JP2005164886A - Optical fiber guide and optical element module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber guide in which the end face of an optical fiber (or a fiber collimator), which is diagonally polished, is easily positioned. <P>SOLUTION: The optical fiber guide is constituted so that the end of the optical fiber of which the end face is diagonal to the axis is positioned and fixed on a substrate and a luminous flux propagated in the air is made incident or emitted. The optical fiber guide comprises: a groove for mounting the optical fiber, the cross section of which is formed in a rectangle, provided on the face of the substrate; a wall face for butting the end face of the optical fiber, which is provided at the end of the groove in such a manner that the wall face is diagonal with respect to the groove axis at the same angle as that of the diagonal end of the optical fiber with respect to the axis and the normal line of the diagonal wall face is in parallel to the face of the substrate; a slit formed at the center of the wall face for butting for incidence and emission of the luminous flux propagated in the air; and a pressing plate which pressurizes the optical fiber mounted in the groove downward. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical axis of a light beam that enters and exits through an end surface of an optical device having an optical fiber end fixed on a substrate and the optical fiber end having a movable part such as an optical switch or a variable optical attenuator. It is related with the optical fiber guide which positions and fixes.

In an apparatus for fixing an optical fiber end portion and emitting a light beam into the air and fixing or entering the optical fiber, as a conventional device having a configuration in which the optical fiber end face is abutted against a wall surface and passively positioned, for example, As described in Patent Documents 1 and 2, there is a module whose optical fiber end face corresponds to a vertical end face.
However, when there is a coupling site with aerial propagation in the optical fiber optical system, it is generally desirable to cut the end face obliquely in order to prevent re-coupling to the reflected return optical transmission line at the fiber end face.
On the other hand, if the end face of the optical fiber is inclined, the optical axis of the light beam emitted or incident from it is deflected according to the direction of the inclination of the end face from the axis of the optical fiber. In order to achieve coupling, it is necessary to adjust the angle with respect to the azimuth around the axis.

For this reason, basically, as described in Patent Document 3, for example, an optical fiber ferrule is subjected to marking and the like, and an angle alignment is performed with respect to rotation around the axis.
As inventions that enable an optical fiber having an obliquely inclined end face to be passively positioned without the step of adjusting the angle as described above, there are various inventions as described in Patent Documents 4 to 9.
Since the invention described in Patent Document 4 has a configuration in which a gap between the optical fiber end face and the optical component to be coupled is filled with a translucent resin, an optical switch or the like to which the present invention is mainly applied It cannot be applied to an apparatus in which an optical device having a movable part is arranged in an air propagation optical path.
Next, the invention described in Patent Document 5 fixes the optical fiber because the inclination is provided in the depth direction with respect to the substrate surface, together with the difficulty of forming a groove inclined at a specific angle on the substrate. When pressing the optical fiber in the axial direction and pressing the end face against the inclined wall, a force acts in the direction that the end of the optical fiber jumps out to the upper surface of the substrate along the slope, There has been a problem that a positional shift occurs in the vertical direction.

Furthermore, the inventions described in Patent Documents 6 and 7 are devices that perform coupling with an optical waveguide instead of an aerial propagation optical path. On the other hand, since it is formed in the depth direction, it has a problem that the end portion is liable to be displaced in the vertical direction as in the case of the invention described in Patent Document 5.
Patent Documents 8 and 9 describe inventions having a configuration in which an inclination is provided in the direction in the substrate, but these are both devices for coupling an optical fiber and an optical waveguide, and particularly for coupling with an air propagation optical path. Application to an optical device having a movable part is impossible.
Japanese Patent No. 2817778 Japanese Patent Laid-Open No. 10-253856 JP 2000-338363 A Japanese Patent Laid-Open No. 2001-21775 Japanese Patent Laid-Open No. 3-93285 Japanese Patent Laid-Open No. 1-261604 JP-A-5-188234 JP-A-5-22404 JP-A-8-122561

When light emitted from an optical fiber having an oblique end face is coupled to another optical fiber as a countermeasure against returning light, the direction of the inclined surface needs to be set to a certain condition. For this reason, an angle adjusting step around the axis is particularly required, and the work of fixing the end face of the optical fiber becomes a difficult work.
An object of the present invention is a light that can accurately position and fix an optical fiber end portion having an oblique end surface necessary as a countermeasure against return light with respect to an aerial propagation optical path without requiring an angle alignment process around the axis. It is an object of the present invention to provide a fiber guide and an optical element module configured using the optical fiber guide.

