A system and method for testing collimation characteristics of a fiber collimator

Abstract

The application provides a system and method applied to collimation characteristic test of a fiber collimator, and belongs to the technical field of optical measurement. In a specific embodiment, the light path of an outgoing light beam sequentially passes through a polarization light splitting module, a collimator to be tested, a quarter-wave plate, and a mirror, and then returns to the polarization light splitting module along the original light path, and is guided to a photodetector through the polarization light splitting module. A processor receives a signal intensity value output by the photodetector, and determines the size of a divergence angle corresponding to any signal intensity value output by the photodetector according to a first mapping relationship measured in advance, wherein the first mapping relationship is a functional relationship between the signal intensity value output by the photodetector and the size of the divergence angle of the collimator to be tested. Based on the reversible principle of the light path, the size of the divergence angle of the collimator to be tested can be calculated according to the signal intensity value output by the photodetector, so that the structure of the collimator to be tested can be adjusted in real time, and the best collimation effect can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical measurement, and particularly relates to a system and method for testing collimation characteristics of a fiber collimator. BACKGROUND

[0002] The fiber collimator is a kind of precise optical device, and its main function is to convert the divergent light beam output from the fiber end into an approximately parallel light beam (also known as a collimated light beam). The beam divergence angle is a key parameter for evaluating the collimation performance of the fiber collimator, and generally the smaller the divergence angle, the higher the collimation quality.

[0003] At present, in actual application, the collimation performance of the light beam output by the fiber collimator is usually evaluated by using a beam quality analyzer or a shearing interferometer. However, both of the two methods have certain limitations: the beam quality analyzer is limited by the size of the detector, and it may be difficult to accurately measure the spot size when the spot size is large, while the shearing interferometer can be used for qualitative analysis of the collimation performance, but it is not convenient for directly quantitative measurement of the beam divergence angle. Therefore, the conventional beam quality analyzer or shearing interferometer may not fully meet the needs of all application scenarios when dealing with different spot sizes, especially when high-precision quantitative measurement of the divergence angle is required. SUMMARY

[0004] In view of the problem that the existing equipment cannot realize quantitative measurement of the divergence angle of an arbitrary light spot, the application aims to provide a system and method for testing collimation characteristics of a fiber collimator, which measures the divergence angle of an arbitrary light spot through the output signal of a photoelectric sensor, so as to adjust the structure of the fiber collimator and realize its best collimation effect.

[0005] In a first aspect, the embodiments of the present application provide a system for testing collimation characteristics of a fiber collimator, comprising a laser, a polarization beam splitting module, a quarter-wave plate, a mirror, a photoelectric detector and a processor.

[0006] The outgoing light beam of the laser enters the first port of the polarization beam splitting module, the polarization beam splitting module transmits the P-polarized light of the outgoing light beam and sends it to the collimation incident end of the to-be-measured collimator through the second port.

[0007] The to-be-measured collimator outputs a collimated light beam through the collimation incident end after collimating the P-polarized light, the collimated light beam reaches the mirror after passing through the quarter-wave plate, and the reflected light beam after being reflected by the mirror passes through the quarter-wave plate again to form S-polarized light sent to the collimation incident end of the to-be-measured collimator.

[0008] The to-be-measured collimator converges the S-polarized light and sends it to the second port of the polarization beam splitting module through the collimation incident end.

[0009] The polarization splitting module reflects the S-polarized light and sends the S-polarized light to the photodetector through the third port;

[0010] The processor is electrically connected to the photodetector, configured to acquire a signal intensity value output by the photodetector, and determine a divergence angle size of the collimator under test corresponding to the signal intensity value according to a first mapping relationship measured in advance, the first mapping relationship being a functional relationship between the signal intensity value output by the photodetector and the divergence angle size of the collimator under test.

[0011] In a possible implementation, the polarization splitting module comprises:

[0012] a half-wave plate configured to change a polarization state of an outgoing light beam input from the first port;

[0013] a polarization splitting prism configured to transmit P-polarized light in the outgoing light beam and output the P-polarized light from the second port, and configured to reflect S-polarized light input from the second port and output the S-polarized light from the third port.

[0014] In a possible implementation, the second port is provided with a first optical fiber flange, and the collimating incident end of the collimator under test is provided with a second optical fiber flange, and the first optical fiber flange and the second optical fiber flange are connected by an optical fiber.

[0015] In a possible implementation, the half-wave plate, the polarization splitting prism, the collimator under test, and the quarter-wave plate are coaxially arranged along a main optical axis of the laser, and the mirror is perpendicular to the main optical axis.

[0016] In a possible implementation, a set of lenses are arranged in the collimator under test.

[0017] The processor is further configured to adjust a relative position between the lenses and the collimating incident end according to the signal intensity value output by the photodetector, so as to adjust the divergence angle size of the collimator under test.

[0018] In a possible implementation, further comprising: an optical isolator, the optical isolator being located between the laser and the polarization splitting module, and configured to isolate the reflected laser beam.

