A method, system, device and medium for non-destructive measurement of coupling coefficient of distributed side-pumped optical fiber

Abstract

The present application discloses a method, system, device and medium for non-destructive measurement of coupling coefficient of distributed side-pumped optical fiber, which relates to the field of testing of optical equipment. The method includes: obtaining an electrical beat signal of the distributed side-pumped optical fiber to be tested; obtaining the amplitude distribution of the beat signal intensity based on the electrical beat signal; the amplitude distribution of the beat signal intensity is an amplitude distribution containing coupling coefficient information of the pump energy coupled from the pump fiber to the signal fiber and the coupling coefficient information of the reverse process; based on the amplitude distribution of the beat signal intensity, normalizing the amplitude of the intensity at the initial point position to obtain the pump power in the distributed side-pumped optical fiber to be tested; fitting the pump power to obtain the coupling coefficient of the pump energy coupled from the pump fiber to the signal fiber and the coupling coefficient of the reverse process. The present application can solve the problem of the lack of high stability and reliability in the prior art for refined research on the coupling process.

Description

Technical Field

[0001] The present application relates to the field of testing of optical equipment, and in particular to a method, system, equipment and medium for non-destructive measurement of coupling coefficient of distributed side-pumped optical fiber. Background Art

[0002] Fiber lasers have the advantages of compact structure, high conversion efficiency, excellent beam quality and convenient thermal management, which makes them have broad application prospects in industrial processing, national defense, military, medical and scientific research. With the rapid development of double-cladding pumping technology and high-brightness pump sources, the output power of fiber lasers has been rapidly improved, but the thermal damage problem caused by excessive end-face power density in double-cladding pumping technology has brought great instability to the continuous increase of fiber laser power. On the contrary, changing the coupling area to distributed side-coupled cladding-pumped (DSCCP) fiber on the side of the fiber, also known as GTwave, composite fiber, etc., has improved these problems to a certain extent.

[0003] DSCCP optical fiber is composed of a signal optical fiber (including a core with gain capability) and several pump optical fibers, which are tightly fitted together. The signal optical fiber and the pump optical fiber are in contact with each other on the side. The pump light is injected from the pump optical fiber and coupled into the signal optical fiber through the side in the form of an evanescent wave.

[0004] Mainstream high-power pumping solutions include end-pumped combiners, side-pumped combiners, and distributed side-coupled cladding pumping. Among them, the end-pumped combiner technology is mature and has the widest application scenarios, but the reverse collector is difficult to prepare, the beam distortion is difficult to completely eliminate, and it is difficult to continuously improve the load capacity at high power. The side-pumped combiner has improved its beam distortion problem to a certain extent, but the preparation process is not mature and has not been realized in large-scale engineering applications. DSCCP optical fiber is naturally suitable for a variety of different pumping methods due to its own design, and the heat distribution is more uniform, which can effectively alleviate the current problems of double-clad optical fiber.

[0005] In the distributed side pumping scheme, the physical process in the DSCCP optical fiber can be divided into two processes: coupling and absorption. In the coupling process, the pump light is injected from the pump fiber end face of the DSCCP optical fiber and transmitted in the pump fiber. At the same time, part of the pump light is gradually coupled from the side to the signal fiber cladding. In the absorption process, the pump light coupled into the signal fiber cladding is absorbed by the rare earth ions doped in the signal fiber core and forms stimulated radiation, and finally the signal light injected from the signal fiber is amplified. A pump source is used to inject pump light of a certain pump power into the pump fiber. After the optical fiber is cut section by section, the output power is measured from the end face at the cut port with a power meter to obtain the values ​​of a series of discrete points at intervals, and the separation method is used to reduce the step size at the position where the numerical value of some discrete points is drastic to obtain a more accurate effect.

[0006] However, although the existing non-destructive measurement method of the coupling coefficient of distributed side-pumped optical fibers is feasible in practice, it still has many disadvantages. For example, the measurement steps are extremely complicated, time-consuming, the step size is large, the measurement is destructive, the measurement efficiency is low, and it cannot be reproduced. These disadvantages make the existing non-destructive measurement method of the coupling coefficient of distributed side-pumped optical fibers lack high stability and reliability for the refined study of the coupling process. Summary of the invention

[0007] The purpose of this application is to provide a method, system, device and medium for non-destructive measurement of the coupling coefficient of a distributed side-pumped optical fiber, which can solve the problem of the lack of high stability and reliability in the refined study of the coupling process in the prior art.

