An optical system and a monitoring method for monitoring stimulated Brillouin scattering effect

Abstract

The application provides an optical system and a monitoring method for monitoring stimulated Brillouin scattering effect. The optical system for monitoring stimulated Brillouin scattering effect firstly delivers a narrow linewidth seed source into a laser amplifier through a first optical device to amplify the narrow linewidth laser, and guides stimulated Brillouin scattering light generated by the laser amplifier to a back light monitoring module to detect the back light power and spectral components of the stimulated Brillouin scattering light in real time through the back light monitoring module, so as to realize the purpose of simultaneously and accurately measuring the stimulated Brillouin scattering light power and observing the laser components, and is more conducive to judging whether the stimulated Brillouin scattering effect occurs. Further, the optical system can adjust the light splitting ratio of the first optical device and the back light monitoring module to protect the narrow linewidth seed source and the spectrometer in the back light monitoring module from the damage of the back light to the greatest extent, and achieve the purpose of accurately judging the stimulated Brillouin scattering effect and protecting the system safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of narrow linewidth fiber laser, and particularly relates to an optical system and a monitoring method for monitoring stimulated Brillouin scattering effect. BACKGROUND

[0002] Narrow linewidth fiber laser has wide application value in the fields of gravitational wave detection, laser radar, nonlinear frequency conversion, coherent beam combination, spectral beam combination and laser weapon. With the continuous improvement of the output power of the current narrow linewidth fiber laser, due to the small cross-sectional area of the fiber core, the energy density of the fiber core increases, and when the output power reaches a certain level, various nonlinear effects are easily generated to limit the further improvement of the output performance. Among these nonlinear effects, the threshold power of stimulated Brillouin scattering effect is relatively low, which is the main factor limiting the improvement of the output power of the narrow linewidth fiber laser. When the output power is improved to a certain level, the amplified signal light is coupled into the backward transmission of the stimulated Brillouin scattering light, and the backward transmission of the self-pulse is randomly generated, and the peak power is much higher than the average power of the signal light, which is extremely destructive. It is particularly important to monitor the stimulated Brillouin scattering effect in time and accurately to protect the safety of the narrow linewidth fiber laser system.

[0003] In the existing narrow linewidth fiber laser system, there are four schemes for monitoring stimulated Brillouin scattering effect: the first scheme is to monitor the backward light power. When the backward light power exceeds one ten-thousandth (sometimes defined as one thousandth) of the output power, the stimulated Brillouin scattering effect occurs, or the growth curve of the backward light power with the output power is recorded. When the backward light power shows a significant nonlinear growth, it is determined that the stimulated Brillouin scattering effect occurs. The second scheme is to collect the spectrum composition of the backward light by a spectrometer. With the occurrence of the stimulated Brillouin scattering effect exceeding the threshold, the stimulated Brillouin scattering light first appears on the backward spectrum, which is frequency shifted by 10MHz order relative to the signal light, and then the pulse peak appears around the stimulated Brillouin scattering light, and the number gradually increases and the spectrum position appears randomly. The third scheme is to monitor the intensity of the backward light power by a high-frequency photodetector through an oscilloscope. The oscilloscope can directly observe the high-frequency pulse. When the high-frequency pulse appears, the stimulated Brillouin scattering effect occurs. The fourth scheme is disclosed in CN117490985A. A stimulated Brillouin scattering online monitoring method, system, device and medium are disclosed. The method obtains the power data at different times in a set time period, the intensity of the backward light power and the intensity of the light on the backward light spectrum at the current time, analyzes the data models of the three, comprehensively judges the final probability of the occurrence of the stimulated Brillouin scattering at the current time, and realizes the online monitoring of the stimulated Brillouin scattering.

