CN107483106B - Online optical time domain reflectometer structure, detection system and detection method - Google Patents
Online optical time domain reflectometer structure, detection system and detection method Download PDFInfo
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Abstract
The invention relates to the technical field of optical fiber detection, and provides an online optical time domain reflectometer structure, a detection system and a detection method. The light outlet of the narrow linewidth pulse laser in the structure is connected with a first light inlet of the circulator, and a second light inlet/outlet of the circulator is used for connecting an external optical fiber to be tested; the third light outlet of the circulator is connected with an optical filter, and the optical filter is connected between the third light outlet of the circulator and the optical detector in series; the signal output port of the optical detector is connected with the processor, and the processor is also connected with the narrow linewidth pulse laser to provide a driving signal for the narrow linewidth pulse laser. According to the invention, by selecting the narrow linewidth pulse laser and the optical filter to be matched for use, only the narrow-band spectrum within the pulse light wavelength range can be collected by the optical detector, the dynamic range and the measuring range of the OTDR are improved, most reverse ASE in the EDFA system can be filtered, and the dynamic range during online monitoring is improved.
Description
[ technical field ] A method for producing a semiconductor device
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 of the invention ]
An Optical Time Domain Reflectometer (OTDR) is an important testing instrument in an Optical fiber communication system, and an Optical transmission module of the OTDR transmits a set Optical pulse signal, and according to the principle of backward fresnel reflection and rayleigh scattering, the reflected Optical signal is converted by an Optical receiving module (including an Avalanche Photodiode (APD)), and then is subjected to data processing and analysis by a signal processing unit, so as to obtain parameters such as average loss of the tested Optical fiber. The optical fiber link loss measuring device can measure the actual length and average loss of an optical fiber in an optical fiber communication system, and can detect, locate and measure many types of events on the optical fiber link, such as points with large loss formed by optical fiber fusion, connectors, bending and the like in the link.
Dynamic range is a very important parameter of OTDR and is often used to classify the performance of OTDR. The dynamic range is defined as the difference between the starting level and the noise level on the backscattering curve, which is the maximum attenuation value (in dB) of the backscattering 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 by the difference between the starting level and the noise root mean square level on the backscatter curve (when the signal-to-noise ratio is 1).
In optical Fiber communication, an Erbium Doped Fiber Amplifier (EDFA) system has been used to check the loss of an optical Fiber link using a 1510nm light source, and the EDFA is internally integrated or the system is provided with an input/output terminal SIN and SOUT (light transmission wavelength range is 1500-1520 nm) of the 1510nm light source. Using a 1510nm light source, it is usually only possible to determine whether the entire fiber link is too lossy or not through power changes, and the type and location of the failure cannot be known. OTDR is widely used in optical fiber communication systems because it can locate the cause and accurate location of a fault point.
Improving the dynamic range and detection accuracy of OTDR has been the subject of research by researchers in the world, and by improving the optical path, detection circuit and algorithm, the performance of OTDR has been improved:
in the patent optical module of an optical time domain reflectometer, the optical time domain reflectometer and an optical fiber testing method of 2004, by the company of hua, the dynamic range of the OTDR is improved by improving an OTDR receiving circuit and amplifying a returned optical signal in a segmented manner by using different amplification gears of an amplifier without changing the size of detection optical power.
2011 japan cross river corporation has designed a Bidirectional OTDR module in the patent "Bidirectional optical module and optical domain reflectometer equaled with the Bidirectional optical module": the laser and the receiver are designed in the same module, a lens is used for focusing before the receiver, and then pinhole filtering is carried out, so that the precision of optical power measurement and reflection point positioning is improved.
In 2015, the department of development of the Changzhou province is connected in a patent of multifunctional FTTH special OTDR tester, a 1550nm laser is used, a film is coated on an APD or a lens is added, and light except 1550nm is filtered out, so that the measuring range reaches 50 km.
