Optical system for monitoring stimulated Brillouin scattering effect and monitoring method

Abstract

The invention provides an optical system and a monitoring method for monitoring a stimulated Brillouin scattering effect, and the optical system for monitoring the stimulated Brillouin scattering effect comprises the steps: firstly, conveying a narrow-linewidth seed source into a laser amplifier through a first optical device, and carrying out the narrow-linewidth laser amplification; and the stimulated Brillouin scattering light generated by the laser amplifier is guided out to the return light monitoring module, so that the return light power and the spectral component of the stimulated Brillouin scattering light are detected in real time through the return light monitoring module, and the purposes of simultaneously and accurately measuring the power of the stimulated Brillouin scattering light and observing the laser component are achieved. Whether the stimulated Brillouin scattering effect occurs or not can be judged more easily; furthermore, according to the optical system, the narrow-linewidth seed source and a spectrograph in the return light monitoring module can be protected from being damaged by return light to the maximum extent by adjusting the light splitting proportion of the first optical device and the return light monitoring module, and the purposes of accurately judging the stimulated Brillouin scattering effect and protecting system safety are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of narrow linewidth optical fiber lasers, and in particular to an optical system and a monitoring method for monitoring stimulated Brillouin scattering effects. Background Art

[0002] Narrow linewidth fiber lasers have a wide range of applications in gravitational wave detection, lidar, nonlinear frequency conversion, coherent beam combining, spectral beam combining and laser weapons. With the continuous increase in the output power of narrow linewidth fiber lasers, due to the small cross-sectional area of ​​the fiber core and the increase in the core energy density, when the output power reaches a certain level, it is easy to produce various nonlinear effects that limit the further improvement of its output performance. Among these nonlinear effects, the threshold power of the stimulated Brillouin scattering effect is relatively low, which is the main factor limiting the increase in the output power of narrow linewidth fiber lasers. When the output power is increased to a certain level, the amplified signal light is coupled to the reverse-transmitting stimulated Brillouin scattered light in large quantities, and randomly generates backward-transmitted self-pulses, whose peak power is much higher than the average power of the signal light, and is extremely destructive. It is particularly important to monitor the stimulated Brillouin scattering effect in a timely and accurate manner to protect the safety of narrow linewidth fiber laser systems.

[0003] There are four schemes for monitoring the stimulated Brillouin scattering effect in existing narrow-linewidth fiber laser systems: the first is to monitor the reverse return light power. When the reverse return light power exceeds one ten-thousandth of the output power (sometimes defined as one thousandth of the output power), the stimulated Brillouin scattering effect occurs, or the growth curve of the return light power with the output power is recorded. When the return light power shows an obvious nonlinear growth, it is determined that the stimulated Brillouin scattering effect occurs; the second is to use a spectrometer to collect the return light spectrum components. As the stimulated Brillouin scattering effect occurs and exceeds the threshold, stimulated Brillouin scattered light will first appear on the reverse spectrum, with a frequency shift of 10MHz relative to the signal light, and then around the stimulated Brillouin scattered light, the stimulated Brillouin scattered light will appear. Pulse peaks appear, the number gradually increases, and the spectral position appears randomly; the third is that the oscilloscope monitors the return light power intensity through a high-frequency photoelectric detector. The oscilloscope can directly observe high-frequency pulses. When high-frequency pulses appear, stimulated Brillouin scattering effect occurs; the fourth is that CN117490985A discloses an online monitoring method, system, equipment and medium for stimulated Brillouin scattering. This method obtains power data at different times in a set time period, reverse light power intensity and light intensity on the reverse light spectrum at the current moment, performs data model analysis on the three, and comprehensively judges the model to obtain the final probability of stimulated Brillouin scattering occurring at the current moment, thereby realizing online monitoring of stimulated Brillouin scattering.

