Optical time domain reflectometer and control method of optical time domain reflectometer

Abstract

The invention relates to an optical time domain reflectometer and a control method of the optical time domain reflectometer, and relates to the technical field of photoelectricity. The optical time domain reflectometer OTDR comprises a single photon detector, and the OTDR is used for being connected with an optical fiber to be measured; the OTDR is further used for sending a plurality of detection signals to the optical fiber to be detected in sequence and receiving a plurality of detection echo signals from the optical fiber to be detected in sequence, and the detection echo signals are used for indicating the transmission state of the same section of transmission area in the optical fiber to be detected; performing amplitude reduction processing on each detection echo signal at a certain time interval to obtain a processed detection echo signal; the positions, corresponding to the same section of transmission area, of the signal sections subjected to amplitude reduction processing in the different processed detection echo signals are not completely the same; each processed detection echo signal is subjected to photoelectric conversion based on the single-photon detector to obtain a first electric signal, a first OTDR oscillogram is output based on the multiple first electric signals, and the first OTDR oscillogram is used for indicating the transmission state of the same section of transmission area. Therefore, the problem of OTDR curve distortion can be solved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of optoelectronic technology, and in particular to an optical time domain reflectometer and a control method of the optical time domain reflectometer. BACKGROUND

[0002] An optical time domain reflectometer (OTDR) can be applied to scenarios such as optical fiber detection and pipeline detection. The OTDR sends a probe signal to a to-be-detected optical fiber, receives a return signal from the to-be-detected optical fiber, and the return signal is a return signal generated by the probe signal being transmitted by the to-be-detected optical fiber. The OTDR analyzes the backscattering and Fresnel reflection of the return signal, thereby measuring the length of the optical fiber, the optical transmission loss, and the joint loss, and positioning the fault point. The detector in the OTDR can be a single photon avalanche detector (SPAD), which can detect weak optical signals at the single photon power level. Even if the return signal is weak due to distance and is only in the single photon state, it can still be detected by the SPAD. Therefore, the single photon detector has high measurement accuracy and range. However, the single photon detector has a dead time. If there is a strong reflection point in the to-be-detected optical fiber, the single photon detector will be blinded, causing the OTDR curve to be distorted. SUMMARY

[0003] Embodiments of the present application provide an optical time domain reflectometer and a control method of the optical time domain reflectometer, which solve the problem of curve distortion of the optical time domain reflectometer in the prior art.

[0004] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0005] In a first aspect, an optical time domain reflectometer (OTDR) is provided. The OTDR includes a single photon detector, and the OTDR is configured to be connected to a to-be-detected optical fiber. The OTDR is further configured to: sequentially send a plurality of probe signals to the to-be-detected optical fiber, and sequentially receive a plurality of probe return signals from the to-be-detected optical fiber, the plurality of probe return signals being return signals generated by the corresponding plurality of probe signals being transmitted by the to-be-detected optical fiber, and the plurality of probe return signals being used to indicate a transmission state of a same transmission region in the to-be-detected optical fiber. Each probe return signal is processed with a certain time interval to obtain a processed probe return signal. The signal segments processed in different processed probe return signals correspond to positions in the same transmission region that are not completely the same. The single photon detector is used to perform photoelectric conversion on each processed probe return signal to obtain a first electric signal, and a first OTDR waveform graph is output based on the plurality of first electric signals, the first OTDR waveform graph being used to indicate the transmission state of the same transmission region.

[0006] In the technical solution, the photon number of the detection echo signal is reduced at certain time intervals by amplitude reduction processing of each detection echo signal. In this way, the strong detection echo signal in the time period of amplitude reduction processing can be avoided to affect the following detection echo signal. Since the signal segments of amplitude reduction processing in different processed detection echo signals correspond to different positions in the same transmission region, the detection echo signal corresponding to each position in the transmission region is reflected in the first OTDR waveform diagram. Therefore, the OTDR can eliminate curve distortion and improve performance and practicability. On the other hand, the technical solution adopts the method of amplitude reduction processing of each detection echo signal, instead of the method of electrically gated control of the single-photon detector. The electrically gated control method refers to controlling the bias voltage of the SPAD to control whether the SPAD works in the Geiger mode. The electrically gated control method can be applied to semiconductor single-photon detectors, but cannot be applied to single-photon detectors of superconducting materials. The technical solution can be applied to single-photon detectors of superconducting materials. For semiconductor single-photon detectors, when a strong reflection peak appears, a post-pulse problem occurs. The post-pulse problem causes the OTDR curve to appear a strong reflection peak after a strong reflection peak, and the latter strong reflection peak is an error curve that should not appear. The electrically gated control method cannot avoid the post-pulse problem. Since the technical solution can reduce the photon number by amplitude reduction, the appearance of a strong reflection peak can be avoided at certain time intervals. Therefore, the technical solution can avoid the post-pulse problem.

[0007] In a possible implementation of the first aspect, the at least two time intervals of the multiple times of amplitude reduction processing of each detection echo signal are different. In the possible implementation, the electrically gated control method cannot adjust the size of the at least two time intervals, but the implementation can adjust the size of the at least two time intervals by amplitude reduction processing of each detection echo signal. By adjusting the size of the at least two time intervals, the OTDR can reduce the time interval near the curve distortion and increase the time interval in the position where the curve distortion does not appear. In this way, the number of required detection echo signals can be reduced, and the detection times can be reduced.

[0008] In a possible implementation of the first aspect, each processing time period of each detection echo signal is greater than the dead time of the single-photon detector. The processing time period is the sum of the time of one time of amplitude reduction processing and the corresponding time interval. The corresponding time interval is the time interval between the present time of amplitude reduction processing and the next time of amplitude reduction processing. In the possible implementation, each processing time period is greater than the dead time of the single-photon detector, so that the concave can be avoided in the OTDR curve corresponding to the same detection echo signal.

[0009] In a possible implementation of the first aspect, each processing time period of each probe echo signal is an integer multiple of a dip time delay, the dip time delay being a ratio of a dip distance to a speed of light, and the dip distance being a distance between positions of the optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal point being a signal point at which a first dip of the processed probe echo signal starts. In the possible implementation, each processing time period of each probe echo signal is an integer multiple of the dip time delay, so that the first OTDR waveform diagram is more complete and the number of tests is less.

[0010] In a possible implementation of the first aspect, the time interval is greater than a dip time delay, the dip time delay being a ratio of a dip distance to a speed of light, and the dip distance being a distance between positions of the optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal point being a signal point at which a first dip of the processed probe echo signal starts. In the possible implementation, the dip time delay is less than the time interval, so that there is an overlap between wave crests of adjacent two probe echo signals. In this way, data loss is avoided, and the first OTDR waveform diagram is more complete.

[0011] In a possible implementation of the first aspect, the single-photon detector is an avalanche photodiode, and a working mode of the avalanche photodiode includes a linear mode and a Geiger mode. The OTDR is specifically configured to: when the avalanche photodiode is in the Geiger mode, obtain a first electrical signal based on photoelectric conversion of the avalanche photodiode on each processed probe echo signal. The OTDR is further configured to: send a detection signal to the optical fiber to be measured, and receive a detection echo signal from the optical fiber to be measured, the detection echo signal being a back echo signal generated by the detection signal being transmitted by the optical fiber to be measured, and the detection signal being used to indicate a transmission state of the optical fiber to be measured. When the avalanche photodiode is in the linear mode, obtain a second electrical signal based on photoelectric conversion of the avalanche photodiode on the detection echo signal, and output a second OTDR waveform diagram based on the second electrical signal, the second OTDR waveform diagram being used to indicate the transmission state of the optical fiber to be measured. In the possible implementation, the same device can be used to implement the functions of the linear-mode avalanche photodiode and the single-photon detector. Not only can the measurement speed, the measurement accuracy of the fault area, and the dynamic range be improved, but also the cost can be saved, and the circuit structure is simpler.

