CN118393637A - Small mode field single polarization hollow anti-resonance optical fiber based on semi-elliptical cladding pipe - Google Patents
Small mode field single polarization hollow anti-resonance optical fiber based on semi-elliptical cladding pipe Download PDFInfo
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- 238000005253 cladding Methods 0.000 title claims abstract description 370
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- 239000000835 fiber Substances 0.000 claims abstract description 64
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- 239000011521 glass Substances 0.000 claims abstract description 21
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
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- G—PHYSICS
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
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Abstract
The invention relates to a small-mode-field single-polarization hollow anti-resonance optical fiber based on a semi-elliptical cladding tube, belongs to the technical field of optical fibers, and solves the problems of large fiber core, high coupling/transmission loss, poor bending resistance and adverse miniaturized application in the prior art. The invention utilizes the semi-elliptical cladding tube to construct the fiber core region, so that the internal space surrounded by the cladding tube and the elliptical cladding tube is larger, the cladding tube and the embedded tube can be additionally placed, multiple glass walls and air gaps are introduced, and the loss lower than 5.5dB/km is realized on the premise of ensuring the smaller fiber core area; by introducing an elliptical cladding tube with a glass wall and a larger x-axis gap in the x-direction, coupling between a fundamental mode x-polarization state FM x and a cladding mode is increased, and the limiting loss of the fundamental mode x-polarization state FM x is improved on the basis of keeping the limiting loss of the fundamental mode y-polarization state FM y almost unchanged; and single-mode transmission and miniaturized application of the fiber core mode are effectively ensured.
Description
Technical Field
The invention relates to the technical field of optical fibers, in particular to a small-mode-field single-polarization hollow anti-resonance optical fiber based on a semi-elliptical cladding tube.
Background
In most polarization-sensitive fiber systems, polarization control or maintaining devices, including polarization maintaining fibers, are required to ensure the stability of the polarization of the transmitted light. However, even if the polarization maintaining fiber is adopted, when the external environment is disturbed, the characteristics of the glass material still change, so that the polarization cross coupling phenomenon of the light transmitted inside the polarization maintaining fiber occurs, and the system performance is reduced. Taking an optical fiber gyro with a full polarization maintaining scheme as an example, two polarized lights in two directions exist in an optical fiber ring due to welding errors and non-ideal actual devices, when an external environment is disturbed, stray light polarized in the y direction is partially coupled into the x direction and interferes with a main wave polarized in the x direction, and noise and drift output by the optical fiber gyro are further increased. By utilizing the single polarization state transmission characteristic of the single polarization optical fiber, the parasitic interference can be reduced, thereby improving the performance of the optical fiber system. Compared with the traditional solid optical fiber, the hollow optical fiber has the characteristic that most of optical fields are transmitted in gas, so that the hollow optical fiber has the advantages of high damage threshold, low transmission delay, low nonlinearity, insensitivity to environmental disturbance and the like. According to the light guiding mechanism, the hollow fiber can be divided into a hollow photonic crystal fiber and a hollow antiresonant fiber. The electric field intensity at the interface of the glass cladding pipe and the air in the hollow anti-resonance optical fiber is lower depending on the anti-resonance principle, so that the influence of the change of the material characteristic on the intermode coupling is smaller, the polarization state of the internal transmission light is not easily influenced by the disturbance of the external environment, and the hollow anti-resonance optical fiber is more suitable for being used as a single-polarization hollow polarization-maintaining optical fiber.
In the prior art, a circular nested structure is arranged in the x direction of the single-polarization hollow anti-resonance optical fiber, and U-shaped nested structures are arranged in the other four directions, so that the x-polarization fundamental mode and the cladding mode are coupled to increase the loss of the single-polarization hollow anti-resonance optical fiber, and the single-polarization transmission is realized, but the working bandwidth of the polarization loss ratio PER is only 10.8nm. A single polarization low-loss hollow negative curvature optical fiber is provided with a U-shaped nested tube with different thickness from a circular tube in the y direction so as to change the loss of an x-polarization state or y-polarization state fundamental mode at different wavelengths, thereby realizing single polarization operation. However, considering that the core diameter of a conventional optical fiber in optical fiber sensing applications is generally less than 8.3 μm, direct coupling of a hollow core optical fiber with a conventional optical fiber using the above-mentioned elliptical core stub of more than 45 μm results in very large coupling loss. A high-birefringence low-loss single-polarization hollow anti-resonance optical fiber is characterized in that a nested silicon tube is arranged in the y direction, so that a y polarization state fundamental mode is coupled with a mode guided by the nested silicon tube to improve the loss of the optical fiber, single polarization operation is finally realized, when the bending direction is the x direction and the bending radius is larger than 3cm, the fundamental mode loss is lower than 4dB/km, but when the bending direction is the y direction and the bending radius is smaller than 7cm, the polarization loss ratio PER is smaller than 100, and single polarization transmission cannot be realized.
In summary, the prior art has the problems of large fiber core, high coupling/transmission loss, poor bending resistance and unfavorable miniaturized application.
Disclosure of Invention
In view of the above problems, the invention provides a small-mode-field single-polarization hollow anti-resonance optical fiber based on a semi-elliptical cladding tube, which solves the problems of large fiber core, high coupling/transmission loss, poor bending resistance and adverse miniaturized application in the prior art.
The invention provides a small-mode field single-polarization hollow anti-resonance optical fiber based on a semi-elliptical cladding pipe, which comprises an optical fiber structure and an optical fiber gap, wherein under the combined action of the optical fiber structure and the optical fiber gap, the transmission loss of a fundamental mode x polarization state FM x is raised, the transmission loss of a fundamental mode y polarization state FM y is not affected, and further single polarization transmission is realized; wherein the fiber structure comprises an outer cladding layer 101, a first elliptical cladding tube 102 and a connecting rod 103; the inner space surrounded by the outer cladding 101 is provided with a first elliptical cladding tube 102; the cross section of the outer cladding 101 is annular, and a connecting rod 103 is arranged on the inner side of the circular inner ring of the outer cladding 101 and is used for connecting the outer cladding 101 and the first elliptical cladding pipe 102; the major axis of the first elliptical cladding tube 102 is located on the x-axis and the minor axis is located on the y-axis;
The optical fiber structure further comprises four groups of pipe wall structures which are arranged on the first elliptical cladding pipe 102 and positioned on the inner side of the first elliptical cladding pipe, and each group of pipe wall structures comprises a semi-elliptical cladding pipe; the first group of pipe wall structures and the second group of pipe wall structures have the same structure, are respectively arranged in the positive direction of the x axis and the negative direction of the x axis, and are respectively symmetrical relative to the x axis; the third group of pipe wall structures and the fourth group of pipe wall structures have the same structure, are respectively arranged in the positive direction of the y axis and the negative direction of the y axis, and are respectively symmetrical relative to the y axis;
the optical fiber structure further includes four round cladding pipes 104 having the same structure disposed on the first elliptical cladding pipe 102 at the inner side thereof; the four round cladding pipes are respectively positioned in the first quadrant angular bisector direction, the second quadrant angular bisector direction, the third quadrant angular bisector direction and the fourth quadrant angular bisector direction;
The fiber gap is a space defined by individual components of the fiber structure, either independently or in combination.
