WO2017054564A1

WO2017054564A1 - Laser phase noise cancellation device, system, and method

Info

Publication number: WO2017054564A1
Application number: PCT/CN2016/091043
Authority: WO
Inventors: 何祖源; 樊昕昱; 郭勇; 朱松林; 印永嘉; 刘庆文; 马麟; 杜江兵; 王彬
Original assignee: 中兴通讯股份有限公司
Priority date: 2015-09-28
Filing date: 2016-07-22
Publication date: 2017-04-06
Also published as: CN106556415A

Abstract

A laser phase noise cancellation device, system, and method. The device comprises: a Mach-Zehnder interferometer, and an optical fiber delay ring. The optical fiber delay ring is coupled via a first photo coupler to a reference arm of the Mach-Zehnder interferometer, and comprises a serial-connected acoustic-optic modulator and optical fiber delay, wherein the optical fiber delay has a preconfigured length less than or equal to a coherence length of a laser.

Description

Laser phase noise canceling device, system and method

Technical field

The present application relates to, but is not limited to, the field of optical fiber detection, and in particular, to a laser phase noise cancellation device, system and method.

Background technique

In recent years, light reflectometer technology has attracted more and more attention due to its ability to implement distributed measurements. It mainly includes Optical Time Domain Reflectometer (OTDR) and Optical Frequency Domain Reflectometer (OFDR). Among them, OTDR technology is widely used due to its relatively simple implementation and long-distance distributed measurement. However, the spatial resolution of OTDR technology can only reach the order of meters, which limits its applications in certain areas with high spatial resolution requirements, such as aerospace and building health monitoring. In contrast, the OFDR technology has a spatial resolution of the order of centimeters, but its detection distance is limited by the coherence length of the laser. When the measured distance exceeds the coherence length, the spatial resolution and signal-to-noise ratio drop sharply due to the influence of the laser phase noise.

In order to eliminate the influence of laser phase noise and achieve a longer measurement range, domestic and foreign scholars have proposed several improved methods of OFDR.

For example, the non-uniform fast Fourier transform can solve the problem of frequency domain non-uniform sampling due to laser phase noise, and can achieve theoretical spatial resolution, but its measurement distance cannot exceed the coherence length of the laser.

For example, the phase noise compensation OFDR technique and the OFDR phase noise compensation technique based on the de-slanting filter can realize distributed measurement of spatial resolution on the order of tens of kilometers.

However, the above two methods all implement phase noise compensation through software data processing, which requires a large amount of calculations to obtain measurement results and is complicated to implement.

In view of the low spatial resolution of long-distance measurement in the optical frequency domain reflectometer technology in the related art, an effective solution has not been proposed yet.

Summary of the invention

The following is an overview of the topics detailed in this document. This summary is not intended to limit the claims The scope of protection.

Embodiments of the present invention provide a laser phase noise canceling apparatus, system, and method, which solve the problem that the optical frequency domain reflectometer technology has low spatial resolution for long distance measurement in the related art.

A laser phase noise canceling apparatus comprising a Mach-Zehnder interferometer, the phase noise canceling apparatus further comprising: a fiber delay loop, wherein the fiber delay loop is coupled to the Mach-Zehnder by a first optical coupler On the reference arm of the interferometer, the fiber delay loop includes a series of acousto-optic modulators and a predetermined length of delay fiber, wherein the predetermined length is less than or equal to the coherence length of the laser.

Optionally, the fiber delay ring further includes: an erbium doped fiber amplifier and an optical band pass filter, wherein the erbium doped fiber amplifier, the optical band pass filter, the acousto-optic modulator, and the delay fiber Serially connected in series along the reference beam propagation direction on the reference arm; or reference to the erbium doped fiber amplifier, the optical bandpass filter, the delay fiber, and the acousto-optic modulator along the reference arm The beam propagation direction is connected in series.

Optionally, the fiber delay ring further includes: an isolator configured to isolate the reverse beam, wherein the acousto-optic modulator, the delay fiber, and the isolator propagate along a reference beam on the reference arm The directions are serially connected in sequence; or the delay fiber, the acousto-optic modulator, and the isolator are sequentially connected in series along a reference beam propagation direction on the reference arm.

