CN108075828B - OTDR device based on multichannel optical fiber optical signal monitoring - Google Patents

Abstract

The invention discloses an OTDR device based on multipath optical fiber optical signal monitoring, which comprises a main control unit, an optical transmitting unit, an optical branching unit, an oscillography unit, N coupling units and N optical branching detection units, wherein the main control unit is respectively connected with the optical transmitting unit and the oscillography unit, the optical transmitting unit is connected with the optical branching unit, the optical branching unit is correspondingly connected with the N coupling units, the input end of each coupling unit is respectively correspondingly connected with the optical branching unit and the optical branching detection unit, the output end of each coupling unit is correspondingly connected with an optical fiber to be tested, and each optical branching detection unit is correspondingly connected with the main control unit. The invention has the advantages that: the method can simultaneously monitor, search and locate the fault points of the optical fibers to be tested, and has high test speed and high measurement accuracy.

Description

An OTDR device based on multi-channel optical fiber optical signal monitoring

Technical Field

The invention relates to the field of optical time domain reflection, and in particular to an OTDR device based on multi-path optical fiber optical signal monitoring.

Background Art

Optical Time-Domain Reflectometry (OTDR) is a precise optoelectronic integrated instrument that uses the backscattering caused by Rayleigh scattering and Fresnel reflection when light is transmitted in an optical fiber. It is widely used in the maintenance and construction of optical cable lines. It can measure optical fiber length, optical fiber transmission attenuation, joint attenuation and fault location.

At present, there are two main types of OTDRs used for optical fiber fault location monitoring: single-photon detection OTDR for single-photon level weak light detection and ordinary OTDR for non-single-photon level light detection; avalanche photodiode (APD) is a common photosensitive detection element in the field of laser communication. It is an indispensable component of OTDR because of its high detection sensitivity.

Among them, the avalanche photodiode of the single-photon detection OTDR works in the gated Geiger mode, while the avalanche photodiode of the ordinary OTDR works in the linear mode; the avalanche photodiode working in the linear mode does not need to consider the after-pulse effect and can work in the continuous signal acquisition state, which has the advantage of fast measurement time. However, since the avalanche photodiode working in the linear mode has a low gain and cannot detect weak optical signals, the measurement accuracy and measurement distance of the ordinary OTDR are limited.

Although the single-photon detection OTDR can detect extremely weak optical signals that are smaller than thermal noise, it can obtain higher measurement accuracy, longer measurement distance and larger dynamic range than ordinary OTDR, which can make up for the shortcomings of ordinary OTDR. However, because the avalanche photodiode of the single-photon detection OTDR works in the gated Geiger mode, it is affected by the after-pulse and has a certain dead time, resulting in a low gate pulse repetition frequency of the single-photon detector. It can only work in the point-by-point scanning mode, and it often takes a long time to complete a detection task; the higher the measurement accuracy and the more scanning points, the longer the detection time required for the single-photon detection OTDR; the greater the probability of the after-pulse, the longer the dead time that needs to be set for the single-photon detection OTDR.

In addition, because the avalanche photodiode is a capacitive device, when the gate pulse signal is loaded on the avalanche photodiode to charge and discharge it, the corresponding noise will be introduced, which will submerge the effective light-generated avalanche signal and affect the detection result. At the same time, temperature changes will also have a certain impact on the detection performance of the avalanche photodiode, causing the instability of the working performance of the avalanche photodiode, making the positioning and search of the optical fiber fault point inaccurate.

Summary of the invention

The object of the present invention is to provide an OTDR device based on multi-channel optical fiber optical signal monitoring to solve the defects in the background technology.

To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: an OTDR device based on multi-channel optical fiber optical signal monitoring, comprising a main control unit, an optical sending unit, an optical branching unit, an oscilloscope unit, N coupling units and N optical branch detection units, the main control unit is respectively connected to the optical sending unit and the oscilloscope unit, the optical sending unit is connected to the optical branching unit, the optical branching unit is correspondingly connected to the N coupling units, the input end of each of the coupling units is correspondingly connected to the optical branching unit and an optical branch detection unit, the output end of each of the coupling units is correspondingly connected to an optical fiber to be tested, and each of the optical branch detection units is correspondingly connected to the main control unit.

