JPH06242342A - Optical fiber coupler - Google Patents

Abstract

PURPOSE:To provide are optical fiber coupler having good strength and workability and having stable optical characteristics by housing a coupler body into a reinforcing device consisting of a metallic material specified in coefft. of thermal expansion. CONSTITUTION:This optical fiber coupler 1 consists of the coupler body 2 and the reinforcing device 3 housing the coupler body 2. The coupler body 2 and the reinforcing device 3 are adhered to each other by an adhesive 7. The metallic material having <=1X10<-6>/ deg.C coefft. of thermal expansion is used as the material for forming the reinforcing device 3. The more specific metallic material is exemplified by a nondeforming steel, super nondeforming steel or stainless nondeforming steel. The coupler body 2 is housed into the reinforcing device 3 consisting of the metallic material having <=1X10<-6>/ deg.C coefft. of thermal expansion and, therefore, a difference in the coefft. of thermal expansion between the reinforcing device 3 and optical fiber glass is suppressed to a lower level and the optical stability against a temp. change of use environment is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion splicing type optical fiber coupler, and more particularly to an optical fiber coupler having stable optical characteristics.

[0002]

2. Description of the Related Art Conventionally, a fusion-spreading type optical fiber coupler is one in which a plurality of optical fibers are spliced, fused and stretched to form a fused portion, which is incident on any one of the optical fibers. It splits light or joins light entering multiple optical fiber terminals and extracts it from other fiber terminals. It also combines or splits light of different wavelengths. It is an optical component used for optical communication, and is used for optical communication using an optical fiber as a transmission medium and optical measurement.

As is well known, most optical fibers for optical communication currently used are made of glass, and most of them are mainly made of quartz glass.

By the way, the glass diameter (clad diameter) of a standard optical fiber is 125 μm, which is quite small, but it is still necessary to apply a tension of about 1 kg to give 1% elongation strain. As described above, when the optical fiber is fusion-stretched, the fusion-stretched portion has a thinner outer diameter of several tens of μm, and its cross-sectional area is one-tenth or less of that of a standard fiber. For this reason, this coupler body may be very distorted even by applying a slight force.

Therefore, in practice, the optical fiber coupler is usually used by accommodating the fusion splicing portion in a suitable reinforcing device. If the material of the reinforcing device is the same as that of the coupler body, that is, the optical fiber glass, a very stable coupler can be manufactured from the viewpoint of thermal expansion. The material of the conventionally commonly used reinforcing device is quartz glass or quartz glass. Besides, a metal material may be used.

[0006]

However, when the reinforcing device made of the glass-based material is used, the breaking strength is insufficient because the glass is a brittle material, and it cannot be processed into a free shape. There was such a problem.

On the other hand, when a stiffener made of a metal-based material is used, the thermal properties of the coupler are greatly different from those of the optical fiber glass, so that the optical stability of the coupler with respect to the temperature change of the use environment is poor. There was a problem.

The present invention has been made in view of these circumstances, and an object thereof is to provide an optical fiber coupler having good strength and workability and having stable optical characteristics.

[0009]

To achieve this object, the optical fiber coupler of the present invention has a coefficient of thermal expansion of 1 ×.
It is characterized in that the coupler body is housed in a reinforcing device made of a metal material of 10 ⁻⁶ / ° C. or less. In particular, the optical fiber coupler according to claim 2 is characterized in that the metal material is any one of invariant steel, ultra-invariant steel, and rust-invariant steel.

[0010]

In the optical fiber coupler of the present invention, since the reinforcing device made of a metal material having a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less is used, the thermal expansion coefficient of the reinforcing device and the optical fiber glass is By suppressing the difference to 1 × 10 ⁻⁶ / ° C. or less, the thermal characteristics of both can be made relatively close. Therefore, it is possible to provide an optical fiber coupler having good optical stability with respect to temperature changes in the use environment.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 and 2 are a plan sectional view and a transverse sectional view showing an embodiment of an optical fiber coupler. The optical fiber coupler 1 of the present embodiment is roughly composed of a coupler body 2 and a reinforcing device 3 that accommodates the coupler body 2.

The coupler body 2 is manufactured by arranging a plurality of optical fibers 4 and 4 in contact with each other in parallel, heating them with a heating device (not shown) and locally fusing them.
Optically continuous fused stretched portion A and non-fused stretched portion B
And have.

The optical fiber 4 has a high-refractive-index core portion made of quartz to which a dopant such as germanium oxide is added, and a low-refractive-index cladding portion made of quartz around the core portion. Fibers or multimode fibers are used. The optical fiber 4 of the non-fusing extension part B
A coating layer 5 made of an ultraviolet curable resin or the like is provided on the outer periphery of the.

As shown in FIG. 2, the reinforcing device 3 has a lower part 3a having a substantially semicircular cross section, which is provided with a recess 6 which is opened in the upper surface and accommodates the coupler body 2, and the upper part of the lower part 3a. It is composed of an upper part 3b having a substantially semicircular cross section that is joined to close the recess 6, and these upper and lower parts 3a and 3b are joined to form a substantially cylindrical reinforcing device 3. The upper and lower parts 3a and 3b are formed in respective shapes so that the center line of the coupler body 2 coincides with the center line of the stiffener 3 when the coupler body 2 is housed in the recess 6. . This is because the strain generated in the coupler body 2 when an external force is applied to the reinforcing device 3 can be suppressed to a minimum. The upper and lower parts 3a and 3b are joined by an adhesive, laser welding, or the like.

