CN112666649A

CN112666649A - Solid core anti-resonance optical fiber for realizing medium infrared band cut-off-free single mode transmission

Info

Publication number: CN112666649A
Application number: CN202011464239.6A
Authority: CN
Inventors: 史伟; 张帅; 孙帅; 盛泉; 姚建铨
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2020-12-11
Filing date: 2020-12-11
Publication date: 2021-04-16

Abstract

The invention provides a solid core anti-resonance optical fiber for realizing medium infrared band cut-off-free single mode transmission, which is characterized by comprising a solid core fiber core and a tubular outer cladding layer coated outside the solid core fiber core, wherein six round solid core small tubes coated with the tubular inner cladding layer are distributed in the solid core fiber core, and the round solid core small tubes are uniformly distributed in the solid core fiber core in a surrounding way without contact with each other to form a node-free structure; the solid core fiber core and each round solid small tube are made of materials with lower refractive indexes, and the tubular outer cladding layer and the tubular inner cladding layer are made of materials with higher refractive indexes, so that a completely solid optical fiber structure is formed.

Description

Solid core anti-resonance optical fiber for realizing medium infrared band cut-off-free single mode transmission

Technical Field

The invention relates to a single-mode solid-core optical fiber based on an anti-resonance characteristic, belonging to the field of special optical fiber design and simultaneously belonging to the field of mid-infrared laser transmission design.

Background

The common solid-core silica fiber is used as a traditional medium for transmitting light waves, and has a great number of intrinsic defects in practical application, such as nonlinear effect, dispersion effect, photo-induced damage effect, ultraviolet and mid-infrared band light-blocking effect and the like. These intrinsic physical problems are difficult to solve effectively in the framework of conventional optical fibers, and thus become fundamental obstacles that greatly restrict the forward development of optical fiber transmission technology. Therefore, it is necessary to design a new optical fiber with excellent transmission performance and stable material and structural properties.

The first generation of hollow core optical fibers based on the photonic band gap effect made great progress both experimentally and theoretically in the early 21 st century. But the structure of the optical fiber is complex, and the transmission loss of the transmission optical fiber can not break through the limit of the surface scattering loss, so that the transmission bandwidth is narrow, and the laser damage threshold is not high enough. With the development of the hollow-core anti-resonant fiber, many researchers optimize and design the hollow-core anti-resonant fiber with wide transmission bandwidth and low transmission loss. However, the design and drawing process of the hollow-core optical fiber structure are complicated, and the hollow-core structure is easy to collapse and has no good structural stability, so that the real large-scale batch production is difficult to realize.

Therefore, based on the design concept of the anti-resonance optical fiber, the invention provides the solid anti-resonance optical fiber with good non-cutoff single-mode transmission characteristic, which can be used for excellent single-mode transmission of middle-infrared band laser, provides a new method and thought for the design of a large-core-diameter single-mode active optical fiber and the research of the nonlinear characteristics of the large-core-diameter single-mode active optical fiber, and also expands the design field of the anti-resonance optical fiber and promotes the further development of the solid optical fiber in the laser transmission field.

Disclosure of Invention

The invention aims to provide a design method of a solid anti-resonance optical fiber, which realizes the non-cutoff single-mode transmission of mid-infrared band laser by filling materials with different refractive indexes and controlling the size of structural parameters of the optical fiber. The technical scheme of the invention is as follows:

a solid core anti-resonance optical fiber for realizing medium infrared band cut-off-free single mode transmission is characterized by comprising a solid core fiber core and a tubular outer cladding layer covering the outside of the solid core fiber core, wherein six round solid core small tubes with tubular inner cladding layers covering the outside are distributed in the solid core fiber core, and the round solid core small tubes are uniformly distributed in the solid core fiber core in a surrounding way without contact with each other to form a node-free structure; the solid core fiber core and each round solid small tube are made of materials with lower refractive indexes, and the tubular outer cladding layer and the tubular inner cladding layer are made of materials with higher refractive indexes, so that a completely solid optical fiber structure is formed.

Furthermore, the round solid small tubes are uniformly distributed in the solid fiber core in a surrounding way.