[0019] In a second aspect, the embodiments of the present application further provide a method for testing collimation characteristics of a fiber collimator, and the method is applied to the system of any of the embodiments of the first aspect, and the method comprises:

[0020] determining a second mapping relationship between the signal intensity value output by the photodetector and a collimation parameter, the collimation parameter being at least one structural parameter in the collimator under test that affects the size of the divergence angle;

[0021] determining a third mapping relationship between the collimation parameter and the divergence angle of the collimator under test;

[0022] determining the first mapping relationship according to the second mapping relationship and the third mapping relationship.

[0023] In a possible implementation, the collimation parameter is the relative position of a set of lenses arranged in the collimator under test and the collimation exit end;

[0024] Correspondingly, the step of determining the second mapping relationship between the signal intensity value output by the photodetector and the collimation parameter comprises:

[0025] adjusting the relative position of the lenses and the collimation exit end for several times, and obtaining the signal intensity value output by the photodetector after each adjustment of the relative position of the lenses and the collimation exit end;

[0026] fitting the signal intensity values for several times, and determining the second mapping relationship between the signal intensity value and the collimation parameter according to the fitting result.

[0027] In a possible implementation, the step of obtaining the signal intensity value output by the photodetector after each adjustment of the relative position of the lenses and the collimation exit end comprises:

[0028] controlling the lenses to move along the main optical axis of the laser at a fixed step, and adjusting the interval distance between the lenses and the collimation exit end at equal intervals;

[0029] recording the signal intensity value output by the photodetector at different interval distances.

[0030] In a possible implementation, the step of determining the third mapping relationship between the collimation parameter and the divergence angle of the collimator under test comprises:

[0031] selecting part of the interval distances, and measuring the real divergence angle of the collimator under test corresponding to the part of the interval distances;

[0032] fitting the real divergence angles of the collimator under test at the part of the interval distances for several times according to the measured real divergence angles, and determining the third mapping relationship between the interval distance and the divergence angle of the collimator under test according to the fitting result.

[0033] This invention provides a system and method for testing the collimation characteristics of an optical fiber collimator. The system first collimates the P-polarized light in the outgoing beam, then reflects the collimated beam back to the collimator under test using a reversible optical path, and then guides the collimated beam into a photodetector through a polarization beam splitting module and outputs the corresponding signal intensity value.

[0034] Since a smaller divergence angle of the collimator under test means that more light beams can be reflected back to the collimator under test by the mirror and transmitted to the photodetector, the signal strength value output by the photodetector will be greater. Therefore, the signal strength value output by the photodetector can effectively reflect the size of the divergence angle of the collimator under test.

[0035] Furthermore, adjusting the structural parameters of the collimator under test can change its divergence angle, thereby affecting the signal strength. Therefore, based on this response relationship, the influence of structural adjustment of the collimator under test on the divergence angle can be systematically studied by detecting the signal strength value output by the photodetector, so as to find the optimal collimation parameters of the collimator under test and achieve the best collimation effect. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0037] Figure 1 This is a schematic diagram of a system structure for testing the collimation characteristics of an optical fiber collimator according to an embodiment of this application;

[0038] Figure 2 This is a schematic diagram of the structure of a polarization beam splitter module according to an embodiment of this application;

[0039] Figure 3 This is a schematic diagram of a system structure for testing the collimation characteristics of an optical fiber collimator according to another embodiment of this application;

[0040] Figure 4 This is a flowchart of a method for testing the collimation characteristics of an optical fiber collimator according to an embodiment of this application;

[0041] Figure 5 This is a flowchart of a method for testing the collimation characteristics of an optical fiber collimator according to another embodiment of this application;

[0042] Figure 6 for Figure 5 A graph showing the functional relationship between the interval distance and the divergence angle in the embodiment;

[0043] Figure 7 for Figure 5 The graph showing the functional relationship between signal strength and divergence angle in the example;

[0044] Figure 8A flow chart of a method for testing collimation characteristics of a fiber collimator according to another embodiment of the present application.

[0045] The specific embodiments of the present application have been shown by the above-described drawings, and will be described in more detail hereinafter. These drawings and detailed description are not intended to limit the scope of the concept of the present application in any way, but to explain the concept of the present application to those skilled in the art by referring to specific embodiments.

[0046] Explanation of Reference Signs:

[0047] 11 - laser; 12 - polarization beam splitting module; 121 - half wave plate; 122 - polarization beam splitting prism; 13 - collimator to be tested; 131 - lens; 14 - quarter wave plate; 15 - mirror; 16 - photodetector; 17 - processor; 18 - optical isolator. DETAILED DESCRIPTION

[0048] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers are used to indicate the same components throughout the drawings, unless otherwise specified. The embodiments described in the following exemplary embodiments are not meant to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0049] In the embodiments of the present application, the terms "first", "second", and the like are used to distinguish between similar or identical items or components having substantially the same function and role. Those skilled in the art will understand that the terms "first", "second", and the like do not limit the number and execution order, and the terms "first", "second", and the like do not necessarily mean different.

[0050] It should be noted that the terms "exemplary" or "for example" in the embodiments of the present application are used to represent an example, illustration, or description. Any embodiment or design scheme described as "exemplary" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the terms "exemplary" or "for example" are intended to present the relevant concept in a specific manner. In the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more.