[0008] To achieve the above objectives, this application provides the following solutions:

[0009] In a first aspect, the present application provides a method for non-destructive measurement of coupling coefficient of distributed side-pumped optical fiber based on optical frequency domain reflection technology, comprising:

[0010] Acquire the electrical beat frequency signal of the distributed side-pumped optical fiber to be tested;

[0011] The amplitude distribution of the beat signal intensity is obtained based on the electrical beat signal; the amplitude distribution of the beat signal intensity is an amplitude distribution including coupling coefficient information of the pump energy from the pump fiber to the signal fiber and the reverse coupling coefficient information;

[0012] Based on the amplitude distribution of the beat frequency signal intensity, normalization is performed according to the amplitude of the intensity at the initial point position to obtain the pump power in the distributed side-pumped optical fiber to be tested;

[0013] The pump power is fitted to obtain the coupling coefficient of the pump energy from the pump fiber to the signal fiber and the reverse coupling coefficient.

[0014] Optionally, obtaining the amplitude distribution of the beat frequency signal intensity based on the electrical beat frequency signal specifically includes:

[0015] Determining the amplitude and initial phase of the beat signal strength based on the electrical beat signal;

[0016] determining a beat signal strength based on the amplitude and the initial phase;

[0017] Performing Fourier transform on the intensity of the beat frequency signal to obtain a frequency spectrum distribution;

[0018] Coordinate transformation is performed based on the frequency spectrum distribution to obtain the amplitude distribution of the beat frequency signal intensity.

[0019] Optionally, performing coordinate transformation based on the frequency spectrum distribution to obtain the amplitude distribution of the beat frequency signal intensity specifically includes:

[0020] The horizontal coordinate data of the spectrum distribution is converted into the longitudinal coordinate data of the distributed side-pumped optical fiber to be tested, and the amplitude of the beat signal intensity corresponding to the longitudinal coordinate in the distributed side-pumped optical fiber to be tested is obtained to generate the amplitude distribution of the beat signal intensity.

[0021] Optionally, the amplitude and initial phase of the beat frequency signal strength are expressed as:

[0022] ;

[0023] In the formula, Indicates the position of the distributed side-pumped fiber to be tested The amplitude of the beat frequency signal strength, Indicates the position of the distributed side-pumped fiber to be tested The initial phase of the beat frequency signal strength, represents the laser amplitude, represents the proportionality coefficient, represents the initial pump power, represents the initial frequency, Indicates delay, represents the sweep rate, It represents the coupling coefficient of pump energy from pump fiber to signal fiber, represents the opposite process coupling coefficient, is the natural logarithm, is the ratio of pi.

[0024] Optionally, the pump power in the distributed side-pumped optical fiber to be tested is expressed as:

[0025] ;

[0026] In the formula, Indicates the position of the distributed side-pumped fiber to be tested The pump power, Indicates the position of the distributed side-pumped fiber to be tested The amplitude distribution of the beat frequency signal intensity, represents the amplitude of the intensity at the initial point of the distributed side-pumped fiber to be tested, It represents the coupling coefficient of pump energy from pump fiber to signal fiber, represents the opposite process coupling coefficient, is the natural logarithm.

[0027] In a second aspect, the present application provides a distributed side-pumped optical fiber coupling coefficient non-destructive measurement system, comprising: a tunable light source, a first coupler, a second coupler, a photodetector, a circulator, and a processing module;

[0028] The laser output by the tunable light source is divided into two beams after passing through the first coupler; one beam of laser light is used as detection light and enters the distributed side-pumped optical fiber to be tested after passing through the circulator to form reverse Rayleigh scattered light, and the reverse Rayleigh scattered light formed is used as signal light; the other beam of laser light is used as reference light; the signal light passes through the circulator and coherently forms heterodyne interference with the reference light in the second coupler to obtain interference light; the interference light generates an electrical beat frequency signal after entering the photodetector;

[0029] The photodetector is electrically connected to the processing module; the processing module implements the above-mentioned distributed side-pumped optical fiber coupling coefficient non-destructive measurement method, and obtains the coupling coefficient of the pump energy in the distributed side-pumped optical fiber to be measured from the pump optical fiber to the signal optical fiber and the reverse process coupling coefficient based on the electrical beat frequency signal.

