JP3798408B2 - Optical monitor module - Google Patents

Description

The present invention splits the light emitted from the optical fiber, by receiving the branched light by the monitor unit, to the module for an optical monitor for monitoring the light other than the branched light that is incident on another optical fiber.

A conventional optical monitor module enters light emitted from an optical fiber into an optical waveguide of an optical waveguide substrate on which an optical branch circuit is formed, and monitors the light branched by the optical branching device from the optical waveguide substrate. It was incident on the part. This conventional technique is disclosed in, for example, Patent Document 1 and Patent Document 2.
As described above, the conventional optical monitor module has a configuration in which light is branched and monitored by the branch circuit of the optical waveguide formed on the optical waveguide substrate, so that propagation loss occurs in the optical waveguide. It was necessary to split a large amount of light. Further, the configuration of the optical branch path is Y-branch, and the two optical waveguides are arranged in a substantially right angle relationship, so that the occupied area of the optical waveguide substrate is relatively large. A configuration is also possible in which light emitted from the optical fiber is incident on the beam splitter through the space without using a branch circuit of the optical waveguide, and the transmitted light or reflected light of the beam splitter is incident on the optical fiber that propagates to the monitor unit. . In this case, there is no light loss due to the propagation of the optical waveguide, but since the distance between the optical fiber and the beam splitter is relatively large, the light beam diverges (the beam diameter becomes large), and eventually the light loss increases. In addition, the two optical fibers are arranged substantially at right angles to each other, and the occupied space is increased.
JP 2001-358362 A JP-A-6-347665

Purpose optical loss less of the present invention, and is to provide a module for small optical monitor space occupancy.

According to the present invention, the first and second optical fibers are mounted on one surface of the substrate so that the first and second optical fibers are parallel to each other by the positioning structure formed thereon, and the positions in the direction perpendicular to the surface and the arrangement direction of the optical fibers are determined. It is done. Each of the first and second optical fibers includes a lens portion formed integrally with the end portion on the same side, and a beam splitter at an intermediate portion of the extension line on the lens portion side of the first and second optical fibers. or optical filter Ru attached to the substrate. A space is provided between each of the lens portions of the first and second optical fibers and the beam splitter or the optical filter, and light emitted from the first optical fiber propagates through the space and is incident on the beam splitter or the optical filter. The light emitting direction of the lens portion of the first optical fiber, the first optical fiber so that a part of the light is transmitted, a part is reflected, and the reflected light propagates through the space and enters the second optical fiber . The light incident direction of the lens portion of the two optical fibers is selected .

  Since there is a space between the first and second optical fibers and the beam splitter or the optical filter, there is no light loss, and no light beam diverges due to the condensing action based on the lens portion at the end of each optical fiber. The first and second optical fibers are arranged in parallel and have a relatively small two-dimensional occupied space.

  An embodiment of the present invention will be described with reference to FIG. A fiber mounting portion 12 and a component mounting portion 13 are provided on one surface 11a of the substrate 11 with an interval therebetween. A plurality of optical fibers are parallel to each other in the fiber mounting portion 12, and the extension direction is the fiber mounting portion 12 and the component mounting. A positioning structure 14 is formed for positioning so as to be in the arrangement direction of the portions 13. The positioning structure 14 determines each position in the direction perpendicular to the surface 11a of the substrate 11 of the attached optical fiber and the arrangement direction of the optical fibers. One end portions of the optical fibers 21 and 22 are positioned and attached to the fiber attachment portion 12 by the positioning structure 14. A beam splitter or optical filter 31 is attached to the component attachment portion 13 in the middle of the extension lines 23 and 24 of the optical fibers 21 and 22. Hereinafter, instead of describing as the beam splitter or the optical filter 31, it is simply described in the beam splitter 31 for convenience.

