JP2015172680A - optical module and optical coupling structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module and an optical coupling structure which can decrease a coupling loss between an optical waveguide and an optical fiber without increasing a coupling loss between a light-emitting element and the optical waveguide.SOLUTION: A transmission-side core 61b is formed in such a manner that broadening of light at a time when incident light P1 reaches an incident-side end face 61f of the transmission-side core 61b is smaller in a width direction intersecting the light incident direction than a width of the transmission-side core 61b, and that broadening of light in an optical axis direction at an end face 61h opposing to the incident-side end face 61f at a time when the incident light P1 reaches the end face 61h is smaller than a size Lin a height direction of the transmission-side core 61b. A cross-sectional shape of the transmission-side core 61b in a cross section perpendicular to the optical axis direction is an oblong that is short in the width direction.

Description

  The present invention relates to an optical module and an optical coupling structure.

  Patent Document 1 discloses an optical waveguide structure in which the cross-sectional area of the core of the receiving-side optical waveguide is larger than the cross-sectional area of the core of the transmitting-side optical waveguide. Accordingly, it is intended to reduce the coupling loss between the optical waveguide and the optical fiber and the coupling loss between the optical waveguide and the light receiving and emitting element.

JP 2010-20085 A

As a substrate used for an HPC server or the like, an optical circuit printed board on which an optical waveguide is mounted has been studied. The optical waveguide is connected to a light emitting element such as a VCSEL. In order to reduce the coupling loss between the light emitting element and the optical waveguide, it is required to increase the core diameter of the optical waveguide. On the other hand, the optical waveguide is also connected to the optical fiber. On the transmission side where light is emitted from the optical waveguide toward the optical fiber, in order to reduce the coupling loss between the optical waveguide and the optical fiber, the optical waveguide It is required to reduce the core diameter. Thus, since it is required to increase the core diameter of the optical waveguide on the one hand and to reduce the core diameter of the optical waveguide on the other hand, the coupling loss between the light emitting element and the optical waveguide is not increased. In addition, it is difficult to reduce the coupling loss between the optical waveguide and the optical fiber.
The present invention has been made in view of such problems, and an optical module capable of reducing the coupling loss between the optical waveguide and the optical fiber without increasing the coupling loss between the light emitting element and the optical waveguide. And an optical coupling structure.

  In order to solve the above-described problem, an optical module according to the present invention includes a light emitting element, a reflective surface including a transmission side core and a portion provided inside the transmission side core, and light from the light emitting element to the transmission side core. Light transmitted along the light incident direction intersecting the axial direction (hereinafter referred to as incident light) is reflected by the reflecting surface and guided in the optical axis direction, and emitted from the transmitting optical waveguide A transmission-side lens that collects light; a transmission-side optical fiber that receives light that has passed through the transmission-side lens; a reception-side optical fiber; and a reception-side lens that collects light emitted from the reception-side optical fiber; A reception-side optical waveguide having a reception-side core that guides light that has passed through the reception-side lens, and a light-receiving element that receives light emitted from the reception-side optical waveguide. The transmission-side core has the width of the transmission-side core in the width direction intersecting the light incidence direction when the incident light reaches the surface of the transmission-side core on which incident light is incident (hereinafter referred to as the incident-side end surface). The spread of light in the direction of the optical axis at the end surface when the incident light is assumed to have reached the end surface opposite to the end surface on the incident side is perpendicular to the width direction of the transmission-side core. It is formed to be smaller than the size in the height direction. The cross-sectional shape of the transmitting core in the cross section perpendicular to the optical axis direction is a rectangular shape that is short in the width direction.

  In addition, the optical coupling structure according to the present invention has a light-emitting element and a reflecting surface including a transmission-side core and a portion provided inside the transmission-side core, and light that intersects the optical axis direction of the transmission-side core from the light-emitting element A transmission-side optical waveguide that reflects light incident along the incident direction (hereinafter referred to as incident light) by a reflecting surface and guides the light in the optical axis direction. The transmission-side core has the width of the transmission-side core in the width direction intersecting the light incidence direction when the incident light reaches the surface of the transmission-side core on which incident light is incident (hereinafter referred to as the incident-side end surface). The spread of light in the direction of the optical axis at the end surface when the incident light is assumed to have reached the end surface opposite to the end surface on the incident side is perpendicular to the width direction of the transmission-side core. It is formed to be smaller than the size in the height direction. The cross-sectional shape of the transmitting core in the cross section perpendicular to the optical axis direction is a rectangular shape that is short in the width direction.

