WO2019056634A1

WO2019056634A1 - Online optical time domain reflectometer structure, detection system, and detection method

Info

Publication number: WO2019056634A1
Application number: PCT/CN2017/118232
Authority: WO
Inventors: 叶知隽; 熊涛; 余春平; 徐红春; 余振宇; 张建涛
Original assignee: 武汉光迅科技股份有限公司
Priority date: 2017-09-25
Filing date: 2017-12-25
Publication date: 2019-03-28
Also published as: CN107483106A; CN107483106B

Abstract

An online optical time domain reflectometer (OTDR) structure, a detection system, and a detection method. In the structure, a light outlet of a narrow-linewidth pulsed laser (101) is connected to a first light inlet (1) of a circulator (102); a second light inlet/outlet (2) of the circulator (102) is used for connecting to an external optical fiber to be detected; a third light outlet (3) of the circulator (102) is connected to an optical filter (103); the optical filter (103) is connected in series between the third light outlet (3) of the circulator (102) and an optical detector (104); a signal output port of the optical detector (104) is connected to a processor (105); the processor (105) is further connected to the narrow-linewidth pulsed laser (101) so as to provide a driving signal for the narrow-linewidth pulsed laser (101). The narrow-linewidth pulsed laser (101) and the optical filter (104) are chosen to be used together, such that only narrowband spectra in a pulsed light wavelength range can be acquired by the optical detector (104) so that the dynamic range and measuring range of the OTDR itself are improved, and furthermore most of reverse ASE in an EDFA system can be filtered so that the dynamic range during online monitoring is improved.

Description

Online optical time domain reflectometer structure, detection system and detection method

[Technical Field]

The invention relates to the technical field of optical fiber detection, in particular to an online optical time domain reflectometer structure, a detection system and a detection method.

【Background technique】

The Optical Time Domain Reflectometer (OTDR) is an important test instrument in optical fiber communication systems. The optical transmission module of the OTDR transmits a set optical pulse signal according to the backward Fresnel reflection and Rayleigh. The principle of scattering, the reflected light signal is converted by the light receiving module (including Avalanche Photodiode (APD)), and then processed and analyzed by the signal processing unit to obtain parameters such as the average loss of the measured fiber. It can measure the actual length and average loss of the fiber in the fiber-optic communication system, and can detect, locate and measure many types of events on the fiber link, such as the loss of fiber fusion, connectors, bending, etc. in the link. point.

Dynamic range is a very important parameter of OTDR, which is usually used to classify the performance of OTDR. The dynamic range is defined as the difference between the initial level and the noise level on the backscatter curve and is the maximum attenuation value (in dB) of the backscatter curve that can be tested. The dynamic range indicates the maximum fiber loss information that can be measured, directly determining the longest fiber distance that can be measured. The dynamic range is usually calculated using the difference between the start level and the noise rms level on the backscatter curve (signal to noise ratio = 1).

In fiber-optic communication, the Erbium Doped Fiber Application Amplifier (EDFA) system used a 1510 nm light source to check the loss of the fiber link. The EDFA integrates or configures the input and output terminals SIN and SOUT of the 1510 nm light source in the system. The pass light wavelength range is 1500 to 1520 nm). With a 1510 nm light source, it is usually only possible to determine whether the entire fiber link is too worn or unreasonable by power variation, and it is impossible to know the type and location of the fault. The OTDR is widely used in optical fiber communication systems because it can locate the cause and exact location of the fault point.

Improving the dynamic range and detection accuracy of OTDR has always been the subject of research by researchers around the world. Through the improvement of optical paths, detection circuits and algorithms, the performance of OTDR has been improving:

In 2004, Huawei patented the optical signal and optical time domain reflectometer and optical fiber test method of the optical time domain reflectometer. By improving the OTDR receiving circuit, the returned optical signal was divided by using different amplification gears of the amplifier. The segment is amplified without changing the magnitude of the probe optical power, which improves the dynamic range of the OTDR.

In 2011, Yokogawa Corporation of Japan designed a bidirectional OTDR module in the patent "Bidirectional optical module and optical time domain reflectometer equipped with the bidirectional optical module": the laser and the receiver are designed in the same module, in front of the receiver. Use lens focusing and pinhole filtering to improve the accuracy of optical power measurement and reflection point positioning.

