Optical receptacle and optical module

This optical receptacle has first optical surfaces via which light outputted by respective light-emitting elements is inputted, a second optical surface whereby light inputted via said first optical surfaces is outputted towards an end face of a light-transporting body, a third optical surface whereby light inputted via the first optical surfaces is reflected towards the second optical surface, a plurality of first concavities formed in the surface where the second optical surface is located, and a plurality of second concavities formed in the surface where the first optical surfaces are located or a surface opposite the surface where the first concavities are located. The first concavities and the second concavities are laid out opposite each other so that the central axes thereof coincide.

TECHNICAL FIELD

The present invention relates to an optical receptacle and an optical module including the optical receptacle.

BACKGROUND ART

In optical communications using optical transmission members such as optical fibers and light waveguides, optical modules have been used, provided with a light emitting element such as a surface-emitting laser (for example, VCSEL: Vertical Cavity Surface Emitting Laser). Such an optical module includes a transmitting optical receptacle that allows light including communication information emitted from a light emitting element to be incident on an optical transmission member, or a receiving optical receptacle that allows light from the optical transmission member to be incident on a light receiving element (see, e.g., PTL 1).

FIG. 1is a perspective view of receiving optical receptacle10disclosed in PTL 1. As illustrated inFIG. 1, optical receptacle10includes a plurality of incidence surfaces12that allow light from a plurality of optical fibers to be respectively incident thereon, reflection surface14that reflects light incident on the plurality of incidence surfaces12, a plurality of emission surfaces16that emit light reflected by reflection surface14respectively toward the plurality of light receiving elements, and a pair of guide holes18disposed such that reflection surface14is interposed therebetween. The plurality of optical fibers are housed in an optical connector, and convex parts of the optical connector are inserted into guide holes18to thereby connect the plurality of optical fibers to optical receptacle10.

In optical receptacle10connected in such a manner, light emitted from the optical fiber is incident on incidence surface12to be reflected by reflection surface14toward the light receiving surface of the light receiving element, and then reaches the light receiving surface of the light receiving element through light emission surface16.

Optical receptacle10disclosed in PTL 1 is integrally molded by injection molding using a thermoplastic transparent resin. Specifically, optical receptacle10is produced by pouring the thermoplastic transparent resin into a mold cavity for solidification, and then releasing optical receptacle10.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, when optical receptacle10disclosed in PTL 1 is produced by injection molding, mold portions corresponding to guide holes18are not easily extracted from guide holes18, and thus optical receptacle10is undesirably deformed during releasing. Optical receptacle10having been deformed during releasing cannot return to the shape before releasing, and thus is unable to properly guide the light emitted from the optical fibers to the light receiving surface of the light receiving element in some cases. Thus, optical receptacle10disclosed in PTL 1 has a problem of being deformed when produced by injection molding.

An object of the present invention is to provide an optical receptacle which is not easily deformed even when produced by injection molding. Further, another object of the present invention is to provide an optical module having the optical receptacle.

Solution to Problem

An optical receptacle of the present invention is disposed between a plurality of light emitting elements or a plurality of light receiving elements and a plurality of optical transmission members, and is configured to optically couple the light emitting elements or the light receiving elements to end surfaces of the optical transmission members, respectively, the optical receptacle including: a plurality of first optical surfaces, each configured such that light emitted from a corresponding one of the light emitting elements is incident on the first optical surface or each configured to emit light propagating therein toward a corresponding one of the light receiving elements; a plurality of second optical surfaces, each configured to emit the light incident on the first optical surface toward an end surface of a corresponding one of the optical transmission members or each configured such that light from a corresponding one of the optical transmission members is incident on the second optical surface; a third optical surface configured to reflect the light incident on the first optical surface toward the second optical surface or configured to reflect the light incident on the second optical surface toward the first optical surface; a plurality of first recesses formed on a surface on which the plurality of second optical surfaces are disposed or a surface on which the plurality of first optical surfaces are disposed; and a plurality of second recesses formed on a surface opposite to a surface on which the first recesses are disposed, in which the plurality of first recesses and the plurality of second recesses are disposed opposite to each other such that central axes of the first recesses coincide, respectively, with central axes of the second recesses.