[0004] Of these four methods, the first method is simple and requires minimal equipment, but its reliance on a single method can be affected by interference from the laser system. For example, in addition to stimulated Brillouin scattering, there is residual pump light in the returned light, which can sometimes dominate the returned light. Using only one ten-thousandth of the output power can lead to inaccuracies. The second method is direct and effective, but if scattered light is collected, stimulated Brillouin scattering may not be observed, and the spectrum may be distorted. If the returned light is directly connected, excessive power can damage the spectrometer, resulting in low system safety. The third method has good time sensitivity, but it is susceptible to noise when used alone, and the pulse can be easily submerged in the initial stage, making it difficult to judge immediately and resulting in poor system reliability. The fourth method has high reliability, but its complex structure makes it difficult to widely adopt.

[0005] Therefore, there is an urgent need for an optical system and monitoring method for monitoring stimulated Brillouin scattering to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide an optical system and method for monitoring stimulated Brillouin scattering (SBS), which improves upon existing SBS monitoring systems by addressing technical problems such as limited monitoring capabilities, low security, poor reliability, and system complexity.

[0007] To solve the above-mentioned technical problems, the present invention first provides an optical system for monitoring stimulated Brillouin scattering, including a narrow linewidth seed source, a first optical device, a laser amplifier, and a backlight monitoring module. The first input terminal of the first optical device is connected to the output terminal of the narrow linewidth seed source, the second input terminal of the first optical device is connected to the input terminal of the backlight monitoring module, and the first output terminal of the first optical device is connected to the input terminal of the laser amplifier.

[0008] The first optical device is used to deliver the narrow linewidth seed source to the laser amplifier for narrow linewidth laser amplification, and to export the stimulated Brillouin scattering light generated by the laser amplifier to the backlight monitoring module; the backlight monitoring module is used to detect the backlight power and spectral composition of the stimulated Brillouin scattering light in real time.

[0009] Preferably, the narrow linewidth seed source outputs linearly polarized laser or non-linearly polarized laser. The narrow linewidth seed source has a structure of a linear cavity oscillator or a ring cavity oscillator. The operating wavelength of the narrow linewidth seed source includes the 1.0µm band, the 1.5µm band, or the 2.0µm band. The linewidth of the narrow linewidth seed source is less than 0.1nm.

[0010] Preferably, the first optical device includes any one of a 2×2 first coupler with a splitting ratio of a:(100-a), a three-port isolator, and a circulator, where a is any number greater than 0 and less than 100.

[0011] Preferably, when the first optical device is a 2×2 first coupler, the splitting ratio of the first input terminal of the first optical device is a, the splitting ratio of the second input terminal of the first optical device is 100-a, the splitting ratio of the first output terminal of the first optical device is a, and the splitting ratio of the second output terminal of the first optical device is 100-a.

[0012] Preferably, the laser amplifier is a linearly polarized laser amplification structure or a non-linearly polarized laser amplification structure, and the pumping structure of the laser amplifier is any one of a forward pumping structure, a reverse pumping structure, or a dual-ended pumping structure.

[0013] Preferably, the backlight monitoring module includes a second optical device, a power meter, a laser attenuator, and a spectrometer. The input terminal of the second optical device is connected to the second input terminal of the first optical device, the first output terminal of the second optical device is connected to the power meter, the second output terminal of the second optical device is connected to the input terminal of the laser attenuator, and the output terminal of the laser attenuator is connected to the spectrometer.

[0014] Preferably, the second optical device includes a 1×2 second coupler with a splitting ratio of b:(100-b), where b is any number greater than 0 and less than 100.

[0015] Preferably, the splitting ratio of the first output end of the second optical device is b, and the splitting ratio of the second output end of the second optical device is 100-b.

[0016] Accordingly, the present invention also provides a monitoring method for monitoring the stimulated Brillouin scattering effect of an optical system as described in any of the above claims, the method comprising the following steps:

[0017] S10 provides an optical system and generates signal light through a narrow-linewidth seed source;

[0018] S20, the signal light is input to the laser amplifier through the first optical device for narrow linewidth laser amplification, and the stimulated Brillouin scattering light generated by the laser amplifier is exported to the backlight monitoring module through the first optical device;

[0019] The S30 uses a backlight monitoring module to detect the backlight power and spectral composition of stimulated Brillouin scattering light in real time.