Lens portions 21a and 22a having the same diameter as the optical fiber are integrally formed at the ends of the optical fibers 21 and 22 on the beam splitter 31 side, and light enters obliquely with respect to the axial centers of the lens portions 21a and 22b. It is set as the structure which radiate | emits. The light propagating through the optical fiber 21 is emitted obliquely with respect to the optical fiber axis, propagates through the space, and is collected and incident on the beam splitter 31, and a part of the light is reflected by the beam splitter 31. Light enters the lens portion 22a of the optical fiber 22 through space.
Each part will be described more specifically below. For example, a rectangular substrate of single crystal silicon is used as the substrate 11, one half of which is a fiber attachment portion 12 and the other end is a component attachment portion 13, and the fiber attachment portion 12 is etched by utilizing crystal anisotropy. The two V-grooves 14 ₁ and 14 ₂ having the same depth are formed in parallel to each other by extending in the arrangement direction of the fiber attachment portion 12 and the component attachment portion 13. In this example, the recess 15 is formed by simultaneously etching the portion between the fiber mounting portion 12 and the component mounting portion 13. The end opposite the V-grooves 14 ₁ and 14 ₂ of the component mounting section 13 is open to the outside, the optical fiber 21 and 22 attached is structured to be derived without being bent out of the substrate 11.

End of the optical fiber 21 and 22 are disposed in the V-grooves 14 ₁ and 14 _2, for example, is adhesively fixed by an adhesive. At this time, the height H1 of each core of the optical fibers 21 and 22 with respect to the surface 11a of the substrate 11 is determined, that is, the position of the optical fiber in the direction perpendicular to the surface 11a is determined, and the interval P between the cores of the optical fibers is The position on the surface 11a in the direction perpendicular to the arrangement direction of the mounting portions 12 and 13 is determined, and the optical fibers 21 and 22 are parallel to each other.
The lens portions 21a and 22a of the optical fibers 21 and 22 include, for example, a silica portion 31 and a graded-index multimode fiber portion described in US Pat. No. 6,014,483 (issued on January 11, 2000). Consists of. In the example shown in FIG. 1, each end surface of the lens portions 21a and 22a is angled, and the end surfaces are slightly shifted from the surfaces perpendicular to the axis of the lens portion. This angled processing can be performed, for example, by a technique in which the end surface of the optical fiber is polished to form an inclined surface in order to prevent light emitted from the optical fiber from being reflected and re-entered. Thus, by making each end surface of the lens portions 21a and 22a be inclined, each incident light of the lens portions 21a and 22a is inclined with respect to the optical fiber axis. In this example, the inclination angle θ ′ with respect to the axis of the lens portions 21a and 22a is the same value.

In this example, the beam splitter 31 is positioned on the center line 25 of the extension lines 23 and 24 of the optical fibers 21 and 22 so that the light incident / exit surface thereof is perpendicular to the center line 25. For example, a pair of markers 16 are arranged at equal distances from the component mounting portion 13 with the center line 25 interposed therebetween, and the beam splitter 31 is mounted on the marker 16 on the surface 11 a of the beam splitter 31. And the position in the direction perpendicular to the surface 11a is also determined. In this case, the distance x along the center line 25 from the lens portions 21a and 22a to the beam splitter 31 and the position accuracy in the extending direction of the center line 25 should be high, but the position accuracy in other directions should be so high. There is no. The marker 16 is formed by, for example, forming a metal film by photolithography and etching technique when the V grooves 14 ₁ and 14 ₂ are formed by photolithography and subsequent etching techniques. It is done. The beam splitter 31 is attached to the component attachment portion 13 after, for example, aligning both the markers 16 and both ends of the bottom surface of the beam splitter 31 using a microscope, as is done by flip chip bonding technology. What is necessary is just to mutually contact and to fix with solder. In this example, a light receiving element such as a photodiode is mounted on the component mounting portion 13 as an optical component 32 on the side opposite to the optical fibers 21 and 22 of the beam splitter 31.