Further, an optical receptacle of the present invention is disposed between a plurality of light emitting elements or a plurality of light receiving elements and a plurality of optical transmission members, and is configured to optically couple the light emitting elements or the light receiving elements to end surfaces of the optical transmission members, respectively, the optical receptacle including: a plurality of first optical surfaces, each configured such that light emitted from a corresponding one of the light emitting elements is incident on the first optical surface or each configured to emit light propagating therein toward a corresponding one of the light receiving elements; a plurality of second optical surfaces, each configured to emit the light incident on the first optical surface toward an end surface of a corresponding one of the optical transmission members or each configured such that light from a corresponding one of the optical transmission members is incident on the second optical surface; a third optical surface configured to reflect the light incident on the first optical surface toward the second optical surface or configured to reflect the light incident on the second optical surface toward the first optical surface; and a plurality of recesses formed on a surface on which the plurality of second optical surfaces are disposed, in which each of the plurality of recesses includes a cylindrical recess body and a substantially truncated cone-shaped tapered part formed continuously to a bottom of the recess body.

An optical module of the present invention includes: a substrate on which a plurality of light emitting elements or a plurality of light receiving elements are disposed; and the optical receptacle of the present invention disposed on the substrate.

Advantageous Effects of Invention

According to the present invention, a plurality of light emitting elements or a plurality of light receiving elements can be optically coupled suitably to a plurality of optical transmission members even when an optical receptacle is produced by injection molding.

DESCRIPTION OF EMBODIMENTS

Configuration of Optical Module

FIG. 2is a cross-sectional view of optical module100according to Embodiment 1 of the present invention. InFIG. 2, hatching is omitted in the cross-section of optical receptacle120to show an optical path in optical receptacle120.

As illustrated inFIG. 2, optical module100includes substrate-mounted photoelectric conversion device110including light emitting elements114, and optical receptacle120. Optical module100is used with optical receptacle120connected to optical transmission members116. Optical transmission member116is not limited to any particular type and may be an optical fiber or a light waveguide, for example. In the present embodiment, optical transmission member116is an optical fiber. Further, the optical fiber may be a single-mode optical fiber or a multi-mode optical fiber.

Photoelectric conversion device110includes substrate112and a plurality of light emitting elements114. Light emitting elements114are disposed in line on substrate112, and configured to emit laser light in the direction perpendicular to the surface of substrate112. Light emitting element114is, e.g., Vertical Cavity Surface Emitting Laser (VCSEL).

Optical receptacle120optically couples light emitting elements114to the end surfaces of optical transmission members116, in the state of being disposed between photoelectric conversion device110and optical transmission members116. A configuration of optical receptacle120is described in detail below.

(Configuration of Optical Receptacle)

FIGS. 3A to 3Eillustrate a configuration of optical receptacle120according to Embodiment 1.FIGS. 3A to 3Eare a plan view, a bottom view, a front view, a rear view and a right side view of optical receptacle120, respectively.

As illustrated inFIGS. 3A to 3E, optical receptacle120is a substantially rectangular parallelepiped member. Optical receptacle120is light transmissive, and configured to emit light emitted from light emitting element114toward the end surface of optical transmission member116. Optical receptacle120includes a plurality of first optical surfaces (incidence surfaces)121, third optical surface (reflection surface)122, a plurality of second optical surfaces (emission surfaces)123, a plurality of first recesses124, and a plurality of second recesses125. Optical receptacle120is formed of a light-transmissive material with respect to light having a wavelength used for optical communications. Examples of the materials include transparent resins such as polyetherimide (PEI) and cyclic olefin resins. Optical receptacle120can be produced by injection molding, for example.

First optical surface121is an incidence surface that refracts laser light emitted from light emitting element114to allow the light to enter inside optical receptacle120. A plurality of first optical surfaces121are disposed in line in the lengthwise direction on the bottom surface of optical receptacle120so as to face respective light emitting elements114. The shape of first optical surface121is not particularly limited. In the present embodiment, the shape of first optical surface121is that of a convex lens surface protruding toward light emitting element114. The shape of first optical surface121in plan view is a circle. The central axis of first optical surface121is preferably perpendicular to the light emitting surface of light emitting element114(and to the surface of substrate112). Further, the central axis of first optical surface121preferably coincides with the optical axis of the laser light emitted from light emitting element114. The light incident on first optical surface121(incidence surface) propagates toward third optical surface122(reflection surface).