Optionally, the Mach-Zehnder interferometer comprises: the reference arm, the detecting arm and the second optical coupler, wherein the second optical coupler and the input end of the reference arm and the detecting arm The input terminal is connected to divide the frequency sweep signal generated by the external modulated swept source device into a reference beam and a probe beam, and send the reference beam to the reference arm, and send the probe beam to the probe arm The probe arm includes a circulator including a first port, a second port, a third port, and a fourth port, wherein the first port is configured to receive the probe beam and to detect the probe beam Sending from the second port, the second port is configured to be connected to the fiber to be tested, the third port is configured to receive a backscattered light beam reflected by the fiber to be tested, and the fourth port is set to Transmitting the backscattered beam into a third optocoupler; an output of the reference arm coupled to the third optocoupler, configured to feed a reference beam on an output of the reference arm into the Third optocoupler, A reference beam on the output of the reference arm is caused to interfere with the backscattered beam.

Optionally, the delay fiber is placed in a sound insulating medium.

Optionally, the delay fiber is a single mode fiber having a length of 10 kilometers.

A laser phase noise canceling system comprising the above laser phase noise canceling device, an external modulated swept source device, and a photodetection and data acquisition module; wherein the external modulated swept source device, the laser phase noise canceling device, and The photodetection and data acquisition module is sequentially connected; the external modulation swept source device is configured to generate a swept beam; the photodetection and data acquisition module is configured to process the interference beam output by the laser phase noise canceling device .

Optionally, the photodetection and data acquisition module comprises: a balanced photodetector and a data acquisition card connected to the balanced photodetector, wherein the balanced photodetector is configured to photoelectrically convert the interference beam The data acquisition card is configured to convert the photoelectrically converted analog signal into a digital signal.

A laser phase noise cancellation method includes: circulating a reference beam coupled from a first optical coupler on a reference arm of a Mach-Zehnder interferometer into a fiber delay loop, and causing the reference beam to be in the fiber delay loop Each transmission in the transmission passes through a predetermined length of the delay fiber and performs a frequency shift of a predetermined frequency; a reference beam on the output end of the reference arm is sent to the third optical coupler, and the output end of the reference arm is made The upper reference beam interferes with the backscattered beam output from the detection arm of the Mach-Zehnder interferometer to obtain an interference beam; the interference beam is processed by a photodetection and data acquisition module.

By adopting the embodiment of the present invention, a phase noise canceling device including a Mach-Zehnder interferometer and a fiber delay loop is adopted, wherein the fiber delay loop is coupled to the reference arm of the Mach-Zehnder interferometer through the first optical coupler, and the optical fiber The delay loop includes a series of acousto-optic modulators and a predetermined length of delay fiber, wherein the predetermined length is less than or equal to the coherence length of the laser, which solves the low spatial resolution of the long-distance measurement by the optical frequency domain reflectometer technology in the related art. The problem is to improve the spatial resolution of long-distance measurements by optical frequency domain reflectometry.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF abstract

1 is a block diagram showing the structure of a laser phase noise canceling apparatus according to an embodiment of the present invention;

2 is a first schematic diagram of a laser phase noise cancellation principle according to an embodiment of the present invention;

3 is a second schematic diagram of a laser phase noise cancellation principle according to an embodiment of the present invention;

4 is a block diagram showing the structure of a laser phase noise canceling system according to an embodiment of the present invention;

FIG. 5 is a flowchart of a laser phase noise canceling method according to an embodiment of the present invention; FIG.

6 is a structural block diagram of an OFDR system in accordance with a preferred embodiment of the present invention;

7 is a comparison of measurement results of compensated back and forth backscattering information according to an alternative embodiment of the present invention;

8 is a second comparison of measurement results of compensated back and forth backscattering information according to an alternative embodiment of the present invention;

9 is a comparison diagram of measurement results of spatial resolution before and after compensation in accordance with an alternative embodiment of the present invention.

Embodiments of the invention

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict.

It should be noted that the terms "first", "second" and the like in the specification and claims of the embodiments of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. order.