EXFO in 2017 provided an OTDR algorithm and apparatus for detecting one or more events in an optical fiber link in the Multiple-acquisition OTDR method Device. By multiple light acquisitions, test light pulses of different pulse widths or wavelengths are propagated in the optical link and corresponding return light signals from the optical fiber link are detected to determine the number and location of events.
With the rapid development of optical fiber communication networks, how to perform efficient and flexible detection and maintenance on optical fiber networks is a great challenge for operators. The traditional external OTDR module is expensive and large in size, and before detection, the optical fiber needs to be disconnected from the system to analyze the position of a fault or a breakpoint, so that the optical fiber link cannot be detected in real time, and normal transmission of service light is influenced.
The application of online OTDR modules has just been rising in 2016, and a system manufacturer generally attaches importance to the testing and popularization of online products, and the whole market is in the initial growth stage. On one hand, the on-line OTDR can be used for on-site laying and post-maintenance of a long-distance optical fiber communication system, and on the other hand, the on-line monitoring can be carried out on an optical fiber communication network, so that the position of an optical fiber fault point can be rapidly and accurately determined, and the normal communication of the system is ensured. The on-line monitoring requires that the OTDR is installed on the optical communication system frame in the form of an optical module, and the real-time system monitoring can be realized in the application, namely the OTDR can be integrated into the existing system without interference or interference from other components. After the evolution maturity of practical effect and application mode of the OTDR trial in 2016, the market gradually accepts the OTDR as the optimal solution for monitoring the optical fiber link.
In real-time in-system monitoring applications, there are additional requirements on OTDR performance. Conventional techniques suffer from severe degradation in this regard because in EDFA systems, reverse ASE generated by the link enters the OTDR, affecting the detection of APDs, resulting in a decrease in dynamic range of more than 10dB and a reduction in the maximum fibre distance that the OTDR can detect.
[ summary of the invention ]
The technical problem to be solved by the invention is that in the system, under the real-time system monitoring application, extra requirements are required on the OTDR performance, and the conventional technology is seriously deteriorated, because in an EDFA system, reverse ASE generated by a link enters the OTDR to influence the detection of APD, the dynamic range is reduced by more than 10dB, and the maximum optical fiber distance which can be detected by the OTDR is shortened.
The invention adopts the following technical scheme:
in a first aspect, the present invention provides an online optical time domain reflectometer structure, including a narrow linewidth pulse laser, a circulator, an optical filter, an optical detector, and a processor, specifically:
the light outlet of the narrow linewidth pulse laser is connected with the first light inlet of the circulator, and the second light inlet/outlet of the circulator is used for connecting an external optical fiber to be tested; the central wavelength of the narrow linewidth pulse laser comprises 1480-1520nm and 1610-1630nm, the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width of the narrow linewidth pulse comprises 5-20000 ns;
the third light outlet of the circulator is connected with the optical filter, and the optical filter is connected between the third light outlet of the circulator and the optical detector in series;
the signal output port of the optical detector is connected with the processor, and the processor is also connected with the narrow linewidth pulse laser and provides a driving signal for the narrow linewidth pulse laser.
Preferably, the optical filter is a narrow linewidth filter, and the 30dB bandwidth of the optical filter is less than or equal to 6 nm.
Preferably, the central wavelength of the narrow-linewidth pulse laser is 1502nm, the 20dB bandwidth of the narrow-linewidth pulse is less than or equal to 6nm, and the pulse width is comprehensively set according to the length of the optical path to be detected and the event resolution; wherein, the smaller the pulse width is, the stronger the ability to distinguish adjacent events is; the larger the pulse width, the longer the distance of the optical path that can be detected.