Third optical surface122is a reflection surface that reflects the light incident on first optical surface121toward second optical surface123. Third optical surface122is tilted such that the distance from optical transmission member116decreases in the direction from the bottom surface to the top surface of optical receptacle120. The inclination angle of third optical surface122relative to the optical axis of light emitted from light emitting element114is not particularly limited. In the present embodiment, the inclination angle of third optical surface122is 45° relative to the optical axis of light incident on first optical surface121. The shape of third optical surface122is not particularly limited. In the present embodiment, the shape of third optical surface122is a flat surface. The light incident on first optical surface121is incident on third optical surface122at an incident angle larger than the critical angle. Third optical surface122totally reflects the incident light toward second optical surface123. That is, light with a predetermined light flux diameter is incident on third optical surface122(reflection surface), and the light with the predetermined light flux diameter is emitted toward second optical surface123(emission surface).

Second optical surface123is an emission surface that emits the light totally reflected by third optical surface122toward the end surface of optical transmission member116. A plurality of second optical surfaces123are disposed in line in the lengthwise direction on a side surface of optical receptacle120so as to face respective end surfaces of optical transmission members116. The shape of second optical surface123is not particularly limited. In the present embodiment, the shape of second optical surface123is that of a convex lens surface protruding toward the end surface of optical transmission member116. This enables the light having the predetermined light flux diameter reflected by third optical surface122to be efficiently coupled to the end surface of optical transmission member116. The central axis of second optical surface123preferably coincides with the central axis of the end surface of optical transmission member116.

First recesses124are each a recess for fixing optical transmission members116to optical receptacle120(surface on which the plurality of second optical surfaces123are disposed). By fitting projections of an optical transmission member attachment respectively to first recesses124, optical transmission members116are fixed to the surface of optical receptacle120, on which the plurality of second optical surfaces123are disposed.

The shape and the number of first recesses124are not particularly limited as long as first recess124enables optical receptacle120to be fixed to substrate112. That is, any shape of first recess124is possible as long as first recess124has a shape complementary to the projection of the optical transmission member attachment. In the present embodiment, the shape of first recess124is a cylindrical shape. In addition, any number of first recesses124is possible as long as first recess124enables optical transmission member116to be fixed to optical receptacle120; typically a plurality of first recesses124are formed. In the present embodiment, two first recesses124are disposed on the surface on which the plurality of second optical surfaces123are disposed, such that all second optical surfaces123are interposed therebetween in the lengthwise direction. The plurality of first recesses124are formed at positions symmetrical with respect to a plane as a symmetry plane which is parallel to the optical axis of light passing through second optical surface123and halves third optical surface122in a vertical direction. Further, the diameter and the depth of the opening of first recess124are not particularly limited either as long as the opening of first recess124has a shape complementary to the projection of substrate112.

Second recesses125are each a recess for suppressing the deformation of optical receptacle120caused by first recess124during releasing in the case of producing optical receptacle120by injection molding. Second recess125opens to a side surface opposite to the surface on which first recesses124are disposed. The shape of second recess125is not particularly limited as long as stress that occurs in releasing first recess124can be offset. In the present embodiment, the shape of second recess125is a cylindrical shape. Further, the diameter and the depth of the opening of second recess125are not particularly limited either; the diameter and the depth thereof may be set depending on the stress that occurs in releasing first recess124.

The plurality of first recesses124and the plurality of second recesses125are disposed opposite to each other. The central axes of plurality of first recesses124and the central axes of the plurality of second recesses125respectively coincide with each other. When the central axes of first recesses124and second recesses125fail to coincide with each other, it is not possible to offset the stress that occurs in releasing first recesses124.

(Measurement of Distortion of Third Optical Surface)

The shape of third optical surface122after releasing when producing optical receptacle120according to Embodiment 1 by injection molding was measured using an interferometer or a three-dimensional measuring instrument. In addition, for comparison, also with regard to optical receptacle120′ which does not include second recesses125, the shape of third optical surface122after releasing was measured.

