CN102368102A - Intermediate infrared optical fiber and manufacturing method thereof - Google Patents

Abstract

The invention is applicable to the field of optical fiber technology, and provides a mid-infrared optical fiber and a manufacturing method thereof. The mid-infrared optical fiber has a quartz cladding and a core made of mid-infrared glass material wrapped in the cladding. The manufacturing method is divided into two steps: the first step is to manufacture hollow-core optical fiber preform rod by PCVD method and wire drawing to produce hollow-core optical fiber; the second step is to inject molten mid-infrared glass into the hole of the hollow-core optical fiber. Since the cladding material of the mid-infrared optical fiber provided by the present invention is quartz, when it is welded with quartz optical fiber, the existing optical fiber cutting and welding equipment can be directly used for convenient and quick operation, so it is easier to weld; and the material of the fiber core is Mid-infrared glasses with high nonlinear coefficient, such as chalcogenide glass, telluride glass and fluoride glass, are suitable for nonlinear applications, such as generating mid-infrared broadband supercontinuum; the mid-infrared fiber can use erbium or thulium-doped fiber Laser pumping to realize all-fiber mid-infrared broadband light source.

Description

A kind of mid-infrared optical fiber and its manufacturing method

technical field

The invention belongs to the field of optical fiber technology, and in particular relates to a mid-infrared photon optical fiber capable of low-loss fusion splicing with common silica optical fibers and a manufacturing method thereof.

Background technique

Because mid-infrared glass has a relatively high light transmission wavelength range (generally 2-16μm), and nonlinear refractive index (two orders of magnitude higher than ordinary quartz glass), it is used in mid-infrared laser conduction, nonlinear optics and other fields. Extensive, such as medical surgery (such as laser ablation surgery), thermal image transmission, or developed into a mid-infrared ultra-broadband light source. The mid-infrared ultra-broadband light source also has high technical content and broad application prospects, and can be applied in many fields such as OCT (Optical Coherence Tomography, optical coherence tomography), active hyperspectral imaging, molecular spectroscopy, biotechnology, and environmental monitoring. . It can also be applied to safety and environmental monitoring, such as: explosive gas detection system, detecting methane and other explosive gases; combustion efficiency and exhaust emission monitoring system, measuring CO, CO2, etc.; toxic gas detection, water vapor concentration in the atmosphere, etc. In recent years, the research on mid-infrared fiber has always been a frontier topic in the field of fiber optics. New designs have continuously improved the performance of mid-infrared fibers, such as using the waveguide structure of photonic crystal fibers to adjust the dispersion and birefringence characteristics of mid-infrared fibers. In recent years, the research on mid-infrared optical fibers has made great progress, and the resulting mid-infrared ultra-broadband spectral range has reached several microns.

However, the general mid-infrared optical fiber has the characteristics of low softening temperature and brittle quality, so it is difficult to weld with silica optical fiber. This is because the melting point of general fused silica glass reaches above 1800 degrees, while the melting point of general mid-infrared glass is only a few hundred degrees. The difference is huge. General erbium (or thulium) doped fiber lasers are made of silica fibers, and it is difficult to fuse these lasers with mid-infrared fibers to produce an all-fiber mid-infrared ultra-broadband light source, which limits its practical application.

Contents of the invention

The technical problem to be solved by the present invention is to provide a mid-infrared optical fiber, aiming at realizing the all-fiber fusion splicing of the mid-infrared optical fiber and the silica optical fiber.

The present invention is achieved in this way, a mid-infrared optical fiber, the mid-infrared optical fiber has a silica cladding and a mid-infrared glass core wrapped in the cladding.

Further, the mid-infrared glass is chalcogenide glass, telluride glass or fluoride glass.

Further, the cladding includes an outer cladding of fused silica, an inner cladding of a fluorine-doped region and a germanium dioxide-doped region.

The present invention also provides a method for making a mid-infrared optical fiber, comprising the following steps:

Step A: Make a preform. The structure of the preform is from the outside to the inside respectively a fused silica area, a fluorine-doped glass depression area, a germanium dioxide-doped glass area, and a core area as an air hole along the direction of light propagation. Draw the preform to obtain a hollow-core silica optical fiber with a hole in the middle;

Step B: Insert one end of the hollow-core silica fiber known in step A into a closed container filled with molten mid-infrared glass; fill the closed container with an inert gas, and inject the molten mid-infrared glass into the fiber with the pressure of the inert gas in the core hole.

Further, the mid-infrared glass is sulfide glass, chalcogenide germanium glass, holide glass or fluoride glass.

Further, the step A specifically prepares the preform by the MCVD method or the PCVD method.

Further, the step A specifically draws the preform through a wire drawing tower.

Since most of the mid-infrared optical fiber provided by the present invention is made of quartz, when it is fused with quartz optical fiber, the existing optical fiber cutting and fusion splicing equipment can be directly used for convenient and quick operation, so it is easier to weld, thereby realizing mid-infrared optical fiber and All-fiber fusion splicing of silica fiber, which can be directly pumped by existing silica fiber laser. In addition, fluorine can also be doped in the quartz cladding, which improves the nonlinear refractive index of the fiber to a certain extent and broadens the light transmission range, and by injecting mid-infrared glass, especially chalcogenide glass, into the core hole, and The overall nonlinear refractive index coefficient can be further improved, and the light transmission range can be further broadened.

Description of drawings

Fig. 1 is a schematic diagram of an end section of a mid-infrared optical fiber provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of a manufacturing method of a mid-infrared optical fiber provided by an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

In the embodiment of the present invention, by making a hybrid glass-type mid-infrared optical fiber with a quartz cladding and a mid-infrared glass core, the all-fiber fusion splicing of an available mid-infrared optical fiber and a silica optical fiber is realized.