The present embodiment provides a laser phase noise canceling apparatus. FIG. 1 is a structural block diagram of a laser phase noise canceling apparatus according to an embodiment of the present invention. As shown in FIG. 1, the apparatus includes a Mach-Zehnder interferometer, and The apparatus further includes: an optical fiber delay loop (OFDL), wherein the fiber delay loop is coupled to the reference arm of the Mach-Zehnder interferometer through the first optical coupler (OC2), and the optical delay loop includes a series of acousto-optic modulators ( AOM) and a predetermined length of retardation fiber, wherein the predetermined length is no greater than the coherence length of the laser.

2 is a schematic diagram 1 of the principle of laser phase noise cancellation according to an embodiment of the present invention. As shown in FIG. 2, the laser phase noise canceling apparatus provided by the embodiment of the present invention can solve the problem of phase noise of a light source existing in the conventional OFDR technology. .

Let the acousto-optic modulator (ie, the frequency shifter) operate at a frequency that indicates the frequency of the beam that the acousto-optic modulator will pass each time; the length of the delay fiber in the OFDL is .

Then, the N×f _FS signal appearing in the frequency domain represents that the reference beam has passed N times in the OFDL, and the length of the corresponding reference fiber is N×1. If the fiber to be tested (FUT) is equivalently divided into many small segments, the length is shown in Figure 3, which is the length of the delay fiber in the OFDL, and L is the length of the fiber to be tested. At this time, the information of the first segment (Seg 1) can be obtained in the frequency domain 0HZ, the information of the second segment (Seg 2) can be obtained in the frequency domain 2×f _FS , and so on, the Nth segment (Seg N) The information can be obtained near N × f _FS .

It can be seen that the optical path difference (OPD) of each scattering point on the fiber to be tested is smaller than the coherence length of the laser. Therefore, the scattering information of each point on the fiber to be tested can be accurately obtained, the influence of phase noise is eliminated, and the OFDR technology is extended. Measuring range.

Therefore, the laser phase noise canceling device provided by the embodiment of the present invention can eliminate the influence of phase noise, and solve the problem that the optical frequency domain reflectometer technology has low spatial resolution for long distance measurement in the related art, and the optical frequency domain is improved. The spatial resolution of the reflectometer technology for long distance measurements.

Optionally, in order to compensate for the power loss of the reference beam in the fiber delay loop, an erbium doped fiber amplifier and an optical bandpass filter may be added at the reference beam entrance of the fiber delay loop, wherein the optical bandpass filter is set to filter out Amplified spontaneous emission (ASE) noise from 铒 fiber amplifiers. In the fiber delay loop, the erbium-doped fiber amplifier, the optical bandpass filter, the acousto-optic modulator, and the delay fiber are sequentially connected in series along the reference beam propagation direction on the reference arm; or the erbium doped fiber amplifier, the optical bandpass filter, and the delay The fiber optic and acousto-optic modulators are connected in series along the direction of propagation of the reference beam on the reference arm. That is, the serial order of the acousto-optic modulator and the delay fiber can be reversed.

Optionally, in order to eliminate the influence of the reflected light on the reference arm on the light delay loop, the isolator is isolated in series at the end of the fiber delay loop, that is, the light delay loop before the reference beam re-enters the reference arm (Isolator) For example, the acousto-optic modulator, the delay fiber, and the isolator are sequentially connected in series along the reference beam propagation direction on the reference arm; or the delay fiber, the acousto-optic modulator, and the isolator are sequentially connected in the direction of the reference beam propagation on the reference arm. . Through the isolator, the effect of reflected light on the delayed fiber is avoided.

