A self-stabilizing fiber coupling system based on MEMS and method thereof

Abstract

This invention provides a MEMS-based self-stabilizing fiber optic coupling system and method, which can achieve real-time closed-loop self-stabilization of coupling efficiency without manual intervention and has extremely strong environmental adaptability. The system includes a laser emitting unit, a MEMS mirror assembly, a beam splitter, a focusing coupling unit, a fiber optic beam splitter, a first detection unit, a second detection unit, and a control unit. The laser beam output from the laser emitting unit is deflected by the MEMS mirror assembly and then incident on the beam splitter. The beam output from the beam splitter is divided into two paths: one path is coupled into the fiber optic beam splitter via the focusing coupling unit, and the other path is projected onto the first detection unit. The fiber optic beam splitter output from the fiber optic beam splitter is incident on the second detection unit. The first detection unit uses a four-quadrant detector to output the detection spot position and total light intensity signal. The second detection unit outputs the input fiber power signal. The control unit is used to drive the deflection of the MEMS mirror assembly and adjust the laser current of the laser emitting unit.

Description

Technical Field

[0001] This invention relates to the field of laser and fiber coupling technology, specifically to a MEMS-based self-stabilizing fiber coupling system and method. Background Technology

[0002] In practical applications of laser fiber coupling, many products currently use a passive manual adjustment structure. This means that during production and debugging, the position of the focusing lens is manually changed through a multi-dimensional adjustment frame to achieve the best efficiency in laser coupling into the fiber. However, during the service life of the equipment, if it is affected by temperature fluctuations, mechanical vibrations, or structural creep, the optical path will shift and the coupling efficiency will drop significantly. In this case, it is necessary for professionals to open the equipment and readjust the focusing lens to restore the efficiency. Real-time compensation is not possible, resulting in extremely poor long-term stability and maintainability. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a MEMS-based self-stabilizing fiber optic coupling system and method, which can achieve real-time closed-loop self-stabilization of coupling efficiency without manual intervention and has extremely strong environmental adaptability.

[0004] The present invention adopts the following technical solution: a self-stabilizing fiber optic coupling system based on MEMS, comprising a laser emitting unit, a MEMS mirror assembly, a beam splitter, a focusing coupling unit, a fiber optic beam splitter, a first detection unit, a second detection unit, and a control unit; wherein, the laser emitting unit outputs a beam that is deflected by the MEMS mirror assembly and then incident on the beam splitter, the beam output by the beam splitter is divided into two paths, one path is coupled into the fiber optic beam splitter via the focusing coupling unit, and the other path is projected onto the first detection unit, and the fiber optic beam split from the fiber optic beam splitter is incident on the second detection unit; The first detection unit uses a four-quadrant detector to output the detection spot position and total light intensity signal; The second detection unit is used to output the fiber input power signal; The control unit is connected to the laser emitting unit, the MEMS mirror assembly, the first detection unit, and the second detection unit. It is used to drive the deflection of the MEMS mirror assembly and adjust the laser current of the laser emitting unit to achieve real-time automatic closed-loop coupling.

