CN115459841A

CN115459841A - Optical fiber detection method and related device

Info

Publication number: CN115459841A
Application number: CN202210970203.8A
Authority: CN
Inventors: 杨智生; 洪小斌; 伍剑; 张倩
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2022-08-12
Filing date: 2022-08-12
Publication date: 2022-12-09

Abstract

The application provides an optical fiber detection method and related equipment, firstly splitting a preset light source with a line width smaller than a preset line width to obtain a first test light source and local oscillation light; broadening the line width of the first test light source through phase modulation to obtain a second test light source; presetting a corresponding preset pulse width before splitting the preset light source with the line width smaller than the preset line width, and setting the coherence length of the second test light source to be smaller than the preset pulse width; performing acousto-optic modulation on the second test light source to obtain a third test light source; then injecting the third test light source into the optical fiber to be tested, and determining Rayleigh scattering light of the optical fiber to be tested; and finally, coupling the Rayleigh scattered light with the local oscillator light, detecting an output signal of the coupled Rayleigh scattered light and the local oscillator light, and obtaining a conclusion that the optical fiber link length is longer and the signal-to-noise ratio is higher compared with the optical fiber link length measured by the method in the related art according to a detection result.

Description

Optical fiber detection method and related device

Technical Field

The present invention relates to the field of optical fiber detection, and in particular, to a method and an apparatus for measuring a functional state of an optical fiber by using rayleigh scattering light of a broadened light source, an electronic device, and a storage medium.

Background

An Optical Time Domain Reflectometer (OTDR) is an Optical fiber testing instrument, and is widely applied to attenuation measurement of an Optical fiber link, quality inspection of an Optical fiber connector and an Optical fiber fusion point, optical fiber defect inspection, and Optical fiber failure detection, and can measure the Optical length of an Optical fiber and analyze physical parameters such as loss distribution of the entire Optical fiber link.

The traditional direct detection OTDR measures the transmission time difference and signal intensity variation between a pulse signal injected into an optical fiber and a backward rayleigh scattering signal and a fresnel reflection signal to realize analysis of the length of an optical fiber link, the loss of an optical fiber line and the like, but the traditional direct detection OTDR has the problems that the backward rayleigh scattering signal light is too weak and a direct detection mode is adopted, so that the received signal-to-noise ratio is small, and the measured length of the optical fiber link is limited. Another problem is that coherent detection techniques cannot be used to improve the signal-to-noise ratio. The reason is that the spectral width of the signal frequency domain of the rayleigh scattered light after coherent detection is the convolution of the light source line width and the pulse spectrum, and the detector bandwidth is determined by the pulse width and is the reciprocal of the pulse width. At the moment, the spectral width of the signal frequency domain is far greater than the bandwidth of the detector, so most of energy is outside the bandwidth of the detector, the spectral utilization efficiency is extremely low, the signal power is low, and the purpose of improving the signal-to-noise ratio cannot be achieved.

Disclosure of Invention

In view of the above, the present application is directed to a method, an apparatus, an electronic device and a storage medium for optical fiber detection, so as to solve or partially solve the above technical problems.

In view of the above, a first aspect of the present application provides a method for optical fiber detection, the method comprising:

splitting a preset light source with a line width smaller than a preset line width to obtain a first test light source and local oscillation light;

broadening the line width of the first test light source through phase modulation to obtain a second test light source;

presetting a corresponding preset pulse width before splitting the preset light source with the line width smaller than the preset line width, and setting the coherence length of the second test light source to be smaller than the preset pulse width;

performing acousto-optic modulation on the second test light source to obtain a third test light source;

injecting the third test light source into the optical fiber to be tested, and determining Rayleigh scattered light of the optical fiber to be tested;

and coupling the Rayleigh scattered light with the local oscillator light, and detecting an output signal of the coupled Rayleigh scattered light and the local oscillator light.

A second aspect of the present application proposes an apparatus for optical fiber detection, the apparatus comprising:

the light source line width widening module is configured to split a preset light source with a line width smaller than a preset line width to obtain a first test light source and local oscillator light; broadening the line width of the first test light source through phase modulation to obtain a second test light source; presetting a corresponding preset pulse width before splitting the preset light source with the line width less than the preset line width, and setting the coherence length of the second test light source to be less than the preset pulse width;

the modulation module is configured to perform acousto-optic modulation on the second test light source to obtain a third test light source;

the rayleigh scattering light detection module is configured to input the third test light source into an optical fiber to be tested and determine rayleigh scattering light of the optical fiber to be tested; and coupling the Rayleigh scattering light with the local oscillator light, and detecting an output signal of the coupled Rayleigh scattering light and local oscillator light.