Optionally, the Mach-Zehnder interferometer comprises: a reference arm, a detecting arm and a second optical coupler (OC1), wherein the second optical coupler is connected to the input end of the reference arm and the input end of the detecting arm, and is set to The sweep signal generated by the external modulated swept source device is divided into a reference beam and a probe beam, and the reference beam is sent to the reference arm, and the probe beam is sent to the probe arm; the probe arm includes a circulator (CIR), The circulator includes a first port, a second port, a third port, and a fourth port, wherein the first port is configured to receive the probe beam and send the probe beam from the second port, and the second port is configured to be connected to the fiber to be tested, The third port is configured to receive the backscattered beam reflected by the fiber to be tested, and the fourth port is configured to feed the backscattered beam into the third optical coupler (OC3); the output of the reference arm and the third optical coupler The connection is arranged to feed the reference beam on the output of the reference arm into the third optocoupler such that the reference beam at the output of the reference arm interferes with the backscattered beam. In the interference beam coupled by the third optical coupler, the reference beam of the reference fiber of the predetermined length of the predetermined length can be obtained in different frequency domains, thereby accurately segmenting the segments of the fiber to be tested in a segmented form. Measurement; finally, the measurement results of each segment are combined to obtain the measurement result of the fiber to be tested.

Optionally, the fiber-optic FUT pigtail of the fiber to be tested adopts a PC/APC interface.

Optionally, in order to eliminate interference from the external environment to the delay fiber, the delay fiber is placed in the soundproof medium, for example, the delay fiber is placed in the soundproof box.

Optionally, depending on the coherence length of the laser, the predetermined length of the delay fiber may be selected to be no longer than the length of the coherence length. For example, for a laser having a coherence length greater than or equal to 10 kilometers, the delay fiber has a length of 10 thousand. Meter's single mode fiber.

The embodiment also provides a laser phase noise cancellation system. FIG. 4 is a structural block diagram of a laser phase noise cancellation system according to an embodiment of the present invention. As shown in FIG. 4, the system includes the laser phase noise cancellation device 41 described above. The externally modulated swept source device 42 and the photodetection and data acquisition module 43 are in turn, wherein the externally modulated swept source device 41, the laser phase noise canceling device 42 and the photodetection and data acquisition module 43 are sequentially connected; the externally modulated swept source device 41 It is arranged to generate a swept beam; the photodetection and data acquisition module 43 is arranged to process the interfering beam output by the laser phase noise canceling device.

Optionally, the photodetection and data acquisition module 43 comprises: a balanced photodetector and a data acquisition card connected to the balanced photodetector, wherein the balanced photodetector is configured to photoelectrically convert the interference beam; the data acquisition card is set to be The analog signal obtained by photoelectric conversion is converted into a digital signal.

This embodiment further provides a laser phase noise canceling method. FIG. 5 is a flowchart of a laser phase noise canceling method according to an embodiment of the present invention. As shown in FIG. 5, the flow includes steps S501-S503:

Step S501, circulating a reference beam coupled from the first optical coupler on the reference arm of the Mach-Zehnder interferometer into the fiber delay loop, so that each transmission of the reference beam in the fiber delay loop is delayed by a predetermined length. The fiber is subjected to a frequency shift of a predetermined frequency.

Step S502, the reference beam on the output end of the reference arm is sent to the third optical coupler, so that the reference beam on the output end of the reference arm interferes with the backscattered beam outputted by the detecting arm of the Mach-Zehnder interferometer. An interference beam is obtained.

In step S503, the interference beam is processed by the photodetection and data acquisition module.

In order to make the description of the embodiments of the present invention more clear, the following description and description are made in conjunction with the exemplary embodiments.

An alternative embodiment of the present invention provides a long-distance optical frequency domain reflectometer technology method and apparatus, and relates to an optical frequency domain reflectometer technology in the field of distributed optical fiber sensing, which aims to compensate a light source phase in an optical frequency domain reflectometer technology. Noise, enabling long-distance fiber distributed sensing.

In an alternative embodiment of the invention, an optical fiber delay ring (OFDL) is added to the Mach-Zehnder interferometer reference arm in the OFDR system, the OFDL comprising a roll of 10 km fiber and an acousto-optic modulation operating at f _FS (ie frequency shifter). Therefore, the interference signal corresponding to the reference light of the N-turn in the OFDL appears near the frequency N×f _FS , so that the signals at different positions on the detection fiber can be accurately obtained at different frequencies. Through this method, the pre-validation experiment achieves a spatial resolution of 11cm within the measurement range of 20km, and does not require complicated post-data processing. The spatial resolution is improved by nearly 40 times compared with the phase noise compensation.

