CN210444271U - Optical cable vibrating positioning device - Google Patents
Optical cable vibrating positioning device Download PDFInfo
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- CN210444271U CN210444271U CN201921560099.5U CN201921560099U CN210444271U CN 210444271 U CN210444271 U CN 210444271U CN 201921560099 U CN201921560099 U CN 201921560099U CN 210444271 U CN210444271 U CN 210444271U
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Abstract
The utility model discloses an optical cable vibration positioning device, which comprises a first differential phase optical time domain reflectometer, a second differential phase optical time domain reflectometer, a wavelength division multiplexer and a measured optical cable; the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer have different working wavelengths and different lengths of optical fiber delay lines; the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer are both connected with the wavelength division multiplexer, and the wavelength division multiplexer is also connected with a measured optical cable; after optical signals transmitted by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer pass through the wavelength division multiplexer and the tested optical cable, a back scattering signal and a reflection signal in the tested optical cable are received by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer. The utility model discloses can eliminate because of the optical cable vibration location blind area that the optic fibre Fresnel reflection arouses, carry out the accurate positioning to the vibration position of optical cable.
Description
Technical Field
The utility model relates to an optical communication test and optical fiber sensing technical field especially relate to a positioner of optical cable vibration.
Background
In maintaining a fiber optic network, in addition to Optical Time Domain Reflectometry (OTDR), common instruments are fiber optic fault trackers. The Optical Time Domain Reflectometer (OTDR) can measure the optical fiber length of an optical cable fault point, the optical cable fault tracker can measure the optical fiber length of an optical cable disturbance point, and the geographical position of the optical cable fault point can be estimated more accurately by analyzing the difference between the optical fiber lengths of the optical cable disturbance point and the optical cable fault point.
According to different disturbance modes of the optical cable, the current optical cable fault tracker is mainly based on the following principles: the bending change of the optical cable is detected by adopting P-OTDR, and the distance of the bent optical cable is positioned (Chinese patent CN201410662192.2 is a method for accurately positioning the fault point of the optical cable); detecting the temperature of the optical cable by using a B-OTDR (Brillouin-optical time domain reflectometer) or an R-OTDR (Raman-optical time domain reflectometer) to perform distance positioning on a heating part of the optical cable; detecting the vibration of the optical cable by using a phi-OTDR (phase-optical time domain reflectometer) to perform distance positioning on the knocked optical cable; the tapped cable is distance-located using a single-axis Sagnac fiber optic interferometer plus differential phase-OTDR probe cable vibration of the OTDR (US 20070264012a1-Identifying or locating waveguides).
The method for detecting the bending change of the optical cable by using the P-OTDR (polarization-optical time domain reflectometer) is used for accurately positioning the fault of the optical cable, and has the defect that the optical cable is required to be bent by about 1m in diameter. If the optical cable is laid tight and the optical cable cannot be drawn out to a sufficient length for bending, it is difficult to perform the bending of the optical cable, and it is inconvenient to perform accurate location of a fault in the optical cable by detecting the bent optical cable using a P-OTDR (polarization-optical time domain reflectometer). The main disadvantage is that the costs of B-OTDR, R-OTDR and phi-OTDR are too high when B-OTDR (Brillouin-optical time domain reflectometer), R-OTDR (Raman-optical time domain reflectometer) and phi-OTDR (phase-optical time domain reflectometer) are used for accurately positioning the disturbance point of the optical cable.
The differential phase-OTDR of the uniaxial Sagnac fiber optic interferometer and the OTDR is adopted to accurately position the disturbance (vibration) point of the optical cable, the cost is moderate, and the operation is convenient. However, in the optical fiber, fresnel reflection occurs due to factors such as connectors, breakpoints, end surfaces, etc., and the intensity of the optical signal generated by fresnel reflection is several orders of magnitude higher than the rayleigh scattering signal generated by the optical fiber. The existence of such blind areas seriously affects the accuracy of positioning the vibration position of the optical cable. Therefore, when the differential phase-OTDR is used to accurately locate the vibration position of the optical cable, the problem of the optical cable vibration location blind area caused by the fresnel reflection of the optical fiber needs to be solved.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a positioner of optical cable vibration can eliminate because of the optical cable vibration location blind area that the optic fibre Fresnel reflection arouses, carries out the accurate positioning to the vibration position of optical cable.
