JPH04152308A - Optical fiber device and optical fiber fixing method - Google Patents

Abstract

PURPOSE:To stabilize the fixation of an optical fiber by fixing a base substance to a fixing part in a state heated to the highest working temperature or above at the time of racking and providing the optical fiber to the fixing part of the base substance having a linear expansion coefficient being larger than that of the optical fiber. CONSTITUTION:The tip of an optical fiber 2 is subjected to optical axis alignment to an optical element 1, and thereafter, to a first fixing part 3 on a base substance 5, the fiber 2 is fixed by soldering. Subsequently, the base substance 5 is heated to the prescribed temperature of the highest working temperature or above, the fiber 2 is racked and provided linearly between a first and a second fixing parts 3, 4 and the fixing part 4 is fixed by soldering. Next, when heating of the base substance 5 is stopped it is returned to an ordinary temperature, a natural deflection is generated in the fiber 2 and an immoderate stress is not applied to the fiber 2. In such a manner the fixation of the optical fiber is stabilized by a simple working method and the damage of the optical fiber can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device and method for fixing an optical fiber that is easily damaged mechanically within an optical device, and particularly relates to an optical fiber that is easily damaged mechanically. The present invention relates to an optical fiber device and an optical fiber fixing method that are important in manufacturing fiber optical coupling modules.

[Conventional technology]

In recent years, with the practical application of optical communication technology, there has been a demand for the development of high-performance optical semiconductor modules (hereinafter referred to as "optical modules") that obtain optical output from optical fibers with high coupling efficiency.

FIG. 4 shows a conventionally used fiber direct coupling type optical module.

This optical module directly receives the output beam from the optical element 1 at the core of the optical fiber 2, so the structure is simple and the number of parts is small, so it can be mounted at low cost.

To assemble this optical module, the surface of the optical fiber core wire is metallized for metal fixation, and the optical axis is aligned by moving the optical fiber 2 using a precision fine movement device to the positional relationship that optimally couples the optical element 1 and the optical fiber 2. After supplying solder material to the metallized portion of the optical fiber 2 in the first fixing part 3 and melting and fixing it by heating means such as a YAG laser, the second fixing part 4 fixes the casing ("substrate"). (Also referred to as ``.'') Fix the optical fiber penetration part 5 with solder material without any gaps.

In addition, the above-mentioned YAG
In addition to laser heating, solder melting using a self-heating element can also be used.

Furthermore, in order to prevent performance deterioration of the optical element l and obtain long-term stability, M9 made of Kovar or other material is applied to the opening at the top of the housing 5 by means such as a seam welder in an atmosphere of an inert gas such as nitrogen. By welding, the inert gas 10 is confined and hermetically sealed.

When the entire optical module is subjected to changes in ambient temperature, stress is generated in the solder fixing parts and optical fibers due to the difference in linear expansion coefficient of the component parts, and coupling loss due to creep of the solder material and optical axis shift due to stress relaxation is caused. Problems such as increase in optical fibers and breakage of optical fibers occur. For example, the linear expansion coefficient of optical fiber is
Since the coefficient of linear expansion is smaller than that of the housing, when the temperature of the housing rises, the temperature between the optical fiber fixing parts (first fixing part 3 and A tensile stress is generated between the second fixing parts 4). Here, (a) shows a top view, and (b) shows a sectional view taken along line XY in (a).

In FIGS. 1(a) and 1(b), it is assumed that the optical fiber 2 is stretched at room temperature. The housing 5 expands within the range of its linear expansion coefficient as the outside temperature increases.

Generally, there is a difference in linear expansion coefficient between the housing 5 and the optical fiber 2, and if the linear expansion coefficient difference is α, then the relationship is α housing) α optical fiber.

Therefore, as shown in the cross-sectional views of FIGS.
There is a phenomenon in which the optical fiber 2 is broken between the first and second fixing parts 3 and 4 due to a tensile force acting on the
L, 5pencer+ IEEELC5+ (199
0).

20).

Therefore, conventionally, when fixing the optical fiber 2 to the housing 5, a compressive external force is applied in advance to the optical fiber 2 between the first and second fixing parts 3 and 4 in the axial direction. The central portion is bent and fixed to reduce the tensile stress applied to the optical fiber when the outside temperature rises (for example, JP-A-63-316010 ``Optoelectronic Devices and Optical Fibers'').

