JPH06242353A - Optical fiber array and its production - Google Patents

Abstract

PURPOSE:To provide an optical fiber array appropriate for coupling with an LD array at high coupling efficiency and its manufacturing method. CONSTITUTION:The optical fiber array consists of a base 3 and plural quartz group optical fibers 1 fixed on the base 3 and projecting their end parts 1'c from the end face 3a of the base 3, the projected length of the end parts 1'c is the same in all the fibers 1 and a truncated cone-like lens part 6 is formed on the tip of each end part 1'c. The optical fiber array is manufactured by applying etching treatment to an array precursor obtained by previously aligning the fibers 1 and the end face 3a of the base 3 with two kinds of etching solutions having respectively different properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber array and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a light emitting device module incorporated in an optical communication system has been a semiconductor laser (laser-diod) as a light source.
e, hereinafter referred to as LD) and a silica-based optical fiber, and a lens for collecting the laser light at the core of the silica-based optical fiber is inserted. This module is L
Since it is necessary to increase the coupling efficiency between D and the silica optical fiber, the LD, the lens, and the silica optical fiber core are aligned and assembled so that the coupling power between them is maximized.

By the way, recently, a plurality of LD light sources are arranged to form an LD array, and a plurality of silica-based optical fibers are arranged on a substrate to form an optical fiber array.
A demand for an LD array module having a structure in which each light source and each silica-based optical fiber are collectively connected by connecting the array and the optical fiber array to each other through a lens array in which a plurality of lenses are arranged. Is increasing.

In this LD array module, it goes without saying that it is desirable that the respective arrays be coupled with high coupling efficiency, but the output power from each silica-based optical fiber arranged in the optical fiber array is It is required to be uniform. Therefore, when manufacturing this LD array module, it is necessary to improve the dimensional accuracy of each array and to align the LD light source, the lens, the silica optical fiber, and the like.

On the other hand, recently, there has been proposed a silica optical fiber with a lens in which a lens portion is directly formed on the end face of the silica optical fiber. Since this silica-based optical fiber has a lens function on its end face, the number of parts can be reduced and the number of man-hours for aligning can be reduced when manufacturing the module, which contributes to cost reduction. Has the advantage.

The above-mentioned quartz optical fiber with a lens is
The quartz optical fiber exposed by peeling off the coating portion is stretched while locally heating it by a heating means such as a burner to stretch the heating portion, and the outer diameter of the stretched portion of the silica optical fiber is about 1
When the thickness becomes 0 μm or less, the stretching operation is stopped, the portion is cut by, for example, a cutter, and then the tip end of the silica-based optical fiber is heated by, for example, a burner to melt. At this time,
The tip portion becomes spherical due to the surface tension, and as a result, the lens function is developed in this portion.

Therefore, the silica-based optical fiber with a lens has a spherical lens at its tip and forms a taper portion having a length gradually increasing from the tip. Using such a quartz optical fiber with a lens, L
When manufacturing a D array module, as a first step, it is necessary to array and fix a plurality of silica optical fibers with lenses on a substrate to manufacture an optical fiber array.

In this case, if the positions of the tips of the respective silica-based optical fibers are not aligned, the coupling efficiency between the respective silica-based optical fibers and the respective LD light sources will vary when the LD array is coupled. . In the case of a silica-based optical fiber with a lens, unlike the conventional silica-based optical fiber in which the end face is a plane orthogonal to the optical axis, the work of aligning the tip of the lens part at the same position becomes possible, which increases complexity. There is.

For the purpose of solving such a problem, Japanese Patent Publication No. 3-50246 proposes the following method. That is, first, when a plurality of silica optical fibers with lenses are aligned and fixed to the array substrate, the tip end of the optical fibers is made to protrude from the end surface of the array substrate by a predetermined length. Then, only the tip of the optical fiber is immersed in hydrofluoric acid to dissolve it, and the tip of each optical fiber is made into a tapered shape. The protruding lengths of are the same.

[0010]

By the way, the optical fiber has a bend in itself, though it is a small amount. In consideration of this, it can be said that the shorter the length of projecting the tip of the optical fiber from the end face of the array substrate is, the more preferable when the array of the optical fibers is fixed to the array substrate in the above method. The reason for this is that the alignment accuracy of the optical fiber tip portion becomes high.

