Optical fiber coupling system based on adaptive optics and calibration method thereof

Abstract

The invention provides an optical fiber coupling system based on adaptive optics. The optical fiber coupling system comprises a tilting mirror, a deformable mirror, a spectroscope, a reflector, an optical fiber coupling module and a Hartmann module. The optical fiber coupling module comprises a coupling lens, an electric translation stage, and a camera and an optical fiber coupler which are vertically arranged on the electric translation stage; and the Hartmann module comprises a beam shrinking mirror front group, a beam shrinking mirror rear group, a micro lens and a Hartmann camera. According to the method, the state of correcting the wavefront aberration of the optical fiber coupling lens by the wavefront corrector is judged based on the spot size, so that calibration is carried out, then the system is corrected on the basis of the calibration value, the optical fiber coupling efficiency is improved, and the problem that the wavefront corrector cannot correct the aberration of the optical fiber coupling lens is solved; the aberration of the optical fiber coupling lens is effectively calibrated and corrected, the optical fiber coupling efficiency is improved, and the overall performance of a wireless optical communication system is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber coupling, and in particular to a calibration method for an optical fiber coupling system based on adaptive optics. Background Art

[0002] As the core technology in the field of modern information transmission, optical fiber communication has been widely used in the fields of communication, network and sensing. The existence of wavefront aberration will directly affect the imaging quality, and poor imaging quality means that the wavefront shape of the light beam has a large distortion or distortion, which leads to reduced fiber coupling. With the rapid development of information technology, improving the fiber coupling efficiency and enhancing the overall performance of optical fiber communication has become an important issue that needs to be solved urgently.

[0003] Nowadays, adaptive optics technology is the most effective way to solve wavefront aberrations. Therefore, adaptive optics technology is introduced in fiber coupling systems to improve fiber coupling efficiency. However, the fiber coupling systems currently using adaptive optics technology do not correct the aberrations of the coupling lenses, resulting in insufficient fiber coupling efficiency. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a fiber coupling system based on adaptive optics and a calibration method thereof, so as to solve the technical problem that the fiber coupling system using adaptive optics technology in the prior art does not correct the aberration of the coupling lens, resulting in insufficient fiber coupling efficiency.

[0005] The present invention provides a fiber coupling system based on adaptive optics, comprising:

[0006] Tilting mirrors, deformable mirrors, beam splitters, reflectors, fiber-coupled modules and Hartmann modules;

[0007] The optical fiber coupling module includes a coupling lens, an electric translation stage, and a camera and an optical fiber coupler vertically arranged on the electric translation stage;

[0008] The Hartmann module comprises a front group of a beam reducer, a rear group of a beam reducer, a microlens and a Hartmann camera.

[0009] The present invention also provides a calibration method using a fiber coupling system based on adaptive optics, comprising:

[0010] S1, start the electric translation to move it up and down, and ensure that the camera moves to replace the position of the optical fiber coupler;

[0011] S2, turn on the collimator, so that the parallel light beam emitted by the collimator enters the fiber coupling system;

[0012] S3, the parallel light beam passes through the tilt mirror, the deformable mirror, and is divided into two parts through the beam splitter in sequence, one part of the parallel light beam is converged at the focus through the coupling lens, so that the camera can receive the light spot converged by the coupling lens at the focus, and the other part of the parallel light beam passes through the reflecting mirror, the front group of the beam reducer, the rear group of the beam reducer and the microlens in sequence, and is emitted into the Hartmann camera;

[0013] S4, using a gradient algorithm to adjust the electric translation stage so that the spot area on the target surface of the camera is within 1.5 times of the Airy spot, and moving the fiber coupler to the focus;

[0014] S5, recording the data of the Harmant camera, calculating the slope value of each aperture in the Harmant camera, and using the slope value as a calibration value;

[0015] S6, judging whether the optical fiber coupling efficiency of the optical fiber coupling module meets the requirement, if not, keeping the parameters of the tilt mirror and the deformable mirror unchanged, and re-performing steps S1-S3 to find the focus;

[0016] S7. Re-adjust the parameters of the tilt mirror and the deformable mirror based on the calibration value, and execute steps S4-S6 until the fiber coupling efficiency meets the requirements.