[0020] Preferably, the backlight monitoring module includes a second optical device, a power meter, a laser attenuator, and a spectrometer. The input terminal of the second optical device is connected to the second input terminal of the first optical device, the first output terminal of the second optical device is connected to the power meter, the second output terminal of the second optical device is connected to the input terminal of the laser attenuator, and the output terminal of the laser attenuator is connected to the spectrometer.

[0021] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides an optical system and method for monitoring stimulated Brillouin scattering (SBS). The optical system first uses a first optical device to transmit a narrow-linewidth seed source to a laser amplifier for narrow-linewidth laser amplification. The stimulated Brillouin scattering light generated by the laser amplifier is then exported to a backlight monitoring module. This backlight monitoring module detects the backlight power and spectral composition of the stimulated Brillouin scattering light in real time, thereby achieving the simultaneous and accurate measurement of the stimulated Brillouin scattering light power and observation of the laser composition, which is more conducive to determining whether the stimulated Brillouin scattering effect has occurred. Furthermore, by adjusting the spectral splitting ratio of the first optical device and the backlight monitoring module, the optical system can maximize the protection of the narrow-linewidth seed source and the spectrometer in the backlight monitoring module from damage caused by backlight, achieving the purpose of accurately determining the stimulated Brillouin scattering effect and protecting system safety. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the optical system for monitoring stimulated Brillouin scattering provided in an embodiment of the present invention;

[0023] Figure 2 This is a flowchart of a monitoring method for monitoring stimulated Brillouin scattering provided in an embodiment of the present invention;

[0024] In the attached diagram: 1000 - Optical system; 101 - Narrow linewidth seed source; 102 - First optical device; 103 - Laser amplifier; 20 - Backlight monitoring module; 201 - Second optical device; 202 - Power meter; 203 - Laser attenuator; 204 - Spectrometer. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] The purpose of this invention is to address the shortcomings of existing technologies by providing an optical system 1000 and a detection method for monitoring stimulated Brillouin scattering (SBS). This invention aims to solve the technical problems of existing SBS monitoring systems, such as limited monitoring capabilities, low security, poor reliability, and system complexity, and ultimately improve the efficiency of SBS monitoring.

[0027] Please see Figure 1 , Figure 1This is a schematic diagram of the overall structure of an optical system 1000 for monitoring stimulated Brillouin scattering provided in an embodiment of the present invention. Specifically, the optical system 1000 for monitoring stimulated Brillouin scattering includes a narrow linewidth seed source 101, a first optical device 102, a laser amplifier 103, and a backlight monitoring module 20. The first input terminal of the first optical device 102 is connected to the output terminal of the narrow linewidth seed source 101, the second input terminal of the first optical device 102 is connected to the input terminal of the backlight monitoring module 20, and the first output terminal of the first optical device 102 is connected to the input terminal of the laser amplifier 103.

[0028] The first optical device 102 is used to deliver the narrow linewidth seed source 101 to the laser amplifier 103 for narrow linewidth laser amplification, and to export the stimulated Brillouin scattering light generated by the laser amplifier 103 to the backlight monitoring module 20; the backlight monitoring module 20 is used to detect the backlight power and spectral composition of the stimulated Brillouin scattering light in real time.

[0029] In this embodiment of the invention, the narrow linewidth seed source 101 outputs linearly polarized laser or non-linearly polarized laser. The narrow linewidth seed source 101 is structured as a linear cavity oscillator or a ring cavity oscillator. The operating band of the narrow linewidth seed source 101 includes the 1.0µm band, the 1.5µm band, or the 2.0µm band. The linewidth of the narrow linewidth seed source 101 is less than 0.1nm.

[0030] In this embodiment of the invention, the first optical device 102 includes any one of a 2×2 first coupler with a splitting ratio of a:(100-a), a three-port isolator, and a circulator, where a is any number greater than 0 and less than 100.