[0012] In a possible implementation manner of the first aspect, the OTDR further includes a switch, the switch includes a first end, a second end and a third end. The first end of the switch is connected with the avalanche photodiode. The OTDR is further configured to: when the avalanche photodiode is in the Geiger mode, turn on the first end and the second end of the switch, and output a first electrical signal based on the second end of the switch. When the avalanche photodiode is in the linear mode, turn on the first end and the third end of the switch, and output a second electrical signal based on the third end of the switch. In the possible implementation manner, the first electrical signal and the second electrical signal output by the switch are distinguished, and subsequent different processing can be performed on the first electrical signal and the second electrical signal respectively.

[0013] In a possible implementation manner of the first aspect, the OTDR further includes an optical attenuator, the optical attenuator is connected with the single-photon detector. The OTDR is further configured to: perform attenuation processing on the plurality of detection signals based on the optical attenuator to obtain a plurality of attenuated detection signals. The OTDR is specifically configured to: sequentially send the plurality of attenuated detection signals to the to-be-measured optical fiber. In the possible implementation manner, there is a dead time when the avalanche photodiode is in the Geiger mode. The attenuation processing on the detection signals by the optical attenuator can reduce the probability that no photons are detected when the avalanche photodiode is in the Geiger mode.

[0014] In a possible implementation manner of the first aspect, the OTDR further includes an optical modulator, the optical modulator is connected with the single-photon detector, and the optical modulator is used to connect the to-be-measured optical fiber. The OTDR is specifically configured to: perform amplitude reduction processing on each detection echo signal at a certain time interval based on the optical modulator to obtain a processed detection echo signal. In the possible implementation manner, the amplitude reduction processing on the detection echo signal by the optical modulator can eliminate OTDR curve distortion and avoid the post-pulse problem.

[0015] In a second aspect, a control method of an optical time domain reflectometer (OTDR) is provided. The method is applied to the OTDR. The method includes: sequentially sending a plurality of detection signals to a to-be-measured optical fiber, and sequentially receiving a plurality of detection echo signals from the to-be-measured optical fiber, the plurality of detection echo signals being echo signals generated by the to-be-measured optical fiber in response to the plurality of detection signals, and the plurality of detection echo signals being used to indicate a transmission state of a same transmission region in the to-be-measured optical fiber. Amplitude reduction processing is performed on each detection echo signal at a certain time interval to obtain a processed detection echo signal. The amplitude reduction processed signal segments in different processed detection echo signals correspond to positions in the same transmission region that are not completely the same. Each processed detection echo signal is photoelectrically converted based on a single-photon detector in the OTDR to obtain a first electrical signal, and a first OTDR waveform diagram is output based on the plurality of first electrical signals, the first OTDR waveform diagram being used to indicate the transmission state of the same transmission region.

[0016] In a possible implementation manner of the second aspect, the at least two time intervals in which each of the probe echo signals is subjected to the multiple amplitude reduction processes are different.

[0017] In a possible implementation manner of the second aspect, each processing time period of each of the probe echo signals is greater than a dead time of the single-photon detector, and the processing time period is a sum of a time of one amplitude reduction process and a corresponding time interval, and the corresponding time interval is a time interval between the one amplitude reduction process and a next amplitude reduction process.

[0018] In a possible implementation manner of the second aspect, each processing time period of each of the probe echo signals is an integer multiple of an amplitude reduction delay, and the amplitude reduction delay is a ratio of an amplitude reduction distance to a speed of light, and the amplitude reduction distance is a distance between positions of an optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal points are signal points at which the first amplitude reduction of the processed probe echo signals starts.

[0019] In a possible implementation manner of the second aspect, the time interval is greater than the amplitude reduction delay, and the amplitude reduction delay is a ratio of an amplitude reduction distance to a speed of light, and the amplitude reduction distance is a distance between positions of an optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal points are signal points at which the first amplitude reduction of the processed probe echo signals starts.

[0020] In a possible implementation manner of the second aspect, the single-photon detector is an avalanche photodiode, and a working mode of the avalanche photodiode includes a linear mode and a Geiger mode. The method of optically-electrically converting each of the processed probe echo signals to obtain the first electric signal based on the single-photon detector in the OTDR includes: when the avalanche photodiode is in the Geiger mode, optically-electrically converting each of the processed probe echo signals based on the avalanche photodiode to obtain the first electric signal. The method further includes: sending a detection signal to the to-be-detected optical fiber, and receiving a detection echo signal from the to-be-detected optical fiber, the detection echo signal being a back echo signal generated by the detection signal being transmitted by the to-be-detected optical fiber, and the detection signal being used to indicate a transmission state of the to-be-detected optical fiber. When the avalanche photodiode is in the linear mode, optically-electrically converting the detection echo signal based on the avalanche photodiode to obtain a second electric signal, and outputting a second OTDR waveform based on the second electric signal, the second OTDR waveform being used to indicate the transmission state of the to-be-detected optical fiber.

[0021] In a possible implementation manner of the second aspect, the OTDR further includes a switch, and the switch includes a first end, a second end, and a third end. The first end of the switch is connected to the avalanche photodiode. The method further includes: when the avalanche photodiode is in the Geiger mode, turning on the first end and the second end of the switch, and outputting the first electric signal based on the second end of the switch. When the avalanche photodiode is in the linear mode, turning on the first end and the third end of the switch, and outputting the second electric signal based on the third end of the switch.

[0022] In a possible implementation manner of the second aspect, the OTDR further includes an optical attenuator connected with the single-photon detector. The method further includes: performing attenuation processing on the plurality of probe signals based on the optical attenuator to obtain a plurality of attenuated probe signals. The sequentially sending the plurality of probe signals to the to-be-measured optical fiber includes: sequentially sending the plurality of attenuated probe signals to the to-be-measured optical fiber.

[0023] In a possible implementation manner of the second aspect, the OTDR further includes an optical modulator connected with the single-photon detector, and the optical modulator is used to connect the to-be-measured optical fiber. The performing amplitude reduction processing on each probe echo signal at a certain time interval to obtain a processed probe echo signal includes: performing amplitude reduction processing on each probe echo signal at a certain time interval based on the optical modulator to obtain a processed probe echo signal.

[0024] In a third aspect, a computer readable storage medium is provided, which includes computer instructions, when the computer instructions are executed on a processing device, cause the processing device to execute the method provided in the second aspect or any possible implementation manner of the second aspect.

[0025] In a fourth aspect, a computer program product is provided, when the computer program product is executed on a computer, cause the computer to execute the method provided in the second aspect or any possible implementation manner of the second aspect.