[0017] Optionally, the step of adjusting the electric translation stage by using a gradient algorithm comprises:

[0018] The gradient algorithm is expressed as:

[0019] U i+1 =U i -α×▽ U J(U;P j )

[0020] Among them, U i is the drive voltage value of the electric translation stage, U i+1 is the updated driver voltage value, ▽ U J(U;P j ) is the evaluation function, J is the value of U at the current optical power measurement value P j The gradient estimate under .

[0021] Optionally, the Airy spot comprises:

[0022] The calculation formula is expressed as:

[0023]

[0024] where r Airy is the radius of the Airy spot, λ is the wavelength, N A is the numerical aperture of the optical fiber.

[0025] Optionally, calculating the slope value of each sub-aperture in the Harmant camera includes:

[0026] The calculation of the subaperture slope is expressed as:

[0027]

[0028] Where (x cj ,y cj ) is the coordinate of the centroid of the jth subaperture, I i is the light intensity of the i-th pixel; (x j ,y j ) is the coordinate of the i-th pixel; λ is the wavelength of the incident light beam; f is the focal length of the microlens array; S j is the area of ​​the jth subaperture; W(x,y) is the wavefront phase; G x x, G yj are the average slopes of the wavefront phase of the incident light at the jth sub-aperture in the x and y directions, respectively.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The present invention determines the state of the wavefront corrector correcting the wavefront aberration of the fiber coupling lens based on the spot size, thereby performing calibration. Afterwards, the system is calibrated again on the basis of the calibration value, thereby improving the fiber coupling efficiency and solving the problem that the wavefront corrector cannot correct the aberration of the fiber coupling lens. The fiber coupling lens aberration is effectively calibrated and corrected, thereby improving the fiber coupling efficiency and enhancing the overall performance of the wireless optical communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 It is a structural schematic diagram of the system in the present invention;

[0034] Figure 2 Schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other implementation cases obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The functional units with the same labels in the examples of the present invention have the same and similar structures and functions.

[0036] See also Figure 1 The present invention provides a fiber coupling system based on adaptive optics, comprising:

[0037] Tilting mirrors, deformable mirrors, beam splitters, reflectors, fiber-coupled modules and Hartmann modules;

[0038] The optical fiber coupling module includes a coupling lens, an electric translation stage, and a camera and an optical fiber coupler vertically arranged on the electric translation stage;

[0039] The Hartmann module comprises a front group of a beam reducer, a rear group of a beam reducer, a microlens and a Hartmann camera.

[0040] See also Figure 2 The present invention also provides a calibration method using a fiber coupling system based on adaptive optics, comprising:

[0041] S1, start the electric translation to move it up and down, and ensure that the camera moves to replace the position of the optical fiber coupler;

[0042] S2, turn on the collimator, so that the parallel light beam emitted by the collimator enters the fiber coupling system;

[0043] S3, the parallel light beam passes through the tilt mirror, the deformable mirror, and is divided into two parts through the beam splitter in sequence, one part of the parallel light beam is converged at the focus through the coupling lens, so that the camera can receive the light spot converged by the coupling lens at the focus, and the other part of the parallel light beam passes through the reflecting mirror, the front group of the beam reducer, the rear group of the beam reducer and the microlens in sequence, and is emitted into the Hartmann camera;

[0044] S4, using a gradient algorithm to adjust the electric translation stage so that the spot area on the target surface of the camera is within 1.5 times of the Airy spot, and moving the fiber coupler to the focus;

[0045] S5, recording the data of the Harmant camera, calculating the slope value of each sub-aperture in the Harmant camera, and using the slope value as a calibration value;

[0046] S6, judging whether the optical fiber coupling efficiency of the optical fiber coupling module meets the requirement, if not, keeping the parameters of the tilt mirror and the deformable mirror unchanged, and re-performing steps S1-S3 to find the focus;

[0047] S7. Re-adjust the parameters of the tilt mirror and the deformable mirror based on the calibration value, and execute steps S4-S6 until the fiber coupling efficiency meets the requirements.