[0004] Among the four methods currently available, the first method is simple and has low equipment requirements, but a single judgment is sometimes interfered by the laser system. For example, in addition to the stimulated Brillouin scattered light, there is also a certain amount of residual pump light in the return light. The residual pump light sometimes occupies most of the return light, and using one ten-thousandth of the output power may sometimes be biased; the second method is direct in observation and has obvious effects, but if the scattered light is collected, no obvious stimulated Brillouin scattered light can be observed, and the spectrum is distorted. If the return light is directly connected, the spectrometer will be damaged when the return light power is too high, and the system safety is not high; the third method has good time sensitivity, but it is easily affected by noise when used alone, and the pulse is easily submerged in the initial stage, making it difficult to judge in the first time, and the system reliability is poor; the fourth method has high reliability in detection results, but it has a complex structure and is not easy to be widely promoted and used.

[0005] Therefore, an optical system and a monitoring method for monitoring the stimulated Brillouin scattering effect are urgently needed to solve the above technical problems. Summary of the invention

[0006] The purpose of the present invention is to provide an optical system and a monitoring method for monitoring stimulated Brillouin scattering effect, so as to improve the technical problems of the existing system for monitoring stimulated Brillouin scattering effect, such as single monitoring, low safety, poor reliability and complex system.

[0007] In order to solve the above technical problems, the present invention first provides an optical system for monitoring stimulated Brillouin scattering effect, comprising a narrow linewidth seed source, a first optical device, a laser amplifier and a return light monitoring module, wherein a first input end of the first optical device is connected to an output end of the narrow linewidth seed source, a second input end of the first optical device is connected to an input end of the return light monitoring module, and a first output end of the first optical device is connected to an input end of the laser amplifier; Among them, the first optical device is used to transport the narrow linewidth seed source to the laser amplifier for narrow linewidth laser amplification, and to export the stimulated Brillouin scattered light generated by the laser amplifier to the return light monitoring module; the return light monitoring module is used to detect the return light power and spectral composition of the stimulated Brillouin scattered light in real time.

[0008] Preferably, the narrow linewidth seed source outputs linearly polarized laser or non-linearly polarized laser, the structure of the narrow linewidth seed source is a linear cavity oscillator or a ring cavity oscillator, the working band of the narrow linewidth seed source includes a 1.0µm band, a 1.5µm band or a 2.0µm band, and the linewidth of the narrow linewidth seed source is less than 0.1nm.

[0009] Preferably, the first optical device comprises any one of a 2×2 first coupler, a three-port isolator and a circulator with a splitting ratio of a:(100-a), where a is any number greater than 0 and less than 100.

[0010] Preferably, when the first optical device is a 2×2 first coupler, the splitting ratio of the first input end of the first optical device is a, the splitting ratio of the second input end of the first optical device is 100-a, the splitting ratio of the first output end of the first optical device is a, and the splitting ratio of the second output end of the first optical device is 100-a.

[0011] 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 double-end pumping structure.

[0012] Preferably, the return light monitoring module includes a second optical device, a power meter, a laser attenuator and a spectrometer, the input end of the second optical device is connected to the second input end of the first optical device, the first output end of the second optical device is connected to the power meter, the second output end of the second optical device is connected to the input end of the laser attenuator, and the output end of the laser attenuator is connected to the spectrometer.

[0013] Preferably, the second optical device comprises 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.

[0014] 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.

[0015] Accordingly, the present invention also provides a monitoring method for monitoring the stimulated Brillouin scattering effect of an optical system as described above, the method comprising the following steps: S10, providing an optical system and generating a signal light through a narrow linewidth seed source; S20, inputting the signal light into a laser amplifier through a first optical device for narrow linewidth laser amplification, and exporting stimulated Brillouin scattered light generated by the laser amplifier to a return light monitoring module through the first optical device; S30, detecting the return light power and spectral components of the stimulated Brillouin scattered light in real time through a return light monitoring module.

[0016] Preferably, the return light monitoring module includes a second optical device, a power meter, a laser attenuator and a spectrometer, the input end of the second optical device is connected to the second input end of the first optical device, the first output end of the second optical device is connected to the power meter, the second output end of the second optical device is connected to the input end of the laser attenuator, and the output end of the laser attenuator is connected to the spectrometer.