[0026] It can be understood that any of the OTDR control method, computer storage medium or computer program product provided above is applied to the OTDR provided above, and the beneficial effects achieved thereby can refer to the beneficial effects of the corresponding OTDR provided above, which will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A schematic diagram of an operating mode of an avalanche photodiode provided by an embodiment of the present application;

[0028] Figure 2 A structural schematic diagram of a first optical time domain reflectometer provided by an embodiment of the present application;

[0029] Figure 3 A schematic diagram of an optical time domain reflectometer curve provided by an embodiment of the present application Figure 1 ;

[0030] Figure 4 A structural schematic diagram of a second optical time domain reflectometer provided by an embodiment of the present application;

[0031] Figure 5A schematic diagram of an optical time domain reflectometer curve provided by an embodiment of the present application Figure 2 ;

[0032] Figure 6 A schematic diagram of a third optical time domain reflectometer provided by an embodiment of the present application

[0033] Figure 7 A schematic diagram of a fourth optical time domain reflectometer provided by an embodiment of the present application Figure 1 ;

[0034] Figure 8 A schematic diagram of an optical time domain reflectometer curve provided by an embodiment of the present application Figure 3 ;

[0035] Figure 9 A schematic diagram of an optical time domain reflectometer curve provided by an embodiment of the present application Figure 4 ;

[0036] Figure 10 A schematic diagram of an optical time domain reflectometer curve provided by an embodiment of the present application Figure 5 ;

[0037] Figure 11 A schematic diagram of a fourth optical time domain reflectometer provided by an embodiment of the present application Figure 2 ;

[0038] Figure 12 A schematic diagram of a control method of a fourth optical time domain reflectometer provided by an embodiment of the present application. DETAILED DESCRIPTION

[0039] It should be noted that the terms "first", "second", and the like in the embodiments of the present application are only used for the purpose of distinguishing the same type of features, and should not be understood as indicating relative importance, quantity, order, and the like.

[0040] The terms "exemplary" or "for example" and the like in the embodiments of the present application are used to represent that an example, an example, or an illustration. Any embodiment or design scheme described as "exemplary" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the use of "exemplary" or "for example" and the like is intended to present the relevant concept in a specific manner.

[0041] The term "connection" in the embodiments of the present application should be interpreted broadly, for example, it can refer to a direct physical connection, or an indirect connection through electronic devices, such as a connection through resistors, inductors, capacitors or other electronic devices.

[0042] First, some basic concepts related to the present application are explained:

[0043] 1. Optical time domain reflectometer (OTDR)

[0044] OTDR is a precision optoelectronic integrated instrument made by using Rayleigh scattering and Fresnel reflection generated when light is transmitted in an optical fiber. OTDR can be applied to optical fiber networks requiring fault positioning, such as core networks, data centers, transmission networks, access networks, and vehicle-mounted optical fiber networks.

[0045] 2. Avalanche photodiode (APD)

[0046] APD is a semiconductor detector that converts light into electricity using the photoelectric effect. As shown in FIG. 1, an avalanche photodiode has two working modes: linear mode and Geiger mode. The avalanche photodiode is in linear mode when the working voltage is Vpt~Vbd, and the multiplication gain is limited, for example, 10~100 times. Vpt is the minimum voltage for working in linear mode, and Vbd is the avalanche voltage. The avalanche photodiode is in Geiger mode when the working voltage is greater than Vbd, and the multiplication gain rises sharply. Figure 1

[0047] 3. Avalanche photodiode (APD) OTDR

[0048] The detector in the APD OTDR works in linear mode. For example, the detector can be an APD working in linear mode. As shown in FIG. 2, the APD OTDR includes a light source 201, a coupler 202, an optical fiber 203, a detector 204, and a data processing unit 205. Figure 2 ​As shown, the first OTDR 100 is an APD OTDR. The first OTDR 100 includes a first controller 110, a first laser 120, a first circulator 130, a first APD 140, a first trans-impedance amplifier (TIA) 150, and a first analog-to-digital converter (ADC) 160. The first laser 120 and the first ADC 160 are connected to the first controller 110, the first laser 120 and the first APD 140 are connected to the first circulator 130, and the first APD 140 and the first ADC 160 are connected to the first TIA 150. The first circulator 130 is used to connect a first to-be-measured optical fiber 170. The first controller 110 is used to control the first laser 120 to send an optical pulse. The optical pulse passes through the first circulator 130 to the first to-be-measured optical fiber 170 and is transmitted in the first to-be-measured optical fiber 170. At different positions of the first to-be-measured optical fiber 170, the optical pulse is reflected back to the first circulator 130. The reflected light signal passes through the first circulator 130 to the first APD 140. The first APD 140 is used to convert the reflected light signal into a current signal. The first TIA 150 is used to convert the current signal into a voltage signal. The first ADC 160 is used to convert the voltage signal from an analog signal to a digital signal. The first controller 110 is used to receive the digital signal and draw an OTDR curve according to the digital signal.

[0049] The APD OTDR can continuously collect a strong light signal, and can obtain an OTDR curve of the entire optical fiber through one measurement, and has the characteristics of fast measurement. However, in long-distance measurement, it is usually necessary to increase the pulse width of the optical pulse to increase the intensity of the reflected light signal. However, increasing the pulse width will cause the spatial resolution to decrease. In addition, it is difficult to achieve a spatial resolution of less than 1 meter due to the bandwidth and response time of the analog detection technology of the photodetector.

[0050] 4. OTDR curve

[0051] As Figure 3As shown, the abscissa of the OTDR curve can be the fiber length (e.g. in km), and the ordinate can be the relative power of the reflected light signal (e.g. in decibel (dB)). When the light pulse is just transmitted to the fiber under test, the relative power of the reflected light signal is relatively large at the starting position of the fiber length. As the light pulse propagates in the fiber under test, the light pulse is affected by Rayleigh scattering, and the relative power of the reflected light signal decreases. This is reflected as a gently declining curve in the OTDR curve. When there is a strong reflection point in the fiber under test, the light pulse is affected by Fresnel reflection, and the relative power of the reflected light signal surges. This is reflected as a wave crest in the OTDR curve. The strong reflection point can be caused by a fault point in the fiber under test. When the relative power of the reflected light signal decreases to 0 dB, there can be a noise signal. The difference between the relative power of the reflected light signal at the starting position of the fiber length and the relative power of the noise signal is the dynamic range of the OTDR curve. The dynamic range of the OTDR curve reflects the ability of the OTDR to measure the size of the fiber link loss. The parameters of the OTDR curve also include the event blind zone and the measurement time, which reflect the minimum resolution distance to distinguish two similar events.