6 is a structural block diagram of an OFDR system according to an alternative embodiment of the present invention, and the symbols in FIG. 6 have the following meanings:

FL: narrow linewidth fiber laser; SSB-modulator: single sideband modulator; RF-Synthesizer: RF synthesizer; EDFA: erbium doped fiber amplifier; BPF: optical bandpass filter; OC: optical coupler; Isolator: light Isolator; AOM: acousto-optic modulator; CIR: optical circulator; PC: polarization controller; BPD: balanced photodetector; ADC: digital-to-analog converter; Delay fiber: delay fiber; Box: soundproof box; Trigger source: Trigger source.

As shown in FIG. 6, the OFDR system includes: an external modulation swept source, a Mach-Zehnder interferometer, an optical delay loop (OFDL), photodetection and data. Acquisition module; where:

Externally modulated swept source devices can include narrow linewidth fiber lasers, RF synthesizers, single sideband modulators, erbium doped fiber amplifiers (EDFAs), and optical bandpass filters.

Optionally, the narrow linewidth fiber laser has a working wavelength of 1550 nm, and the RF synthesizer generates a frequency sweeping electrical signal, and the radio frequency signal is modulated onto the optical signal by a single sideband modulator to generate a swept optical signal. The maximum gain of the EDFA is 22dB, which is set to compensate for the insertion loss caused by the modulator. The minimum bandwidth of the optical bandpass filter is 0.08nm and the insertion loss is 5dB. The optical bandpass filter is set to filter out the amplified spontaneous emission caused by the EDFA ( ASE) noise.

Optionally, the modulation bandwidth of the single sideband modulator exceeds 35 GHz, the sideband suppression ratio of the single frequency signal is more than 25 dB, and the sideband suppression ratio of the frequency sweeping signal is more than 20 dB.

The Mach-Zehnder interferometer can include two optocouplers (50/50 size), a circulator, a fiber to be tested (FUT), and a polarization controller.

The 50/50 optical coupler divides the optical signal into a reference beam and a probe beam, the reference light passes through the OFDL to the second optical coupler, the probe light enters the fiber to be tested through the circulator, and the backscattered light enters from the circulator 2 port. The second optocoupler interferes with the reference light, and the polarization controller is used to adjust the polarization state of the reference light.

Fiber Delay Loop (OFDL) can include: 10km delay fiber, acousto-optic modulator (AOM), erbium doped fiber amplifier (EDFA), and optical bandpass filters.

The 10km delay fiber is set to compensate the phase noise of the light source, and is placed in the soundproof box in order to eliminate external environmental interference. The AOM produces a fixed frequency offset from which the number of turns of light in the OFDL can be known. The EDFA is set to compensate for the power loss in the loop, and the optical filter is set to filter out the ASE noise from the EDFA.

Optionally, the delay fiber insertion loss is 3 dB; the AOM operating frequency is 40 MHz and the insertion loss is 4 dB.

Photoelectric detection and data acquisition modules include: balanced photodetectors and 8-bit data acquisition cards.

The balanced photodetector is set to photoelectric conversion, and the data acquisition card digitally converts the analog signal for later data processing. Optionally, the balanced photodetector has a bandwidth of 1.6 GHz and the data acquisition card has a sampling rate of 1 GHz.

The laser phase noise cancellation method will be described and illustrated using an example based on the OFDR system shown in FIG.

The laser produces seed light with a wavelength of 1550 nm. The RF synthesizer generates an RF signal with a sweep frequency range of 1 GHz and a sweep rate of 100 GHz/s. The sweep signal is modulated onto the seed light by a single sideband modulator. The single sideband modulator outputs swept light in the 1 GHz frequency range and corresponds to a theoretical spatial resolution of 10 cm in the OFDR. After the Swept Light is amplified by the EDFA, the ASE noise is filtered out by an optical filter and split into two paths through a 50/50 coupler. One way is to probe light, enter the fiber to be tested through the circulator, and the other is reference light. After the OFDL, the backscattered signal is coherent in the second coupler. The photodetector converts the optical signal into an electrical signal, the analog signal is digitized by an analog-to-digital converter, and the RF synthesizer and the data acquisition card are synchronized by an external signal source. Fourier transforming the acquired time domain signal yields a distributed backscattered signal along the measurement fiber without the need for complex phase compensation processes.