The shape of the recess 6 may be a semi-circular cross section as shown in FIG. 3 in addition to the rectangular cross section as shown in FIG. In addition to the circular cross section shown in FIG. 2, the outer shape of the reinforcing device 3 may be a quadrangular cross section as shown in FIG. 4 or 5.

The recess 6 is, as shown in FIG.
The coupler main body 2 is formed to have a large size in a central portion that accommodates the fusion-bonded stretched portion A and a small size in both end portions that accommodates the non-fusion-bonded stretched portion B.

The coupler body 2 and the reinforcing device 3 are formed in the recess 6
By filling the gaps inside with the adhesive 7, they are adhered to each other.

As a material for forming the reinforcing device 3, a metal material having a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less is used. If the coefficient of thermal expansion exceeds this value, the difference in coefficient of thermal expansion from the optical fiber glass forming the coupler body 2 becomes large, and the stability of the coupler body 2 with respect to changes in environmental temperature deteriorates. .

Examples of specific metal materials include invariant steel, ultrainvariant steel, and rust-invariant steel. Immutable steel is iron 6
It has a composition of 3.5% and nickel 36.5%, ultra-invariant steel has a composition of iron 63%, nickel 32% and cobalt 5%, and stainless steel has a composition of iron 36.5%. 54% cobalt,
It has a composition of 9.5% chromium.

As described above, in the optical fiber coupler of this embodiment, since the coupler main body 2 is housed in the reinforcing device 3 made of a metal material having a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less,
The difference in the coefficient of thermal expansion between the reinforcing device 3 and the optical fiber glass can be suppressed to be small, and the optical stability with respect to the temperature change of the use environment can be improved.

Further, it is possible to improve the breaking strength and the moldability as compared with the case where the reinforcing device made of a glass material is used.

Specific examples will be shown below to clarify the effects of the present invention. (Example) A reinforcing device having a cross-sectional structure shown in FIG. 2 was made of ultra-invariant steel. The outer diameter of the reinforcing device was 4 mmφ. The shape of the recess for accommodating the coupler body is a quadrangular cross section, and the size thereof is 1500 μm × 1500 μm at the central portion for accommodating the fusion-bonded stretched portion of the coupler body, and 700 μm × at both end portions for accommodating the non-fusion-stretched portion. It was set to 700 μm.
On the other hand, core diameter 9 μm, outer diameter 125 μm, coating (ultraviolet curable resin) diameter 250 μm, cutoff wavelength 1.2 μm,
A single-mode fiber having a mode field of 9.5 μm was used, and a plurality of the single-mode fibers were arranged in parallel in a contact state and fused and drawn to produce a coupler body having a wavelength of 1.3 μm and a branching ratio of 1: 1.
An optical fiber coupler was manufactured by accommodating the coupler main body in the recess of the reinforcing device, filling a gap between the coupler main body and the recess with an adhesive, and bonding the two together.

(Comparative Example) An optical fiber coupler was manufactured in the same manner as in the above Example except that a reinforcing device made of quartz glass was used.

When the loss characteristics in the temperature range of −45 ° C. to + 80 ° C. were examined using the optical fiber couplers of Examples and Comparative Examples, almost no change in the characteristics was observed in Examples. On the other hand, in the comparative example, the contraction stress of the adhesive at a low temperature causes a breakage in a part of the coupler body, and the branching ratio is originally 1: 1;
→ The transmission loss around 4 dB of 4 greatly changed. Further, a variation of about ± 1 dB was observed among some test samples.

[0025]

As described above, in the optical fiber coupler of the present invention, since the coupler body is housed in the reinforcing device made of a metal material having a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less, It is possible to provide an optical fiber coupler which has a small difference in thermal expansion coefficient between the stiffener and the optical fiber glass and which has good optical stability with respect to temperature changes in the use environment. Further, it is possible to improve the breaking strength and the molding workability as compared with the case where a glass-based material reinforcing device is used.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing an embodiment of an optical fiber coupler of the present invention.

FIG. 2 is a cross sectional view showing the optical fiber coupler.

FIG. 3 is a cross-sectional view showing another example of the shape of the reinforcing device in the optical fiber coupler.

FIG. 4 is a cross-sectional view showing another example of the shape of the reinforcing device.

FIG. 5 is a cross-sectional view showing another example of the shape of the reinforcing device.

[Explanation of symbols]

 1 Optical fiber coupler 2 Coupler body 3 Reinforcer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Kawakami 42-1, Shintomi, Futtsu City, Chiba Prefecture Fujikura Futtsu Plant (72) Inventor Shinichiro Shishikura 42-1, Shintomi, Futtsu City, Chiba Prefecture Fujikura Futtsu Plant Co., Ltd. Within

Claims (2)

[Claims] 1. An optical fiber coupler in which a coupler body is housed in a reinforcing device made of a metal material having a coefficient of thermal expansion of 1 × 10 ⁻⁶ / ° C. or less. 2. The optical fiber coupler according to claim 1, wherein the metal material is any one of invariant steel, ultra-invariant steel, and rust-invariant steel.