[0051] It should be noted that "at the time of" in the embodiments of the present application can be at the moment when a certain condition occurs, or can be within a certain period of time after the occurrence of a certain condition, which is not specifically limited in the embodiments of the present application.

[0052] In order to clearly describe the technical solutions of the embodiments of the present application, the following briefly introduces some terms and technologies involved in the embodiments of the present application:

[0053] Half-wave plate: A half-wave plate is a birefringent crystal with a certain thickness, and when a normally incident light beam passes through it, the phase difference between ordinary light (o light) and extraordinary light (e light) is equal to π or an odd multiple thereof. The half-wave plate is mainly used to rotate polarized light and change the polarization state of polarized light. For example, when linearly polarized light is normally incident on a half-wave plate, the transmitted light is still linearly polarized light. When the angle between the vibration plane and the main section of the crystal is θ, the vibration plane of the transmitted linearly polarized light is rotated by 2θ.

[0054] Quarter-wave plate: Similar to the half-wave plate, when a normally incident light beam passes through a quarter-wave plate, the phase difference between ordinary light (o light) and extraordinary light (e light) is equal to π / 2 or an odd multiple thereof. The quarter-wave plate is mainly used to convert linearly polarized light into circularly polarized light or elliptically polarized light. When the polarization of the light and the optical axis plane (perpendicular to the natural cleavage plane) of the wave plate form an angle θ, the outgoing light is elliptically polarized light; when θ is equal to 45°, the outgoing light is circularly polarized light.

[0055] Polarizing beam splitter: A polarizing beam splitter is a cube structure obtained by coating a multilayer film structure on the hypotenuse of a right-angle prism. When light is incident at the Brewster angle, the P-polarized light in the light is directly transmitted, and the S-polarized light is reflected by the coated hypotenuse. The polarizing beam splitter is mainly used to separate the P-polarized light and the S-polarized light in a light beam, thereby playing the roles of polarizing, analyzing, and adjusting light intensity.

[0056] A fiber collimator is a precision optical device that mainly converts the divergent light beam output from the end of an optical fiber into a nearly parallel light beam (also known as a collimated light beam). The beam divergence angle is a key parameter for evaluating the collimation performance of a fiber collimator. Generally, the smaller the divergence angle, the higher the collimation quality. A fiber collimator also has the function of coupling an external nearly parallel light beam into an optical fiber.

[0057] In some application fields, such as cold atom interferometers, it is necessary to collimate Raman light to obtain collimated Raman light with small divergence angle characteristics, thereby obtaining a higher atomic transition frequency. Therefore, it is particularly important to accurately evaluate the collimation characteristics of a fiber collimator.

[0058] Currently in practical applications, the collimation performance of the output light beam of the fiber collimator is usually evaluated by using a beam quality analyzer or a shearing interferometer. However, both of the two methods have certain limitations: the beam quality analyzer is limited by the size of the detector, and it may be difficult to accurately measure the spot size when the spot size is large; although the shearing interferometer can be used for qualitative analysis of the collimation performance, it is often not convenient for directly quantitative measurement of the beam divergence angle. Therefore, the conventional beam quality analyzer or shearing interferometer may not fully meet the needs of all application scenarios when dealing with different spot sizes, especially when high-precision quantitative measurement of the divergence angle is required.

[0059] To solve the above problems, the embodiments of the present application provide a system and method applied to testing the collimation characteristics of a fiber collimator. The technical concept of the application is that based on the characteristics that the more the beams of the incident light, the greater the signal strength output by the photodetector, the application designs a device capable of reflecting the collimated light beam of the to-be-tested collimator back to the to-be-tested collimator and sending it to the photodetector for measurement. Since the smaller the divergence angle of the to-be-tested collimator, the smaller the spot, the more the light beams that can be reflected back to the to-be-tested collimator and reach the photodetector, and the greater the signal strength output by the photodetector, the signal strength value output by the photodetector can be used to effectively reflect the size of the divergence angle of the to-be-tested collimator. In addition, adjusting the structural parameters of the to-be-tested collimator will change its divergence angle, which in turn affects the signal strength. Therefore, based on this response relationship, the influence of the structural adjustment of the to-be-tested collimator on the divergence angle can be systematically studied by detecting the signal strength value output by the photodetector, so as to find the best collimation parameters of the to-be-tested collimator to achieve the best collimation effect.

[0060] Figure 1 The system structure schematic diagram of the fiber collimator collimation characteristic test of an embodiment of the present application is shown in FIG. 1. Figure 1 As shown in FIG. 1, a system applied to testing the collimation characteristics of a fiber collimator includes a laser 11, a polarization beam splitting module 12, a quarter-wave plate 14, a reflecting mirror, a photodetector 16, and a processor 17.

[0061] The outgoing light beam emitted by the laser 11 enters the first port a of the polarization beam splitting module 12 as an incident light beam, and the P-polarized light of the incident light beam is transmitted by the polarization beam splitting module 12 and output through the second port b to the collimation incident end d of the to-be-tested collimator 13.