[0030] Optionally, the processing module includes: an oscilloscope and a host computer;

[0031] The photoelectric detector and the host computer are both electrically connected to the oscilloscope.

[0032] Optionally, the distributed side-pumped optical fiber coupling coefficient nondestructive measurement system completes the measurement of the distributed side-pumped optical fiber coupling coefficient based on optical frequency domain reflection technology.

[0033] In a third aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the above-mentioned method for non-destructive measurement of the coupling coefficient of a distributed side-pumped optical fiber.

[0034] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned method for non-destructive measurement of coupling coefficient of a distributed side-pumped optical fiber.

[0035] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0036] The present application provides a method, system, device and medium for non-destructive measurement of coupling coefficient of distributed side-pumped optical fiber. Based on optical frequency domain reflection technology, non-destructive and accurate measurement of coupling coefficient of distributed side-pumped optical fiber can be achieved. The amplitude distribution of beat frequency signal intensity is obtained based on the electrical beat frequency signal, which improves the speed of measuring coupling coefficient. At the same time, the present application adopts optical frequency domain reflection technology, which does not require cutting the length of optical fiber, improves the utilization efficiency of the entire section of distributed side-pumped optical fiber, and thus can solve the problem of lack of high stability and reliability in the refined study of coupling process in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 This is a schematic diagram of a flow chart of a method for non-destructive measurement of coupling coefficient of a distributed side-pumped optical fiber in one embodiment of the present application;

[0039] Figure 2 A schematic diagram of the (1+1) type DSCCP optical fiber structure provided in one embodiment of the present application;

[0040] Figure 3 A schematic diagram of the (N+1) type DSCCP optical fiber structure provided in one embodiment of the present application;

[0041] Figure 4 A schematic diagram of the (1+N) type DSCCP optical fiber structure provided in one embodiment of the present application;

[0042] Figure 5 A distribution diagram of pump power under different coupling coefficients provided in an embodiment of the present application;

[0043] Figure 6 A schematic diagram of the structure of a distributed side-pumped optical fiber coupling coefficient non-destructive measurement system provided in an embodiment of the present application;

[0044] Figure 7A schematic diagram of a DSCCP optical fiber reflection signal obtained by OFDR measurement according to an embodiment of the present application;

[0045] Figure 8 A schematic diagram of the structure of a computer device provided in one embodiment of the present application.

[0046] Description of reference numerals:

[0047] 101 - tunable light source, 102 - first coupler, 103 - second coupler, 104 - photodetector, 105 - circulator, 106 - distributed side-pumped optical fiber to be tested, 107 - processing module, 1a - detection light, 1b - reference light, 1c - signal light, 1d - interference light. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0049] For the sake of convenience, the present application takes the (1+1) type DSCCP optical fiber with the simplest structure as an example, but all the invention contents are also applicable to other types of (N+1) type and (1+N) type DSCCP optical fibers. Figure 2 As shown, the (N+1) type DSCCP optical fiber structure is as follows Figure 3 As shown, the (1+N) type DSCCP optical fiber structure is as follows Figure 4 shown.

[0050] In order to quantitatively describe the physical process in DSCCP optical fiber, three parameters can be introduced: , , To describe, is the coupling coefficient of the pump light from the pump fiber to the signal fiber, is the coupling coefficient of the opposite process, is the pump absorption coefficient in the signal fiber core, and Closely related to the coupling process, Closely related to the absorption process.

[0051] Similar to ordinary double-clad optical fibers, higher pump power is required to achieve higher power laser output. The upper limit of pump power that can be injected into DSCCP optical fibers is positively correlated with the fiber diameter, numerical aperture, pump, and laser brightness. Under the condition that the numerical aperture (NA) is difficult to increase, the common method to increase the upper limit of pump power injection is to increase the pump brightness and fiber diameter. The pump brightness is determined by the existing pumping methods and it is difficult to improve it. Increasing the fiber diameter can increase the upper limit of the input pump power, but in DSCCP optical fibers, this will increase the coupling coefficient. , In order to achieve the same laser output in theory, the length of the optical fiber needs to be increased. However, when the optical fiber is too long, problems such as stimulated Raman scattering, stimulated Brillouin scattering and reabsorption will occur. Therefore, how to balance the relationship between the core size and the coupling coefficient becomes crucial. At the same time, how to accurately calculate the coupling coefficient has also become a key issue in characterizing related characteristics.