However, if the length by which the tip portion is projected is made too short, when the tip portion is immersed in hydrofluoric acid, the array substrate may be eroded by the hydrofluoric acid that has risen along the tip portion due to surface tension. is there. Therefore, according to the method of the above publication, the length of the tip cannot be shortened so much. The present invention solves the problems in the above method, and the length of the silica optical fiber with a lens protruding from the end face of the array substrate is very short, and accordingly, the optical fiber array having a high optical fiber array accuracy is provided. The purpose is to provide a manufacturing method thereof.

[0012]

In order to achieve the above object, in the present invention, a substrate and a plurality of silica-based optical fibers fixed to the substrate and having an end projecting from an end face of the substrate. And a protrusion length of the end portion is the same for all silica-based optical fibers, and at least a frustoconical lens portion is formed at the tip of the end portion. A fiber array is provided, and a plurality of silica-based optical fibers composed of a core and a clad having a composition having a higher etching rate when using a hydrofluoric acid solution are aligned and fixed on a substrate that is not corroded by the hydrofluoric acid solution. After that, the end face of the substrate and the end faces of the plurality of silica-based optical fibers are processed to be the same face, and the portion of the same face is at least the silica-based etching rate for the substrate. The substrate is selectively removed by etching by immersing it in an etching solution having a larger etching rate than that of the fiber, and the end of the silica-based optical fiber is projected, and then the end of the silica-based optical fiber is hydrofluoric acid solution. There is provided a method for manufacturing an optical fiber array, which comprises immersing in a core to form a lens portion by projecting at least a truncated cone-shaped core at the tip of the end portion.

[0013]

In the present invention, first, the end face of the substrate and the end face of the silica-based optical fiber are processed so that they are flush with each other.
Then, it is immersed in the first etching solution. At that time, since the etching solution selectively dissolves the substrate, the end portion of the silica-based optical fiber projects from the end surface of the substrate with the same length after the end of etching. To do.

After that, the end of the optical fiber is
The substrate is not eroded and the silica-based optical fiber is selectively dissolved at that time, but in that case, the clad dissolves faster, At the tips of the plurality of silica-based optical fibers protruding from the end surface of the substrate, cores having the same shape and protruding in a truncated cone shape come out. And this becomes the lens part.

Therefore, the optical fibers having the same protrusion length and the lens portion at the tip are arranged on the end face of the substrate, and the optical fiber array can be obtained here.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, first, as shown in FIG. 1, each silica-based optical fiber 1 of a multi-core optical fiber 2 having a plurality (4 in the drawing) of silica-based optical fibers 1 is For example, by arranging them on a fiber alignment plate 3a in which V-shaped grooves having a predetermined size are engraved, covering the holding plate 3b shown by imaginary lines from above, and then bonding the two with, for example, an epoxy adhesive. Thus, each quartz optical fiber 1 is fixed. At this time, the tip 1a of the silica-based optical fiber 1 is attached to the substrate 3
The protrusions a and 3b are projected from the end faces, but the length of the protrusion may be uneven in each silica optical fiber.

Then, as shown in FIG. 2, the end face 3c of the substrate 3 composed of the fiber aligning plate 3a and the pressing plate 3b is polished so as to project unevenly from the end face of the substrate as shown in FIG. The end 1a that had been used is also polished so that the end face 3c of the substrate 3 and the end face 1b of the silica-based optical fiber 1 are aligned in the same plane. As the above-mentioned silica-based optical fiber, an optical fiber is used in which the etching rate of the cladding is higher than the etching rate of the core when it is immersed in a hydrofluoric acid solution.

The following can be given as such an optical fiber. First, in the first optical fiber, the core is made of pure silica glass (SiO ₂ ), and the clad surrounding the core is made of glass having a composition obtained by doping silica glass with a fluorine component. As another optical fiber, the core is made of silica glass and Ge.
It is composed of a material doped with O ₂ . In this case, the clad may be pure quartz glass, or may be doped with a fluorine component or the like.

In the former optical fiber, the doping amount of the fluorine component in the clad was formed because the etching rate between the clad and the core was appropriately different when the end face of the optical fiber was immersed in hydrofluoric acid. The truncated cone shape of the core is adjusted so as to exert an appropriate lens function, but at the same time, it is adjusted so as not to adversely affect the optical transmission characteristics of the optical fiber. Usually, the difference in refractive index between the core and the clad is 0.3-
It is preferably about 0.4%.