[0031] Specifically, the 2×2 first coupler with a:(100-a) is a common passive fiber optic device with two inputs and two outputs. It can distribute the optical signal entering from one of the inputs to the two outputs according to a set splitting ratio. The value of 'a' can be determined by the overall parameters of the optical system 1000; the function of the 2×2 first coupler with a splitting ratio of a:(100-a) is to guide the backlight (mainly stimulated Brillouin scattering light) of the optical system 1000 from the laser amplifier 103 to the backlight monitoring module 20, both to protect the entire optical system 1000 from backlight damage and to better monitor the backlight.

[0032] Preferably, when the first optical device 102 is a 2×2 first coupler, the splitting ratio of the first input terminal of the first optical device 102 is a, the splitting ratio of the second input terminal of the first optical device 102 is 100-a, the splitting ratio of the first output terminal of the first optical device 102 is a, and the splitting ratio of the second output terminal of the first optical device 102 is 100-a; at this time, the second output terminal of the first optical device 102 can be used as a monitoring port for the laser power and spectral stability of the narrow linewidth seed source 101.

[0033] In this embodiment of the invention, the laser amplifier 103 is a linearly polarized laser amplification structure or a non-linearly polarized laser amplification structure, and the pumping structure of the laser amplifier 103 is any one of a forward pumping structure, a reverse pumping structure, or a dual-end pumping structure.

[0034] The laser amplifier 103 is used to amplify the signal light output from the narrow linewidth seed source 101. As the power increases during the narrow linewidth laser amplification process, stimulated Brillouin scattering will occur in the laser amplifier 103, generating stimulated Brillouin scattered light. Its transmission direction is opposite to the laser transmission direction, so it is sometimes referred to as backlight for the sake of convenience. At this time, the output end of the laser amplifier 103 serves as the final output port of the amplified laser.

[0035] In this embodiment of the invention, the backlight monitoring module 20 is used to detect the backlight power and spectral composition of stimulated Brillouin scattering light in real time. The backlight monitoring module 20 includes a second optical device 201, a power meter 202, a laser attenuator 203, and a spectrometer 204. The input terminal of the second optical device 201 is connected to the second input terminal of the first optical device 102, the first output terminal of the second optical device 201 is connected to the power meter 202, the second output terminal of the second optical device 201 is connected to the input terminal of the laser attenuator 203, and the output terminal of the laser attenuator 203 is connected to the spectrometer 204.

[0036] In this embodiment of the invention, the main function of the second optical device 201 is to perform spectral processing on the received return light and finally send it to the power meter 202 and the spectrometer 204 for detection. The power meter 202 serves as a partial stimulated Brillouin scattering light power measurement port, and the spectrometer 204 serves as a stimulated Brillouin scattering light component monitoring port.

[0037] Specifically, the second optical device 201 includes a 1×2 second coupler with a splitting ratio of b:(100-b), where b is any number greater than 0 and less than 100, and the value of b can be jointly determined by the measurement accuracy of the power meter 202 and the spectrometer 204; preferably, the splitting ratio of the first output end of the second optical device 201 is b, and the splitting ratio of the second output end of the second optical device 201 is 100-b.

[0038] In this embodiment of the invention, the intensity of the stimulated Brillouin scattering light returned from the laser amplifier 103 may be high, while the spectrometer 204 has a specific light intensity tolerance range. The laser attenuator 203 can reduce the light intensity, preventing excessively strong light signals from entering the spectrometer 204 and causing damage. Simultaneously, different spectrometers 204 have different optimal measurement light intensity ranges. The laser attenuator 203 can regulate the light intensity to a range that the spectrometer 204 can accurately measure. If the light intensity exceeds the measurement range of the spectrometer 204, it may lead to inaccurate spectral measurement results, saturation, or distortion. By attenuating the light intensity, the spectrometer 204 can accurately measure and analyze the spectral components of the stimulated Brillouin scattering light. Furthermore, before the light signal enters the spectrometer 204, the laser attenuator 203 can reduce noise and interference in the light signal. When the light intensity is too high, it may be accompanied by noise generated by nonlinear effects; attenuating the light intensity helps reduce the impact of this noise on spectral measurements, thereby improving the accuracy and reliability of the measurement.