Further, the main control unit includes a single chip microcomputer, a pulse signal generator, a signal attenuation driver and a data processor, and the pulse signal generator, the signal attenuation driver and the data processor are respectively connected to the single chip microcomputer;

The optical transmission unit comprises a pulse light source and an adjustable attenuator, the pulse light source is connected to the pulse signal generator and the adjustable attenuator respectively, and the adjustable attenuator is connected to the signal attenuation driver and the optical branching unit respectively;

Each of the optical branching detection units includes a 1x2 splitter, a common detection unit and a single photon detection unit. Each of the 1x2 splitter input ends is correspondingly connected to a coupling unit, and each of the 1x2 splitter output ends is correspondingly connected to a common detection unit and a single photon detection unit.

Furthermore, the optical branching unit is a 1xN splitter; the oscilloscope unit is a waveform display, and the waveform display includes N display areas corresponding to the detection light waveform curve output by the optical branching detection unit; each of the coupling units is a directional coupler or a circulator; wherein N is an integer ≥2.

Further, each of the ordinary detection units includes a first photoelectric detection module, a filter, a first signal amplifier and a first analog/digital converter connected in sequence, each of the first photoelectric detection modules is also correspondingly connected to an output port of a 1x2 spectrometer, each of the first analog/digital converters is also correspondingly connected to a data processor of the main control unit, each of the first photoelectric detection modules includes a first avalanche photodiode, a first temperature control module and a first packaging box; each of the first temperature control modules includes a first refrigerator, a first heater and a first temperature sensor, each of the first refrigerator and the first heater are respectively connected to the single-chip microcomputer of the main control unit, each of the first temperature sensors are respectively connected to the single-chip microcomputer of the main control unit and the pins of a first avalanche photodiode, and the first avalanche photodiode, the first refrigerator, the first heater and the first temperature sensor corresponding to each of the first photoelectric detection modules are correspondingly packaged in a first packaging box.

Furthermore, each of the single-photon detection units includes a second photoelectric detection module, a bias module, a clock module, a gate pulse module, a noise suppression module, a pulse shaping module and a photon counter. Each of the bias modules is respectively connected to the single-chip microcomputer of the main control unit and a second photoelectric detection module. Each of the clock modules is respectively connected to the pulse signal generator of the main control unit and a gate pulse module. Each of the gate pulse modules is respectively connected to the single-chip microcomputer of the main control unit and a second photoelectric detection module. Each of the noise suppression modules is respectively connected to a second photoelectric detection module and a pulse shaping module. Each of the photon counters is respectively connected to the data processor of the main control unit and a pulse shaping module. The two photoelectric detection modules are each connected to an output port of a 1x2 splitter, and each of the second photoelectric detection modules includes a second avalanche photodiode, a second temperature control module and a second packaging box; each of the second temperature control modules includes a second refrigerator, a second heater and a second temperature sensor, and each of the second refrigerator and the second heater is respectively connected to the single-chip microcomputer of the main control unit, and each of the second temperature sensors is respectively connected to the single-chip microcomputer of the main control unit and the pin of a second avalanche photodiode, and the second avalanche photodiode, the second refrigerator, the second heater and the second temperature sensor corresponding to each of the second photoelectric detection modules are correspondingly packaged in a second packaging box.

Furthermore, each of the bias modules is a voltage source module, and is respectively connected to the microcontroller of the main control unit and to the cathode of a second avalanche photodiode; each of the bias modules is used to provide the reverse bias voltage required for the second avalanche photodiode connected thereto.