Further, the first group of pipe wall structures and the second group of pipe wall structures respectively include a first x-axis semi-elliptical cladding pipe 105, a second x-axis semi-elliptical cladding pipe 106 and a second elliptical cladding pipe 107 which are arranged on the first elliptical cladding pipe 102 in sequence from inside to outside along the radial direction, and a rectangular glass wall 108 which is arranged on the second elliptical cladding pipe 107 and is parallel to the y-axis; the second x-axis semi-elliptical cladding tube 106 is located in the inner space formed by the first x-axis semi-elliptical cladding tube 105 and the first elliptical cladding tube 102; the second elliptical cladding tube 107 is located in the interior space formed by the second x-axis semi-elliptical cladding tube 106 and the first elliptical cladding tube 102.
Further, the third set of pipe wall structures and the fourth set of pipe wall structures respectively include a first y-axis semi-elliptical cladding pipe 109, a second y-axis semi-elliptical cladding pipe 110 and a double elliptical nested pipe outer layer 111 which are arranged on the first elliptical cladding pipe 102 in sequence from inside to outside along the radial direction, and a double elliptical nested pipe inner layer 112 which is arranged on the double elliptical nested pipe outer layer 111; the second y-axis semi-elliptical cladding pipe 110 is located in the inner space formed by the first y-axis semi-elliptical cladding pipe 109 and the first elliptical cladding pipe 102; the double elliptical sleeve outer layer 111 is located in the interior space formed by the second y-axis semi-elliptical cladding tube 110 and the first elliptical cladding tube 102.
Further, the optical fiber gap includes a fiber core 201, and the cross section of the fiber core 201 is circular, and the circular is tangential to the vertex of the first x-axis semi-elliptical cladding tube 105 of the first set of tube wall structures, the vertex of the first x-axis semi-elliptical cladding tube 105 of the second set of tube wall structures, the vertex of the first y-axis semi-elliptical cladding tube 109 of the third set of tube wall structures, and the vertex of the first y-axis semi-elliptical cladding tube 109 of the fourth set of tube wall structures.
Further, the fiber gap also includes a first x-axis gap 202, a second x-axis gap 203, a third x-axis gap 204, and a fourth x-axis gap 205; wherein the first x-axis gap 202 is surrounded by the first elliptical cladding tube 102, the first x-axis semi-elliptical cladding tube 105, and the second x-axis semi-elliptical cladding tube 106; the second x-axis gap 203 is surrounded by the first elliptical cladding tube 102, the second x-axis semi-elliptical cladding tube 106, and the second elliptical cladding tube 107; the third x-axis gap 204 and the fourth x-axis gap 205 are a half of the inner space of the second elliptical cladding tube 107, which is partitioned by the rectangular glass wall 108, near the core 201, and a half of the inner space, which is far from the core 201, respectively;
Further, by adjusting the thicknesses of the first x-axis semi-elliptical cladding tube 105 and the first y-axis semi-elliptical cladding tube 109, and the dimensions of the first x-axis gap 202 and the first y-axis gap 206, the birefringent characteristics of the fundamental mode y-polarization state FM y and the fundamental mode x-polarization state FM x can be improved; by adjusting the dimensions of the first y-axis semi-elliptical cladding tube 109, the second y-axis semi-elliptical cladding tube 110, the double elliptical sleeve outer layer 111, the double elliptical sleeve inner layer 112, and the first y-axis gap 206, the second y-axis gap 207, the third y-axis gap 208, and the fourth y-axis gap 209, the loss of the higher-order mode HOM can be increased, and single-mode operation can be realized.
Further, the fiber gap further includes a first y-axis gap 206, a second y-axis gap 207, a third y-axis gap 208, and a fourth y-axis gap 209; wherein the first y-axis gap 206 is surrounded by the first elliptical cladding tube 102, the first y-axis semi-elliptical cladding tube 109, and the second y-axis semi-elliptical cladding tube 110; the second y-axis gap 207 is surrounded by the first elliptical cladding tube 102, the second y-axis semi-elliptical cladding tube 110, and the double elliptical nested tube outer layer 111; the third y-axis gap 208 is defined by the double elliptical nested tube outer layer 111 and the double elliptical nested tube inner layer 112; the fourth y-axis gap 209 is defined by the double elliptical nested tube inner layer 112;
Further, the first y-axis semi-elliptical cladding tube 109, the second y-axis semi-elliptical cladding tube 110, the double elliptical nested tube outer layer 111 and the double elliptical nested tube inner layer 112 are used for providing anti-resonance for the small mode field single polarization hollow core anti-resonance fiber based on the semi-elliptical cladding tube, so that the limiting loss of the fundamental mode y polarization state FM y can be reduced. By adjusting the pitches of the first x-axis gap 202, the second x-axis gap 203, the third x-axis gap 204, and the fourth x-axis gap 205, and the size of the second elliptical cladding tube 107, the limiting loss of the fundamental mode x-polarization state FM x can be increased, and single polarization transmission can be realized.
Further, the material of the optical fiber structure is quartz glass.
Further, the fiber gap is filled with air.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The small-mode-field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe utilizes the semi-elliptical cladding pipe to construct a fiber core region, so that the inner space surrounded by the cladding pipe and the elliptical cladding pipe is larger, the cladding pipe and the embedded pipe can be additionally placed, multiple glass walls and air gaps are introduced, and the transmission loss of the fundamental mode y polarization state FM y lower than 5.5dB/km is realized on the premise of ensuring the smaller fiber core area.
(2) The thickness of the first x-axis semi-elliptical cladding tube 105 is set to be different from that of the first y-axis semi-elliptical cladding tube 109, so that the difference between the effective refractive index of the fundamental mode x-polarization state FM x and the effective refractive index of the fundamental mode y-polarization state FM y is larger than 1.2X10. 10 -4, and higher double refraction is introduced to realize polarization-preserving characteristics.
(3) According to the small mode field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe, the coupling of a fundamental mode x polarization state FM x and a cladding mode x polarization state is increased by introducing the elliptical cladding pipe with a glass wall and a larger second x-axis gap in the x direction; on the basis of maintaining the limit loss of the fundamental mode y polarization state FM y almost unchanged, the limit loss of the fundamental mode x polarization state FM x is improved; at an operating bandwidth of 42nm, a polarization loss ratio PER above 100 and a fundamental mode y-polarization FM y transmission loss below 20dB/km are achieved.
