JPS628109A - Slab type converging optical transmission body - Google Patents

Abstract

PURPOSE:To reduce the insertion loss of a lens and facilitate the fixation of a slab lens, and to improve operability by forming a reflecting film on the flank of the slab lens. CONSTITUTION:One light measuring fiber 1 is connected to the center of an incidence surface and the reflecting film 4 is formed on the flank perpendicular to the plane of the optical axis except the incidence end surface and projection end surface of the slab lens 2 which has plural light measuring fibers 3 arrayed on the projection surface. This reflecting film should have high functional strength and superior chemical and thermal durability in addition to high reflection efficiency. A metallic vapor-deposited film of Al, etc., attains the purpose sufficiently, but the use of a total reflecting film obtained by vapor-depositing a transparent material with a low refractive index such as MgF2 eliminates extension to the incidence or projection end surface and spoils neither incident light nor projection light, which is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a slab-like convergent transmission body used in branch circuits, multi-terminal LD modules, etc. in the field of optical communications.

[Prior Art] In an optical fiber communication system, a circuit that evenly branches light output from a light source such as an LD (laser diode) or one input photometric fiber to a plurality of output photometric fibers is useful.

The present inventors previously developed a molecular stuffing method (Japanese Unexamined Patent Publication No.
-146946) and ion diffusion method (patent application No. 146946)
6913), one direction perpendicular to the optical axis plane (y direction)
A slab-like focusing optical transmission body (hereinafter referred to as a slab lens) has a refractive index distribution approximately expressed by formula 1 from the optical axis plane toward the periphery, and has a uniform refractive index in the direction parallel to the optical axis plane (hereinafter referred to as a slab lens). ) has been disclosed.

n(V)2=n2 (1-Q”T/2)
+11 Here, no is the refractive index on the optical axis, n (y) is the refractive index at a point at a distance y from the optical axis, and qo is a constant. Furthermore, using these slab lenses, a patent application was filed in 1986-1965.
In No. 28, the optical branch circuit was proposed in patent application No. 60-97959.
disclosed a multi-terminal LD modulator in the issue. - As an example, the configuration of an optical branching circuit is shown in FIG. 2, and the length is approximately 0.5 pitch (one pitch length is 2π/g).

A single fiber 1 is connected to the center of the entrance surface of the slab lens 20, and a plurality of optical fibers 3 are connected to the exit surface of the slab lens 2 in a line along the optical axis plane of the slab lens 2. They are arranged with approximately equal width. As shown in FIG. 3, the light incident on this slab lens 2 is
In the y-axis direction, the light is refracted within the lens and condensed on the output end face, and in the Z-axis direction, as shown in FIG. 4, the light travels straight through the lens and is repeatedly reflected on the side surfaces to be mixed. In this way, the light is condensed into a uniform line on the optical axis at the output end face.

[Problems to be Solved by the Invention] However, in such a branch circuit, when fixing the slab lens, if adhesive is applied or a presser is applied to the side surface of the slab lens, the inside of the lens will be exposed to the side surface. There was a problem in that some of the incident light leaked outside without being reflected, increasing insertion loss of the lens.

In order to solve such problems, the present invention aims to provide a slab-like convergent optical transmission body that does not leak light from the side to the outside.

[Means for solving the problems] In order to achieve the above object, the present invention provides an optical axis perpendicular to the optical axis plane.
The refractive index gradually decreases from the optical axis plane toward the periphery only in the direction, and the refractive index is uniform in the direction parallel to the optical axis plane.The side surface of a slab lens (excluding the input end and output end surface)
Moreover, the lens is characterized in that the side surface perpendicular to the optical axis plane is equipped with a reflective film that has a function of reflecting light incident on the side surface from inside the lens into the lens. In this way, in the present invention, since the reflective film is formed on the side surface of the slab lens, the insertion loss of the lens can be kept low.

[Example 1 Hereinafter, the present invention will be explained based on the drawings.