The mid-infrared optical fiber provided by the embodiment of the present invention has a silica cladding and a mid-infrared glass core 2 wrapped in the cladding. FIG. 1 is a specific example of the present invention. The cladding includes a fused silica outer cladding 11, The cladding layer 12 and the germanium dioxide-doped region 13 are included in the region. By setting the cladding 12 in the fluorine-doped region in the cladding, the nonlinear refractive index coefficient of the optical fiber is improved to a certain extent and the light transmission range is widened.

The above-mentioned mid-infrared glass can be chalcogenide glass, telluride glass or fluoride glass, and the chalcogenide glass can be AS ₂ S ₃ and AS ₂ Se ₃ , which can further improve the overall nonlinear refractive index and further broaden the light transmission range .

Further, by setting the germanium dioxide-doped region 13 in the cladding, a germanium dioxide high-refractive index region 13 can be formed. Even if mid-infrared glass is not injected into the middle hollow core, this hollow core fiber can also be used as an independent transmission Optical waveguides, where light is guided in regions of high refractive index in germanium dioxide.

Specifically, the diameter of the above-mentioned mid-infrared glass core 2 can be designed between 2 um and 6 um, the thickness of the cladding 12 in the fluorine-doped region can be designed to be 2 um, the refractive index depression is 0.008, and the low refractive index region acts as a cladding ; while the thickness of the ring-shaped germanium dioxide-doped region 13 is 1-3um, correspondingly, the refractive index can be increased to: 0.02-0.035. Here, the advantage that the refractive index is higher than that of the fluorine-doped region is that even if the core is not filled with mid-infrared glass with a higher refractive index, it is air, and the light can be limited to conduct in the germanium-doped region; that is, the cladding 12 in the fluorine-doped region can make The refractive index of the fused silica decreases, and the germanium dioxide-doped region 13 can increase the refractive index of the fused silica.

The above-mentioned mid-infrared optical fiber can be manufactured by high-pressure injection method, and the manufacturing method includes the following steps:

Step A: Make a preform. The structure of the preform is from the outside to the inside respectively a fused silica area, a fluorine-doped glass depression area, a germanium dioxide-doped glass area, and a core area as an air hole along the direction of light propagation. The preform is drawn to obtain a hollow-core silica optical fiber with a hole in the middle.

Step B: Insert one end of the hollow-core silica fiber known in step A into a closed container filled with molten mid-infrared glass; fill the closed container with an inert gas, and inject the molten mid-infrared glass into the fiber with the pressure of the inert gas in the core hole.

Wherein, the above-mentioned mid-infrared glass may be sulfide glass, chalcogenide germanium glass, holide glass or fluoride glass, and the inert gas may be realized by helium or argon.

Fig. 2 is a specific implementation of the above manufacturing method, wherein the mid-infrared glass is an example of chalcogenide glass. Referring to FIG. 2 , chalcogenide glass is placed in the airtight container A, and the quartz optical fiber C obtained through step A is inserted into the cover of the airtight container A, and the socket is guaranteed to be sealed. Then vacuumize the closed container A to prevent the mid-infrared glass from reacting with oxygen when it melts, resulting in glass denaturation, and then heat the closed container A through the furnace B until the chalcogenide glass is in a molten state. As mentioned above, the quartz optical fiber C There is a hole inside the fiber core along the direction of light propagation, and the silica fiber C is inserted into the molten chalcogenide glass. Inject the inert gas D into the airtight container A. When the air pressure in the airtight container A reaches a certain level, the molten chalcogenide glass will be injected into the hole of the quartz optical fiber C under high pressure. Different injection lengths can be realized by adjusting the air pressure of the airtight container A through the barometer.

Most of the above-mentioned mid-infrared optical fibers are made of quartz. When splicing with quartz optical fibers, the existing optical fiber cutting and fusion splicing equipment can be directly used for convenient and quick operation, so it is easier to splice, so as to realize the full optical fiber of mid-infrared optical fibers and quartz optical fibers. This fiber can be directly pumped with an existing quartz-silica fiber laser.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (7)

1. a middle infrared optical fiber is characterized in that, said middle infrared optical fiber has quartzy covering and the middle infrared glass fibre core that is wrapped in the said covering.

2. middle infrared optical fiber as claimed in claim 1 is characterized in that, said middle infrared glass is chalcogenide glass, tellurite glass or fluoride glass.

3. middle infrared optical fiber as claimed in claim 1 is characterized in that, said covering comprises the fused quartz surrounding layer, mixes fluorine district inner cladding and mixes the germanium dioxide district.

4. the method for making of a middle infrared optical fiber is characterized in that, comprises the steps:

Steps A: make a prefabricated rods; The prefabricated rods structure is respectively the fused quartz district from outside to inside, mix fluorine glass refraction bogging down area, mix the germanium dioxide glass region, core area is an airport along optical propagation direction; With prefabricated stick drawn wire, obtain middle porose hollow silica fibre;

Step B: an end of the hollow silica fibre that steps A is known inserts in the closed container of the middle infrared glass that fills fusion; To charging into inert gas in the said closed container, the middle infrared glass of fusion is injected in the hole of fibre core with inert gas pressure.

5. the method for making of middle infrared optical fiber as claimed in claim 4 is characterized in that, said middle infrared glass is chalcogenide glass, tellurite glass or fluoride glass.

6. the method for making of middle infrared optical fiber as claimed in claim 4 is characterized in that, said steps A specifically gets prefabricated rods through MCVD method goods PCVD legal system.

7. the method for making of middle infrared optical fiber as claimed in claim 4 is characterized in that, said steps A is specifically passed through wire-drawer-tower with prefabricated stick drawn wire.

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