Output isolator with Raman suppression function

Abstract

The utility model provides an output isolator with a Raman suppression function, which comprises a shell, an isolation module is packaged in the shell, one end of the isolation module is provided with an input optical fiber, and the input optical fiber extends out of the shell; the input optical fiber is provided with a fiber core and a wrapping layer wrapping the fiber core, a Raman suppression grating used for suppressing stimulated Raman scattering light is arranged on one section of the fiber core, an included angle which is not zero is formed between the Raman suppression grating and the axial direction of the fiber core, and the Raman suppression grating is not perpendicular to the axial direction of the fiber core. According to the utility model, the number of welding points of an optical fiber system can be reduced, system complexity is reduced, and optical signal transmission quality is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of optical communication devices, specifically, it is an output isolator with raman suppression function. BACKGROUND

[0002] With the development of optical communication technology, optical devices are widely used in optical fiber communication systems. Among them, the fiber laser has the advantages of high conversion efficiency, small size and good beam quality, especially the pulse laser has important applications in the fields of optical fiber communication, optical fiber sensing, industrial processing, biomedicine and so on. However, the pulse laser will produce nonlinear effects such as stimulated Raman scattering (SRS) during power amplification, which will cause pulse laser power loss and thermal effect, which is an important factor restricting the development of high-power pulse laser. The thermal effect caused by stimulated Raman scattering produces thermal birefringence and thermal lens effect in the output isolator, and the thermal birefringence will affect the Faraday effect of the crystal and reduce the isolation of the device, and the thermal lens effect will cause the wavefront distortion of the laser, affecting the quality of the output beam.

[0003] At present, the common way is to increase the fiber mode field area and reduce the effective length of the fiber to increase the stimulated Raman scattering threshold or increase the band-stop filter to filter out the stimulated Raman scattering light. If the mode field area of the fiber is increased, the problem is that as the core diameter increases, it is difficult for the laser to maintain single-mode output, and the beam quality will deteriorate; in addition, this method will cause the mode instability threshold of the fiber to decrease, thereby limiting the increase of the output power. If the effective length of the fiber is reduced, the absorption coefficient of the gain fiber is usually increased by increasing the doping concentration of rare earth ions to reduce the effective length of the fiber, but the increase of the doping concentration will cause the enhancement of the photon darkening effect in the gain fiber, which will affect the performance of the laser.

[0004] Another way is to use a long-period grating as a band-stop filter to suppress the generation of stimulated Raman scattering, but the long-period grating is sensitive to temperature, stress and other external factors, and its spectral characteristics are relatively unstable, which affects the filtering effect of stimulated Raman scattering.

[0005] The Chinese invention patent application with publication number CN111817119A discloses a fiber laser with anti-core Raman back light function, which adds a first Raman isolation unit and a second Raman isolation unit outside the fiber oscillator resonant cavity to filter out the core Raman back light. However, the first Raman isolation unit and the second Raman isolation unit of this scheme need to be fused with the laser input fiber and the laser output end cap input fiber before use, which will increase the number of fusion points of the fiber system, increase the complexity of the system, affect the stability of the system, and also affect the transmission quality of the optical signal. UTILITY MODEL CONTENT

[0006] The utility model discloses a kind of output isolators with Raman inhibition function, which can reduce the number of fusion points and reduce the complexity of system.

[0007] To achieve the above purpose, the utility model provides an output isolator with Raman inhibition function includes a shell, the shell is encapsulated with an isolation module, one end of the isolation module is provided with an input optical fiber, the input optical fiber extends to the outside of the shell;The input optical fiber has a core and a cladding layer wrapped outside the core, a section of the core is provided with a Raman suppression grating for suppressing stimulated Raman scattered light, the Raman suppression grating has a non-zero angle with the axial direction of the core, and the Raman suppression grating is not perpendicular to the axial direction of the core.