[0052] In the existing known technology, the pump power in the pump fiber in the DSCCP fiber is considered to be and the pump power in the signal fiber , which should satisfy the following differential equation:

[0053] (1)

[0054] In the formula, is the longitudinal coordinate of the optical fiber, is the coupling coefficient of pump energy from pump fiber to signal fiber, is the reverse process coupling coefficient, is the pump absorption coefficient in the signal fiber core, is the pump light loss coefficient in the optical fiber, and the units of the above coefficients are .

[0055] When considering the problem of fitting the pump fiber and the signal fiber in the DSCCP fiber, in order to clearly and accurately study the coupling variation relationship of the pump power in different optical fibers, we first consider decoupling the coupling problem from the core absorption problem. The signal fiber is usually replaced by a passive fiber with no core gain but similar other parameters. = 0. Whether it is a pump fiber or a passive fiber without considering the core absorption, the pump light loss coefficient can be ignored within a limited length (usually tens of meters). Therefore, after simplifying the above formula (1), = =0 holds, and The distribution of and Based on this, we can get:

[0056] (2)

[0057] In solving the above formula (2), the initial condition is that = 0, the injected power is The pump light, = and =0, the corresponding solution of the equation is as follows:

[0058] (3)

[0059] From a theoretical analysis, when we know the different positions of the two optical fibers Where and After the distribution of Figure 5 As shown, after fitting, we can get and Based on the above coupling principles and assumptions, the fundamental difference between different measurement methods is and Distribution acquisition scheme.

[0060] In the known Chinese patent application CN117554034B, a pump source is used to inject pump light of a certain pump power into the pump fiber, and after the fiber is cut section by section, a power meter is used to measure the output power from the end face at the cut end to obtain a series of discrete points at intervals. and The value of and The step size can be reduced by changing the position of the drastic change to obtain a more accurate effect. However, although this scheme is feasible in practice, it still has many disadvantages. The measurement steps are extremely complicated, time-consuming, the step size is large, the measurement is destructive, the measurement efficiency is low, and it cannot be reproduced. These disadvantages make this method lack high stability and reliability for the refined study of the coupling process. Therefore, it is extremely important and urgent to design a scheme to measure the coupling coefficient of DSCCP optical fiber efficiently, accurately, stably and non-destructively.

[0061] In the field of fiber optic sensing, the reflection spectrum of the fiber Bragg grating will shift as the environment (such as temperature, stress, etc.) in which the fiber is located changes. By studying the frequency shift of the reflection spectrum, information about environmental changes can be obtained. The optical fiber itself can be equivalent to a continuously distributed weak random periodic Bragg grating, and its state change will cause the movement of the scattering spectrum. The most common one is the elastic scattering caused by the interaction with the optical fiber material when the light propagates axially but does not exchange energy - Rayleigh scattering. The frequency (wavelength) of the light remains unchanged after scattering. Rayleigh scattered light is isotropic in the propagation direction, and its intensity is inversely proportional to the fourth-order equation of the wavelength of the incident light. Part of the scattered light is totally reflected at the core-cladding interface and returns along the original path of the optical fiber axis, in the opposite direction of the propagation direction of the incident light. This part of the scattered light is called backward Rayleigh scattered light. The frequency information carried by this part of the reflected light can be used to obtain the state distribution characteristics of the optical fiber. This is also the basic principle of Optical Frequency Domain Reflectometry (OFDR) based on Rayleigh scattering.

[0062] Based on this, the present invention proposes a feedback-type efficient, fast and non-destructive measurement method based on OFDR to solve the measurement problem of DSCCP optical fiber coupling coefficient.

[0063] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0064] The differences in the coupling coefficient measurement methods in DSCCP optical fibers are mainly due to and In terms of information acquisition, this application provides non-destructive and efficient measurement in DSCCP optical fiber through OFDR. and Nondestructive measurement method of coupling coefficient of distributed side-pumped optical fiber, such as Figure 1 As shown, the method includes:

[0065] Step 11: Obtain the electrical beat frequency signal of the distributed side-pumped optical fiber to be tested.

[0066] Step 12: Obtaining the amplitude distribution of the beat signal intensity based on the electrical beat signal. The amplitude distribution of the beat signal intensity includes the coupling coefficient information of the pump energy from the pump fiber to the signal fiber and the reverse coupling coefficient information.