[0062] In the present embodiment, in addition to the first port a and the second port b, the polarization beam splitting module 12 also has at least a third port c, which can realize the following functions: the P-polarized light in the incident light beam entering the polarization beam splitting module 12 enters from the first port a and exits from the second port b, or enters from the second port b and exits from the first port a; the S-polarized light entering the polarization beam splitting module 12 enters from the second port b and exits from the third port c.

[0063] In another embodiment, the polarization splitting module 12 described above can also be provided with a fourth port (not shown in the figure), at this time the S-polarized light enters from the first port a and exits from the fourth port, so that the polarization splitting module 12 has a completely symmetrical structure. That is, whether the incident light beam enters from the first port a or the second port b, the P-polarized light will penetrate and exit from the other end; and the S-polarized light will exit from the third port c or the fourth port, that is, the polarization splitting module 12 has the function of separating the light beam into P-polarized light and S-polarized light.

[0064] Exemplarily, Figure 2 The structural schematic diagram of the polarization splitting module 12 of an embodiment of the present application is shown in Figure 2 As shown, the polarization splitting module 12 only adopts a structure with three ports, and the polarization splitting module 12 includes a half-wave plate 121 and a polarization splitting prism 122, wherein the half-wave plate 121 is used to change the polarization state of the light entering from the first port a, and the polarization splitting prism 122 is used to transmit the P-polarized light in the incident light beam and output from the second port b, at this time the S-polarized light input from the first port a and reflected by the polarization splitting prism 122 does not have a corresponding output port (if necessary, the fourth port of the above embodiment can also be provided); if the reflected light beam (to be described later) enters from the second port b, the polarization splitting prism 122 is also used to reflect the S-polarized light input from the second port b and output from the third port c.

[0065] In the polarization splitting module 12 shown in Figure 2 The position of the half-wave plate 121 should be rotated as much as possible to maximize the power of the light signal output from the second port b.

[0066] Continuing to refer to Figure 1 , the second port b of the polarization splitting module 12 is provided with a first fiber flange, and the collimating incident end d of the to-be-tested collimator 13 is provided with a second fiber flange, wherein the first fiber flange and the second fiber flange are connected through an optical fiber, so that the first fiber flange can couple the S-polarized light output from the second port into the optical fiber for transmission, thereby reducing the transmission loss.

[0067] The collimating incident end d of the to-be-tested collimator 13 receives the S-polarized light and collimates it, and the collimated light beam is emitted to the quarter-wave plate 14 through the collimating exit end of the to-be-tested collimator 13, and the light beam changes the polarization state through the quarter-wave plate 14 and reaches the mirror 15. In this embodiment, the mirror 15 can receive as much as possible all the light beams output forwardly from the to-be-tested collimator 13, so that the light beams that can be reflected back to the to-be-tested collimator 13 are not reflected. From the observation angle, the light spot collimated by the to-be-tested collimator 13 should be fully present on the mirror 15.

[0068] In the prior art, a special device is usually arranged at the position of the mirror 15 to collect the light spot irradiated by the collimated light beam, and the divergence angle size of the collimator 13 to be measured is determined by analyzing the size of the light spot. In order to solve the problem that the light spot is too large to be effectively measured, the mirror 15 is arranged in the present application to reflect the light beam back to form a reflected light beam, and the polarization state of the reflected light beam is changed again by the quarter-wave plate 14 and sent to the collimated exit end of the collimator 13 to be measured. Since the P-polarized light passes through the quarter-wave plate 14 twice, the total phase generated between the two perpendicular polarization components is π, which makes the polarization direction of the P-polarized light rotate 90°, so the P-polarized light is changed into S-polarized light which is perpendicular to the original P-polarized light.

[0069] It should be noted that the better the collimation performance of the collimator 13 to be measured (the smaller the divergence angle), the more light beams can be reflected back to the collimated exit end, and vice versa. In order to improve the sensitivity of the reflected light beam, the intensity of the reflected light signal can be improved by adjusting the rotation angle of the quarter-wave plate 14, and at this time the quarter-wave plate 14 has the function of adjusting the intensity of the light signal.

[0070] After the collimated exit end of the collimator 13 to be measured receives the returned S-polarized light, it converges the S-polarized light through the internal lens 131 and transmits it to the second port of the polarization beam splitting module 12 through the collimated entrance end d. Since the collimated entrance end d is provided with a second fiber flange, the collimator 13 to be measured can couple the returned S-polarized light into the optical fiber for transmission, thereby reducing the transmission loss.

[0071] After the second port b of the polarization beam splitting module 12 receives the S-polarized light, it is emitted from the third port c. As shown in Figure 1 and Figure 2 The S-polarized light entering the polarization beam splitting module 12 is reflected by the polarization beam splitting prism 122 and sent to the photodetector 16 through the third port c.

[0072] The photodetector 16 outputs a corresponding signal intensity value after receiving the light signal, which can be a voltage value, and the size of which can reflect the intensity of the received light signal.