In the center line 25 between the beam splitter 31 and the lens portions 21 a and 22 a of the optical fibers 21 and 22, the light entrance and exit directions of the lens portions 21 a and 22 a of the optical fibers 21 and 22 intersect at the position of the beam splitter 31. The distance x along is set as follows. That is, the following relationship is obtained in a plane parallel to the surface 11a. The refractive index of the lens portions 21a and 22a is n ', the refractive index of the optical path medium between the lens portions 21a and 22a and the beam splitter 31 is n, and the angle with respect to the plane perpendicular to the axial center of the end surfaces of the lens portions 21a and 22a. When θ ′, respectively, the angle θ of the light incident / exit directions of the lens portions 21a and 22a with respect to the direction perpendicular to the end face is θ = sin ⁻¹ (n′sin θ ′ / n) (1)
It becomes. If the light incident / exit directions of both lens portions 21a, 22a intersect at the center line 25, the intersecting angle between the center line 25 and the light incident / exit directions of the lens portions 21a, 22a is (θ−θ ′). If the distance between the axes of the fibers 21 and 22 is P, x is x = P / (2 tan (θ−θ ′)) (2)
It becomes. If P = 250 μm, θ ′ = 6 °, and n ′ = 1.5, the optical path between the lens portions 21a and 22a and the beam splitter 31 is formed in space (air), and therefore n = 1. , Θ = 9 °, and x≈2.4 mm. The positions of the optical fibers 21 and 22 in the V grooves 14 ₁ and 14 ₂ are determined with respect to the beam splitter 31 so as to be x calculated in this way. In addition, the inclination state of the end faces of the lens portions 21a and 22a is confirmed with an image, the angular positions around the axis of the lens portions 21a and 22a are adjusted, or a marker is attached to the outer periphery of the tip portion of the lens portions 21a and 22a. Angles around the axes of the optical fibers 21 and 22 so that the marker is directly above the surface 11a when viewed from the vertical direction and the inclinations of the end surfaces of the lens portions 21a and 22a with respect to the central axis 25 are opposite to each other. Determine the position. Desirably, the position of the end face of the lens portion in the length direction of the optical fibers 21 and 22 and the axial center of the fiber so that light is incident from, for example, the optical fiber 21 and the light emitted from the optical fiber 22 is maximized. Determine the angular position around and fix it. The position of the intermediate portion in the direction perpendicular to the surface 11a of the beam splitter 31 is substantially the same as the height H1 with respect to the axial center surface 11a of the optical fibers 21 and 22, and the arrangement of the optical fibers 21 and 22 of the beam splitter 31 An intermediate portion in the direction is on the center line 25.

  According to the configuration described above, the light propagating through the optical fiber 21 is refracted and emitted from the lens portion 21 a, propagates through the space, and is collected and incident on the beam splitter 31. The light incident on the beam splitter 31 is branched into transmitted light and reflected light, and the transmitted light is incident on an optical component, in this example, the light receiving element 32 and is converted into an electric signal. The reflected light from the beam splitter 31 passes through the space, enters the lens unit 22a, propagates through the optical fiber 22, and is transmitted to the outside. At this time, the output electric signal of the light receiving element 32 can be monitored to monitor the propagation light of the optical fiber 22.

Refraction when the optical fibers 21 and 22 are on the same plane parallel to the surface 11a, and when the light is emitted from the lens portion 21a of the optical fiber 21, and when the light is incident on the lens portion 22a of the optical fiber 22. Are performed in the same plane, and the positions of the lens portions 21a and 22a in the axial direction and the angular position around the axial center are related so as to satisfy the conditions of the expressions (1) and (2). Therefore, the light emitted from the lens unit 21a and reflected by the beam splitter 31 correctly enters the center of the end surface of the lens unit 21b, and the optical path between these lens units 21a and 22a and the beam splitter 31 is a space (air). Therefore, the loss can be ignored as compared with the optical waveguide, and the light converging action of the lens portions 21a and 22a prevents the light from diverging, and the overall optical loss is extremely small. Since the propagation path of the light is space, no deterioration of polarization characteristics due to light propagation in optical waveguides, the optical characteristics of the modules for their light monitoring is improved. Furthermore, there is an advantage that the waveguide substrate for the optical waveguide is not required and the number of parts is small.

It is preferable that the light emitted from the lens portion 21a of the optical fiber 21 has the light beam diameter most narrowed at the position of the beam splitter 31 and becomes thin. The optical path length between the lens unit 21a and the beam splitter 31 that is set as such may be selected from the interval P in the equations (1) and (2) and the end surface inclination angle θ ′ of the lens unit 21a. The relationship between the lens unit 22a and the beam splitter 31 is the same.
As described above, the beam splitter 31 may be a narrow beam splitter with no wavelength selectivity, which transmits a part of all wavelengths of incident light and reflects a part thereof, and is an optical filter, that is, a specific part of incident light. It is possible to use a wavelength selective material that transmits or reflects a component of a wavelength (or a band including this wavelength) and reflects or transmits the remaining wavelength component. The light transmitted through the beam splitter 31 may be propagated to the monitor unit to monitor the light transmitted through the optical fiber 21. In this case, an optical fiber may be used as the optical component 32 to transmit the light transmitted through the beam splitter 31 to the monitor unit.