[0067] Among them, the amplitude and initial phase of the beat frequency signal strength are expressed as:

[0068] (4)

[0069] In the formula, Indicates the position of the distributed side-pumped fiber to be tested The amplitude of the beat frequency signal strength, Indicates the position of the distributed side-pumped fiber to be tested The initial phase of the beat frequency signal strength, represents the laser amplitude, represents the proportionality coefficient, represents the initial pump power, represents the initial frequency, Indicates delay, Indicates the sweep rate.

[0070] Step 13: Based on the amplitude distribution of the beat signal intensity, normalize the amplitude of the intensity at the initial point position to obtain the pump power in the distributed side-pumped optical fiber to be tested. The pump power in the distributed side-pumped optical fiber to be tested is expressed as:

[0071] (5)

[0072] In the formula, Indicates the position of the distributed side-pumped fiber to be tested The pump power, It represents the amplitude of the intensity at the initial point of the distributed side-pumped fiber to be tested.

[0073] Step 14: Fit the pump power to obtain the coupling coefficient of the pump energy from the pump fiber to the signal fiber and the reverse coupling coefficient. and of The distribution is fitted according to the above formula (5), and we can get and result.

[0074] In one embodiment of the present application, the implementation process of the above step 12 may include:

[0075] Step 12-1: Determine the amplitude and initial phase of the beat signal strength based on the electrical beat signal.

[0076] Step 12-2: Determine the strength of the beat signal based on the amplitude and the initial phase. The strength of the beat signal is expressed as:

[0077] (6)

[0078] In the formula, represents the beat frequency signal strength, represents the beat frequency, Indicates time.

[0079] Step 12-3: Perform Fourier transform on the beat frequency signal intensity to obtain the spectrum distribution.

[0080] Step 12-4: Perform coordinate transformation based on the spectrum distribution to obtain the amplitude distribution of the beat frequency signal strength. For example, for the horizontal coordinate of the spectrum distribution, Convert to , the vertical coordinate is the intensity amplitude of the corresponding coordinate position , so the spectrum distribution after further processing is and information distributed.

[0081] Another embodiment of the present application provides a distributed side-pumped optical fiber coupling coefficient non-destructive measurement system, such as Figure 6 As shown, the system includes: a tunable light source 101 , a first coupler 102 , a second coupler 103 , a photodetector 104 , a circulator 105 and a processing module 107 .

[0082] The laser output by the tunable light source 101 is divided into two beams after passing through the first coupler 102. One beam of laser light is used as the detection light 1a and enters the distributed side pump fiber 106 to be tested after passing through the circulator 105, forming reverse Rayleigh scattered light, and the formed reverse Rayleigh scattered light is used as the signal light 1c. The other beam of laser light is used as the reference light 1b. After passing through the circulator 105, the signal light 1c and the reference light 1b are coherently formed in the second coupler 103 to form heterodyne interference to obtain the interference light 1d. The interference light 1d enters the photodetector 104 to generate an electrical beat signal.

[0083] The photodetector 104 is electrically connected to the processing module 107. The processing module 107 implements the above-mentioned non-destructive measurement of the distributed side pump fiber coupling coefficient, and obtains the coupling coefficient of the pump energy in the distributed side pump fiber 106 to be measured from the pump fiber to the signal fiber and the reverse coupling coefficient based on the electrical beat frequency signal.

[0084] In another embodiment of the present application, a distributed side-pumped optical fiber coupling coefficient nondestructive measurement system completes the measurement of the distributed side-pumped optical fiber coupling coefficient based on OFDR; wherein the detection mechanism of OFDR is:

[0085] Tuning the laser frequency emitted by the light source 101 For periodic changes, within a cycle, Satisfies the following relationship:

[0086] (7)

[0087] For laser phase , which corresponds to the following (the influence of phase noise is not considered here):

[0088] (8)

[0089] in, is the initial phase.

[0090] Then for the reference light 1b, its light field is expressed as Relative to the reference light 1b, the signal light 1c has an additional optical path length of ( is the refractive index of the optical fiber, is the coordinate in the optical fiber), its phase is delayed , is the speed of light in vacuum, and the corresponding signal light 1c light field is At the same time, in order to consider the reflected light intensity and return light attenuation, When , the original reflection coefficient is , the optical fiber attenuation coefficient in reverse transmission is , then the reflection coefficient after attenuation is It can be expressed as:

[0091] (9)