The clad may be formed by mixing a phosphorus component in place of the fluorine component, or by mixing a phosphorus component in addition to the fluorine component. Furthermore, when the core is not pure quartz glass but has a composition in which a fluorine component or a germanium component such as GeO ₂ is mixed, the cladding should be within the range that does not affect the optical transmission characteristics. A large amount of the above-mentioned fluorine component may be mixed to make the etching rate for hydrofluoric acid different between the core and the clad.

The same applies to the latter optical fiber, and the amount of germanium component doped into the core has an appropriate difference in the etching rate between the core and the clad when the end face of this optical fiber is immersed in a hydrofluoric acid solution described later. Occurs, and the truncated cone shape of the formed core is adjusted so as to exert an appropriate lens function. In addition, as a material for forming the substrate 3, for example, metallic silicon can be cited as a preferable material in relation to the two times of the etching treatment described later.

Then, the quartz optical fiber 1 and the substrate 3 are polished so that their respective end faces are flush with each other, and the same plane portion is immersed in the first etching solution 4 as shown in FIG. To do. As the etching solution 4, one having an etching rate with respect to the substrate 3 higher than that with respect to the silica optical fiber is used. For example, when the substrate 3 is made of metallic silicon, a mixed solution of nitric acid and hydrofluoric acid can be used.

For example, when a mixed solution of nitric acid and hydrofluoric acid is used, the substrate 3 may vary depending on their concentrations and mixing ratios.
When is silicon metal, the etching of the metal silicon proceeds about 10 times faster than the etching of the silica optical fiber. As a result, as shown in FIG. 4, the end portion of the substrate 3 is selectively removed by etching, and the end portion 1c of the silica-based optical fiber 1 projects from the end surface 3d after etching. At this time, since the etching conditions that act on the respective silica-based optical fibers 1 are the same, the protruding length of the end portion 1c of each silica-based optical fiber from the substrate end face 3d is the same for all silica-based optical fibers 1. become.

The protruding length of the end portion 1c is mainly defined by the etching processing time. Therefore, the protrusion length of the end 1c can be shortened, lengthened, or arbitrarily changed by changing the etching processing time. Then, as shown in FIG. 5, the end portion 1c of the silica-based optical fiber and the portion of the substrate 3 shown in FIG. 4 are immersed in a hydrofluoric acid solution 5 which is a second etching solution.

The former optical fiber is immersed in hydrofluoric acid. As the hydrofluoric acid solution, one obtained by diluting hydrofluoric acid with water or ammonium fluoride is usually used. The hydrofluoric acid concentration at that time is determined by the relationship with the etching rate of the cladding and core of the silica-based optical fiber.
It may be about 0 to 50 mol%.

When the end face of the optical fiber is dipped in a hydrofluoric acid solution, both the clad and the core are made of silica glass and thus etched. At this time, the etching rate of the clad is higher than the etching rate of the core, and the etching progresses in the axial direction of the optical fiber to shorten the optical fiber and proceeds in the radial direction of the optical fiber to thin the optical fiber. Since the etching and the etching progress in a combined state, after a predetermined time elapses, the core has a truncated cone shape and protrudes from the end face of the optical fiber.

At this time, when the substrate 3 is made of metallic silicon, the etching of the substrate 3 does not proceed, and the end 1 of the silica-based optical fiber protruding from the end face 3d of the substrate.
c is selectively etched. In this case, the etching rate of the clad at the end 1c is higher than the etching rate of the core, and the etching proceeds in the axial direction of the silica-based optical fiber to shorten the optical fiber and in the radial direction of the silica-based optical fiber. And the etching for thinning the optical fiber is performed.
After all, after a predetermined time has passed, as shown in FIGS. 6 and 7, before the etching process, the substrate 3 is
The end portion 1c of the silica-based optical fiber 1 protruding from the end surface 3d has a small diameter and a short length as a whole, but at the same time, the end portion 1c 'after etching has a truncated cone-shaped core at its tip. And then project. And this protruding portion 6
Functions as a lens.

In this etching process, the etching conditions that act on the end 1c of each silica-based optical fiber are the same,
Moreover, since the etching of the substrate end face 3a does not proceed, the protruding length of the end 1c 'protruding from the substrate end face 3d is the same for all the silica optical fibers 1. In addition, in the truncated cone-shaped portion of the protruding portion (lens portion) 6,
For example, when a focused laser beam is irradiated and heated and melted, this truncated cone shape can be changed to a spherical lens.

