JPH01134405A - Manufacture of optical fiber coupler - Google Patents

Abstract

PURPOSE:To improve the consistency in coefficient of linear expansion with an optical fiber greatly and to minimize variation in characteristics with temperature by using a glass fusing means such as a CO2 laser and a gas burner and soldering optical fibers to a glass-made reinforcing jig by fusion. CONSTITUTION:The optical fiber coupler is constituted by connecting a couple of single-mode optical fiber cores 1 to a glass substrate 4 by fusion, and the cores 1a, clads 1b, and fusion part 5 of the core conductors 1 are shown. When the optical fiber coupler is manufactured, the clads are removed, two front and rear parts are fused and connected by the CO2 laser across the optical coupling parts of the core conductors 1, and then lower ends of the core conductors 1 are fused and connected on the substrate 4 of low-fusion-point quartz glass of 5mmX30mmX0.5mm size similarly. Consequently, the optical fiber coupler is manufactured which has superior temperature transmission characteristics, mechanical characteristics, and reliability of optical transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an optical fiber coupler used in an optical communication system.

(Prior Art) In recent years, with advances in optical signal transmission technology, many types of optical communication systems have been proposed and put into practical use. With this background, one or more types of optical signals propagating on one transmission line can be branched into multiple transmission lines, or one or more types of optical signals propagated through multiple transmission lines can be split into one transmission line. It is requested that they be superimposed. Optical couplers perform this function, and among them, optical fiber couplers have lower loss than other components and are superior in connectivity with optical fibers, which are light transmission paths.

Figure 2 (A) shows the basic structure of an optical fiber coupler, in which a plurality of coated optical fibers 1 are fused and stretched, and an optical coupling part 2 with a reduced diameter is used to emit light. Signals are combined and demultiplexed. However, as can be seen from the drawings, the coupling part 2 of an optical fiber coupler is usually small in diameter, so stress tends to concentrate there, resulting in poor mechanical strength, and even small stress can cause changes in the multiplexing and demultiplexing characteristics. Increase in optical transmission loss is likely to occur.

For this reason, conventionally, as shown in FIGS. 2(B) and 2(C), an epoxy adhesive 3 is used to bond both sides of the optical coupling portion 2 of each optical fiber core 1 to a reinforcing glass substrate 4. are doing.

(Problem to be Solved by the Invention) However, when an optical fiber coupler is manufactured by the method described above, the linear expansion coefficient of the epoxy adhesive 3 which is a polymeric material is 2 compared to that of quartz glass which is an optical fiber material. Since it is more than an order of magnitude larger, there is a drawback that the characteristics of the optical fiber coupler are limited by the characteristics of the epoxy adhesive 3. For this reason,
Due to changes in temperature and humidity and external vibrations, optical fiber couplers tend to change the optical coupling ratio and increase optical transmission loss. The physical characteristics are also insufficient.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing an optical fiber coupler having excellent optical transmission temperature characteristics, mechanical characteristics, and reliability.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for manufacturing an optical fiber coupler in which a plurality of optical fibers having optical coupling portions are fixed to a reinforcing jig made of glass. The present invention is characterized in that the optical fiber and at least a portion of the reinforcing jig are fused using glass melting means.

(Function) With this configuration, each optical fiber is fused to the glass substrate or glass cylinder using glass melting means such as a laser or gas burner, and foreign materials such as epoxy adhesives are eliminated, improving various properties. do.

(Embodiment) FIG. 1A shows a first embodiment of a 3 dB' (optical branching ratio) optical fiber coupler to which the present invention is applied. This optical fiber coupler is constructed by fusing a pair of single-mode optical fiber cores (hereinafter referred to as core fibers) 1 to a glass substrate 4, and the core of each core fiber 1 is 1 g, and the cladding is 1 g.
b, each fused portion is indicated by 5;

In manufacturing the optical fiber coupler, first, the optical coupling part (see Fig. 2 (B)) of the core wire 1 from which the coating was removed is sandwiched, and the front and rear parts are fused using a CO2 laser, and then 5 am
The lower end of each core wire 1 was similarly fused onto a low melting point quartz glass substrate 4 measuring 30 x 0.5 mm.

This optical fiber coupler is exposed to UV (ultraviolet light) using the conventional method.
A heat cycle test was conducted on an equivalent 3 dB single mode optical fiber coupler similarly reinforced using a curable adhesive. The test temperature range is -60~150℃,
One cycle was 6 hours, the standing time at -60°C and 150°C was 1 hour each, and the temperature decreasing and temperature increasing rates were 110°C/hour (constant). FIG. 1(B) shows the temperature characteristics of the optical coupling ratio after 20 cycles. If reinforced using the conventional method, -6
While the optical coupling ratio fluctuates by a maximum of 3% in the temperature range of 0 to 160°C, when the reinforcement according to this example is applied, the optical coupling ratio changes in the same temperature range of -60 to 160°C. The variation in ratio was less than 0.2%.