In 2015, Changzhou Development Co., Ltd. used the 1550nm laser in the patent "Multi-Function FTTH Special OTDR Tester" to coat the APD or add a lens to filter out light outside 1550nm, making the range reach 50km.

In 2017, EXFO provided an OTDR algorithm and device for detecting one or more events in a fiber link in the patent "Multiple-acquisition OTDR Method and Device". Through multiple optical acquisitions, test light pulses of different pulse widths or wavelengths are propagated in the optical link, and corresponding return optical signals from the fiber link are detected to determine the number and location of events.

With the rapid development of optical fiber communication networks, how to efficiently and flexibly detect and maintain optical fiber networks is a huge challenge for operators. The traditional external OTDR module is expensive and bulky, and needs to disconnect the optical fiber from the system before the detection to analyze the fault or breakpoint position. The fiber link cannot be detected in real time, which affects the normal transmission of service light.

The application of the online OTDR module has just started in 2016, and system vendors generally attach importance to the testing and promotion of online products. The entire market is in the early stages of growth. On-the-spot OTDR can be used for on-site laying and post-maintenance of long-distance fiber-optic communication systems. On the other hand, online monitoring of fiber-optic communication networks can quickly and accurately determine the location of fiber fault points and ensure normal communication of the system. On-line monitoring requires the OTDR to be installed in an optical communication system rack in the form of an optical module. The application can realize real-time monitoring in the system, that is, it can be integrated into the existing system without interfering with or being disturbed by other components. After the evolution of the actual effects and application methods of the OTDR trial in 2016, the market gradually accepted OTDR as the optimal solution for fiber link monitoring.

There are additional requirements for OTDR performance in real-time system monitoring applications in the system. Conventional techniques can be severely degraded here because in the EDFA system, the reverse ASE generated by the link enters the OTDR, affecting the detection of the APD, resulting in a dynamic range degradation of more than 10 dB, and the maximum fiber distance that the OTDR can detect is shortened.

[Summary of the Invention]

The technical problem to be solved by the present invention is that in the system in real time, in the system monitoring application, there is an additional requirement for the performance of the OTDR, and the conventional technology may be seriously deteriorated here because the reverse of the link generation in the EDFA system. The ASE enters the OTDR and affects the detection of the APD, resulting in a dynamic range of more than 10 dB, and the maximum fiber distance that the OTDR can detect is shortened.

The invention adopts the following technical solutions:

In a first aspect, the present invention provides an online optical time domain reflectometer structure comprising a narrow linewidth pulsed laser, a circulator, an optical filter, a photodetector and a processor, specifically:

The light exit of the narrow linewidth pulsed laser is connected to the first light inlet of the circulator, and the second inlet/outlet of the circulator is used for connecting the external fiber to be tested; wherein the center wavelength of the narrow linewidth pulse laser includes 1480 ~ 1520nm and 1610 ~ 1630nm, and the 20dB bandwidth of the narrow line width pulse is less than or equal to 6nm, the narrow line width pulse pulse width includes 5 ~ 20000ns;

a third light exit port of the circulator is connected to the optical filter, and the optical filter is connected in series between the third light exit port of the circulator and the photodetector;

The signal output port of the photodetector is coupled to the processor, and the processor is further coupled to a narrow linewidth pulsed laser to provide a drive signal for the narrow linewidth pulsed laser.

Preferably, the optical filter is specifically a narrow linewidth filter having a 30 dB bandwidth of less than or equal to 6 nm.

Preferably, the center wavelength of the narrow linewidth pulse laser is specifically 1502 nm, and the 20 dB bandwidth of the narrow line width pulse is less than or equal to 6 nm, and the pulse width is comprehensively set according to the length of the optical path to be detected and the event resolution; wherein the pulse width is The smaller the smaller, the stronger the ability to resolve adjacent events; the larger the pulse width, the longer the distance of the optical path that can be detected.

Preferably, the center wavelength of the narrow linewidth pulsed laser is specifically 1625 nm, and the 20 dB bandwidth of the narrow linewidth pulse is less than or equal to 6 nm, and the pulse width is comprehensively set according to the length of the optical path to be detected and the event resolution; wherein the pulse width is The smaller the smaller, the stronger the ability to resolve adjacent events; the larger the pulse width, the longer the distance of the optical path that can be detected.

