JP3234347B2 - Optical fiber array and manufacturing method thereof - Google Patents

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 to be coupled to an LD array and a method of manufacturing the same. More specifically, the distance between the end face of the fiber alignment block and the tip working face of the silica-based optical fiber is all quartz. It is the same as the system optical fiber, and furthermore, a lens portion is integrally formed on the tip working surface, and it is possible to prevent gas generation from the fiber alignment block at the time of operation, thereby preventing contamination of the LD array. The present invention relates to a possible optical fiber array and a method for manufacturing the same.

[0002]

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

On the other hand, recently, a quartz optical fiber with a lens in which a lens portion is formed directly on the end face of the quartz optical fiber has been proposed. Since the end face of the silica-based optical fiber itself has a lens function, the number of components is reduced and the number of steps of the alignment work can be reduced when manufacturing the module, which contributes to cost reduction. It has the advantage.

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

By the way, a light emitting element module in which this quartz optical fiber with a lens is assembled is conventionally known, for example, as shown in FIG.
The structure is as shown in FIG. That is, the package 7 in which the upper part is opened and the bare LD 6 is disposed inside.
A quartz optical fiber with lens 8 is inserted from the wall of
The tip lens portion 8a and the light emitting surface of the LD 6 are set so as to face each other at an interval of about 10 μm. And
A cover 9 is provided at the opening of the package 7 for the purpose of preventing the oxidation of the LD 6 and preventing moisture.
0, so that the package 7 has an airtight structure.

[0006]

By the way, recently, LD
A plurality of light sources are arranged to form an LD array, and a plurality of quartz-based optical fibers are arranged in a fiber alignment block to form an optical fiber array. The LD array and this optical fiber array are formed by a plurality of lenses. There is an increasing demand for an LD array module having a structure in which each light source and each silica-based optical fiber are collectively coupled by being coupled to each other via the arranged lens array.

In this LD array module, it is needless to say that the respective arrays are desirably coupled with high coupling efficiency. However, the output power from each quartz optical fiber arranged in the optical fiber array is It is required to be uniform. When such an LD array module is manufactured using the above-mentioned quartz optical fiber with a lens, as a pre-operation, a plurality of the quartz optical fibers with a lens are arranged and fixed in a fiber alignment block, and an optical fiber An array must be assembled.

In this case, if the positions of the tips of the silica-based optical fibers with lenses are not aligned for all the optical fibers with respect to each of the light sources of the LD array, the respective optical fibers and the respective optical fibers are connected at the time of coupling with the LD array. Variations occur in the coupling efficiency with the LD light source. In the case of a silica-based optical fiber with a lens, unlike the conventional optical fiber in which the end face is orthogonal to the optical axis, the work of aligning the tips of the lens portions of all the optical fibers to the same position is quite complicated. Become.

The present invention solves the above-mentioned problem when an optical fiber array is manufactured by arranging silica-based optical fibers with lenses in a fiber alignment block, and simply positions the tips of the lens portions of all the optical fibers at the same position. An optical fiber array capable of improving the coupling efficiency with an LD array, and an optical fiber array that does not contaminate the LD array when operated in combination with the LD array, and a method of manufacturing the same. The purpose is to provide a method.

[0010]

According to the present invention, there is provided a fiber alignment block comprising:
A plurality of silica-based optical fibers, which are fixedly arranged on the fiber alignment block and whose tip working surface is exposed from the end face of the fiber alignment block, have the tip working face and the end face of the fiber alignment block. Is the same for all quartz optical fibers, and a lens portion is formed on the tip working surface, and a metal plating layer is formed on all surfaces except the tip working surface. An optical fiber array is provided, and a step of fixing and arranging a plurality of silica-based optical fibers in a fiber alignment block in a state where the tips thereof protrude from the end surface of the fiber alignment block (hereinafter, referred to as The first step);
Forming a metal plating layer by covering the entire surface of the fiber alignment block and the entire surface of the protruding portion of the quartz optical fiber (hereinafter, referred to as a second step); A step of forming the tip working surface of the silica-based optical fiber by batch polishing and, at the same time, adjusting the protrusion length of the tip to the same length (hereinafter referred to as a third step);
In addition, there is provided a method for manufacturing an optical fiber array, comprising a step of forming a lens portion on the distal end working surface (hereinafter, referred to as a fourth step).

