Return light monitoring device and monitoring adjustment method thereof

Abstract

The present application relates to a kind of back light monitoring device and its monitoring adjustment method, including positive and negative light separator, back light power attenuator and control circuit system;For separating positive and negative laser, positive and negative light separator includes 3 ports, laser enters from the input port Port1 of positive and negative light separator, and from output port Port2 output, back light is from output port Port2 from side port Port3 output after entering back light power attenuator, back light power attenuator carries out power attenuation to back light and sends control circuit system monitoring. By adjusting the length of optical fiber fusion coupling part, the optical path of positive and negative laser is separated, the power attenuation of back light is carried out using diffuse reflection principle, the rated optical power that attenuator can bear is flexibly changed by adjusting attenuation rate online, with simple structure, low cost and high reliability, etc. The intensity of back light can be accurately monitored, and protective measures can be taken in time, effectively avoiding the damage of laser caused by back light.

Description

[0001] This application is a divisional application of the invention patent application filed on January 28, 2022, with the China National Intellectual Property Administration, entitled "Return Light Monitoring Device and Monitoring and Adjustment Method Thereof", application number 202111327647.1. Technical Field

[0002] This invention relates to laser technology, and more particularly to a backlight monitoring device and its monitoring and adjustment method. Background Technology

[0003] With the development of laser technology, the output power of fiber lasers is constantly increasing, and application scenarios are becoming more complex, placing higher demands on the anti-reflection capability of fiber lasers. During normal operation or processing, some laser light will reflect back along its original path, affecting the core components inside the laser. When the intensity of the reflected light reaches a certain threshold, it can lead to laser instability or irreversible damage. Therefore, accurately monitoring the intensity of the reflected light and taking timely protective measures can effectively prevent laser damage caused by excessively strong reflected light.

[0004] To address the aforementioned issues, prior art CN 111106512 A provides a monitoring device, fiber laser, and method for handling reflected light, including an attenuation unit, a photoelectric monitor, a temperature monitor, and a processor. The attenuation unit reduces the reflected light entering the fiber laser, and the processor receives and determines whether the photoelectric signal output from the photoelectric monitor and the temperature signal output from the temperature monitor exceed a first preset threshold. The processor also controls the fiber laser to stop operating when the photoelectric signal and temperature signal exceed the first preset threshold. While this prior art solution solves the problem of reflected light damaging the fiber laser, the attenuation unit has a limited optical power tolerance. When the reflected light power exceeds its rated power, irreversible damage to the attenuation unit occurs, causing the reflected light monitoring device to malfunction. Summary of the Invention

[0005] To address the issue of backlight processing in fiber lasers, a backlight monitoring device and its monitoring and adjustment method are proposed. By adjusting the length of the fused coupling section of the fiber, the optical paths of the forward and reverse lasers are separated. The power of the backlight is attenuated using the principle of diffuse reflection. The rated optical power that the attenuator can withstand can be flexibly changed by adjusting the attenuation rate online. The intensity of the backlight can be accurately monitored and protective measures can be taken in a timely manner.

[0006] The technical solution of the present invention is as follows: a backlight monitoring device, comprising a forward and reverse light separator, a backlight power attenuator, and a control circuit system; the forward and reverse light separator for separating forward and reverse lasers includes three ports: Port1, Port2, and Port3. After the laser enters from the input port Port1 of the forward and reverse light separator, it is output from the output port Port2. The backlight enters the forward and reverse light separator from the output port Port2, and the reverse light is output from the side port Port3 and then enters the backlight power attenuator. The backlight power attenuator attenuates the power of the backlight and outputs it to the control circuit system for monitoring.

[0007] Preferably, the forward and reverse optical splitter is formed by melting and drawing two double-clad optical fibers; the double-clad optical fibers are the main optical fiber and the side arm optical fiber branched from the main optical fiber.

[0008] Preferably, the main optical fiber has a main optical fiber core at its center, which is wrapped by a main optical fiber cladding. A main optical fiber coating layer is applied to the outside of the main optical fiber cladding. Along the forward optical path, there is a main optical fiber cladding light leakage section at the front end of the side arm optical fiber.