As shown in FIG. 1, one photometric fiber 1 is connected to the center of the input surface, and a plurality of photometric fibers 3 are arranged in a line on the output surface of the slab lens 2. Moreover, there is a reflective film 4 on the side surface perpendicular to the optical axis plane.
to form. In addition to high reflection efficiency, this material 114 is required to have strong functional strength and excellent chemical and thermal durability.

Although the purpose of the present invention can be sufficiently achieved with a metal vapor-deposited film such as A42, if a total reflection film obtained by vapor-depositing a transparent material with a low refractive index such as MQF2 is used, it is possible to form a reflective film on the incident end face or the outgoing end face. This is convenient because there is no interference and the incident light and the emitted light are not damaged.

Next, we will explain the manufacturing method and effects of the product of the present invention, similar to the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 146946/1983.
A porous glass plate obtained by acid-treating phase-separated glass (thickness 4cm, width 6G+ss).

120g of C8NO per 10011 of water
C8NO3 was stuffed into the pores of the porous body by immersing it in a solution in which C.
Unstuffed ink was performed by immersion at ℃ for 20 minutes.

After that, this glass body was immersed in a methanol solution at a temperature of 0"C for 3 hours to perform precipitation, and then dried and fired at 880℃ to make it non-porous, making it a raw material for transparent slab lenses. Obtained.

This raw material is cut out and polished to a thickness of 3.411 mm, a width of 0.6 mm, and a length of 0.5 pitch (36,805 mm).
A slab lens of m) was produced. One GI5G (core diameter 50μ11 cladding diameter 125μm) optical fiber is placed in the center of the entrance surface of this slab lens, and ten GI5G (core diameter 50μ11 cladding diameter 125μm) optical fibers are placed on the optical axis of the output surface with a cladding diameter 60μm and core diameter 50μm.
10 pieces of 01 with 0 cladding diameter 60 span 0μ■diameter 50μ-
An optical fiber array consisting of 50 optical fibers arranged in a row is tightly attached and the whole is glued with epoxy adhesive (refractive index 1.55).
A 1:10 branch circuit was created by fixing the circuit with

In this 1:10 branch circuit, when a slab lens without a reflective film on the side surface is used, the side surface is reflected before applying the adhesive (Comparative Example 1) and after applying the adhesive (Comparative Example 2). The properties obtained in each case (Examples 1 to 5) using a slab lens coated with an OA film and fixed with a bonding agent are summarized in the table below along with an introduction to the film. Comparative Example 1 had an excellent insertion loss of 15 dB and output variation of 0.2 dB, but Comparative Example 2, which fixed the circular side surface with adhesive, had a poor insertion loss e and SDI output variation of 1.5 dB, resulting in poor branch circuit performance. cannot be used as However, in Examples 1 to 4 in which a reflective film was attached to the side surface of the slab lens based on the present invention, even if it was fixed with adhesive, the insertion loss and output varied. Even if a compound is applied, the light that enters the side surface from inside the slab lens is reflected at the interface between the side surface and the film, and there is no leakage to the outside, so the insertion loss of the lens can be reduced and the slab lens can be easily fixed. , and work efficiency has improved.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the slab-like focusing optical transmission body of the present invention, Figure 2
3 is a side view illustrating the progression of light within the slab lens, and FIG. 4 is a front view illustrating the progression of light within the slab lens. DESCRIPTION OF SYMBOLS 1...Incidence side optical fiber, 2...Slab-like focusing transmission body (slab lens), 3...Output side optical fiber array, 4...Reflection film. Applicant Hoya Co., Ltd.

Claims (1)

[Claims] 1. The refractive index gradually decreases from the optical axis toward the periphery only in one direction perpendicular to the optical axis, and has a uniform refractive index in the direction parallel to the optical axis. A slab characterized in that a reflective film having a function of reflecting light incident from inside into the slab lens body is provided on a side surface of the slab lens body other than the incident end face and the output end face, and moreover, on the side face perpendicular to the optical axis plane. A convergent light transmitter. 2. The slab-shaped convergent optical transmission body according to claim 1, wherein the reflective film on the side surface is a transparent vapor-deposited film having a function of reflecting light.