In a second aspect, the present invention provides an online optical time domain reflection detecting system, comprising the optical time domain reflectometer, the transmitted optical signal, the wavelength division multiplexer, and the optical fiber network to be tested, according to the first aspect, wherein The fiber network to be tested includes one or more network nodes, specifically:

The transmission optical signal is connected to a first input port of the wavelength division multiplexer, the second input/output port of the wavelength division multiplexer is connected to the optical fiber network to be tested, and the third input/output of the wavelength division multiplexer a port connected to the optical time domain reflectometer;

The optical fiber network to be tested is composed of one or more optical fiber links, and each of the optical fiber links is connected by a connector, and the connector is configured to form a partial reflection on a narrow linewidth pulse detection signal of the optical time domain reflectometer; Wherein, the narrow linewidth pulse detection signal transmits backscattering in the optical fiber, and the fiber end face or the fiber cross section forms a strong reflection on the narrow linewidth pulse detection signal.

Preferably, the processor is further configured to record the intensity and time of receiving the portion of the backscattered light and the reflected light: determining the physical state of the point according to the light intensity, and calculating the distance of the point according to the time returned to the processor, In order to depict the fiber length and attenuation profile.

In a third aspect, the present invention also provides an online optical time domain reflection detection system, including a narrow linewidth pulse laser, a circulator, a photodetector, a processor, a transmission optical signal, a wavelength division multiplexer, and an optical filter. And the optical fiber network to be tested, wherein the optical fiber network to be tested includes one or more network nodes, specifically:

The transmission optical signal is connected to a first input port of the wavelength division multiplexer, the second input/output port of the wavelength division multiplexer is connected to the optical fiber network to be tested, and the third input/output of the wavelength division multiplexer a port connecting the second inlet/outlet of the circulator;

The light exit of the narrow linewidth pulsed laser is connected to the first light entrance of the circulator, and the third light exit of the circulator is connected between the light detectors; wherein the center wavelength of the narrow linewidth pulse laser comprises 1480-1520 nm And 1610 ~ 1630nm, and the 20dB bandwidth of the narrow line width pulse is less than or equal to 6nm, the narrow line width pulse pulse width includes 5 ~ 20000ns;

a signal output port of the photodetector is connected to the processor, and the processor is further connected to a narrow linewidth pulse laser to provide a driving signal for the narrow linewidth pulsed laser;

Preferably, the processor is further configured to record the intensity and time of receiving the portion of the backscattered light and the reflected light: determining a physical state of the point according to the light intensity, and calculating the point according to a time returned to the processor Distance to plot the fiber length and attenuation profile.

In a fourth aspect, the present invention further provides an online optical time domain reflectometer using the online optical time domain reflectometer according to the first aspect, comprising:

A narrow linewidth pulsed laser emits narrow linewidth pulsed light driven by a processor;

The narrow linewidth pulsed light passes through the first inlet port and the second inlet/outlet port of the circulator to enter the fiber to be tested;

The narrow linewidth pulsed light generates backscattered light and/or reflected light when encountering network nodes, breakpoints and/or deformation points during transmission in the optical fiber;

Backscattered light and/or reflected light corresponding to narrow linewidth pulsed light and normal data signal light, transmitted together with the reverse ASE light generated by the data signal through the second inlet/outlet port and the third inlet port of the circulator Channel, the reverse ASE light outside the filtering bandwidth is filtered by the optical filter, and the backscattered light and/or the reflected light of the reverse ASE light and the narrow linewidth pulsed light within the remaining filtering bandwidth are collected by the photodetector;

The signal converted by the photodetector is analyzed and processed by the processor.

Compared with the prior art, the beneficial effects of the present invention are:

The invention selects a pulse laser with a specific wavelength to make the working wavelength of the OTDR different from the service optical signal, and the monitoring of the OTDR does not affect the normal operation of the optical network; further, by selecting a narrow linewidth pulse laser and an optical filter, only the pulse is used. The narrow-band spectrum of the optical wavelength range can be captured by the photodetector, which improves the dynamic range and range of the OTDR itself, and filters out most of the reverse ASE in the EDFA system, improving the dynamic range during online monitoring.

[Description of the Drawings]

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

1 is a schematic structural diagram of an online optical time domain reflectometer according to an embodiment of the present invention;

2 is a schematic diagram of a narrow linewidth pulse signal of a narrow linewidth pulse laser according to an embodiment of the present invention;

3 is a schematic diagram of performance parameters of a filter according to an embodiment of the present invention;

4 is a backscattering curve diagram of a 1502 nm OTDR when an OTN is used to monitor an EDFA off pump according to an embodiment of the present invention;

FIG. 5 is a backscattering curve diagram of a 1502 nm OTDR when an OTN online monitoring EDFA is turned on according to an embodiment of the present invention; FIG.