[0009] Preferably, the return light power attenuator includes a return light reflection module, a return light output fiber, and a return light detection module. The return light output fiber is the output port Port3 in the forward and reverse light splitter. The return light output fiber leads the return light to the return light reflection module. After the return light is reflected and attenuated by the return light reflection module, it is detected by the return light detection module and output to the control circuit system.

[0010] Preferably, the surface of the retroreflection module is roughened to attenuate the retroreflection due to diffuse reflection. The attenuation coefficient α is expressed by the formula: α∝κ·l f ·θ f , where l f θ is the perpendicular distance between the end face of the return light output fiber and the surface of the return light reflection module. f κ is the angle between the return light output fiber and the surface of the return light reflection module 20, and κ is the surface roughness of the return light reflection module; the received diffuse reflection light power P s Relationship: Among them, l p θ is the perpendicular distance between the surfaces of the return light detection module and the return light reflection module. p The angle between the surfaces of the return light detection module and the return light reflection module.

[0011] A forward and reverse light splitter for laser forward and reverse light separation comprises two double-clad optical fibers fused together, including a main fiber and side-arm fibers branching off from the main fiber. The main fiber core is located at the center of the main fiber, which is wrapped by the main fiber cladding. A main fiber coating layer is applied to the outside of the main fiber cladding. Along the forward light path, there is a main fiber cladding light leakage section at the leading end of the side-arm fiber. The fused coupling length between the main fiber and the side-arm fiber is l. r The length of the optical leakage section in the cladding of the main optical fiber is l x The diameter of the main fiber core 100 is d1, and the diameter of the main fiber cladding is d2. The laser is input from one end of the main fiber, Port1, and output from the other end, Port2. The return light enters from the output end of the main fiber, Port2, and outputs from the side arm fiber port, Port3.

[0012] Preferably, the forward optical isolation of the forward and reverse optical splitter is 1550 nm. 1-2 IS 1-2 Relationship:

[0013]

[0014] Among them, P 1-3 P1 represents the optical power entering Port3 from Port1, and P1 represents the total forward laser power injected into Port1 at the main fiber input end, including the main fiber cladding optical power and the fiber core optical power; x The longer, P 1-3 The smaller, IS 1-2 The higher;

[0015] The reverse laser transmittance T of the forward and reverse light separator 2-3 Relationship: Among them, P 2-3 P2 is the optical power entering Port3 from Port2, and P2 is the total return optical power injected into Port2. r The longer, P 2-3 The larger T is 2-3 The higher.

[0016] Preferably, the forward laser isolation degree IS of the forward and reverse light separator is... 1-2 >20dB, the reverse laser transmittance T of the forward and reverse light splitter 2-3 >97%.

[0017] Preferably, the main optical fiber is a double-clad passive optical fiber that matches the optical path of the laser, and the side arm optical fibers are multimode or single-mode double-clad optical fibers.

[0018] A method for adjusting backlight monitoring includes a backlight monitoring device, and the adjustment steps are as follows:

[0019] S1. The return light is coupled into the return light monitoring device and transmitted in the reverse direction to the forward and reverse light separator; the forward and reverse light separator separates the optical paths of the forward laser and the reverse laser.

[0020] S2. The reverse transmission return light is coupled to Port3 and enters the return light output fiber of the return light power attenuator. It is then led out from the inside of the return light monitoring device and monitored. The monitoring and adjustment steps are as follows: S201 to S203.

[0021] S201. Adjust the angle and distance between the return light output fiber and the return light reflection module; adjust the attenuation coefficient α online.

[0022] S202, The return light reflection module attenuates the power of the return light;

[0023] S203, The retroreflection detection module receives the retroreflected light after diffuse reflection, performs photoelectric signal conversion, and adjusts the power of the received retroreflected light online;

[0024] S3. The control circuit system reads the electrical signal from the return light monitor and controls the working state of the laser; the laser is turned off when the electrical signal exceeds the threshold.