(4) According to the small-mode-field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe, the high-order mode HOM and the cladding mode are guided to be strongly coupled by adjusting the size and the distance between the cladding pipe and the embedded pipe, so that the loss of the high-order mode HOM is improved, the high-order mode suppression ratio HOMER is more than 35dB, and single-mode transmission is effectively ensured.
(5) The small-mode-field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe has transmission loss of the fundamental mode y polarization FM y lower than 12dB/km and polarization loss ratio PER higher than 100 in a bending state with bending directions of x, y and 45 degrees and bending radius larger than 1.84cm, and is beneficial to miniaturization application based on the single-polarization hollow anti-resonance optical fiber.
(6) The small mode field single polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe has smaller fiber core radius, and the theoretical value of the coupling loss is lower than 0.1dB when the small mode field single polarization hollow anti-resonance optical fiber is directly coupled with the traditional solid optical fiber with the fiber core radius of 4.5 mu m. The optical fiber provided by the invention can realize lower coupling loss even without using a mode field adapter in various applications requiring coupling of the single-polarization hollow anti-resonance optical fiber and the traditional solid optical fiber, and is beneficial to miniaturized application.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention.
FIG. 1 is a schematic diagram of the cross-sectional components of a small mode field single-polarization hollow-core antiresonant fiber based on a semi-elliptical cladding tube according to the present invention;
FIG. 2 is a schematic parameter diagram of a cross-section component of a small mode field single-polarization hollow-core antiresonant fiber based on a semi-elliptical cladding tube according to the present invention-part 1;
FIG. 3 is a schematic parameter diagram of a cross-section component of a small mode field single-polarization hollow-core antiresonant fiber based on a semi-elliptical cladding tube according to the present invention, section 2;
FIG. 4 is a schematic diagram showing the relationship between the transmission loss of the y polarization state of the fundamental mode and the variation of the polarization loss ratio PER with the bending radius of the small-mode field single-polarization hollow anti-resonance optical fiber based on a semi-elliptical cladding pipe in different bending directions;
FIG. 5 is a schematic diagram showing the relationship between the high-order mode rejection ratio HOMER along with the bending radius and the working wavelength in a flat state of the small mode field single-polarization hollow anti-resonance fiber based on a semi-elliptical cladding tube according to the present invention;
FIG. 6 is a schematic diagram showing the relationship between the transmission loss of the fundamental mode y polarization FM y and the change of the polarization loss ratio PER with the working wavelength of a small mode field single-polarization hollow anti-resonance fiber based on a semi-elliptical cladding pipe;
Fig. 7 is a schematic diagram showing the relationship between the ratio of the coupling coefficient κ m2x of the fundamental mode x-polarization state FM x and the cladding mode x-polarization state CMx 2x guided by the second x-axis gap 203, the ratio of the coupling coefficient κ m2y of the fundamental mode y-polarization state FM y and the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203, the difference Δn m2y between the refractive indexes of the fundamental mode y-polarization state FM y and the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203, and the ratio of the difference Δn m2x between the refractive indexes of the fundamental mode x-polarization state FM x and the cladding mode x-polarization state CMx 2x guided by the second x-axis gap 203, along with the change of the distance h 2x of the second x-axis gap 203.
Fig. 8 is a schematic diagram showing the relationship between the limiting loss of the cladding mode x-polarization state CMx 2x and the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203 of the small mode field single-polarization hollow anti-resonant fiber based on the semi-elliptical cladding tube and the limiting loss ratio of the fundamental mode x-polarization state FM x and the fundamental mode y-polarization state FM y along with the distance h 2x of the second x-axis gap 203 in the x direction.
Reference numerals:
101-an outer cladding; 102-a first elliptical cladding tube; 103-connecting rods; 104-a round cladding tube; 105-a first x-axis semi-elliptical cladding tube; 106-a second x-axis semi-elliptical cladding tube; 107-a second elliptical cladding tube; 108-rectangular glass walls; 109-a first y-axis semi-elliptical cladding tube; 110-a second y-axis semi-elliptical cladding tube; 111-double elliptical nested tube outer layer; 112-double elliptical nested tube inner layer; 201-a fiber core; 202-first x-axis gap; 203-a second x-axis gap; 204-third x-axis gap; 205-fourth x-axis gap; 206-a first y-axis gap; 207-second y-axis gap; 208-third y-axis gap; 209-fourth y-axis gap.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. It should be noted that, without conflict, the embodiments of the present invention and features in the embodiments may be combined with each other. In addition, the invention may be practiced otherwise than as specifically described and thus the scope of the invention is not limited by the specific embodiments disclosed herein.
The invention discloses a small-mode-field single-polarization hollow anti-resonance optical fiber based on a semi-elliptical cladding pipe, which comprises an optical fiber structure and an optical fiber gap as shown in fig. 1-3, wherein under the combined action of the optical fiber structure and the optical fiber gap, the transmission loss of a fundamental mode x-polarization state FM x is raised, and the transmission loss of a fundamental mode y-polarization state FM y is not affected, so that single polarization transmission is realized.
Specifically, the fiber structure includes an outer cladding 101, a first elliptical cladding tube 102, and a connecting rod 103; the inner space surrounded by the outer cladding 101 is provided with a first elliptical cladding tube 102; the cross section of the outer cladding 101 is annular, and a connecting rod 103 is arranged on the inner side of the circular inner ring of the outer cladding 101 and is used for connecting the outer cladding 101 and the first elliptical cladding pipe 102; the major axis of the first elliptical cladding tube 102 is located on the x-axis and the minor axis is located on the y-axis; a connecting rod 103 is used to connect the overclad 101 and the first elliptical cladding tube 102.
The optical fiber structure further comprises four groups of pipe wall structures which are arranged on the first elliptical cladding pipe 102 and positioned on the inner side of the first elliptical cladding pipe, and each group of pipe wall structures comprises a semi-elliptical cladding pipe; the first group of pipe wall structures and the second group of pipe wall structures have the same structure, are respectively arranged in the positive direction of the x axis and the negative direction of the x axis, and are respectively symmetrical relative to the x axis; the third group of pipe wall structures and the fourth group of pipe wall structures have the same structure, are respectively arranged in the positive direction of the y axis and the negative direction of the y axis, and are respectively symmetrical relative to the y axis.
The first group of pipe wall structures and the second group of pipe wall structures respectively comprise a first x-axis semi-elliptical cladding pipe 105, a second x-axis semi-elliptical cladding pipe 106 and a second elliptical cladding pipe 107 which are arranged on the first elliptical cladding pipe 102 in sequence from inside to outside along the radial direction, and a rectangular glass wall 108 which is arranged on the second elliptical cladding pipe 107 and is parallel to the y axis; the second x-axis semi-elliptical cladding tube 106 is located in the inner space formed by the first x-axis semi-elliptical cladding tube 105 and the first elliptical cladding tube 102; the second elliptical cladding tube 107 is located in the interior space formed by the second x-axis semi-elliptical cladding tube 106 and the first elliptical cladding tube 102.