A third aspect of the present application proposes an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method of the first or second aspect when executing the program.

A fourth aspect of the present application proposes a non-transitory computer-readable storage medium storing computer instructions for causing a computer to perform the method of the first or second aspect.

It can be seen from the above that, according to the optical fiber detection method, the apparatus, the electronic device, and the storage medium provided in the present application, the light source is broadened on the basis of the coherent detection method to obtain the light source with broadened line width, which can solve the problems that in the conventional direct detection system, rayleigh scattered light scattered by the optical fiber to be detected is too weak due to too narrow line width of the light source caused by direct detection, and the length of the optical fiber link to be detected is limited due to low signal-to-noise ratio of the output signal, and that some points with low light intensity exist in the interference pattern obtained in the conventional coherent detection Φ -OTDR system and the state of the optical fiber to be detected cannot be directly represented.

Drawings

In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for the embodiments or related technologies in the following description are briefly introduced, and it is obvious that the drawings in the following description are only the embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic view of a related art;

FIG. 2 is a schematic diagram of a related art test curve;

FIG. 3 is a schematic flowchart of an optical fiber detection method according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a fiber optic detection method according to an embodiment of the present application;

FIG. 5 is a schematic diagram illustrating comparison between a broadened line width of a light source according to an embodiment of the present disclosure;

FIG. 6 is a schematic structural diagram of an optical fiber detection apparatus according to an embodiment of the present application;

fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to specific embodiments and the accompanying drawings.

It is to be noted that technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which the embodiments of the present invention belong, unless otherwise defined. The use of "first," "second," and similar terms in the embodiments of the present application is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

The OTDR is an important instrument recommended by standards such as Telecommunications Industry Association (TIA) and International Electrotechnical Commission (IEC) to authenticate performance of a new optical fiber link and detect problems of an existing optical fiber link, has the advantages of simple implementation, low price, high test speed, high test precision and the like, is as important as a universal meter for production and debugging of electronic products in construction and maintenance of optical fiber cables and occasions related to optical fibers, and thus is widely concerned and favored by manufacturers at home and abroad.

Due to factors such as non-uniform fiber structure, manufacturing defects of the fiber itself, and non-uniform doping distribution inside the fiber, rayleigh scattering signals in various directions are generated when an optical pulse propagates through the fiber. The phenomenon that a signal scattered in the opposite direction of propagation of an optical signal is called rayleigh backscattering, and the optical signal generates a reflected signal at the end face of the optical fiber is called fresnel reflection. The OTDR is an instrument for implementing analysis of optical fiber link length, optical fiber line loss, etc. by measuring the transmission time difference between a pulse signal injected into an optical fiber and a backward rayleigh scattering, fresnel reflection signal, and signal intensity variation.

The infrastructure of a conventional direct probing OTDR is shown in fig. 1. The light source (Laser) is internally modulated to generate light pulses, and the light pulses are injected into the optical fiber to be tested through the circulator (Cir), wherein the pulse interval is large enough to ensure that the previous pulse leaves when the next pulse enters the optical fiber to be tested (FUT). The backward optical signal that the optic fibre that awaits measuring returns is exported by Photoelectric Detector (PD) and is received through circulator, and the signal reception device (Acq) that generates includes: the amplifier amplifies and converts to digital signals by analog-to-digital converter (ADC) which are sent to signal control and processing unit. The signal control and processing unit is responsible for maintaining the clock synchronization of the whole system and triggering the pulse generator on one hand; on the other hand, the intensity of the optical signal returned to the receiving end at different moments is recorded, average calculation and logarithmic transformation are executed, the obtained result is used as a vertical coordinate, the time unit is converted into a distance unit and then used as a horizontal coordinate, and the loss curves of different scattering positions can be drawn.

The light source of a conventional direct detection OTDR is typically a broadband light source, with a bandwidth of about 2nm, so the measured power-time curve is relatively smooth, as shown in fig. 2, where the horizontal axis is distance and the vertical axis shows signal loss in dB. The OTDR curve can accurately position the position of a connector, a joint or a fracture in a link, and obtain the attenuation coefficient, the length and the refractive index of an optical fiber, the insertion loss, the return loss and other parameters of the connector. The types of events in the OTDR plot can be mainly classified into reflection events, non-reflection events and gain events: reflection events show up as spikes in the fiber curve, indicating that there may be connectors, mechanical splices, and even poor fusion splices or cracks; non-reflection events appear as discontinuities in the slope of the falling curve signal, typically caused by splices, macrobends or microbends in the fiber; the gain event shows that the power level at a certain point is obviously increased, which indicates that two jointed optical fibers have different backscattering characteristics, and the latter optical fiber generates more backscattering light and is often appeared at a welding point and other positions.