[0005] Furthermore, the laser emitting unit includes a laser, which is connected to a backlight detector. The control unit is connected to both the laser and the backlight detector to receive the operating laser power of the laser and the backlight power. Furthermore, the control unit has a multimodal control mode, which includes the following execution strategies: a. When the fiber input power is lower than the set threshold and the backlight power decreases proportionally, it is determined to be laser attenuation. In this case, the laser drive current is adjusted within a safe range to maintain the fiber input power. b. When the fiber input power is lower than the set threshold and the backlight power is stable, it is determined that there is an optical path offset or a change in coupling efficiency. Then, the MEMS reflector assembly is deflected to adjust the position of the detection spot. c. When the position of the detection spot remains unchanged and the input fiber power is still lower than the set threshold, it is determined that the output fiber end face is damaged or the focus is off-focus. The control unit triggers the MEMS mirror assembly to perform a micro-scan to search for the maximum input fiber power value. If the maximum input fiber power value is still lower than the set threshold, an early warning signal is output. If a maximum input fiber power value greater than the set threshold can be found, the current deflection position of the MEMS mirror assembly is recorded, and a prompt is made to check the output fiber end face. Furthermore, when the total light intensity signal output by the first detection unit is less than the preset noise threshold, it is determined to be a loss of lock. The control unit then executes the loss of lock recovery strategy, drives the MEMS mirror assembly according to the Archimedes spiral trajectory until the fiber input power is greater than the set threshold, and then switches back to the multi-mode control mode. Furthermore, a collimating lens and an optical isolator are sequentially arranged in the optical path between the laser emitting unit and the MEMS mirror assembly; the focusing coupling unit uses a focusing lens, the focused beam output by the focusing lens is coupled into the output optical fiber, the signal output by the output optical fiber is input to the optical fiber beam splitter, and the output optical fiber is fused to the optical fiber beam splitter; the reflectivity of the beam splitter is 2%~5%, and the splitting ratio of the optical fiber beam splitter is 1%~3%; the MEMS mirror assembly includes a first MEMS mirror and a second MEMS mirror, both of which are two-dimensional micro-deflection mirrors; the beam output by the optical isolator is sequentially incident on the first MEMS mirror and the second MEMS mirror, and the first MEMS mirror and the second MEMS mirror are arranged parallel to each other; A self-stabilizing fiber coupling method based on MEMS includes: Acquire the optical signal in the detection optical path and the position of the detection spot in the detection optical path where the laser beam is located; Based on the optical signal and the position of the detected light spot, it is determined whether the lock-out condition is met. If it is met, the lock-out recovery strategy is executed. If it is not met, the corresponding execution strategy in the multi-modal control mode is mapped and executed, thereby realizing real-time automatic closed-loop coupling.

[0006] Furthermore, when executing strategy b, the following steps are included: S1. Determine the initial position of the detection spot in the detection optical path where the laser beam is located; S2. Real-time detection of the real-time position of the detection spot, obtaining the offset of the detection spot based on the real-time position and the initial position, and obtaining the angle correction amount based on the offset; S3. Adjust the position of the detection spot based on the angle correction amount; S4. Repeat step S2 until the offset is zero, thereby achieving real-time automatic stable coupling. Further, in step S2, obtaining the offset of the detection spot includes: The position deviation is obtained based on the real-time position and the initial position: Δx=x0-x mems Δy=y0-y mems ; The offset is constructed based on the positional deviation: Δp=[Δx,Δy] T ; Where x0 and y0 are the real-time position coordinates of the detected light spot; x mems y mems To determine the initial maximum power position coordinates for detecting the light spot; Further, in step S2, obtaining the angle correction amount based on the offset includes: Pre-stored pseudo-inverse matrix J + =J T (JJ T ) -1 ; The required angle correction is obtained from the pseudo-inverse matrix: Δθ = J + ·Δp; Where J represents a full-rank matrix; J T It represents the transpose of a full-rank matrix J; Further, in step S3, adjusting the position of the detection spot includes: S3.1. According to the formula: θ(k+1)=θ(k)+Δθ, obtain the deflection angle θ(k+1) required for the MEMS mirror assembly; Where θ(k) represents the deflection angle at time k; S3.2 Drive the MEMS mirror assembly to deflect according to the deflection angle θ(k+1) to adjust the position of the detection spot.

[0007] The beneficial effects of this invention are that it uses a MEMS mirror assembly, a first detection unit, and a second detection unit to form a closed-loop feedback link, which can detect the spot position deviation and the total intensity of the coupled light in real time, and adjust the deflection angle of the MEMS mirror assembly and the laser driving current in a closed loop to achieve real-time automatic closed-loop stable coupling. Moreover, it can adaptively compensate for the optical path offset caused by temperature fluctuations, mechanical vibrations, and structural creep without manual intervention, which significantly improves the long-term stability, service reliability, and maintainability of the fiber optic coupling system. It is suitable for high-precision fiber optic coupling applications such as industrial lasers, optical communication, and sensing detection. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the optical path connection of the present invention. Detailed Implementation