The third set of pipe wall structures and the fourth set of pipe wall structures respectively comprise a first y-axis semi-elliptical cladding pipe 109, a second y-axis semi-elliptical cladding pipe 110 and a double elliptical nested pipe outer layer 111 which are sequentially distributed from inside to outside along the radial direction and are arranged on the first elliptical cladding pipe 102, and a double elliptical nested pipe inner layer 112 which is arranged on the double elliptical nested pipe outer layer 111; the second y-axis semi-elliptical cladding pipe 110 is located in the inner space formed by the first y-axis semi-elliptical cladding pipe 109 and the first elliptical cladding pipe 102; the double elliptical sleeve outer layer 111 is located in the interior space formed by the second y-axis semi-elliptical cladding tube 110 and the first elliptical cladding tube 102.
The optical fiber structure further includes four round cladding pipes 104 having the same structure disposed on the first elliptical cladding pipe 102 at the inner side thereof; the four round cladding pipes are respectively positioned in the first quadrant angular bisector direction, the second quadrant angular bisector direction, the third quadrant angular bisector direction and the fourth quadrant angular bisector direction.
The fiber gap is a space defined by individual components of the fiber structure, either independently or in combination.
The fiber gap includes a core 201, the cross-section of the core 201 being circular, the circular being tangential to the vertices of the first x-axis semi-elliptical cladding tube 105 of the first set of tube wall structures, the first x-axis semi-elliptical cladding tube 105 of the second set of tube wall structures, the first y-axis semi-elliptical cladding tube 109 of the third set of tube wall structures, and the first y-axis semi-elliptical cladding tube 109 of the fourth set of tube wall structures.
The fiber gap further includes a first x-axis gap 202, a second x-axis gap 203, a third x-axis gap 204, and a fourth x-axis gap 205; wherein the first x-axis gap 202 is surrounded by the first elliptical cladding tube 102, the first x-axis semi-elliptical cladding tube 105, and the second x-axis semi-elliptical cladding tube 106; the second x-axis gap 203 is surrounded by the first elliptical cladding tube 102, the second x-axis semi-elliptical cladding tube 106, and the second elliptical cladding tube 107; the third x-axis gap 204 and the fourth x-axis gap 205 are a half of the inner space of the second elliptical cladding tube 107, which is partitioned by the rectangular glass wall 108, near the core 201, and a half of the inner space, which is far from the core 201, respectively;
The fiber gap further includes a first y-axis gap 206, a second y-axis gap 207, a third y-axis gap 208, and a fourth y-axis gap 209; wherein the first y-axis gap 206 is surrounded by the first elliptical cladding tube 102, the first y-axis semi-elliptical cladding tube 109, and the second y-axis semi-elliptical cladding tube 110; the second y-axis gap 207 is surrounded by the first elliptical cladding tube 102, the second y-axis semi-elliptical cladding tube 110, and the double elliptical nested tube outer layer 111; the third y-axis gap 208 is defined by the double elliptical nested tube outer layer 111 and the double elliptical nested tube inner layer 112; fourth y-axis gap 209 is defined by double oval nested tube inner layer 112.
The limiting loss α ck for mode k can be expressed as:
wherein κ k,l is the coupling coefficient of mode k and mode l; Δβ k,l is the difference between the propagation constants of mode k and mode l; alpha cl is the limiting loss of mode l; e k、El is the electric field intensity distribution of mode k and mode l, respectively; The conjugate complex number of the electric field intensity distribution of the mode l, A is the cross-sectional area of the small-mode field single-polarization hollow anti-resonance fiber based on the semi-elliptical cladding tube. When the polarization states of the mode k and the mode l are mutually orthogonal, the coupling coefficient of the mode k and the mode l is 0, and the limiting loss of the mode k is not influenced by the mode l. Meanwhile, the smaller the difference between the effective refractive indexes of the two modes, the larger the loss of mode l, and the larger the limiting loss of mode k caused by mode l.
In this patent, the transmission loss of the mode k is a linear superposition of the confinement loss of the mode k and the surface scattering loss.
The first y-axis semi-elliptical cladding tube 109, the second y-axis semi-elliptical cladding tube 110, the double elliptical nested tube outer layer 111 and the double elliptical nested tube inner layer 112 are used for providing anti-resonance for a small-mode-field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding tube, so that a larger refractive index difference exists between a fundamental mode y polarization state FM y and a fundamental mode x polarization state FM x and a cladding mode y polarization state CMy y and a cladding mode x polarization state CMy x in the y direction and the small mode field overlap, and the fact that the fundamental mode y polarization state FM y and the fundamental mode x polarization state FM x are not strongly coupled with the cladding mode y polarization state CMy y and the cladding mode x polarization state CMy x in the y direction is finally achieved, and lower limiting loss of the fundamental mode y polarization state FM y is finally achieved.
By adjusting the spacing between the first x-axis gap 202, the second x-axis gap 203, the third x-axis gap 204 and the fourth x-axis gap 205, and the size of the second elliptical cladding tube 107, the difference in refractive index between the fundamental mode x-polarization state FM x and the cladding mode x-polarization state CMx 2x guided by the second x-axis gap 203 is smaller, the coupling coefficient is larger, and stronger coupling is generated, while the difference in refractive index between the fundamental mode y-polarization state FM y and the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203 is larger, the coupling coefficient is smaller, so that the transmission of the fundamental mode y-polarization state FM y in the fiber core 201 is not affected, and further, the limiting loss of the fundamental mode x-polarization state FM x is improved while the limiting loss of the fundamental mode y-polarization state FM y is almost unchanged, and single polarization transmission is finally realized.
By adjusting the thicknesses of the first x-axis semi-elliptical cladding tube 105 and the first y-axis semi-elliptical cladding tube 109, and the dimensions of the first x-axis gap 202 and the first y-axis gap 206, the base mode y-polarization state FM y and the base mode x-polarization state FM x can have higher birefringence characteristics; by adjusting the dimensions of the first y-axis semi-elliptical cladding tube 109, the second y-axis semi-elliptical cladding tube 110, the double elliptical cladding tube outer layer 111, the double elliptical cladding tube inner layer 112, the first y-axis gap 206, the second y-axis gap 207, the third y-axis gap 208, and the fourth y-axis gap 209, the high-order mode HOM can be strongly coupled with the cladding tube and the cladding mode guided by the optical fiber gap, so that the loss of the high-order mode HOM can be improved, and single-mode operation can be realized.
Preferably, the material of the fiber structure is quartz glass, and the fiber gap is filled with air.
Alternatively, the diameter Dc of the core 201 is 9.7 μm to 10.2 μm.