An optical fiber guide that positions and fixes an end portion of an optical fiber whose end face is inclined with respect to an axis on a substrate and measures the entrance and exit of a light beam propagating in the air,
An optical fiber mounting groove formed on one surface of the substrate and having a rectangular cross section, and provided at the end of the optical fiber mounting groove, the angle with respect to the axis of the oblique end surface formed on the end surface of the optical fiber is the same At the center of the groove width of the groove of the end face abutting wall surface and the end face abutting wall face that is inclined with respect to the groove axis at an angle of An optical fiber guide provided with a formed slit for entering and exiting an airborne light beam is proposed.

  In the present invention, a plurality of optical fiber placement grooves are formed in such a posture that the end face abutting wall faces the optical fiber guide, and the end faces are inclined in each of the plurality of optical fiber placement grooves. Each end face of the optical fiber comes into contact with the end face abutting wall formed in each optical fiber placement groove and is pressed by the presser plate, and is mounted between the presser plate and the substrate. An optical fiber is fixed inside the mounting groove, and an aerial propagation path of light that propagates light from one side of the optical fiber to the other through a slit between the end face abutting wall surfaces arranged in a facing position. An optical element module having a space for formation and having an optical device arranged in the middle is proposed.

  According to the optical fiber guide of the present invention, the end face abutting wall surface having the same angle as the oblique end face of the optical fiber is provided at one end of the optical fiber placement groove formed on the substrate. Insert the end face into the optical fiber mounting groove with the end face almost parallel to the end face abutting wall surface, with the faces slightly separated from each other, and press the optical fiber with the presser plate from the top after insertion. Is moved toward the end surface abutting wall surface, and the end surface of the optical fiber is abutted against the end surface abutting wall surface. To be implemented.

  Therefore, in the present invention, the end portion of the optical fiber is fixed in a predetermined condition, that is, in a state where the direction of the inclined surface attached to the end surface of the optical fiber is aligned in a predetermined direction without performing the angle adjusting process in the direction around the axis. As a result, the optical fibers fixed in a posture facing each other on the substrate can be simply and reliably optically coupled. By disposing an optical device such as a movable mirror or a filter between optical fibers that are optically coupled in this facing orientation, an optical element module that performs an optical switch or light amount adjustment can be configured. There is an advantage that the optical element module can be easily manufactured.

  The structure of the substrate used in the optical fiber guide of the present invention will be described with reference to FIGS. For example, a silicon substrate is used as the substrate 10, and a plurality of optical fiber placement grooves 11 </ b> A to 11 </ b> D are formed on one surface of the substrate 10 by a manufacturing method described later. Each of the optical fiber placement grooves 11A to 11D has a substantially rectangular cross section, and the depth of the groove is shallow to about 70 to 80% of the diameter of the fiber to be placed. One end of each of the optical fiber placement grooves 11A to 11D is opened at the peripheral edge of the substrate 10, while the other end is terminated inside the substrate 10, and an end surface abutting wall surface and a slit 13 are formed at the termination portion. It is formed. The embodiment shown in FIG. 1 shows a case where four optical fiber placement grooves 11A, 11B, 11C, and 11D having a cross-like cross section and a substantially rectangular cross section are formed on the surface of a substantially square substrate 10. These four optical fiber mounting grooves 11A to 11D have end-to-end relations. In the example shown in FIG. 1, 11A and 11C and 11B and 11D are parallel to each other. It is formed slightly shifted in the axial direction. This deviation of the axis is an influence due to the inclination of the end face of the optical fiber for the reason described above. The amount of deviation of the axis is determined by the angle of the inclined surface attached to the end face of the optical fiber. The angle of the inclined surface attached to the end face of the optical fiber (the angle formed between the optical axis of the optical fiber and the perpendicular line) is generally selected in the range of about 2 ° to 10 °. In general, about 6 ° is often used.