FIGS. 4A to 4Eillustrate a configuration of optical receptacle120′ according to a comparative example.FIGS. 4A, 4B, 4C, 4D, and 4Eare, respectively, a plan view, a bottom view, a front view, a rear view, and a right side view of optical receptacle120′ of the comparative example.FIGS. 5A, 5B, 6A, and 6Bare explanatory diagrams of distortion of third optical surfaces122of optical receptacles120and120′ produced by injection molding.FIG. 5Aillustrates force applied to optical receptacle120′ of the comparative example at the time of injection molding, andFIG. 5Bis a graph showing the shape of third optical surface122of the comparative example after injection molding.FIG. 6Aillustrates force applied to optical receptacle120according to Embodiment 1 at the time of injection molding, andFIG. 6Bis a graph showing the shape of third optical surface122according to Embodiment 1 after injection molding. InFIGS. 5B and 6B, the abscissa indicates distance d from the center of third optical surface122. The ordinate indicates deformation amount h of third optical surface122in the normal direction.

First, the case of producing conventional optical receptacle120′ by injection molding will be described. As illustrated inFIG. 5A, conventional optical receptacle120′ has recesses formed on a side surface, and thus requires at least a mold that molds a side surface on which recesses are formed in the injection molding. In the case where such a mold is used to perform injection molding followed by releasing, optical receptacle120′ is pulled toward the mold side (downward inFIG. 5) at the positions of the recesses by friction that occurs at inner surfaces of the recesses and mold portions corresponding to the recesses (see fine dotted lines inFIG. 5A). At that time, stress is applied to optical receptacle120′ such that optical receptacle120′ is curved as a whole (see fine solid lines inFIG. 5A). As a result, force is applied to cause third optical surface122to be curved as a whole, and thus third optical surface122is undesirably distorted (see thick solid lines inFIG. 5A).

On the other hand, as illustrated inFIG. 6A, optical receptacle120according to Embodiment 1 has first recesses124formed on one side surface and second recesses125formed on a side surface opposite to the one side surface, and thus requires a mold that molds both side surfaces opposite to each other in the injection molding. In the case where such a mold is used to perform injection molding followed by releasing, optical receptacle120is pulled in directions opposite to each other by friction that occurs at the inner surfaces of first recesses124and mold portions corresponding to first recesses124and by friction that occurs at the inner surfaces of second recesses125and mold portions corresponding to second recesses125. At that time, stress caused by friction that occurs at the inner surfaces of first recesses124and the mold portions corresponding to first recesses124is offset by stress caused by friction that occurs at the inner surfaces of second recesses125and the mold portions corresponding to second recesses125. Accordingly, no large force is applied to optical receptacle120. Therefore, as illustrated inFIG. 6B, in optical receptacle120, distortion in the height direction of third optical surface122was suppressed.

As described above, optical receptacle120according to Embodiment 1 includes first recesses124and second recesses125which are disposed opposite to each other such that the central axes thereof coincide with each other, and thus can suppress the occurrence of deformation (distortion) during releasing even when optical receptacle120is produced by injection molding.

An optical module according to Embodiment 2 differs from optical module100according to Embodiment 1 in the shape of optical receptacle220. Thus, the components same as those of optical module100according to Embodiment 1 are given the same symbols as those of optical module100according to Embodiment 1 and the description thereof is omitted, and different components of the optical module are mainly described. Optical receptacle220according to Embodiment 2 differs from optical receptacle120according to Embodiment 1 in that optical receptacle220has a plurality of recesses221instead of the plurality of first recesses124and the plurality of second recesses125.

(Configuration of Optical Receptacle]

FIGS. 7A to 7Eillustrate a configuration of optical receptacle220according to Embodiment 2 of the present invention.FIGS. 7A, 7B, 7C, 7D, and 7Eare, respectively, a plan view, a bottom view, a front view, a rear view, and a right side view of optical receptacle220according to Embodiment 2.

As illustrated inFIGS. 7A to 7E, optical receptacle220according to Embodiment 2 includes a plurality of first optical surfaces121, third optical surface122, a plurality of second optical surfaces123, and a plurality of recesses221.

Recesses221are each a portion for fixing optical transmission members116to optical receptacle220(surface on which the plurality of second optical surfaces123are disposed). The present embodiment is intended to suppress the deformation of the optical receptacle during releasing at the time of injection molding, by devising the shape of recess221. That is, recess221has functions of both first recess124and second recess125according to Embodiment 1. Recess221is formed on a side surface of optical receptacle220, on which the plurality of second optical surfaces123are disposed. Further, the number of recesses221is set in a manner corresponding to the number of projections of the optical transmission member attachment. In the present embodiment, two recesses221are disposed such that all second optical surfaces123are interposed therebetween. Recess221includes recess body222and tapered part223.

