Optical fiber laser for low-reflection light splitting monitoring

Abstract

The utility model provides a low-reflection light-splitting monitoring fiber laser which comprises a fiber amplifier, a light-splitting isolation assembly, an output head and a photoelectric detector. The light splitting isolation assembly comprises a double-fiber collimator, a two-stage isolator and a single-fiber collimator which are sequentially arranged in the direction of a main light path, the double-fiber collimator comprises a first optical fiber, a second optical fiber, a first capillary tube and a first lens, and the fiber core end of the first optical fiber and the output end face of the first capillary tube form a first beam expanding length; the fiber core end of the second optical fiber and the input end face of the second capillary tube form a second beam expanding length, the input end of the first optical fiber is connected with the optical fiber amplifier, the output end face of the first lens faces the input end of the two-stage isolator, the output end face of the first lens is plated with an anti-reflection film, and the output end of the second optical fiber is connected with the photoelectric detector. According to the scheme, the optical path is more concise, a device optical fiber coupler is saved, more space is reserved, and the integration level of the laser module is higher.

Description

Technical Field

[0001] The utility model relates to the field of optical devices, in particular to a low-reflection spectroscopic monitoring optical fiber laser. Background Art

[0002] With the rapid development of LiDAR, smaller fiber lasers have become the preferred light source for LiDAR due to their simple structure, high efficiency, stable and reliable performance, and low cost. Of course, different types of fiber lasers are also widely used in different fields. Since the application scenarios of LiDAR involve people, high-intensity lasers pose a safety hazard to the human eye. Therefore, the output intensity of the laser must be monitored in real time, and the monitoring accuracy must be high, and it cannot drift with environmental conditions and time.

[0003] Reference Figure 1 In the existing design, a coupler for splitting is generally connected to the output end of the double-stage isolator, and a small part of the laser output energy is split into a photodetector for power monitoring using a 1X2 coupler, while most of the laser energy continues to be output.

[0004] Since the laser light source configured by the laser radar is often a short high-peak laser pulse, the separated laser must be a very small part (about -50dB) to avoid exceeding the linear range of the photodetector, so it is often necessary to use two-stage splitting to achieve it, such as one stage is 0.1%, and the other stage is 1% to achieve the purpose of overall -50dB attenuation, or use attenuation plates to achieve light attenuation to meet the requirements. Therefore, the existing design scheme structure is relatively complex, the optical path link is long, the monitoring accuracy is poor, and the adjustment response speed needs to be further improved. Utility Model Content

[0005] The utility model aims to provide a low-reflection spectral monitoring optical fiber laser.

[0006] In order to achieve the purpose of the utility model, the utility model provides a low-reflection spectroscopic monitoring fiber laser, including a fiber amplifier, a spectroscopic isolation component, an output head and a photodetector; the spectroscopic isolation component includes a dual-fiber collimator, a double-stage isolator and a single-fiber collimator arranged in sequence along the main optical path direction, the dual-fiber collimator includes a first optical fiber, a second optical fiber, a first capillary and a first lens, the output end face of the first capillary is inclined relative to the input end face of the first lens, the first capillary is penetrated by a first capillary hole and a second capillary hole, the core of the first optical fiber penetrates the first capillary hole, the core end of the first optical fiber and the output end face of the first capillary form a first beam expansion length, the core of the second optical fiber penetrates the first capillary hole, The single-fiber collimator comprises a third optical fiber, a second capillary tube and a second lens. The core end of the second optical fiber and the input end face of the second capillary tube form a second beam expansion length. The input end of the first optical fiber is connected to the optical fiber amplifier. The output end face of the first lens faces the input end of the double-stage isolator. An anti-reflection film is coated on the output end face of the first lens. The film reflectivity of the anti-reflection film is less than or equal to 0.25%. The output end of the second optical fiber is connected to the photodetector. The single-fiber collimator comprises a third optical fiber, a second capillary tube and a second lens. The output end of the double-stage isolator faces the input end face of the second lens. The core of the third optical fiber penetrates into the third capillary hole of the second capillary tube. The core end of the third optical fiber is opposite to the output end face of the second lens. The output end of the third optical fiber is connected to the output head.

[0007] A further solution is that the double-stage isolator includes a magnetic ring and an optical rotation component located inside the magnetic ring, the optical rotation component includes a first birefringent crystal, a first optical rotation crystal, a second birefringent crystal, a third birefringent crystal, a second optical rotation crystal and a fourth birefringent crystal arranged in sequence along the optical path; the input end of the double-stage isolator is located on the first birefringent crystal, and the output end of the double-stage isolator is located on the fourth birefringent crystal.

[0008] A further solution is that the dual-fiber collimator comprises a first sleeve, and the output end face of the first capillary and the input end face of the first lens are fixedly assembled in the first sleeve.

[0009] A further solution is that the dual-fiber collimator includes a second sleeve, and a portion of the first capillary is fixedly assembled in the second sleeve.

[0010] A further solution is that the first lens is a self-focusing lens.