[0025] The beneficial effects of this invention are as follows: The backlight monitoring device and its monitoring and adjustment method of this invention separate the optical paths of the forward and reverse lasers by adjusting the length of the fiber fusion coupling part, and use the principle of diffuse reflection to attenuate the power of the backlight. The rated optical power that the attenuator can withstand can be flexibly changed by adjusting the attenuation rate online. It has the characteristics of simple structure, low cost and high reliability. It can accurately monitor the intensity of the backlight and take protective measures in time, and can effectively avoid laser damage caused by backlight. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the backlight monitoring device of the present invention;

[0027] Figure 2 This is a schematic diagram of the forward and reverse light splitter structure of the present invention;

[0028] Figure 3 This is a schematic diagram of the forward light isolation of the forward and reverse light separator of the present invention;

[0029] Figure 4 This is a schematic diagram showing the forward light transmittance of the forward and reverse light separator of the present invention;

[0030] Figure 5 This is a schematic diagram of the reverse light transmission path of the forward and reverse light splitter of the present invention;

[0031] Figure 6 This is a schematic diagram showing the reverse light transmittance of the forward and reverse light separator of the present invention;

[0032] Figure 7 This is a schematic diagram illustrating the working principle of the return optical power attenuator of the present invention.

[0033] Figure 8 This is a flowchart of the backlight monitoring and adjustment method of the present invention.

[0034] Figure labels: 1. Forward and reverse light splitter; 10. Main optical fiber; 100. Main optical fiber core; 101. Main optical fiber cladding; 102. Main optical fiber coating; 103. Main optical fiber cladding light leakage section; 11. Side arm optical fiber; 2. Return light power attenuator; 20. Return light reflection module; 21. Return light output fiber; 22. Return light detection module; 3. Control circuit system. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] like Figure 1 The schematic diagram of the return beam monitoring device shown includes a forward and reverse beam splitter 1, a return beam power attenuator 2, and a control circuit system 3. The forward and reverse beam splitter 1 separates forward and reverse laser beams and includes three ports: Port1, Port2, and Port3. The laser beam enters through the input port Port1 of the forward and reverse beam splitter 1 and exits through the output port Port2. The return beam beam enters through the output port Port2 and exits through the side port Port3, then enters the return beam power attenuator 2. After power reduction, the beam is sent to the control circuit system 3 for monitoring.

[0037] like Figure 2 The schematic diagram of the forward and reverse optical splitter shown illustrates the forward and reverse optical splitter: used to separate the optical paths of forward and reverse lasers, it is formed by fusion drawing of two double-clad optical fibers; it includes a main optical fiber 10 and side-arm optical fibers 11 branching off from the main optical fiber 10, wherein the main optical fiber 10 is a double-clad optical fiber with a main optical fiber core 100 at its center, which is wrapped by a main optical fiber cladding 101, and a main optical fiber coating layer 102 is coated on the outside of the main optical fiber cladding. Along the forward optical path, there is a main optical fiber cladding light leakage section 103 at the front end of the side-arm optical fiber 11; r The length of the fused coupling portion of the main fiber 10 and the side arm fiber 11, l x d1 is the length of the optical leakage section 103 of the main fiber cladding, d1 is the diameter of the main fiber core 100, and d2 is the diameter of the main fiber cladding 101; solid arrows indicate the forward laser transmission optical path and direction (Port1 to Port2), and dashed arrows indicate the reverse laser transmission optical path and direction (Port2 to Port3).

[0038] The forward laser includes the laser signal light and pump light. Most of the signal light propagates in the core 100 of the main fiber, while a small portion of the higher-order mode signal light and residual pump light not absorbed by the gain medium propagates in the cladding 101 of the main fiber. To improve the separation between the forward and reverse laser beams, it is necessary to prevent the forward laser from propagating from Port1 to Port3. Here, the laser power ratio from Port1 to Port3 is defined as the forward beam isolation IS. 1-2 IS 1-2 Relationship:

[0039]

[0040] Among them, P 1-3 P1 represents the optical power entering Port3 from Port1, and P1 represents the total forward laser power injected into the main fiber input port Port1 (including the main fiber cladding optical power and the fiber core optical power). For example... Figure 3 As shown, θ1 represents the incident light angle entering the main fiber cladding 101, and θ2 represents the incident light angle entering the main fiber core 100. According to the principle of light transmission (total internal reflection), laser light with an incident light angle satisfying the core NA (numerical aperture) propagates in the main fiber core 100, i.e., from Port1 to Port2; laser light with an incident light angle satisfying the cladding NA propagates in the main fiber cladding 101, entering from Port1 and propagating to Port2, and possibly to Port3. To improve the forward laser isolation IS... 1-2 Cladding light leakage treatment is performed on the main optical fiber, such as... Figure 4 As shown, when the angle θ1 of the injected light at Port1 is constant, P 1-3 The length l of the optical leakage section 103 of the main fiber cladding x Related to: l x The longer, P 1-3 The smaller, IS 1-2 The higher.