[0073] In some embodiments, the photodetector can be externally connected to an oscilloscope or a signal intensity display device, so that the management personnel can adjust the collimation parameters by observing the trend of the signal intensity value.

[0074] Please continue to refer to Figure 1The laser 11 and the polarization beam splitting module 12, the polarization beam splitting module 12 and the to-be-measured collimator 13 are connected through optical fibers. In addition, when the polarization beam splitting module 12 is far away from the remote to-be-measured collimator 13, the optical fiber flange is arranged at the second port b of the polarization beam splitting module 12 and the collimating incident end d of the to-be-measured collimator 13 for coupling transmission, which is beneficial to detecting the divergence angle of the remote to-be-measured collimator at the end of the polarization beam splitting module. If the polarization beam splitting module 12 is close to the remote to-be-measured collimator 13, the optical fiber coupler can be arranged on the optical fiber without arranging the optical fiber flange.

[0075] The processor 17 is electrically connected with the photodetector 16, used for acquiring the signal intensity value output by the photodetector 16, and the processor 17 can determine the divergence angle of the to-be-measured collimator 13 corresponding to the signal intensity value output by the photodetector 16 according to the first mapping relationship measured in advance, wherein the first mapping relationship is a functional relationship between the signal intensity value output by the photodetector 16 and the divergence angle of the to-be-measured collimator.

[0076] In the above embodiment, by measuring a plurality of different signal intensity values and the real divergence angle of the to-be-measured collimator 13 corresponding to the signal intensity values, the functional relationship between the signal intensity value output by the photodetector 16 and the divergence angle, i.e. the first mapping relationship, can be fitted. Then in subsequent measurement, only the signal intensity value output by the photodetector 16 is needed to obtain the divergence angle of the to-be-measured collimator 13 by using the first mapping relationship. In addition, the small amount of real divergence angles required for fitting can be measured by the existing measurement method, such as directly measuring the divergence angle by using the beam quality analyzer, which can save the measurement workload compared with measuring the divergence angle of the to-be-measured collimator 13 each time.

[0077] In another embodiment, the half-wave plate 121, the polarization beam splitting prism 122, the to-be-measured collimator 13 and the quarter-wave plate 14 are coaxially arranged along the main optical axis of the laser 11, wherein the laser 11 is located at one end of the main optical axis, and the mirror 15 is located at the other end of the main optical axis and is perpendicular to the main optical axis. In addition, the photodetector 16 is arranged in the output direction of the third port c of the polarization beam splitting module 12.

[0078] In the above embodiment, the outgoing light beam of the laser 11 reaches the mirror 15 from the polarization beam splitting module 12, and the light path from the mirror 15 back to the polarization beam splitting module 12 is coincident. This can reduce the power loss caused by reflection or refraction of other components to a certain extent.

[0079] In another embodiment, the collimator 13 to be tested is provided with only one set of lenses 131. The set of lenses 131 can be a combination of multiple lenses 131 or a single lens 131. In this embodiment, adjusting the position of the set of lenses 131 must be done as a whole. This is beneficial for analyzing the influence of the position of the lens 131 on the size of the divergence angle of the collimator 13 to be tested.

[0080] In the above embodiments, the smaller the divergence angle, the better the collimation performance of the collimator 13 under test, the stronger the light signal received by the photodetector 16, and the greater the output signal strength value. Therefore, the processor 17 can adjust the position of the lens 131 on the principal optical axis according to the signal strength value output by the photodetector 16 (for example, using the relative position between the lens 131 and the collimation output end as the collimation parameter). When the output signal strength value is small, the signal strength value can be adjusted by adjusting the position of the lens 131, thereby adjusting the size of the divergence angle.

[0081] In another embodiment, Figure 3 This is a schematic diagram of a system structure for testing the collimation characteristics of an optical fiber collimator according to another embodiment of this application. Figure 3 As shown, in this embodiment... Figure 1 Based on the embodiment shown, at least one optical isolator 18 is added. One of the optical isolators 18 is located on the main optical axis between the laser 11 and the polarization beam splitter 12 to isolate the reflected laser beam, thereby preventing the reflected light from interfering with the stability of the laser 11 or the optical path.

[0082] Figure 4 This is a flowchart illustrating a method for testing the collimation characteristics of an optical fiber collimator according to an embodiment of this application. Figure 4 As shown, this embodiment provides a method for testing the collimation characteristics of an optical fiber collimator. Applied to any of the collimation characteristic testing systems described in the above embodiments, the method includes the following steps:

[0083] S401: Determine the second mapping relationship between the signal strength value output by the photodetector and the collimation parameter.

[0084] In this embodiment, the collimation parameters are internal structural parameters that affect the size of the divergence angle of the collimator 13 under test, such as the lens focal length, lens position, and lens material. Adjusting the collimation parameters can change the size of the divergence angle of the collimator.

[0085] To determine the second mapping relationship, different collimation parameter values ​​can be adjusted, and then the signal strength value output by photodetector 16 can be measured.