The difference between the major half axis a 1 and the minor half axis b 1 of the first elliptical cladding tube 102 is 1.8-2.5 um, and the thickness t 7 of the first elliptical cladding tube 102 is 0.5-0.8 um. Alternatively, the spacing g between adjacent first x-axis semi-elliptical cladding tube 105 and first y-axis semi-elliptical cladding tube 109 is 1.6 μm to 2.2 μm.
Optionally, in the y-direction, the center of the first y-axis semi-elliptical cladding tube 109 is located on the y-axis; the minor axis b 1y of the first y-axis semi-elliptical cladding tube 109 is 16um to 22um, the thickness t 1y of the first y-axis semi-elliptical cladding tube 109 is 0.42um to 0.48um, and the major axis a 1y of the first y-axis semi-elliptical cladding tube 109 is determined according to the following formula:
It should be noted that the thickness of the first y-axis semi-elliptical cladding tube 109 is equal throughout, and the other parts of the optical fiber structure are also the same, which will not be described in detail.
Optionally, the distance h 1y of the first y-axis gap 206 in the y-direction is 3 μm to 4 μm.
Alternatively, in the y-direction, the second y-axis semi-elliptical cladding tube 110 is concentric with the first y-axis semi-elliptical cladding tube 109; the major half axis a 2y＝a1y-h1y of the second y-axis semi-elliptical cladding tube 110, the minor half axis b 2y＝b1y-h1y×ratio1y of the second y-axis semi-elliptical cladding tube 110, the thickness t 2y of the second y-axis semi-elliptical cladding tube 110 being 0.45 μm to 0.6 μm; wherein, the value range of the ratio 1y is 0.6-1.1.
Alternatively, the distance h 2y of the second y-axis gap 207 in the y-direction is 4 μm to 5.6 μm.
Alternatively, in the y direction, the major axis a 3y＝b1-(Dc/2+h1y+h2y of the double oval nested tube outer layer 111), the minor axis b 3y＝a3y/ratio2y of the double oval nested tube outer layer 111, the thickness t 3y of the double oval nested tube outer layer 111 is 0.45 μm to 0.65 μm; wherein, the value range of the ratio 2y is 1-1.3.
Optionally, the distance h 3y of the third y-axis gap 208 in the y-direction is 4 μm to 5.2 μm.
Optionally, in the y direction, the major axis a 4y＝a3y-h3y of the double oval nested tube inner layer 112, the minor axis b 4y＝a4y/ratio2y of the double oval nested tube inner layer 112, and the thickness t 4y of the double oval nested tube inner layer 112 is 0.45 μm to 0.6 μm.
Optionally, in the x-direction, the center of the first x-axis semi-elliptical cladding tube 105 is located on the x-axis; the shorter half axis b 1x＝b1y of the first x-axis semi-elliptical cladding tube 105, the longer half axis a 1x＝a1y of the first x-axis semi-elliptical cladding tube 105, the difference t 1x-t1y between the thickness t 1x of the first x-axis semi-elliptical cladding tube 105 and the thickness t 1y of the first y-axis semi-elliptical cladding tube 109 is in the range of 0.08 μm to 0.14 μm
Optionally, the distance h 1x of the first x-axis gap 202 in the x-direction is 3.5 μm to 4.4 μm.
Alternatively, in the x-direction, the second x-axis semi-elliptical cladding tube 106 is concentric with the first x-axis semi-elliptical cladding tube 105; the long half axis a 2x＝a1x-h1x of the second x-axis semi-elliptical cladding tube 106, the short half axis b 2x＝b1x-h1x×ratio1x of the second x-axis semi-elliptical cladding tube 106, and the thickness t 2x of the second x-axis semi-elliptical cladding tube 106 is 0.51-0.65 μm; wherein the value range of the ratio 1x is 0.5-0.78.
Alternatively, the distance h 2x of the second x-axis gap 203 in the x-direction is 5.5 μm to 7 μm.
Alternatively, in the x-direction, the center of the second elliptical cladding tube 107 is located on the x-axis; the thickness t 3x of the second elliptical cladding tube 107 is 0.58 μm to 0.67 μm, and the ratio 2x of the short axis b 3x to the long axis a 3x of the second elliptical cladding tube 107 is 0.75 to 0.9; the midpoint of the rectangular glass wall 108 is located at the center of the second elliptical cladding tube 107 and has a thickness t 4x of 0.6 μm to 0.68 μm.
Optionally, between each set of adjacent tube wall structures, i.e. in the directions of 45 °, 135 °, 225 ° and 315 °, a circular cladding tube 104 of the same size is placed, respectively, which circular cladding tube 104 is fixed by the first elliptical cladding tube 102. The diameter D 5 of the round cladding pipe 104 is 3 μm to 5.4 μm, and the thickness t 5 of the round cladding pipe 104 is 0.48 μm to 0.67 μm.
Alternatively, two connecting rods 103 are symmetrical about the y-axis, the thickness t 6 of the connecting rods 103 being 1.5 μm to 2.5 μm and the width b 6 of the connecting rods 103 being 4 μm to 6.5 μm.
The larger the number of silica glass walls and air gaps, the more likely it is that the smaller the confinement loss of the hollow-core antiresonant fiber will be. Because the fiber core diameter of the proposed optical fiber is smaller, if a semicircular cladding tube or a circular cladding tube commonly used for hollow anti-resonance optical fibers is used to form the fiber core region, the space for placing other inner cladding structures is smaller, and lower loss is difficult to realize, so that the first x-axis semi-elliptical cladding tube 105 and the first y-axis semi-elliptical cladding tube 109 are used to construct the fiber core region. To increase the number of quartz glass walls and air gaps to further reduce the loss of fundamental mode, a second x-axis semi-elliptical cladding tube 106, a second y-axis semi-elliptical cladding tube 110, a double elliptical nested outside tube 111, a double elliptical nested inside tube 112, a second elliptical cladding tube 107, a rectangular glass wall 108, and a circular cladding tube 104 are introduced. When the optical fiber realizes the low loss to high polarization loss ratio PER of the fundamental mode y polarization state FM y, the space required for the y-direction structure is smaller than that required for the x-direction structure, so that the first elliptical cladding tube 102 is used with its short axis in the y-direction and its long axis in the x-direction.
Considering that the characteristics of different polarization states of the fiber core fundamental mode are more easily influenced by the thickness of the cladding tube orthogonal to the electric field direction, the invention provides that the optical fiber adopts four groups of tube wall structures, the circumferential interval of each group of tube wall structures is 90 degrees, so that the fundamental mode x-polarization state FM x is more easily influenced by two groups of tube wall structures in the x direction, and the fundamental mode y-polarization state FM y is more easily influenced by the other two groups of tube wall structures. The thickness of the first x-axis semi-elliptical cladding tube 105 is different from that of the first y-axis semi-elliptical cladding tube 109, and the birefringence of the fundamental mode can be ensured.
