Elliptical core heart-shaped polarization maintaining optical fiber

Abstract

The application discloses a kind of elliptical core cardioid polarization maintaining optical fiber.The application composition includes: cladding, elliptical core, two stress zones drawn by cardioid R=c (1+cosθ), the elliptical core is located in the center of the cladding, two the stress zones are horizontally symmetrically placed about the elliptical core;The material of the cladding is silica;The material of the elliptical core is silica doped with 15%-20% concentration GeO2;The material of the cardioid stress zone is silica doped with 20%-30% concentration B2O3.The application increases geometric birefringence, improves the birefringence value of polarization maintaining optical fiber;Compared with the traditional stress type polarization maintaining optical fiber, the stress zone area of this structure is relatively small, reduces the sensitivity of stress birefringence to temperature, improves the polarization stability of optical fiber, and the stress zone structure is relatively simple, which is beneficial to actual preparation.

Description

Technical Field

[0001] This invention belongs to the field of polarization-maintaining optical fiber, specifically relating to an elliptical core cardioid polarization-maintaining optical fiber. Background Technology

[0002] Fiber optic gyroscopes are solid-state inertial devices widely used in aerospace and marine applications. The core component of a fiber optic gyroscope is the fiber optic loop, and overcoming the influence of external temperature loads on the gyroscope's output stability is a key research focus in the field.

[0003] Polarization-maintaining fibers used in fiber optic gyroscopes can be classified into geometric and stress-based types. Geometric polarization-maintaining fibers lack stress regions, thus exhibiting stronger stability under the influence of environmental factors such as temperature; their main drawback is a lower birefringence value. Stress-based polarization-maintaining fibers rely on stress regions with high thermal expansion coefficients to generate high stress birefringence, but this also makes them more susceptible to interference from environmental factors such as temperature during application, reducing the fiber's polarization-maintaining effect. Simply increasing the doping concentration and area of ​​the stress region to improve birefringence will increase the fiber's temperature sensitivity.

[0004] When optical fibers are subjected to external temperature disturbances, the coating material of the fiber also undergoes thermal expansion and contraction with temperature changes. This causes stress and compression between the inter-turn fibers, which in turn alters the refractive index of the fiber, affecting its polarization stability. Consequently, the stability and accuracy of the fiber optic sensor decrease under environmental disturbances such as temperature fluctuations. Summary of the Invention

[0005] The purpose of this invention is to provide an elliptical core cardioid polarization-maintaining fiber that, by introducing geometric birefringence and optimizing the stress region structure, improves the birefringence value of the polarization-maintaining fiber and reduces its sensitivity to environmental factors such as temperature with minimal stress region area.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] An elliptical core cardioid polarization-maintaining fiber includes: a cladding, an elliptical core, and two stress regions drawn by a cardioid line R = c(1 + cosθ). The elliptical core is located at the center of the cladding, and the two stress regions are horizontally symmetrical about the elliptical core.

[0008] Furthermore, the cladding material is silicon dioxide.

[0009] Furthermore, the elliptical fiber core material is silicon dioxide doped with 15%-20% GeO2.

[0010] Furthermore, the material of the heart-shaped stress region is silicon dioxide doped with 20%-30% B2O3.

[0011] Furthermore, with the distance d between the fixed elliptical fiber core and the cardioid stress region remaining constant, and the structural parameter value c of the cardioid stress region ranging from 4μm to 8μm, when the ratio e of the major semi-axis a to the minor semi-axis b of the elliptical fiber core is 1.3 to 1.5, its birefringence B ≥ 5.2 × 10⁻⁶. -4 .

[0012] Furthermore, the structural parameter value c of the heart-shaped stress region ranges from 4μm to 8μm, and its effective area ranges from 24πμm. 2 -96πμm 2 Compared to traditional panda-type polarization-maintaining fiber, its stress zone area is significantly reduced while maintaining the same birefringence value.

[0013] Furthermore, when the ratio of the major semi-axis a to the minor semi-axis b of the elliptical fiber core is e≥1.5 and c≥4.5μm, its birefringence value B≥5.85×10 -4 At this time, the area S of the stress zone sap >10πμm 2 .

[0014] Furthermore, the elliptical fiber core material is silicon dioxide doped with 20% GeO2.

[0015] Furthermore, the material of the heart-shaped stress region is silicon dioxide doped with 29% B2O3.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention improves the birefringence value of polarization-maintaining fiber by increasing geometric birefringence. Compared to traditional stress-type polarization-maintaining fiber, the stress region area of ​​this structure is relatively small, reducing the temperature sensitivity of stress birefringence and improving the polarization stability of the fiber. Furthermore, the stress region structure is relatively simple, which is beneficial for practical fabrication. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to understand the invention and do not constitute an improper limitation of the invention.