[0039] In this embodiment of the invention, the connection between the narrow linewidth seed source 101, the first optical device 102 and the laser amplifier 103 is achieved by fusion splicing using a fiber optic fusion splicer; the connection between the first optical device 102, the second optical device, the power meter 202, the laser attenuator 203 and the spectrometer 204 is achieved by fusion splicing using a fiber optic fusion splicer or by connecting with fiber optic connectors.

[0040] Accordingly, please refer to Figure 2 The present invention also provides a monitoring method for monitoring the stimulated Brillouin scattering effect of an optical system 1000 as described in any of the preceding claims, the method comprising the following steps:

[0041] S10 provides an optical system 1000 and generates signal light through a narrow linewidth seed source 101;

[0042] S20, the signal light is input to the laser amplifier 103 through the first optical device 102 for narrow linewidth laser amplification, and the stimulated Brillouin scattering light generated by the laser amplifier 103 is exported to the backlight monitoring module 20 through the first optical device 102.

[0043] S30 uses the backlight monitoring module 20 to detect the backlight power and spectral composition of stimulated Brillouin scattering light in real time.

[0044] Specifically, the backlight monitoring module 20 includes a second optical device 201, a power meter 202, a laser attenuator 203, and a spectrometer 204. The input terminal of the second optical device 201 is connected to the second input terminal of the first optical device 102, the first output terminal of the second optical device 201 is connected to the power meter 202, the second output terminal of the second optical device 201 is connected to the input terminal of the laser attenuator 203, and the output terminal of the laser attenuator 203 is connected to the spectrometer 204.

[0045] In this embodiment of the invention, the first optical device 102 is a 2×2 first coupler with a splitting ratio of a:(100-a), and the second optical device 201 is a 1×2 second coupler with a splitting ratio of b:(100-b); wherein, the specific process of the above monitoring method is as follows:

[0046] (1) A signal light is generated by a narrow linewidth seed source 101 and input to the input end of a 2×2 first coupler with a split ratio of a:(100-a). The signal light enters the laser amplifier 103 for narrow linewidth laser amplification through the output end of the 2×2 first coupler with a split ratio of a:(100-a). The amplified signal light is output through the output end of the laser amplifier 103. At this time, the output end of the 2×2 first coupler with a split ratio of a:(100-a) with a split ratio of (100-a) serves as the laser power and spectral stability monitoring port of the narrow linewidth seed source 101.

[0047] (2) As the power increases during the narrow linewidth laser amplification process, stimulated Brillouin scattering will occur in the laser amplifier 103, generating stimulated Brillouin scattered light. Its transmission direction is opposite to the laser transmission direction, so it is sometimes referred to as backlight for the convenience of description.

[0048] (3) The backlight enters the output of the 2×2 first coupler with a split ratio of a:(100-a) from the input of the laser amplifier 103. The backlight enters the input of the split ratio of a and the input of the split ratio of (100-a) in the 2×2 first coupler with a split ratio of a:(100-a) according to the ratio.

[0049] (4) The returned light enters the input end of the 1×2 second coupler with a split ratio of (100-a) from the input end of the 2×2 first coupler with a split ratio of a:(100-a) and a split ratio of (100-a); at this time, the returned light enters the output end of the 1×2 second coupler (4) with a split ratio of b and the output end of the split ratio of (100-b) respectively in proportion;

[0050] (5) Part of the backlight enters the power meter 202 from the output end of the 1×2 second coupler with a split ratio of b:(100-b) for power measurement. The backlight power can be accurately calculated based on the split ratio of each stage. At the same time, the remaining backlight enters the laser attenuator 203 and the spectrometer 204 step by step from the output end of the 1×2 second coupler with a split ratio of b:(100-b) for measurement of the backlight components. The spectrometer 204 can directly observe the stimulated Brillouin scattering light and the random pulse light components caused by the stimulated Brillouin scattering light. Combining the backlight power and spectral components, it is possible to accurately determine online whether the stimulated Brillouin scattering effect has occurred and protect the safety of the entire optical system 1000.