[0009] like Figure 1 As shown, a self-stabilizing fiber optic coupling system based on MEMS according to the present invention includes a laser emitting unit, a MEMS mirror assembly, a beam splitter 6, a focusing coupling unit, a fiber optic beam splitter 8, a first detection unit 10, a second detection unit 11, and a control unit 13. The laser beam emitted by the laser emitting unit is deflected by the MEMS mirror assembly and then incident on the beam splitter 6. The beam output by the beam splitter 6 is divided into two paths. One path is coupled into the fiber beam splitter 8 through the focusing coupling unit, and the other path is projected to the first detection unit 10. The fiber beam splitter 8 outputs the fiber beam splitter into the second detection unit 11. The first detection unit 10 uses a four-quadrant detector to output the detection spot position and total light intensity signal; The second detection unit 11 is used to output the fiber input power signal; The control unit 13 is connected to the laser emitting unit, the MEMS mirror assembly, the first detection unit 10, and the second detection unit 11. It is used to drive the deflection of the MEMS mirror assembly and adjust the laser current of the laser emitting unit to achieve real-time automatic closed-loop coupling.

[0010] The laser emitting unit includes a laser 1, and a backlight detector 12 built into or external to the laser 1 (in this embodiment, the backlight detector 12 is built into the laser 1) to acquire the laser 1's output power in real time; the control unit 13 is connected to both the laser 1 and the backlight detector 12 to receive the laser 1's operating laser power and backlight power.

[0011] Control unit 13 can be implemented in real time by an embedded digital signal processor or FPGA, with a compact and reliable structure. Control unit 13 has a multi-modal control mode, which includes the following execution strategies: a. When the fiber input power is lower than the set threshold and the backlight power decreases proportionally, it is determined that the laser 1 is attenuating. Then the control unit 13 adjusts the laser 1 drive current within a safe range to maintain the fiber input power. That is, the control unit 13 gradually increases the laser 1 drive current under the premise of not exceeding the maximum allowable current until the fiber input power is restored. b. When the fiber input power is lower than the set threshold and the backlight power is stable, it is determined that the optical path is offset or the coupling efficiency is reduced. Then, the position of the light spot detected by the first detection unit 10 is compared with the initial optimal position (factory calibration or recalibration update) to obtain the deviation. The MEMS reflector assembly is deflected to adjust the position of the detection light spot, that is, to restore the light spot to the optimal coupling position and realize the fiber input power recovery. c. When the position of the detection spot remains unchanged but the input fiber power is still lower than the set threshold, and the duration exceeds the threshold, it is determined that the output fiber 9 end face is damaged, contaminated, or defocused. The control unit 13 automatically starts micro-scanning, that is, the first MEMS reflector 4 and the second MEMS reflector 5 make small-range high-frequency disturbances with the reference point as the center, and search for the maximum input fiber power value through micro-scanning. If the maximum input fiber power value is still lower than the set threshold, an early warning signal is output; if a maximum input fiber power value greater than the set threshold can be found, the current deflection position of the MEMS reflector assembly is recorded, the new position is recorded as the temporary best point, and a prompt is made to check or recalibrate the output fiber 9 end face.

[0012] The control unit 13 has an automatic recalibration process built in, which can periodically or when misalignment is detected, scan the deflection angle of the MEMS mirror assembly and combine it with the fiber input power and spot position information to update the optimal coupling reference. For example, when the system runs every 24 hours or the temperature change exceeds 5°C, the recalibration process is automatically executed. That is, the spot position feedback is turned off, the deflection angle range of the MEMS mirror assembly is scanned with the current setting as the center, the spot position and fiber input power detected by the four-quadrant detector are recorded, and the four-quadrant coordinates and the deflection angle of the MEMS mirror assembly corresponding to the maximum fiber input power are found by using surface fitting, and the new reference is updated to eliminate long-term drift.

[0013] When the total light intensity signal output by the first detection unit 10 is less than the preset noise threshold, it is determined to be a loss of lock. Then the control unit 13 executes the loss of lock recovery strategy, expands the MEMS scanning range according to the Archimedes spiral trajectory, that is, drives the MEMS mirror assembly according to the spiral or grid scanning trajectory until the fiber input power is greater than the set threshold, and then switches back to the multi-mode control mode.