Preferably, the central wavelength of the narrow linewidth pulse laser is 1625nm, the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width is comprehensively set according to the length of the optical path to be detected and the event resolution; wherein, the smaller the pulse width is, the stronger the ability to distinguish adjacent events is; 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 reflectometry system, including the optical time domain reflectometer, a transmission optical signal, a wavelength division multiplexer, and a to-be-tested optical fiber network according to the first aspect, where the to-be-tested optical fiber network includes one or more network nodes, specifically:
the transmission optical signal is connected with a first input port of a wavelength division multiplexer, a second input/output port of the wavelength division multiplexer is connected with an optical fiber network to be tested, and a third input/output port of the wavelength division multiplexer is connected with the optical time domain reflectometer;
the optical fiber network to be tested consists of one or more sections of optical fiber links, each section of optical fiber link is connected through a connector, and the connector is used for forming partial reflection on a narrow-linewidth pulse detection signal of the optical time domain reflectometer; the narrow-linewidth pulse detection signal is transmitted in the optical fiber to generate back scattering, and the end face or the cross section of the optical fiber forms strong reflection on the narrow-linewidth pulse detection signal.
Preferably, the processor is further configured to record the intensity and time of light received from the portion of backscattered and reflected light: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile.
In a third aspect, the present invention further provides an online optical time domain reflectometry detection system, including a narrow linewidth pulse laser, a circulator, an optical detector, a processor, a transmission optical signal, a wavelength division multiplexer, an optical filter, and a to-be-detected optical fiber network, where the to-be-detected optical fiber network includes one or more network nodes, specifically:
the transmission optical signal is connected with a first input port of a wavelength division multiplexer, a second input/output port of the wavelength division multiplexer is connected with an optical fiber network to be tested, and a third input/output port of the wavelength division multiplexer is connected with a second input/output port of the circulator;
a light outlet of the narrow linewidth pulse laser is connected with a first light inlet of the circulator, and a third light outlet of the circulator is connected between the optical detectors; the central wavelength of the narrow linewidth pulse laser comprises 1480-1520nm and 1610-1630nm, the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width of the narrow linewidth pulse comprises 5-20000 ns;
a signal output port of the optical detector is connected with the processor, and the processor is also connected with the narrow linewidth pulse laser and provides a driving signal for the narrow linewidth pulse laser;
the optical fiber network to be tested consists of one or more sections of optical fiber links, each section of optical fiber link is connected through a connector, and the connector is used for forming partial reflection on a narrow-linewidth pulse detection signal of the optical time domain reflectometer; the narrow-linewidth pulse detection signal is transmitted in the optical fiber to generate back scattering, and the end face or the cross section of the optical fiber forms strong reflection on the narrow-linewidth pulse detection signal.
Preferably, the processor is further configured to record the intensity and time of light received from the portion of backscattered and reflected light: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out 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, including:
the narrow-linewidth pulse laser emits narrow-linewidth pulse light under the drive of the processor;
narrow-linewidth pulse light enters the optical fiber to be tested through a first light inlet and a second light inlet/outlet of the circulator;
in the transmission process of narrow-linewidth pulse light in the optical fiber, when meeting network nodes, breakpoints and/or deformation points, back scattered light and/or reflected light are generated;
the backward scattered light and/or reflected light corresponding to the narrow-linewidth pulse light and the common data signal light passes through a second light inlet/outlet and a third light inlet transmission channel of the circulator together with reverse ASE light generated by the data signal, the reverse ASE light outside the filtering bandwidth is filtered out through an optical filter, and the backward scattered light and/or reflected light of the reverse ASE light and the narrow-linewidth pulse light within the residual filtering bandwidth are collected by an optical detector;
the signal converted by the light detector is analyzed and processed by a processor.
Preferably, the processor is further configured to record the intensity and time of light received from the portion of backscattered and reflected light: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile.
Compared with the prior art, the invention has the beneficial effects that:
the invention selects the pulse laser with specific wavelength, so that the working wavelength of the OTDR is different from the service optical signal, and the monitoring of the OTDR can not influence the normal operation of the optical network; furthermore, by selecting the narrow linewidth pulse laser to be matched with the optical filter, only the narrow-band spectrum within the pulse light wavelength range can be collected by the optical detector, the dynamic range and the measuring range of the OTDR are improved, most reverse ASE in the EDFA system can be filtered, and the dynamic range during online monitoring is improved.
