JPS6028606A - Manufacture of infrared ray transmitting fiber - Google Patents

Abstract

PURPOSE:To obtain a uniform core clad interface and to form a protective layer without impairing the surface of a core fiber by fitting a heat shrinkable tube onto the outer circumference of the clad surrounding the core. CONSTITUTION:The outer surface of a core fiber 3 is covered with a roll-pressed clad 2 and sheathed with a heat shrinkable tube 1. A fiber composed of the 3- layer structure of the core 3, the clad 2, and the tube 1 by shrinking it by properly heating the tube 1. Any material can be used for the core 3 and the clad 2 so long as they are small in loss of absorption in the IR region, and they can be constituted by combining ones high and low in the refractive index. Halides, such as TlBr, TlCl, AgBr, AgCl, CsCl, and CsBr, are suitable for the core fiber to be used here. A heat-shrinkable ''Teflon'' tube and a polyvinyl chloride tube, etc., heat shrink by 30% at low temps. up to the max. temp. of 250 deg.C, and hence, they are useful as the tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a step-index type infrared transmission fiber having a core and a cladding layer.

[Technical background of the invention and its problems]

The development of fibers that transmit infrared light has progressed rapidly in recent years, and various compositions have been proposed, and associated characteristic manufacturing methods are being investigated.

For example, polycrystalline fibers made by hot extrusion of thallium halide or silver halide, and single-crystalline fibers of alkali halide are produced by EFG method, MPD method, etc., and practical optical loss values can be obtained in both cases. ing. These fibers are being applied to laser processing machines and medical laser scalpels for transmitting high-power infrared light such as CO2 laser light. A step-index fiber is a core made of polycrystalline or single crystal, which is covered with a cladding layer that has a lower refractive index than the core.
Light is transmitted by repeated reflections at the interface between the core and cladding. The method of coating the Kushirad layer on these step-index fibers varies depending on the fiber composition and other factors, but in a typical example, the following weight is.

For example, in the case of polycrystalline fibers, it is common to first form a preform for extrusion in which the core is covered with a cladding, and then convert it into fibers by hot extrusion. There is a method in which the entire beam is passed through a crystal melt having a low refractive index.

However, in the hot extrusion method, the core crystal and the clad crystal interlock with each other during extrusion, resulting in grain growth, so the core clad surface does not become smooth and light transmission is disrupted.
There were some drawbacks. In addition, all crystal melts with low melting point and low refractive index
When dealing with IJ11, use c5 to the core part or lakrasod part.
It was difficult to obtain a smooth core-clad interface due to the denting.

(One of the items that an optical transmission fiber should have is a protective layer coating.The protective layer is a coating made of resin or low melting point metal on the outer surface of the fiber, and prevents mechanical and chemical deterioration of the fiber.) The purpose is to prevent

However, in reality, it is difficult to coat the fiber with a protective layer without damaging the outer surface of the fiber, and a method of coating the protective layer that can be applied while maintaining a uniform outer surface has been desired.

This is because damaging the outer surface of the fiber has an adverse effect on the transmission characteristics of the fiber.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks, and provides a method for manufacturing an infrared transmission fiber that has a uniform core-clad interface and can be coated with a protective layer without damaging the fiber surface. It is something to do.

[Summary of the invention]

In the present invention, a cladding layer having a refractive index lower than that of the core is arranged around the outer periphery of a core made of a single crystal or polycrystalline fiber, and a heat-shrinkable tube is further arranged around the outer periphery of the cladding, and then the heat-shrinkable tube is This is a manufacturing method of an infrared transmission fiber in which a reinforcing layer is formed by shrinking the fiber. Place it inside the heat shrink tube (1). Thereafter, the heat-shrinkable tube is shrunk by an appropriate heat treatment, and as shown in FIG. 2, the fiber is made up of 14 triple layers of core and crass tubes (i.e., insulation layer).

According to the present invention, the smoothness of the core-clad interface can be maintained, and the outer surface of the clad is not damaged during coating with a protective layer. Furthermore, the core cladding and the protective layer can be covered only by the process of shrinking the island-like +4hi tube as the protective IN, which is simpler than the conventional process of separating the core and cladding, and the cladding and protective layer, respectively. and can be implemented in a short period of time.