[0092] The laser light field emitted by the tunable light source 101 and directly entering the second coupler 103 after being split by the first coupler 102 is: , whose amplitude is , the phase is After being split by the first coupler 102, the other beam passes through the circulator 105 and enters the distributed side-pumped optical fiber 106 to be tested. Its weak Rayleigh scattered light passes through the circulator 105 and enters the second coupler 103. The light field is , which increases the corresponding optical path compared to the reference tube, so the phase will be delayed by t- (The influence caused by the difference in fiber length inside the measurement system is ignored here, which can be eliminated through optimized design and has no obvious interference with the overall measurement results). At the same time, due to the weak Rayleigh scattering, only part of the power is reflected, so The amplitude is also factored decrease, so accordingly and Can be expressed as:

[0093] (10)

[0094] When the light source performs frequency sweeping, when the signal light 1c and the reference light 1b interfere with each other in the second coupler 103, the interference intensity can be calculated as:

[0095] (11)

[0096] in, , is the beat frequency. The first two terms in formula (11) are DC terms, which can be filtered out in signal monitoring. The real observable term is the third AC signal term. The AC signal term is extracted separately and defined as the beat frequency intensity , expressed as:

[0097] (12)

[0098] Beat frequency intensity The time-dependent term in the phase of , the phase changes linearly with time. At the same time, it can be analyzed from formula (12) that only when the frequency of the light source changes, the sweep rate The beat frequency signal component will only appear when the light source 101 is tuned.

[0099] In another embodiment of the present application, the process of OFDR and distributed side-pumped fiber detection can be described as follows:

[0100] In the above content, we have derived the simplified case The power distribution in the DSCCP fiber when . Next, we will derive the beat frequency signal and the coupling coefficient and association.

[0101] In the beat frequency signal, Determined by the light source, and is a constant, different positions Corresponding delay Therefore, after the beat frequency signal is transformed into the frequency domain by Fourier transform, different frequencies correspond to different positions. The frequency distribution spectrum corresponds to the reflection strength spectrum over the entire length of the optical fiber.

[0102] In the DSCCP fiber, the detection signal light 1c is injected from the pump fiber. Since the optical signal in the DSCCP fiber is coupled by the side (i.e., the coefficient and ) enters the signal fiber, causing the optical power distribution on the entire fiber to gradually decay to a stable value, and its variation law is described by formula (13).

[0103] (13)

[0104] In formula (12), Contains information about the reflectivity at different locations. Since in actual measurements, the fiber length is only tens of meters and the attenuation coefficient is extremely small, we can take an approximate The Rayleigh scattering intensity can be approximately considered to be proportional to the transmission power under the conditions of the same fiber size, refractive index, wavelength of the transmitted light and similar waveguide structure. The proportionality coefficient is (constant), then:

[0105] (14)

[0106] The beat frequency signal is expressed as follows:

[0107] (15)

[0108] Through the above theoretical analysis process, after the time domain beat frequency signal is transformed into the frequency domain by Fourier transform, the frequencies correspond to the positions one by one. The corresponding amplitude value on the spectrum corresponds to the transmission power at that location, which provides the power of the entire pump fiber obtained from the coherent detection signal of OFDR. Information pathways.

[0109] In another embodiment of the present application, the processing module 107 includes: an oscilloscope and a host computer.

[0110] The photodetector 104 and the host computer are both electrically connected to the oscilloscope.

[0111] In another exemplary embodiment of the present application, the process of implementing the distributed side-pumped optical fiber coupling coefficient non-destructive measurement method based on the above-mentioned distributed side-pumped optical fiber coupling coefficient non-destructive measurement system includes:

[0112] a) Take a distributed side-pumped optical fiber to be tested with a length of tens of meters, process both ends of it, and connect one end to the output end of the circulator (flange connection or fusion splicing can be used).

[0113] b) Turn on the distributed side-pumped fiber coupling coefficient non-destructive measurement system and start the tuned light source for linear frequency sweep.

[0114] c) aligning the coherent signal output by the second coupler to the center position of the photodetector.

[0115] d) The electrical signal output by the photodetector is transferred to the processing module. Through the above-mentioned non-destructive measurement method of the distributed side-pumped fiber coupling coefficient, the beat frequency signal is Fourier transformed to obtain the spectrum at different positions, that is, the amplitude of the beat frequency signal intensity in the distributed side-pumped fiber to be measured. .

[0116] e) For the result obtained in step d) Processing to obtain Then, Perform fitting and obtain and The results show that the non-destructive measurement of the distributed side-pumped optical fiber to be tested is completed.

