A high-birefringence microstructure optical fiber

Abstract

The present invention belongs to the technical field of microstructure optical fibers, and discloses a highly birefringent microstructure optical fiber. The cross-section of the optical fiber is circular. The optical fiber sequentially includes a core, a holey cladding, and a silica cladding from the inside to the outside. The number of layers of the holey cladding is at least two. A plurality of holes in each layer of the holey cladding are centrosymmetric with the center of the cross-section of the optical fiber as the center. The first layer of the holey cladding is composed of two large holes and six small holes, and is arranged in a rectangular lattice. The remaining layers of the holey cladding are composed of several small holes, and are arranged in a rectangular lattice and exhibit four-fold rotational symmetry. The microstructure optical fiber provided by the present invention has a relatively high birefringence effect, and has a simple structure and is easy to fabricate.

Description

Technical Field

[0001] The present invention belongs to the technical field of microstructure optical fibers, and more specifically, relates to a highly birefringent microstructure optical fiber. Background Art

[0002] Since the concept of microstructure optical fiber was proposed by Russell et al. in 1992, with the continuous in-depth research, due to the flexibility of the microstructure optical fiber structure, the microstructure optical fiber has been developed by leaps and bounds. In 2000, Blanch et al. from the University of Bath in the UK first made the world's first polarization-maintaining microstructure optical fiber, achieving high birefringence by introducing asymmetry into the air holes in the cladding. The birefringence value of this optical fiber is as high as 3.7×10 -3 -3. High birefringence is one of the important characteristics of microstructure optical fibers, and higher birefringence performance can be obtained by flexibly designing the photonic crystal structure, including changing the cladding or core structure. In addition, compared with traditional polarization-maintaining optical fibers that require doping and applying stress to achieve birefringence, the polarization-maintaining microstructure optical fiber can have a single material, flexible structure design, good temperature stability, and a large single-mode working wavelength range.

[0003] In recent years, people have utilized the advantage of large design freedom to design various polarization-maintaining microstructure optical fibers that are superior to traditional polarization-maintaining optical fibers in both birefringence effect and resistance to environmental changes. How to improve the birefringence effect of microstructure optical fibers to meet the application requirements is an important research topic in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide a highly birefringent microstructure optical fiber, so that the microstructure optical fiber has a higher birefringence effect.

[0005] The present invention provides a highly birefringent microstructure optical fiber. The cross-section of the optical fiber is circular. The optical fiber from the inside to the outside is successively a core, a pore cladding, and a quartz cladding. The number of layers of the pore cladding is at least two layers. In each layer of the pore cladding, a plurality of pores are centrosymmetric with the center of the cross-section of the optical fiber as the center. The first layer of the pore cladding is composed of two large pores and six small pores, arranged in a rectangular lattice. The remaining layers of the pore cladding are composed of several small pores, arranged in a rectangular lattice and showing four-fold rotational symmetry.

[0006] Preferably, the number of layers of the pore cladding is two layers, and the second layer of the pore cladding is composed of 12 small pores.

[0007] Preferably, the number of layers of the pore cladding is two layers, and the second layer of the pore cladding is composed of 16 small pores.

[0008] Preferably, the number of layers of the pore cladding is three layers, the second layer of the pore cladding is composed of 16 small pores, and the third layer of the pore cladding is composed of 24 small pores.

[0009] Preferably, the number of layers of the pore cladding is three. The second layer of the pore cladding is composed of 16 small pores, and the third layer of the pore cladding is composed of 12 small pores.

[0010] Preferably, the number of layers of the pore cladding is four. The second layer of the pore cladding is composed of 16 small pores, the third layer of the pore cladding is composed of 24 small pores, and the fourth layer of the pore cladding is composed of 20 small pores.

[0011] Preferably, the number of layers of the pore cladding is four. The second layer of the pore cladding is composed of 16 small pores, the third layer of the pore cladding is composed of 24 small pores, and the fourth layer of the pore cladding is composed of 32 small pores.

[0012] Preferably, the distance Λ between adjacent two pores is 3.90 - 12.00 μm; the diameter D of the large pore is 3.79 - 12.00 μm, and the duty ratio D / Λ of the large pore is 0.33 - 1.30; the diameter d of the small pore is 2.00 - 7.00 μm, and the duty ratio d / Λ of the small pore is 0.17 - 0.90; the diameter d of the quartz cladding cl is 40 - 125 μm.

[0013] Preferably, the optical fiber further includes a coating layer coated outside the quartz cladding, and the diameter d of the coating layer co is 80 - 250 μm.