In the present invention, the materials of the core and cladding can be selected from materials with low absorption loss in the infrared region, and can be constructed by combining high and low refractive indexes.

However, in order to use it as a fiber, it needs to be non-cleavable, rich in flexible VC, transparent in the infrared region, and highly flexible, such as Tll3r and TIJOII.

AgBr, Ag0A! , OsI, OsBr, or a mixture thereof. Also, if the flexibility of the resin material is not sufficient, the cladding layer should be made thinner. Alternatively, it is effective to carry out the roll rolling process while heating at 77 Fl at a temperature below the Tuffman temperature. In addition, the heat-shrinkable tube that serves as the protective layer only needs to be made of a material with little chemical and mechanical deterioration and have removability; for example, heat-shrinkable Teflon tubes and vinyl chloride-I can be used at temperatures as low as 250°C or less. At temperature ~3
It is useful as it earns 0%.

[Embodiments of the invention]

A detailed explanation will be given below based on examples.

First, an OsI single crystal fiber was manufactured by the MPIJ method.

# Using OsI crystal purified by Seigi method, N2
:l(2; 1:l (vol ratio)) was melted by resistance heating with a gsten heater in a # atmosphere of 1:l (vol ratio).

The OsI melt flowing out from the orifice of the crucible for the MPD method was received by a yuzu crystal, and the melt was turned into a single crystal fiber while gradually pulling down the seed crystal. An X-ray Laue photograph was taken of part of the fiber, confirming that it was a single crystal. A U sl of 0.3ilirN thickness was roll-formed around the obtained 7-eye bar with a diameter of 1.2Cta and a length of 80Cta.
(+r Arrange the thin plate at 120 in Fig. 1, and further set the outer diameter to 3,
0, inner diameter 2.6+; This was heated from one end with a hot air gas to shrink the heat-shrinkable tube, resulting in a 2.2-u-diameter plastic tube consisting of a core and a carbon protective layer (heat-shrinkable defroner tube).

This fiber's 002 laser light (wavelength 10.6μI
The transmission loss of n) was measured and was 0.82 dB/I.
A Cs with a diameter of 1.10 mm and a length of l m obtained in the same way with an and low loss.
A 0s13r thin plate having a thickness of 0.15i+g, which was roll-formed from a No. At this time, the tube has an outer diameter of 2.4
TIm, sweetfish with an inner diameter of 2.0 was used. After insertion, the fibers were heated with a honoto air gas to shrink the nape and form a fiber with an outer diameter of 1.6 mm. The CO□ laser light transmission loss of this fiber was as low as 0.78 dB/m2, and even if the shift layer was made thinner, the transmission loss was not affected.

[Brief explanation of the drawing]

FIG. 1 is a +11r side view of a heat-shrinkable tube made of the VC of the present invention at a pre-shrinkage stage. FIG. 2 is a cross-sectional view after shrinkage. Figure 3 shows the horizontal 111r plane of the heat-shrinkable tube in the example before it is harvested. 1: Kensuke (and 1 other person) 1st Figure 2 U (-mi Figure 8/Z 3 A

Claims (1)

[Claims] (1) Infrared transmission fiber having a core made of polycrystal or single crystal, a cladding portion having a small refractive index around the core, and a protective layer around the outside of the cladding. 1. A method for producing an infrared ray 4 fiber, characterized in that a heat-shrinkable tube is used as the protective layer, and the protective layer is formed by heat-shrinking the tube. 2) Claim 1t1 No. 1, characterized in that the shrinkage of the heat-shrinkable tube is carried out at a temperature of 250°C or less.
A method for manufacturing an infrared transmission fiber mounted on a 1i pin. 3) Infrared light 1 described in item 2 of the so-called patent, characterized in that the material of the heat-shrinkable tube is Teflon/or vinyl chloride.
A method for producing fibers to be fed to.・1) Core and gland materials are Osl and 0sBr. 4. The method for manufacturing an infrared transmission fiber according to claim 3, characterized in that the fiber is made of a single crystal or a mixture of crystals selected from TRI, TlBr, kgBr, and kgcll.