Further, at this time, by selecting an appropriate etching condition such as lengthening the etching processing time, for example, as shown in FIG. 8, the core is made to protrude in a conical shape at the tip of the end 1c '. You can also Then, by heating and melting the conical protruding portion 6'to make the leading end spherical so as to form a lens portion, the light collecting efficiency is increased, and a suitable optical fiber array can be obtained.

[0030]

As is apparent from the above description, according to the present invention, the optical fibers projecting from the end face of the substrate have the same projecting length, and the optical fiber is integrally provided with the lens portion at the tip thereof. An array can be obtained. Therefore, if this optical fiber array and LD array are combined,
It is possible to obtain an LD array module having a high coupling efficiency, and the coupling efficiency does not vary between each LD and each silica-based optical fiber.

In this optical fiber array, the end faces of the silica-based optical fiber and the substrate are aligned by polishing, and then 2
Since it can be obtained only by performing an etching process using a kind of etching solution, its productivity is high. Moreover, by selecting the etching treatment time, it is possible to adjust the length of the protruding length of the end portion of the silica-based optical fiber regardless of the surface tension of the etching solution.
It is particularly suitable for manufacturing an optical fiber array having a short protruding length.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which multi-core fibers are arranged on a fiber organizing plate.

FIG. 2 is a perspective view showing a state where the end face of the substrate and the end face of the silica-based optical fiber are processed to be the same face.

FIG. 3 is a schematic view showing a state in which the same surface portion of FIG. 2 is immersed in a first etching solution.

FIG. 4 is a schematic view showing a state of an end surface of the substrate after the etching process of FIG.

5 is a schematic view showing a state where the end face portion of the substrate of FIG. 4 is immersed in a hydrofluoric acid solution.

FIG. 6 is a partial schematic view showing a state of a substrate end surface portion after the etching treatment of FIG. 5;

7 is a partial perspective view showing a state of a substrate end surface portion after the etching process of FIG.

8 is a partial schematic view showing another state of the end face portion of the substrate after the etching treatment of FIG.

[Explanation of symbols]

1 Silica-based optical fiber 1a End face of arrayed silica-based optical fiber 1b End face of silica-based optical fiber 1 after polishing 1c Tip of silica-based optical fiber 1 protruding in the first etching treatment 1'c Second etching treatment The tip of the silica-based optical fiber 1 formed in 2. Multi-fiber 3 Substrate 3a Fiber alignment plate 3b Holding plate 3c Polished surface of the substrate 3 and the silica-based optical fiber 3d End face of the substrate 3 after the first etching 4 1 Etching solution 5 Hydrofluoric acid solution 6 Cone trapezoidal core protrusion (lens) 6'Cone cone protrusion

Claims (4)

[Claims] 1. A substrate and a plurality of silica-based optical fibers fixed to the substrate and having an end protruding from the end face of the substrate, wherein the protruding length of the end is the same for all silica-based optical fibers. An optical fiber array having the same length, and at least a frustoconical lens portion is formed at the tip of the end portion. 2. A plurality of silica-based optical fibers consisting of a core and a clad having a composition having a higher etching rate when a hydrofluoric acid solution is used than the core are aligned and fixed on a substrate which is not corroded by the hydrofluoric acid solution, The end face of the substrate and the end faces of the plurality of silica-based optical fibers are processed to be the same face, and at least the etching rate for the substrate is higher than the etching rate for the silica-based optical fiber in the same face portion. The substrate is selectively removed by etching by immersing it in an etching solution so that the end of the silica-based optical fiber is projected, and then the end of the silica-based optical fiber is immersed in a hydrofluoric acid solution to form the end. A method of manufacturing an optical fiber array, wherein a lens portion is formed by projecting at least a truncated cone-shaped core at the tip of the. 3. The method of manufacturing an optical fiber array according to claim 2, wherein the core is formed by doping germanium component into pure silica glass, and the hydrofluoric acid solution is a mixed aqueous solution of hydrofluoric acid and ammonium fluoride. 4. The method of manufacturing an optical fiber array according to claim 2, wherein the truncated cone-shaped core is heated and melted to form a curved lens portion.