[0008] As can be seen from the above scheme, the Raman suppression grating is directly formed on the input optical fiber of the output isolator, so that the input optical fiber of the output isolator itself has the function of suppressing stimulated Raman scattered light, and there is no need to additionally fuse the optical fiber with the Raman suppression grating, so as not to increase the additional fusion points. Therefore, the utility model can suppress stimulated Raman scattering without increasing the fusion points and the complexity of the optical fiber system, can reduce the loss of laser power, improve the performance stability of the output isolator, and at the same time maintain good output beam quality.

[0009] One preferred scheme is that a collimator is arranged in the isolation module, and the input optical fiber is connected to one end of the collimator.

[0010] As can be seen from the above scheme, the light signal output from the input optical fiber is incident into the isolation module after passing through the collimator, improving the collimation of the light signal.

[0011] Further, the collimator has a collimating lens and a pigtail encapsulated in a glass tube, and the pigtail is arranged between the input optical fiber and the collimating lens.

[0012] As can be seen from the above scheme, the pigtail is used in the collimator to realize the signal transmission between the collimating lens and the input optical fiber, and the structure of the collimator is simple.

[0013] Further, the end of the input optical fiber is inserted into one end of the glass tube. In this way, the connection reliability of the input optical fiber and the glass tube can be ensured.

[0014] Further, the outer peripheral wall of the input optical fiber and the inner wall of the glass tube are fixed by an adhesive.

[0015] Further, a grating section is arranged in the input optical fiber, and the Raman suppression grating is arranged in the grating section. Preferably, the cladding layer of the grating section is a restructured cladding layer.

[0016] Therefore, the cladding layer outside the grating section is a reconstruction cladding layer, that is, when the Raman suppression grating is manufactured, the cladding layer of the grating section needs to be removed first, and then the cladding layer is reconstructed after the Raman suppression grating is formed, that is, the cladding layer is re-manufactured. This manufacturing process is easy to implement, reduces the manufacturing difficulty and manufacturing cost of the Raman suppression grating.

[0017] Further, the shell is provided with a fiber protection sleeve outside, and the grating section is arranged in the fiber protection sleeve. Preferably, the fiber protection sleeve is adjacent to the shell.

[0018] Therefore, the grating section is protected by the fiber protection sleeve, that is, the end of the fiber provided with the Raman suppression grating is protected, which can effectively protect the reconstruction cladding layer and effectively prolong the service life of the output isolator. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic view of an embodiment of the output isolator with Raman suppression function of the utility model.

[0020] Figure 2 is a structural schematic view of an input fiber in an embodiment of the output isolator with Raman suppression function of the utility model.

[0021] Figure 3 is a structural schematic view of a collimator in an embodiment of the output isolator with Raman suppression function of the utility model.

[0022] The utility model will be further described below in combination with the drawings and embodiments. DETAILED DESCRIPTION

[0023] The output isolator with Raman suppression function of the utility model sets the inclined Raman suppression grating on the core of the input fiber, reduces the number of fusion points of the whole fiber system through the integrated manufacturing mode, thereby reducing the complexity of the fiber system, reducing the production cost of the fiber system, and improving the optical signal transmission stability of the fiber system.

[0024] Referring to Figure 1 The output isolator with Raman suppression function of the embodiment includes a shell 30, an isolation module is integrated in the shell 30, the isolation module includes a plurality of optical devices, for example, includes Faraday rotator, birefringent crystal and other optical devices. An input fiber 10 is arranged on one side of the isolation module, one end of the input fiber 10 extends into the shell 30, and the other end extends from the shell 30 to the outside of the shell 30.

[0025] Referring to Figure 2The input optical fiber 10 has a core 11, and a cladding layer 13 is coated on the core 11. Preferably, the cross section of the core 11 is circular, the cross section of the cladding layer 13 is annular, and the cladding layer 13 wraps the core 11 in the circumferential direction. A grating section is arranged on the input optical fiber 10, and a Raman suppression grating 12 is arranged in the core 11 corresponding to the grating section. The Raman suppression grating 12 forms an oblique angle with the axial direction of the core 11, and the angle is not a right angle. Therefore, the Raman suppression grating 12 has a non-zero angle with the axial direction of the core 11, and the Raman suppression grating 12 is not perpendicular to the axial direction of the core 11. When the optical signal propagates in the core 11 in the direction indicated by the arrow of Figure 2 , the stimulated Raman scattering light is reflected by the Raman suppression grating 12 and enters the cladding layer 13, and the other optical signals continue to propagate through the Raman suppression grating 12. In this way, the stimulated Raman scattering light cannot basically pass through the Raman suppression grating 12, thereby achieving the function of suppressing the stimulated Raman scattering light.