In order to achieve the above purpose, the utility model provides a following technical scheme:
a positioning device for optical cable vibration comprises a first differential phase optical time domain reflectometer, a second differential phase optical time domain reflectometer, a wavelength division multiplexer and a measured optical cable;
the working wavelengths of the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer are different;
the first differential phase optical time domain reflectometer comprises a first optical fiber delay line, the second differential phase optical time domain reflectometer comprises a second optical fiber delay line, and the lengths of the first optical fiber delay line and the second optical fiber delay line are different;
the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer are both connected with the wavelength division multiplexer, and the wavelength division multiplexer is also connected with a measured optical cable;
after optical signals transmitted by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer pass through the wavelength division multiplexer and the tested optical cable, a back scattering signal and a reflection signal in the tested optical cable are received by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer.
Optionally, the first differential phase optical time domain reflectometer includes:
a first optical pulse transmitter, a first optical receiver, and a first single-axis Sagnac interferometer;
the first optical pulse transmitter, the first single-axis Sagnac interferometer and the first optical receiver are connected in sequence.
Optionally, the second differential phase optical time domain reflectometer includes:
a second optical pulse transmitter, a second optical receiver, and a second single-axis Sagnac interferometer;
and the second optical pulse transmitter, the second single-axis Sagnac interferometer and the second optical receiver are connected in sequence.
Optionally, the operating wavelengths of the first optical pulse transmitter and the second optical pulse transmitter are any two of a C band of 1310nm, a 1490nm and 1550nm, an L band of 1550nm and a 1625 nm.
Optionally, the length range of the first optical fiber delay line and the second optical fiber delay line is 500 m-20 km.
Optionally, the light source type of the first optical pulse transmitter and the second optical pulse transmitter is F-PLD or SLD, the range of the optical pulse period value of the first optical pulse transmitter and the second optical pulse transmitter is 0.1ms to 2ms, and the range of the optical pulse width value of the first optical pulse transmitter and the second optical pulse transmitter is 50ns to 5000 ns.
Optionally, a length difference Δ L between the first optical fiber delay line and the second optical fiber delay line is at least greater than T/5, where T is an optical pulse width value, a unit of T is ns, and a unit of Δ L is m.
Optionally, the photodetectors used by the first optical receiver and the second optical receiver are APDs or PINs.
According to the utility model provides a concrete embodiment, the utility model discloses a following technological effect:
the utility model discloses an utilize first differential phase place optical time domain reflectometer and second differential phase place optical time domain reflectometer that operating wavelength is different and optic fibre delay line length is different, make the optic fibre delay line of different length of walking to the signal of different wavelength to correspond and obtain the analysis result, compare two results again, filter, thereby eliminate because of the optical cable vibration location blind area that the optic fibre Fresnel reflection arouses, carry out the accurate positioning to the vibration position of optical cable.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and 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 these drawings without creative efforts.
FIG. 1 is a schematic diagram of a conventional cable vibration positioning device;
FIG. 2 is a vibration positioning data curve diagram of a positioning device for vibration of an existing optical cable;
FIG. 3 is a schematic diagram of a vibration positioning blind area of a conventional optical cable vibration positioning device;
fig. 4 is a schematic structural view of the optical cable vibration positioning device of the present invention;
fig. 5 is the utility model discloses positioner's of optical cable vibration location data curve graph.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
The utility model aims at providing a positioner of optical cable vibration can eliminate because of the optical cable vibration location blind area that the optic fibre Fresnel reflection arouses, carries out the accurate positioning to the vibration position of optical cable.