[0041] Reverse laser light includes the light reflected back from the end face of the laser output fiber and the light reflected back from the surface of a material during laser processing. For example... Figure 5 As shown, the reverse laser is coupled into the fiber through the fiber endface. Since d2 > d1, the reflected light power coupled into the cladding is significantly greater than the reflected light power coupled into the fiber core. To improve the separation between the forward and reverse lasers, it is necessary to prevent the reverse laser from propagating from Port2 to Port1. Figure 5 ), improving the transmittance from Port2 to Port3 ( Figure 6 Reverse laser transmittance T 2-3 Relationship: Among them, P 2-3 P2 is the optical power entering Port3 from Port2, and P2 is the total return optical power injected into Port2; for example Figure 6As shown, when the injection angle θ3 (i.e., the return injection angle) at Port2 is constant, P 2-3 With l r Related to length: l r The longer, P 2-3 The larger T is 2-3 The higher.

[0042] In the manufacturing process of the forward and reverse light splitter, by monitoring P 1-3 and P 2-3 Adjust the length of the optical leakage section 103 of the main fiber cladding online. x and the length l of the fused coupling section of the two optical fibers r To fabricate forward and reverse beam splitters that meet application requirements, the forward laser isolation (IS) is required. 1-2 >20dB, reverse laser transmittance T 2-3 >97%; the main fiber can be a double-clad passive fiber that matches the laser optical path, including but not limited to 10 / 125, 20 / 400, 30 / 250, 50 / 400, etc., and the side arm fiber can be a multimode or single-mode double-clad fiber, including but not limited to 10 / 125, 20 / 130, 105 / 125, 135 / 155, 200 / 220, etc.

[0043] Return optical power attenuator 2, such as Figure 7 As shown, the return light output fiber 21 is the output port Port3 in the forward and reverse light splitter 1, which guides the return light from the laser to the return light reflection module 20. The total power of the return light received by the return light reflection module 20 is P3. The surface of the return light reflection module 20 needs to be roughened to reflect the received return light using the principle of diffuse reflection. The power of the P3 return light is attenuated after passing through the return light reflection module 20. The attenuation coefficient α is expressed by the following relationship: α∝κ·l f ·θ f , where l f θ is the perpendicular distance between the end face of the return light output fiber 21 and the surface of the return light reflection module 20. f Let α be the angle between the return light output fiber 21 and the surface of the return light reflection module 20, and let κ be the surface roughness of the return light reflection module 20. If l f θ f The larger κ is, the larger α is, and correspondingly, the attenuation of the returned light power by the return light reflection module 20 is greater. The attenuated light power is P. r The reflected light from the return light reflection module 20 is received by the return light detection module 22, and the received diffuse reflection light power P s Relationship: Among them, l p θ is the perpendicular distance between the surfaces of the retroreflector module 22 and the retroreflector module 20.p Let l be the angle between the surfaces of the retroreflector module 22 and the retroreflector module 20. p θ p The larger α is, the greater P s The smaller; in summary, by adjusting l f θ f l p θ p The power attenuation rate β = (P3 - P) can be adjusted online. s ) / P3, when P s At a certain time (P) s The greater the attenuation rate β, the greater the total power P3 of the returned light received by the returned light reflection module 20, which means the rated power that the attenuator can withstand increases.

[0044] The control circuit system 3 is connected to the return light detection module 22 in the return light power attenuator 2. It is used to determine whether the electrical signal exceeds the threshold and to turn off the laser when the judgment condition is met, thereby protecting the laser from damage by the return light.