[0048] In this embodiment, S1, start the electric translation to move it up and down, ensuring that the camera moves to replace the position of the optical fiber coupler.

[0049] In actual use, the fiber optic coupler and the camera are placed on an electric translation stage. The relative position of the fiber optic coupler and the camera can be calibrated by the number of turns n of the electric translation stage knob. The electric translation stage knob is rotated n times to move the electric translation stage, so that the camera moves downward to replace the position of the fiber optic coupler and can receive the output light spot.

[0050] S2. Turn on the collimator to allow the parallel light beam emitted by the collimator to enter the fiber coupling system.

[0051] S3. The parallel light beam passes through the tilt mirror, the deformable mirror and is divided into two parts through the beam splitter in sequence. One part of the parallel light beam is converged at the focus through the coupling lens, so that the camera can receive the light spot converged by the coupling lens at the focus. The other part of the parallel light beam passes through the reflector, the front group of the beam reducer, the rear group of the beam reducer and the microlens in sequence and is emitted into the Hartmann camera.

[0052] The beam splitter divides the parallel light beam into two parts, one part enters the fiber coupling module, and the other part enters the Hartmann module after being reflected by a reflector.

[0053] The coupling lens converges parallel light at the focal point. The fiber coupler and the camera are placed on an electric translation stage and can be interchanged at the focal point to ensure that both the fiber coupler and the camera can receive the light spot converged by the coupling lens at the focal point. The relative position of the fiber and the camera can be calibrated by the number of turns n of the electric translation stage knob. By rotating the electric translation stage knob n times, the electric translation stage moves, so that the camera replaces the position of the fiber coupler, and the fiber coupling system is calibrated.

[0054] S4. Use a gradient algorithm to adjust the electric translation stage so that the spot area on the target surface of the camera is within 1.5 times of the Airy spot, and move the fiber coupler to the focus.

[0055] This step starts the fiber coupling based on adaptive optics. The camera is switched to the focus, and the electric translation stage is adjusted using the random gradient algorithm so that the spot area on the camera target surface is within 1.5 times the Airy spot. The Airy spot size can be calculated according to the following formula:

[0056]

[0057] where r Airy is the radius of the Airy spot, λ is the wavelength, N A is the numerical aperture of the optical fiber. At this point, the correction requirements of the optical fiber coupling system have been met. Switch the optical fiber coupler of the optical fiber coupling system to the focal position.

[0058] At this time, in order to meet the calibration requirements of the fiber coupling system, the fiber coupler is switched to the focal point.

[0059] S5. Record the data of the Harmant camera, calculate the slope value of each sub-aperture in the Harmant camera, and use the slope value as a calibration value.

[0060] The data of the Hartmann camera and the fiber coupling rate of the fiber coupling system are collected. Based on this data, the aberration of the main optical path of the system is corrected by using the tilt mirror and deformable mirror. After the aberration of the fiber coupling lens is corrected by using the translation stage, the surfaces of the tilt mirror and deformable mirror have certain fluctuations. This fluctuation can be converted into a slope value, and the slope value of each sub-aperture of each Hartmann system is recorded, which is the calibration value. After that, the system calibration is based on the calibration value.

[0061] At this time, it is determined whether the required optical fiber coupling efficiency is achieved. If not, the parameters of the tilt mirror and the deformable mirror are kept unchanged, and steps S1-S3 are re-executed to find the focus.

[0062] S7. Re-adjust the parameters of the tilt mirror and the deformable mirror based on the calibration value, and execute steps S4-S6 until the fiber coupling efficiency meets the requirements.