[0026] The output isolator with the Raman suppression function of the embodiment further comprises a collimator, which can be packaged in the shell 30. Referring to Figure 3 , the collimator comprises a collimating lens 21, and a circular annular glass tube 20 is arranged, and a part of the collimating lens 21 is packaged in the glass tube 20. As can be seen from Figure 3 , the end face of the end of the collimating lens 21 exposed outside the glass tube 20 is an arc face. Preferably, the collimating lens 21 and the glass tube 20 are fixed by adhesive.

[0027] A part of the input optical fiber 10 is also packaged in the glass tube 20, and the input optical fiber 10 is also fixed in the glass tube 20 by the adhesive. Therefore, the outer peripheral wall of the input optical fiber 10 and the inner wall of the glass tube 20 are fixed by the adhesive, thereby achieving the fixed connection between the input optical fiber 10 and the glass tube 20.

[0028] A pigtail 22 is arranged between the input optical fiber 10 and the collimating lens 21. As can be seen from Figure 3 , the pigtail 22 is completely packaged in the glass tube 20, so that the pigtail 22 can be protected by the glass tube 20 to avoid damage to the pigtail 22.

[0029] The input optical fiber 10 of the output isolator of the embodiment directly forms the Raman suppression grating 12, thereby achieving the integration of the Raman suppression grating 12 and the output isolator. Compared with the existing solution that needs to be fused, the embodiment does not need to fuse the grating with the Raman suppression grating on the output isolator. Therefore, without increasing the fusion points and the complexity of the optical fiber system, the stimulated Raman scattering light can be effectively suppressed, the laser power loss is reduced, the performance stability of the output isolator is improved, and the output beam quality is maintained.

[0030] When the output isolator of the embodiment is manufactured, firstly, the wavelength of the stimulated Raman scattering light needs to be found. Specifically, the spectrum of the light signal of the output of the pulse laser is measured to determine the wavelength of the stimulated Raman scattering light, and the spectrum of the stimulated Raman scattering light is recorded. Moreover, a suitable mask plate is selected according to the spectrum of the stimulated Raman light.

[0031] Then, the Raman suppression grating 12 is arranged at a suitable position of the input optical fiber 10, and it is necessary to ensure that the Raman suppression grating 12 has a certain angle with the axial direction of the core 11 of the input optical fiber 10, so as to ensure that the Raman suppression grating 12 can reflect the stimulated Raman light in the core 11 to the cladding layer 13, thereby achieving the function of suppressing the stimulated Raman light.

[0032] Specifically, firstly, the cladding layer 13 of the fiber segment of the input optical fiber 10 where the Raman suppression grating 12 needs to be arranged is stripped, and the core 11 with the stripped cladding layer 13 is cleaned with anhydrous ethanol. Then, the input optical fiber 10 is placed on a fiber clamp, and the fiber clamp is kept in a stressed state so that the input optical fiber 10 is in a straightened state.

[0033] Then, the Raman suppression grating 12 is manufactured according to the pre-calculated tilt angle of the Raman suppression grating 12. When the tilt angle of the Raman suppression grating 12 is calculated, the tilt angle of the Raman suppression grating 12 is obtained by simulation calculation through the transfer matrix method according to the fiber type, reflectivity and other parameters of the input optical fiber 10.

[0034] Next, the phase mask plate is rotated in a plane perpendicular to the ultraviolet laser. In the embodiment, the Raman suppression grating 12 is manufactured by using low-power ultraviolet laser. During the manufacturing process, it is necessary to ensure that the input optical fiber 10 is located at the center of the optical axis of the ultraviolet laser. After the positioning of the input optical fiber 10 is completed, the focal point of the spot of the ultraviolet laser is adjusted so that the focal point of the spot is focused on the core 11 of the input optical fiber 10. Then, the ultraviolet laser is turned on to perform laser etching, and the Raman suppression grating 12 is obtained.