[0014] Preferably, the transmission loss of the optical fiber at a wavelength of 1550 nm is less than or equal to 5.00 dB / km, and the transmission loss at a wavelength of 1310 nm is less than or equal to 7.00 dB / km; the beat length of the optical fiber at a wavelength of 1550 nm is less than or equal to 5.00 mm, and the beat length at a wavelength of 1310 nm is less than or equal to 4.23 mm; the mode field diameter of the optical fiber at a wavelength of 1550 nm is less than or equal to 10.00 μm, and the mode field diameter at a wavelength of 1310 nm is less than or equal to 12.00 μm; the polarization extinction ratio of the optical fiber at a wavelength of 1550 nm is greater than or equal to 23 dB / 100 m, and the polarization extinction ratio at a wavelength of 1550 nm is greater than or equal to 15 dB / 1000 m.

[0015] Preferably, the core, the pore cladding and the quartz cladding are all prepared from pure quartz glass materials.

[0016] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0017] The cross-section of the highly birefringent microstructure optical fiber provided by the present invention is circular. The optical fiber sequentially includes a core, a pore cladding, and a silica cladding from the inside to the outside. The number of layers of the pore cladding is at least two. Multiple pores in each layer of the pore cladding are centrosymmetric with the center of the cross-section of the optical fiber as the center. The first layer of the pore cladding consists of two large pores and six small pores, arranged in a rectangular lattice. The remaining layers of the pore cladding consist of several small pores, arranged in a rectangular lattice and showing four-fold rotational symmetry. That is, in the present invention, multiple pores forming the innermost layer of the pore cladding are arranged in a rectangular lattice, and by introducing two large air holes, the four-fold rotational symmetry is highly disrupted, resulting in different propagation constants in the two fundamental mode directions of the optical fiber, thereby enhancing the birefringence performance of the optical fiber and enabling the microstructure optical fiber provided by the present invention to have high birefringence performance. Compared with the triangular lattice arrangement commonly used for the pores of conventional polarization-maintaining microstructure optical fibers, the rectangular lattice arrangement adopted in the present invention has stronger anisotropy and is more likely to generate birefringence. In addition, the number of layers of the pore cladding in the present invention can be as low as two. By reducing the number of layers of the pore cladding, the cladding diameter and the coating layer diameter can be reduced, realizing the miniaturization and lightweight design of the optical fiber. The number of layers of the pore cladding in the present invention can be adjusted according to application needs to achieve a wide range of application scenarios. In summary, the present invention provides an alternative highly birefringent microstructure optical fiber solution different from the prior art and has a high birefringence effect. The structure of the present invention is simple and easy to prepare, and can meet the application requirements in the directions of sensors, polarization-maintaining devices, lasers, etc. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of a highly birefringent microstructure optical fiber provided by Embodiment 1 of the present invention;

[0019] Figure 2 It is the fundamental mode of the x polarization state of a highly birefringent microstructure optical fiber provided by Embodiment 1 of the present invention;

[0020] Figure 3 It is the fundamental mode of the y polarization state of a highly birefringent microstructure optical fiber provided by Embodiment 1 of the present invention;

[0021] Figure 4 It is a schematic structural diagram of a highly birefringent microstructure optical fiber provided by Embodiment 2 of the present invention;

[0022] Figure 5 It is a schematic structural diagram of a highly birefringent microstructure optical fiber provided by Embodiment 3 of the present invention;

[0023] Figure 6 It is a schematic structural diagram of a highly birefringent microstructure optical fiber provided by Embodiment 4 of the present invention;

[0024] Figure 7Schematic diagram of the structure of a highly birefringent microstructure optical fiber provided in Embodiment 5 of the present invention;

[0025] Figure 8 Schematic diagram of the structure of a highly birefringent microstructure optical fiber provided in Embodiment 6 of the present invention. Detailed implementation manners

[0026] A highly birefringent microstructure optical fiber provided by the present invention, see Figure 1 , the cross-section of the optical fiber is circular, and the optical fiber sequentially includes a core 1, a pore cladding, and a silica cladding 4 from inside to outside; the number of layers of the pore cladding is at least two layers, and a plurality of pores in each layer of the pore cladding are centrosymmetric with the center of the cross-section of the optical fiber as the center. The first layer of the pore cladding is composed of two large pores 2 and six small pores 3, and is arranged in a rectangular lattice. That is, the innermost layer of the pore cladding can be understood as obtained by replacing two small pores 3 symmetric about the core 1 with two large pores 2. The remaining layers of the pore cladding are composed of several small pores 3, and are arranged in a rectangular lattice and are rotationally symmetric about four-fold. In addition, the optical fiber may further include a coating layer 5 coated outside the silica cladding 4.