6 is a backscattering curve diagram of a 1625 nm OTDR when an OTN is used to monitor an EDFA off pump according to an embodiment of the present invention;

7 is a backscattering curve diagram of a 1625 nm OTDR when an OTN online monitoring EDFA is turned on according to an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of an online optical time domain reflection detecting system according to an embodiment of the present invention; FIG.

FIG. 9 is a schematic structural diagram of another online optical time domain reflection detecting system according to an embodiment of the present invention; FIG.

FIG. 10 is a schematic flowchart of an online optical time domain reflection detecting method according to an embodiment of the present invention.

【Detailed ways】

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the description of the present invention, the orientations or positional relationships of the terms "inner", "outer", "longitudinal", "transverse", "upper", "lower", "top", "bottom", etc. are based on the drawings. The orientation or positional relationship shown is for the purpose of describing the present invention and is not intended to be a limitation of the invention.

In various embodiments of the present invention, the symbol "/" means a meaning having two functions at the same time, for example, "second in/out port" indicates that the port can enter or exit light. The symbol "A and / or B" indicates that the combination between the front and back objects connected by the symbol includes "A", "B", "A and B", such as "backscattered light and / or Reflected light indicates that it can express either "backscattered light", "reflected light" alone, and "backscattered light and reflected light".

Further, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not constitute a conflict with each other.

Example 1:

Embodiment 1 of the present invention provides an online optical time domain reflectometer structure 1, as shown in FIG. 1, including a narrow linewidth pulse laser 101, a circulator 102, an optical filter 103, a photodetector 104, and a processor 105. ,specific:

The light exit of the narrow linewidth pulsed laser 101 is connected to the first light inlet of the circulator (the corresponding port labeled 1 in the circulator 102 in FIG. 1), and the second inlet/outlet of the circulator 102 (FIG. 1) The corresponding port labeled 2 in the circulator 102 is used to connect the external fiber to be tested; wherein the center wavelength of the narrow linewidth pulse laser 101 includes 1480 to 1520 nm and 1610 to 1630 nm, and the narrow line width pulse is 20 dB. The bandwidth is less than or equal to 6 nm, and the narrow line width pulse width includes 5 to 20000 ns (as shown in FIG. 2, wherein the width of Δλ is less than or equal to 6 nm);

Wherein, when selecting the center wavelength of the narrow linewidth pulsed laser 101, in addition to taking into consideration the conventional data signal use band, for example, C30 band 1530nm-1565nm, L band 1565nm-1625nm, usually avoiding some Bands that are formulated for special purposes, such as 1490nm and 1510nm for the conventional Optical Supervising Channel (OSC), are usually excluded from the selection of the center wavelength of the narrow linewidth pulsed laser 101. other than. Wherein, since the cutoff wavelength actually used in the L-band is sometimes only 1605 nm, the 1610-1630 nm selected in the embodiment of the present invention can be applied; if the cutoff wavelength of the L-band reaches 1625 nm, the OTDR of 1626-1630 nm can be selected, or the 1480-1520 nm can be directly used. The OTDR goes to monitor the L-band. In addition, the conventional optical monitoring channel can usually only determine whether the entire fiber link is excessively worn or unreasonable through power variation, and cannot know the type and location of the fault. The monitoring wavelength written by the ITU standard is 1510 nm, and 1490 nm is an alternative.

The third light exit port of the circulator 102 (the corresponding port labeled 3 in the circulator 102 in FIG. 1) is connected to the optical filter 103, and the optical filter 103 is connected in series to the third of the circulator 102. Between the light exit port and the photodetector 104;

The signal output port of the photodetector 104 is connected to the processor 105. The processor 105 is also connected to the narrow linewidth pulsed laser 101 to provide a driving signal for the narrow linewidth pulsed laser 101.