The OFDL consists of a 10km delay fiber and an acousto-optic modulator (AOM) that operates at a frequency shift. The AOM operates at 40MHz and the isolator is set to eliminate reverse light. In order to eliminate external environmental interference, the delay fiber is placed in the soundproof box. The delay fiber insertion loss is 3dB, the AOM insertion loss is 4dB, and the insertion loss is about 9dB for the entire loop including the connector. In order to increase the optical power, an EDFA is used in the loop, and the optical filter is used to filter out the ASE noise of the EDFA.

The fiber to be tested is two rolls of 10km single mode fiber (SMF) connected by a fiber optic connector. Figure 7 shows the backscattering information near the first fiber optic connector. The graph in the upper left corner of Fig. 7 is an enlarged view of the Fresnel reflection peak. The spatial resolution of 35 cm in the figure is the spatial resolution of the Fresnel reflection peak before compensation, and the spatial resolution of 10 cm is the compensated Fresnel reflection peak. Spatial resolution. The spatial resolution of the measured fiber-optic joint Fresnel reflection peak is 35 cm due to the influence of phase noise before compensation. By adopting the phase noise compensation method of the light source proposed by the embodiment of the present invention, the frequency domain is 80 MHz (double the AOM operating frequency). The Fresnel reflection peak produced by the first fiber connector was obtained nearby, and the reference light was circled twice in the OFDL and coherent with the signal light. The spatial resolution is 10 cm, which is consistent with the theoretical spatial resolution. Similarly, we obtained the Fresnel reflection peak of the fiber end connector to be tested near 160 MHz, and the reference light was surrounded by the signal light in the OFDL. As shown in FIG. 8, the spatial resolution of 380 cm in FIG. 8 is the spatial resolution of the Fresnel reflection peak before compensation, and the spatial resolution of 11 cm is the spatial resolution of the compensated Fresnel reflection peak. As can be seen from Figure 8, the compensation is obtained. The spatial resolution of the reflected peak is 11 cm, which is basically consistent with the theoretical spatial resolution. The source phase noise compensation method proposed by the alternative embodiment of the present invention increases the spatial resolution by 40 times compared to the 380 cm spatial resolution before compensation.

The source phase noise compensation method proposed by the alternative embodiment of the present invention has the worst compensation effect at ML/4 (where M is an odd number and L is a delay fiber length). At the worst compensation point, the optical path difference of the two arms of the Mach-Zehnder interferometer is. In order to detect the compensation effect of these points, the phase noise compensation before and after compensation is measured respectively, and the length is 5km and 8.1km (since the laboratory does not have 7.5) The km length fiber, using 8.1km fiber instead of), 10km, 12.5km, 15km, 17.5km and 20km fiber, and recording the spatial resolution of the end Fresnel reflection peak. The measurement results are shown in Fig. 9. At the point where these compensation effects are the worst, the spatial resolution in accordance with the theory is also obtained. Among them, all the measurements in Figure 9 were performed 10 times and averaged.

In summary, the laser phase noise cancellation scheme provided by the embodiment of the present invention can compensate the phase noise of the light source in the OFDR technology, and realize the distributed measurement of the spatial resolution of the centimeter level in the measurement range of several tens of kilometers or even hundreds of kilometers.

A computer readable storage medium storing computer executable instructions that, when executed by a processor, implement the laser phase noise cancellation method.

It will be apparent to those skilled in the art that each module or step of the above-described embodiments of the present invention can be implemented by a general-purpose computing device, which can be centralized on a single computing device or distributed across multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device such that they may be stored in the storage device by the computing device and, in some cases, may be different The steps shown or described herein are performed sequentially, or they are separately fabricated into a plurality of integrated circuit modules, or a plurality of the modules or steps are fabricated into a single integrated circuit module. Thus, embodiments of the invention are not limited to any specific combination of hardware and software.