The principle and the method of the utility model are as follows:
in the prior art, in the differential phase-OTDR for detecting the vibration of the optical cable and the vibration position of the optical cable, as shown in fig. 1, a uniaxial Sagnac fiber optic interferometer (also called unbalanced mach-zehnder interferometer) structure is adopted, and an optical signal output from an optical transmitter enters a cable to be detected after passing through the uniaxial Sagnac fiber optic interferometer, is scattered and reflected by the cable to be detected, and then enters an optical receiver after passing through the uniaxial Sagnac fiber optic interferometer. In this process, the optical signal is divided into four paths according to the path traveled: in the 1 st path, a first optical transmitter or a second optical transmitter, namely a 2x2 optical splitter, an optical fiber delay line, a 1x2 optical splitter, a tested optical cable, a 1x2 optical splitter, an optical fiber delay line, a 2x2 optical splitter and an optical receiver; in the 2 nd path, an optical transmitter, namely a 2x2 optical splitter, an optical fiber time delay line, a 1x2 optical splitter, an optical cable to be tested, a 1x2 optical splitter, a short optical fiber, a 2x2 optical splitter and an optical receiver; in the 3 rd path, an optical transmitter, a 2x2 optical splitter, a short optical fiber, a 1x2 optical splitter, a tested optical cable, a 1x2 optical splitter, an optical fiber time delay line, a 2x2 optical splitter and an optical receiver; in the 4 th path, an optical transmitter, namely a 2x2 optical splitter, a short optical fiber, a 1x2 optical splitter, a tested optical cable, a 1x2 optical splitter, a short optical fiber, a 2x2 optical splitter and an optical receiver;
the 2 nd path signal and the 3 rd path signal have the same walking path but different directions, the optical path difference of the two paths of signals is smaller than the coherence length of the optical signal, coherence is generated at the output end of the single-axis Sagnac optical fiber interferometer and can be used for detecting the vibration of the optical cable, and the signals contain the vibration information of the optical cable; the 1 st and 4 th path signals are different in walking path, one path of optical signal passes through the optical fiber delay line twice, the other path of optical signal does not pass through the optical fiber delay line, the optical path difference of the two paths of signals is far greater than the coherence length of the optical signal, so that the optical interference phenomenon can not occur, the optical signal cannot be used for detecting the vibration of the optical cable, and the part of signals do not contain the vibration information of the optical cable.
Therefore, the optical signal received by the optical receiver at a certain time may comprise two parts, one part of the signal comprises the cable vibration information, and the other part does not comprise the cable vibration information. If the portion of the signal containing the vibration information of the fiber optic cable is weak (e.g., the scattered signal of the optical fiber) and the portion of the signal not containing the vibration information of the fiber optic cable is strong (e.g., the fresnel reflected signal of the optical fiber), the strong signal masks the weak signal, and the vibration signal cannot be detected from the optical signal received during this time.
And because in the current differential phase-OTDR, a fiber delay line with a fixed length is used, once fresnel reflection exists at a certain point in a fiber circuit, starting from an optical transmitter, because the path traveled by the optical signal traveling the 4 th path is shortest, the first path reaches an optical receiver, the path traveled by the optical signal traveling the 1 st path is longest, the last path reaches the optical receiver, the path traveled by the optical signal traveling the 2 nd and 3 rd paths is between the lengths of the two paths, and the second path reaches the optical receiver, the optical receiver receives fresnel reflection signals at three different times, and actually receives the fresnel reflection signal optical pulses in three different time periods considering that the transmitted optical pulses have a certain width. The length of these time periods is typically greater than the width of the light pulses. In the received three Fresnel reflection signal light pulses, the three Fresnel reflection signal light pulses are arranged according to the receiving time sequence, the first light pulse and the third light pulse do not contain optical cable vibration information, and the second light pulse contains optical cable vibration information. This is because in the normal case, the fresnel reflected signal light pulse is much stronger than the fiber scattered signal; the scattered signal received in the first optical pulse signal time period contains the vibration information of the optical cable, but if the first optical pulse signal is too strong, the scattered signal received in the time period is greatly suppressed, and the too strong optical pulse signal is easy to cause the optical receiver circuit to be saturated, so that the vibration signal cannot be detected even in the time period when the first and third optical pulses appear. Therefore, if stronger Fresnel reflection exists in the optical fiber circuit, a dead zone of optical cable vibration detection can occur. The position of the blind zone is directly related to the position of a Fresnel reflection point in the optical fiber, and the size of the blind zone is directly related to the width of the optical pulse.