FIG. 2 shows a plan view of another embodiment of the present invention. In this example, three or more parallel V-grooves 14 ₁ , 14 ₂ ,..., 14 ₆ are arranged in parallel on the surface 11a of the substrate 11 and in FIG.
Or to increase the distance between the optical fibers 21, 22 and the beam splitter 31 according to the required modules for optical monitoring, if desired to the short hidden or beam splitter 31, the position in the array direction of the optical fibers 21, 22 shifted might want, such cases two V grooves to meet the request, and select the 14 ₂ and 14 ₅ in FIG. 2 mounting the optical fiber 21 and 22. Alternatively, the beam splitter 31 has a preferable incident angle and reflection angle, and the light incident / exit directions of the lens portions 21a and 22a of the optical fiber coincide with each other, and the light incident / exit direction is the center between the optical fibers 21 and 22. Two V-grooves to be used are selected so that they intersect on the line. In this case, it is necessary to change the inclination angles θ ′ of the lens portions 21a and 22a so that the light incident / exit directions of the lens portions 21a and 22a become desired directions together with this selection. Thus, by forming three or more V-grooves, the substrate 11 can be used in common for various requirements.

FIG. 2 shows an example in which an optical fiber 33 is used as an optical component. The optical fiber 33 is also V-shaped grooves 14 _1, ..., and the same depth at the same time as 14 ₆ formation, it is formed on the component mounting portion 13 of the parallel substrate 11, the surface 11a of the optical fiber 33 and the vertical and the light Each position in the arrangement direction of the fibers 21 and 22 is determined. In this example, the end portion of the optical fiber 33 is integrally formed with a lens portion 33a, and the inclination angle θ ′ of the end surface of the lens portion 33a is the same as the inclination angle θ ′ of the end surface of each lens portion of the optical fibers 21 and 22. In addition, the angular position around the optical fiber axis is set so that the end surface of the lens portion 33a is parallel to the end surface of the lens portion 21a. The optical fiber 33 may not include the lens portion 33a. However, the end surface on the beam splitter side of the optical fiber 33 is an inclined surface so that the incident refraction angle from the beam splitter 31 to the optical fiber 33 coincides with the outgoing refraction angle of the lens portion 21a. It is also possible to monitor the light propagated through the optical fiber 22 by converting the light incident on the optical fiber 33 into an electrical signal by a light receiving element (not shown).

The positioning structure 14 for the optical fibers 21 and 22 is not limited to the V-groove but may be a square groove. For example cross-section in the plane 11a, for example, by dry etching of the reactive ions to the substrate 11 as shown in FIG. 3 is formed by rectangular grooves 14 ₁ and 14 ₂ are parallel to and the same groove width. Placing the optical fiber 21 and 22 respectively square grooves 14 ₁ and 14 _2. The diameter of the optical fiber 21 and 22 is larger than the groove width of the square grooves 14 ₁ and 14 _2, thus the optical fiber 21 and 22 as shown in FIG. 3B partially inserted into the groove 14 ₁ and 14 _2, and each not in contact with the grooves 14 ₁ and 14 ₂ of the bottom 14a. The axes of the optical fibers 21 and 22 have the same height H1 with respect to the surface 11a of the substrate 11, and the optical fibers 21 and 22 are positioned in a direction perpendicular to the surface 11a. Arranged in parallel, the distance P between the axes becomes a predetermined value, and the position of the optical fibers 21 and 22 on the surface 11a in the arrangement direction is determined. Therefore, it becomes embodiment similar effect optical monitoring module effect is obtained as shown in FIG. 1 will be readily understood.