[0011]

In the optical fiber array of the present invention, when the silica-based optical fibers are arranged in a fiber alignment block,
Even if the projection lengths of these silica-based optical fibers from the end face of the fiber alignment block are not uniform, the projections of these silica-based optical fibers are collectively polished in the third step. The position of the working surface is the same for all quartz optical fibers with respect to the end face of the fiber alignment block. Therefore, the position of the lens portion formed on the front working surface in the fourth step is the same for all the quartz optical fibers. Therefore, this optical fiber array is
When assembled in an array module, the distance between each LD light source and the lens portion of each silica-based optical fiber is the same for all silica-based optical fibers, and the variation in coupling efficiency is eliminated.

In the second step, since the entire surface of the fiber alignment block is covered with the metal plating layer, the metal plating layer functions as a barrier against gas generated from the fiber alignment block, and as a result, during operation, No gas is generated, and contamination of the LD array can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 First, in the first step, as shown in FIG. 1, each fiber insertion hole 1a of the fiber alignment block 1 in which a plurality (four in the figure) of fiber insertion holes 1a are formed.
The silica-based optical fibers 2 are inserted, and are arranged in a state where the tips thereof are projected.

Here, the fiber alignment block 1 is preferably made of a resin such as an epoxy resin. Then, by machining the resin bulk body, fiber insertion holes 1a are drilled with high precision at a pitch of, for example, 250 μm. The fiber alignment block 1 can be formed and formed like a conventional multi-core optical connector.

The optical fibers 2 inserted into the respective fiber insertion holes 1a are respectively fixed to the fiber insertion holes 1a by, for example, an epoxy adhesive 3. At this time,
The length of the optical fibers 2 projecting from the end face 1b of the fiber alignment block 1 does not need to be the same for all the optical fibers 2, and may be different from each other as shown in FIG.

When a quartz optical fiber is immersed in an etchant such as a hydrofluoric acid solution or a mixed solution of hydrofluoric acid and ammonium fluoride, the cladding has a higher etching rate than the core. Such an optical fiber is used. Examples of such optical fibers include the following.

First, the first optical fiber has a core made of pure quartz glass (SiO ₂ ), and a clad surrounding the core is made of glass having a composition in which quartz glass is doped with a fluorine component. As another optical fiber, a core is formed by doping GeO ₂ into quartz glass. 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 is determined by an appropriate difference in the etching rate between the clad and the core when the end face of the optical fiber is immersed in an etchant. It becomes a trapezoidal (or conical) protruding state, which is adjusted so as to exert an appropriate lens function. At the same time, adjustment is made 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 preferably about 0.3 to 0.4%.

The clad may be formed by mixing a phosphorus component instead of a fluorine component, or by mixing a phosphorus component in addition to the fluorine component. Furthermore, when the core is not pure silica glass but has a composition in which a germanium component such as a fluorine component or GeO ₂ is mixed, the cladding is formed within a range that does not affect the optical transmission characteristics. By mixing many fluorine components described above, the etching rate for the etchant may be made different between the core and the clad.

The same applies to the case of the latter optical fiber. The doping amount of the germanium component into the core is determined by an appropriate difference in the etching rate between the core and the clad when the end face of the optical fiber is immersed in an etchant. The frusto-conical shape (or conical shape) of the obtained core is adjusted so as to exert an appropriate lens function. Then, in the second step, as shown in FIG. 2, the entire surface of the fiber alignment block 1, the entire surface of the projecting portion of the optical fiber 2, and the entire surface of the rear end portion of the optical fiber 2 are covered. Metal plating layer 4
To form By forming the metal plating layer 4, even if gas is generated in the fiber alignment block 1, the gas is prevented from escaping to the outside.