Furthermore, each of the gate pulse modules is a gate pulse generator, and is respectively connected to a clock module and to the cathode of a second avalanche photodiode. Each of the gate pulse modules includes a phase-locked loop circuit, a frequency divider and a second signal amplifier. The output end of each phase-locked loop circuit is connected to a second signal amplifier, and the input end of each phase-locked loop circuit is connected to a clock module. Each phase-locked loop circuit includes a phase detector, a loop filter and a voltage-controlled oscillator connected in sequence. Each of the gate pulse modules is used to output a gate control signal to control the charge and discharge of the second avalanche photodiode connected thereto, so as to control the avalanche and quenching process of the second avalanche photodiode. Each of the clock modules is used to control the synchronous triggering of the gate pulse module and the pulse signal generator connected thereto, so that the gate control signal output by the gate pulse module and the bias voltage signal output by the bias module are loaded onto the second avalanche photodiode in a time sequence, so that the second avalanche photodiode works in a Geiger gating mode, thereby realizing single-photon level light intensity signal detection.

Furthermore, each of the noise suppression modules comprises a bandpass filter, a low-pass filter and a third signal amplifier; each of the bandpass filter input ends is correspondingly connected to a gate pulse module output end, and each of the bandpass filter output ends is correspondingly connected to the cathode of a second avalanche photodiode; each of the low-pass filter input ends is correspondingly connected to the anode of a second avalanche photodiode, and each of the low-pass filter output ends is correspondingly connected to the input end of a third signal amplifier; each of the third signal amplifier output ends is correspondingly connected to a pulse shaping module; each of the bandpass filters is used to filter out the sideband noise and harmonic noise signals brought by the gated signal output by the corresponding gate pulse module; each of the low-pass filters is used to filter out the noise signals introduced by the gated signal output by the corresponding gate pulse module and produced after the photoelectric conversion of the corresponding second avalanche photodiode, so as to obtain an effective photogenerated carrier avalanche signal therefrom.

Furthermore, each of the pulse shaping modules includes a pulse amplitude detector, a pulse shaping circuit and a second analog/digital converter; each of the pulse amplitude detector input ends is correspondingly connected to a third signal amplifier output end, each of the pulse amplitude detector output ends is correspondingly connected to a pulse shaping circuit input end, each of the pulse shaping circuit output ends is correspondingly connected to a second analog/digital converter input end, each of the second analog/digital converter output ends is correspondingly connected to a photon counter input end, and each of the photon counter output ends is correspondingly connected to a data processor of the main control unit.

Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can accurately locate and find fault points of multiple optical fibers to be tested, which is beneficial to improving the efficiency of operation and maintenance of optical fiber lines by operating monitoring personnel and reducing the investment in monitoring costs of optical fiber links. It has the advantages of high work efficiency, accurate measurement results and fast monitoring speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a block diagram of an OTDR device based on multi-channel optical fiber optical signal monitoring according to the present invention;

FIG2 is a block diagram of a specific embodiment of an OTDR device based on multi-channel optical fiber optical signal monitoring according to the present invention;

FIG3 is a structural block diagram of each common detection unit in FIG2;

FIG4 is a block diagram of the structure of each single photon detection unit in FIG3 ;

FIG5 is a circuit connection block diagram of the gate pulse module based on FIG4;

In the figure: 1, main control unit; 11, single chip microcomputer; 12, pulse signal generator; 13, signal attenuation driver; 14, data processor; 2, optical transmission unit; 21, pulse light source; 22, adjustable attenuator; 3, optical branching unit; 4, oscilloscope unit; 5, coupling unit; 6, optical branching detection unit; 61, 1x2 optical splitter; 62, ordinary detection unit; 621, first photoelectric detection module; 621a, first avalanche photodiode; 621b, first temperature control module; 621b-1, first refrigerator; 621b-2, first heater; 621b-3, first temperature sensor; 621c, first packaging box; 622, filter; 623, first signal amplifier; 624, first analog/digital converter; 63, single photon detection unit; 6 31. The second photoelectric detection module; 631a. The second avalanche photodiode; 631b. The second temperature control module; 631b-1. The second refrigerator; 631b-2. The second heater; 631b-3. The second temperature sensor; 631c. The second packaging box; 632. The bias module; 633. The clock module; 634. The gate pulse module; 634a. The phase-locked loop circuit; 634b. The frequency divider; 634c. The second signal amplifier; 635. The noise suppression module; 635a. The band-pass filter; 635b. The low-pass filter; 635c. The third signal amplifier; 636. The pulse shaping module; 636a. The pulse amplitude detector; 636b. The pulse shaping circuit; 636c. The second analog-to-digital converter; 637. The photon counter; 7. The optical fiber to be tested.