[0051] Furthermore, the monitoring method provided by the present invention can control the proportion of reflected light entering the narrow linewidth seed source 101 by adjusting the spectral ratio in the 2×2 first coupler with a spectral ratio of a:(100-a), so as to protect the narrow linewidth seed source 101 from damage caused by reflected light generated in the laser amplifier 103; the monitoring method provided by the present invention can also control the proportion of reflected light entering the spectrometer 204 by adjusting the spectral ratio in the 1×2 second coupler with a spectral ratio of b:(100-b), so as to protect the spectrometer 204 from damage caused by reflected light generated in the laser amplifier 103.

[0052] The technical solution of the present invention will now be described in conjunction with specific embodiments.

[0053] Example 1:

[0054] Please see Figure 1 This embodiment 1 first provides an optical system 1000 for monitoring stimulated Brillouin scattering effect, including: a narrow linewidth seed source 101, a 2×2 first coupler with a splitting ratio of a:(100-a), a laser amplifier 103, a 1×2 second coupler with a splitting ratio of b:(100-b), a power meter 202, a laser attenuator 203, and a spectrometer 204.

[0055] The output of the narrow linewidth seed source 101 is connected to the input of the 2×2 first coupler with a splitting ratio of a:(100-a). The output of the 2×2 first coupler with a splitting ratio of a:(100-a) is connected to the input of the laser amplifier 103. The output of the laser amplifier 103 serves as the final output port of the laser.

[0056] Specifically, the input terminal of the 2×2 first coupler with a split ratio of (100-a) and a split ratio of (100-a) is connected to the input terminal of the 1×2 second coupler with a split ratio of (100-b); the output terminal of the 2×2 first coupler with a split ratio of (100-a) and a split ratio of (100-a) serves as the monitoring port of the narrow linewidth seed source 101.

[0057] Specifically, the output terminal of the 1×2 second coupler with a splitting ratio of b:(100-b) is connected to the power meter 202; the power meter 202 serves as a port for measuring the power of partially stimulated Brillouin scattering light; the output terminal of the 1×2 second coupler with a splitting ratio of b:(100-b) is connected to the input terminal of the laser attenuator 203; the output terminal of the laser attenuator 203 is connected to the spectrometer 204; the spectrometer 204 serves as a port for monitoring the composition of stimulated Brillouin scattering light.

[0058] In this embodiment 1, the narrow linewidth seed source 101 is a linearly polarized laser output, with a linear cavity structure, a working wavelength of 1064nm, and a linewidth of 0.1419nm.

[0059] In this embodiment 1, the 2×2 first coupler with a splitting ratio of a:(100-a) has a splitting ratio a of 90, and the 1×2 second coupler with a splitting ratio of b:(100-b) has a splitting ratio b of 90.

[0060] In this embodiment 1, the laser amplifier 103 is a single reverse pump structure.

[0061] In this embodiment 1, the narrow linewidth seed source 101, the 2×2 first coupler with a splitting ratio of 90:10, the laser amplifier 103, and the 1×2 second coupler with a splitting ratio of 90:10 are all connected by fusion splicing using a fiber optic fusion splicer; the 1×2 second coupler with a splitting ratio of 90:10, the power meter 202, the laser attenuator 203, and the spectrometer 204 are all connected by fiber optic connectors.

[0062] Specifically, the specific process of the monitoring method for stimulated Brillouin scattering light provided in this embodiment 1 is as follows:

[0063] (1) A 1064nm signal light is generated by a narrow linewidth seed source 101 and input to the input end of a 2×2 first coupler with a split ratio of 90:10. The signal light enters the laser amplifier 103 for narrow linewidth laser amplification through the output end of the 2×2 first coupler with a split ratio of 90:10. The amplified signal light is output through the output end of the laser amplifier 103. At this time, the output end of the 2×2 first coupler with a split ratio of 10 is used as the laser power and spectral stability monitoring port of the narrow linewidth seed source 101.