With conventional direct detection OTDR systems, the functional state of the fiber can be detected, which includes two main states, strong reflection and attenuation. These two conditions affect the quality of the transmitted signal in the optical fiber, leading to an increased error rate of the communication, and are therefore of major concern.

In the conventional direct detection OTDR, analysis such as optical fiber link length and optical fiber line loss is realized by measuring a transmission time difference between a pulse signal injected into an optical fiber and a backward rayleigh scattering signal, a fresnel reflection signal and a signal intensity change, but because the backward rayleigh scattering signal light in the OTDR is too weak and a direct detection method is adopted, a received signal-to-noise ratio is small, and the measured optical fiber link length is limited. An optical pulse with a pulse width of 20us and a peak power of 15dBm is taken as an example for analysis, the length of a measured optical fiber link is 50km, the scattering rate of backward Rayleigh scattering light is known to be-73 dB/m, the Rayleigh scattering light received by a detection end is attenuated by 0.4dB/km, the power of the Rayleigh scattering light at the starting end of the optical fiber is-25 dBm, the total attenuation power of the whole optical fiber link is 20dB, and the power of the Rayleigh scattering light at the tail end of the optical fiber is-45 dBm. If the signal-to-noise ratio of the received tail rayleigh scattered light is required to be 6dB, that is, the rayleigh scattered signal is 4 times larger than the noise, the noise is required to be less than-51 dBm, which is lower than the noise power of a general detector, and is difficult to realize.

Another problem with conventional direct detection OTDR systems is that coherent detection techniques cannot be used to improve the signal-to-noise ratio. The reason is that the spectral width of the signal frequency domain of the Rayleigh scattering light after coherent detection is the convolution of the light source line width and the pulse spectrum, and the detector bandwidth B _c The pulse width is determined by the reciprocal of the pulse width. When the spectral width of the signal frequency domain is far larger than the bandwidth B of the detector _c Most of energy is outside the bandwidth of the detector, so that the frequency spectrum utilization efficiency is extremely low, the signal power is low, and the purpose of improving the signal-to-noise ratio cannot be achieved.

In conventional coherent sounding Φ -OTDR systems, however, since our objective is to detect the functional states of the fiber, two main states are strong reflection and attenuation. Because the traditional coherent detection phi-OTDR system adopts a narrow linewidth light source with strong coherence, an intensity fluctuation curve can be caused on an interference pattern, so that the intensity of some position points is very low, and the attenuation rate or the reflection value of an optical fiber cannot be directly represented.

Based on the above situation, the embodiments of the present application provide an optical fiber detection method, apparatus, electronic device, and storage medium. Compared with the traditional direct detection OTDR, the optical fiber detection method can increase the length of the measured optical fiber link, improve the signal to noise ratio of a detection signal and solve the problem of poor performance when the traditional direct detection OTDR monitors the optical fiber link.

Referring to fig. 3, a schematic flow chart of an optical fiber detection method according to an embodiment of the present application is shown.

As shown in fig. 3, the present embodiment provides a method for detecting an optical fiber, the method including:

step 301, splitting a preset light source with a line width smaller than a preset line width to obtain a first test light source and local oscillation light.

In the step, a preset light source with a line width smaller than a preset line width is split through a coupler, one light source is split into a first test light source and two local oscillator light beams, and the center frequencies of the two light signals are f ₀ 。

In the above process, a preset light source smaller than a preset line width is split to obtain a first test light source and a local oscillator light, wherein the first test light source transmitted to the phase modulator for processing is mainly used for preparing a finally obtained rayleigh scattered light, and the other path of local oscillator light is transmitted downwards, which is used for preparing coherent detection.

Step 302, broadening the line width of the first test light source through phase modulation to obtain a second test light source; and presetting a corresponding preset pulse width before splitting the preset light source with the line width less than the preset line width, and setting the coherence length of the second test light source to be less than the preset pulse width.

In this step, the first test light source is phase-modulated in a certain way to broaden the line width thereof, and finally, the second test light source is obtained, and when the line width of the light source is broadened, the broadening degree of the line width is not as wide as possible, and too wide may cause that when a photodetector is subsequently used to receive a signal, the frequency spectrum of the signal is far greater than the bandwidth of the photodetector, so that most of the energy cannot be received by the photodetector, and it is very important to set the coherence length of the second test light source to be smaller than the preset pulse width.