By introducing a second x-axis gap 203 in the x-direction, at a distance h 2x, the effective refractive index of the guided cladding mode x-polarization CMx 2x differs from the cladding mode y-polarization CMx 2y by more than 0.001, So that the difference between the effective refractive indices of the fundamental mode x-polarization state FM x and the cladding mode x-polarization state CMx 2x guided by the second x-axis gap 203 is small, while the difference between the effective refractive indices of the fundamental mode y-polarization state FM y and the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203 is large. The second elliptical cladding tube 107 and the rectangular glass wall 108 are introduced in the x-direction to obtain a third x-axis gap 204 and a fourth x-axis gap 205 of similar dimensions such that the two cladding modes CMx 3 and CMx 4, respectively, with smaller differences in effective refractive indices are guided within the two air gaps. the third x-axis gap 204 and the fourth x-axis gap 205 are shaped similarly to the second x-axis gap 203, there is also an effective index difference of greater than 0.001 between the cladding mode x-polarization CMx 3x and the cladding mode y-polarization CMx 3y guided by the third x-axis gap 204 and the cladding mode x-polarization CMx 4x and the cladding mode y-polarization CMx 4y guided by the fourth x-axis gap 205. Because the cladding modes CMx 3 guided by the third x-axis gap 204 and the cladding modes CMx 4 guided by the fourth x-axis gap 205 are close to the outer cladding structure and nodes, there is a relatively high confinement loss. The dimensions of the second x-axis semi-elliptical cladding tube 106, the second x-axis gap 203, the second elliptical cladding tube 107, and the rectangular glass wall 108 are appropriately adjusted such that the cladding mode CMx 2 guided by the second x-axis gap 203 has an effective refractive index similar to the cladding mode CMx 3 guided by the third x-axis gap 204 to increase the confinement loss of the cladding mode CMx 2 guided by the second x-axis gap 203. In the above-described structure, the first and second heat exchangers, The coupling coefficient κ c2c3x of the cladding mode x-polarization CMx 2x guided by the second x-axis gap 203 and the cladding mode x-polarization CMx 3x guided by the third x-axis gap 204 is higher than the coupling coefficient κ c2c3y of the cladding mode y-polarization CMx 2y guided by the second x-axis gap 203 and the cladding mode y-polarization CMx 3y guided by the third x-axis gap 204, Typical values are more than 4 times, resulting in a limiting loss of the cladding mode x-polarization CMx 2x directed by the second x-axis gap 203 that is more than 16 times the limiting loss of the cladding mode y-polarization CMx 2y directed by the second x-axis gap 203. Meanwhile, the coupling coefficients of the fundamental mode x-polarization state FM x and the cladding mode x-polarization state CMx 2x guided by the second x-axis gap 203 and the cladding mode x-polarization state CMx 3x guided by the third x-axis gap 204 are the fundamental mode y-polarization state FM y and the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203, The coupling coefficient of the cladding mode y polarization CMx 3y guided by the third x-axis gap 204 is more than 6 times, so that compared with the fundamental mode y polarization FM y, the fundamental mode x polarization FM x is easier to guide to the cladding mode x polarization CMx 2x guided by the second x-axis gap 203 with larger limiting loss, The third x-axis gap 204 guides leakage of the cladding mode x-polarization CMx 3x, which results in far greater limiting loss of the fundamental mode x-polarization FM x than the fundamental mode y-polarization FM y, and finally achieves single polarization transmission.
Compared with the prior art, the small-mode-field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe has smaller fiber core radius, and theoretical coupling loss is lower than 0.1dB when the small-mode-field single-polarization hollow anti-resonance optical fiber is directly coupled with the traditional solid optical fiber with the fiber core radius of 4.5 mu m; the semi-elliptical cladding tube is utilized to construct a fiber core region, so that the inner space surrounded by the cladding tube and the elliptical cladding tube is larger, the cladding tube and the embedded tube can be additionally placed, multiple glass walls and air gaps are introduced, the transmission loss of a fundamental mode y polarization state FM y lower than 5.5dB/km is realized on the premise of ensuring the small fiber core area, the high-order mode HOM and the cladding mode are guided to be strongly coupled, the loss of the high-order mode HOM is improved, the high-order mode suppression ratio HOMER is more than 35dB, and the single-mode transmission of the fiber core mode is effectively ensured; the thickness of the first x-axis semi-elliptical cladding pipe 105 is set to be different from that of the first y-axis semi-elliptical cladding pipe 109, so that the difference between the effective refractive index of the fundamental mode x-polarization state FM x and the effective refractive index of the fundamental mode y-polarization state FM y is greater than 1.2X10. 10 -4, and higher birefringence is introduced to realize polarization-maintaining characteristics; introducing an elliptical cladding pipe with a glass wall and a larger second x-axis gap in the x-direction, improving the limiting loss of a fundamental mode x-polarization state FM x while ensuring that the limiting loss of a fundamental mode y-polarization state FM y is almost unchanged, and realizing the transmission loss of the fundamental mode y-polarization state FM y with the polarization loss ratio higher than 100 and lower than 20dB/km under the working bandwidth of 52nm, namely single polarization transmission; under the bending state that the bending directions are x, y and 45 degrees and the bending radius is larger than 1.84cm, the transmission loss of the FM y in the y polarization state of the fundamental mode is lower than 12dB/km, the polarization loss ratio PER is higher than 100, and the miniaturization application based on the single-polarization hollow anti-resonance optical fiber is facilitated. In order to illustrate the effectiveness of the method according to the present invention, the following describes the above technical solution of the present invention in detail by means of a specific embodiment, which is as follows:
example 1
The diameter Dc of the core 201 is 10 μm, the spacing g between adjacent first x-axis semi-elliptical cladding tube 105 and first y-axis semi-elliptical cladding tube 109 is 2.1 μm, the minor half axis b 1x of the first x-axis semi-elliptical cladding tube 105 is 20 μm, the thickness t 1x of the first x-axis semi-elliptical cladding tube 105 is 0.54 μm, the distance h 1x of the first x-axis gap 202 is 4.2 μm, The minor half axis b 2x of the second x-axis semi-elliptical cladding tube 106 is 1.8 μm, the thickness t 2x of the second x-axis semi-elliptical cladding tube 106 is 0.58 μm, the distance h 2x of the second x-axis gap 203 is 6.8 μm, The thickness t 3x of the second elliptical cladding tube 107 was 0.61 μm, the minor axis b 3x of the second elliptical cladding tube 107 was 13 μm, the major axis a 3x of the second elliptical cladding tube 107 was 16.2 μm, the thickness t 4x of the rectangular glass wall 108 was 0.63 μm, The minor half axis b 1y of the first y-axis semi-elliptical cladding tube 109 is 20 μm, the thickness t 1y of the first y-axis semi-elliptical cladding tube 109 is 0.44 μm, the distance h 1y of the first y-axis gap 206 is 3.7 μm, The minor half axis b 2y of the second y-axis semi-elliptical cladding tube 110 is 17.6 μm, the thickness t 2y of the second y-axis semi-elliptical cladding tube 110 is 0.52 μm, the distance h 2y of the second y-axis gap 207 is 5.3 μm, the major axis a 3y of the double oval nested tube outer layer 111 is 13 μm, the minor axis b 3y of the double oval nested tube outer layer 111 is 10.8 μm, the thickness t 3y of the double oval nested tube outer layer 111 is 0.53 μm, The major axis a 4y of the double oval nested tube inner layer 112 is 8.2 μm, the minor axis b 4y of the double oval nested tube inner layer 112 is 6.8 μm, the thickness t 4y of the double oval nested tube inner layer 112 is 0.47 μm, The diameter D 5 of the round cladding tube 104 was 5.4 μm, the thickness t 5 of the round cladding tube 104 was 0.62 μm, the minor half axis b 1 of the first elliptical cladding tube 102 was 27 μm, the major half axis a 1 of the first elliptical cladding tube 102 was 29 μm, The thickness t 7 of the first elliptical cladding tube 102 was 0.65 μm, the thickness t 6 of the connecting rod 103 was 2 μm, and the width b 6 of the connecting rod 103 was 6 μm.