[0035] Finally, the cladding layer 13 needs to be re-manufactured on the grating segment to protect the Raman suppression grating 12 by the re-manufactured cladding layer 13. Therefore, the cladding layer 13 formed outside the grating segment is a restructured cladding layer.

[0036] After the Raman suppression grating 12 is manufactured, the collimator also needs to be packaged. The collimating lens 21 is packaged at one end of the glass tube 20, and the pigtail 22 is arranged in the glass tube 20. Then, one end of the input optical fiber 10 is fixed to the other end of the glass tube 20 by an adhesive, so as to realize the packaging of the collimator.

[0037] After the collimator is made, the collimator, the isolation module and the beam expander are packaged, for example, the collimator, the isolation module and the beam expander are packaged in the shell 30, and the one end of the input optical fiber 10 extends out of the shell 30. Figure 1 It can be seen that the optical fiber protection sleeve 31 is arranged outside the shell 30, and the grating section provided with the Raman suppression grating 12 is arranged in the optical fiber protection sleeve 31. Preferably, the optical fiber protection sleeve 31 is adjacent to the shell 30. In this way, the optical fiber protection sleeve 31 can protect the grating section, and avoid that the Raman suppression grating 12 is damaged due to the bending of the input optical fiber 10.

[0038] It can be seen that the Raman suppression grating 12 is directly formed on the input optical fiber 10 of the output isolator, so that the input optical fiber 10 of the output isolator itself has the function of suppressing the stimulated Raman scattered light, and it is not necessary to additionally fuse the optical fiber with the Raman suppression grating, and the additional fusion point is not increased. Therefore, the utility model can suppress the stimulated Raman scattering without increasing the fusion point and the complexity of the optical fiber system, can reduce the laser power loss, improve the performance stability of the output isolator, and maintain good output beam quality.

[0039] Finally, it needs to be emphasized that the above is only the preferred embodiment of the utility model, and is not used for limiting the utility model. For the person skilled in the art, the utility model can have various changes and modifications, and any modification, equivalent replacement, improvement and the like made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1.A output isolator with Raman suppression function, comprising: a housing, an isolator module is encapsulated in the housing, an input fiber is arranged at one end of the isolator module, and the input fiber extends out of the housing; characterized in that: the input fiber has a core and a cladding layer covering the core, a Raman suppression grating for suppressing stimulated Raman scattering light is arranged on a section of the core, the Raman suppression grating has a non-zero angle with the axial direction of the core, and the Raman suppression grating is not perpendicular to the axial direction of the core. 2.The output isolator with Raman suppression function according to claim 1, characterized in that: a collimator is arranged in the isolator module, and the input fiber is connected to one end of the collimator. 3.The output isolator with Raman suppression function according to claim 2, characterized in that: the collimator has a collimating lens and a pigtail encapsulated in a glass tube, and the pigtail is arranged between the input fiber and the collimating lens. 4.The output isolator with Raman suppression function according to claim 3, characterized in that: the end of the input fiber is inserted into one end of the glass tube. 5.The output isolator with Raman suppression function according to claim 4, characterized in that: the outer peripheral wall of the input fiber and the inner wall of the glass tube are fixed by an adhesive. 6.The output isolator with Raman suppression function according to any one of claims 1 to 5, characterized in that: a grating section is arranged in the input fiber, and the Raman suppression grating is arranged in the grating section. 7.The output isolator with Raman suppression function according to claim 6, characterized in that: the cladding layer of the grating section is a restructured cladding layer. 8.The output isolator with Raman suppression function according to claim 6, characterized in that: a fiber protection sleeve is arranged outside the housing, and the grating section is arranged in the fiber protection sleeve. 9.The output isolator with Raman suppression function according to claim 8, characterized in that: the fiber protection sleeve is adjacent to the housing.

Images