FIG. 3 shows a plan view of the reinforcing portion of a 6×6 optical fiber coupler made up of six multimode optical fibers as a second embodiment of the present invention. A hard glass cylinder 4a with an inner diameter of 0.7+am and a length of 40+m is used. When manufacturing an optical fiber buster coupler, the coating of each optical fiber is removed, the core wires 1 are passed through a glass cylinder 4a, and both ends of the glass cylinder 4a are melted with a gas burner (propane gas) to form an optical coupling part. (See FIG. 2(B)) were tied together on both sides and fused and fixed.

This optical fiber coupler and conventional method
Vibration testing was performed on an equivalent 6x6 multimode fiber optic coupler similarly reinforced using a curable adhesive. Vibration frequency 2000Hz, amplitude ±1 fin,
Changes in the optical coupling ratio after 1 hour of vibration were measured perpendicular to the length in the vibration direction. As a result of testing 10 couplers each, it was found that the optical coupling ratio varied by up to 1% when reinforced using the conventional method, whereas when reinforced using this example, the optical coupling ratio changed. The variation was less than 0.1%.

FIG. 4 shows a third embodiment of the present invention, in which a wavelength of 0.8 μm is formed by two single mode optical fibers, 1.
A 3 μm combining/demultiplexing optical fiber coupler is shown.
A multi-component glass substrate 4b with a low melting point of 5+nX3cl+mXO, 5+u+ is used as the reinforcing jig.

In manufacturing, the two core wires 1 on both sides of the optical coupling part of the optical fiber coupler are fused and fixed at each point by arc discharge, and then the lower end of each core wire 1 is made into a multi-component glass by arc discharge. It was fused onto the substrate 4b.

This optical fiber coupler and an equivalent 0.8 μm, L
The tensile strength of the S μm combining/demultiplexing single mode optical fiber coupler was determined by a tensile test. As a result of testing 10 couplers each, the tensile strength when reinforced by the conventional method was all 100 g or less, whereas the tensile strength when reinforced according to the present example was all 500 g or more.

It should be noted that each of the above-mentioned embodiments is merely an illustration of the present invention.
This is not intended to limit the technical scope of the present invention in any way.

(Effects of the Invention) As detailed above, in the method for manufacturing an optical fiber coupler according to the present invention, a plurality of optical fibers are fused to a glass reinforcing jig using a glass melting means such as a C02 laser or a gas burner. This eliminates the need for conventional epoxy adhesives, significantly improves the matching of the coefficient of linear expansion with the optical fiber, and makes it possible to minimize changes in characteristics due to temperature changes.

In addition, since the connection strength of each component is improved, the stability of properties against external forces and mechanical properties are improved, and reliability is also improved against changes in temperature and humidity. Significant improvements in environmental resistance such as temperature expansion can be expected.

[Brief explanation of the drawing]

FIG. 1(A) is a sectional view showing a first embodiment of an optical fiber coupler fused by the manufacturing method of the present invention, FIG. 1(B)
is a diagram of the relationship between temperature and optical coupling ratio, Figure 2 (A), (B), (
C) shows the conventional product, Figure 2 (A) is a perspective view of the optical fiber coupler before reinforcement, Figure 2 CB) is a side view of the same after reinforcement, and Figure 2 (C) is the reinforced part. 3 and 4 are cross-sectional views of the second and third embodiments, respectively. DESCRIPTION OF SYMBOLS 1... Optical fiber core wire, 2... Optical coupling part, 4...
Glass substrate, 4a... Glass cylinder, 4b... Multi-component glass substrate, 5... Fusion part. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (4)

[Claims] (1) A method for manufacturing an optical fiber coupler in which a plurality of optical fibers having optical coupling portions are fixed to a reinforcing jig made of glass, wherein at least a part of the optical fibers and the reinforcing jig are melted using glass melting means. A method for manufacturing an optical fiber coupler, characterized by: fusing it. (2) The method for manufacturing an optical fiber coupler according to claim (1), wherein the reinforcing jig is a glass substrate, and the glass melting means is a CO_2 laser. (3) The reinforcing jig is a glass cylinder that covers the optical fiber,
Claim No. 1, wherein the glass melting means is a gas burner (
1) A method for manufacturing an optical fiber coupler according to item 1). (4) The method for manufacturing an optical fiber coupler according to claim (1), wherein the reinforcing jig is a multi-component glass substrate, and the glass melting means is arc discharge.