In the above description, the inclination angles θ ′ of the end faces of the lens portions 21a and 22a of the optical fibers 21 and 22 are the same, but they may be different from each other. As the material of the substrate 11, gallium arsenide (GaAs) single crystal, crystal, glass, synthetic resin, or the like may be used. For the former two, the V-groove can be formed by wet etching utilizing crystal anisotropy. A square groove may be used. What is necessary is just to produce by dry processing by reactive ion for glass, and molding for synthetic resin. In order to make the light incident / exit directions of the lens portions 21a and 22a oblique with respect to the axial center, the end surface is not limited to be inclined, but the end surface is perpendicular to the axial center. For example, the lens portions 21a and 22a are described in the U.S. Pat. In the description, the center of the distribution of the graded-index multimode fiber portion need only be slightly shifted with respect to each core of the optical fibers 21 and 22. In the above-described embodiment, the optical path between the lens portions 21a and 22a and the beam splitter 31 is located outside the surface 11a of the substrate 11. However, the optical path is sufficiently close to the surface 11a of the substrate 11, and the optical path. Since the light beam may come into contact with the surface 11a at a part of the surface, the recess 15 is formed. However, if there is no such a risk, for example, the recess 15 may not be formed as shown by a two-dot chain line in FIG. 1C. . As shown in FIG. 3, when a rectangular groove is used, the optical fibers 21 and 22 may be positioned by the bottom surface and both side walls. Grooves 14 ₁ and 14 ₂ are V grooves, be any of rectangular grooves, the light incident and exit point of the lens portion 21a and 22a may be positioned on the substrate inwardly from a surface 11a of the substrate 11. In that case, a shallow recess 17 is provided in the substrate 11, for example, as shown by a two-dot broken line in FIG. 3A so that the concave portion 15 is provided and the mounting position of the beam splitter 31 on the surface 11 a of the substrate 11 is also inside the substrate. Form.

1A is a plan view showing an embodiment of the present invention, B is a left side view of FIG. 1A, and C is a front view of FIG. 1A. The top view which shows the other Example of this invention. A is a plan view showing still another embodiment of the present invention, and B is a left side view of FIG. 3A.

Claims (8)

A substrate on which a positioning structure for determining a position in a direction perpendicular to the optical fiber array direction and the one surface is formed on a plurality of optical fibers in parallel with each other;
On the substrate, mounted in parallel with each other by the positioning structure, on the same side, the first and second optical fiber lenses portion are integrally formed,
In the middle of the extension line on the lens part side of each of the first and second optical fibers, the light is attached to the substrate, is emitted from the lens part of the first optical fiber, and transmits a part of the incident light. A beam splitter or an optical filter that reflects a part of the second optical fiber and enters the lens part of the second optical fiber,
Optical path between each of the lens portion and the beam splitter or optical filter of the first and second optical fibers Ri space der,
The light emitting direction of the end face of the lens portion of the first optical fiber is selected as the direction of the beam splitter or the optical filter, and the light incident direction of the end face of the lens portion of the second optical fiber is set to the direction of the beam splitter or the optical filter. A module for optical monitoring , which is selected . In the optical monitor module according to claim 1,
The end faces of the respective lens portions of the first and second optical fiber to the central axis between the first and second optical fiber, the module for an optical monitor, characterized in that there is a outwardly inclined surface to each other. According to claim 1 or 2 optical monitor module according,
The positioning structure includes first and second grooves having the same shape and the same depth and arranged in parallel with each other, and the first and second optical fibers are arranged in the first and second grooves so that the positioning is performed. module for optical monitoring, characterized in that it is. In the optical monitor module according to claim 3,
Module for optical monitoring, wherein said first and second grooves are V-grooves, respectively. In optical monitor module according to claim 3,
Three or more grooves having the same shape and the same depth are formed in parallel on the substrate, and two of the grooves are the first and second grooves . module. In the optical monitor module according to any one of claims 1 to 5,
In the middle of the first and second fiber optic in the vicinity of these optical fibers and flat lines or One the one surface of the substrate and a straight line parallel, said first optical fiber lens end face of the light incident and exit direction and the module for optical monitoring of the incoming and outgoing direction of the light of the lens end face of the second optical fiber crosses, characterized in that the beam splitter or optical filter in the vicinity of the intersection is located. In the module for an optical monitor according to claim 6,
Module for optical monitoring, wherein said straight line is the center line between the first and second optical fiber. In the optical monitor module according to any one of claims 1 to 7,
Module for optical monitoring, characterized in that the optical component the light transmitted through the beam splitter or optical filter is incident is attached to the substrate.

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