In the embodiment of the present invention, a pulse laser of a specific wavelength is selected such that the working wavelength of the OTDR is different from the service optical signal (also referred to as data signal light), and the monitoring of the OTDR does not affect the normal operation of the optical network; further, by selecting a narrow line Wide-pulse lasers and optical filters (for example, Wavelength Division Multiplexing (WDM)) are used together. Only the narrow-band spectrum of the pulsed light wavelength range can be collected by the photodetector, which improves the dynamics of the OTDR itself. Range (dynamic range above 36dB) and range (range up to 260km), and can filter out most of the reverse ASE in EDFA system (taking 20dBm output amplifier as an example, after 125km fiber, the ASE power generated at 1480~1520nm is -38.72dBm. Using a 1502nm filtered wavelength division multiplexer WDM (transmitting light in a 1502nm bandwidth while reflecting other light), the power drops to -52.11dBm in the range of 1480 to 1520nm), improving on-line monitoring. Dynamic Range.

In the embodiment of the present invention, the optical filter 103 is specifically a narrow linewidth filter with a 30 dB bandwidth of less than or equal to 6 nm. As shown in FIG. 3, the length of Δλ shown in the figure is less than or equal to 6 nm, and, in an optimal implementation, the center wavelength λ of the filter window of the optical filter coincides with the center wavelength of the narrow linewidth pulse laser. Wherein, 6 nm is the most interval value obtained by testing in the embodiment of the present invention, and in the actual implementation process, considering the device fabrication difficulty and the processing cost, the value of the 30 dB bandwidth is increased by appropriately losing the filtering effect. Selected implementations should also be attributed to equivalents under the common idea of the present invention. In the above narrow linewidth filter parameter setting conditions are small, the reverse ASE optical power entering the APD is reduced, and the detection performance of the APD is improved.

In the embodiment of the present invention, the center wavelengths of two typical narrow linewidth pulsed lasers 101 are also provided, and the corresponding experimental result data is given.

Case 1:

The center wavelength of the narrow linewidth pulsed laser 101 is specifically 1502 nm, and the 20 dB bandwidth of the narrow linewidth pulse is less than or equal to 6 nm, wherein the total length of the fiber reaches 125 km and the pulse width is set to 20000 ns. The pulse width is comprehensively set according to the length of the optical path to be detected and the resolution of the event; wherein the smaller the pulse width, the stronger the ability to distinguish adjacent events; the larger the pulse width, the longer the distance of the optical path that can be detected.

As shown in FIG. 4, when the EDFA is not working, the dynamic range of the 1502 nm OTDR is 37.58 dB, where the dynamic range is the range of the initial light attenuation intensity to the interval when the noise shown in FIG. 4 is generated; as shown in FIG. When the EDFA is operating, the dynamic range of the 1502nm OTDR deteriorates to 34.98dB. The OTDR instrument proposed by the embodiment of the present invention is only used when the OTN online monitoring is degraded by 2.60 dB (calculated by 37.58 dB-34.98 dB).

Case 2:

The center wavelength of the narrow linewidth pulsed laser 101 is specifically 1625 nm, and the 20 dB bandwidth of the narrow linewidth pulse is less than or equal to 6 nm, wherein the total length of the fiber reaches 125 km, and the pulse width is set to 20000 ns. The pulse width is comprehensively set according to the length of the optical path to be detected and the resolution of the event; wherein the smaller the pulse width, the stronger the ability to distinguish adjacent events; the larger the pulse width, the longer the distance of the optical path that can be detected.

As shown in Figure 6, when the EDFA is not operating, the dynamic range of the 1625nm OTDR is 36.00dB; as shown in Figure 7, when the EDFA is operating, the dynamic range of the 1625nm OTDR is degraded to 30.50dB. Through the OTDR instrument proposed in the embodiment of the present invention, the dynamic range is only degraded by 5.50 dB when applied to OTN online monitoring.

Example 2:

In the first embodiment of the present invention, an on-line optical time domain reflectometry system is provided. The embodiment of the present invention further provides an online optical time domain reflectance detecting system, which is used in the embodiment. The optical time domain reflectometer 100, as shown in FIG. 8, additionally includes a transmission optical signal 201, a wavelength division multiplexer 202, and an optical fiber network 203 to be tested, wherein the optical fiber network to be tested is composed of one or more optical fibers. The link consists of each fiber link connected through a connector. There may be fusion points, bends, breaks or mechanical joints in the fiber. Specifically:

The transmission optical signal 201 is connected to a first input port of the wavelength division multiplexer 202, and the second input/output port of the wavelength division multiplexer 202 is connected to the optical fiber network 203 to be tested, and the wavelength division multiplexer 202 a third input/output port connected to the optical time domain reflectometer;

Since the present invention adopts the online optical time domain reflectometer as described in Embodiment 1, the embodiment of the present invention also selects a pulse laser of a specific wavelength to make the operating wavelength of the OTDR different from the service optical signal, and the monitoring of the OTDR. It does not affect the normal operation of the optical network; further, by selecting a narrow linewidth pulsed laser and an optical filter, only the narrowband spectrum of the pulsed light wavelength range can be collected by the photodetector, which improves the dynamic range and range of the OTDR itself. It also filters out most of the reverse ASE in the EDFA system, improving the dynamic range of online monitoring.