At 1550nm, the transmission loss of the fundamental mode y polarization state FM y is 5.45dB/km, the polarization loss ratio PER is 127.8, the difference delta n between the effective refractive index of the fundamental mode y polarization state FM y and the effective refractive index of the fundamental mode x polarization state FM x is 1.24 multiplied by 10 -4, the high-order mode rejection ratio HOMER is 41dB, and the direct coupling loss with a traditional solid optical fiber with the cladding diameter of 125 μm is 0.08dB. As shown in fig. 4 and 5, when the bending directions are x, y and 45 ° directions and the bending radius is greater than 1.84cm, the transmission loss of the fundamental mode y polarization state FM y is lower than 12dB/km, the polarization loss ratio PER is higher than 100, and the higher-order mode rejection ratio is greater than 35dB.
As shown in fig. 5 and 6, when the polarization loss ratio PER is higher than 100 and the transmission loss of the fundamental mode y polarization state FM y is lower than 20dB/km, the high-order mode rejection ratio home is greater than 30dB, which indicates that the embodiment can realize single-mode single-polarization transmission with lower loss.
As shown in fig. 7 and 8, when the distance h 2x of the second x-axis gap 203 increases from 5.5 μm to 7 μm, The coupling coefficient κ m2x of the fundamental mode x-polarization FM x and the cladding mode x-polarization CMx 2x guided by the second x-axis gap 203 and the coupling coefficient κ m2y of the fundamental mode y-polarization FM y and the cladding mode y-polarization CMx 2y guided by the second x-axis gap 203 are both reduced, And |kappa m2x/κm2y|2 >38, while the difference Deltan m2y between the refractive indices of the fundamental mode y-polarization FM y, the cladding mode y-polarization CMx 2y guided by the second x-axis gap 203, and the fundamental mode x-polarization FM x, The ratio of the difference in refractive index deltan m2x between the cladding mode x-polarization states CMx 2x guided by the second x-axis gap 203 is constantly greater than 1.9, and the loss of the cladding mode x-polarization state CMx 2x guided by the second x-axis gap 203 is always higher than the loss of the cladding mode y-polarization state CMx 2y guided by the second x-axis gap 203, So that the fundamental mode x-polarization state FM x has a higher limiting loss than the fundamental mode y-polarization state FM y, and finally, a fundamental mode limiting loss ratio higher than 300 is realized.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. The small-mode-field single-polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding pipe is characterized by comprising an optical fiber structure and an optical fiber gap, wherein under the combined action of the optical fiber structure and the optical fiber gap, the transmission loss of a fundamental mode x polarization state FM x is raised, the transmission loss of a fundamental mode y polarization state FM y is not affected, and further single polarization transmission is realized; wherein,
The optical fiber structure comprises an outer cladding layer (101), a first elliptical cladding tube (102) and a connecting rod (103); the inner space surrounded by the outer cladding layer (101) is provided with a first elliptical cladding pipe (102); the cross section of the outer cladding layer (101) is annular, and a connecting rod (103) is arranged on the inner side of the circular inner ring of the outer cladding layer and is used for connecting the outer cladding layer (101) and the first elliptical cladding pipe (102); the major axis of the first elliptical cladding tube (102) is located on the x-axis and the minor axis is located on the y-axis;
the optical fiber structure further comprises four groups of pipe wall structures which are arranged on the first elliptical cladding pipe (102) and positioned on the inner side of the first elliptical cladding pipe, and each group of pipe wall structures comprises a semi-elliptical cladding pipe; the first group of pipe wall structures and the second group of pipe wall structures have the same structure, are respectively arranged in the positive direction of the x axis and the negative direction of the x axis, and are respectively symmetrical relative to the x axis; the third group of pipe wall structures and the fourth group of pipe wall structures have the same structure, are respectively arranged in the positive direction of the y axis and the negative direction of the y axis, and are respectively symmetrical relative to the y axis;
The optical fiber structure further comprises four round cladding pipes (104) which are arranged on the first elliptical cladding pipe (102) and positioned on the inner side of the first elliptical cladding pipe and have the same structure; the four round cladding pipes are respectively positioned in the first quadrant angular bisector direction, the second quadrant angular bisector direction, the third quadrant angular bisector direction and the fourth quadrant angular bisector direction;
The fiber gap is a space defined by individual components of the fiber structure, either independently or in combination.
2. The half-elliptical cladding-tube-based small mode field single-polarization hollow-core antiresonant optical fiber according to claim 1, wherein the first set of tube wall structures and the second set of tube wall structures respectively comprise a first x-axis half-elliptical cladding tube (105), a second x-axis half-elliptical cladding tube (106) and a second elliptical cladding tube (107) which are arranged on the first elliptical cladding tube (102) in sequence from inside to outside along the radial direction, and a rectangular glass wall (108) which is arranged on the second elliptical cladding tube (107) and is parallel to the y-axis; the second x-axis semi-elliptical cladding pipe (106) is positioned in an inner space formed by the first x-axis semi-elliptical cladding pipe (105) and the first elliptical cladding pipe (102); the second elliptical cladding tube (107) is located in the interior space formed by the second x-axis semi-elliptical cladding tube (106) and the first elliptical cladding tube (102).