[0086] Assuming that there are two collimation parameters, lens position x and lens focal length y, where the lens position x can select the distance between the lens 131 and the collimation output end, and the signal intensity value output by the photodetector 16 is z, then by measuring a plurality of groups of three-tuples about the lens position, the lens focal length, and the signal intensity value, the second mapping relationship between the lens position x, the lens focal length y, and the signal intensity value z can be established by fitting:

[0087]

[0088] wherein, is an operation rule about the mapping of the lens position x, the lens focal length y, to the signal intensity value z.

[0089] For the case of having more numbers of collimation parameters, the second mapping relationship can be fitted by using the same method.

[0090] S402: Determine the third mapping relationship between the collimation parameters and the divergence angle of the collimator to be measured.

[0091] In this embodiment, assuming that the real divergence angle size measured by the collimator to be measured 13 is Similarly, by measuring a plurality of groups of three-tuples about the lens position, the lens focal length, and the real divergence angle size, the second mapping relationship between the lens position x, the lens focal length y, and the real divergence angle size can be established:

[0092]

[0093] wherein, is an operation rule about the mapping of the lens position x, the lens focal length y, to the real divergence angle size .

[0094] It should be noted that measuring the real divergence angle size of the collimator to be measured 13 only needs to sample a small amount of measurement of the real divergence angle size when determining different lens focal lengths and lens positions.

[0095] For example: when 50 different lens focal length and lens position parameters are selected, 50 corresponding signal intensity values are obtained, but at the same time of measuring the signal intensity value, a small part of the real divergence angle size can be measured when the lens focal length and lens position parameters are determined.

[0096] S403: Determine the first mapping relationship according to the second mapping relationship and the third mapping relationship.

[0097] In this embodiment, after the second mapping relationship and the third mapping relationship are determined, the first mapping relationship between the divergence angle size and the signal intensity value z can be established:

[0098]

[0099] wherein, is the operation rule about mapping signal intensity value z to real divergence angle size .

[0100] That is to say, in the case of determining a set of collimation parameters, the divergence angle size and the signal intensity value are one-to-one corresponding, then in the subsequent detection of the divergence angle size of the to-be-tested collimator 13, only the signal intensity value output by the photodetector 16 is needed to be acquired, and the divergence angle size of the to-be-tested collimator 13 at this time can be calculated according to the first mapping relationship.

[0101] Figure 5 The flow chart of the method for testing the collimation characteristics of the fiber collimator according to another embodiment of the present application is shown. In the embodiment, the collimation parameter is the relative position of the lens 131 and the collimation exit end. In order to simplify the number of collimation parameters, the embodiment only considers the position of the lens 131 in the to-be-tested collimator 13, and specifically, the relative position between the lens 131 and the collimation exit end of the to-be-tested collimator 13 is taken as the only collimation parameter.

[0102] As Figure 5 shown, the method for testing the collimation characteristics of the fiber collimator according to the embodiment comprises the following steps:

[0103] S501: Adjust the relative position of the lens and the collimation exit end for several times, and acquire the signal intensity value output by the photodetector after adjusting the relative position of the lens and the collimation exit end each time.

[0104] In the embodiment, the to-be-tested collimator 13 has a corresponding divergence angle size and the photodetector 16 outputs a corresponding signal intensity value each time the relative position of the lens 131 and the collimation exit end is adjusted.

[0105] Exemplarily, the following shows how to adjust the relative position of the lens 131 and the collimation exit end and acquire the signal intensity value:

[0106] Firstly, the lens 131 is controlled to move along the main optical axis at a fixed step length within a reasonable moving range, so as to adjust the interval distance between the lens 131 and the collimation exit end at equal intervals, and then record the signal intensity value output by the photodetector 16 at different interval distances. In the embodiment, the fixed step length can be 0.02-0.1 mm.

[0107] It should be noted that since the fixed step length of the lens 131 moving along the main optical axis is small, the lens 131 needs to be measured by a special device at different positions. In order to improve the convenience of adjusting the interval distance, the lens 131 can be arranged on a track that can be accurately moved, and the lens 131 is moved on the track by a motor. In some embodiments, the motor of the track can also be controlled by the processor 17. At this time, the different interval distances that the lens 131 needs to move can be controlled by the processor.

[0108] In addition, after the relative position between the lens 131 and the collimating exit end is determined, the relative position between the lens 131 and the collimating entrance end d is also determined, so the two belong to equivalent collimating parameters. In specific implementation, appropriate collimating parameters can be selected according to the convenience of adjustment.

[0109] S502: fitting the signal strength values, and determining the second mapping relationship between the signal strength values and the collimating parameters according to the fitting result.

[0110] After a plurality of sets of collimating parameters and signal strength values are measured according to step S501, a second mapping relationship between the signal strength values and the collimating parameters can be determined by polynomial fitting: , is the operation rule of mapping the lens position x to the signal strength value z. The specific steps can refer to the description of step S401, which will not be repeated here.

[0111] S503: selecting part of the interval distances, and measuring the real divergence angle of the to-be-measured collimator 13 corresponding to the interval distances.

[0112] In the embodiment, in order to reduce the workload of measurement, part of the interval distances used in step S501 can be selected to measure the real divergence angle of the to-be-measured collimator 13.