[0017] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides an optical system and a monitoring method for monitoring stimulated Brillouin scattering effect. The optical system for monitoring stimulated Brillouin scattering effect first transmits a narrow linewidth seed source to a laser amplifier through a first optical device for narrow linewidth laser amplification, and guides the stimulated Brillouin scattered light generated by the laser amplifier to a light return monitoring module, so as to detect the light return power and spectral components of the stimulated Brillouin scattered light in real time through the light return monitoring module, thereby achieving the purpose of simultaneously and accurately measuring the stimulated Brillouin scattered light power and observing the laser components, which is more conducive to judging whether the stimulated Brillouin scattering effect occurs; further, the optical system for monitoring stimulated Brillouin scattering effect can protect the narrow linewidth seed source and the spectrometer in the light return monitoring module from being damaged by the light return to the greatest extent by adjusting the splitting ratio of the first optical device and the light return monitoring module, thereby achieving the purpose of accurately judging the stimulated Brillouin scattering effect and protecting the safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the overall structure of an optical system for monitoring stimulated Brillouin scattering effect provided by an embodiment of the present invention; Figure 2 is a flow chart of a monitoring method for monitoring stimulated Brillouin scattering effect provided by an embodiment of the present invention; In the attached figure: 1000 - optical system; 101 - narrow line width seed source; 102 - first optical device; 103 - laser amplifier; 20 - return light monitoring module; 201 - second optical device; 202 - power meter; 203 - laser attenuator; 204 - spectrometer. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The purpose of the present invention is to address the defects of the prior art. The purpose of the present invention is to provide an optical system 1000 and a detection method for monitoring the stimulated Brillouin scattering effect, aiming to solve the technical problems of the existing system for monitoring the stimulated Brillouin scattering effect, such as single monitoring, low safety, poor reliability and complex system, and ultimately improve the efficiency of monitoring the stimulated Brillouin scattering effect.

[0021] See also Figure 1 , Figure 11 is a schematic diagram of the overall structure of an optical system 1000 for monitoring stimulated Brillouin scattering effect provided by an embodiment of the present invention; specifically, the optical system 1000 for monitoring stimulated Brillouin scattering effect comprises a narrow linewidth seed source 101, a first optical device 102, a laser amplifier 103 and a return light monitoring module 20, a first input end of the first optical device 102 is connected to an output end of the narrow linewidth seed source 101, a second input end of the first optical device 102 is connected to an input end of the return light monitoring module 20, and a first output end of the first optical device 102 is connected to an input end of the laser amplifier 103; Among them, the first optical device 102 is used to transport the narrow linewidth seed source 101 to the laser amplifier 103 for narrow linewidth laser amplification, and to export the stimulated Brillouin scattered light generated by the laser amplifier 103 to the return light monitoring module 20; the return light monitoring module 20 is used to detect the return light power and spectral components of the stimulated Brillouin scattered light in real time.

[0022] In an embodiment of the present invention, the narrow linewidth seed source 101 outputs linearly polarized laser or non-linearly polarized laser, the structure of the narrow linewidth seed source 101 is a linear cavity oscillator or a ring cavity oscillator, the working band of the narrow linewidth seed source 101 includes a 1.0µm band, a 1.5µm band or a 2.0µm band, and the linewidth of the narrow linewidth seed source 101 is less than 0.1nm.

[0023] In the embodiment of the present invention, the first optical device 102 includes any one of a 2×2 first coupler, a three-port isolator and a circulator with a splitting ratio of a:(100-a), where a is any number greater than 0 and less than 100.

[0024] Specifically, the 2×2 first coupler with a:(100-a) is a common fiber optical passive device with two input ends and two output ends. It can distribute the optical signal entering from one of the input ends to the two output ends according to the set splitting ratio. The size 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 export the return light (mainly stimulated Brillouin scattered light) of the optical system 1000 from the laser amplifier 103 to the return light monitoring module 20, both to protect the entire optical system 1000 from damage by the return light and to better monitor the return light.

[0025] Preferably, when the first optical device 102 is a 2×2 first coupler, the splitting ratio of the first input end of the first optical device 102 is a, the splitting ratio of the second input end of the first optical device 102 is 100-a, the splitting ratio of the first output end of the first optical device 102 is a, and the splitting ratio of the second output end of the first optical device 102 is 100-a; at this time, the second output end 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.

[0026] In the embodiment of the present 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 double-end pumping structure.