[ 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 description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an on-line optical time domain reflectometer according to an embodiment of the present invention;
fig. 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;
FIG. 3 is a schematic diagram of filter performance parameters according to an embodiment of the present invention;
fig. 4 is a back scattering graph of 1502nm OTDR when an OTN monitors an EDFA on-line and shuts down a pump according to an embodiment of the present invention;
fig. 5 is a back scattering graph of 1502nm OTDR when an OTN monitors an EDFA on-line and pumps up, according to an embodiment of the present invention;
fig. 6 is a backscattering graph of an OTDR of 1625nm when an OTN monitors an EDFA pump shutdown on line according to an embodiment of the present invention;
fig. 7 is a backscattering plot of a 1625nm OTDR when an OTN online monitoring EDFA is started according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of an on-line optical time domain reflectometry system according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of an alternative on-line optical time domain reflectometry system architecture according to an embodiment of the present invention;
fig. 10 is a schematic flow chart of an on-line optical time domain reflection detection method according to an embodiment of the present invention.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be 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 terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are for convenience only to describe the present invention without requiring the present invention to be necessarily constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the embodiments of the present invention, the symbol "/" indicates that two functions are simultaneously performed, for example, "second light inlet/outlet port" indicates that the port can be used for both light inlet and light outlet. And for the symbol "a and/or B" it is indicated that the combination between the front and rear objects connected by the symbol includes three cases "a", "B", "a and B", for example "backscattered light and/or reflected light", it is indicated that it can express any one of the three meanings of "backscattered light alone", reflected light alone ", and" backscattered light and reflected light ".
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1:
the light outlet of the narrow linewidth pulse laser 101 is connected with a first light inlet of a circulator (a corresponding port marked with 1 in the circulator 102 in fig. 1), and a second light inlet/outlet of the circulator 102 (a corresponding port marked with 2 in the circulator 102 in fig. 1) is used for connecting an external optical fiber to be tested; the central wavelength of the narrow linewidth pulse laser 101 comprises 1480-1520nm and 1610-1630nm, the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the narrow linewidth pulse width comprises 5-20000 ns (as shown in fig. 2, wherein the width of delta lambda is less than or equal to 6 nm);
in selecting the center wavelength of the narrow linewidth pulse laser 101, in addition to the conventional data signal use bands, such as 1530nm to 1565nm in the C band and 1565nm to 1625nm in the L band, some bands designated for special purposes, such as: 1490nm and 1510nm, which are used for conventional Optical Supervisory Channels (OSC) are also generally excluded from the selection of the center wavelength of the narrow linewidth pulsed laser 101. Wherein, the cutoff wavelength actually used in the L band is only 1605nm, and 1610-1630nm selected in the embodiment of the present invention can be applied; if the L-band cut-off wavelength reaches 1625nm, the OTDR at 1626-. In addition, the conventional optical supervisory channel can only determine whether the entire optical fiber link is too lossy or not through power change, and cannot know the type and location of the fault. The monitoring wavelength for standard writing of ITU is 1510nm, and 1490nm is an alternative.
A third light outlet of the circulator 102 (a corresponding port marked with 3 in the circulator 102 in fig. 1) is connected to the optical filter 103, and the optical filter 103 is connected in series between the third light outlet of the circulator 102 and the optical detector 104;
the signal output port of the optical detector 104 is connected with the processor 105, and the processor 105 is further connected with the narrow linewidth pulse laser 101, so as to provide a driving signal for the narrow linewidth pulse laser 101.
The embodiment of the invention selects the pulse laser with specific wavelength, so that the working wavelength of the OTDR is different from the service optical signal (also called as data signal light), and the monitoring of the OTDR can not influence the normal operation of an optical network; furthermore, by selecting a narrow-linewidth pulse laser and an optical filter (for example, a Wavelength Division Multiplexer (WDM) for short) to be used in combination, only a narrow-band spectrum in the pulse light Wavelength range can be collected by the optical detector, the dynamic range (above 36 dB) and the range (up to 260km) of the OTDR itself are increased, most of the reverse ASE in the EDFA system can be filtered (for example, 20dBm output amplifier, after passing through a 125km fiber, the ASE power generated at 1480 to 1520nm is-38.72 dBm, after passing through the 1502nm Wavelength division multiplexer (transmitting light in 1502nm bandwidth, and reflecting other light), the power is reduced to-52.11 dBm in the 1480 to 1520nm range, and the dynamic range during online monitoring is improved.