The principle of the utility model is as follows: the utility model discloses in the device, including first differential phase place optical time domain reflectometer and second differential phase place optical time domain reflectometer and a Wavelength Division Multiplexer (WDM), wherein, the transmission wavelength difference, the optic fibre time delay length difference of first differential phase place optical time domain reflectometer and second differential phase place optical time domain reflectometer;
the Wavelength Division Multiplexer (WDM) is used to multiplex two wavelength signals into one optical cable under test. In the measurement time period, the optical pulse transmitters with different wavelengths work simultaneously, so that signals with different wavelengths can go through optical fiber delay lines with different lengths; and the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer simultaneously measure the vibration position of the optical cable, and the two results are combined and screened to obtain the real vibration position of the optical cable. The difference between the lengths of the optical fiber time delay lines of the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer is enough to ensure that dead zones of the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer when the optical cable is measured to vibrate are not overlapped completely. Therefore, signals with different wavelengths are adopted for measurement in a measurement time period, each single-axis Sagnac interferometer uses optical fiber delay lines with different lengths to measure the vibration position of the optical cable respectively, results of the two times of measurement are compared, and then the real vibration position of the optical cable is obtained, so that the measurement blind zone generated by a Fresnel reflection point in the optical fiber can be eliminated.
FIG. 1 is a schematic diagram of a prior art apparatus for positioning optical cable vibrations using a single-fiber single-axis Sagnac fiber interferometer. The uniaxial Sagnac fiber optic interferometer comprises 12 x2 optical splitter with the splitting ratio of 50 to 50, 1x2 optical splitter with the splitting ratio of 50 to 50 and a fiber delay line. An optical pulse signal sent by an optical transmitter enters a tested cable through the single-axis Sagnac optical fiber interferometer, a scattered signal and Fresnel reflection generated by the tested cable return to the single-axis Sagnac optical fiber interferometer and enter the optical receiver, and then the optical pulse signal is amplified, subjected to digital/analog conversion and subjected to digital signal processing.
The simplest digital signal processing mode is to subtract two Optical Time Domain Reflectometer (OTDR) data frame signals, and determine whether there is a vibration signal on the optical cable and the position where the optical cable vibrates according to the data obtained by the subtraction. Fig. 2 shows two sets of data obtained by subtracting data frame signals from each other by the apparatus of fig. 1, where series 1 is a data set when there is no vibration on the optical cable, and series 2 is a data set when there is vibration on the optical cable. It can also be known from the data set of series 2 that the vibration occurs at point a and the end of the cable being measured is at point e.
If the tail end of the measured optical cable is flat, strong Fresnel reflection can be generated, the reflectivity can be as high as-15 dB, the scattering rate of the optical fiber is only about-50 dB (1550nm wavelength, 1 microsecond of optical pulse width), and the level difference of optical signals is 35 dB. In order to normally receive a scattered signal from an optical fiber, an optical receiver amplifier needs to have a certain gain, and when a strong fresnel reflection signal is received, an amplification circuit enters a saturation state. During the circuit entering the saturation state, the signal value obtained by the A/D circuit does not change, which means that the signal saturation period is a measurement blind area.
Fig. 3 shows data obtained from differential phase-OTDR of a single fiber delay line in the case of strong fresnel reflection at the end of the cable under test. It can be seen that the values from point b to point c are all 0. If the vibration occurrence position a unfortunately falls between the point b and the point c, the accurate value of the position a cannot be determined, although the vibration occurrence on the optical cable can still be judged at the moment.
In order to perform accurate vibration positioning when strong fresnel reflection occurs in a measured cable, it is necessary to eliminate the influence of a measurement blind area caused by fresnel reflection.
To this end, the utility model adopts the device structure of two differential phase optical time domain reflectometers with different wavelengths and different lengths of the optical fiber delay line shown in fig. 4.