[0027] The distance Λ between adjacent two pores is 3.90 - 12.00 μm; the diameter D of the large pore 2 is 3.79 - 12.00 μm, and the duty ratio D / Λ of the large pore 2 is 0.33 - 1.30; the diameter d of the small pore 3 is 2.00 - 7.00 μm, and the duty ratio d / Λ of the small pore 3 is 0.17 - 0.90; the diameter d of the silica cladding 4 cl is 40 - 125 μm, and the diameter d of the coating layer 5 co is 80 - 250 μm.

[0028] The core 1, the pore cladding, and the silica cladding 4 are all prepared from pure silica glass materials. That is, the optical fiber provided by the present invention uses pure silicon dioxide as the background material. The materials of the core 1 and the cladding structure (including the pore cladding and the silica cladding 4) in the present invention are single, and are all pure silica glass materials, so that the core 1 and the cladding structure have good mechanical matching and good anti-irradiation performance. In addition, the birefringence of a highly birefringent microstructure optical fiber provided by the present invention is generated based on the geometric asymmetry of the core, and has very low temperature sensitivity.

[0029] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners.

[0030] Embodiment 1:

[0031] Embodiment 1 provides a highly birefringent microstructure optical fiber, such as Figure 1As shown, the number of layers of the air-hole cladding is three; the first-layer air-hole cladding consists of two large air holes 2 and six small air holes 3, arranged in a rectangular lattice and centrosymmetric about the center of the cross-section circle of the optical fiber; the second-layer air-hole cladding consists of sixteen small air holes 3, arranged in a rectangular lattice and having four-fold rotational symmetry; the third-layer air-hole cladding consists of twenty-four small air holes 3, arranged in a rectangular lattice and having four-fold rotational symmetry. The fundamental mode of the x polarization state of the highly birefringent microstructure optical fiber provided in Example 1 is as shown in Figure 2 shown, and the fundamental mode of the y polarization state is as shown in Figure 3 shown.

[0032] Example 2:

[0033] Example 2 provides a highly birefringent microstructure optical fiber. As shown in Figure 4 shown, the number of layers of the air-hole cladding is two; the first-layer air-hole cladding consists of two large air holes and six small air holes, arranged in a rectangular lattice and centrosymmetric about the center of the cross-section circle of the optical fiber; the second-layer air-hole cladding consists of twelve small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry.

[0034] Example 3:

[0035] Example 3 provides a highly birefringent microstructure optical fiber. As shown in Figure 5 shown, the number of layers of the air-hole cladding is two; the first-layer air-hole cladding consists of two large air holes and six small air holes, arranged in a rectangular lattice and centrosymmetric about the center of the cross-section circle of the optical fiber; the second-layer air-hole cladding consists of sixteen small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry.

[0036] Example 4:

[0037] Example 4 provides a highly birefringent microstructure optical fiber. As shown in Figure 6 shown, the number of layers of the air-hole cladding is three; the first-layer air-hole cladding consists of two large air holes and six small air holes, arranged in a rectangular lattice and centrosymmetric about the center of the cross-section circle of the optical fiber; the second-layer air-hole cladding consists of sixteen small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry; the third-layer air-hole cladding consists of twelve small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry.

[0038] Example 5:

[0039] Example 5 provides a highly birefringent microstructure optical fiber, Figure 7As shown in the figure, the number of layers of the air hole cladding is four; the first layer of the air hole cladding consists of two large air holes and six small air holes, arranged in a rectangular lattice and centrosymmetric about the center of the cross-section of the optical fiber; the second layer of the air hole cladding consists of sixteen small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry; the third layer of the air hole cladding consists of twenty-four small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry; the fourth layer of the air hole cladding consists of twenty small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry.

[0040] Example 6:

[0041] Example 6 provides a highly birefringent microstructure optical fiber, as Figure 8 shown in the figure, the number of layers of the air hole cladding is four; the first layer of the air hole cladding consists of two large air holes and six small air holes, arranged in a rectangular lattice and centrosymmetric about the center of the cross-section of the optical fiber; the second layer of the air hole cladding consists of sixteen small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry; the third layer of the air hole cladding consists of twenty-four small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry; the fourth layer of the air hole cladding consists of thirty-two small air holes, arranged in a rectangular lattice and having four-fold rotational symmetry.

[0042] That is, the number of layers of the air hole cladding and the number of air holes in each layer in the present invention can be adjusted according to application requirements. The air hole cladding in the present invention is a centrosymmetric structure, and the air holes are arranged in a rectangular lattice.

