected signal data in the optical fiber to be identified is collected; Finally, the two sets of collected data are logarithmically processed to form a logarithmic data set.

4. The method for identifying optical fiber type in an optical fiber link according to claim 3, characterized in that: In the identification method, when the optical fiber transmission characteristic curve is obtained, the distribution distance of each sampling point on the optical fiber is first calculated based on the collected logarithmic data set, and then the optical fiber transmission characteristic curve is constructed based on the calculated distribution distance of each sampling point on the optical fiber.

5. The method for identifying optical fiber type in an optical fiber link according to claim 1, characterized in that: The identification method also introduces a guide optical fiber, and by comparing the differences between each section of optical fiber to be tested and the guide optical fiber, the model and transmission parameters of each section of optical fiber in the optical fiber link to be tested are analyzed.

6. The method for identifying optical fiber type in an optical fiber link according to claim 5, characterized in that: The identification method adopts a dual-wavelength unidirectional measurement and analysis method to completely and accurately identify the optical fiber model of the entire optical fiber link.

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