3. The half-elliptical cladding-tube-based small mode field single-polarization hollow-core antiresonant optical fiber according to claim 2, wherein the third set of tube wall structures and the fourth set of tube wall structures respectively comprise a first y-axis half-elliptical cladding tube (109), a second y-axis half-elliptical cladding tube (110) and a double elliptical nested tube outer layer (111) which are sequentially distributed from inside to outside along the radial direction and are arranged on the first elliptical cladding tube (102), and a double elliptical nested tube inner layer (112) which is internally arranged on the double elliptical nested tube outer layer (111); the second y-axis semi-elliptical cladding pipe (110) is positioned in an inner space formed by the first y-axis semi-elliptical cladding pipe (109) and the first elliptical cladding pipe (102); the double elliptical nested tube outer layer (111) is located in an interior space formed by the second y-axis semi-elliptical cladding tube (110) and the first elliptical cladding tube (102).
4. A half-elliptical cladding tube based small mode field single polarization hollow core antiresonant fiber according to claim 3, wherein the fiber gap comprises a core (201), the cross section of the core (201) being circular, the circular being tangential to the apex of the first x-axis half-elliptical cladding tube (105) of the first set of tube wall structures, the apex of the first x-axis half-elliptical cladding tube (105) of the second set of tube wall structures, the apex of the first y-axis half-elliptical cladding tube (109) of the third set of tube wall structures, and the apex of the first y-axis half-elliptical cladding tube (109) of the fourth set of tube wall structures.
5. The half-elliptical cladding tube-based small mode field single polarization hollow-core antiresonant fiber of claim 4, wherein the fiber gap further comprises a first x-axis gap (202), a second x-axis gap (203), a third x-axis gap (204), and a fourth x-axis gap (205); wherein the first x-axis gap (202) is surrounded by the first elliptical cladding tube (102), the first x-axis semi-elliptical cladding tube (105) and the second x-axis semi-elliptical cladding tube (106); the second x-axis gap (203) is surrounded by the first elliptical cladding tube (102), the second x-axis semi-elliptical cladding tube (106) and the second elliptical cladding tube (107); the third x-axis gap (204) and the fourth x-axis gap (205) are a half of the inner space of the second elliptical cladding tube (107) and a half of the inner space of the second elliptical cladding tube away from the fiber core (201) which are obtained by dividing the inner space of the second elliptical cladding tube by the rectangular glass wall (108), respectively;
By adjusting the spacing of the first x-axis gap (202), the second x-axis gap (203), the third x-axis gap (204) and the fourth x-axis gap (205), and the dimensions of the second elliptical cladding tube (107), the limiting loss of the fundamental mode x-polarization state FM x can be increased, and single polarization state transmission can be realized.
6. The half-elliptical cladding tube-based small mode field single polarization hollow-core antiresonant fiber of claim 5, wherein the fiber gap further comprises a first y-axis gap (206), a second y-axis gap (207), a third y-axis gap (208), and a fourth y-axis gap (209); wherein the first y-axis gap (206) is surrounded by the first elliptical cladding tube (102), the first y-axis semi-elliptical cladding tube (109) and the second y-axis semi-elliptical cladding tube (110); the second y-axis gap (207) is surrounded by the first elliptical cladding tube (102), the second y-axis semi-elliptical cladding tube (110) and the double elliptical nested tube outer layer (111); the third y-axis gap (208) is defined by a double elliptical sleeve outer layer (111) and a double elliptical sleeve inner layer (112); the fourth y-axis gap (209) is surrounded by the double elliptical nested tube inner layer (112);
The first y-axis semi-elliptical cladding tube (109), the second y-axis semi-elliptical cladding tube (110), the double elliptical nested tube outer layer (111) and the double elliptical nested tube inner layer (112) are used for providing anti-resonance for the small mode field single polarization hollow anti-resonance optical fiber based on the semi-elliptical cladding tube, and can reduce the limiting loss of the fundamental mode y polarization state FM y.
7. The half-elliptical cladding tube-based small mode field single-polarization hollow-core antiresonant fiber of claim 6, wherein the birefringent properties of the fundamental mode y-polarization state FM y and the fundamental mode x-polarization state FM x can be improved by adjusting the thicknesses of the first x-axis half-elliptical cladding tube (105) and the first y-axis half-elliptical cladding tube (109), and the dimensions of the first x-axis gap (202) and the first y-axis gap (206); by adjusting the dimensions of the first y-axis semi-elliptical cladding tube (109), the second y-axis semi-elliptical cladding tube (110), the double elliptical nested tube outer layer (111), the double elliptical nested tube inner layer (112), the first y-axis gap (206), the second y-axis gap (207), the third y-axis gap (208) and the fourth y-axis gap (209), the loss of the higher-order mode HOM can be increased, and single-mode operation can be realized.
8. The half-elliptical cladding tube-based small mode field single-polarization hollow-core antiresonant optical fiber of claim 7, wherein the material of the optical fiber structure is quartz glass.
9. The half-elliptical cladding tube-based small mode field single-polarization hollow-core antiresonant fiber of claim 8, wherein the fiber gap is filled with air.
10. The half-elliptical cladding tube-based small mode field single polarization hollow-core antiresonant optical fiber according to claim 9, wherein the diameter Dc of the core (201) is 9.7 μm to 10.2 μm, the spacing g between adjacent first x-axis half-elliptical cladding tube (105) and first y-axis half-elliptical cladding tube (109) is 1.6 μm to 2.2 μm, the minor half axis b 1y of the first y-axis half-elliptical cladding tube (109) is 16 μm to 22 μm, the thickness t 1y of the first y-axis half-elliptical cladding tube (109) is 0.42 μm to 0.48 μm, The first x-axis semi-elliptical cladding tube 105 has a minor half axis b 1x＝b1y, the first x-axis semi-elliptical cladding tube (105) has a thickness t 1x of 0.50 μm to 0.62 μm, the first x-axis gap (202) has a distance h 1x of 3.5 μm to 4.4 μm, The thickness t 2x of the second x-axis semi-elliptical cladding tube (106) is 0.51-0.65 μm, the distance h 2x of the second x-axis gap (203) is 5.5-7 μm, the ratio of the minor half axis b 3x to the major half axis a 3x of the second elliptical cladding tube (107) 2x is 0.75-0.9, the thickness t 3x of the second elliptical cladding tube (107) is 0.58-0.67 mu m, the thickness t 4x of the rectangular glass wall (108) is 0.6-0.68 mu m, the minor half axis b 1 of the first elliptical cladding tube (102) is 26.8-28.5 mu m, The difference between the major half axis a 1 and the minor half axis b 1 of the first elliptical cladding tube (102) is 1.8-2.5 μm, and the thickness t 7 of the first elliptical cladding tube (102) is 0.5-0.8 μm.
Priority Applications (1)
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| CN118625444A (en) * | 2024-08-12 | 2024-09-10 | 华南师范大学 | Hollow anti-resonance optical fiber |
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| CN118625444A (en) * | 2024-08-12 | 2024-09-10 | 华南师范大学 | Hollow anti-resonance optical fiber |
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