The wall surface of the end face abutting wall surface 12 formed at the end of each of the optical fiber placement grooves 11A to 11D is also formed to be inclined with respect to the axis of each of the optical fiber placement grooves 11A to 11D. This inclination angle is the same as the inclination angle attached to the end face of the optical fiber 20. The end face abutting walls 12 facing each other are formed so that the wall surfaces thereof are parallel to each other, and each end of the end face abutting wall surfaces 12 facing each other is formed by the formation of the parallel end face abutting wall surfaces 12. The bent portion having an acute angle and the bent portion having an obtuse angle are arranged diagonally to each other.
When the angle of the inclined surface attached to the end face of the optical fiber is determined, the amount of deviation of the axes of the optical fiber placement grooves 11A to 11D can be calculated. Accordingly, the positions of the optical fiber placement grooves 11 </ b> A to 11 </ b> D obtained by this calculation (mainly the shift amount of the axis) are faithfully reproduced on the substrate 10, and the reproduced optical fiber placement grooves 11 </ b> A to 11 </ b> D are reproduced. If an optical fiber is mounted, each optical fiber is guided and arranged in a state where the optical axes coincide with each other, and an optical element module can be manufactured without adjustment.
The method for calculating the position of each of the optical fiber mounting grooves 11A to 11D from the angle of the inclined surface attached to the end face of the optical fiber is not the essence of the present invention. It is.

3 to 8, the description will be given of the fact that the end face of the optical fiber is accurately positioned following the slope of the end face abutting wall surface 12 formed on the substrate 10 when the optical fiber which is a feature of the present invention is mounted. To do.
3 to 8 show a process of mounting the optical fiber on the optical fiber guide according to the present invention. In each figure, A is a plan view of the optical fiber guide, and B is a side view. Here, one of the optical fiber placement grooves 11A to 11D shown in FIG. 1 is representatively shown as the optical fiber placement groove 11, and a method of mounting the optical fiber 20 will be described.

Step 1
An optical fiber 20 (which may be a short graded index fiber portion whose tip is fusion-spliced) is gripped by a jig (not shown) above the substrate 10 and the end face is inclined from above. The image is recognized and the rotational angle around the axis is roughly adjusted so that the end surface is substantially perpendicular to the substrate surface, and the tip of the optical fiber 20 and the end surface abutting wall surface 12 are positioned above the optical fiber placement groove 11. Hold a little distance (see FIG. 4).
Step 2
In the state of FIG. 4, the optical fiber 20 is pressed from above with a pressing plate 30 made of, for example, a glass plate, and the optical fiber 20 is pushed into the optical fiber placement groove 11 (see FIG. 5).

Step 3
With the pressing plate 30 applying a pressing force to the optical fiber 20, the optical fiber 20 confined in the optical fiber placement groove 11 is pushed in the axial direction, and its tip surface advances toward the end surface abutting wall surface 12. Then, the end surface is pressed against the end surface abutting wall surface 12 (see FIG. 6).
In this step 3, the angle error as the remainder of the coarse adjustment of the angle alignment around the axis of the optical fiber in the step 1 is absorbed and compensated by a slight twist of the optical fiber 20 itself, and the end face of the optical fiber 20 is for end face abutment. It follows the surface of the wall surface 12 until it completely coincides.

This automatic adjustment of the angle error is caused by the movement of the optical fiber 20 being constrained in all directions in a plane perpendicular to the axis by the optical fiber placement groove 11 and the presser plate 30. In particular, since the diameter of the optical fiber 20 is selected to be larger than the depth of the groove 11, if the oblique end face is coarsely adjusted with an error in the direction in which the oblique end face is inclined relatively downward as a result of the steps 1 and 2, it is assumed to be oblique. Further, the sharp tip portion of the end portion of the optical fiber is positioned further above the upper side of the end face abutting wall surface having the same height as the groove depth. Here, if the optical fiber 20 is advanced in the axial direction without being pressed by the presser plate 30, the optical fiber 20 moves up above the abutting wall surface and induces rotation around the axis to automatically adjust the angle. Cannot cause exercise to achieve. Therefore, the action of restraining the movement of the optical fiber 20 by the optical fiber placement groove 11, in particular, the side wall surface on the side that forms an acute angle with the end face abutting wall surface and the presser plate 30 from above is an object of the invention. Is essential for.
It is a unique effect of the present invention that the natural twist of the optical fiber 20 is used to easily realize high-accuracy angle alignment, which is difficult with conventional active angle alignment.

Step 4
A UV curable adhesive 31 is poured into a gap (about 30 μm) between the pressing plate 30 and the substrate (see FIG. 7). The adhesive 31 is cured to the adhesive layer 32 shown in FIG. 8 by irradiating ultraviolet rays, the positioning and fixing are completed, and the pressing to the presser plate 30 is released. The liquid phase adhesive may be applied after step 2 described above, and after acting as a lubricant for the movement of the optical fiber 20 in the groove 11 in step 3, it may be cured by irradiation with ultraviolet rays after positioning. .
From the above, the positioning state of the tip of the optical fiber 20 which is a feature of the present invention can be understood. Below, the formation method of the optical fiber mounting groove | channel 11, the end surface butting wall surface 12 and the slit 13 to the board | substrate 10, and the practical example of this invention are demonstrated.