In the embodiment of the present invention, the optical filter 103 is specifically a narrow linewidth filter, and the 30dB bandwidth thereof is less than or equal to 6 nm. As shown in fig. 3, the length of Δ λ is less than or equal to 6nm, and in a preferred implementation, the central wavelength λ of the filter window of the optical filter coincides with the central wavelength of the narrow-linewidth pulsed laser. Wherein 6nm is the most significant interval value obtained by the test of the embodiment of the present invention, and in the actual implementation process, considering the manufacturing difficulty and the processing cost of the device, increasing the value of the 30dB bandwidth by a proper loss filtering effect is also an optional implementation scheme, and should also belong to an equivalent scheme under the common concept of the present invention. The narrow linewidth filter has small parameter setting conditions, reduces reverse ASE optical power entering APD, and improves the detection performance of APD.
In the embodiment of the present invention, the center wavelengths of two typical narrow linewidth pulse lasers 101 are also provided, and corresponding experimental result data is given for conformity.
The first condition is as follows:
the central wavelength of the narrow linewidth pulse laser 101 is 1502nm, and the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, wherein the total length of the optical fiber reaches 125km, 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 event resolution; wherein, the smaller the pulse width is, the stronger the ability to distinguish adjacent events is; the larger the pulse width, the longer the distance of the optical path that can be detected.
As shown in fig. 4, the dynamic range of 1502nm OTDR, when the EDFA is not operating, is 37.58dB, where the dynamic range is the range from the initial optical attenuation intensity to the time when noise is generated as shown in fig. 4; as shown in fig. 5, the dynamic range of the 1502nm OTDR degrades to 34.98dB when the EDFA is in operation. When the OTDR instrument provided by the embodiment of the invention is applied to OTN on-line monitoring, the dynamic range is only degraded by 2.60dB (obtained by calculation of 37.58dB-34.98 dB).
Case two:
the central wavelength of the narrow linewidth pulse laser 101 is 1625nm, and the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, wherein the total length of the optical fiber reaches 125km, 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 event resolution; wherein, the smaller the pulse width is, the stronger the ability to distinguish adjacent events is; the larger the pulse width, the longer the distance of the optical path that can be detected.
As shown in FIG. 6, the dynamic range of the 1625nm OTDR is 36.00dB when the EDFA is not operating; as shown in fig. 7, the dynamic range of the 1625nm OTDR degrades to 30.50dB when the EDFA is in operation. When the OTDR instrument provided by the embodiment of the invention is applied to OTN online monitoring, the dynamic range is only degraded by 5.50 dB.
Example 2:
on the basis that embodiment 1 of the present invention provides an online optical time domain reflectometer structure, an embodiment of the present invention further provides an online optical time domain reflection detection system, where the embodiment uses the optical time domain reflectometer 100 as set forth in embodiment 1, as shown in fig. 8, the online optical time domain reflection detection system further includes a transmission optical signal 201, a wavelength division multiplexer 202, and an optical fiber network to be detected 203, where the optical fiber network to be detected is composed of one or more segments of optical fiber links, each segment of optical fiber link is connected by a connector, and a situation such as a fusion point, a bend, a fracture, or a mechanical joint may exist in an optical fiber, specifically:
the transmission optical signal 201 is connected to a first input port of a wavelength division multiplexer 202, a second input/output port of the wavelength division multiplexer 202 is connected to an optical fiber network 203 to be tested, and a third input/output port of the wavelength division multiplexer 202 is connected to the optical time domain reflectometer;
the optical fiber network to be tested consists of one or more sections of optical fiber links, each section of optical fiber link is connected through a connector, and the connector is used for forming partial reflection on a narrow-linewidth pulse detection signal of the optical time domain reflectometer; the narrow-linewidth pulse detection signal is transmitted in the optical fiber to generate back scattering, and the end face or the cross section of the optical fiber forms strong reflection on the narrow-linewidth pulse detection signal.