[0052] 5. Single photon avalanche detector (SPAD) OTDR

[0053] The detector in the SPAD OTDR works in the Geiger mode. For example, the detector can be an APD working in the Geiger mode, can also be a superconducting single photon detector (SSPD), and can also be a superconducting nanowire single photon detector (SNSPD). As shown in FIG. 1, the SPAD OTDR can include a light source 101, a coupler 102, a fiber under test 103, a detector 104, and a data processing unit 105. The light source 101 can be a laser, and the coupler 102 can be a 3dB coupler. The coupler 102 can be connected to the light source 101 and the fiber under test 103. The coupler 102 can split the light from the light source 101 into two parts, one part is transmitted to the fiber under test 103, and the other part is transmitted to the detector 104. The detector 104 can be a SPAD, and the data processing unit 105 can be a computer. Figure 4As shown, the second OTDR 200 is a SPAD OTDR. The second OTDR 200 includes a second controller 210, a second laser 220, a second circulator 230, a first SPAD 240, a first quenching circuit 250, and a first time-to-digital converter (TDC) 260. The second laser 220 and the first TDC 260 are connected to the second controller 210. The second laser 220 and the first SPAD 240 are connected to the second circulator 230. The first SPAD 240 and the first TDC 260 are connected to the first quenching circuit 250. The second circulator 230 is used to connect the second fiber under test 270. The second controller 210 is used to control the second laser 220 to send light pulses, which pass through the second circulator 230 to the second fiber under test 270. The reflected light signals pass through the second circulator 230 to the first SPAD 240. The first SPAD 240 is used to convert the reflected light signals into electrical signals. Due to the avalanche effect of the SPAD, even if the reflected light signal has only one photon, the SPAD can convert the single photon into a larger electrical signal. After the SPAD enters the avalanche process, the avalanche process needs to be stopped in time to wait for the next reflected light signal. The first quenching circuit 250 is used to stop the avalanche process of the first SPAD 240. For example, the first quenching circuit 250 reduces the voltage across the first SPAD 240 to below Vbd, thereby stopping the avalanche process. The first TDC 260 is used to convert the time interval into a digital signal. The first controller is used to receive the electrical signal and the digital signal, and draw an OTDR curve according to the electrical signal and the digital signal.

[0054] The SPAD OTDR can collect weak reflected light signals. Even if the reflected light signal is weak due to distance and other reasons, it is still possible to be detected by the single-photon detector. The SPAD OTDR has high measurement accuracy and range. However, the longer the fiber under test, the fewer the number of photons counted per unit length, and a longer time is needed to obtain the OTDR curve. Moreover, the single-photon detector has a dead time. The dead time refers to the time after the single-photon detector receives a photon to stop the avalanche process to wait for the next reflected light signal. During the dead time, the single-photon detector cannot detect the arrival of other photons. The dead time will cause the single-photon detector to lose count in the case of strong reflected light signals, that is, there is an undetectable area. For example, Figure 5 As shown, the horizontal coordinate of the OTDR curve measured by the single-photon detector can be time, and the vertical coordinate is the relative power of the reflected light signal. After the first strong reflection peak 201 arrives, there will be a dip 203 in the OTDR curve before the second strong reflection peak 202 arrives. The dip 203 is an undetectable area, which is the distortion of the OTDR curve.

[0055] In a possible implementation, a linear mode APD and a single photon detector can be simultaneously set in the OTDR, so that the OTDR has both the measurement speed of the linear mode APD and the high precision of the single photon detector. As shown in Figure 6 The third OTDR 300 includes a third controller 310, a third laser 320, a third circulator 331, an optical splitter 332, a second APD 341, a second TIA 351, a second ADC 361, a second SPAD 342, a second quenching circuit 352, and a second TDC 362. The third laser 320, the second ADC 361, and the second TDC 362 are connected to the third controller 310. The third laser 320 and the optical splitter 332 are connected to the third circulator 331, and the third circulator 331 is used to connect a third to-be-measured optical fiber 370. The second APD 341 and the second SPAD 342 are connected to the optical splitter 332, the second APD 341 and the second ADC 361 are connected to the second TIA 351, and the second SPAD 342 and the second TDC 362 are connected to the second quenching circuit 352. The optical splitter 332 can turn on a path between the third circulator 331 and the second APD 341 and turn off a path between the third circulator 331 and the second SPAD 342. Alternatively, the optical splitter 332 can turn on the path between the third circulator 331 and the second SPAD 342 and turn off the path between the third circulator 331 and the second APD 341. The third OTDR 300 receives a reflected light signal through the second APD 341, quickly obtains an OTDR curve of the entire transmission region of the third to-be-measured optical fiber 370, and determines a fault region of the third to-be-measured optical fiber 370. The third OTDR 300 receives a reflected light signal through the second SPAD 342, and obtains an OTDR curve of the fault region of the third to-be-measured optical fiber 370 with high precision. In this way, fast measurement speed and high measurement precision of the fault region can be achieved. However, the curve distortion problem of the single photon detector still exists. Moreover, the optical splitter 332 and two detectors need to be used, and the cost is relatively high.

[0056] Embodiments of the present application provide an OTDR, which can solve the problem of SPAD OTDR curve distortion. As shown in Figure 7As shown, the fourth OTDR 400 comprises a third single-photon detector, and is configured to be connected to a fourth to-be-measured optical fiber 410. The fourth OTDR 400 is further configured to sequentially send a plurality of probe signals to the fourth to-be-measured optical fiber 410, and sequentially receive a plurality of probe echo signals from the fourth to-be-measured optical fiber 410. The plurality of probe echo signals are echo signals generated by the corresponding plurality of probe signals being transmitted by the fourth to-be-measured optical fiber 410, and are used to indicate the transmission state of a same transmission region (for example, a preset transmission region) in the fourth to-be-measured optical fiber 410. Each probe echo signal is processed by amplitude reduction at a certain time interval to obtain a processed probe echo signal. The signal segments processed by amplitude reduction in different processed probe echo signals correspond to positions in the same transmission region that are not completely the same. The third single-photon detector is used to perform photoelectric conversion on each processed probe echo signal to obtain a first electrical signal, and a first OTDR waveform diagram is output based on the plurality of first electrical signals. The first OTDR waveform diagram is used to indicate the transmission state of the same transmission region.

[0057] For example, the fourth OTDR 400 sends a first probe signal to the fourth to-be-measured optical fiber 410, and receives a first probe echo signal from the fourth to-be-measured optical fiber 410. The first probe signal can be an optical pulse signal, and the first probe echo signal can be a reflected light signal. As the first probe signal is transmitted in the fourth to-be-measured optical fiber 410, the first probe signal will continuously reflect to form the first probe echo signal. The count time of the first probe echo signal is positively correlated with the transmission distance of the first probe signal in the fourth to-be-measured optical fiber 410. The OTDR curve corresponding to the first probe echo signal can refer to Figure 5 . The count time of the OTDR curve corresponding to the first probe echo signal is 800 ns, corresponding to the first probe signal being transmitted to the end point of the preset transmission region in the fourth to-be-measured optical fiber 410. When the count time of the OTDR curve corresponding to the first probe echo signal is 800 ns, the power of the OTDR curve is about 20 dB. The transmission state of the preset transmission region can indicate whether there is a fault point in the preset transmission region. The fourth OTDR 400 processes the first probe echo signal by amplitude reduction at a certain time interval, and the third single-photon detector performs photoelectric conversion on the amplitude-reduced first probe echo signal. The fourth OTDR 400 sends an nth probe signal to the fourth to-be-measured optical fiber 410, and receives an nth probe echo signal from the fourth to-be-measured optical fiber 410. The nth probe echo signal is processed by amplitude reduction at a certain time interval, and the third single-photon detector performs photoelectric conversion on the amplitude-reduced nth probe echo signal. The fourth OTDR 400 outputs a first OTDR waveform diagram.