The above is only an alternative embodiment of the present invention, and is not intended to limit the embodiments of the present invention. For those skilled in the art, the present invention may be variously modified and changed. Any modifications, equivalent substitutions, improvements, etc. within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Industrial applicability

Claims

A laser phase noise canceling device, comprising a Mach-Zehnder interferometer, characterized in that the phase noise canceling device further comprises: a fiber delay loop;

The fiber delay loop is coupled to a reference arm of the Mach-Zehnder interferometer by a first optical coupler, the fiber delay loop comprising a series of acousto-optic modulators and a predetermined length of delay fiber, wherein The predetermined length is less than or equal to the coherence length of the laser.
The laser phase noise canceling apparatus according to claim 1, wherein said fiber delay ring further comprises: an erbium doped fiber amplifier and an optical band pass filter, wherein

The erbium doped fiber amplifier, the optical band pass filter, the acousto-optic modulator, and the delay fiber are sequentially connected in series along a reference beam propagation direction on the reference arm; or

The erbium doped fiber amplifier, the optical band pass filter, the delay fiber, and the acousto-optic modulator are sequentially connected in series along a reference beam propagation direction on the reference arm.
The laser phase noise canceling apparatus according to claim 1, wherein the fiber delay ring further comprises: an isolator configured to isolate the reverse beam, wherein

The acousto-optic modulator, the delay fiber, and the isolator are sequentially connected in series along a reference beam propagation direction on the reference arm; or

The delay fiber, the acousto-optic modulator, and the isolator are sequentially connected in series along a reference beam propagation direction on the reference arm.
The laser phase noise canceling apparatus according to claim 1, wherein said Mach-Zehnder interferometer comprises: said reference arm, a detecting arm, and a second optical coupler;

The second optical coupler is connected to the input end of the reference arm and the input end of the detecting arm, and is configured to divide the frequency sweep signal generated by the external modulated swept source device into a reference beam and a probe beam, and a reference beam is sent to the reference arm, and the probe beam is sent to the probe arm;

The probe arm includes a circulator including a first port, a second port, a third port, and a fourth port, wherein the first port is configured to receive the probe beam and to transmit the probe beam Sending, by the second port, the second port is configured to be connected to the optical fiber to be tested, the third port is configured to receive a backscattered light beam reflected by the optical fiber to be tested, and the fourth port is configured to be The backscattered beam is sent to a third optocoupler;

An output end of the reference arm is coupled to the third optical coupler, configured to feed a reference beam on an output end of the reference arm to the third optical coupler, and output the reference arm The reference beam interferes with the backscattered beam.
The laser phase noise canceling apparatus according to claim 1, wherein said retardation fiber is placed in a sound insulating medium.
The laser phase noise canceling apparatus according to claim 1, wherein said delay fiber is a single mode fiber having a length of 10 kilometers.
A laser phase noise canceling system comprising the laser phase noise canceling device according to any one of claims 1 to 6, an external modulated swept source device, and a photodetection and data acquisition module;

The external modulation swept source device, the laser phase noise canceling device, and the photodetection and data acquisition module are sequentially connected;

The externally modulated swept source device is configured to generate a swept beam;

The photodetection and data acquisition module is configured to process an interference beam output by the laser phase noise cancellation device.
The laser phase noise cancellation system of claim 7 wherein said photodetection and data acquisition module comprises: a balanced photodetector and a data acquisition card coupled to said balanced photodetector;

The balanced photodetector is configured to perform photoelectric conversion on the interference beam;

The data acquisition card is configured to convert the photoelectrically converted analog signal into a digital signal.
A laser phase noise cancellation method includes:

Looping a reference beam coupled from the first optical coupler on the reference arm of the Mach-Zehnder interferometer into the fiber delay loop, causing each transmission of the reference beam in the fiber delay loop to pass a predetermined length Delaying the fiber and performing a frequency shift of a predetermined frequency;

Feeding a reference beam on the output end of the reference arm into the third optocoupler such that the reference beam on the output of the reference arm and the detection arm output of the Mach-Zehnder interferometer are facing away The scattered beams interfere to obtain an interference beam;

The interference beam is processed by a photodetection and data acquisition module.
A computer readable storage medium storing computer executable instructions that, when executed by a processor, implement the laser phase noise cancellation method of claim 9.