In the embodiment of the present invention, the processor 105 is further configured to record the light intensity and time of receiving the portion of the backscattered light and the reflected light: determining the physical state of the point according to the light intensity, and calculating the time according to the time returned to the processor The distance of the points to plot the fiber length and attenuation profile. The corresponding attenuation distribution curve can be referred to FIG. 4 to FIG. 7 , and details are not described herein again.

Example 3:

In the embodiment of the present invention, an on-line optical time domain reflectance detection system is also provided. Compared with the online optical time domain reflectance detector OTDR described in the first embodiment, the embodiment of the present invention will The position of the optical filter in Embodiment 1 is adjusted, extracted from the OTDR 100, and disposed between the wavelength division multiplexer 202 and the OTDR 100, as shown in FIG. 9, including a narrow linewidth pulse laser 101, The circulator 102, the photodetector 104, the processor 105, the transmitted optical signal 201, the wavelength division multiplexer 202, the optical filter 103, and the optical fiber network 203 to be tested, wherein the optical fiber network to be tested includes one or more network nodes ,specific:

The transmission optical signal 201 is connected to a first input port of the wavelength division multiplexer 202, and the second input/output port of the wavelength division multiplexer 202 is connected to the optical fiber network 203 to be tested, and the wavelength division multiplexer 202 a third input/output port is connected to the second inlet/exit port of the circulator 102;

For example, the 1550/λ wavelength division multiplexer 202 is used, which is characterized by transmitting light of 1528 to 1568 nm and reflecting light of wavelength λ (center wavelength selected by the OTDR). The first input port and the second input/output port of the wavelength division multiplexer 202 pass light from 1528 to 1568 nm, and the first input port and the third input/output port pass the light of the center wavelength λ selected by the OTDR.

The light exit of the narrow linewidth pulsed laser 101 is connected to the first light entrance of the circulator 102, and the third light exit of the circulator 102 is connected between the photodetectors 104; wherein the center of the narrow linewidth pulsed laser 101 The wavelength includes 1480 to 1520 nm and 1610 to 1630 nm, and the 20 dB bandwidth of the narrow line width pulse is less than or equal to 6 nm, and the narrow line width pulse width includes 5 to 20000 ns;

The signal output port of the photodetector 104 is connected to the processor 105, and the processor 105 is further connected to the narrow linewidth pulse laser 101 to provide a driving signal for the narrow linewidth pulse laser 101;

Since the present invention adopts the online optical time domain reflectometer structure similar to that described in Embodiment 1, the embodiment of the present invention also selects a pulse laser of a specific wavelength, so that the operating wavelength of the OTDR is different from the service optical signal, and the OTDR is Monitoring does not affect the normal operation of the optical network; further, by selecting a narrow linewidth pulsed laser and an optical filter, only the narrowband spectrum of the pulsed light wavelength range can be collected by the photodetector, improving the dynamic range and range of the OTDR itself. And can filter out most of the reverse ASE in the EDFA system, improving the dynamic range of online monitoring.

In the embodiment of the present invention, the processor 105 is further configured to record the light intensity and time of receiving the partially backscattered light and the reflected light: determining the physical state of the point according to the light intensity, and calculating according to the time of the return processor The distance from this point is plotted to plot the fiber length and attenuation profile.

Example 4:

The embodiment of the present invention further provides an online optical time domain reflectometer using the online optical time domain reflectometer as described in Embodiment 1 in the method of the embodiment of the present invention, as shown in FIG. The method also includes:

In step 301, the narrow linewidth pulsed laser 101 emits narrow linewidth pulsed light under the drive of the processor 105.