In the process, the second test light source with the broadened line width lays a foundation for a third test light source for optical fiber detection, and the problem that the strength of some position points is low due to Rayleigh scattering light intensity fluctuation of the optical fiber to be detected caused by too narrow line width of the third test light source input into the optical fiber to be detected if coherent detection is carried out is solved.

And 303, performing acousto-optic modulation on the second test light source to obtain a third test light source.

In this step, when the second test light source is subjected to the acousto-optic modulation by the acousto-optic modulator, the center frequency and the light source type of the second test light source are both changed, at this time, the center frequency of the light source subjected to the acousto-optic modulation is shifted to be the sum of the center frequency of the second test light source and the modulation frequency of the acousto-optic modulator, and the third test light source type is changed into a light source capable of entering the optical fiber to be tested.

In the above process, the third test light source is prepared for inputting the light source into the optical fiber for detection, the light source type is changed into the light source capable of entering the optical fiber to be detected, and the change of the center frequency is related to the property of the acousto-optic modulator.

And 304, injecting the third test light source into the optical fiber to be tested, and determining the Rayleigh scattered light of the optical fiber to be tested.

In this step, a third test light source is driven into the optical fiber to be tested through the circulator, and the optical fiber to be tested scatters the rayleigh scattered light back and then outputs from the circulator. At this time, the center frequency of the rayleigh scattered light signal output from the circulator is the sum of the center frequency of the second test light source and the modulation frequency of the acousto-optic modulator, and the frequency spectrum is the convolution of the third test light source line width and the third test light source pulse frequency spectrum. At this time, the task of detecting the optical fiber to be detected by the upper path light is basically completed.

According to the above process, the part is mainly the transmission process of the light source, and the light source is transmitted through the circulator.

And 305, coupling the rayleigh scattered light with the local oscillator light, and detecting an output signal after the rayleigh scattered light is coupled with the local oscillator light.

In this step, the local oscillator light obtained in step 301 and the rayleigh scattered light output in step 304 are combined by a coupler to obtain an output signal and detected, where the detection process includes conversion of an optical signal and an electrical signal and signal control and processing of the signal after entering a receiving device.

According to the above scheme, the local oscillator light obtained in step 301 and the rayleigh scattered light output in step 304 are combined by the coupler, which mainly plays a role of amplifying light intensity, and indirectly improves the signal-to-noise ratio of the output signal output in this step. The detection comprises the conversion of optical signals and electric signals and the signal control and processing of the signals after the signals enter a receiving device.

In some embodiments, prior to step 301, the method further comprises:

the value of the preset pulse width is predetermined before splitting the preset light source, and the size of the preset pulse width is determined by the user's requirement for the spatial resolution of the system, for example: a pulse width of 20ns corresponds to a system spatial resolution of 2 m. Wherein the system spatial resolution refers to the resolution of the smallest distance that is actually detectable.

In some embodiments, step 302 comprises:

step 3021, disturbing the phase of the first test light source by using a pseudo-random binary sequence, and widening the line width to obtain a second test light source.

In specific implementation, a phase modulator driven by a pseudo-random binary sequence can be adopted to widen the line width of the light source.

According to the scheme, the line width of the light source is widened through the phase modulator driven by the pseudo-random binary sequence to obtain the second test light source, and at the moment, the line width of the second test light source is in direct proportion to the bit rate of the pseudo-random binary series.

In some embodiments, step 303 specifically includes:

step 3031, modulating the center frequency of the second test light source.

3032, determining the electric pulse required by the acousto-optic modulation according to the preset pulse width; and modulating the second test light source into pulse light according to the electric pulse to obtain the third test light source, wherein the pulse width of the pulse light is the preset pulse width.

In specific implementation, before performing the acousto-optic modulation, the level of the electrical pulse required for the electro-optic modulation needs to be set according to the preset value of the preset pulse width, and the high level of the optical pulse is generated according to the high level corresponding to the electrical pulse, so that the pulse width of the third test light source also obtains the value of the preset pulse width at the beginning. When acousto-optic modulation is carried out, frequency modulation is carried out on the second test light source, the center frequency of the obtained third test light source is slightly different from that of the second test light source, and the value of the center frequency is changed into f ₀ +f _AOM Wherein f is ₀ Is the center frequency, f, of the second test light source _AOM The line width of the light source is not changed in the modulation process for the modulation frequency of the acousto-optic modulator. The light source type is changed from continuous light into pulse light entering the optical signal of the optical fiber to be measured.

In the above scheme, the second test light source has changed the center frequency and the light source type due to the property of the acousto-optic modulator, and when performing optical fiber detection, the use of pulsed light has the advantage of easier signal processing and analysis of subsequent output signals.