[0113] Exemplarily, the real divergence angle of the to-be-measured collimator 13 is measured by the beam quality analyzer every five times of adjusting the interval distance.

[0114] More preferably, the number of measurements of the divergence angle can be increased in the interval where the signal strength value is large, and the number of measurements of the divergence angle can be reduced in the interval where the signal strength value is small. This is conducive to improving the fitting accuracy near the minimum value of the divergence angle.

[0115] S504: fitting the real divergence angles, and determining the third mapping relationship between the interval distances and the divergence angle of the to-be-measured collimator according to the fitting result.

[0116] Based on the collimation parameters and the true divergence angle measured in step S503, the third mapping relationship between the interval distance and the divergence angle can also be determined by polynomial fitting: , It concerns the size of the lens position x mapped to the true divergence angle. The rules of operation.

[0117] Figure 6 for Figure 5 The graph showing the functional relationship between the interval distance and the divergence angle in the embodiment. Figure 6 As shown, the lens 131 has a good spacing distance, which allows the collimator 13 under test to have a better divergence angle.

[0118] It should be noted that although the above embodiment uses only the distance between lens 131 and collimating output end as the only collimation parameter, the detection process can still refer to the steps of the above embodiment when other collimation parameters are selected, and will not be repeated here.

[0119] S505: Determine the first mapping relationship based on the second and third mapping relationships.

[0120] In this embodiment, according to the second mapping relationship and the third mapping relationship The first mapping relationship can be determined, namely the functional relationship between the signal strength value and the divergence angle: .

[0121] in, It concerns the mapping of the signal strength value z to the actual divergence angle. The rules of operation.

[0122] Figure 7 for Figure 5 The example shows the functional relationship between signal strength and divergence angle. Figure 7 As shown, it can be seen that the greater the signal strength value output by the photodetector 16, the smaller the divergence angle of the collimator 13 under test, which is consistent with the theoretical derivation results.

[0123] After establishing the first mapping relationship through steps S501~S505, the divergence angle of the collimator 13 under test can be calculated based on any signal strength value output by the photodetector 16.

[0124] Figure 8 This is a flowchart illustrating a method for testing the collimation characteristics of an optical fiber collimator according to another embodiment of this application. Figure 8 As shown in the figure, this embodiment provides a method for testing the collimation characteristics of an optical fiber collimator, which includes the following steps:

[0125] S801: determining a second mapping relationship between the signal intensity value output by the photodetector and the collimation parameter.

[0126] S802: determining a third mapping relationship between the collimation parameter and the divergence angle of the collimator under test.

[0127] S803: determining the first mapping relationship according to the second mapping relationship and the third mapping relationship.

[0128] In this embodiment, the specific content of S801-S803 can refer to the description of S401-S403 in the embodiment shown in Figure 4 or the description of S501-S505 in the embodiment shown in Figure 5 This will not be described here.

[0129] In the foregoing steps of this embodiment, the collimation parameter corresponding to the optimal divergence angle can be determined according to the third mapping relationship, and then the collimator under test 13 is set according to the collimation parameter.

[0130] However, in some cases, the divergence angle of the collimator under test is not only the optimal value, but also only needs to meet the given target divergence angle requirement. For example, a target divergence angle threshold is set, and as long as the divergence angle of the collimator under test 13 is less than the target divergence angle threshold, it is considered that the collimation performance of the collimator under test 13 meets the requirement. Since the divergence angle detection of the collimator under test 13 is relatively troublesome, the embodiment determines whether the collimator under test 13 meets the target divergence angle requirement by the following method.

[0131] S804: determining a target signal value range of the photodetector output when the divergence angle of the collimator under test meets the target divergence angle requirement according to the first mapping relationship.

[0132] Since the first mapping relationship can reflect the relationship between the divergence angle of the collimator under test 13 and the signal intensity value output by the photodetector 16, because only the target signal value range corresponding to the target divergence angle requirement needs to be found according to the first mapping relationship. In this way, as long as the signal intensity value output by the photodetector 16 is in the target signal value range, it can be considered that the divergence angle of the collimator under test 13 meets the target divergence angle requirement.

[0133] S805: determining a target parameter range of the collimation parameter corresponding to the target signal value range according to the second mapping relationship.

[0134] If the signal intensity value output by the photodetector 16 is not directly displayed, then the processor 17 can also determine the target parameter range of the collimation parameter according to the target signal value range obtained in step S804 and the second mapping relationship.

[0135] If the collimation parameter is the relative position (interval distance) between the lens 131 and the collimation exit end, the processor 17 can determine the target interval distance range between the lens 131 and the collimation exit end according to the target signal value range obtained in step S804 and the second mapping relationship, i.e. the installation position range that the lens 131 can select when the divergence angle of the to-be-tested collimator 13 meets the target divergence angle requirement.

[0136] The collimation characteristic testing method provided by the above embodiment, if the target is to make the divergence angle of the to-be-tested collimator 13 meet the target divergence angle requirement, the processor 17 can obtain the target signal value range that the photodetector 16 needs to output and the target parameter range (such as the target interval distance range between the lens 131 and the collimation exit end) that the collimation parameter needs to set according to the target divergence angle requirement and the first mapping relationship and the second mapping relationship established in advance without directly measuring the divergence angle.