[0043] The following describes the structural parameters and performance of the highly birefringent microstructure optical fiber provided by the present invention in combination with specific numerical values. Table 1 lists the optical fiber structure cross-section parameters of multiple test examples provided by the present invention, and Table 2 lists the optical transmission characteristics corresponding to each optical fiber in Table 1.

[0044] Table 1 Optical Fiber Structure Cross-Section Parameters

[0045]

[0046]

[0047] Table 2 Optical Fiber Performance Parameters

[0048]

[0049] As can be seen from Table 1 and Table 2, the transmission loss of the optical fiber at a wavelength of 1550 nm is less than or equal to 5.00 dB / km, and the transmission loss at a wavelength of 1310 nm is less than or equal to 7.00 dB / km; the beat length of the optical fiber at a wavelength of 1550 nm is less than or equal to 5.00 mm, and the beat length at a wavelength of 1310 nm is less than or equal to 4.23 mm; the mode field diameter of the optical fiber at a wavelength of 1550 nm is less than or equal to 10.00 μm, and the mode field diameter at a wavelength of 1310 nm is less than or equal to 12.00 μm; the polarization extinction ratio of the optical fiber at a wavelength of 1550 nm is greater than or equal to 23 dB / 100 m, and the polarization extinction ratio at a wavelength of 1550 nm is greater than or equal to 15 dB / 1000 m.

[0050] In summary, through specific designs in multiple aspects including aperture, hole spacing, hole arrangement, etc., the present invention obtains a highly birefringent microstructure optical fiber that can meet the actual application requirements.

[0051] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A highly birefringent microstructure optical fiber, characterized in that, the cross-section of the optical fiber is circular, and the optical fiber successively includes a core, a pore cladding, and a silica cladding from inside to outside; the number of layers of the pore cladding is at least two layers, and a plurality of pores in each layer of the pore cladding are centrosymmetric with the center of the cross-section of the optical fiber as the center; the first layer of the pore cladding is composed of two large pores and six small pores, arranged in a rectangular lattice; the remaining layers of the pore cladding are composed of several small pores, arranged in a rectangular lattice and showing four-fold rotational symmetry; The distance Λ between two adjacent air holes is 3.90 to 12.00 µm; the diameter D of the large air hole is 3.79 to 12.00 µm, and the duty ratio D / Λ of the large air hole is 0.33 to 1.30; the diameter d of the small air hole is 2.00 to 7.00 µm, and the duty ratio d / Λ of the small air hole is 0.17 to 0.90; the diameter d of the quartz cladding cl is 40 to 125 µm.

2. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the number of layers of the pore cladding is two layers, and the second layer of the pore cladding is composed of 12 small pores.

3. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the number of layers of the pore cladding is two layers, and the second layer of the pore cladding is composed of 16 small pores.

4. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the number of layers of the pore cladding is three layers, the second layer of the pore cladding is composed of 16 small pores, and the third layer of the pore cladding is composed of 24 small pores.

5. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the number of layers of the pore cladding is three layers, the second layer of the pore cladding is composed of 16 small pores, and the third layer of the pore cladding is composed of 12 small pores.

6. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the number of layers of the pore cladding is four layers, the second layer of the pore cladding is composed of 16 small pores, the third layer of the pore cladding is composed of 24 small pores, and the fourth layer of the pore cladding is composed of 20 small pores.

7. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the number of layers of the pore cladding is four layers, the second layer of the pore cladding is composed of 16 small pores, the third layer of the pore cladding is composed of 24 small pores, and the fourth layer of the pore cladding is composed of 32 small pores.

8. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, The optical fiber further includes a coating layer coated outside the quartz cladding, and the diameter d of the coating layer co is 80 to 250 µm.

9. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, the transmission loss of the optical fiber at a wavelength of 1550 nm is less than or equal to 5.00 dB / km, and the transmission loss at a wavelength of 1310 nm is less than or equal to 7.00 dB / km; the beat length of the optical fiber at a wavelength of 1550 nm is less than or equal to 5.00 mm, and the beat length at a wavelength of 1310 nm is less than or equal to 4.23 mm; the mode field diameter of the optical fiber at a wavelength of 1550 nm is less than or equal to 10.00 µm, and the mode field diameter at a wavelength of 1310 nm is less than or equal to 12.00 µm; the polarization extinction ratio of the optical fiber at a wavelength of 1550 nm is greater than or equal to 23 dB / 100 m, and the polarization extinction ratio at a wavelength of 1550 nm is greater than or equal to 15 dB / 1000 m.

10. The highly birefringent microstructure optical fiber according to claim 1, characterized in that, The core, the air-hole cladding and the quartz cladding are all made of pure quartz glass material.

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