Because the online optical time domain reflectometer is adopted in the embodiment 1, the embodiment of the invention also selects the pulse laser with specific wavelength, so that the working wavelength of the OTDR is different from the service optical signal, and the monitoring of the OTDR can not influence the normal operation of the optical network; furthermore, by selecting the narrow linewidth pulse laser to be matched with the optical filter, only the narrow-band spectrum within the pulse light wavelength range can be collected by the optical detector, the dynamic range and the measuring range of the OTDR are improved, most reverse ASE in the EDFA system can be filtered, and the dynamic range during online monitoring is improved.
In an embodiment of the present invention, the processor 105 is further configured to record the intensity and time of the received part of the backscattered and reflected light: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile. The corresponding attenuation profiles can be shown in fig. 4-7, and are not described herein again.
Example 3:
in an embodiment of the present invention, an online optical time domain reflectometry system is further provided, and compared with the online optical time domain reflectometry OTDR described in embodiment 1 directly cited in embodiment 2, in the embodiment of the present invention, the optical filter in embodiment 1 is adjusted in position, extracted from the OTDR100, and arranged between the wavelength division multiplexer 202 and the OTDR100, as shown in fig. 9, the system includes a narrow linewidth pulse laser 101, a circulator 102, an optical detector 104, a processor 105, a transmission optical signal 201, the wavelength division multiplexer 202, an optical filter 103, and an optical fiber network 203 to be tested, where the optical fiber network to be tested includes one or more network nodes, specifically:
the transmission optical signal 201 is connected to a first input port of a wavelength division multiplexer 202, a second input/output port of the wavelength division multiplexer 202 is connected to an optical fiber network 203 to be tested, and a third input/output port of the wavelength division multiplexer 202 is connected to a second input/output port of the circulator 102;
for example: the 1550/lambda wavelength division multiplexer 202 is characterized by transmitting light of 1528-1568 nm and reflecting light with lambda wavelength (central wavelength selected by OTDR). The first input port and the second input/output port of the wavelength division multiplexer 202 are connected with 1528-1568 nm light, and the first input port and the third input/output port are connected with light with a central wavelength lambda selected by OTDR.
A light outlet of the narrow linewidth pulse laser 101 is connected with a first light inlet of the circulator 102, and a third light outlet of the circulator 102 is connected between the optical detectors 104; the central wavelength of the narrow linewidth pulse laser 101 comprises 1480-1520nm and 1610-1630nm, the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width of the narrow linewidth pulse comprises 5-20000 ns;
a signal output port of the optical detector 104 is connected with the processor 105, and the processor 105 is further connected with the narrow linewidth pulse laser 101 to provide a driving signal for the narrow linewidth pulse laser 101;
the optical fiber network to be tested consists of one or more sections of optical fiber links, each section of optical fiber link is connected through a connector, and the connector is used for forming partial reflection on a narrow-linewidth pulse detection signal of the optical time domain reflectometer; the narrow-linewidth pulse detection signal is transmitted in the optical fiber to generate back scattering, and the end face or the cross section of the optical fiber forms strong reflection on the narrow-linewidth pulse detection signal.
Because the invention adopts the structure of the on-line optical time domain reflectometer similar to that described in embodiment 1, the embodiment of the invention also selects the pulse laser with specific wavelength, so that the working wavelength of the OTDR is different from the service optical signal, and the monitoring of the OTDR does not influence the normal operation of the optical network; furthermore, by selecting the narrow linewidth pulse laser to be matched with the optical filter, only the narrow-band spectrum within the pulse light wavelength range can be collected by the optical detector, the dynamic range and the measuring range of the OTDR are improved, most reverse ASE in the EDFA system can be filtered, and the dynamic range during online monitoring is improved.
In an embodiment of the present invention, the processor 105 is further configured to record the light intensity and the time when the part of the backscattered and reflected light is received: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile.