The metal plating layer 4 is formed, for example, by applying conventional electroless plating to a place where a metal plating layer is to be formed and imparting conductivity to the place, and then forming a normal layer on the electroless plating layer. Can be formed as an electrolytic plating layer having a desired thickness. The metal plating layer 4 is made of a material that is not eroded by an etchant used when forming a lens portion in a fourth step described later. For example, a nickel plating layer can be given.

Although the thickness of the metal plating layer 4 is not particularly limited, the length of the protruding portion of the optical fiber 2 may be reduced by about 20 μm when a lens portion described later is formed. However, considering that the lens portion protrudes from the end face 1b of the fiber alignment block 1, it is preferable that the thickness be approximately 50 μm. Next, in the third step, the tips of the optical fibers 2 protruding from the fiber alignment block 1 are polished at once.

At this time, as shown in FIG. 3, the end face 1b of the fiber alignment block 1 is covered with a resin so that the base of the tip of the optical fiber 2 is buried. , It is preferable to perform a reinforcing process for fixing the entire optical fiber 2 with the resin layer 5.
In addition, as shown by the imaginary line in FIG. 3, the distal end portion of each optical fiber 2 may be entirely buried in the resin layer 5.

As the resin to be used, for example, an ultraviolet curable resin or a thermosetting resin can be used. After the resin is applied to the end face 1b, the resin is irradiated with ultraviolet light or heated to be cured, whereby the distal end of the optical fiber 2 is fixed while maintaining its protruding state. After the above-mentioned collective polishing, as shown in FIG. 4, the tips of the optical fibers 2 that have irregularly protruded are polished and removed, and the polished surface of the metal plating layer 4 and the polished surface of the resin coating layer 5 are removed. The polished surface 2a of the fiber 2 forms the same plane. That is, the polished surface 2a of all the optical fibers 2 is exposed as the tip working surface, and the position thereof is a position protruding from the end surface 1b of the fiber alignment block 1 by the same length.

Thereafter, a resin coating layer 5 covering the end face 1b is formed.
It is removed. As a result, as shown in FIG. 5, the tip of the optical fiber 2 protrudes from the end face 1b of the fiber alignment block 1, but the position of the tip working surface 2a in each optical fiber is determined by the end face 1b of the fiber alignment block 1. Is the same for all optical fibers based on Then, the fourth
In the process, a lens portion is formed on the distal end working surface 2a of the optical fiber.

Specifically, the tip of the optical fiber 2 is immersed in an etchant such as a hydrofluoric acid solution or a mixed solution of hydrofluoric acid and ammonium fluoride. When the tip of the optical fiber is immersed in these etchants, the cladding and the core are both etched because they are quartz glass. At this time,
The etching rate of the clad is higher than the etching rate of the core.Moreover, the etching proceeds in the axial length direction of the optical fiber to shorten the optical fiber and the etching proceeds in the radial direction of the optical fiber to make the optical fiber thinner. Since it proceeds in a synthesized state, after a predetermined period of time, the projection length of the optical fiber 2 becomes shorter as a whole, and at the same time, the core projects on the end face of the optical fiber in the shape of a truncated cone, As shown in FIG. 6, a lens portion 2b is formed on the distal end working surface 2a of the optical fiber 2.

During the etching process, the protruding length of the tip of the silica-based optical fiber is shortened by about 20 to 30 μm. Therefore, before the etching, the metal plating layer covering the tip of the optical fiber is removed by 20 to 30 μm. It is preferable to remove it in a length of about 30 μm. In this etching process, the etching conditions acting on the distal end of each quartz optical fiber 2 are the same, so that the protruding length of the distal end protruding from the end face 1b is the same for all the quartz optical fibers 2. .

When the frusto-conical portion of the protruding portion (lens portion) 2b is irradiated with, for example, a condensed laser beam and heated and melted, the frusto-conical shape can be changed to a spherical lens. Embodiment 2 FIG. 7 shows another embodiment of the optical fiber array of the present invention.