DETAILED DESCRIPTION

In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following further describes how the present invention is implemented in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the present invention provides an OTDR device based on multi-channel optical fiber optical signal monitoring, which includes a main control unit 1, an optical sending unit 2, an optical branching unit 3, an oscilloscope unit 4, N coupling units 5 and N optical branch detection units 6; the main control unit 1 is connected to the optical sending unit 2 and the oscilloscope unit 4 respectively; the optical sending unit 2 is connected to the optical branching unit 3, and the optical branching unit 3 is correspondingly connected to N coupling units 5, and the input end of each coupling unit 5 is correspondingly connected to an output end of the optical branching unit 3 and an optical branch detection unit 6, and the output end of each coupling unit 5 is correspondingly connected to an optical fiber 7 to be tested; each optical branch detection unit 6 is correspondingly connected to the main control unit 1.

As shown in FIG2 , in this embodiment, the main control unit 1 includes a single chip microcomputer 11, a pulse signal generator 12, a signal attenuation driver 13 and a data processor 14, and the pulse signal generator 12, the signal attenuation driver 13 and the data processor 14 are respectively connected to the single chip microcomputer 11;

The optical transmission unit 2 includes a pulse light source 21 and an adjustable attenuator 22. The pulse light source 21 is connected to the pulse signal generator 12 and the adjustable attenuator 22 respectively. The adjustable attenuator 22 is connected to the signal attenuation driver 13 and the optical splitter unit 3 respectively. The pulse light source 21 emits high-speed near-infrared light in the 1550nm band, and the optical splitter unit 3 is a 1xN splitter.

The oscilloscope unit 4 is a waveform display, and the waveform display is provided with N display areas corresponding to the waveform curve of the detection light output by the optical branch detection unit 6;

Each coupling unit 5 is a directional coupler or a circulator;

Each optical branching detection unit 6 includes a 1×2 optical splitter 61 , a common detection unit 62 and a single photon detection unit 63 .

Wherein, N is an integer ≥ 2. According to the usual window viewing habits, it is best to set N equal to 4.

As shown in FIG3 , each common detection unit 62 includes a first photoelectric detection module 621, a filter 622, a first signal amplifier 623 and a first analog/digital converter 624 connected in sequence, and the input end of each first photoelectric detection module 621 is correspondingly connected to an output port of a 1x2 optical splitter 61, and each first analog/digital converter 624 is also correspondingly connected to the data processor 14 of the main control unit 1;

Each first photoelectric detection module 621 includes a first avalanche photodiode 621a, a first temperature control module 621b and a first packaging box 621c. Each first temperature control module 621b includes a first refrigerator 621b-1, a first heater 621b-2 and a first temperature sensor 621b-3. Each first refrigerator 621b-1 and the first heater 621b-2 are respectively connected to the single-chip microcomputer 11 of the main control unit 1. Each first temperature sensor 621b-3 is respectively connected to the single-chip microcomputer 11 of the main control unit 1 and a pin of a first avalanche photodiode 621a. The first avalanche photodiode 621a, the first refrigerator 621b-1, the first heater 621b-2 and the first temperature sensor 621b-3 corresponding to each first photoelectric detection module 621 are correspondingly packaged in a first packaging box. In 621c, each first temperature control module 621b adjusts the temperature in the corresponding first packaging box body 621c through the first refrigerator 621b-1 and the first heater 621b-2, and the first temperature sensor 621b-3 packaged in the corresponding first packaging box body 621c feeds back the sensed working temperature of the first avalanche photodiode 621a to the single-chip microcomputer 11 of the main control unit 1 in real time, and the first refrigerator 621b-1 and the first heater 621b-2 are controlled by the single-chip microcomputer 11 to control the cooling or heating control, so as to realize the temperature control in the first packaging box body 621c, so that the first avalanche photodiode 621a is always at a suitable working temperature, thereby effectively avoiding the unstable performance of the first avalanche photodiode 621a caused by the temperature increase, which affects the accuracy of the light intensity signal detection result of the ordinary detection unit.