[0063] Then switch the fiber coupling system to a camera, find the focus position, and repeat the above process until the requirement is met.

[0064] The present invention determines the state of the wavefront corrector correcting the wavefront aberration of the fiber coupling lens based on the spot size, thereby performing calibration. Afterwards, the system is calibrated again on the basis of the calibration value, thereby improving the fiber coupling efficiency and solving the problem that the wavefront corrector cannot correct the aberration of the fiber coupling lens. The fiber coupling lens aberration is effectively calibrated and corrected, thereby improving the fiber coupling efficiency and enhancing the overall performance of the wireless optical communication system.

[0065] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0066] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A fiber coupling system based on adaptive optics, characterized in that: include: Tilting mirrors, deformable mirrors, beam splitters, reflectors, fiber-coupled modules and Hartmann modules; The optical fiber coupling module includes a coupling lens, an electric translation stage, and a camera and an optical fiber coupler vertically arranged on the electric translation stage; The Hartmann module comprises a front group of a beam reducer, a rear group of a beam reducer, a microlens and a Hartmann camera.

2. The calibration method of the fiber coupling system based on adaptive optics as claimed in claim 1, characterized in that: include: S1, start the electric translation to move it up and down, and ensure that the camera moves to replace the position of the optical fiber coupler; S2, turn on the collimator, so that the parallel light beam emitted by the collimator enters the fiber coupling system; S3, the parallel light beam passes through the tilt mirror, the deformable mirror, and is divided into two parts through the beam splitter in sequence, one part of the parallel light beam is converged at the focus through the coupling lens, so that the camera can receive the light spot converged by the coupling lens at the focus, and the other part of the parallel light beam passes through the reflecting mirror, the front group of the beam reducer, the rear group of the beam reducer and the microlens in sequence, and is emitted into the Hartmann camera; S4, using a gradient algorithm to adjust the electric translation stage so that the spot area on the target surface of the camera is within 1.5 times of the Airy spot, and moving the fiber coupler to the focus; S5, recording the data of the Harmant camera, calculating the slope value of each sub-aperture in the Harmant camera, and using the slope value as a calibration value; S6, judging whether the optical fiber coupling efficiency of the optical fiber coupling module meets the requirement, if not, keeping the parameters of the tilt mirror and the deformable mirror unchanged, and re-performing steps S1-S3 to find the focus; S7. Re-adjust the parameters of the tilt mirror and the deformable mirror based on the calibration value, and execute steps S4-S6 until the fiber coupling efficiency meets the requirements.

3. The calibration method of the fiber coupling system based on adaptive optics according to claim 2, characterized in that: The method of using a gradient algorithm to adjust the electric translation stage comprises: The gradient algorithm is expressed as: Among them, U i is the drive voltage value of the electric translation stage, U i+1 is the updated driver voltage value, is the evaluation function, J is the value of U at the current optical power measurement value P j The gradient estimate under .

4. The calibration method of the fiber coupling system based on adaptive optics according to claim 2, characterized in that: The Airy spot comprises: The calculation formula is expressed as: where r Airy is the radius of the Airy spot, λ is the wavelength, N A is the numerical aperture of the optical fiber.

5. The calibration method of the fiber coupling system based on adaptive optics according to claim 2, characterized in that: The calculating the slope value of each sub-aperture in the Harmant camera includes: The calculation of the subaperture slope is expressed as: Where (x cj ,y cj ) is the coordinate of the centroid of the jth subaperture, I i is the light intensity of the i-th pixel; (x j ,y j ) is the coordinate of the i-th pixel; λ is the wavelength of the incident light beam; f is the focal length of the microlens array; S j is the area of ​​the jth subaperture; W(x,y) is the wavefront phase; G xj , G yj are the average slopes of the wavefront phase of the incident light at the jth sub-aperture in the x and y directions, respectively.

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