阅读说明：本技术 一种抗辐射保偏光纤 (Anti-radiation polarization maintaining optical fiber ) 是由 杨坤 曹蓓蓓 熊伟 胡小龙 郑伟 杨晨 张心贲 汪松 童维军 于 2020-05-08 设计创作，主要内容包括：本发明涉及一种抗辐射保偏光纤,包括有芯层和包层,在包层内芯层的两侧对称设置应力层,其特征在于所述的芯层直径D1为4.0～7.0μm,相对折射率差Δ1％为-0.1％～-0.3％,所述的应力层直径D2为15.0～25.0μm,相对折射率差Δ3％为-0.6％～-1.0％,所述的包层相对折射率差Δ2％为-0.2％～-0.5％。本发明通过芯层、包层深掺氟改变保偏光纤的波导结构和材料成分使得本发明不仅具有优异的偏振保持性能,而且可以保证在1550nm等工作波段在一定的辐照剂量下,附加衰减显著降低,小于或等于0.5dB/100m,很好的满足了光纤陀螺外太空等场合抗辐射性能要求。(The invention relates to a radiation-resistant polarization-maintaining optical fiber, which comprises a core layer and a cladding, wherein stress layers are symmetrically arranged on two sides of the core layer in the cladding, and the radiation-resistant polarization-maintaining optical fiber is characterized in that the diameter D1 of the core layer is 4.0-7.0 mu m, the relative refractive index difference delta 1% is-0.1% -0.3%, the diameter D2 of the stress layer is 15.0-25.0 mu m, the relative refractive index difference delta 3% is-0.6% -1.0%, and the relative refractive index difference delta 2% of the cladding is-0.2% -0.5%. The invention changes the waveguide structure and material components of the polarization maintaining fiber by deeply doping fluorine in the core layer and the cladding layer, so that the polarization maintaining fiber has excellent polarization maintaining performance, can ensure that the additional attenuation is obviously reduced to be less than or equal to 0.5dB/100m under a certain irradiation dose in working wave bands of 1550nm and the like, and well meets the radiation resistance requirement of occasions such as outer space and the like of the fiber optic gyroscope.)

1. The anti-radiation polarization-maintaining fiber comprises a core layer and a cladding, wherein stress layers are symmetrically arranged on two sides of the core layer in the cladding, and is characterized in that the diameter D1 of the core layer is 4.0-7.0 mu m, the relative refractive index difference delta 1% is-0.1% -0.3%, the diameter D2 of the stress layer is 15.0-25.0 mu m, the relative refractive index difference delta 3% is-0.6% -1.0%, and the relative refractive index difference delta 2% of the cladding is-0.2% -0.5%.

2. The radiation-resistant polarization-maintaining fiber of claim 1, wherein said core layer is fluorine-doped silica, said stress layer is a boron-doped silica layer, and said cladding layer is a fluorine-doped silica layer.

3. The radiation-resistant polarization-maintaining fiber of claim 1 or 2, wherein the cladding diameter D3 is 50.0 to 90.0 μm.

4. The radiation-resistant polarization-maintaining fiber of claim 3, wherein the ratio of the stress layer spacing L to the cladding diameter D3 is 0.2 to 0.5.

5. The radiation-resistant polarization maintaining fiber of claim 1 or 2, wherein the relative refractive index difference is the refractive index difference of each of the core, cladding and stress layers relative to pure silica.

6. The radiation-resistant polarization maintaining optical fiber of claim 1 or 2, wherein the cladding is coated with a radiation-resistant coating, the radiation-resistant coating comprises an inner coating and an outer coating from inside to outside, the difference D5-D4 between the diameter D4 of the inner coating and the diameter D5 of the outer coating is 10.0-30.0 μm, and the diameter D5 of the outer coating is 160-170 μm.