[0137] It should be noted that the above steps provide a method for testing the collimation characteristics of a fiber collimator, and the implementation principle and technical effects are the same as those of the above system embodiments. For brevity, the part of the embodiment of the collimation characteristic testing method not mentioned can be referred to the corresponding content in the above system embodiment of the collimation characteristic testing method.

[0138] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A method applied to a system for testing collimation properties of a fiber collimator, characterized in that, The test system comprises a laser (11), a polarization beam splitting module (12), a quarter-wave plate (14), a mirror (15), a photodetector (16) and a processor (17); The outgoing beam of the laser (11) enters a first port of the polarization beam splitting module (12), the polarization beam splitting module (12) transmits P-polarized light of the outgoing beam and sends it to a collimating incident end of a collimator to be tested (13) through a second port; The collimator to be tested (13) collimates the P-polarized light and outputs a collimated beam through a collimated outgoing end, the collimated beam reaches the mirror (15) after passing through the quarter-wave plate (14), the reflected beam after being reflected by the mirror (15) passes through the quarter-wave plate (14) again to form S-polarized light which is sent to the collimated outgoing end of the collimator to be tested (13); a set of lenses (131) are arranged in the collimator to be tested (13); The collimator to be tested (13) converges the S-polarized light and sends it to the second port of the polarization beam splitting module (12) through the collimating incident end; The polarization beam splitting module (12) reflects the S-polarized light and sends it to the photodetector (16) through a third port; The processor (17) is electrically connected to the photodetector (16); The method comprises: determining a second mapping relationship between the signal intensity value output by the photodetector and a collimation parameter, the collimation parameter being at least one structural parameter in the collimator to be tested which affects the size of the divergence angle; determining a third mapping relationship between the collimation parameter and the divergence angle of the collimator to be tested; determining a first mapping relationship according to the second mapping relationship and the third mapping relationship; The collimation parameter is the relative position of a set of lenses arranged in the collimator to be tested and the collimated outgoing end; Correspondingly, the step of determining the second mapping relationship between the signal intensity value output by the photodetector and the collimation parameter comprises: adjusting the relative position of the lenses and the collimated outgoing end several times, and obtaining the signal intensity value output by the photodetector after adjusting the relative position of the lenses and the collimated outgoing end each time; fitting the signal intensity values several times, and determining the second mapping relationship between the signal intensity value and the collimation parameter according to the fitting result.

2. The method of claim 1, wherein, The step of obtaining the signal intensity value output by the photodetector after adjusting the relative position of the lenses and the collimated outgoing end each time comprises: controlling the lenses to move along the main optical axis of the laser at a fixed step length, and adjusting the interval distance between the lenses and the collimated outgoing end at equal intervals; recording the signal intensity value output by the photodetector at different interval distances.

3. The method of claim 2, wherein, The step of determining the third mapping relationship between the collimation parameter and the divergence angle of the collimator to be tested comprises: selecting part of the interval distances, and measuring the real divergence angle corresponding to the collimator to be tested; According to the measured real divergence angles of the to-be-tested collimator at a plurality of interval distances, a plurality of the real divergence angles are fitted, and a third mapping relationship between the interval distances and the divergence angle of the to-be-tested collimator is determined according to a fitting result.

4. A system for testing the collimation properties of a fiber collimator, characterized by, The test system is applied to the method of any one of claims 1-3, the processor (17) is configured to acquire a signal intensity value output by the photodetector (16), and determine a size of the divergence angle of the to-be-tested collimator (13) corresponding to the signal intensity value according to a first mapping relationship measured in advance; the first mapping relationship is a functional relationship between the signal intensity value output by the photodetector (16) and the size of the divergence angle of the to-be-tested collimator (13).

5. The system of claim 4, wherein, The polarization splitting module (12) comprises: a half-wave plate (121) configured to change a polarization state of an outgoing light beam input from the first port; a polarization splitting prism (122) configured to transmit P-polarized light in the outgoing light beam and output from the second port, and reflect S-polarized light input from the second port and output from the third port.

6. The system of claim 5, wherein, The second port is provided with a first fiber flange, and a collimating incident end of the to-be-tested collimator (13) is provided with a second fiber flange, and the first fiber flange and the second fiber flange are connected by an optical fiber.

7. The system of claim 5, wherein, The half-wave plate (121), the polarization splitting prism (122), the to-be-tested collimator (13), and the quarter-wave plate (14) are coaxially arranged along a main optical axis of the laser (11), and the mirror (15) is perpendicular to the main optical axis.

8. The system of claim 4, wherein, The processor (17) is further configured to adjust a relative position between the lens (131) and the collimating incident end according to the signal intensity value output by the photodetector (16), so as to adjust the size of the divergence angle of the to-be-tested collimator (13).

9. The system of claim 4, wherein, Further comprising: an optical isolator (18) located between the laser (11) and the polarization splitting module (12), configured to isolate the reflected laser beam.

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