[0058] For example, the plurality of probe echo signals comprise a first probe echo signal, a second probe echo signal, and a third probe echo signal. Figure 8 (a) of FIG. 1,Figure 8 Figure (b) and Figure 8 Figure (c) shows the corresponding OTDR curves of the first detection echo signal, the second detection echo signal and the third detection echo signal, respectively. Among them, the peak position is the signal that has not been processed by amplitude reduction, and the trough position is the signal with only noise left after the amplitude reduction. The duration of the peak is the above-mentioned time interval. In the same horizontal axis system, there is a time delay between the signal segment of the first detection echo signal with amplitude reduction processing and the signal segment of the second detection echo signal with amplitude reduction processing. That is, the position in the fourth optical fiber to be tested 410 corresponding to the signal segment of the first detection echo signal with amplitude reduction processing does not completely overlap with the position in the fourth optical fiber to be tested 410 corresponding to the signal segment of the second detection echo signal with amplitude reduction processing. The same is true between the second detection echo signal and the third detection echo signal.

[0059] Exemplarily, outputting a first OTDR waveform diagram based on a plurality of first electrical signals may refer to: drawing a plurality of corresponding OTDR curve diagrams based on the plurality of first electrical signals. Figure 9 As shown, multiple OTDR curves are spliced ​​in the same coordinate system. Figure 9 Only three OTDR curves are spliced ​​together. In practice, there may be more OTDR curves. For the same horizontal axis, the maximum vertical axis value of the spliced ​​multiple OTDR curves is used as the vertical axis value of the first OTDR waveform, so as to draw the following figure: Figure 10 The first OTDR waveform is shown.

[0060] by Figure 8 Figure (a) in Figure 8 Figure (b) and Figure 8 Taking Figure (c) in the figure as an example, the principle of eliminating curve distortion of the fourth OTDR400 is introduced. When the first strong reflection peak 201 appears in the OTDR curve corresponding to the first detection echo signal, the first detection echo signal is subjected to amplitude reduction processing to avoid the occurrence of a depression 203. Since there is a time delay between the signal segment of the amplitude reduction processing of the first detection echo signal and the signal segment of the amplitude reduction processing of the second detection echo signal, when the first strong reflection peak 201 appears, the second detection echo signal is amplitude reduced. The OTDR curve corresponding to the second detection echo signal will not be affected by the first strong reflection peak 201 and will not have a depression 203. After the first strong reflection peak ends, the second detection echo signal stops decreasing, and the OTDR curve corresponding to the second detection echo signal has a second strong reflection peak 202. As shown Figure 10 As shown, after the first detection echo signal and the second detection echo signal are spliced, a first strong reflection peak 201 and a second strong reflection peak 202 are obtained, but no depression 203 appears.

[0061] In this embodiment, by performing amplitude reduction processing on each detection echo signal at regular time intervals, the number of photons in the detection echo signal can be reduced at regular time intervals. This prevents a strong detection echo signal during the amplitude reduction period from affecting subsequent detection echo signals. Since the amplitude reduction signal segments in the differently processed detection echo signals correspond to different positions within the same transmission region, the detection echo signal corresponding to each position within the transmission region will be reflected in the first OTDR waveform diagram. Therefore, the fourth OTDR 400 can eliminate curve distortion and improve performance and practicality. On the other hand, the embodiment of the present application adopts a method of performing amplitude reduction processing on each detection echo signal, rather than adopting a method of electrically gating the third single-photon detector. Electrical gating control refers to controlling the magnitude of the bias voltage of the SPAD, thereby controlling whether the SPAD operates in Geiger mode. Electrical gating control can be applied to semiconductor single-photon detectors, but not to single-photon detectors made of superconducting materials. However, the embodiment of the present application can be applied to single-photon detectors made of superconducting materials. For semiconductor single-photon detectors, after-pulse problems may occur when strong reflection peaks appear. The after-pulse problem causes the OTDR curve to show a strong reflection peak after a strong reflection peak. This later strong reflection peak is an erroneous curve that should not appear. Electrically gated control methods cannot avoid the after-pulse problem. Because the embodiments of the present application can reduce the number of photons by reducing the amplitude, thereby avoiding the occurrence of strong reflection peaks at regular intervals, the embodiments of the present application can avoid the after-pulse problem.

[0062] In a possible implementation, at least two time intervals of performing multiple amplitude reduction processes on each detection echo signal are different.

[0063] For example, Figure 8 Figure (a) in Figure 8 Figure (b) and Figure 8 As shown in FIG. (c), the duration of the peak is the above time interval. For each OTDR curve corresponding to the detection echo signal, the duration of at least two peaks can be different. For example, the fourth OTDR 400 can first perform a detection and obtain Figure 5 The OTDR curve with curve distortion shown in the figure can determine the location of the notch. This can reduce the duration of the peak near the location where the notch appears, and increase the duration of the peak at the location where the notch does not appear.

[0064] In this embodiment, the electrical gating control method cannot adjust the length of the at least two time intervals. However, in this embodiment, the amplitude of each probe echo signal is reduced, which allows the length of the at least two time intervals to be adjusted. By adjusting the length of the at least two time intervals, the fourth OTDR 400 reduces the time interval near locations where curve distortion occurs and increases the time interval where curve distortion does not occur. This reduces the number of required probe echo signals, thereby reducing the number of detections.

[0065] In one possible embodiment, each processing time period of each detection echo signal is greater than the dead time of the third single-photon detector, and the processing time period is the sum of the time of one amplitude reduction processing and the corresponding time interval, and the corresponding time interval is the time interval between this amplitude reduction processing and the next amplitude reduction processing.

[0066] For example, Figure 8 Figure (a) in Figure 8 Figure (b) and Figure 8 As shown in Figure (c), the processing time period is the sum of the duration of a trough and the duration of the peak adjacent to the trough. In this embodiment, each processing time period is greater than the dead time of the third single-photon detector, which can avoid the occurrence of notches in the OTDR curve corresponding to the same detection echo signal.

[0067] In a possible implementation, each processing time period of each detection echo signal is an integer multiple of the amplitude reduction delay. Figure 8 Figure (a) in Figure 8 Figure (b) and Figure 8 As shown in Figure (c), the amplitude reduction delay is the ratio of the amplitude reduction distance to the speed of light. The amplitude reduction distance is the distance between the optical fiber positions corresponding to the initial signal points in two adjacent processed probe echo signals. The initial signal point is the signal point where the first amplitude reduction of the processed probe echo signal begins. In this embodiment, each processing time period of each probe echo signal is an integer multiple of the amplitude reduction delay, which makes the first OTDR waveform more complete and reduces the number of tests.

[0068] In one possible implementation, the time interval is greater than the ramp-down delay. In this embodiment of the present application, the smaller the ramp-down delay, the smoother and more complete the first OTDR waveform, and the smaller the error. In this implementation, the ramp-down delay is smaller than the time interval, thereby allowing the peaks of two adjacent detection echo signals to overlap. This prevents data loss and makes the first OTDR waveform more complete.

[0069] In a possible implementation, the single photon detector in the fourth OTDR 400 may be an APD, which may also operate in a linear mode.

[0070] In some examples, as shown in Figure 11 The fourth OTDR 400 includes a fourth controller 420, a fourth laser 430, an optical attenuator 440, an optical splitting device 450, an optical modulator 460, a third APD 470, a switch 480, a third quenching circuit 491, a third TDC 492, a third TIA 493, and a third ADC 362. The fourth laser 430, the third TDC 492, and the third ADC 362 are connected to the fourth controller 420. The fourth laser 430 and the optical attenuator 440 are connected to the optical splitting device 450. The optical splitting device 450 is used to connect the fourth to-be-measured optical fiber 410. The optical splitting device 450 can be a circulator or an optical splitter. The optical splitting device 450 and the third APD 470 are connected to the optical modulator 460. The switch 480 includes a first end, a second end, and a third end. The first end of the switch 480 is connected to the third APD 470, the second end of the switch 480 is connected to the third quenching circuit 491, and the third end of the switch 480 is connected to the third TIA 493. The third quenching circuit 491 is connected to the third TDC 492, and the third TIA 493 is connected to the third ADC 362.