[0045] like Figure 8 As shown, a flowchart of a backlight monitoring and adjustment method includes:

[0046] S1, the return light is coupled into the return light monitoring device and transmitted in the opposite direction to the forward and reverse light separator; the forward and reverse light separator 1 separates the optical paths of the forward laser and the reverse laser of the laser.

[0047] S2, the reverse-transmitted return light is coupled to Port3 and enters the return light output fiber 21 of the return light power attenuator. It is then led out from inside the return light monitoring device and monitored. The monitoring and adjustment steps are as follows: S201 to S203.

[0048] S201, adjust the angle and distance between the return light output fiber 21 and the return light reflection module 20; adjust the attenuation coefficient α online.

[0049] S202, the return light reflection module 20 attenuates the power of the return light.

[0050] S203, the return light detection module 22 receives the return light after diffuse reflection and performs photoelectric signal conversion; it also adjusts the power of the received return light online.

[0051] S3, the control circuit system 3 reads the electrical signal from the return light detection module 22 and controls the working state of the laser; the laser is turned off when the electrical signal exceeds the threshold.

[0052] Example:

[0053] Forward and reverse optical splitter: Used to separate the optical paths of forward and reverse lasers, and to guide the returned light from the reverse transmission out of the laser via Port3; in this embodiment, 30 / 250 (d1 = 30um, d2 = 250um) passive optical fiber is used as the main fiber, and 105 / 135 (d1 = 105um, d2 = 135um) passive optical fiber is used as the side arm fiber, and the process control parameter is l. x l r By monitoring the power of Port3, the isolation and transmittance are controlled to meet the IS requirements. 1-2 >25dB, T 2-3 >98%, the final structure is as follows Figure 1 The forward and reverse light separator 1 is shown.

[0054] Return beam power attenuator: In this embodiment, a frosted aluminum block coated with black paint is used as the 20-stage return beam reflection module; in this embodiment, when l f =1cm, θ f =6°; l p =3cm, θ p At a constant angle of 10°, the attenuator can withstand a return optical power of >10W and achieve a power attenuation of >20dB; when l f =2cm, θ f =10°; l p =3cm, θ p At 12°, the attenuator can withstand a return optical power of >25W and achieve a power attenuation of >30dB.

[0055] Control circuit system: Connected to the backlight detection module, it reads the electrical signal from the backlight detection module and determines whether it exceeds a threshold. When the electrical signal exceeds the threshold, a protection mechanism is activated to shut down the laser, thereby protecting the laser from damage caused by backlight. In this embodiment, the maximum backlight power threshold that the laser can withstand is 30W. At this time, the voltage value measured by the backlight detection module is 0.245V. This value is set as the voltage threshold. When the backlight power is >30W, the control circuit system triggers the protection mechanism to shut down the laser.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A retroreflection monitoring device, characterized in that, This includes forward and reverse beam splitters, return beam power attenuators, and control circuitry. The forward and reverse beam splitter for separating forward and reverse laser beams is made of two double-clad optical fibers fused together and includes a main fiber and a side arm fiber branching off from the main fiber. It includes a first port, a second port, and a third port. The laser beam enters from the first port at one end of the main fiber and exits from the second port at the other end. The return beam enters the forward and reverse beam splitter from the second port, and the reverse beam exits from the third port of the side arm fiber before entering the return beam power attenuator. The return beam power attenuator attenuates the power of the return beam before outputting it to the control circuit system for monitoring. The return light power attenuator includes a return light reflection module, a return light output fiber, and a return light detection module. The return light output fiber is the third port in the forward and reverse light splitter. The return light output fiber leads the return light to the return light reflection module. After the return light is reflected and attenuated by the return light reflection module, it is detected by the return light detection module and output to the control circuit system. The surface of the retroreflective module is roughened to attenuate the diffuse reflection of the retroreflective light. The attenuation coefficient α is expressed by the formula: α∝κ·l f ·θ f , where l f θ is the perpendicular distance between the end face of the return light output fiber and the surface of the return light reflection module. f κ is the angle between the return light output fiber and the surface of the return light reflection module; P is the surface roughness of the return light reflection module. s Relationship: P s ∝ ,in, l p θ is the perpendicular distance between the surfaces of the return light detection module and the return light reflection module. p The angle between the surfaces of the return light detection module and the return light reflection module.