In some embodiments, step 305 further comprises:

step 3051, converting the optical signal and the electrical signal to the output signal by using a photoelectric detector to obtain a detection signal.

Step 3052, determining a test curve of the detection signal.

And 3053, detecting the optical fiber to be detected according to the obtained test curve of the detection signal.

In specific implementation, the center frequency of the local oscillator light is known to be f ₀ Center frequency of Rayleigh scattered light is f ₀ +f _AOM After beat frequency is carried out in the photoelectric detector, the known center frequency f is obtained _AOM The electrical signal of (a) is the detection signal. The shape and width of the spectrum of the detection signal are the same as those of the rayleigh scattered light mentioned above, and only the center frequency is locatedA change in position. Therefore, it can be said that the signal analysis of the detection signal represents the analysis of the rayleigh scattered light, that is, the detection result of the optical fiber. The detection signal is detected to obtain a test curve, and the functional state of the optical fiber to be measured and the measured length of the optical fiber link to be measured can be obtained according to the characteristic analysis of the test curve.

In the above scheme, the process of transmitting the output signal into the photoelectric detector is the process of converting the optical signal and the electrical signal, and the test curve of the detection signal can be obtained by converting the optical signal into the electrical signal and then processing and analyzing the signal by using the following receiving device, so that the functional state of the optical fiber to be tested and the link length of the optical fiber to be tested can be clearly determined.

In some embodiments, before step 3051, the method further includes setting a bandwidth of the photodetector to be equal to or greater than a full width at half maximum of a spectrum in which the line width of the third test light source is convolved with the pulse spectrum of the third test light source, to obtain the photodetector.

In specific implementation, the implementation manner may be that, first, a first target spectrum obtained by convolving a line width of a third test light source with a pulse spectrum of the third test light source is determined, and then, after the first target spectrum is subjected to a coherent detection process, a modulation frequency f with a center frequency shifted to the acousto-optic modulator is obtained _AOM And finally, setting the bandwidth of the photodetector to be equal to or greater than the full width half maximum of the second target spectrum. In one embodiment, the bandwidth of the photodetector is directly set to be equal to or greater than a full width at half maximum of a frequency spectrum obtained by convolving a line width of the third test light source with a pulse frequency spectrum of the third test light source, so as to obtain the photodetector.

In general, coherent detection includes three parts, first splitting a preset light source smaller than a preset line width by a coupler to obtain a first test light source and a local oscillator, then coupling the local oscillator with Rayleigh scattering light transmitted on the upper path to obtain an output signal, and finally performing beat frequency on the output signal by a photoelectric detector to obtain a signal center frequency f _AOM The detection signal of (c). The coherent detection process in the above scheme mainly includes a process of coupling the local oscillation light and the rayleigh scattered light and then performing beat frequency by the photoelectric detector; in addition, the bandwidth of the photoelectric detector needs to be more than or equal to the full width at half maximum of the convolution of the third test light source line width and the third test light source pulse frequency spectrum, namely the full width at half maximum of the Rayleigh scattering light signal frequency spectrum, the above conditions ensure that the photoelectric detector can receive all the energy of the output signal, the problem that the full energy of the output signal cannot be received due to the fact that the bandwidth of the photoelectric detector is too small is avoided, and the signal-to-noise ratio of the signal cannot be reduced in the process.

In some embodiments, step 3052 specifically includes:

step 30521, determining the relative power of the rayleigh scattered light and the distance of the optical fiber to be detected corresponding to each sampling time according to the detection signal;

step 30522, determining the test curve according to the relative power and the distance of the optical fiber to be tested.

In specific implementation, the detection signal is analyzed to obtain the change of the power of the rayleigh scattering signal amplified by coherent detection along the distance of the optical fiber, that is, a series of processing such as squaring and filtering is performed on the rayleigh scattering beat signal, and finally the relative power of the detection signal is obtained. And then, drawing a test curve by taking the optical fiber distance corresponding to each sampling time as an abscissa and taking the relative power of the detection signal as an ordinate.

In the scheme, the position of the connector, the joint or the fracture part in the optical fiber link to be tested can be accurately positioned through the drawn test curve, and the attenuation coefficient, the length and the refractive index of the optical fiber, the insertion loss, the return loss and other parameters of the connector are obtained. And determining the event type according to the curve, wherein the event type comprises a reflection event, a non-reflection event and a gain event.