7. The radiation-resistant polarization-maintaining fiber of claim 1 or 2, wherein said polarization-maintaining fiber has a mode birefringence not less than 3.0 × 10^-4。

8. The radiation-resistant polarization-maintaining fiber of claim 1 or 2, wherein the additional attenuation of said polarization-maintaining fiber after irradiation at a dose rate of 0.1Gy/s and a total dose of 5000Gy is less than or equal to 0.5dB/100 m.

9. A radiation-resistant polarization maintaining optical fiber according to claim 1 or 2, wherein the refractive index profile of the core, cladding and stress layer is stepped.

10. The radiation-resistant polarization-maintaining fiber of claim 6, wherein said polarization-maintaining fiber has a screening strength of greater than or equal to 100 kpsi.

Technical Field

The invention relates to an anti-radiation polarization maintaining optical fiber, and belongs to the technical field of special optical fibers for optical fiber sensing.

Background

Polarization maintaining optical fibers are a class of specialty fibers. Polarization maintaining fibers, i.e., polarization maintaining fibers, are fibers that have the ability to maintain the linear polarization direction of transmitted light. The polarization maintaining optical fiber can be applied to a plurality of fields, such as multiplexing coherent communication, optical fiber gyroscopes, optical fiber hydrophones, polarization sensing and the like, and is a special optical fiber with wide application value.

Polarization maintaining optical fibers include geometric birefringence and stress birefringence polarization maintaining optical fibers. An example of a geometrically birefringent polarization maintaining fiber is an elliptical core polarization maintaining fiber, the core of which is elliptical, exploiting this geometrical asymmetry to produce the birefringent effect. The stress double refraction polarization maintaining fiber mainly comprises a butterfly junction type polarization maintaining fiber, a panda type polarization maintaining fiber and an elliptical cladding type polarization maintaining fiber. The optical fiber is characterized in that a stress layer with high expansion coefficient is introduced into a cladding of the optical fiber to extrude a fiber core to generate a birefringence effect.

The structure of the panda-type polarization maintaining fiber comprises a fiber core, a stress layer and a cladding part, wherein the fiber core is positioned in the central part of the cladding, and two cylindrical stress layers are distributed on two sides of the fiber core. The core is typically germanium-fluorine co-doped silica glass, the stress layer is typically boron-doped silica glass, and the cladding is typically a pure silica glass material. Since boron quartz has a larger thermal expansion property than pure quartz, the stress layer can generate compressive stress to act on the fiber core part, so that the stress birefringence is generated to enable the polarization-maintaining fiber to have linear polarization maintaining performance.

The fiber optic gyroscope is an angular velocity fiber optic sensor based on an optical SAGNAC effect, and gradually replaces the traditional mechanical gyroscope after more than 20 years of development by the advantages of all solid state, no rotating part and friction part, long service life, large dynamic range, instant start, simple structure, small size, light weight and the like. Compared with a laser gyroscope, the fiber optic gyroscope has the advantages of no locking problem, simple assembly, low power consumption, high reliability and low cost. With the maturity of the fiber optic gyroscope technology, the precision of the fiber optic gyroscope can reach the requirement of an inertia level, and the requirement of controlling the satellite attitude is met. Radiation is the most dominant factor affecting many space applications. The fiber optic gyroscope and its optics are very reliable in a radiation environment, and the greatest effect is the additional loss of the polarization-maintaining fiber ring.

The satellite orbits in space, receives various radiations from space, including the electromagnetic radiation of the sun including rays, X-rays, ultraviolet rays, visible light, infrared rays, microwaves, radio waves and the like, and the particle radiation mainly includes high-energy charged particle radiation such as electrons, protons, α particles, heavy ions and the like from the earth radiation zone, the solar cosmic ray and the silver river cosmic ray.

Fiber optic gyroscopes and their optics are relatively reliable in a radiating environment, but the polarization maintaining fiber ring is the largest point of impact. The surface of the fiber optic gyroscope is coated with the radiation-resistant material, so that the radiation resistance of the fiber optic gyroscope can be improved, but the mass is increased. The weight requirements of the satellite are rather demanding, since every kilogram of weight of the satellite increases, several hundred kilograms of launching system are required. The most important part of the radiation influence of the fiber-optic gyroscope is the fiber-optic ring, so that the problem of radiation resistance of the optical fiber is solved, and the radiation resistance of the fiber-optic gyroscope is very important to be improved.