The utility model discloses an among the optical cable vibration positioner, including first differential phase place optical time domain reflectometer, second differential phase place optical time domain reflectometer, wavelength division multiplexer and by the optical cable, the light signal of first differential phase place optical time domain reflectometer, second differential phase place optical time domain reflectometer is connected to one by the optical cable of surveying after closing the wave-division multiplexer.
Specifically, the first differential phase optical time domain reflectometer comprises a first optical pulse transmitter, a first optical receiver and a first uniaxial Sagnac interferometer; the first single-axis Sagnac optical fiber interferometer is used for enabling a back scattering signal and a reflection signal in a tested cable to generate interference after passing through the optical fiber interferometer; the first optical pulse transmitter, the first single-axis Sagnac interferometer and the first optical receiver are connected in sequence.
The first single-axis Sagnac interferometer comprises a first 2x2 optical splitter, a first 1x2 optical splitter, and a first fiber delay line; one port of the A side of the first 2x2 optical splitter is connected with a first optical pulse transmitter, and the other port of the A side of the first 2x2 optical splitter is connected with a first optical receiver; one port of the B side of the first 2x2 optical splitter is connected with one end of a first optical fiber delay line, the other port of the B side of the first 2x2 optical splitter is connected with one port of the A side of the first 1x2 optical splitter, and the other end of the first optical fiber delay line is connected with the other port of the A side of the first 1x2 optical splitter; and the first 1x2 optical splitter B-side port is connected with a first wavelength division port of a wavelength division multiplexer.
An optical pulse signal sent by the first optical transmitter enters the wavelength division multiplexer through the first single-axis Sagnac optical fiber interferometer and then enters the tested cable, a scattering signal and Fresnel reflection generated by the tested cable return to wavelength division multiplexing and then enter the first single-axis Sagnac optical fiber interferometer and then enter the first optical receiver, and the first optical receiver is connected with amplification, digital/analog conversion and digital signal processing.
The second differential phase optical time domain reflectometer comprises: a second optical pulse transmitter, a second optical receiver, and a second single-axis Sagnac interferometer; the second optical pulse transmitter is used for generating an optical pulse signal, the second optical pulse receiver is used for converting the optical signal into an electric signal, and the second single-axis Sagnac optical fiber interferometer is used for enabling a back scattering signal and a reflection signal in a tested cable to generate interference after passing through the optical fiber interferometer; and the second optical pulse transmitter, the second single-axis Sagnac interferometer and the second optical receiver are connected in sequence.
The second single-axis Sagnac interferometer comprises a second 2x2 optical splitter, a second 1x2 optical splitter, and a second fiber delay line; one port of the A side of the second 2x2 optical splitter is connected with a second optical pulse transmitter, and the other port of the A side of the second 2x2 optical splitter is connected with a second optical receiver; one port of the second 2x2 optical splitter on the B side is connected with one end of a second optical fiber delay line, the other port of the second optical fiber delay line is connected with one port of the second 1x2 optical splitter on the A side, and the other end of the second optical fiber delay line is connected with the other port of the second 1x2 optical splitter on the A side; and the second 1x2 optical splitter B-side port is connected with a second wavelength division port of the wavelength division multiplexer.
And an optical pulse signal sent by the second optical transmitter enters the wavelength division multiplexer through the second single-shaft Sagnac optical fiber interferometer and then enters the tested cable, a scattering signal and Fresnel reflection generated by the tested cable return to the wavelength division multiplexer and then enter the second single-shaft Sagnac optical fiber interferometer and then enter the second optical receiver, and the second optical receiver is subjected to amplification, digital/analog conversion and digital signal processing.
The first optical transmitter and the second optical transmitter have different working wavelengths, and the lengths of the first optical fiber delay line and the second optical fiber delay line are unequal. The lengths of the first and second optical fibre delay lines are selected taking into account the width of the optical transmit pulse used and the duration of time the optical receiver has taken from entering saturation to fully exiting saturation.