[0014] A collimating lens 2 and an optical isolator 3 are sequentially arranged in the optical path between the laser emitting unit and the MEMS mirror assembly. The focusing coupling unit uses a focusing lens 7, and the focused beam output from the focusing lens 7 is coupled into the output fiber 9. The signal output from the output fiber 9 is input to the fiber beam splitter 8, and the output fiber 9 and the fiber beam splitter 8 are fused together. At the same time, the system uses the optical isolator 3 to block the reflected light from most of the interfaces from returning to the laser 1, avoiding intensity noise and damage.

[0015] The reflectivity of the beam splitter 6 is 2%~5% to improve the detection signal-to-noise ratio; the beam splitter 8 has a splitting ratio of 1%~3%, which ensures detection sensitivity while minimizing the impact on output power.

[0016] The MEMS mirror assembly includes a first MEMS mirror 4 and a second MEMS mirror 5, both of which are two-dimensional micro-deflection mirrors. The light beam output from the optical isolator 3 is sequentially incident on the first MEMS mirror 4 and the second MEMS mirror 5, and the first MEMS mirror 4 and the second MEMS mirror 5 are arranged in parallel relative to each other.

[0017] A self-stabilizing fiber coupling method based on MEMS includes: Acquire the optical signal in the detection optical path and the position of the detection spot in the detection optical path where the laser beam is located; Based on the optical signal and the position of the detected light spot, it is determined whether the lock-out condition is met. If it is met, the lock-out recovery strategy is executed. If it is not met, the corresponding execution strategy in the multi-modal control mode is mapped and executed, thereby realizing real-time automatic closed-loop coupling.

[0018] Furthermore, when executing strategy b, the following steps are included: S1. Determine the initial position of the detection spot in the detection optical path where the laser beam is located; S2. Real-time detection of the real-time position of the detection spot, obtaining the offset of the detection spot based on the real-time position and the initial position, and obtaining the angle correction amount based on the offset; Further, in step S2, obtaining the offset of the detection spot includes: The position deviation is obtained based on the real-time position and the initial position: Δx=x0-x mems Δy=y0-y mems ; The offset is constructed based on the positional deviation: Δp=[Δx,Δy] T ; Where x0 and y0 are the real-time position coordinates of the detected light spot; x mems y mems To determine the initial maximum power position coordinates for detecting the light spot; Further, in step S2, obtaining the angle correction amount based on the offset includes: Pre-stored pseudo-inverse matrix J + =J T (JJ T ) -1 ; Pseudo-inverse matrix J + It can be pre-stored offline, without the need for real-time inversion; The required angle correction is obtained by decoupling using the pseudo-inverse matrix: Δθ = J + ·Δp; Where J represents a full-rank matrix (usually full-rank row matrix); J T It represents the transpose of a full-rank matrix J; By employing the Moore-Penrose pseudoinverse to solve for the minimum norm solution, the overall energy of the MEMS angle correction is minimized, thus avoiding full deflection on a single axis. S3. Adjust the position of the detection spot based on the angle correction amount; Further, in step S3, the position adjustment of the detection spot includes: S3.1 According to the formula: θ(k+1)=θ(k)+Δθ, the required deflection angle θ(k+1) of the MEMS mirror assembly is obtained, which is the deflection angle superimposed on the previous moment; Where θ(k) represents the deflection angle at time k; S3.2. Drive the MEMS mirror assembly to deflect according to the deflection angle θ(k+1) to adjust the position of the detection spot; S4. Repeat step S2 until the offset is zero, thereby achieving real-time automatic stable coupling.