The existing polarization maintaining fiber is doped with Ge with higher concentration in a core layer, and Ge replaces Si in a [ SiO4] tetrahedron to cause the distortion of the tetrahedron, so that stress is generated in the fiber, and finally defects are formed. And the impurity atoms have strong electron affinity, and are easy to capture charges generated after irradiation to form color centers, and the color centers absorb light with specific wavelength to increase loss.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a radiation-resistant polarization-maintaining fiber with low additional attenuation at a certain irradiation dose in the 1550nm operating band, which overcomes the above-mentioned shortcomings of the prior art.

The technical scheme adopted by the invention for solving the problems is as follows: the multilayer composite material comprises a core layer and a cladding layer, wherein stress layers are symmetrically arranged on two sides of the core layer in the cladding layer, and the multilayer composite material is characterized in that the diameter D1 of the core layer is 4.0-7.0 mu m, the relative refractive index difference delta 1% is-0.1% -0.3%, the diameter D2 of the stress layer is 15.0-25.0 mu m, the relative refractive index difference delta 3% is-0.6% -1.0%, and the relative refractive index difference delta 2% of the cladding layer is-0.2% -0.5%.

According to the scheme, the core layer is fluorine-doped quartz, the stress layer is a boron-doped quartz layer, and the cladding layer is a fluorine-doped quartz layer.

According to the scheme, the diameter D3 of the cladding is 50.0-90.0 μm.

According to the scheme, the ratio of the stress layer spacing L symmetrically arranged on two sides to the cladding diameter D3 is 0.2-0.5.

According to the scheme, the relative refractive index difference is the refractive index difference of each core, each bag and each stress layer relative to pure silicon dioxide.

According to the scheme, the outer side of the cladding is coated with the anti-radiation coating layer, the anti-radiation coating layer sequentially comprises an inner coating layer and an outer coating layer from inside to outside, the difference D5-D4 between the diameter D4 of the inner coating layer and the diameter D5 of the outer coating layer is 10.0-30.0 mu m, and the diameter D5 of the outer coating layer is 160-170 mu m; the radiation-resistant coating layer can resist the temperature of more than or equal to-60 ℃ and less than or equal to 150 ℃.

According to the scheme, the mode birefringence index of the polarization maintaining optical fiber is not less than 3.0 × 10^-4。

According to the scheme, the additional attenuation of the polarization maintaining optical fiber after irradiation at the dose rate of 0.1Gy/s and the total dose of 5000Gy is less than or equal to 0.5dB/100 m.

According to the scheme, the refractive index profile structures of the core layer, the cladding layer and the stress layer are all step type profile structures.

According to the scheme, the screening strength of the polarization maintaining optical fiber is greater than or equal to 100 kpsi.

The invention has the beneficial effects that: the waveguide structure and material components of the polarization maintaining fiber are changed by deeply doping fluorine into the core layer and the cladding layer, so that the polarization maintaining fiber has polarization maintaining performance, can ensure that the additional attenuation is obviously reduced to be less than or equal to 0.5dB/100m under a certain irradiation dose in working wave bands of 1550nm and the like, and well meets the radiation resistance requirement of occasions such as outer space of a fiber optic gyroscope and the like.

Drawings

FIG. 1 is a graph comparing radiation resistance of a conventional polarization maintaining fiber and a radiation-resistant polarization maintaining fiber.

Fig. 2 is a schematic view of a radial structure of a radiation-resistant polarization-maintaining fiber according to an embodiment of the present invention.