[0064] (2) Since the laser amplifier 103 adopts a single reverse pumping structure, as the power increases during the narrow linewidth laser amplification process, the stimulated Brillouin scattering effect will occur in the laser amplifier 103, generating stimulated Brillouin scattered light. Its transmission direction is opposite to the laser transmission direction, so it is sometimes called backlight for the convenience of description.

[0065] (3) The return light enters the output end of the 2×2 first coupler with a split ratio of 90 from the input end of the laser amplifier 103. The return light enters the input end with a split ratio of 90 and the input end with a split ratio of 10 in the 2×2 first coupler with a split ratio of 90:10 according to the ratio.

[0066] (4) The returned light enters the input end of the 1×2 second coupler with a split ratio of 90:10 from the input end of the 2×2 first coupler with a split ratio of 90:10; at this time, the returned light enters the output end of the 1×2 second coupler with a split ratio of 90 and the output end of the split ratio of 10 respectively in proportion.

[0067] (5) 90% of the backlight enters the power meter 202 from the output end of the 1×2 second coupler with a split ratio of 90:10 for power measurement. The backlight power can be accurately calculated according to the split ratio of each stage. At the same time, 10% of the backlight enters the laser attenuator 203 and the spectrometer 204 step by step from the output end of the 1×2 second coupler with a split ratio of 10 for the determination of the backlight components.

[0068] (6) When the laser output power is amplified to 1800W, the backlight power is 16mW. According to the calculation of one ten-thousandth of the laser output power, the stimulated Brillouin scattering threshold is reached at this time. At the same time, it is observed from the spectrometer 204 that as the laser output power is increased to 1800W, the stimulated Brillouin scattering light gradually covers the signal light component, but no random pulses caused by the stimulated Brillouin scattering effect appear. When the laser output power is further increased to 1850W, the backlight power reaches 17mW, which exceeds the threshold of the stimulated Brillouin scattering effect. At the same time, random pulses caused by the stimulated Brillouin scattering effect are observed from the spectrometer 204. The position of the random pulses on the spectrum is not fixed, and they gradually change with time. They become denser and more intense as the laser output power increases.

[0069] Therefore, the experimental results of this embodiment 1 accurately show the changes in backlight power and backlight composition during the occurrence of stimulated Brillouin scattering, thereby achieving the purpose of online monitoring of stimulated Brillouin scattering.

[0070] This invention, in an optical system 1000 with a narrow-linewidth seed source 101, uses a second optical device 201 and a laser attenuator 203 to introduce stimulated Brillouin scattering light into a power meter 202 and a spectrometer 204 for online monitoring. This achieves the goal of simultaneously and accurately measuring the power of stimulated Brillouin scattering light and observing the laser composition, which is more conducive to determining whether the stimulated Brillouin scattering effect has occurred. Furthermore, by adjusting the splitting ratio of the first coupler and the second coupler, the narrow-linewidth fiber laser seed source and the spectrometer 204 can be protected from damage by backlight to the greatest extent, achieving the goal of accurately determining the stimulated Brillouin scattering effect and protecting system safety.

[0071] The optical system 1000 and monitoring method for monitoring stimulated Brillouin scattering provided by this invention have the following advantages, as they differ from existing technologies:

[0072] This invention employs a second coupler and a laser attenuator 203 to introduce stimulated Brillouin scattering light into a power meter 202 and a spectrometer 204 for online monitoring. This method simultaneously achieves accurate measurement of return light power and observation of laser components. It avoids the problem of a surge in return light power due to system variations when monitoring only the return light power, which can affect the assessment of the stimulated Brillouin scattering effect. It also avoids the damage to the spectrometer 204 caused by a surge in return light when monitoring only the laser components. Furthermore, this invention can also introduce the return light into the photodetector by adding a splitting port to the second coupler or by splitting the light again after the second coupler has finished, simultaneously monitoring the temporal stability of the return light to determine if random pulses associated with the stimulated Brillouin scattering effect are generated. This method offers advantages such as simple operation, compact structure, affordable price, and high reliability. In summary, this invention, by employing a backlight monitoring module 20 to introduce stimulated Brillouin scattering light into the power meter 202 and spectrometer 204 for online monitoring, can simultaneously and accurately measure backlight power and observe laser components, making it more advantageous for determining whether the stimulated Brillouin scattering effect has occurred. It has advantages such as ease of operation, simple structure, high safety, and high reliability.