[0011] A further solution is that the first beam expansion length is smaller than the second beam expansion length.

[0012] A further solution is that the core end of the first optical fiber is melted and fixed in the first capillary hole.

[0013] A further solution is that the core end of the second optical fiber is melted and fixed in the second capillary hole.

[0014] The beneficial effect of the utility model is that, by adjusting the length difference between the first beam expansion length and the second beam expansion length, and cooperating with adjusting the reflectivity of the film layer of the anti-reflection film, most of the signal light is transmitted through the double-stage isolator and output outwardly using the output head, while a very small part of the split light enters the second optical fiber through reflection coupling, so that the reflected light of the second optical fiber can be continuously adjusted under different attenuation ratios, and then the adjustment control of the optical fiber laser can be realized through the monitoring of the photoelectric detector. In addition, the optical path of this case is simpler, the device optical fiber coupler is saved, more space is left, and the integration of the laser module is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of a conventional fiber laser.

[0016] Figure 2 It is a structural diagram of an embodiment of the fiber laser of the utility model.

[0017] Figure 3 It is a structural diagram of the optical splitting isolation component in the embodiment of the optical fiber laser of the utility model.

[0018] Figure 4 It is a structural diagram of a dual-fiber collimator in an embodiment of the optical fiber laser of the utility model.

[0019] Figure 5 It is a structural diagram of a double-stage isolator in an embodiment of the optical fiber laser of the utility model.

[0020] Figure 6 It is a structural diagram of a single fiber collimator in an embodiment of the optical fiber laser of the utility model.

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0022] Reference Figures 2 to 6 The fiber laser includes a fiber amplifier 11, a splitter isolation component 2, an output head 12 and a photodetector 13. The splitter isolation component 2 includes a dual-fiber collimator 21, a double-stage isolator 22 and a single-fiber collimator 23. The fiber amplifier 11, the dual-fiber collimator 21, the double-stage isolator 22, the single-fiber collimator 23 and the output head 12 are connected and arranged in sequence from left to right along the main optical path.

[0023] The dual-fiber collimator 21 includes a first sleeve 215, a second sleeve 213, a first optical fiber 211, a second optical fiber 212, a first capillary 214 and a first lens 216. The output end face of the first capillary 214 is inclined to face the input end face of the first lens 216. The first capillary 214 is provided with a first capillary hole and a second capillary hole. The core of the first optical fiber 211 penetrates the first capillary hole. The core end 217 of the first optical fiber 211 and the output end face of the first capillary 214 form a first beam expansion length L1. The core of the second optical fiber 212 penetrates the second capillary hole. The core end 218 of the second optical fiber 212 and the input end face of the second capillary 233 form a second beam expansion length L2. The core end 217 of the first optical fiber 211 is molten and fixed in the first capillary hole. The core end 218 of the second optical fiber 212 is molten and fixed in the second capillary hole.

[0024] The input end of the first optical fiber 211 is connected to the optical fiber amplifier 11, the first lens 216 is a self-focusing lens, the output end face of the first lens 216 faces the input end of the double-stage isolator 22, the output end face of the first lens 216 is plated with an anti-reflection film 219, and the film reflectivity of the anti-reflection film 219 is less than or equal to 0.25%, and the output end of the second optical fiber 212 is connected to the photodetector 13. The output end face of the first capillary 214 and the input end face of the first lens 216 are fixedly assembled in the first sleeve 215, and part of the first capillary 214 is fixedly assembled in the second sleeve 213.

[0025] The double-stage isolator 22 includes a magnetic ring 221 and an optical rotation component located in the magnetic ring 221. The optical rotation component includes a first birefringent crystal 222, a first optical rotation crystal 223, a second birefringent crystal 224, a third birefringent crystal 225, a second optical rotation crystal 226 and a fourth birefringent crystal 227 arranged in sequence along the main optical path. The input end of the double-stage isolator 22 is located on the first birefringent crystal 222, the output end face of the first lens 216 faces the first birefringent crystal 222, and the output end of the double-stage isolator 22 is located on the fourth birefringent crystal 227.

[0026] The single-fiber collimator 23 includes a third sleeve 232, a third optical fiber 234, a second capillary 233, and a second lens 231. The output end of the double-stage isolator 22, i.e., the fourth birefringent crystal 227, faces the input end face of the second lens 231. The core of the third optical fiber 234 penetrates into the third capillary hole of the second capillary 233. The core end of the third optical fiber 234 is opposite to the output end face of the second lens 231. The output end of the third optical fiber 234 is connected to the output head 12. The second capillary 233 and the second lens 231 are fixedly assembled in the third sleeve 232. The double-fiber collimator 21, the double-stage isolator 22, and the single-fiber collimator 23 are all fixedly assembled in the fixed sleeve 24.