[0071] The third single-photon detector is the third APD 470, and the working mode of the third APD 470 includes a linear mode and a Geiger mode. For example, the third APD 470 is controlled to be in the linear mode or the Geiger mode by bias voltage. The fourth OTDR 400 is specifically configured to: when the third APD 470 is in the Geiger mode, convert the first electric signal based on the third APD 470 photoelectric conversion of each processed detection echo signal. In this mode, the detection accuracy of the fourth OTDR 400 is higher. The fourth OTDR 400 is also configured to: send a detection signal to the fourth to-be-measured optical fiber 410, receive a detection echo signal from the fourth to-be-measured optical fiber 410, the detection echo signal being a back echo signal generated by the detection signal being transmitted by the fourth to-be-measured optical fiber 410, and the detection signal being used to indicate the transmission state of the fourth to-be-measured optical fiber 410. When the third APD 470 is in the linear mode, the second electric signal is obtained based on the third APD 470 photoelectric conversion of the detection echo signal, and the second OTDR waveform diagram is output based on the second electric signal, the second OTDR waveform diagram being used to indicate the transmission state of the fourth to-be-measured optical fiber 410. In this mode, the detection speed of the fourth OTDR 400 is faster. In this embodiment, the functions of the linear mode APD and the single-photon detector can be realized by using the same device. Not only can the measurement speed, the measurement accuracy of the fault area, and the dynamic range be improved, but also the cost can be saved, and the circuit structure is simpler.

[0072] Exemplarily, the fourth OTDR 400 is further configured to: when the third APD 470 is in the Geiger mode, turn on the first end and the second end of the switch 480, and output a first electrical signal based on the second end of the switch 480; when the third APD 470 is in the linear mode, turn on the first end and the third end of the switch 480, and output a second electrical signal based on the third end of the switch 480. In this embodiment, the first electrical signal and the second electrical signal are distinguished by the switch 480, and the first electrical signal and the second electrical signal can be processed differently subsequently.

[0073] Exemplarily, the fourth OTDR 400 is further configured to: attenuate the plurality of probe signals based on the optical attenuator 440 to obtain a plurality of attenuated probe signals. The fourth OTDR 400 is specifically configured to: send the plurality of attenuated probe signals to the fourth to-be-measured optical fiber 410 in sequence. Exemplarily, when the third APD 470 is in the linear mode, the detection signal can not be attenuated. In this embodiment, the third APD 470 has a dead time when it is in the Geiger mode. By attenuating the probe signal by the optical attenuator 440, the probability of the third APD 470 failing to detect a photon when it is in the Geiger mode can be reduced.

[0074] Exemplarily, the function of attenuating the probe echo signal can be performed by the optical modulator 460. The optical modulator 460 is connected to the to-be-measured optical fiber through the optical splitting device 450. The fourth OTDR 400 is specifically configured to: attenuate each probe echo signal at a certain time interval based on the optical modulator 460 to obtain a processed probe echo signal. In this embodiment, the probe echo signal is attenuated by the optical modulator 460, thereby eliminating OTDR curve distortion and avoiding the problem of post-pulse.

[0075] Next, a possible application mode of the fourth OTDR 400 is introduced. When testing the fourth to-be-tested optical fiber 410, the controller controls the fourth laser 430 to send a detection signal, and the optical splitting device 450 receives the detection signal and sends it to the fourth to-be-tested optical fiber 410. The detection signal is transmitted through the fourth to-be-tested optical fiber 410 and reflected back as a detection echo signal. The optical splitting device 450 receives the detection echo signal and sends it to the third APD 470. Optionally, the third APD 470 and the switch 480 are both connected with the fourth controller 420. The fourth controller 420 controls the third APD 470 to work in a linear mode, and controls the first end and the third end of the switch 480 to be conductive. The third APD 470 receives the detection echo signal and performs photoelectric conversion, and sends a second electric signal through the switch 480. The second electric signal is processed by the third TIA 493 and the third ADC 362, and then sent to the fourth controller 420. The fourth controller 420 outputs a second OTDR waveform diagram according to the processed second electric signal. The second OTDR waveform diagram can reflect the transmission state of the entire transmission region of the fourth to-be-tested optical fiber 410. Since the accuracy of the second OTDR waveform diagram is not high, the fault position reflected by the second OTDR waveform diagram is usually a range, so the fourth controller 420 can use a single-photon detection mode to measure the fault range.

[0076] The fourth controller 420 controls the fourth laser 430 to sequentially send a plurality of probe signals. For example, the period of the plurality of probe signals can be T, and the pulse width can be s. The fourth controller 420 also controls the third TDC 492 to implement T coincidence counting. Optionally, the optical attenuator 440, the optical modulator 460, and the third APD 470 are connected with the fourth controller 420. The fourth controller 420 controls the optical attenuator 440 to adjust the peak value of the probe signal, so that the single photon detection count generated by the third APD 470 in the period T is equal to the saturation count. The fourth controller 420 controls the optical modulator 460 to input the first probe echo signal and output the first probe echo signal after amplitude reduction processing. The time interval of the amplitude reduction in the first probe echo signal is greater than the pulse width of the modulation signal input by the optical modulator 460, so that the maximum extinction ratio can be achieved. Each processing time period of the first probe echo signal is greater than the dead time of the third APD 470 and the third TDC 492, and is less than the period T. The third TDC 492 measures the count result corresponding to the first probe echo signal and stores it to the fourth controller 420. The fourth controller 420 controls the optical modulator 460 to input the second probe echo signal and output the second probe echo signal after amplitude reduction processing. The signal point corresponding to the position of the second optical fiber to be measured at which the amplitude reduction of the second probe echo signal first starts is different from the signal point corresponding to the position of the second optical fiber to be measured at which the amplitude reduction of the first probe echo signal first starts. The ratio of the difference between the two positions to the speed of light is the amplitude reduction delay. The smaller the amplitude reduction delay is, the better, such as less than the time interval of the amplitude reduction, or less than the response time jitter of the third APD 470 and the third TDC 492. Each processing time period of each probe echo signal can be an integer multiple of the amplitude reduction delay. The third TDC 492 measures the count result corresponding to the second probe echo signal and stores it to the fourth controller 420. The fourth controller 420 outputs the first OTDR waveform diagram according to the plurality of first electrical signals corresponding to the plurality of processed probe echo signals.

[0077] Based on the structure of the fourth OTDR 400 shown in the above Figure 7 or Figure 11 The control method of the fourth OTDR 400 shown in the above Figure 12 may be performed. The method comprises:

[0078] S110: sequentially sending a plurality of probe signals to the fourth optical fiber to be measured 410, and sequentially receiving a plurality of probe echo signals from the fourth optical fiber to be measured 410.

[0079] Exemplarily, the plurality of probe echo signals are echo signals generated by the transmission of the corresponding plurality of probe signals by the fourth optical fiber to be measured 410, and the plurality of probe echo signals are used to indicate the transmission state of the same transmission region in the fourth optical fiber to be measured 410.