[Problem to be solved by the invention]

When bending the center of an optical fiber, consider the process of applying an external force so that the deformation is appropriate.
In order to perform reproducible control, a jig with a precision optical fiber feeding mechanism must be used.
In addition, it is a skilled work that requires careful attention and experience from the operator, which makes it difficult to work with, and furthermore, it is difficult to bend the optical fiber to the necessary minimum level with good reproducibility. Additionally, unnecessary stress was often applied to the optical fiber during the bending process.

Therefore, the optical fiber will not be damaged during the production of the optical module, and even if the optical fiber and the housing are repeatedly changed in the usage environment after the production of the optical module,
In order to maintain stable optical coupling over a long period of time, some effective fixing method was required.

The present invention relates to a technique for solving problems such as increased coupling loss and breakage due to external forces applied to optical fibers due to changes in the operating environment temperature applied to optical modules, using special equipment. The purpose of this paper is to provide easy and reproducible solutions to the following technical problems.

To summarize the technical challenges, (1) measures must be taken to avoid applying unnecessary stress to the optical fiber during operation; (2) measures must be taken to ensure that the optical fiber has an appropriate amount of deflection at the operating temperature. , etc.

[Means to solve the problem]

In order to solve the technical problems mentioned above, in the present invention,
Utilizes the difference in linear expansion coefficient between the optical fiber and the housing.

That is, first, the linear expansion coefficient of the casing is selected to be larger than that of the optical fiber. Next, the optical fiber is fixed at a predetermined position inside the housing. During this work, the temperature of the casing is set to be slightly higher than the operating environment temperature, and the optical fiber is maintained and fixed in a straight line in this state. in particular,
When connecting and fixing the optical fiber to the casing using the second fixing part, place the casing on a heating element such as a heater or hot plate to heat the entire optical module to a temperature slightly higher than the maximum operating temperature (for example, 80° Heat to C+10deg,)
Work to fix the optical fiber while keeping it straight.

This makes it easy to bend the optical fiber naturally when the temperature of the optical module reaches room temperature, and allows for optimal design of the amount of bending (this will be explained later using Figure 3). .

[Function] According to the present invention, when installing an optical fiber between the first and second fixing parts within the housing, the second fixing part is fixed while the entire housing is heated to a temperature higher than the maximum operating temperature. As a result, the casing temperature is natural and reproducible for optical fibers having a linear expansion coefficient smaller than that of the casing within the operating temperature range of the optical module, and the necessary minimum deflection can be caused. That is, the present invention can maintain stable optical coupling of an optical module over a long period of time, and can solve problems such as damage to optical fibers by using an easy fixing method.

〔Example〕

FIGS. 2(a) and 2(b) show two examples of light receiving modules to which the optical fiber device according to the present invention is applied.

The light receiving module shown in FIG. 2(a) has a first fixing part 3 near the light receiver 6, a second fixing part 4 at a position a little apart from the first fixing part 3, and Part 3, 4
An optical fiber 2 is installed between them, and the optical fiber 2 is fixed by soldering at each fixing part 3, 4,
The whole is housed in a housing 5. In this case, if the light receiver 6 is a laser diode (LD), it changes from a light receiving module to an LD module.

FIG. 2(b) shows an optical crystal material 7 (for example, LiNb0:
This is an LN module that functions as an optical switch or optical modulator made of a There is a second fixing part 4 at a separate position, and the optical fiber 2 is installed between the first fixing part 3 and the second fixing part 4, and the optical fiber 2 is connected to each fixing part 3. It is fixed with an adhesive at a fixing part 4, and the whole is housed in a housing 5.

As shown in the embodiments of FIGS. 2(a) and 2(b), the optical fiber according to the present invention is installed and fixed across two fixing parts 3.4 (first and second fixing parts). Regarding the fiber fixing method, Fig. 3 (a), (b), (C) (
The work process will be explained using an explanatory diagram shown in d).