[0027] Among them, the laser amplifier 103 is used to perform laser amplification on the signal light output by the narrow linewidth seed source 101. As the power increases during the narrow linewidth laser amplification process, stimulated Brillouin scattering effect will occur in the laser amplifier 103 to generate stimulated Brillouin scattered light. Its transmission direction is opposite to the laser transmission direction, so it is sometimes called return light for the convenience of description; at this time, the output end of the laser amplifier 103 serves as the final output port of the amplified laser.

[0028] In the embodiment of the present invention, the light return monitoring module 20 is used to detect the light return power and spectral components of the stimulated Brillouin scattered light in real time. The light return monitoring module 20 includes a second optical device 201, a power meter 202, a laser attenuator 203 and a spectrometer 204. The input end of the second optical device 201 is connected to the second input end of the first optical device 102, the first output end of the second optical device 201 is connected to the power meter 202, the second output end of the second optical device 201 is connected to the input end of the laser attenuator 203, and the output end of the laser attenuator 203 is connected to the spectrometer 204.

[0029] In the embodiment of the present invention, the second optical device 201 mainly functions to perform spectroscopic processing on the received return light, and finally transmits it to the power meter 202 and the spectrometer 204 for detection respectively; the power meter 202 serves as a partial stimulated Brillouin scattered light power measurement port, and the spectrometer 204 serves as a stimulated Brillouin scattered light component monitoring port.

[0030] 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 size 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.

[0031] In the embodiment of the present invention, the intensity of the stimulated Brillouin scattered light returned from the laser amplifier 103 may be high, and the spectrometer 204 has a specific light intensity tolerance range. The laser attenuator 203 can reduce the intensity of the light to prevent the overly strong light signal from entering the spectrometer 204 and causing damage to it. At the same time, different spectrometers 204 have different optimal measurement light intensity ranges. The laser attenuator 203 can adjust 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 cause inaccurate spectral measurement results, saturation or distortion, etc. By attenuating the light intensity, the spectrometer 204 can accurately measure and analyze the spectral components of the stimulated Brillouin scattered light. In addition, before the light signal enters the spectrometer 204, the laser attenuator 203 can reduce the noise and interference in the light signal. When the light intensity is too high, it may be accompanied by some noise generated by nonlinear effects. Attenuating the light intensity helps to reduce the impact of these noises on the spectral measurement, thereby improving the accuracy and reliability of the measurement.

[0032] In the embodiment of the present invention, the narrow linewidth seed source 101, the first optical device 102 and the laser amplifier 103 are connected by fusion connection through a fiber fusion splicer; the first optical device 102, the second optical device, the power meter 202, the laser attenuator 203 and the spectrometer 204 are connected by fusion connection through a fiber fusion splicer or by connection with a fiber connector.

[0033] Accordingly, see Figure 2 The present invention also provides a monitoring method for monitoring the stimulated Brillouin scattering effect of the optical system 1000 as described above, the method comprising the following steps: S10, providing an optical system 1000, and generating signal light through a narrow linewidth seed source 101; S20, inputting the signal light into the laser amplifier 103 through the first optical device 102 for narrow line width laser amplification, and exporting the stimulated Brillouin scattered light generated by the laser amplifier 103 to the return light monitoring module 20 through the first optical device 102; S30, detecting the return light power and spectral components of the stimulated Brillouin scattered light in real time through the return light monitoring module 20.

[0034] Specifically, the return light monitoring module 20 includes a second optical device 201, a power meter 202, a laser attenuator 203 and a spectrometer 204. The input end of the second optical device 201 is connected to the second input end of the first optical device 102, the first output end of the second optical device 201 is connected to the power meter 202, the second output end of the second optical device 201 is connected to the input end of the laser attenuator 203, and the output end of the laser attenuator 203 is connected to the spectrometer 204.