[0117] In another exemplary embodiment of the present application, for a system that needs to meet commercial applications, it can be assembled and miniaturized as a whole so that it only needs to retain one optical fiber output end and one external signal output end. The optical fiber output end is connected to the distributed side-pumped optical fiber to be tested, and the signal output end is connected to an external computer or acquisition card.

[0118] In another exemplary embodiment of the present application, based on the above-mentioned distributed side-pumped fiber coupling coefficient non-destructive measurement system, a DSCCP fiber sample was measured in kind, and the following results were obtained during the measurement: Figure 7 The feedback signal diagram of OFDR is shown in Figure 1. The detection light enters from the left. The negative value area is the internal fiber of the distributed side-pumped fiber coupling coefficient non-destructive measurement system, the 0~2m area is the external transition fiber area after the mode field adaptation period, and the 2~30m area is the distributed side-pumped fiber to be tested. In the 2~12m area, due to the evanescent wave side coupling in the distributed side-pumped fiber to be tested, part of the light energy is coupled to the signal fiber, and the reflection intensity gradually decreases. In the 12~30m area, the coupling between the distributed side-pumped fiber to be tested and the signal fiber reaches a balanced state, and the reflection intensity tends to remain consistent. This signal feature is consistent with the coupling mechanism characteristics in the above-mentioned DSCCP fiber.

[0119] In summary, compared with the prior art, the solution provided by this application has the following advantages:

[0120] 1) Lossless: This application can obtain the power distribution characteristics in the pump fiber through OFDR without destroying the structure of the existing optical fiber, which is used to calculate the coupling coefficient, so that the side pump fiber can still be used normally after the optical fiber coupling coefficient is measured.

[0121] 2) High efficiency: Existing technologies are prone to miss points where the coupling curve changes suddenly when measuring the coupling coefficient. Relatively speaking, OFDR can more accurately measure the power curve distribution of each point in the entire optical fiber at a small distance step, thereby improving the utilization efficiency of the entire optical fiber.

[0122] 3) Fast: Existing technologies take several days to measure the coupling coefficient each time, but OFDR measurement only takes a few minutes, greatly improving the speed of measuring the coupling coefficient.

[0123] 4) Accuracy: The existing technology actually has an error in the length of the light intercepted when measuring the coupling coefficient, resulting in the actual measured power being a point near the expected measurement point, which leads to an error. This error is generated in the process of intercepting the optical fiber. In contrast, the OFDR used in this application does not require intercepting the optical fiber, making the measurement of the coupling coefficient more accurate.

[0124] In addition, in actual applications, the (1+1) distributed side pumping fiber can be replaced with a (1+N) or (N+1) type distributed side pumping fiber with other fiber numbers. OFDR can also be replaced with other technologies with similar distributed detection principles.

[0125] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 8 As shown. The computer device includes a processing module, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Among them, the processing module, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processing module of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the lossless measurement data of the coupling coefficient of the distributed side-pumped optical fiber. The input / output interface of the computer device is used to exchange information between the processing module and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processing module, a lossless measurement method for the coupling coefficient of the distributed side-pumped optical fiber is realized.

[0126] Those skilled in the art will understand that Figure 8 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components. In an exemplary embodiment, a computer device is provided, including a memory and a processing module, wherein a computer program is stored in the memory, and the processing module implements the steps in the above-mentioned method embodiments when executing the computer program.

[0127] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processing module, the steps in the above-mentioned method embodiments are implemented.

[0128] In an exemplary embodiment, a computer program product is provided, including a computer program, which implements the steps in the above-mentioned method embodiments when executed by a processing module.