Further, according to the wavelength of the mid-infrared band to be transmitted and the refractive index of the two selected materials, the length L of the anti-resonance period is determined, and the thickness of the tubular inner cladding is determined through optimized design.

Further, the refractive index of the solid core and the round solid small tube is n₂2.4158; the refractive index of the tubular outer cladding and the tubular inner cladding is n₁2.8034, the thickness of the tubular inner cladding is 0.52 μm.

Further, the central diameter of the solid core of the solid core anti-resonance optical fiber is 20 μm, and the minimum gap between the tubular inner cladding and the tubular outer cladding of the solid core anti-resonance optical fiber is 2 μm. The thickness of the tubular outer cladding is 5 μm. The diameter of the round solid small tube is 13.6 mu m.

The solid anti-resonance optical fiber is characterized in that when laser is transmitted in the structure, the laser and the tubular inner cladding generate anti-resonance action, so that a laser field is limited in the solid fiber core and transmitted in a single-mode, and the solid anti-resonance optical fiber has excellent laser single-mode transmission characteristics; compared with a hollow fiber, the solid anti-resonance fiber is very stable in overall structure and not easy to collapse, and the structure can be easily processed and manufactured by drilling and filling materials on a common solid fiber base material, so that large-scale batch production can be performed by industrialized drawing, the market prospect is good, the function realization mode is simple, and a good technical conversion foundation is achieved.

Drawings

FIG. 1 is a schematic structural diagram of a solid core antiresonant optical fiber for implementing cut-off-free single mode transmission according to the present invention;

FIG. 2 is a schematic diagram illustrating the variation of the antiresonance period of the solid antiresonant fiber in the embodiment of FIG. 1;

FIG. 3 shows the fundamental mode HE of the embodiment of FIG. 1 when the optical fiber structure has different diameter d of the round solid-core small tube 3₁₁And higher order mode TE₀₁Schematic diagram of the variation of the transmission loss of (1);

FIG. 4 shows a fundamental mode HE of the optical fiber structure of the embodiment of FIG. 1 when transmitting laser beams with different wavelengths₁₁And higher order mode TE₀₁Schematic diagram of the transmission loss variation.

Fig. 5 is a schematic diagram of field intensity distribution when the optical fiber structure in the embodiment of fig. 1 realizes very good single-mode transmission.

Reference numerals: 1-solid core, 2-tubular outer cladding, 3-round solid core small tube, 4-tubular inner cladding

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 1 is a schematic structural diagram of a solid core antiresonant optical fiber for implementing non-cutoff single-mode transmission according to the embodiment of the present invention. The fiber core structure comprises a tubular outer cladding layer 2, a solid fiber core 1, six round solid small tubes 3 embedded in the solid fiber core 1 and a tubular inner cladding layer 4 wrapping the round solid small tubes 3, wherein the six round solid small tubes 3 are uniformly distributed in the solid fiber core 1 in a surrounding mode without contact, and a node-free structure is formed. Laser with the wavelength of lambda being 3 mu m is led into the structural optical fiber, and the non-cutoff single-mode transmission characteristic of the designed optical fiber structure in the middle infrared band is proved by a software simulation mode.

Wherein the solid core 1 and the round solid small tube 3 are made of material As with lower refractive index₂S₃Filling with a refractive index n₂2.4158; the tubular outer cladding 2 and the tubular inner cladding 4 are made of a material As having a high refractive index₂Se₃Filling with a refractive index n₁2.8034, thereby forming an optical fiber structure that is entirely filled with solid core material.

As shown in FIG. 1, the solid core 1 has a large central diameterSmall D_coreSet to 20 μm; the distance G between the tubular inner cladding 4 and the tubular outer cladding 2 is set to be 2 μm; thickness T of the tubular envelope 2_exSet to 5 μm. The anti-resonance period length L of the solid core anti-resonance fiber structure can be obtained as 1.055 μm according to the formula (1):

whereby the thickness T of the tubular inner cladding 4 is set to

The transmission loss of the laser light in this fiber is at a minimum.