[0035] In the embodiment of the present 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: (1) Generate signal light through the narrow linewidth seed source 101, and input the signal light to the input end with a splitting ratio of a of the 2×2 first coupler with a splitting ratio of a:(100-a), and the signal light enters the laser amplifier 103 through the output end with a splitting ratio of a of the 2×2 first coupler with a splitting ratio of a:(100-a) for narrow linewidth laser amplification, and the amplified signal light is output through the output end of the laser amplifier 103; at this time, the output end with a splitting ratio of (100-a) of the 2×2 first coupler with a splitting ratio of a:(100-a) serves as a monitoring port for laser power and spectral stability of the narrow linewidth seed source 101; (2) As the power of the narrow linewidth laser increases during amplification, stimulated Brillouin scattering effect occurs in the laser amplifier 103, generating stimulated Brillouin scattered light, which has a transmission direction opposite to the laser transmission direction. Therefore, it is sometimes referred to as return light for the convenience of description. (3) The return light enters the output end with a splitting ratio of a of the 2×2 first coupler with a splitting ratio of a:(100-a) from the input end of the laser amplifier 103. The return light enters the input end with a splitting ratio of a and the input end with a splitting ratio of (100-a) in the 2×2 first coupler with a splitting ratio of a:(100-a) in proportion. (4) The return light enters the input end of the 1×2 second coupler with a splitting ratio of b: (100-b) from the input end of the 2×2 first coupler with a splitting ratio of a: (100-a). At this time, the return light enters the output end of the 1×2 second coupler (4) with a splitting ratio of b: (100-b) and the output end of the 1×2 second coupler (4) with a splitting ratio of b: (100-b) in proportion. (5) Part of the return light enters the power meter 202 from the output end of the 1×2 second coupler with a splitting ratio of b:(100-b) for power measurement. The return light power can be accurately calculated according to the splitting ratios of each level. At the same time, the remaining return light enters the laser attenuator 203 and the spectrometer 204 step by step from the output end of the 1×2 second coupler with a splitting ratio of b:(100-b) for return light component measurement. The spectrometer 204 can directly observe the stimulated Brillouin scattered light and the random pulse light component caused by the stimulated Brillouin scattered light. Combining the return light power and the spectral component, it can be accurately determined online whether the stimulated Brillouin scattering effect occurs and protect the safety of the entire optical system 1000.

[0036] Furthermore, the monitoring method provided by the present invention can control the proportion of the return light entering the narrow linewidth seed source 101 by adjusting the splitting ratio in the 2×2 first coupler with a splitting ratio of a: (100-a), so as to protect the narrow linewidth seed source 101 from being damaged by the return light generated in the laser amplifier 103; the monitoring method provided by the present invention can also control the proportion of the return light entering the spectrometer 204 by adjusting the splitting ratio in the 1×2 second coupler with a splitting ratio of b: (100-b), so as to protect the spectrometer 204 from being damaged by the return light generated in the laser amplifier 103.

[0037] The technical solution of the present invention is now described in conjunction with specific embodiments.

[0038] Embodiment 1: See also Figure 1 In this embodiment 1, an optical system 1000 for monitoring stimulated Brillouin scattering effect is first provided, 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.

[0039] Among them, the output end of the narrow linewidth seed source 101 is connected to the input end of the 2×2 first coupler with a splitting ratio of a:(100-a) with a splitting ratio of a; the output end of the 2×2 first coupler with a splitting ratio of a:(100-a) with a splitting ratio of a is connected to the input end of the laser amplifier 103; the output end of the laser amplifier 103 serves as the final output port of the laser.

[0040] Specifically, the input end of the 2×2 first coupler with a splitting ratio of a: (100-a) and the input end of the 1×2 second coupler with a splitting ratio of b: (100-b) are connected; the output end of the 2×2 first coupler with a splitting ratio of a: (100-a) and the output end of the splitting ratio of (100-a) serves as the monitoring port of the narrow linewidth seed source 101.

[0041] Specifically, the output end with a splitting ratio of b 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 partial stimulated Brillouin scattered light power measurement port; the output end with a splitting ratio of (100-b) of the 1×2 second coupler with a splitting ratio of b:(100-b) is connected to the input end of the laser attenuator 203; the output end of the laser attenuator 203 is connected to the spectrometer 204; the spectrometer 204 serves as a stimulated Brillouin scattered light component monitoring port.