For the first differential phase optical time domain reflectometer, the vibration localization data curve is as series 1 in fig. 5; for the second differential phase optical time domain reflectometer, the vibration localization data curve is as series 2 in fig. 5. The measurement dead zone of the series 1 curve is b-c, and the measurement dead zone of the series 2 curve is b '-c', and the b-c region and the b '-c' region do not overlap. Therefore, if the vibration point a of the optical cable falls into the b-c area, the vibration point a cannot enter the b '-c' area; on the contrary, if the vibration point a of the optical cable falls into the b '-c' region, it does not enter the b-c region. Therefore, after the two test results obtained by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer are combined and screened, the finally obtained test result of the vibration point position of the optical cable is not influenced by Fresnel reflection existing in the optical fiber.
The utility model discloses a working parameter that device used:
the light source type adopted by the first optical pulse transmitter and the second optical pulse transmitter is F-PLD or SLD, and the F-PLD type is preferred; the working wavelengths of the first optical pulse transmitter and the second optical pulse transmitter are different, two of the 1310nm waveband, the 1490 waveband, the 1550nm C waveband, the 1550nm L waveband and the 1625nm waveband are selected, and the 1550nm C waveband and the 1550nm L waveband are preferred; the range of the period of the emitted light pulse is 0.1 ms-2 ms, preferably 1 ms; the optical pulse width T ranges from 50ns to 5000ns, preferably 1000 ns. The first optical pulse transmitter and the second optical pulse transmitter do not necessarily have the same optical pulse period and the same optical pulse width, and the first optical pulse transmitter and the second optical pulse transmitter preferably have the same pulse period and the same optical pulse width.
The detectors used by the first optical receiver and the second optical receiver are APDs or PINs.
The length range of the first optical fiber delay line and the second optical fiber delay line is 500-20 km, the length difference delta L of the first optical fiber delay line and the second optical fiber delay line is larger than the optical pulse width T/5, the unit of delta L is m, and the unit of T is ns. In the case where the optical pulse width is 1000ns, the second optical fiber delay line is preferably 2.5km, and the first optical fiber delay line is preferably 5.0 km.
The utility model discloses a concrete implementation method as follows:
after the measurement is started, lightly knocking the optical cable by using a small tool or a finger;
in a first differential phase optical time domain reflectometer, after a first optical pulse transmitter transmits an optical pulse signal every time, a first optical receiver acquires 1 frame of optical fiber backscattering and backscattering signal data Dn; subtracting adjacent data of two frames, namely: delta DK＝DK+1-DK(ii) a It is composed ofMiddle, Δ DKIs a discrete function, the variable of the function is K, and K is a positive integer. Let Y be Δ DKWhere T is the sampling interval of the a/D converter, C is the speed of light in vacuum, n is the effective refractive index of the fiber, and X represents the fiber length. Displaying the signal data sequence Δ D in a curvilinear manner in the XY coordinate axisKThe Y-axis represents the variation of the amplitude of the backscattered signal and the X-axis represents the length of the optical fiber; calculating data sequence delta D by forward point-by-point displacement from coordinate originKWhen signal data sequence Δ DKWhen the Y value is larger than a set threshold Yt, recording the point on the curve, performing point-by-point displacement and calculation from the point to the direction of the origin of coordinates, when the slope of the curve at a certain point on the curve is changed from a positive value to a negative value (or zero), the point corresponds to the vibration position of the optical cable, and the value of the X axis of the point subtracts half of the length value of the first optical fiber delay line, so that the obtained value S1 is the optical fiber length value from the vibration position of the optical cable to the measuring device;
according to the same steps, obtaining an optical fiber optical length value S2 from the vibration position of the optical cable to the measuring device by a second differential phase optical time domain reflectometer;
comparing the magnitudes of S1 and S2, wherein the smaller value of the magnitudes is the optical fiber length value S from the final optical cable vibration position to the measuring device; because S1 and S2 are theoretically the same if S is not within the measurement blind zone, but S1 and S2 are not necessarily the same due to measurement errors due to noise and fiber birefringence, the smaller of S1 and S2 is closer to the true S value; if one of the fiber delay lines is used so that S is within the range of the blind zone, the measured value must be larger than the S value, so that the smaller of S1 and S2 is closer to the true S value excluding the measurement error factor. Therefore, after the two sections of optical fiber delay lines are used for measurement, whether S is in the blind area range or not, the smaller value of S1 and S2 is selected as the measured value, and the measured value can be further ensured to be close to the real S value.