2. The retroreflection monitoring device according to claim 1, characterized in that, The main optical fiber has a core at its center, which is surrounded by a cladding. A main optical fiber coating layer is applied to the cladding. Along the forward optical path, there is a cladding light leakage section at the front end of the side arm fiber. The fusion coupling length between the main optical fiber and the side arm fiber is lr, and the length of the cladding light leakage section is lx. The laser enters from the first port at one end of the main optical fiber and exits from the second port at the other end. The return light enters from the second port and exits from the third port of the side arm fiber. The forward optical isolation of the forward / reverse optical splitter is IS. 1-2 IS 1-2 Relationship: IS 1-2 = 10 lg , Among them, P 1-3 P1 represents the optical power entering the third port from the first port, and P1 represents the total forward laser power injected into the first port of the main fiber, including the optical power of the main fiber cladding and the optical power of the fiber core. x The longer, P 1-3 The smaller, IS 1-2 The higher; The reverse laser transmittance T of the forward and reverse light separator 2-3 Relationship: T 2-3 = 100%, of which, P 2-3 P1 is the optical power entering the third port from the second port, and P2 is the total return optical power injected into the second port. r The longer, P 2-3 The larger T is 2-3 The higher.

3. The retroreflection monitoring device according to claim 2, characterized in that, Control parameter l x l r By monitoring the power of the third port, the isolation and transmittance are controlled to meet the IS requirements. 1-2 >20dB, T 2-3 >97%.

4. The retroreflection monitoring device according to claim 1 or 2, characterized in that, The main optical fiber is a double-clad passive optical fiber that matches the optical path of the laser, and the side arm optical fibers are multimode or single-mode double-clad optical fibers.

5. The retroreflection monitoring device according to claim 2, characterized in that, By adjusting l f θ f l p θ p Parameters, online adjustment of power attenuation rate β=(P3) P s ) / P3, where P3 is the total power of the returned light received by the return light reflection module; making P s The optical power is less than the damage threshold of the return light detection module.

6. A method for adjusting the backlight monitoring of the backlight monitoring device according to claim 1, characterized in that, The adjustment steps are as follows: The returned light is coupled into the returned light monitoring device and transmitted in the reverse direction to the forward and reverse light separator; the forward and reverse light separator separates the optical paths of the forward laser and the reverse laser of the laser. The reverse-transmitted return light is coupled to the third port and enters the return light output fiber of the return light power attenuator; The return light output from the return light output fiber is directed to the return light reflection module; Adjust the attenuation coefficient α of the retroreflection module online; The reflected light module attenuates the power of the reflected light. The power Ps of the returned light received by the online returned light detection module is adjusted to further attenuate the power of the returned light arriving at the returned light detection module. The return light detection module performs photoelectric signal conversion on the return light after power attenuation; The control circuit system reads the electrical signal from the return light detection module and controls the working state of the laser; the laser is turned off when the electrical signal exceeds a threshold.

7. The method for monitoring and adjusting reflected light according to claim 6, characterized in that, Control parameter l x l r By monitoring the power of the third port, the isolation and transmittance are controlled to meet the IS requirements. 1-2 >20dB, T 2-3 >97%.

8. The method for monitoring and adjusting reflected light according to claim 6 or 7, characterized in that, The return light power attenuator uses an aluminum block with a frosted surface and black paint as the return light reflection module. When adjusting l f =1cm, θ f =6°; l p =3cm, θ p At α = 10°, the attenuator can withstand >10W of return optical power and achieve power attenuation of α > 20dB; or When adjusting l f =2cm, θ f =10°; l p =3cm, θ p At 12°, the attenuator can withstand a return optical power of >25W and achieve a power attenuation of α>30dB.

9. The method for monitoring and adjusting reflected light according to claim 6, characterized in that, It also includes the following steps: By adjusting the angle θ between the return light output fiber and the return light reflection module f The perpendicular distance l between the end face of the return light output fiber and the surface of the return light reflection module f Adjust the attenuation coefficient α online; By adjusting the angle θ between the surface of the reflected light detection module and the reflected light reflection module... p The vertical distance l between the surfaces of the return light detection module and the return light reflection module p Adjust the received return optical power Ps online.

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