A method of forming the optical fiber placement groove 11, the end face abutting wall surface 12, and the slit 13 in the substrate 10 will be described with reference to FIGS. 9 to 12. In each figure, A is a plan view and B is a cross-sectional view.
As the substrate 10, for example, a silicon substrate having a two-layer structure can be used. The first silicon layer 10A is selected to have a thickness corresponding to the depth of the optical fiber mounting groove 11, the first insulating layer 10C is formed on the surface, and the second insulating layer 10D is formed on the lower surface. The A second silicon layer 10B is formed on the lower surface side of the second insulating layer 10D. This second silicon layer 10B has the strength of the portion where the optical fiber mounting groove 11 is formed.

Process 1
The insulating layers 10C and 10D are silicon oxide films, and a resist layer 14 made of, for example, a photocurable resin is attached to the upper surface of the insulating layer 10C, and the shape of the optical fiber placement groove 11 is formed on the resist layer 14. Then, the shape of the end surface abutting wall surface 12 and the shape of the slit 13 are patterned by photolithography, and the resist layer 14 in a portion to be removed by etching is removed (see FIG. 9).
Process 2
Dry etching is performed using an RIE (reactive ion etching) apparatus, and the insulating layer 10C exposed from the resist layer 14 is removed (see FIG. 10).

Process 3
After the exposed insulating layer 10C is removed by etching, the resist layer 14 is removed (see FIG. 11).
Process 4
Using the oxide film 10C as a mask, an ICP (inductively coupled plasma) etching apparatus is used to carry out deep RIE etching to form an optical fiber mounting groove 11 having a vertical wall surface having a depth required for the silicon layer 10A, an end surface abutting wall surface 12, and A slit 13 is formed. Although deep etching can be performed by a conventional RIE technique depending on the temperature condition of the substrate and the plasma condition, it is convenient to use an ICP apparatus (see FIG. 12).

In the V-groove processing method using anisotropic etching often used for positioning of the optical fiber on the silicon substrate, the optical fiber mounting groove 11 having a vertical wall surface and the end face protrusion are used to solve the problem of the present invention. The abutting wall surface 12 and the slit 13 cannot be formed.
FIG. 13 shows an example of numerical values of dimensions of the optical fiber mounting groove 11. The width W of the optical fiber mounting groove 11 is set to W = 126 μm when the diameter of the optical fiber 20 is 125 μm, and the depth D is set to about 100 μm, which is shallower than the diameter of the optical fiber 20. The angle θ of the end surface abutting wall surface 12 is shown here when θ = 6 °.

FIG. 14 and FIG. 15 show Example 1 of an optical element module in which an optical fiber is mounted on a substrate 10. In this embodiment, an example is shown in which a movable mirror 40 is arranged at the center of four optical fibers 20A to 20D arranged in a cross shape, and an optical switch is configured to move the movable mirror 40 and switch an optical path.
In the case of configuring an optical switch, since the optical propagation path length in the air is relatively long, a collimator is attached to the tip of the optical fiber 20 so as to have a condensing performance, and a parallel light flux can be input and output. desirable. The specific structure is a length corresponding to the designed focal length after a graded index optical fiber having the same diameter as the transmission optical fiber is fused and connected to the tip of the transmission optical fiber. It can be realized by cutting the remaining portion and making the cut end face oblique. The graded index type optical fiber can be used as a cylindrical lens as it is, and acts as a collimator. Here, although an optical fiber with a collimator is used, the following description will be simply referred to as an optical fiber.

  The movable mirror 40 is arranged so as to be able to rise and fall in the thickness direction of the plate of the substrate 10, and exists in the aerial propagation path of light formed between the optical fibers 20 </ b> A to 20 </ b> D at the raised position. It is excluded from the air propagation path. FIG. 14 shows a state in which the movable mirror 40 is in the raised position. In this state, for example, light emitted from the optical fiber 20A is reflected by the movable mirror 40, enters the optical fiber 20B, and an optical signal is transmitted from the optical fiber 20A to the optical fiber 20B. At this time, the light emitted from the optical fiber 20D is reflected by the movable mirror 40, enters the optical fiber 20C, and an optical signal is transmitted from the optical fiber 20D to the optical fiber 20C.