The shape of recess body222is not particularly limited as long as recess body222enables optical transmission members116to be positioned to a surface on which the plurality of second optical surfaces123are disposed. In the present embodiment, the shape of recess body222is a cylindrical shape. The length (depth) of recess body222in the axial direction is preferably 0.3 mm or more from the viewpoint of positioning the projection of the optical transmission member attachment. When the length of recess body222in the axial direction is less than 0.3 mm, there is a risk that optical transmission members116cannot be properly fixed to the surface on which the plurality of second optical surfaces123are disposed.

Tapered part223is a truncated cone-shaped portion for suppressing deformation of optical receptacle220by alleviating friction that occurs between recess221and a corresponding mold portion during releasing. The bottom surface of recess body222and the bottom surface of tapered part223have the same shape, and the inner peripheral surface of tapered part223(tapered surface) is continuous with the inner peripheral surface of recess body222. While the angle of the inner peripheral surface of tapered part223(tapered surface) relative to the central axis of recess221is not particularly limited, the angle thereof is about 3°, for example. It is preferable that the central axis of recess body222and the central axis of tapered part223coincide with each other.

(Measurement of Distortion of Third Optical Surface)

FIGS. 8A and 8Bare explanatory diagrams of distortion of third optical surface122of optical receptacle220produced by injection molding.FIG. 8Aillustrates stress applied to optical receptacle220of Embodiment 2 during releasing, andFIG. 8Bis a graph showing the shape of third optical surface122after releasing. In the graph ofFIG. 8B, the abscissa indicates distance d from the center of third optical surface122. The ordinate indicates deformation amount h of third optical surface122in the normal direction.

As illustrated inFIG. 8A, optical receptacle220according to Embodiment 2 has recesses221formed on a side surface, and thus requires a mold that molds a side surface side on which recesses221are formed, in the injection molding. In the case where such a mold is used to perform injection molding followed by releasing, optical receptacle220is pulled toward the mold side (downward inFIG. 8A) at the positions of recesses221by friction that occurs at the inner surfaces of recesses221and the mold portions corresponding to recesses221(see fine dotted lines inFIG. 8A). At that time, tapered part223is formed at the bottom of recess221, and thus friction is alleviated in optical receptacle220compared to optical receptacle120′ of the comparative example illustrated inFIGS. 5A and 5B. Therefore, as illustrated inFIG. 8B, in optical receptacle220, distortion of third optical surface122in the height direction was suppressed.

As described above, optical receptacle220according to Embodiment 2 can suppress the occurrence of deformation (distortion) during releasing even when optical receptacle220is produced by injection molding, since recesses221each include tapered part223formed at the bottom thereof.

Note that, while a case where first optical surfaces121and second optical surfaces123are a convex lens surface is shown in optical receptacles120and220according to the respective embodiments described above, first optical surfaces121and second optical surfaces123may be a flat surface. Specifically, only first optical surface121may be a flat surface, or only second optical surface123may be a flat surface. When first optical surface121is formed in a flat surface, third optical surface122is formed to function as a concave mirror, for example. When light immediately before reaching second optical surface123is effectively converged by first optical surface121, third optical surface122, or the like, second optical surface123may be formed in a flat surface.

Further, optical receptacles120and220according to the respective embodiments described above may also be used for a receiving optical module. In this case, the receiving optical module includes a plurality of light receiving elements for receiving light instead of the plurality of light emitting elements114. The plurality of light receiving elements are disposed on the same positions as the respective corresponding light emitting elements. The receiving optical module has second optical surfaces123as incidence surfaces, and first optical surfaces121as emission surfaces. Light emitted from the end surface of optical transmission member116enters the optical receptacle from second optical surface123. The light having entered the optical receptacle is reflected by third optical surface122to be emitted from first optical surface121toward the light receiving element. In the case of an optical module not having a reflection surface, light having entered the optical receptacle is emitted from first optical surface121toward the light receiving element.

This application is entitled to and claims the benefit of Japanese Patent Application No. 2013-267214, filed on Dec. 25, 2013, the disclosure of which including the specification, drawings and abstract is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The optical receptacle and optical module according to the present invention are advantageous for optical communications using optical transmission members.

REFERENCE SIGN LIST