JPS58142305A - Fiber for optical transmission - Google Patents

Abstract

PURPOSE:To provide a fiber for optical transmission having good low temp. characteristics and side-pressure resistance characteristics by coating resin layers of low Young's modulus and high Young's modulus successively on an optical fiber strand of guartz glass. CONSTITUTION:A coating layer 3 of a silicone resin is coated on the outside of a pure strand of, for example, 125mum outside diameter consisting of a core part 1 and a clad part 2 which consist essentially of quartz glass differing in refractive index from each other, whereby a strand having 300mum outside diameter is formed. A resin layer 4 of nylon or the like having low Young's modulus of 5,000kg/cm is coated to 100mum thickness on the outside thereof, and further nylon or the like having Young's modulus of as high as 12,000kg/cm is coated to 200mum thickness on the outside thereof.

Description

Detailed Description of the Invention (a) Technology of the Invention Publicly Funded The present invention relates to an optical transmission fiber mainly composed of quartz glass used in optical communications, and particularly relates to an optical transmission fiber having good low temperature resistance and lateral pressure resistance. This is related to transmission fiber.

(To) Prior Art and Problems Conventional optical transmission fibers that are mainly composed of silica glass and used for optical communications have a core and a cladding that have different Kl refractive indexes.

In order to prevent minute scratches or defects from occurring on the surface of the glass fiber, and to prevent the strength from decreasing due to the growth of these defects, and to improve the tensile strength of 9 and bending strength of 1 and to facilitate handling, S/
The optical transmission fiber described above has a structure in which a primary coating is made of IJ resin, etc., and a secondary coating is made of polyamide resin (nylon) on top of it. It is important that the loss characteristics are stable even against temperature changes in the stress agent from the outside. For example, it is desired that the increase in loss in a low-temperature environment of -30° C. be 1 dB/km or less. However, in reality, when the secondary coating, such as polyamide resin (nylon), is cooled to a low temperature, it contracts, causing the pure optical fiber made of glass fiber to bend slightly, resulting in a transmission loss of several d.
El/1an may also increase,
There was also a problem that the characteristics against lateral pressure were not satisfactory.

(0) Purpose of the Invention It is an object of the present invention to provide a novel optical transmission fiber which overcomes the above-mentioned conventional problems and has good low-temperature properties and good lateral pressure properties.

Structure of the Invention In order to achieve the above-mentioned object, the optical transmission fiber of the present invention has an optical fiber having quartz glass as its main component.
It is characterized by having a structure in which a resin layer having a low Young's modulus and a resin layer having a high Young's modulus are sequentially coated.

(e) Embodiments of the invention Embodiments of the invention will now be described in detail with reference to the drawings.

The figure is a cross-sectional view showing the structure of an embodiment of the optical fiber for optical transmission according to the present invention, in which 1 is a core portion, and 2 is a cut-through portion, each of which is made of glass whose main component is quartz. The outer periphery is coated with a coating layer 8 made of silicone resin to constitute an optical fiber wire. A low Young's modulus resin layer 4 made of polyamide resin (nylon) or polyethylene, which has a low shrinkage rate at low temperatures, or polyethylene, is formed around the outer periphery of the optical fiber, and a high Young's modulus resin layer 4 is further formed on the side 1 for reinforcement against pressure. A high Young's modulus resin Jl! made of polyamide resin (nylon), for example, has a high Young's modulus. ls
or coated as shown.

That is, to explain the above embodiment in more detail, the outer periphery of a pure optical fiber having an outer diameter of 125 μm, for example, is composed of a core portion l and a cutulad portion 2, which are mainly composed of quartz glass having different refractive indexes. A coating layer 8t- made of silicone resin
The coating forms an optical fiber with an outer diameter of 800 μm, and the outer periphery of the optical fiber has a Young's modulus of 5000.
A low Young's modulus resin layer 4 made of, for example, N1940 type polyamide resin (nylon) manufactured by Ohcell Co., Ltd.
It is coated to a thickness of 0 μm, and the Young's modulus is
For example, L19 manufactured by Ohcell Co., Ltd. has a high value of 12000 WaA.
If the structure is coated with a high Young's modulus resin layer made of type 40 polyamide resin (nylon) to a thickness of δt - 200 μm, the shrinkage force will be small at low temperatures with respect to the central optical fiber strand, and it will be relatively soft. The low Young's modulus resin layer 4 serves as a relaxation layer against external stress and the large shrinkage force of the high Young's modulus resin layer due to temperature changes, and the high Young's modulus at the outermost periphery acts as a relaxation layer against lateral pressure. The resin layer 5 provides sufficient protection.

Therefore, in the optical transmission fiber configured as described above, the loss increasing power at low temperature (-80°C) is, for example, 0.2.
dB/km, and the loss increase due to lateral pressure is 0.5 dB/km.
The loss characteristics of the fan were reduced by approximately one order of magnitude compared to the loss characteristics of conventional optical transmission fibers.

(G) Effects of the Invention As is clear from the above explanation, the optical transmission fiber according to the present invention has a resin layer having a low Young's modulus and a resin layer having a high Young's modulus sequentially laminated around the outer periphery of the optical fiber. This structure has the advantage that the transmission loss characteristics against lateral pressure and temperature changes are significantly improved to about l/l O compared to conventional ones, and is particularly suitable for optical transmission used in low-temperature environments. Extremely effective when applied to optical fibers, etc.

[Brief explanation of the drawing]

The figure is a cross-sectional view showing one embodiment of the optical transmission fiber according to the present invention. In the figure, 1 is a core portion, 2 is a cladding portion, 8 is a resin coating layer, 4 is a low Young's modulus resin layer, and 5 is a high Young's modulus resin layer.

Claims (1)

[Claims] 1. An optical transmission fiber characterized in that the outer periphery K of an optical fiber strand mainly composed of quartz glass is coated with a resin layer having a low Young's modulus and a resin layer having a high Young's modulus in order.