FIG. 15 shows a state in which the movable mirror 40 exists at the lowered position. In this case, since the movable mirror 40 does not exist on the light propagation path, the light emitted from the optical fiber 20A enters the optical fiber 20C, and an optical signal is transmitted from the optical fiber 20A to the optical fiber 20C. The light emitted from the optical fiber 20D enters the optical fiber 20B, and an optical signal is transmitted from the optical fiber 20D to the optical fiber 20B.
As described above, according to the optical element module shown in FIG. 14 and FIG. 15, an optical switch for switching the optical signal path can be configured. According to the present invention, such an optical switch can be easily manufactured. be able to. In particular, since the optical fiber placement grooves 11A to 11D, the end surface abutting wall surface 12 and the slit 13 are formed by etching, each of these elements can be manufactured with high precision and uniformity, so that the optical fiber is mounted on the substrate 10. In this state, the optical coupling between the optical fibers is set to the best state, and a large number of optical element modules having uniform characteristics can be manufactured.

  FIG. 16 shows a second embodiment. In this embodiment, an optical element module in which an optical filter 50 for adjusting the amount of light is interposed between optical fibers is shown. Even in the case of manufacturing such an optical element module, the optical fiber 20 is inserted into the optical fiber mounting groove 11 formed on the substrate 10, and the optical fiber 20 is merely abutted against the end surface abutting wall surface 12. Since the optical axis of 20 coincides with the optical axis of the counterpart optical fiber and is fixed, manufacturing is easy.

  The above-described optical fiber guide and optical element module according to the present invention are practically used in the field related to optical communication.

The top view for demonstrating the structure of the board | substrate used for the optical fiber guide of this invention. The side view of the board | substrate shown in FIG. FIG. 2A is a plan view and B is a side view for explaining a step of mounting an optical fiber on the substrate shown in FIG. 3A is a plan view and B is a side view for explaining a step subsequent to the step shown in FIG. FIG. 5A is a plan view and B is a side view for explaining a step subsequent to the step shown in FIG. 4. FIG. 6A is a plan view and B is a side view for explaining a step subsequent to the step shown in FIG. 5. FIG. 7A is a plan view and B is a side view for explaining a step subsequent to the step shown in FIG. 6. FIG. 8A is a plan view and B is a side view for explaining a step subsequent to the step shown in FIG. 7. 1A is a plan view and B is a cross-sectional view for explaining the steps of the substrate manufacturing method shown in FIG. 9A is a plan view and B is a cross-sectional view for explaining a step subsequent to the step shown in FIG. FIG. 11A is a plan view and B is a cross-sectional view for explaining a step subsequent to the step shown in FIG. 10. 11A is a plan view and B is a cross-sectional view for explaining a step subsequent to the step shown in FIG. FIG. 2A is a plan view and FIG. 2B is a cross-sectional view showing numerical examples of dimensions of elements of respective portions formed on the substrate shown in FIG. The top view for demonstrating the Example which mounted the optical fiber in the board | substrate shown in FIG. 1, and constructed | assembled the optical element module. The top view for demonstrating operation | movement of the Example shown in FIG. The top view for demonstrating the other Example of an optical element module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 11, 11A-11D Optical fiber mounting groove | channel 12 End surface abutting wall surface 13 Slit 14 Resist layer 20, 20A-20D Optical fiber 30 Holding plate 40 Movable mirror

Claims (2)

An optical fiber guide for positioning and fixing an end portion of an optical fiber whose end face is inclined with respect to an axis on a substrate, and for entering and exiting an airborne light beam,
An optical fiber mounting groove having a rectangular cross section formed on the plate surface of the substrate;
Provided at the end of the groove, and inclined with respect to the axis of the groove at the same angle as the axis of the oblique end surface of the optical fiber, and the normal of the oblique surface is relative to the surface of the substrate A parallel wall for abutting the end face;
A slit for entering and exiting the air propagating light beam formed in the center of the wall for end face abutting,
An optical fiber guide comprising: a pressing plate that presses the optical fiber placed in the groove downward. The optical fiber guide according to claim 1 has a plurality of optical fiber placement grooves formed in a posture in which the end face abutting wall faces each other, and the end faces are inclined in each of the plurality of optical fiber placement grooves. Each optical fiber end face is in contact with the end face abutting wall formed in each optical fiber placement groove and is pressed and placed by the press plate, and the press plate and the substrate are bonded together, An optical fiber is fixed inside each optical fiber mounting groove, and light is propagated from one end of the optical fiber to the other through the slit between the end face abutting wall surfaces arranged in the facing orientation. An optical element module comprising: a space for forming an aerial propagation path of light to be transmitted; and an optical device disposed in the space.

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