In order to more clearly illustrate the technical solution of the embodiment of the present application, the embodiment of the present application may also be described in more detail:

because the coherent detection phi-OTDR system of the related art has the problem that the light intensity of some points on an interference pattern is very low, and the attenuation rate or the reflection value of an optical fiber cannot be directly represented, on the basis, a laser source with a line width needs to be widened, namely, the process of widening a first test light source to obtain a second test light source is needed, so that the coherence length of the second test light source is smaller than the preset pulse width, and the phenomenon of fluctuation and fluctuation of the light intensity is eliminated. An example of the present application is shown in fig. 4, in which a phase modulator module driven by a Pseudo Random binary Sequence (PRBS for short) is added on the basis of a conventional coherent sounding Φ -OTDR system. The line width broadening degree of the light source is determined by the preset pulse width, only the coherence length of the second test light source obtained after phase modulation is required to be smaller than the preset pulse width, and the broadening is not required, otherwise, the phenomenon that most energy cannot be received by the preset photoelectric detector occurs in subsequent output signals, so that the spectrum utilization rate is extremely low, and the signal-to-noise ratio of the output signals is low.

In FIG. 4, the narrow linewidth laser output center frequency is f ₀ Line width of Δ v ₀ The continuous light is divided into two paths by the coupler, after the phase of the light on the upper path is disturbed by the pseudorandom binary sequence, the line width of the broadening light source is in direct proportion to the bit rate of the pseudorandom binary sequence and is delta v ₁ . Taking fig. 5 as an example, the left image is a narrow linewidth light source without PRBS code perturbation phase, the linewidth of which is about 1.4MHz; the right image is a light source of a specific extended linewidth, about 40MHz, perturbed by a PRBS code of 50 Mbps.

The passing frequency of the second test light source with the broadened line width is f _AOM The acousto-optic modulator performs acousto-optic modulation to obtain the central frequency f ₀ +f _AOM Line width of Deltav ₁ The pulse light of (1) is injected into the optical fiber to be tested by the third test light source, and the spectral width of the frequency domain of the received Rayleigh scattering light is related to the line width and the pulse width of the third test light source. The center frequency of the other path of local oscillator light is f _Lo ＝f ₀ . The local oscillator light and the Rayleigh scattered light on the upper path enter the photoelectric detector for beat frequency after being combined by the coupler, and after the direct current component of the signal light after beat frequency is removed, the central frequency is f _AOM To (3). The spectral width of the signal frequency domain of the Rayleigh scattered light after the light source with specific extended line width is subjected to coherent detection is the convolution of the line width of the light source and the pulse frequency spectrum, so the bandwidth B of the photoelectric detector _c It needs to be larger than the full width at half maximum (FWHM) of the spectrum.

Compared with the traditional direct detection OTDR of the related art, the method has higher signal-to-noise ratio under the conditions of the same measurement time, the same measurement precision and the same spatial resolution. And analyzing by taking an optical pulse with the pulse width of 20us and the peak power of 15dBm as an example, setting the length of the optical fiber link to be detected to be 50km, knowing that the scattering rate of backward Rayleigh scattering light is-73 dB/m, and attenuating the Rayleigh scattering light received by the detection end by 0.4dB/km, wherein the Rayleigh scattering light power of the initial end of the optical fiber is-25 dBm, the total attenuation power of the whole optical fiber link is 20dB, and the Rayleigh scattering light power of the tail end of the optical fiber is-45 dBm. With a probe bandwidth B _c For example of 350MHz, under the direct detection condition, the signal light power is-45 dBm, the thermal noise is dominant at this time, the noise power is about-34 dBm, the signal-to-noise ratio is-11 dB, and the rayleigh scattering signal at the tail end cannot be detected; under the condition of coherent detection, taking local oscillator light of 5dBm as an example, the signal light after beat frequency is-20 dBm, at the moment, shot noise is dominant, the noise power is about-32 dBm, the signal-to-noise ratio is 12dB, and the signal-to-noise ratio is improved by 23dB compared with the traditional OTDR (optical time domain reflectometer) scheme under the same condition, so that the application embodiment brings higher signal-to-noise ratio and longer measurement distance compared with the related technology, namely, the better measurement performance is realized.

Based on the same inventive concept, the application also provides an optical fiber detection device corresponding to the method of any embodiment.

The optical fiber detection device described with reference to fig. 6 includes:

the light source line width widening module 601 is configured to split a preset light source with a line width smaller than a preset line width to obtain a first test light source and local oscillator light; broadening the line width of the first test light source through phase modulation to obtain a second test light source; presetting a corresponding preset pulse width before splitting the preset light source with the line width smaller than the preset line width, and setting the coherence length of the second test light source to be smaller than the preset pulse width;

a modulation module 602 configured to perform acousto-optic modulation on the second test light source to obtain a third test light source;

a rayleigh scattered light detection module 603 configured to inject the third test light source into the optical fiber to be tested and determine rayleigh scattered light of the optical fiber to be tested; and coupling the Rayleigh scattered light with the local oscillator light, and detecting an output signal of the coupled Rayleigh scattered light and the local oscillator light.