[0042] In the present embodiment 1, the narrow linewidth seed source 101 is a linearly polarized laser output, and its structure type is a linear cavity, with an operating wavelength of 1064 nm and a linewidth of 0.1419 nm.

[0043] In this embodiment 1, the splitting ratio a of the 2×2 first coupler with a splitting ratio of a:(100-a) is 90, and the splitting ratio b of the 1×2 second coupler with a splitting ratio of b:(100-b) is 90. In the first embodiment, the laser amplifier 103 is a single reverse pumping structure.

[0044] 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 connection through a fiber 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.

[0045] Specifically, the specific process of the monitoring method for stimulated Brillouin scattered light provided in this embodiment 1 is as follows: (1) Generate a 1064nm signal light through the narrow linewidth seed source 101, and input the signal light into the input end with a splitting ratio of 90 of the 2×2 first coupler with a splitting ratio of 90:10. The signal light enters the laser amplifier 103 through the output end with a splitting ratio of 90 of the 2×2 first coupler with a splitting ratio of 90:10 for narrow linewidth laser amplification. The amplified signal light is output through the output end of the laser amplifier 103. At this time, the output end with a splitting ratio of 10 of the 2×2 first coupler with a splitting ratio of 90:10 serves as a monitoring port for the laser power and spectral stability of the narrow linewidth seed source 101. (2) Since the laser amplifier 103 adopts a single reverse pump structure, as the power of the narrow linewidth laser increases during amplification, stimulated Brillouin scattering effect will occur in the laser amplifier 103, generating stimulated Brillouin scattered light, whose transmission direction is opposite to the laser transmission direction, and is sometimes referred to as return light for the convenience of description; (3) The return light enters the output end with a splitting ratio of 90 of the 2×2 first coupler with a splitting ratio of 90:10 from the input end of the laser amplifier 103. The return light enters the input end with a splitting ratio of 90 and the input end with a splitting ratio of 10 in the 2×2 first coupler with a splitting ratio of 90:10 respectively according to the proportion; (4) The return light enters the input end of the 1×2 second coupler with a splitting ratio of 90:10 from the input end of the 2×2 first coupler with a splitting ratio of 90:10 with a splitting ratio of 10; at this time, the return light enters the output end of the 1×2 second coupler with a splitting ratio of 90 and the output end of the splitting ratio of 10 in proportion; (5) 90% of the return light enters the power meter 202 from the output end with a splitting ratio of 90 of the 1×2 second coupler with a splitting ratio of 90:10 for power measurement. The return light power can be accurately calculated according to the splitting ratios at each level. At the same time, 10% of the return light enters the laser attenuator 203 and the spectrometer 204 step by step from the output end with a splitting ratio of 10 of the 1×2 second coupler with a splitting ratio of 90:10 for determination of the return light component.

[0046] (6) When the laser output power is amplified to 1800W, the return light power is 16mW. According to one ten-thousandth of the laser output power, it can be calculated that 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 increases to 1800W, the stimulated Brillouin scattered 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 return light power reaches 17mW, exceeding the stimulated Brillouin scattering threshold. 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, but gradually changes with time, and becomes dense and intense as the laser output power increases.

[0047] Therefore, the above experimental results of the present embodiment 1 accurately show the changes in the return light power and return light component during the stimulated Brillouin scattering effect, thereby achieving the purpose of online monitoring of the stimulated Brillouin scattering effect.

[0048] In the present invention, in an optical system 1000 having a narrow linewidth seed source 101, the stimulated Brillouin scattered light is introduced into a power meter 202 and a spectrometer 204 for online monitoring by using a second optical device 201 and a laser attenuator 203. This method achieves the purpose of simultaneously and accurately measuring the stimulated Brillouin scattered light power and observing the laser component, which is more conducive to judging whether the stimulated Brillouin scattering effect occurs; further, 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 the return light to the greatest extent, thereby achieving the purpose of accurately judging the stimulated Brillouin scattering effect and protecting the safety of the system.