[0080] S120: performing a dip processing on each probe echo signal at a time interval to obtain a processed probe echo signal.

[0081] Exemplarily, the signal segments of the dip processing in different processed probe echo signals correspond to different positions in the same transmission region.

[0082] S130: performing a photoelectric conversion on each processed probe echo signal based on the third single-photon detector in the fourth OTDR 400 to obtain a first electric signal, and outputting a first OTDR waveform diagram based on the plurality of first electric signals.

[0083] Exemplarily, the first OTDR waveform diagram is used to indicate the transmission state of the same transmission region.

[0084] In some possible implementation manners, the at least two time intervals of the multiple times of dip processing on each probe echo signal are different.

[0085] In some possible implementation manners, each processing time period of each probe echo signal is greater than the dead time of the third single-photon detector, the processing time period being the sum of the time of one dip processing and the corresponding time interval, the corresponding time interval being the time interval between the present dip processing and the next dip processing.

[0086] In some possible implementation manners, each processing time period of each probe echo signal is an integer multiple of a dip time delay, the dip time delay being the ratio of a dip distance to the speed of light, the dip distance being the distance between the positions of the optical fiber corresponding to the initial signal points in adjacent two processed probe echo signals, the initial signal point being the signal point at which the first dip of the processed probe echo signal starts.

[0087] In some possible implementation manners, the time interval is greater than the dip time delay, the dip time delay being the ratio of a dip distance to the speed of light, the dip distance being the distance between the positions of the optical fiber corresponding to the initial signal points in adjacent two processed probe echo signals, the initial signal point being the signal point at which the first dip of the processed probe echo signal starts.

[0088] In some possible implementation manners, the third single-photon detector is a third APD 470, and a working mode of the third APD 470 includes a linear mode and a Geiger mode. S130 includes: when the third APD 470 is in the Geiger mode, photoelectrically converting, by the third APD 470, each processed probe echo signal to obtain a first electrical signal. The method further includes: sending a detection signal to the fourth to-be-detected optical fiber 410, receiving a detection echo signal from the fourth to-be-detected optical fiber 410, the detection echo signal being a echo signal generated by the detection signal being transmitted by the fourth to-be-detected optical fiber 410, and the detection signal being used to indicate a transmission state of the fourth to-be-detected optical fiber 410. When the third APD 470 is in the linear mode, photoelectrically converting, by the third APD 470, the detection echo signal to obtain a second electrical signal, and outputting a second OTDR waveform based on the second electrical signal, the second OTDR waveform being used to indicate the transmission state of the fourth to-be-detected optical fiber 410.

[0089] In some possible implementation manners, the fourth OTDR 400 further includes a switch 480, and the switch 480 includes a first end, a second end, and a third end. The first end of the switch 480 is connected to the third APD 470. The method further includes: when the third APD 470 is in the Geiger mode, turning on the first end and the second end of the switch 480, and outputting the first electrical signal based on the second end of the switch 480. When the third APD 470 is in the linear mode, turning on the first end and the third end of the switch 480, and outputting the second electrical signal based on the third end of the switch 480.

[0090] In some possible implementation manners, the fourth OTDR 400 further includes an optical attenuator 440, and the optical attenuator 440 is connected to the third single-photon detector. The method further includes: attenuating, by the optical attenuator 440, the plurality of probe signals to obtain a plurality of attenuated probe signals. S110 includes: sequentially sending the plurality of attenuated probe signals to the fourth to-be-detected optical fiber 410.

[0091] In some possible implementation manners, the fourth OTDR 400 further includes an optical modulator 460, and the optical modulator 460 is connected to the third single-photon detector and used to connect the fourth to-be-detected optical fiber 410. S120 includes: performing, by the optical modulator 460, amplitude reduction processing on each probe echo signal at a certain time interval to obtain a processed probe echo signal.

[0092] The embodiments of the present application also provide a computer readable storage medium including instructions. When the instructions are executed on the fourth OTDR 400 (for example, the fourth OTDR 400 shown in Figure 7 or Figure 11 the processing apparatus therein) or the processing apparatus therein as described in the above embodiments, the fourth OTDR 400 is caused to perform the control method (for example, the control method as described in the above embodiments) as described in the above embodiments. Figure 12The fourth OTDR 400 is controlled according to the method described above. The processing device can be a controller in the fourth OTDR 400.

[0093] The controller according to the embodiments of the present application can be a chip. For example, the controller can be a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a system on chip (SoC), a central processor unit (CPU), a network processor (NP), a digital signal processor (DSP), a microcontroller unit (MCU), a programmable logic device (PLD), or other integrated chip.

[0094] Based on the understanding, the embodiments of the present application further provide a computer program product containing instructions. The technical solution of the present application or the part of the technical solution that makes a contribution to the prior art or the whole or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes instructions for making a computer execute all or part of the steps of the method described in the embodiments of the present application.

[0095] It should be understood that the size of the sequence number of each process described above in the various embodiments of the present application does not mean the order of execution. The execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0096] Those skilled in the art can realize that the modules and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0097] In several embodiments provided in the present application, it should be understood that the disclosed OTDR and control method can be implemented in other manners. For example, the embodiments of the control method of the OTDR described above are merely illustrative. For example, the division of the modules is merely a logical function division. In actual implementation, another division manner can be used. For example, a plurality of modules or components can be combined or integrated into another device, or some features can be ignored or not executed. In addition, the displayed or discussed connection between the modules can be direct connection or indirect connection, and can be electrical, mechanical or in other forms.

[0098] In addition, each function module in each embodiment of the present application can be integrated in one device, or each function module can exist physically separately, or two or more function modules can be integrated in one device.

[0099] The above describes only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An optical time domain reflectometer (OTDR) characterized by, The OTDR comprises a single-photon detector, and is configured to be connected to a to-be-tested optical fiber; and the OTDR is further configured to: send a plurality of probe signals to the to-be-tested optical fiber in sequence, and receive a plurality of probe echo signals from the to-be-tested optical fiber in sequence, wherein the plurality of probe echo signals are echo signals generated by the corresponding plurality of probe signals being transmitted by the to-be-tested optical fiber, and the plurality of probe echo signals are used to indicate a transmission state of a same transmission region in the to-be-tested optical fiber; perform amplitude reduction processing on each of the probe echo signals at a certain time interval to obtain a processed probe echo signal; and signal segments subjected to the amplitude reduction processing in different processed probe echo signals correspond to positions in the same transmission region that are not completely same. perform photoelectric conversion on each of the processed probe echo signals based on the single-photon detector to obtain a first electric signal, and output a first OTDR waveform diagram based on a plurality of the first electric signals, wherein the first OTDR waveform diagram is used to indicate the transmission state of the same transmission region.

2. The OTDR of claim 1, wherein, At least two time intervals of a plurality of times of amplitude reduction processing performed on each of the probe echo signals are different.

3. The OTDR according to claim 1 or 2, characterized in that Each processing time period of each of the probe echo signals is greater than a dead time of the single-photon detector, the processing time period is a sum of a time of one time of amplitude reduction processing and a corresponding time interval, and the corresponding time interval is a time interval between the one time of amplitude reduction processing and a next time of amplitude reduction processing.

4. The OTDR of claim 3, wherein, Each processing time period of each of the probe echo signals is an integer multiple of an amplitude reduction time delay, the amplitude reduction time delay is a ratio of an amplitude reduction distance to a speed of light, and the amplitude reduction distance is a distance between positions of the optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal points are signal points at which amplitude reduction is started for the first time in the processed probe echo signals.