As shown in FIG4 , each single photon detection unit 63 includes a second photodetection module 631 , a bias module 632 , a clock module 633 , a gate pulse module 634 , a noise suppression module 635 , a pulse shaping module 636 and a photon counter 637 ;

The input end of each bias module 632 is connected to the single-chip microcomputer 11 of the main control unit 1, and the output end of each bias module 632 is connected to the input end of a second photoelectric detection module 631. The input end of each second photoelectric detection module 631 is also connected to an output port of a 1x2 optical splitter 61 and an output end of a gate pulse module 634 respectively. The other output port of each 1x2 optical splitter 61 is connected to the input end of a first photoelectric detection module 621. The output end of each second photoelectric detection module 631 corresponds to a noise suppression module 635, a pulse shaping module 636 and a photon counter 637 connected in sequence. The input end of each gate pulse module 634 is connected to the single-chip microcomputer 11 and a clock module 633 of the main control unit 1 respectively; each clock module 633 is also connected to the pulse signal generator 12 and the single-chip microcomputer 11 of the main control unit 1 respectively, and each photon counter 637 is also connected to the data processor 14 of the main control unit 1 respectively.

Each second photoelectric detection module 631 includes a second avalanche photodiode 631a, a second temperature control module 631b and a second packaging box 631c; each second temperature control module 631b includes a second refrigerator 631b-1, a second heater 631b-2 and a second temperature sensor 631b-3, each second refrigerator 631b-1 and a second heater 631b-2 are respectively connected to the single-chip microcomputer 11 of the main control unit 1, each second temperature sensor 631b-3 is respectively connected to the single-chip microcomputer 11 of the main control unit 1 and a pin of a second avalanche photodiode 631a, and the second avalanche photodiode 631a, the second refrigerator 631b-1, the second heater 631b-2 and the second temperature sensor 631b-3 corresponding to each second photoelectric detection module 631 are correspondingly packaged in a second packaging box. In 631c, each second temperature control module 631b adjusts the temperature inside the corresponding second packaging box body 631c through the second refrigerator 631b-1 and the second heater 631b-2, and the first temperature sensor 631b-3 packaged in the corresponding second packaging box body 631c feeds back the sensed working temperature of the second avalanche photodiode 631a to the single-chip microcomputer 11 of the main control unit 1 in real time, and the second refrigerator 631b-1 and the second heater 631b-2 are controlled by the single-chip microcomputer 11 to control the cooling or heating control, so as to realize the temperature control inside the first packaging box body 621c, so that the second avalanche photodiode 631a is always at a suitable working temperature, thereby effectively avoiding the performance instability of the second avalanche photodiode 631a caused by the temperature increase, affecting the accuracy of the light intensity signal detection result of the single photon detection unit.

Each bias module 632 is a voltage source module, and is respectively connected to the microcontroller 11 of the main control unit 1 and to the cathode of a second avalanche photodiode 631a; each bias module 632 is used to provide the reverse bias voltage required for operation for the second avalanche photodiode 631a connected thereto.