[0049] Different from the prior art, the optical system 1000 for monitoring stimulated Brillouin scattering effect and the monitoring method provided by the present invention also have the following advantages: The present invention uses a second coupler and a laser attenuator 203 to introduce stimulated Brillouin scattered light into a power meter 202 and a spectrometer 204 for online monitoring. This method can simultaneously achieve the purpose of accurately measuring the return light power and observing the laser component; it avoids the situation that when the return light power is monitored alone, sometimes due to changes in the system, the residual pump light increases, resulting in a surge in the return light power, which affects the judgment of the stimulated Brillouin scattering effect; it also avoids the situation that when the laser component is monitored alone, the surge in the return light damages the spectrometer 204. The present invention can further introduce the return light into the photoelectric detector by adding a splitting port of the second coupler or performing splitting again after the second coupler splits the light, and monitors the time domain stability of the return light at the same time, and determines whether there is a random pulse generated accompanied by the stimulated Brillouin scattering effect, so as to monitor the stimulated Brillouin scattering effect. The invention has the advantages of simple operation, compact structure, affordable price and high reliability. In summary, the present invention uses the return light monitoring module 20 to introduce the stimulated Brillouin scattered light into the power meter 202 and the spectrometer 204 for online monitoring, which can simultaneously achieve the purpose of accurately measuring the return light power and observing the laser component, and is more conducive to judging whether the stimulated Brillouin scattering effect occurs. It has the advantages of easy operation, simple structure, high safety and reliability.

[0050] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0051] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An optical system for monitoring stimulated Brillouin scattering effect, characterized in that: It includes a narrow line width seed source, a first optical device, a laser amplifier and a return light monitoring module, wherein a first input end of the first optical device is connected to an output end of the narrow line width seed source, a second input end of the first optical device is connected to an input end of the return light monitoring module, and a first output end of the first optical device is connected to an input end of the laser amplifier; Among them, the first optical device is used to transport the narrow linewidth seed source to the laser amplifier for narrow linewidth laser amplification, and to export the stimulated Brillouin scattered light generated by the laser amplifier to the return light monitoring module; the return light monitoring module is used to detect the return light power and spectral components of the stimulated Brillouin scattered light in real time.

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

3. The optical system for monitoring stimulated Brillouin scattering effect according to claim 1, characterized in that: The first optical device includes any one of a 2×2 first coupler, a three-port isolator and a circulator with a splitting ratio of a:(100-a), where a is any number greater than 0 and less than 100.

4. The optical system for monitoring stimulated Brillouin scattering effect according to claim 3, characterized in that: When the first optical device is the 2×2 first coupler, the splitting ratio of the first input end of the first optical device is a, the splitting ratio of the second input end of the first optical device is 100-a, the splitting ratio of the first output end of the first optical device is a, and the splitting ratio of the second output end of the first optical device is 100-a.

5. The optical system for monitoring stimulated Brillouin scattering effect 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 double-end pumping structure.

6. The optical system for monitoring stimulated Brillouin scattering effect according to claim 1, characterized in that: The return light monitoring module includes a second optical device, a power meter, a laser attenuator and a spectrometer. The input end of the second optical device is connected to the second input end of the first optical device, the first output end of the second optical device is connected to the power meter, the second output end of the second optical device is connected to the input end of the laser attenuator, and the output end of the laser attenuator is connected to the spectrometer.

7. The optical system for monitoring stimulated Brillouin scattering effect according to claim 6, characterized in that: 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.

8. The optical system for monitoring stimulated Brillouin scattering effect according to claim 7, characterized in that: 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.

9. A monitoring method for monitoring the stimulated Brillouin scattering effect of an optical system according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S10, providing the optical system, and generating signal light through the narrow linewidth seed source; S20, inputting the signal light into the laser amplifier through the first optical device for narrow linewidth laser amplification, and exporting stimulated Brillouin scattered light generated by the laser amplifier to the return light monitoring module through the first optical device; S30, detecting the return light power and spectral components of the stimulated Brillouin scattered light in real time through the return light monitoring module.

10. The monitoring method according to claim 9, characterized in that: The return light monitoring module includes a second optical device, a power meter, a laser attenuator and a spectrometer. The input end of the second optical device is connected to the second input end of the first optical device, the first output end of the second optical device is connected to the power meter, the second output end of the second optical device is connected to the input end of the laser attenuator, and the output end of the laser attenuator is connected to the spectrometer.

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