The center wavelength of the pulsed laser is optional from 1480 to 1520 nm and 1610 to 1630 nm (excluding 1490 and 1510 nm monitored by OSC), and the 20 dB bandwidth is no more than 6 nm (as shown in Figure 1, the bandwidth Δλ corresponding to 20 dB lower than the peak power is no more than 6 nm). ), pulse width 5 ~ 20000ns can be set.

In step 302, the narrow linewidth pulsed light passes through the first inlet port and the second inlet/outlet port of the circulator 102 to enter the fiber to be tested.

The generated Rayleigh scattered light and Fresnel reflected light are transmitted through the optical fiber 203, and enter the detecting portion of the OTDR through the 2 interface 2 and the interface 3 of the circulator 102, wherein the detecting portion includes the narrowband WDM 103 and the APD 1045.

In step 303, the narrow linewidth pulsed light produces backscattered light and/or reflected light when it encounters network nodes, breakpoints, and/or deformation points during transmission in the fiber.

In step 304, the backscattered light and/or the reflected light corresponding to the narrow linewidth pulsed light, together with the reverse ASE light generated by the data signal, passes through the second inlet/exit port and the third inlet port of the circulator 102. The transmission channel filters out the reverse ASE light outside the filtering bandwidth through the optical filter 103, and the backscattered light and/or the reflected light of the reverse ASE light and the narrow linewidth pulsed light within the remaining filtering bandwidth are received by the photodetector 104. collection.

Filtering with a 30 dB bandwidth of no more than 6 nm narrowband WDM 103 (passband attenuation profile as shown in Figure 3) reduces the reverse ASE optical power entering the APD 104, improves the detection performance of the APD 104, and converts the signal through the APD 104. The signal processor 105 performs analysis and processing.

In step 305, the signal converted by photodetector 104 is analyzed and processed by processor 105.

Through the above steps, the OTDR is installed in the optical communication system rack in the form of an optical module, and realizes the function of online monitoring of the OTN, and the dynamic range degradation is less than 6 dB (1502 nm OTDR can be less than 3 dB, and 1625 nm OTDR can be less than 6 dB).

In the embodiment of the present invention, the processor 105 is further configured to record the light intensity and time of receiving the partially backscattered light and the reflected light: determining the physical state of the point according to the light intensity, according to the time of returning to the processor The distance at this point is calculated to plot the fiber length and attenuation profile.

It should be noted that the content interaction between the modules and the units in the above-mentioned device and the system, the execution process, and the like are based on the same concept as the embodiment of the processing method of the present invention. For details, refer to the description in the method embodiment of the present invention. , will not repeat them here.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

An online optical time domain reflectometer structure comprising a narrow linewidth pulsed laser, a circulator, an optical filter, a photodetector and a processor, specifically:

The light exit of the narrow linewidth pulsed laser is connected to the first light inlet of the circulator, and the second inlet/outlet of the circulator is used for connecting the external fiber to be tested; wherein the center wavelength of the narrow linewidth pulse laser includes 1480 ~ 1520nm and 1610 ~ 1630nm, and the 20dB bandwidth of the narrow line width pulse is less than or equal to 6nm, the narrow line width pulse pulse width includes 5 ~ 20000ns;

a third light exit port of the circulator is connected to the optical filter, and the optical filter is connected in series between the third light exit port of the circulator and the photodetector;

The signal output port of the photodetector is coupled to the processor, and the processor is further coupled to a narrow linewidth pulsed laser to provide a drive signal for the narrow linewidth pulsed laser.
The on-line optical time domain reflectometer structure according to claim 1, wherein the optical filter is specifically a narrow linewidth filter having a 30 dB bandwidth of less than or equal to 6 nm.
The on-line optical time domain reflectometer structure according to claim 1, wherein the center wavelength of the narrow linewidth pulse laser is specifically 1502 nm, and the 20 dB bandwidth of the narrow line width pulse is less than or equal to 6 nm, and the pulse width is based on The length of the optical path to be detected and the resolution of the event are comprehensively set; wherein the smaller the pulse width, the stronger the ability to distinguish adjacent events; the larger the pulse width, the longer the distance of the optical path that can be detected.
The on-line optical time domain reflectometer structure according to claim 1, wherein the center wavelength of the narrow linewidth pulse laser is specifically 1625 nm, and the 20 dB bandwidth of the narrow line width pulse is less than or equal to 6 nm, and the pulse width is according to The length of the optical path to be detected and the resolution of the event are comprehensively set; wherein the smaller the pulse width, the stronger the ability to distinguish adjacent events; the larger the pulse width, the longer the distance of the optical path that can be detected.
An optical optical time domain reflectance detection system, comprising: the optical time domain reflectometer according to any one of claims 1-4, a transmission optical signal, a wavelength division multiplexer, and a fiber network to be tested, wherein The fiber network to be tested includes one or more network nodes, specifically:

The transmission optical signal is connected to a first input port of the wavelength division multiplexer, the second input/output port of the wavelength division multiplexer is connected to the optical fiber network to be tested, and the third input/output of the wavelength division multiplexer a port connected to the optical time domain reflectometer;

The optical fiber network to be tested is composed of one or more optical fiber links, and each of the optical fiber links is connected by a connector, and the connector is configured to form a partial reflection on a narrow linewidth pulse detection signal of the optical time domain reflectometer; Wherein, the narrow linewidth pulse detection signal transmits backscattering in the optical fiber, and the fiber end face or the fiber cross section forms a strong reflection on the narrow linewidth pulse detection signal.
The on-line optical time domain reflection detecting system according to claim 5, wherein the processor is further configured to record the light intensity and time of receiving the portion of the backscattered light and the reflected light: determining the point according to the light intensity The physical state, the distance from the point is calculated based on the time returned to the processor to plot the fiber length and attenuation profile.
An online optical time domain reflection detection system, comprising: a narrow linewidth pulse laser, a circulator, a photodetector, a processor, a transmission optical signal, a wavelength division multiplexer, an optical filter, and a fiber network to be tested , wherein the fiber network to be tested includes one or more network nodes, specifically:

The transmission optical signal is connected to a first input port of the wavelength division multiplexer, the second input/output port of the wavelength division multiplexer is connected to the optical fiber network to be tested, and the third input/output of the wavelength division multiplexer a port connecting the second inlet/outlet of the circulator;

The light exit of the narrow linewidth pulsed laser is connected to the first light entrance of the circulator, and the third light exit of the circulator is connected between the light detectors; wherein the center wavelength of the narrow linewidth pulse laser comprises 1480-1520 nm And 1610 ~ 1630nm, and the 20dB bandwidth of the narrow line width pulse is less than or equal to 6nm, the narrow line width pulse pulse width includes 5 ~ 20000ns;

a signal output port of the photodetector is connected to the processor, and the processor is further connected to a narrow linewidth pulse laser to provide a driving signal for the narrow linewidth pulsed laser;

The optical fiber network to be tested is composed of one or more optical fiber links, and each of the optical fiber links is connected by a connector, and the connector is configured to form a partial reflection on a narrow linewidth pulse detection signal of the optical time domain reflectometer; Wherein, the narrow linewidth pulse detection signal transmits backscattering in the optical fiber, and the fiber end face or the fiber cross section forms a strong reflection on the narrow linewidth pulse detection signal.
The on-line optical time domain reflectance detecting system according to claim 7, wherein the processor is further configured to record light intensity and time of receiving the portion of the backscattered light and the reflected light: determining according to the light intensity The physical state of the point is calculated from the time returned to the processor to plot the fiber length and attenuation profile.
An online optical time domain reflectometer, characterized in that the online optical time domain reflectometer according to any one of claims 1-4 comprises:

A narrow linewidth pulsed laser emits narrow linewidth pulsed light driven by a processor;

The narrow linewidth pulsed light passes through the first inlet port and the second inlet/outlet port of the circulator to enter the fiber to be tested;

The narrow linewidth pulsed light generates backscattered light and/or reflected light when encountering network nodes, breakpoints and/or deformation points during transmission in the optical fiber;

Backscattered light and/or reflected light corresponding to narrow linewidth pulsed light and normal data signal light, transmitted together with the reverse ASE light generated by the data signal through the second inlet/outlet port and the third inlet port of the circulator Channel, the reverse ASE light outside the filtering bandwidth is filtered by the optical filter, and the backscattered light and/or the reflected light of the reverse ASE light and the narrow linewidth pulsed light within the remaining filtering bandwidth are collected by the photodetector;

The signal converted by the photodetector is analyzed and processed by the processor.
The method of using an in-line optical time domain reflectometer according to claim 9, wherein the processor is further configured to record light intensity and time of receiving the portion of the backscattered light and the reflected light: according to the light intensity The physical state of the point is determined, and the distance of the point is calculated based on the time returned to the processor to plot the fiber length and the attenuation profile.