FIG. 3 is a refractive index profile of a radiation-resistant polarization maintaining fiber according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

With the intensive research on the radiation-resistant quartz glass and the quartz optical fiber, fluorine doping has proved to be the most important way to improve the radiation resistance of the quartz glass and the quartz optical fiber. F plays a role in breaking the net in the quartz glass network structure. As described above for the defect structure with higher energy in the quartz glass, since the Si-F bond is stronger than the Si-O bond, the introduction of F will increase the net breaking probability of the defect structure with higher energy state, i.e. it will help to reduce the three-membered ring and four-membered ring defects in the quartz glass. And as the F content increases, the defect concentration decreases. Therefore, the mechanism of the anti-radiation polarization maintaining fiber is that the waveguide structure (same cut-off wavelength, mode field diameter and intrinsic loss) which is the same as that of the common polarization maintaining fiber is achieved by deeply doping fluorine in the core layer and the cladding layer, and meanwhile, the anti-radiation polarization maintaining fiber has stronger anti-radiation performance.

As can be seen from FIG. 1, the difference between the radiation resistance of the polarization maintaining fiber after deep fluorine doping and the radiation resistance of the common polarization maintaining fiber is very large, the additional attenuation of the radiation resistant polarization maintaining fiber after a certain radiation dose (0.1Gy/s dose rate, 5000Gy total dose) is less than 0.5dB/100m, and the additional attenuation of the conventional polarization maintaining fiber after the same radiation dose is more than 20dB/100 m.

An embodiment of the invention is shown in fig. 2 and 3, and is a panda type polarization maintaining optical fiber, which comprises a core layer 1 and a cladding layer 2, wherein stress layers 3 are symmetrically arranged at intervals on two sides of a cladding inner core layer, the diameter of the core layer is D1, the relative refractive index difference is delta 1%, the diameter of the stress layer is D2, the relative refractive index difference is delta 3%, the distance between the stress layers symmetrically arranged on the two sides is L, the diameter of the cladding layer is D3, the relative refractive index difference is delta 2%, the core layer is fluorine-doped quartz, the stress layer is a boron-doped quartz layer, the cladding layer is a fluorine-doped quartz layer, the cross-sectional structures of the refractive indexes of the core layer, the cladding layer and the stress layer are step-type cross-sectional structures, the cladding layer is externally coated with a radiation resistant coating layer, the radiation resistant coating layer is an inner cladding layer 4 and an outer cladding layer 5 in sequence from inside to outside, the difference D5-D4 of the diameter of the inner cladding layer and the diameter D39 5 of the outer cladding layer is 10.0-30.0 μm, the temperature resistant coating is equal to 160-3660 ℃ radiation resistant intensity of the screening temperature resistant optical fiber is equal to 150 μm.

Examples of the three different parameters of the present invention are shown in tables 1-3.

TABLE 1

TABLE 2

Parameters of optical fiber	Example two parameters
		Cladding diameter D3/mum	79.9
Core diameter D1/. mu.m	5.7
		Core relative refractive index Δ 1/%)	-0.333
Relative refractive index of the cladding Δ 2/%)	-0.516
		Stress layer diameter D2/cladding diameter D3	0.25
Stress layer spacing L/cladding diameter D3	0.275
		Stress layer relative refractive index delta 3/%)	-1.0
Modal birefringence (× 10)-4)	3.8
		Optical fiber crosstalk/(dB, zero tension, 100m optical fiber)	-28
Additional attenuation (dB/100m, 0.1Gy/s dose rate, 5000Gy total dose)	0.433

TABLE 3

Parameters of optical fiber	Example three parameters
		Cladding diameter D3/mum	79.9
Core diameter D1/. mu.m	5.5
		Core relative refractive index Δ 1/%)	-0.277
Relative refractive index of the cladding Δ 2/%)	-0.455
		Stress layer diameter D2/cladding diameter D3	0.25
Stress layer spacing L/cladding diameter D3	0.275
		Stress layer relative refractive index delta 3/%)	-1.0
Modal birefringence (× 10)-4)	3.8
		Optical fiber crosstalk/(dB, zero tension, 100m optical fiber)	-28
Additional attenuation (dB/100m, 0.1Gy/s dose rate, 5000Gy total dose)	0.469