Example 4:
the embodiment of the present invention further provides a method for using an online optical time domain reflectometer, where the online optical time domain reflectometer described in embodiment 1 is used in the method in the embodiment of the present invention, as shown in fig. 10, the method further includes:
in step 301, the narrow-linewidth pulse laser 101 emits narrow-linewidth pulsed light under the drive of the processor 105.
The center wavelength of the pulse laser is 1480-1520nm and 1610-1630nm (except 1490 and 1510nm monitored by OSC), the 20dB bandwidth is not more than 6nm (as shown in FIG. 1, the bandwidth Delta lambda corresponding to 20dB lower than the peak power is not more than 6nm), and the pulse width is 5-20000 ns.
In step 302, narrow-linewidth pulsed light enters the optical fiber to be tested through the first light inlet and the second light inlet/outlet of the circulator 102.
The rayleigh scattered light and fresnel reflected light generated are transmitted in fiber 203 and enter the detection section of the OTDR through interface 2 and interface 3 of circulator 102, wherein the detection section includes narrowband WDM103 and APD 1045.
In step 303, in the process of transmitting the narrow-linewidth pulsed light in the optical fiber, when encountering a network node, a breakpoint and/or a deformation point, a back-scattered light and/or a reflected light is generated.
In step 304, the backscattered light and/or reflected light corresponding to the narrow-linewidth pulsed light passes through the second light inlet/outlet and the third light inlet transmission channel of the circulator 102 together with the reverse ASE light generated by the data signal, the reverse ASE light outside the filtering bandwidth is filtered out by the optical filter 103, and the backscattered light and/or reflected light of the reverse ASE light and the narrow-linewidth pulsed light within the remaining filtering bandwidth is collected by the optical detector 104.
The 30dB bandwidth is not more than 6nm narrow band WDM103 (the pass band attenuation spectrum type is shown in figure 3) is used for filtering, the reverse ASE optical power entering the APD104 is reduced, the detection performance of the APD104 is improved, and the signal converted by the APD104 is analyzed and processed by the signal processor 105.
In step 305, the signal converted by the light detector 104 is analyzed and processed by the processor 105.
Because the online optical time domain reflectometer is adopted in the embodiment 1, the embodiment of the invention also selects the pulse laser with specific wavelength, so that the working wavelength of the OTDR is different from the service optical signal, and the monitoring of the OTDR can not influence the normal operation of the optical network; furthermore, by selecting the narrow linewidth pulse laser to be matched with the optical filter, only the narrow-band spectrum within the pulse light wavelength range can be collected by the optical detector, the dynamic range and the measuring range of the OTDR are improved, most reverse ASE in the EDFA system can be filtered, and the dynamic range during online monitoring is improved.
Through the steps, the OTDR is installed on the optical communication system frame in the form of an optical module, the function of OTN online monitoring is realized, and the degradation of the dynamic range is less than 6dB (1502nm OTDR can be less than 3dB, and 1625nm OTDR can be less than 6 dB).
In an embodiment of the present invention, the processor 105 is further configured to record the light intensity and the time at which the portion of the backscattered and reflected light is received: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile.
It should be noted that, for the information interaction, execution process and other contents between the modules and units in the apparatus and system, the specific contents may refer to the description in the embodiment of the method of the present invention because the same concept is used as the embodiment of the processing method of the present invention, and are not described herein again.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (7)
1. The utility model provides an online optical time domain reflectometer structure which characterized in that, includes narrow linewidth pulse laser, circulator, optical filter, optical detector and treater, and is specific:
the light outlet of the narrow linewidth pulse laser is connected with the first light inlet of the circulator, and the second light inlet/outlet of the circulator is used for connecting an external optical fiber to be tested; the central wavelength of the narrow linewidth pulse laser comprises 1480-1520nm and 1610-1630nm, the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width of the narrow linewidth pulse comprises 5-20000 ns;
when the central wavelength of the narrow linewidth pulse laser is selected, avoiding the wave bands used by the current data signal, wherein the wave bands comprise one or more of 1530nm-1565nm of a C wave band, 1565nm-1625nm of an L wave band, 1490nm and 1510nm used for a conventional optical monitoring channel;
the third light outlet of the circulator is connected with the optical filter, and the optical filter is connected between the third light outlet of the circulator and the optical detector in series; the optical filter is a narrow linewidth filter, and the 30dB bandwidth of the optical filter is less than or equal to 6 nm;
the signal output port of the optical detector is connected with the processor, and the processor is also connected with the narrow linewidth pulse laser and provides a driving signal for the narrow linewidth pulse laser.