[0019] In this invention, the laser beam emitted from laser 1 is collimated by collimating lens 2 to generate a parallel beam, and then passes through optical isolator 3 to prevent backlight interference from subsequent devices. The collimated parallel beam after optical isolation is deflected sequentially by first MEMS mirror 4 and second MEMS mirror 5, and then incident on beam splitter 6 (e.g., a beam splitter prism with a reflectivity of 5% and a transmittance of 95%). Beam splitter 6 transmits 95% of the transmitted light to focusing lens 7, and after focusing, it is directly coupled into the end face of output fiber 9. The 5% light spot reflected by beam splitter 6 is projected onto first detection unit 10 for spot position detection, obtaining the position of the light spot in the X and Y directions and the total light intensity signal. A fiber optic beam splitter 8 (such as a 1×2 single-mode coupler with a splitting ratio of 99:1) is connected to the fiber optic beam splitter 8. The fiber optic beam splitter 8 splits 1% of the optical power and connects it to the second detection unit 11 (such as a fiber-coupled photodetector) through a fiber optic pigtail to directly monitor the transmitted optical power (i.e., the input power) in the output fiber 9. The laser 1 has a built-in or external backlight detector 12 to acquire the output power of the laser 1 in real time. The control unit 13 receives the spot position signal of the first detection unit 10, the input power signal of the second detection unit 11, and the backlight power signal of the laser 1. It can also receive temperature signals and execute the corresponding execution strategy and lockout recovery strategy in the multi-mode control mode.

[0020] Compared with existing manually adjustable products, the present invention has the following technical advantages: (1) It can clearly distinguish various anomalies in the coupled link, realize accurate compensation and intelligent recovery, and realize real-time closed-loop self-stabilization of coupling efficiency without manual intervention, and has strong environmental adaptability. (2) By comparing the backlight power with the fiber input power, the root cause of power attenuation can be accurately identified, and erroneous adjustments can be prevented; (3) Directly monitor the transmission power within the output optical fiber 9, with a clear control target, and is not affected by changes in intermediate optical path loss; (4) Decoupling control eliminates oscillations caused by the linkage of the two mirrors, improving the speed and stability of position correction; (5) It has the ability to diagnose and warn of problems at the 9 end faces of the output optical fiber, thus avoiding ineffective compensation; (6) Automatic recalibration overcomes reference drift and provides excellent long-term stability; (7) The optical isolator 3 and the optimized beam splitting ratio improve the signal-to-noise ratio and the safety of the laser 1.

[0021] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0022] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A self-stabilizing fiber optic coupling system based on MEMS, characterized in that: The system includes a laser emitting unit, a MEMS mirror assembly, a beam splitter, a focusing and coupling unit, an optical fiber beam splitter, a first detection unit, a second detection unit, and a control unit. The laser emitting unit outputs a beam that is deflected by the MEMS mirror assembly and then incident on the beam splitter. The beam splitter splits the beam into two paths: one path is coupled into the optical fiber beam splitter via the focusing and coupling unit, and the other path is projected onto the first detection unit. The split beam output from the optical fiber beam splitter is then incident on the second detection unit. The first detection unit uses a four-quadrant detector to output the detection spot position and total light intensity signal; The second detection unit is used to output the fiber input power signal; The control unit is connected to the laser emitting unit, the MEMS mirror assembly, the first detection unit, and the second detection unit. It is used to drive the deflection of the MEMS mirror assembly and adjust the laser current of the laser emitting unit to achieve real-time automatic closed-loop coupling.

2. The self-stabilizing fiber optic coupling system based on MEMS according to claim 1, characterized in that: The laser emitting unit includes a laser, which is connected to a backlight detector. The control unit is connected to both the laser and the backlight detector to receive the operating laser power of the laser and the backlight power.

3. The self-stabilizing fiber optic coupling system based on MEMS according to claim 2, characterized in that: The control unit has a multimodal control mode, which includes the following execution strategies: a. When the fiber input power is lower than the set threshold and the backlight power decreases proportionally, it is determined to be laser attenuation. In this case, the laser drive current is adjusted within a safe range to maintain the fiber input power. b. When the fiber input power is lower than the set threshold and the backlight power is stable, it is determined that there is an optical path offset or a change in coupling efficiency. Then, the MEMS reflector assembly is deflected to adjust the position of the detection spot. c. When the position of the detection spot remains unchanged and the input fiber power is still lower than the set threshold, it is determined that the output fiber end face is damaged or the focus is off-focus. The control unit triggers the MEMS mirror assembly to micro-scan and search for the maximum input fiber power value. If the maximum input fiber power value is still lower than the set threshold, an early warning signal is output. If a maximum input fiber power value greater than the set threshold can be found, the current deflection position of the MEMS mirror assembly is recorded, and a prompt is made to check the output fiber end face.