5. The OTDR according to any one of claims 1 to 4, wherein: The time interval is greater than the amplitude reduction time delay, the amplitude reduction time delay is a ratio of an amplitude reduction distance to a speed of light, and the amplitude reduction distance is a distance between positions of the optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal points are signal points at which amplitude reduction is started for the first time in the processed probe echo signals.

6. The OTDR according to any one of claims 1 to 5, characterized in that The single-photon detector is an avalanche photodiode, and working modes of the avalanche photodiode include a linear mode and a Geiger mode; and the OTDR is specifically configured to: when the avalanche photodiode is in the Geiger mode, perform photoelectric conversion on each of the processed probe echo signals based on the avalanche photodiode to obtain a first electric signal; and the OTDR is further configured to: send a detection signal to the to-be-tested optical fiber, and receive a detection echo signal from the to-be-tested optical fiber, wherein the detection echo signal is an echo signal generated by the detection signal being transmitted by the to-be-tested optical fiber, and the detection signal is used to indicate a transmission state of the to-be-tested optical fiber; when the avalanche photodiode is in the linear mode, perform photoelectric conversion on the detection echo signal based on the avalanche photodiode to obtain a second electric signal, and output a second OTDR waveform diagram based on the second electric signal, wherein the second OTDR waveform diagram is used to indicate the transmission state of the to-be-tested optical fiber.

7. The OTDR of claim 6, wherein, The OTDR further comprises a switch, the switch comprising a first end, a second end and a third end; the first end of the switch is connected with the avalanche photodiode; the OTDR is further used for: when the avalanche photodiode is in the Geiger mode, turning on the first end and the second end of the switch, and outputting the first electrical signal based on the second end of the switch; when the avalanche photodiode is in the linear mode, turning on the first end and the third end of the switch, and outputting the second electrical signal based on the third end of the switch.

8. The OTDR of any one of claims 1-7, wherein, The OTDR further comprises an optical attenuator, the optical attenuator being connected with the single-photon detector; The OTDR is further used for: performing attenuation processing on the plurality of detection signals based on the optical attenuator to obtain a plurality of attenuated detection signals; The OTDR is specifically used for: sequentially sending a plurality of attenuated detection signals to the optical fiber to be measured.

9. The OTDR of any of claims 1-8, wherein, The OTDR further comprises an optical modulator, the optical modulator being connected with the single-photon detector, and the optical modulator being used for connecting the optical fiber to be measured; The OTDR is specifically used for: performing amplitude reduction processing on each of the detection echo signals at a certain time interval based on the optical modulator to obtain a processed detection echo signal.

10. A control method of an optical time domain reflectometer (OTDR), characterized by, The method is applied to an OTDR; the method comprises: sequentially sending a plurality of detection signals to an optical fiber to be measured, and sequentially receiving a plurality of detection echo signals from the optical fiber to be measured, the plurality of detection echo signals being echo signals generated by corresponding detection signals being transmitted by the optical fiber to be measured, and the plurality of detection echo signals being used for indicating a transmission state of a same transmission region in the optical fiber to be measured; performing amplitude reduction processing on each of the detection echo signals at a certain time interval to obtain a processed detection echo signal, and the signal segments subjected to amplitude reduction processing in different processed detection echo signals corresponding to positions in the same transmission region being not completely the same; performing photoelectric conversion on each of the processed detection echo signals based on a single-photon detector in the OTDR to obtain a first electrical signal, and outputting a first OTDR waveform diagram based on a plurality of first electrical signals, the first OTDR waveform diagram being used for indicating the transmission state of the same transmission region.

11. The method of claim 10, wherein, At least two time intervals of the plurality of times of amplitude reduction processing performed on each of the detection echo signals are different.

12. The method according to claim 10 or 11, characterized in that, Each processing time period of each of the detection echo signals is greater than a dead time of the single-photon detector, the processing time period being a sum of a time of one amplitude reduction processing and a corresponding time interval, and the corresponding time interval being a time interval between the present amplitude reduction processing and the next amplitude reduction processing.

13. The method of claim 12, wherein, Each processing time period of each of the detection echo signals is an integer multiple of an amplitude reduction time delay, the amplitude reduction time delay being a ratio of an amplitude reduction distance to a speed of light, and the amplitude reduction distance being a distance between positions of the optical fiber corresponding to initial signal points in adjacent two processed detection echo signals, the initial signal point being a signal point at which the first amplitude reduction of the processed detection echo signal starts.

14. The method according to any one of claims 10 to 13, characterized in that, The time interval is greater than a drop time delay, the drop time delay is a ratio of a drop distance and a speed of light, the drop distance is a distance between positions of the optical fiber corresponding to initial signal points in adjacent two processed probe echo signals, and the initial signal point is a signal point at which a first drop of the processed probe echo signal starts.

15. The method according to any one of claims 10 to 14, characterized in that, The single-photon detector is an avalanche photodiode, and a working mode of the avalanche photodiode includes a linear mode and a Geiger mode. The single-photon detector in the OTDR photoelectrically converts each processed probe echo signal to obtain a first electric signal. When the avalanche photodiode is in the Geiger mode, the single-photon detector photoelectrically converts each processed probe echo signal to obtain a first electric signal. A detection signal is sent to the optical fiber to be tested, and a detection echo signal is received from the optical fiber to be tested, the detection echo signal being a return signal of the detection signal transmitted by the optical fiber to be tested, and the detection signal being used to indicate a transmission state of the optical fiber to be tested. When the avalanche photodiode is in the linear mode, the single-photon detector photoelectrically converts the detection echo signal to obtain a second electric signal, and a second OTDR waveform diagram is output based on the second electric signal, the second OTDR waveform diagram being used to indicate the transmission state of the optical fiber to be tested.

16. The method of claim 15, wherein, The OTDR further includes a switch, the switch including a first end, a second end, and a third end; the first end of the switch is connected to the avalanche photodiode; and the method further includes: When the avalanche photodiode is in the Geiger mode, the first end and the second end of the switch are turned on, and the first electric signal is output based on the second end of the switch; When the avalanche photodiode is in the linear mode, the first end and the third end of the switch are turned on, and the second electric signal is output based on the third end of the switch.

17. The method according to any one of claims 10-16, characterized in that, The OTDR further includes an optical attenuator, and the optical attenuator is connected to the single-photon detector; and the method further includes: The optical attenuator attenuates the plurality of probe signals to obtain a plurality of attenuated probe signals; The plurality of probe signals are sequentially sent to the optical fiber to be tested, including: The plurality of attenuated probe signals are sequentially sent to the optical fiber to be tested.

18. The method according to any one of claims 10-17, characterized in that, The OTDR further includes an optical modulator, and the optical modulator is connected to the single-photon detector and used to connect the optical fiber to be tested; The probe echo signal is processed at a certain time interval to obtain a processed probe echo signal, including: The optical modulator processes each probe echo signal at a certain time interval to obtain a processed probe echo signal.

19. A computer-readable storage medium, characterized in that, The computer program product includes computer instructions, and when the computer instructions run on a processing device, the processing device executes the method in any one of claims 10-18.

20. A computer program product, characterised in that, When the computer program product runs on a computer, the computer executes the method in any one of claims 10-18.

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