Each gate pulse module 634 is a gate pulse generator, and is respectively connected to a clock module 633 and a bias module 632. As shown in FIG5 , each gate pulse module 634 includes a phase-locked loop circuit 634a, a frequency divider 634b and a second signal amplifier 634c. The output end of each phase-locked loop circuit 634a is correspondingly connected to a second signal amplifier 634c, and the input end of each phase-locked loop circuit 634a is correspondingly connected to a clock module 633. Each phase-locked loop circuit 634a includes a phase detector 634a-1, a loop filter 634a-2 and a voltage-controlled oscillator 634a-3 connected in sequence; each gate pulse module 634 is used to output a gate control signal to control the charge and discharge of the bias module 632 connected thereto, thereby generating a reverse bias voltage loaded on the second avalanche photodiode 631a, so as to control the avalanche and quenching process of the second avalanche photodiode 631a.

When the reverse bias voltage generated by the bias module 632 is loaded on the second avalanche photodiode 631a and is greater than or equal to the avalanche voltage of the second avalanche photodiode 631a, the photons returning from the optical fiber 7 to be tested through Rayleigh scattering and Fresnel reflection will be incident on the second avalanche photodiode 631a to generate a large number of photogenerated carriers, that is, to form an avalanche signal;

When the reverse bias voltage generated by the bias module 632 is loaded on the second avalanche photodiode 631a and is less than the avalanche voltage of the second avalanche photodiode 631a, the photons returning from the optical fiber 7 to be tested through Rayleigh scattering and Fresnel reflection are insufficient to generate photogenerated carriers, that is, the second avalanche photodiode 63a is quenched;

Each clock module 633 is used to control the synchronous triggering of the gate pulse module 634 and the pulse signal generator 12 connected thereto, so that the gate signal output by the gate pulse module 634 and the pulse light signal emitted by the pulse signal generator 12 are loaded onto the second avalanche photodiode 631a in a clock manner, so that the second avalanche photodiode 631a works in the Geiger gating mode, thereby realizing single-photon level light intensity signal detection.

Each noise suppression module 635 comprises a bandpass filter 635a, a low-pass filter 635b and a third signal amplifier 635c; each bandpass filter 635a input end is correspondingly connected to an output end of a gate pulse module 634, and each bandpass filter 635a output end is correspondingly connected to a cathode of a second avalanche photodiode 631a; each low-pass filter 635b input end is correspondingly connected to an anode of a second avalanche photodiode 631a, and each low-pass filter 635b output end is correspondingly connected to an input end of a third signal amplifier 635c; each third signal amplifier 635c output end is correspondingly connected to a pulse shaping module 636;

Each bandpass filter 635a is used to filter out the sideband noise and harmonic noise signal brought by the gate control signal output by the corresponding gate pulse module 634;

Each low-pass filter 635b is used to filter out the noise signal introduced by the gate control signal output by the corresponding gate pulse module 634 and produced after the photoelectric conversion by the corresponding second avalanche photodiode 631a, so as to obtain an effective photogenerated carrier avalanche signal therefrom.

Each pulse shaping module 636 includes a pulse amplitude detector 636a, a pulse shaping circuit 636b and a second analog/digital converter 636c; each pulse amplitude detector 636a input end is correspondingly connected to a third signal amplifier 636c output end, each pulse amplitude detector 636a output end is correspondingly connected to a pulse shaping circuit 636b input end, each pulse shaping circuit 636b output end is correspondingly connected to a second analog/digital converter 636c input end, each second analog/digital converter 636c output end is correspondingly connected to a photon counter 637 input end, and each photon counter 637 output end is correspondingly connected to the data processor 14 of the main control unit 1.

Each pulse shaping module 636 is used to shape the acquired effective avalanche analog signal into a standard digital signal and output it to the digital processor 14 of the main control unit. After analysis and processing by the digital processor 14, the corresponding OTDR detection light waveform signal is displayed in the corresponding display area on the waveform display.

In this embodiment, the first avalanche photodiode 621a and the second avalanche photodiode 631a are InGaAs or InP avalanche photodiodes.

Finally, it should be noted that the above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present invention.