[0019] Appendix Figure 1 This is a schematic diagram of the cross-section of the elliptical core cardioid polarization-maintaining fiber involved in this invention.

[0020] Appendix Figure 2 This is a schematic diagram illustrating the variation of the modal birefringence value of the circular core-shaped polarization-maintaining fiber of the present invention with the stress region parameter value c.

[0021] Appendix Figure 3This is a graph showing the relationship between the modal birefringence value of the elliptical core cardioid polarization-maintaining fiber of the present invention and the stress region parameter value c.

[0022] Appendix Figure 4 This is a schematic diagram of the birefringence and stress zone area changes in Examples 2, 4, and 5 of the present invention.

[0023] Appendix Figure 5 The effective mode area A (μm) of Embodiment 4 of the present invention 2 The relationship between the fluctuation of elliptical fiber core parameters by ±5% and the wavelength.

[0024] Appendix Figure 6 The nonlinear coefficient γ(km) in Embodiment 4 of the present invention -1 W -1 The relationship between the fluctuation of elliptical fiber core parameters by ±5% and the wavelength. Detailed Implementation

[0025] The present invention will now be further described with reference to the accompanying drawings.

[0026] Example 1:

[0027] According to embodiments of the present invention, an elliptical core cardioid polarization-maintaining fiber is provided, such as... Figure 1 As shown: the cladding material is silicon dioxide, the elliptical core material is silicon dioxide doped with 20% GeO2, and the material of the two stress zones is silicon dioxide doped with 29% B2O3. The cladding diameter is W1 = 80 μm, the ellipticity of the elliptical core is e = a / b, the distance between the elliptical core and the stress zone is d = 2 μm, and the stress zone is drawn by a cardioid line R = c(1 + cosθ), with an area of ​​S = 1.5πc. 2 .

[0028] Example 2:

[0029] Based on the elliptical core cardioid polarization-maintaining fiber described in Example 1, with e = 1 and d = 2 μm, this is a traditional circular core cardioid polarization-maintaining fiber. Under different core radii, as the stress region parameter value c varies from 4 μm to 8 μm, the birefringence value ranges from 4.5 to 6.6 × 10⁻⁶. -4 Between these, its birefringence value is relatively high.

[0030] Appendix Figure 2 This is a schematic diagram illustrating the variation of birefringence value with stress region parameter value c under different values ​​of 'a' in this embodiment. It can be seen that, for the same value of 'a', the birefringence value increases with increasing stress region parameter value c, and when c = 4.5 μm, B ≥ 5.2 × 10⁻⁶. -4 .

[0031] Example 3:

[0032] Based on the elliptical core cardioid polarization-maintaining fiber described in Example 1, when a = 4 μm, d = 2 μm, and e = 1.3, it is an elliptical core cardioid polarization-maintaining fiber. During the variation of the stress region parameter value c from 4 μm to 8 μm, the birefringence value ranges from 5.2 to 7.044 × 10⁻⁶. -4 Between these, it exhibits high birefringence properties.

[0033] Example 4:

[0034] Based on the elliptical core cardioid polarization-maintaining fiber described in Example 1, when a = 4 μm, d = 2 μm, and e = 1.5, it is an elliptical core cardioid polarization-maintaining fiber. During the variation of the stress region parameter value c from 4 μm to 8 μm, the birefringence value ranges from 5.35 to 7.16 × 10⁻⁶. -4 Between these, it exhibits high birefringence properties.

[0035] Appendix Figure 3 This is a schematic diagram of the birefringence characteristics and stress region parameter value c of Examples 2, 3, and 4. As can be seen from the figure, compared with Example 2, Examples 3 and 4 of the present invention have significantly higher birefringence values. Moreover, at the same birefringence value, the stress region parameter value c of Examples 3 and 4 is smaller than that of Example 2, that is, the stress region area is reduced, the sensitivity to temperature is reduced, thereby improving the polarization temperature stability of the polarization-maintaining fiber caused by the stress region.

[0036] Appendix Figure 5 The effective mode area A (μm) of Example 4 2 The graph shows the relationship between the core structure parameters and the elliptical fiber parameters when the design values ​​fluctuate by ±5%. It can be seen from the graph that within the wavelength range of 1.53 μm to 1.62 μm, a ±5% change in the core structure parameters results in a ±4% change in the effective mode area. At a typical wavelength of 1.55 μm, the effective mode area ranges from 23.9 to 25.85 μm. 2 This demonstrates that the effective mode area of ​​the elliptical core cardioid polarization-maintaining fiber involved in this invention is suitable for sensing fibers. An excessively large effective mode area will increase bending loss and make the fiber susceptible to external interference. An appropriate mode area can ensure that energy propagates through the core region.