FIG. 2 is a schematic diagram of an antiresonance period of a solid antiresonant fiber obtained by simulation in the example. It can be found that the solid core antiresonant fiber designed by the invention has obvious antiresonant characteristic, the antiresonant period L is 1.05546 μm, the first antiresonant point is located at 0.5277 μm, and the result is consistent with the theoretical value calculated by the formula (1).

FIG. 3 shows a fundamental mode HE of the solid-core antiresonant optical fiber structure of the embodiment with different diameter d of the circular solid-core small tube 3₁₁And higher order mode TE₀₁The respective transmission losses are illustrated schematically. It can be seen that the fiber structure designed by the present invention has very good non-cutoff single-mode transmission characteristics, especially when d is 13.6 μm, the transmission loss of the fundamental mode is about three orders of magnitude lower than that of the high-order mode, and even if the diameter size of the circular solid small tube 3 changes, the transmission loss of the fundamental mode remains substantially unchanged, thereby achieving excellent single-mode transmission.

FIG. 4 is a diagram illustrating a fundamental mode HE of a solid-core anti-resonant fiber structure in an embodiment when transmitting laser beams with different wavelengths₁₁And higher order mode TE₀₁Schematic diagram of the variation of the transmission loss of (1). As can be seen, in the intermediate infrared band of 2.5-3.5 μm, the solid core anti-resonance optical fiber with the structure has better transmission characteristics, the transmission loss of the fundamental mode is about two orders of magnitude lower than that of the high-order mode, and therefore, the solid core anti-resonance optical fiber can be used for transmitting laser in the intermediate infrared band in a good single-modeAnd (6) inputting.

Fig. 5 is a schematic diagram of field intensity distribution when the solid core antiresonant fiber structure in the embodiment realizes excellent single-mode transmission. Under the influence of the anti-resonance characteristic, the solid core optical fiber structure designed by the invention well limits laser inside the optical fiber core, and realizes excellent single-mode transmission.

The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto and changes may be made without departing from the scope of the invention as defined by the claims and their equivalents.

Claims

1. A solid core anti-resonance optical fiber for realizing medium infrared band cut-off-free single mode transmission is characterized by comprising a solid core fiber core and a tubular outer cladding layer covering the outside of the solid core fiber core, wherein six round solid core small tubes with tubular inner cladding layers covering the outside are distributed in the solid core fiber core, and the round solid core small tubes are uniformly distributed in the solid core fiber core in a surrounding way without contact with each other to form a node-free structure; the solid core fiber core and each round solid small tube are made of materials with lower refractive indexes, and the tubular outer cladding layer and the tubular inner cladding layer are made of materials with higher refractive indexes, so that a completely solid optical fiber structure is formed.

2. The solid core antiresonant fiber for uninterrupted single mode transmission according to claim 1, wherein the circular solid small tubes are uniformly distributed around the solid core with respect to each other.

3. The solid core antiresonant optical fiber for cutoff-free single-mode transmission according to claim 1, wherein the antiresonant period length L is determined according to the mid-infrared band wavelength to be transmitted and the refractive index of the two selected materials, and the thickness of the tubular inner cladding is determined through optimized design.

4. The solid core antiresonant optical fiber for uninterrupted single-mode transmission according to claim 1, wherein the refractive index of the solid core and the circular solid core tubule is n₂2.4158; the refractive index of the tubular outer cladding and the tubular inner cladding is n₁2.8034, the thickness of the tubular inner cladding is 0.52 μm.

5. The solid core antiresonant fiber for the cutless single mode transmission according to any of claims 1-4, wherein the solid core of the solid core antiresonant fiber has a central diameter of 20 μm, and the minimum gap between the tubular inner cladding and the tubular outer cladding of the solid core antiresonant fiber is 2 μm.

6. The solid core antiresonant optical fiber for uninterrupted single mode transmission according to any of claims 1-5, wherein the tubular outer cladding has a thickness of 5 μm.

7. The solid core antiresonant fiber for endless single mode transmission according to any of claims 1-6, wherein the diameter of said circular solid core small tube is 13.6 μm.