[0073] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0074] The above embodiments merely illustrate implementation methods 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. An optical system for monitoring stimulated Brillouin scattering, characterized in that, It includes a narrow linewidth seed source, a first optical device, a laser amplifier, and a backlight monitoring module. The first input terminal of the first optical device is connected to the output terminal of the narrow linewidth seed source, the second input terminal of the first optical device is connected to the input terminal of the backlight monitoring module, and the first output terminal of the first optical device is connected to the input terminal of the laser amplifier. The first optical device is used to deliver the narrow-linewidth seed source to the laser amplifier for narrow-linewidth laser amplification and to guide the stimulated Brillouin scattering light generated by the laser amplifier to the backlight monitoring module. The backlight monitoring module is used to detect the backlight power and spectral composition of the stimulated Brillouin scattering light in real time. The backlight monitoring module includes a second optical device, a power meter, a laser attenuator, and a spectrometer. The input terminal of the second optical device is connected to the second input terminal of the first optical device, the first output terminal of the second optical device is connected to the power meter, the second output terminal of the second optical device is connected to the input terminal of the laser attenuator, and the output terminal of the laser attenuator is connected to the spectrometer. The second optical device includes a 1×2 second coupler with a splitting ratio of b:(100-b), where b is any number greater than 0 and less than 100. The first optical device includes a 2×2 first coupler with a splitting ratio of a:(100-a), where a is any number greater than 0 and less than 100. The splitting ratio of the first input terminal of the first optical device is a, the splitting ratio of the second input terminal of the first optical device is 100-a, the splitting ratio of the first output terminal of the first optical device is a, and the splitting ratio of the second output terminal of the first optical device is 100-a. Specifically, the proportion of reflected light entering the narrow linewidth seed source is controlled by adjusting the spectral ratio in the 2×2 first coupler with a spectral ratio of a:(100-a), thus protecting the narrow linewidth seed source from damage caused by reflected light generated in the laser amplifier; the proportion of reflected light entering the spectrometer is controlled by adjusting the spectral ratio in the 1×2 second coupler with a spectral ratio of b:(100-b), thus protecting the spectrometer from damage caused by reflected light generated in the laser amplifier.

2. The optical system for monitoring stimulated Brillouin scattering according to claim 1, characterized in that, The narrow linewidth seed source outputs linearly polarized laser or non-linearly polarized laser. The narrow linewidth seed source has a structure of a linear cavity oscillator or a ring cavity oscillator. The operating wavelength of the narrow linewidth seed source is 1.0µm, 1.5µm, or 2.0µm. The linewidth of the narrow linewidth seed source is less than 0.1nm.

3. The optical system for monitoring stimulated Brillouin scattering according to claim 1, characterized in that, The laser amplifier is a linearly polarized laser amplification structure or a non-linearly polarized laser amplification structure, and the pumping structure of the laser amplifier is any one of a forward pumping structure, a reverse pumping structure, or a dual-ended pumping structure.

4. The optical system for monitoring stimulated Brillouin scattering according to claim 1, characterized in that, The splitting ratio of the first output terminal of the second optical device is b, and the splitting ratio of the second output terminal of the second optical device is 100-b.

5. A monitoring method for monitoring the stimulated Brillouin scattering effect of an optical system as described in any one of claims 1 to 4, characterized in that, The method includes the following steps: S10, providing the optical system and generating signal light through the narrow linewidth seed source; S20, the signal light is input to the laser amplifier for narrow linewidth laser amplification through the first optical device, and the stimulated Brillouin scattering light generated by the laser amplifier is exported to the backlight monitoring module through the first optical device; S30, the backlight monitoring module detects the backlight power and spectral composition of the stimulated Brillouin scattering light in real time.

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