In some embodiments, the apparatus further comprises:

a detector setting module configured to set a bandwidth of the photodetector to be equal to or greater than a full width at half maximum of a spectrum in which a line width of the third test light source is convolved with a pulse spectrum of the third test light source, resulting in the photodetector.

In some embodiments, the light source linewidth broadening module 601 specifically includes:

the phase perturbation unit is configured to perturb the phase of the first test light source by using a pseudo-random binary sequence and widen the line width to obtain a second test light source;

a line width determination unit configured to set a coherence length of the second test light source to be less than the preset pulse width.

In some embodiments, the modulation module 602 specifically includes:

a center frequency modulation unit configured to modulate a center frequency of the second test light source;

the light source type modulation unit is configured to determine an electric pulse required for performing the acousto-optic modulation according to the preset pulse width; and modulating the second test light source into pulse light according to the electric pulse to obtain a third test light source, wherein the pulse width of the pulse light is the preset pulse width.

In some embodiments, the rayleigh scattered light detection module 603 specifically includes:

a Rayleigh scattered light determination unit configured to inject the third test light source into an optical fiber to be tested and determine Rayleigh scattered light of the optical fiber to be tested;

the coupling unit is configured to couple the Rayleigh scattering light with the local oscillator light to obtain an output signal;

a first detection unit configured to convert the output signal into an optical signal and an electrical signal by a photodetector to obtain a detection signal;

a second detection unit configured to determine a test curve of the detection signal; and detecting the optical fiber to be detected according to the obtained test curve of the detection signal.

In some embodiments, the second detection unit specifically includes:

a detection signal detection subunit configured to determine, according to the detection signal, the relative power of the rayleigh scattered light and the distance of the optical fiber under test corresponding to each sampling time;

and the test curve determining subunit determines the test curve according to the relative power and the distance of the optical fiber to be tested.

For convenience of description, the above devices are described as being divided into various modules by functions, which are described separately. Of course, the functionality of the various modules may be implemented in the same one or more pieces of software and/or hardware in the practice of the present application.

The apparatus of the foregoing embodiment is used to implement the corresponding optical fiber detection method in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiment, which are not described herein again.

Based on the same inventive concept, corresponding to the method of any embodiment described above, the present application further provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the program, the optical fiber detection method described in any embodiment above is implemented.

Fig. 7 is a schematic diagram of a more specific hardware structure of an electronic device provided in this embodiment, where the electronic device may include: a processor 710, a memory 720, an input/output interface 730, a communication interface 740, and a bus 750. Wherein processor 710, memory 720, input/output interface 730, and communication interface 740 are communicatively coupled to each other within the device via bus 750.

The processor 710 may be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits, and is configured to execute related programs to implement the technical solutions provided in the embodiments of the present disclosure.

The Memory 720 may be implemented in the form of a ROM (Read Only Memory), a RAM (Random Access Memory), a static storage device, a dynamic storage device, or the like. The memory 720 may store an operating system and other application programs, and when the technical solutions provided by the embodiments of the present specification are implemented by software or firmware, the relevant program codes are stored in the memory 720 and called to be executed by the processor 710.

The input/output interface 730 is used for connecting an input/output module to realize information input and output. The i/o module may be configured as a component within the device (not shown) or may be external to the device to provide corresponding functionality. The input devices may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output devices may include a display, a speaker, a vibrator, an indicator light, etc.

The communication interface 740 is used for connecting a communication module (not shown in the figure) to implement communication interaction between the present device and other devices. The communication module can realize communication in a wired mode (such as USB, network cable and the like) and also can realize communication in a wireless mode (such as mobile network, WIFI, bluetooth and the like).

Bus 750 includes a path that transfers information between various components of the device, such as processor 710, memory 720, input/output interface 730, and communication interface 740.

It should be noted that although the above-described device only shows the processor 710, the memory 720, the input/output interface 730, the communication interface 740, and the bus 750, in a specific implementation, the device may also include other components necessary for normal operation. In addition, those skilled in the art will appreciate that the above-described apparatus may also include only those components necessary to implement the embodiments of the present description, and not necessarily all of the components shown in the figures.

The electronic device of the foregoing embodiment is used to implement the corresponding game user distribution method in any one of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiment, which are not described herein again.

Based on the same inventive concept, corresponding to any of the above-mentioned embodiment methods, the present application further provides a non-transitory computer-readable storage medium storing computer instructions for causing the computer to execute the game user shunting method according to any of the above-mentioned embodiments.