4. The self-stabilizing fiber optic coupling system based on MEMS according to claim 3, characterized in that: When the total light intensity signal output by the first detection unit is less than the preset noise threshold, it is determined to be a loss of lock. The control unit then executes the loss of lock recovery strategy, drives the MEMS mirror assembly according to the Archimedes spiral trajectory until the fiber input power is greater than the set threshold, and then switches back to the multi-mode control mode.

5. The self-stabilizing fiber optic coupling system based on MEMS according to claim 1, characterized in that: A collimating lens and an optical isolator are sequentially arranged in the optical path between the laser emitting unit and the MEMS mirror assembly. The focusing coupling unit uses a focusing lens, and the focused beam output by the focusing lens is coupled into the output optical fiber. The signal output by the output optical fiber is input to the optical fiber beam splitter, and the output optical fiber is fused to the optical fiber beam splitter. The reflectivity of the beam splitter is 2%~5%, and the splitting ratio of the optical fiber beam splitter is 1%~3%. The MEMS mirror assembly includes a first MEMS mirror and a second MEMS mirror, both of which are two-dimensional micro-deflection mirrors. The beam output by the optical isolator is sequentially incident on the first MEMS mirror and the second MEMS mirror, and the first MEMS mirror and the second MEMS mirror are arranged parallel to each other.

6. A self-stabilizing fiber coupling method based on MEMS, characterized in that: The method is applied to the MEMS-based self-stabilizing fiber optic coupling system as described in any one of claims 1-5, and the method includes: Acquire the optical signal in the detection optical path and the position of the detection spot in the detection optical path where the laser beam is located; Based on the optical signal and the position of the detected light spot, it is determined whether the lock-out condition is met. If it is met, the lock-out recovery strategy is executed. If it is not met, the corresponding execution strategy in the multi-modal control mode is mapped and executed, thereby realizing real-time automatic closed-loop coupling.

7. The self-stabilizing fiber coupling method based on MEMS according to claim 6, characterized in that: When executing strategy b, the following steps are included: S1. Determine the initial position of the detection spot in the detection optical path where the laser beam is located; S2. Real-time detection of the real-time position of the detection spot, obtaining the offset of the detection spot based on the real-time position and the initial position, and obtaining the angle correction amount based on the offset; S3. Adjust the position of the detection spot based on the angle correction amount; S4. Repeat step S2 until the offset is zero, thereby achieving real-time automatic stable coupling.

8. The self-stabilizing fiber coupling method based on MEMS according to claim 7, characterized in that: In step S2, obtaining the offset of the detection spot includes: The position deviation is obtained based on the real-time position and the initial position: Δx=x0-x mems ,Δy=y0-y mems ; The offset is constructed based on the positional deviation: Δp=[Δx,Δy] T ; Where x0 and y0 are the real-time position coordinates of the detected light spot; x mems y mems The initial maximum power position coordinates were determined to detect the light spot.

9. The self-stabilizing fiber coupling method based on MEMS according to claim 8, characterized in that: In step S2, obtaining the angle correction amount based on the offset includes: Pre-stored pseudo-inverse matrix J + =J T (JJ T ) -1 ; The required angle correction is obtained from the pseudo-inverse matrix: Δθ = J + ·Δp; Where J represents a full-rank matrix; J T It represents the transpose of a full-rank matrix J.

10. A self-stabilizing fiber coupling method based on MEMS according to claim 9, characterized in that: In step S3, adjusting the position of the detection spot includes: S3.

1. According to the formula: θ(k+1)=θ(k)+Δθ, obtain the deflection angle θ(k+1) required for the MEMS mirror assembly; Where θ(k) represents the deflection angle at time k; S3.2 Drive the MEMS mirror assembly to deflect according to the deflection angle θ(k+1) to adjust the position of the detection spot.

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