2. The on-line optical time domain reflectometer structure of claim 1, wherein the central wavelength of the narrow linewidth pulse laser is specifically 1502nm, and the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width is set synthetically according to the length of the optical path to be detected and the event resolution; wherein, the smaller the pulse width is, the stronger the ability to distinguish adjacent events is; the larger the pulse width, the longer the distance of the optical path that can be detected.
3. The on-line optical time domain reflectometer structure of claim 1, wherein the central wavelength of the narrow linewidth pulse laser is 1625nm, and the 20dB bandwidth of the narrow linewidth pulse is less than or equal to 6nm, and the pulse width is set synthetically according to the length of the optical path to be detected and the event resolution; wherein, the smaller the pulse width is, the stronger the ability to distinguish adjacent events is; the larger the pulse width, the longer the distance of the optical path that can be detected.
4. An on-line optical time domain reflectometry system comprising an optical time domain reflectometer according to any of claims 1 to 3, a transmission optical signal, a wavelength division multiplexer, an optical fiber network under test, wherein the optical fiber network under test comprises one or more network nodes, in particular:
the transmission optical signal is connected with a first input port of a wavelength division multiplexer, a second input/output port of the wavelength division multiplexer is connected with an optical fiber network to be tested, and a third input/output port of the wavelength division multiplexer is connected with the optical time domain reflectometer;
the optical fiber network to be tested consists of one or more sections of optical fiber links, each section of optical fiber link is connected through a connector, and the connector is used for forming partial reflection on a narrow-linewidth pulse detection signal of the optical time domain reflectometer; the narrow-linewidth pulse detection signal is transmitted in the optical fiber to generate back scattering, and the end face or the cross section of the optical fiber forms strong reflection on the narrow-linewidth pulse detection signal.
5. The on-line optical time domain reflectometry system of claim 4 wherein the processor is further configured to record the intensity and time of light received from the backscattered and reflected light: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile.
6. A method of using an in-line optical time domain reflectometer, wherein the in-line optical time domain reflectometer of any of claims 1 to 3 is used, comprising:
the narrow-linewidth pulse laser emits narrow-linewidth pulse light under the drive of the processor;
narrow-linewidth pulse light enters the optical fiber to be tested through a first light inlet and a second light inlet/outlet of the circulator;
in the transmission process of narrow-linewidth pulse light in the optical fiber, when meeting network nodes, breakpoints and/or deformation points, back scattered light and/or reflected light are generated;
the backward scattered light and/or reflected light corresponding to the narrow-linewidth pulse light and the common data signal light passes through a second light inlet/outlet and a third light inlet transmission channel of the circulator together with reverse ASE light generated by the data signal, the reverse ASE light outside the filtering bandwidth is filtered out through an optical filter, and the backward scattered light and/or reflected light of the reverse ASE light and the narrow-linewidth pulse light within the residual filtering bandwidth are collected by an optical detector;
the signal converted by the light detector is analyzed and processed by a processor.
7. The method of using an in-line optical time domain reflectometry according to claim 6, wherein the processor is further configured to record the intensity of light and the time at which the backscattered and reflected light is received: the physical state of the point is determined from the light intensity and the distance from the point is calculated from the time of return to the processor to trace out the fiber length and attenuation profile.
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| PCT/CN2017/118232 WO2019056634A1 (en) | 2017-09-25 | 2017-12-25 | Online optical time domain reflectometer structure, detection system, and detection method |
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