Computer-readable media, including both permanent and non-permanent, removable and non-removable media, for storing information may be implemented in any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Disks (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device.

The computer instructions stored in the storage medium of the above embodiment are used to enable the computer to execute the game user distribution method according to any one of the above embodiments, and have the beneficial effects of the corresponding method embodiment, which are not described herein again.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the context of the present application, technical features in the above embodiments or in different embodiments may also be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present application described above, which are not provided in detail for the sake of brevity.

In addition, well-known power/ground connections to Integrated Circuit (IC) chips and other components may or may not be shown in the provided figures for simplicity of illustration and discussion, and so as not to obscure the embodiments of the application. Furthermore, devices may be shown in block diagram form in order to avoid obscuring embodiments of the application, and this also takes into account the fact that specifics with respect to implementation of such block diagram devices are highly dependent upon the platform within which the embodiments of the application are to be implemented (i.e., specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the application, it should be apparent to one skilled in the art that the embodiments of the application can be practiced without, or with variation of, these specific details. Accordingly, the description is to be regarded as illustrative instead of restrictive.

While the present application has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. For example, other memory architectures, such as Dynamic RAM (DRAM), may use the discussed embodiments.

The present embodiments are intended to embrace all such alternatives, modifications and variances which fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalents, improvements, and the like that may be made without departing from the spirit or scope of the embodiments of the present application are intended to be included within the scope of the claims.

Claims

1. An optical fiber detection method, comprising:

presetting a corresponding preset pulse width before splitting the preset light source with the line width less than the preset line width, and setting the coherence length of the second test light source to be less than the preset pulse width;

and coupling the Rayleigh scattering light with the local oscillator light, and detecting an output signal of the coupled Rayleigh scattering light and local oscillator light.

2. The method of claim 1, wherein broadening the linewidth of the first test light source by phase modulation to obtain a second test light source comprises:

and disturbing the phase of the first test light source by using a pseudo-random binary sequence, widening the line width, and obtaining a second test light source.

3. The method of claim 1, wherein said acousto-optically modulating said second test light source to obtain a third test light source comprises:

modulating a center frequency of the second test light source;

determining the electric pulse required by the acousto-optic modulation according to the preset pulse width;

and modulating the second test light source into pulse light according to the electric pulse to obtain a third test light source, wherein the pulse width of the pulse light is the preset pulse width.

4. The method according to claim 1, wherein after detecting the output signal after the rayleigh scattering light is coupled with the local oscillator light, further comprising:

converting the optical signal and the electric signal of the output signal through a photoelectric detector to obtain a detection signal;

determining a test curve of the detection signal;

and detecting the optical fiber to be detected according to the obtained test curve of the detection signal.

5. The method of claim 4, wherein the converting the output signal into the optical signal and the electrical signal by the photodetector comprises:

and setting the bandwidth of the photoelectric detector to be more than or equal to the full width at half maximum of the frequency spectrum of convolution of the line width of the third test light source and the pulse frequency spectrum of the third test light source, and obtaining the photoelectric detector.

6. The method of claim 4, wherein the test profile of the probe signal comprises:

determining the relative power of the Rayleigh scattered light and the distance of the optical fiber to be detected corresponding to each sampling time according to the detection signal;

and determining the test curve according to the relative power and the distance of the optical fiber to be tested.

7. An optical fiber detection device, comprising: the device comprises a light source line width widening module, a modulation module and a Rayleigh scattering light detection module;

the light source line width widening module is configured to split a preset light source with a line width smaller than a preset line width to obtain a first test light source and local oscillator light; broadening the line width of the first test light source through phase modulation to obtain a second test light source; presetting a corresponding preset pulse width before splitting the preset light source with the line width smaller than the preset line width, and setting the coherence length of the second test light source to be smaller than the preset pulse width;

the rayleigh scattered light detection module is configured to inject the third test light source into the optical fiber to be tested and determine rayleigh scattered light of the optical fiber to be tested; and coupling the Rayleigh scattering light with the local oscillator light, and detecting an output signal of the coupled Rayleigh scattering light and local oscillator light.

8. The apparatus of claim 7, further comprising: a detector setting module;

the detector setting module is configured to set a bandwidth of the photodetector to be equal to or greater than a full width at half maximum of a frequency spectrum obtained by convolution of a line width of the third test light source and a pulse frequency spectrum of the third test light source, so as to obtain the photodetector.

9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method of any one of claims 1 to 6 when executing the program.

10. A non-transitory computer readable storage medium storing computer instructions for causing a computer to perform the method of any one of claims 1 to 6.