[0129] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0130] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0131] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processing module involved in each embodiment provided in this application may be a general processing module, a central processing module, a graphics processing module, a digital signal processing module, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0132] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for non-destructive measurement of coupling coefficient of distributed side-pumped optical fiber, characterized in that: The distributed side-pumped optical fiber coupling coefficient lossless measurement method is implemented based on optical frequency domain reflection technology; the distributed side-pumped optical fiber coupling coefficient lossless measurement method includes: Acquire the electrical beat frequency signal of the distributed side-pumped optical fiber to be tested; The amplitude distribution of the beat signal intensity is obtained based on the electrical beat signal; the amplitude distribution of the beat signal intensity is an amplitude distribution including coupling coefficient information of the pump energy from the pump fiber to the signal fiber and the reverse coupling coefficient information; Based on the amplitude distribution of the beat signal intensity, the normalization process is performed according to the amplitude of the intensity at the initial point position to obtain the pump power in the distributed side-pumped optical fiber to be tested; the pump power in the distributed side-pumped optical fiber to be tested is expressed as: ； In the formula, Indicates the position of the distributed side-pumped fiber to be tested The pump power, Indicates the position of the distributed side-pumped fiber to be tested The amplitude distribution of the beat frequency signal intensity, represents the amplitude of the intensity at the initial point of the distributed side-pumped fiber to be tested, It represents the coupling coefficient of pump energy from pump fiber to signal fiber, represents the opposite process coupling coefficient, is the natural logarithm; Fitting the pump power to obtain the coupling coefficient of the pump energy from the pump fiber to the signal fiber and the reverse coupling coefficient; Wherein, obtaining the amplitude distribution of the beat frequency signal intensity based on the electrical beat frequency signal specifically includes: Determining the amplitude and initial phase of the beat signal strength based on the electrical beat signal; The beat signal strength is determined based on the amplitude and the initial phase; the amplitude and initial phase of the beat signal strength are expressed as: ； In the formula, Indicates the position of the distributed side-pumped fiber to be tested The amplitude of the beat frequency signal strength, Indicates the position of the distributed side-pumped fiber to be tested The initial phase of the beat frequency signal strength, represents the laser amplitude, represents the proportionality coefficient, represents the initial pump power, represents the initial frequency, Indicates delay, represents the sweep rate, It represents the coupling coefficient of pump energy from pump fiber to signal fiber, represents the opposite process coupling coefficient, is the natural logarithm, is the ratio of pi; Performing Fourier transform on the intensity of the beat frequency signal to obtain a frequency spectrum distribution; Coordinate transformation is performed based on the frequency spectrum distribution to obtain the amplitude distribution of the beat frequency signal intensity.

2. The method for nondestructive measurement of coupling coefficient of distributed side-pumped optical fiber according to claim 1, characterized in that: Coordinate transformation is performed based on the frequency spectrum distribution to obtain the amplitude distribution of the beat frequency signal intensity, specifically including: The horizontal coordinate data of the spectrum distribution is converted into the longitudinal coordinate data of the distributed side-pumped optical fiber to be tested, and the amplitude of the beat signal intensity corresponding to the longitudinal coordinate in the distributed side-pumped optical fiber to be tested is obtained to generate the amplitude distribution of the beat signal intensity.

3. A distributed side-pumped optical fiber coupling coefficient non-destructive measurement system, characterized in that: The distributed side-pumped optical fiber coupling coefficient non-destructive measurement system comprises: a tunable light source, a first coupler, a second coupler, a photodetector, a circulator and a processing module; The laser output by the tunable light source is divided into two beams after passing through the first coupler; one beam of laser light is used as detection light and enters the distributed side-pumped optical fiber to be tested after passing through the circulator to form reverse Rayleigh scattered light, and the reverse Rayleigh scattered light formed is used as signal light; the other beam of laser light is used as reference light; the signal light passes through the circulator and coherently forms heterodyne interference with the reference light in the second coupler to obtain interference light; the interference light generates an electrical beat frequency signal after entering the photodetector; The photodetector is electrically connected to the processing module; the processing module implements the non-destructive measurement method of the distributed side-pumped optical fiber coupling coefficient as described in any one of claims 1-2, and obtains the coupling coefficient of the pump energy in the distributed side-pumped optical fiber to be measured from the pump optical fiber to the signal optical fiber and the coupling coefficient of the reverse process based on the electrical beat frequency signal.

4. The distributed side-pumped optical fiber coupling coefficient non-destructive measurement system according to claim 3, characterized in that: The processing module includes: an oscilloscope and a host computer; The photoelectric detector and the host computer are both electrically connected to the oscilloscope.

5. The distributed side-pumped optical fiber coupling coefficient non-destructive measurement system according to claim 3, characterized in that: The distributed side-pumped optical fiber coupling coefficient nondestructive measurement system completes the measurement of the distributed side-pumped optical fiber coupling coefficient based on the optical frequency domain reflection technology.

6. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method for non-destructive measurement of the coupling coefficient of a distributed side-pumped optical fiber according to any one of claims 1 to 2.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for non-destructive measurement of the coupling coefficient of a distributed side-pumped optical fiber according to any one of claims 1 to 2 is implemented.

Images