In FIG. 3(a), there are a first fixing part 3 and a second fixing part (not shown) 4 for fixing the optical fiber 2 onto the housing 5 or the base 5 housed therein. . The optical axis of the tip of the optical fiber 2 is correctly aligned with the laser diode 6a. First, the optical fiber 2 is fixed to the first fixing part 3. If the optical fiber 2 is subjected to metallization treatment, it can be fixed by soldering. This work can be done at room temperature.

In Figure 3 (bl), the substrate 5 is placed on a heater or hot plate and heated.The substrate temperature is slightly higher than the maximum operating temperature of the final product, such as the light receiving element, LD module, LN module, etc. For example, the standard specifies that the salinity of the environment in which the final product is used is between -10 and 80°C, so soldering above 80°C will result in temperature (soldering difficulties, p.
, 183°C) or less. In actual work, the maximum operating temperature is preferably about 10 β (10 cleg), for example.

In this temperature state, that is, the temperature at which the optical fiber is installed, the optical fiber 2 is installed between the first fixing part 3 and the second fixing part 4, as shown in FIG. Then, the optical fiber 2 is fixed by soldering at the second fixing part 4.

The optical fiber 2 fixed in this manner naturally bends as shown in Figure 3 at the operating environment temperature when removed from the heater or real plate, and no unreasonable stress is applied to the optical fiber 2. . To give numerical values for one embodiment, if the distance between the first and second fixing parts 3 and 4 is l0II11, the optical fiber installation temperature is 90°C.
The work done in the above shows a deflection of about 0.5 μm at room temperature. In the embodiment described above, the first fixing part 3 was fixed at room temperature, but the first and second fixing parts 3 and 4 may be fixed at the construction temperature.

[Effects of the Invention] In the present invention, since the optical fiber is fixed with the substrate heated to a temperature higher than the maximum operating temperature of the optical fiber device, the optical fiber naturally bends during use, making it possible to stably fix the optical fiber. Ta.

According to the present invention, (1) an optical fiber device could be manufactured by a simple operation of installing optical fibers in a straight line;

(2) Since the deflection of the optical fiber can be adjusted with good reproducibility and quantitatively, the manufacturing yield of the optical module and the reliability of environmental performance such as temperature cycles can be improved.

(3) In addition to simplifying assembly jigs and work processes, it was possible to improve productivity with inexpensive equipment.

(4) In this way, it was possible to reduce the optical fiber breakage accidents that had plagued the conventional technology, and to express this numerically, 900 FIT became less than 100 FIT.

[Brief explanation of the drawing]

Figure 1 (aL (b) is a schematic explanatory diagram of the optical module, θ)
shows a top view thereof, and (b) shows a sectional view taken along line X-Y in (a). FIGS. 2(a) and 2(b) show an embodiment of a light receiving module using the optical fiber device of the present invention, where (a) shows the light receiving module and 0)) shows the LN module. Figures 3 (a), (b), (C), (Hitoshi shows explanatory diagrams of the working steps of the optical fiber fixing method according to the present invention. Figures 4 (a) and (b) show the optical 1A shows a plan view of a fiber direct coupling type optical module, and FIG. In the figure, 1 is an optical element, 2 is an optical fiber, 3 is a first fixing part, 4 is a second fixing part, 5 is a housing (base body), and 6
is a light receiver, 7 is an optical crystal material, 8 is a reinforcing material, 9 is a lid, 10
indicates an inert gas, respectively. Patent Applicant Anri Co., Ltd. Agent Patent Attorney Ryuta Koike Part 4: Second fixed part

Claims (1)

[Claims] 1) a base (5) having a linear expansion coefficient larger than that of the optical fiber to be fixed; and a base (5) provided on the base,
An optical fiber device comprising a first fixing part (3) and a second fixing part (4) for fixing an optical fiber, wherein the first fixing part is fixed at a predetermined temperature higher than the maximum operating temperature. and an optical fiber device, characterized in that the second fixing portion holds the optical fiber in a straight line. 2) between the first fixing part (3) and the second fixing part (4) provided on the base (5) having a linear expansion coefficient larger than that of the optical fiber to be fixed; An optical fiber fixing method for fixing an optical fiber, comprising: a first step of fixing the optical fiber to the first fixing part; fixing the optical fiber to the second fixing part, and fixing the optical fiber to the second fixing part; a second step of heating the substrate and maintaining it at a predetermined temperature when fixing the optical fiber to the substrate.