In this optical fiber array, the tip working surface 2a of the optical fiber 2 is recessed from the outer surface 4a of the metal plating layer 4. When the optical fiber array is optically coupled to, for example, an LD array, the lens portion 2b
Is not in contact with the light emitting surface of the LD array, and therefore, during the optical coupling process between the two, L
There is an advantage that the danger of damaging the D array can be completely eliminated.

In this optical fiber, after proceeding to the third step in the same manner as in the first embodiment, the amount of etching of the optical fiber with respect to the tip working surface is controlled when the lens portion is formed in the fourth step. Can be manufactured.

[0031]

As is apparent from the above description, according to the method of the present invention, when the optical fibers are arranged in the fiber alignment block, the lengths of the optical fibers projecting from the end faces of the fiber alignment block are not uniform. Even if it does, finally, it is possible to manufacture an optical fiber array in which all the optical fibers have the same protruding length and a lens portion is formed on the front working surface thereof. Therefore, the complicated operation of aligning the ends of the optical fibers one by one and arranging them in the fiber alignment block as in the related art can be eliminated.

Further, when the obtained optical fiber array is coupled to an LD array, the coupling efficiency becomes higher, and since the protruding length of each optical fiber is the same, the coupling efficiency between each LD and each optical fiber is increased. There is no variation between them. Therefore, a very excellent LD array module can be assembled. In addition, since the surface of the fiber alignment block is covered with the metal plating layer, contamination of the LD array caused by gas generated from the fiber alignment block is prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which optical fibers are arranged in a fiber alignment block.

FIG. 2 is a cross-sectional view showing a state where a metal plating layer is formed.

FIG. 3 is a cross-sectional view showing a state in which the distal end of the optical fiber is fixed.

FIG. 4 is a cross-sectional view showing a state after a polishing process.

FIG. 5 is a sectional view showing a state where a resin coating layer is removed.

FIG. 6 is a cross-sectional view showing a state where a lens portion is formed.

FIG. 7 is a partial cross-sectional view showing a tip working surface of another optical fiber array according to the present invention.

FIG. 8 is a cross-sectional view showing a conventional light emitting element module.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fiber alignment block 1a fiber insertion hole 1b end face of fiber alignment block 1 2 optical fiber 2a polished surface of optical fiber 2 (tip working surface) 2b lens portion 3 adhesive 4 metal plating layer 4a outer surface of metal plating layer 4 5 resin Coating layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-318503 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/42 G02B 6/10 G02B 6 / 36

Claims (4)

(57) [Claims] 1. A fiber alignment block, comprising: a plurality of silica-based optical fibers fixedly arranged on the fiber alignment block and having a tip working surface exposed from an end face of the fiber alignment block; The distance between the working surface and the end surface of the fiber alignment block is the same for all silica-based optical fibers, and a lens portion is formed on the front working surface, and all surfaces except the front working surface are used. An optical fiber array, wherein a metal plating layer is formed on the optical fiber array. 2. The optical fiber according to claim 1, wherein the quartz optical fiber is made of a material having a composition in which the etching rate of the core with hydrofluoric acid or a mixed solution of hydrofluoric acid and ammonium fluoride is lower than the etching rate of the cladding. Fiber array. 3. A step of fixing and arranging a plurality of silica-based optical fibers on a fiber alignment block with their tips protruding from the end surface of the fiber alignment block; the entire surface of the fiber alignment block; Forming a metal plating layer by covering the entire surface of the protruding portion of the silica-based optical fiber; simultaneously polishing the distal end of the silica-based optical fiber to form the distal end working surface of the silica-based optical fiber; A method for manufacturing an optical fiber array, comprising the steps of: adjusting a projecting length of a distal end portion to the same length; and forming a lens portion on the operating surface of the distal end. Wherein said silica-based optical fiber, light of claim 3 towards the core etching rate of the by mixed solution of hydrofluoric acid or hydrofluoric acid and ammonium fluoride is made of a material smaller composition than the etching rate of the cladding Fiber array manufacturing method.