[0027] The signal light is amplified by the optical fiber amplifier 11 (EDFA) and then input into the first optical fiber 211. By adjusting the length difference between the first beam expansion length L2 and the first beam expansion length L1, the first beam expansion length L1 is smaller than the second beam expansion length L2, and adjusting the reflectivity of the anti-reflection film 219, different attenuation ratios are obtained, which can be continuously adjustable within 20dB-60dB. The attenuation formula is as follows:

[0028]

[0029] Where λ is the wavelength of the laser, △L is the length of the second beam expansion length L2 minus the first beam expansion length L1, n is the refractive index of the beam expansion fiber, and MFD is the mode field diameter of the fiber. AR is the reflectivity of the anti-reflection film of the G lens, which is generally less than or equal to 0.25%. By increasing △L, the attenuation can be increased, and by reducing △L, the attenuation can also be reduced.

[0030] After the signal light is output from the fiber core end 217, it begins to expand, and then passes through the anti-reflection film 219 for transmission and reflection. Most of the light is collimated and transmitted out of the anti-reflection film 219 and input into the double-stage isolator 22. As a very small part of the split light is reflected, it is then coupled into the second optical fiber 212, and can then be monitored by the photodetector 13, and the optical signal can be converted into an electrical signal.

[0031] The dual-fiber collimator 21 can tap 0.1% (i.e. 30 dB), and the photodetector can integrate a 1% (20 dB) transmission attenuation plate (or high reflection plate), which can achieve 50 dB attenuation power monitoring. The dual-fiber collimator 21 can also tap 0.001% (i.e. 50 dB), and the photodetector has no attenuation, which can also achieve 50 dB attenuation power monitoring.

[0032] The forward transmission of the laser light is achieved through the double-stage isolator 22 , and the reverse light is isolated, and the transmitted signal light is output from the third optical fiber 234 using the output head 12 .

[0033] As can be seen from the above, this case utilizes the difference in length between the first beam expansion length and the second beam expansion length, and cooperates with adjusting the reflectivity of the anti-reflection film. Most of the signal light is transmitted through the double-stage isolator and then output outward using the output head, while a very small part of the split light enters the second optical fiber through reflection coupling. Therefore, the reflected light of the second optical fiber can be continuously adjusted at different attenuation ratios, and then the adjustment and control of the optical fiber laser can be realized through monitoring by the photoelectric detector. In addition, the optical path of this case is simpler, which saves the device optical fiber coupler, leaves more space, and the integration of the laser module is higher.

Claims

1. A low-reflection spectral monitoring fiber laser, characterized in that: It includes a fiber amplifier, a light splitting isolation component, an output head and a photoelectric detector; The optical splitting and isolation component includes a dual-fiber collimator, a double-stage isolator and a single-fiber collimator arranged in sequence along the main optical path direction, the dual-fiber collimator includes a first optical fiber, a second optical fiber, a first capillary and a first lens, and the single-fiber collimator includes a third optical fiber, a second capillary and a second lens; The output end face of the first capillary tube is inclined to the input end face of the first lens, the first capillary tube is penetrated by a first capillary hole and a second capillary hole, the core of the first optical fiber penetrates the first capillary hole, the core end of the first optical fiber and the output end face of the first capillary tube form a first beam expansion length, the core of the second optical fiber penetrates the second capillary hole, the core end of the second optical fiber and the input end face of the second capillary tube form a second beam expansion length, the input end of the first optical fiber is connected to the optical fiber amplifier, the output end face of the first lens faces the input end of the double-stage isolator, the output end face of the first lens is plated with an anti-reflection film, the film reflectivity of the anti-reflection film is less than or equal to 0.25%, and the output end of the second optical fiber is connected to the photodetector; The output end of the double-stage isolator faces the input end face of the second lens, the core of the third optical fiber penetrates into the third capillary hole of the second capillary, the core end of the third optical fiber is opposite to the output end face of the second lens, and the output end of the third optical fiber is connected to the output head.

2. The fiber laser according to claim 1, characterized in that: The double-stage isolator comprises a magnetic ring and an optical rotation component located in the magnetic ring, wherein the optical rotation component comprises a first birefringent crystal, a first optical rotation crystal, a second birefringent crystal, a third birefringent crystal, a second optical rotation crystal and a fourth birefringent crystal arranged in sequence along the optical path direction; The input end of the double-stage isolator is located on the first birefringent crystal, and the output end of the double-stage isolator is located on the fourth birefringent crystal.

3. The fiber laser according to claim 1, characterized in that: The dual-fiber collimator comprises a first sleeve, in which the output end face of the first capillary and the input end face of the first lens are fixedly assembled.

4. The optical fiber laser according to claim 3, characterized in that: The dual-fiber collimator comprises a second sleeve, and a portion of the first capillary is fixedly assembled in the second sleeve.

5. The fiber laser according to claim 1, characterized in that: The first lens is a self-focusing lens.

6. The optical fiber laser according to any one of claims 1 to 5, characterized in that: The first beam expansion length is smaller than the second beam expansion length.

7. The optical fiber laser according to claim 6, characterized in that: The core end of the first optical fiber is melted and fixed in the first capillary hole.

8. The fiber laser according to claim 6, characterized in that: The core end of the second optical fiber is melted and fixed in the second capillary hole.

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