Claims (5)

1. An OTDR device based on multi-channel optical fiber optical signal monitoring, characterized in that it comprises a main control unit (1), an optical transmission unit (2), an optical branching unit (3), an oscilloscope unit (4), N coupling units (5) and N optical branch detection units (6), wherein the main control unit (1) is connected to the optical transmission unit (2) and the oscilloscope unit (4), respectively, the optical transmission unit (2) is connected to the optical branching unit (3), the optical branching unit (3) is connected to the N coupling units (5) respectively, the input end of each coupling unit (5) is connected to the optical branching unit (3) and one of the optical branch detection units (6), the output end of each coupling unit (5) is connected to an optical fiber to be tested (7), and each of the optical branch detection units (6) is connected to the main control unit (1) respectively; The main control unit (1) comprises a single-chip microcomputer (11), a pulse signal generator (12), a signal attenuation driver (13) and a data processor (14); the pulse signal generator (12), the signal attenuation driver (13) and the data processor (14) are respectively connected to the single-chip microcomputer (11); The optical transmission unit (2) comprises a pulse light source (21) and an adjustable attenuator (22), the pulse light source (21) being connected to the pulse signal generator (12) and the adjustable attenuator (22) respectively, and the adjustable attenuator (22) being connected to the signal attenuation driver (13) and the optical branching unit (3) respectively; Each of the optical splitting detection units (6) comprises a 1x2 optical splitter (61), a common detection unit (62) and a single photon detection unit (63); the input end of each of the 1x2 optical splitters (61) is correspondingly connected to a coupling unit (5); and the output end of each of the 1x2 optical splitters (61) is correspondingly connected to a common detection unit (62) and a single photon detection unit (63); Each of the common detection units (62) comprises a first photoelectric detection module (621), a filter (622), a first signal amplifier (623) and a first analog/digital converter (624) which are connected in sequence; each of the first photoelectric detection modules (621) is also correspondingly connected to an output port of a 1x2 optical splitter (61); each of the first analog/digital converters (624) is also correspondingly connected to a data processor (14) of the main control unit (1); each of the first photoelectric detection modules (621) comprises a first avalanche photodiode (621a), a first temperature control module (621b) and a first packaging box (621c); each of the first temperature control modules (621b) comprises a first refrigerator (621b-1) , a first heater (621b-2) and a first temperature sensor (621b-3), each of the first refrigerator (621b-1) and the first heater (621b-2) is respectively connected to the single chip computer (11) of the main control unit (1), each of the first temperature sensors (621b-3) is respectively connected to the single chip computer (11) of the main control unit (1) and a pin of a first avalanche photodiode (621a), and the first avalanche photodiode (621a), the first refrigerator (621b-1), the first heater (621b-2) and the first temperature sensor (621b-3) corresponding to each of the first photoelectric detection modules (621) are correspondingly packaged in a first packaging box (621c); Each of the single-photon detection units (63) comprises a second photoelectric detection module (631), a bias module (632), a clock module (633), a gate pulse module (634), a noise suppression module (635), a pulse shaping module (636) and a photon counter (637). Each of the bias modules (632) is respectively connected to a single-chip microcomputer (11) and a second photoelectric detection module (631) of the main control unit (1). Each of the clock modules (633) is respectively connected to a pulse signal generator (634) of the main control unit (1). 12) and a gate pulse module (634), each of the gate pulse modules (634) is respectively connected to the single chip computer (11) of the main control unit (1) and a second photoelectric detection module (631), each noise suppression module (635) is respectively connected to a second photoelectric detection module (631) and a pulse shaping module (636), each photon counter (637) is respectively connected to the data processor (14) of the main control unit (1) and a pulse shaping module (636), each of the second photoelectric detection modules (631 ) are connected to an output port of a 1x2 optical splitter (61), each of the second photodetection modules (631) comprises a second avalanche photodiode (631a), a second temperature control