Wherein the value range of Yt is 0.05-0.2 dB.
The utility model also discloses a following technological effect:
the utility model discloses an utilize first differential phase place optical time domain reflectometer and second differential phase place optical time domain reflectometer that operating wavelength is different and optic fibre delay line length is different, make the optic fibre delay line of different length of walking of the signal of different wavelength, and utilize first photoreceiver and second photoreceiver to correspond and obtain the analysis result, compare two results again, screen, thereby eliminate the optical cable vibration location blind area that arouses because of optic fibre Fresnel reflection, carry out the accurate positioning to the vibration position of optical cable.
In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principle and the implementation of the present invention are explained herein by using specific examples, and the above description of the embodiments is only used to help understand the method and the core idea of the present invention; meanwhile, for the general technical personnel in the field, according to the idea of the present invention, there are changes in the concrete implementation and the application scope. In summary, the content of the present specification should not be construed as a limitation of the present invention.
Claims (8)
1. A positioning device for optical cable vibration is characterized by comprising a first differential phase optical time domain reflectometer, a second differential phase optical time domain reflectometer, a wavelength division multiplexer and a measured optical cable;
the working wavelengths of the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer are different;
the first differential phase optical time domain reflectometer comprises a first optical fiber delay line, the second differential phase optical time domain reflectometer comprises a second optical fiber delay line, and the lengths of the first optical fiber delay line and the second optical fiber delay line are different;
the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer are both connected with the wavelength division multiplexer, and the wavelength division multiplexer is also connected with a measured optical cable;
after optical signals transmitted by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer pass through the wavelength division multiplexer and the tested optical cable, a back scattering signal and a reflection signal in the tested optical cable are received by the first differential phase optical time domain reflectometer and the second differential phase optical time domain reflectometer.
2. The apparatus for locating vibration in an optical fiber cable according to claim 1, wherein the first differential phase optical time domain reflectometer comprises:
a first optical pulse transmitter, a first optical receiver, and a first single-axis Sagnac interferometer;
the first optical pulse transmitter, the first single-axis Sagnac interferometer and the first optical receiver are connected in sequence.
3. The apparatus for locating vibration in an optical fiber cable according to claim 2, wherein the second differential phase optical time domain reflectometer comprises:
a second optical pulse transmitter, a second optical receiver, and a second single-axis Sagnac interferometer;
and the second optical pulse transmitter, the second single-axis Sagnac interferometer and the second optical receiver are connected in sequence.
4. The optical cable vibration locating device of claim 1 or 3, wherein the operating wavelengths of the first optical pulse transmitter and the second optical pulse transmitter are any two of 1310nm, 1490nm, 1550nm C band, 1550nm L band and 1625 nm.
5. The apparatus for locating vibration of optical fiber cable according to claim 1, wherein the lengths of the first and second optical fiber delay lines range from 500 to 20 km.
6. The optical cable vibration positioning apparatus as claimed in claim 3, wherein the light source type of the first and second optical pulse transmitters is F-PLD or SLD, the values of the optical pulse periods of the first and second optical pulse transmitters range from 0.1ms to 2ms, and the values of the optical pulse widths of the first and second optical pulse transmitters range from 50ns to 5000 ns.
7. The apparatus for locating vibration in an optical fiber cable according to claim 5, wherein the difference Δ L between the lengths of the first and second optical fiber delay lines is at least greater than T/5, where T is the optical pulse width value, T is in ns, and Δ L is in m.
8. The optical cable vibration positioning apparatus of claim 3, wherein the photodetectors used by the first and second optical receivers are APDs or PINs.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110518969A (en) * | 2019-09-19 | 2019-11-29 | 桂林聚联科技有限公司 | A kind of positioning device and method of optic cable vibration |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110518969A (en) * | 2019-09-19 | 2019-11-29 | 桂林聚联科技有限公司 | A kind of positioning device and method of optic cable vibration |
| CN110518969B (en) * | 2019-09-19 | 2024-01-16 | 桂林聚联科技有限公司 | Optical cable vibration positioning device and method |
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