[0037] Appendix Figure 6 The nonlinear coefficient γ (km) of Example 4 -1 W -1 The graph shows the relationship between the elliptical fiber core parameters and the design values ​​when they fluctuate by ±5%. It can be seen from the graph that, within the wavelength range of 1.53 μm to 1.62 μm, a ±5% change in the core structure parameters results in a ±3.9% change in the effective mode area. (Based on the formula...) It can be seen that (where λ is the operating wavelength, and parameter n is the nonlinear refractive index coefficient of the material, which is related to the dopant concentration) the nonlinear coefficient (γ) km -1 W -1 Inversely proportional to the effective mode area A, a low effective area provides the high-density power required to make the nonlinear effect significant, which indirectly proves that the polarization-maintaining fiber with high birefringence and small stress region area involved in this invention has good practical fabrication feasibility.

[0038] Example 5:

[0039] Based on the elliptical core cardioid polarization-maintaining fiber described in Example 1, with e = 1 and d = 2 μm, and the radius of the circular stress region varying from 5.5 μm to 9 μm, Example 4 is a traditional circular core panda-type polarization-maintaining fiber with a birefringence value ranging from 3.0 to 4.6 × 10⁻⁶. -4 Between these, its birefringence value is relatively low.

[0040] Appendix Figure 4 This is a schematic diagram of the birefringence characteristics and stress zone area of ​​Examples 2, 4, and 5. As can be seen from the figure, compared with Example 5, Examples 2 and 4 of the present invention have significantly higher birefringence values, and with the same stress zone area, Examples 2 and 4 have higher birefringence values. When the birefringence values ​​of Examples 2, 4, and 5 are equal, the stress zone area of ​​Examples 2 and 4 of the present invention is much smaller than that of Example 5, thus achieving a higher birefringence value with a smaller stress zone area.

[0041] Preferably, when the birefringence value B≈5.6×10 -4 At that time, the stress region area S of the elliptical core cardioid polarization-maintaining fiber sap 37.5πμm 2 The stress region area S of traditional panda-type polarization-maintaining fiber sap 144πμm 2 Its stress zone area is reduced by 3 / 4 compared to traditional panda-type polarization-maintaining fiber.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An elliptical core heart-shaped polarization maintaining optical fiber, characterized by, Comprising: a cladding (1), an elliptical core (2) located in the center of the cladding (1), two stress regions (3) drawn by cardioid R=c(1+cosθ), the two stress regions (3) are horizontally symmetrically placed about the elliptical core (2).

2. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 1, characterized in that, The material of the cladding (1) is silica.

3. The elliptical core heart-shaped polarization maintaining optical fiber according to claim 1, characterized in that, The material of the elliptical core (2) is silica doped with 15%-20% concentration of GeO2.

4. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 1, characterized in that, The material of the cardioid stress region (3) is silica doped with 20%-30% concentration of B2O3.

5. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 1 or 2 or 3 or 4, characterized in that, The distance d between the fixed elliptical core (2) and the heart-shaped stress region (3) is constant, the structural parameter value c of the heart-shaped stress region (3) ranges from 4 μm to 8 μm, and when the ratio e of the long semi-axis a to the short semi-axis b of the elliptical core (2) ranges from 1.3 to 1.5, the birefringence B is greater than or equal to 5.2*10 -4 .

6. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 5, characterized in that, The structural parameter value c of the heart-shaped stress region (3) ranges from 4 μm to 8 μm, and the effective area of the stress region ranges from 24πμm 2 to 96πμm 2 Compared with the conventional panda polarization maintaining optical fiber, the area of the stress region is greatly reduced under the same birefringence value.

7. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 1 or 3, characterized by When the ratio e of the long semi-axis a to the short semi-axis b of the elliptical core (2) is e≥1.5, c≥4.5μm, the birefringence value B≥5.85×10 -4 At this time, the stress area S sap >10πμm 2 .

8. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 3, characterized in that, The material of the elliptical core (2) is silica doped with 20% concentration of GeO2.

9. The elliptical-core heart-shaped polarization maintaining optical fiber according to claim 4, characterized in that, The material of the cardioid stress region (3) is silica doped with 29% concentration of B2O3.

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