module (631b) and a second packaging box (631c); each of the second temperature control modules (631b) comprises a second refrigerator (631b-1), a second heater (631b-2) and a second temperature sensor (631b-3), each of the second refrigerator (631b-1) and the second heater (631b-2) being equally spaced. The second photoelectric detection module (631) is respectively connected to the single chip computer (11) of the main control unit (1), each of the second temperature sensors (631b-3) is respectively connected to the single chip computer (11) of the main control unit (1) and the pins of a second avalanche photodiode (631a), and the second avalanche photodiode (631a), the second refrigerator (631b-1), the second heater (631b-2) and the second temperature sensor (631b-3) corresponding to each of the second photoelectric detection modules (631) are correspondingly packaged in a second packaging box (631c); Each of the noise suppression modules (635) comprises a bandpass filter (635a), a low-pass filter (635b) and a third signal amplifier (635c); the input end of each of the bandpass filters (635a) is correspondingly connected to the output end of a gate pulse module (634), and the output end of each of the bandpass filters (635a) is correspondingly connected to the cathode of a second avalanche photodiode (631a); the input end of each of the low-pass filters (635b) is correspondingly connected to the anode of a second avalanche photodiode (631a), and the output end of each of the low-pass filters (635b) is correspondingly connected to the input end of a third signal amplifier (635c); and the output end of each of the third signal amplifiers (635c) is correspondingly connected to a pulse shaping module (636); Each bandpass filter (635a) is used to filter out the sideband noise and harmonic noise signal brought by the gate control signal output by the corresponding gate pulse module (634); Each low-pass filter (635b) is used to filter out the noise signal introduced by the gate control signal output by the corresponding gate pulse module (634) and produced after the photoelectric conversion by the corresponding second avalanche photodiode (631a), so as to obtain an effective photogenerated carrier avalanche signal therefrom. 2. The OTDR device based on multi-channel optical fiber optical signal monitoring according to claim 1 is characterized in that: the optical branching unit (3) is a 1xN splitter, the oscilloscope unit (4) is a waveform display, and the waveform display includes N waveform curve display areas; each of the coupling units (5) is a directional coupler or a circulator; wherein N is an integer ≥2. 3. The OTDR device based on multi-channel optical fiber optical signal monitoring according to claim 1 is characterized in that: each of the bias modules (632) is a voltage source module, and is respectively connected to the single chip microcomputer (11) of the main control unit (1) and to the cathode of a second avalanche photodiode (631a). 4. The OTDR device based on multi-channel optical fiber optical signal monitoring according to claim 1 is characterized in that: each of the gate pulse modules (634) is a gate pulse generator, and is respectively connected to a clock module (633) and to the cathode of a second avalanche photodiode (631a), each of the gate pulse modules (634) includes a phase-locked loop circuit (634a), a frequency divider (634b) and a second signal amplifier (634c), the output end of each phase-locked loop circuit (634a) is correspondingly connected to a second signal amplifier (634c), the input end of each phase-locked loop circuit (634a) is correspondingly connected to a clock module (633), and each phase-locked loop circuit (634a) includes a phase detector (634a-1), a loop filter (634a-2) and a voltage-controlled oscillator (634a-3) connected in sequence. 5. The OTDR device based on multi-channel optical fiber optical signal monitoring according to claim 1, characterized in that: each of the pulse shaping modules (636) comprises a pulse amplitude detector (636a), a pulse shaping circuit (636b) and a second analog/digital converter (636c); each input end of the pulse amplitude detector (636a) is correspondingly connected to the output end of a third signal amplifier (635c), each output end of the pulse amplitude detector (636a) is correspondingly connected to the input end of a pulse shaping circuit (636b), each output end of the pulse shaping circuit (636b) is correspondingly connected to the input end of a second analog/digital converter (636c), each output end of the second analog/digital converter (636c) is correspondingly connected to the input end of a photon counter (637), and each output end of the photon counter (637) is correspondingly connected to the data processor (14) of the main control unit (1).