  According to the optical module and the optical coupling structure of the present invention, the coupling loss between the transmission side optical waveguide and the transmission side optical fiber is reduced without increasing the coupling loss between the light emitting element and the transmission side optical waveguide. be able to.

FIG. 1 is a front view of an optical module according to an embodiment of the present invention. FIG. 2 is a sectional side view taken along line II of the optical module transmitter shown in FIG. FIG. 3 is a side sectional view of the optical module receiver shown in FIG. 1 taken along line II-II. 4 is an enlarged cross-sectional view showing a part of FIG. FIG. 5 is an enlarged cross-sectional view showing a part of FIG. FIG. 6 is a cross-sectional view of the optical waveguide module shown in FIGS. 4 and 5 taken along line III-III. FIG. 7 is a top view of the optical waveguide module shown in FIG. 6 viewed from the positive direction of the Z axis. FIG. 8 is a diagram conceptually illustrating an example of the trajectory of light emitted from the VCSEL. FIG. 9 is a diagram conceptually illustrating an example of a locus of light emitted from the VCSEL. FIG. 10 is a diagram for explaining the first condition. FIG. 11 is a diagram for explaining the second condition. FIG. 12 is a conceptual diagram of an optical module transmission unit for explaining a condition different from the first and second conditions. FIG. 13 is a conceptual diagram of the optical module receiver.

[Description of Embodiment of Present Invention]
First, the contents of the embodiment of the present invention will be listed and described. (1) An optical module according to the present invention has a light emitting element and a reflecting surface including a transmitting side core and a portion provided inside the transmitting side core, and light that intersects the optical axis direction of the transmitting side core from the light emitting element. A transmission-side optical waveguide that reflects light incident along the incident direction (hereinafter referred to as incident light) by the reflecting surface and guides it in the optical axis direction, and a transmission that condenses the light emitted from the transmission-side optical waveguide A side lens, a transmission side optical fiber to which light passing through the transmission side lens is input, a reception side optical fiber, a reception side lens that collects light emitted from the reception side optical fiber, and a reception side lens A receiving-side optical waveguide having a receiving-side core that guides the received light, and a light-receiving element to which light emitted from the receiving-side optical waveguide is input. The transmission-side core has the width of the transmission-side core in the width direction intersecting the light incidence direction when the incident light reaches the surface of the transmission-side core on which incident light is incident (hereinafter referred to as the incident-side end surface). The spread of light in the direction of the optical axis at the end surface when the incident light is assumed to have reached the end surface opposite to the end surface on the incident side is perpendicular to the width direction of the transmission-side core. It is formed to be smaller than the size in the height direction. The cross-sectional shape of the transmitting core in the cross section perpendicular to the optical axis direction is a rectangular shape that is short in the width direction.

  In this optical module, in order to guide the incident light from the light emitting element to the transmission-side optical waveguide without omission, the reflection surface arranged in the transmission-side optical waveguide has a portion provided inside the transmission-side core. It is necessary for incident light to be contained. The present inventor recommends that the size of the transmitting core in the width direction and the size of the transmitting core in the height direction should be equal to or larger than a certain size for the incident light to be contained in the portion. I found it. That is, regarding the size in the width direction of the transmission side core, it is preferable that the light spread at the stage where the incident light reaches the incident side end face of the transmission side core is smaller than the width of the transmission side core. In addition, regarding the size in the height direction of the transmission side core, the spread of light in the optical axis direction on the end surface assuming that the incident light reaches the end surface facing the incident side end surface is the height of the transmission side core. It may be smaller than the size in the vertical direction.

  If the size of the transmitting core in the width direction and the height direction satisfy the above conditions, the coupling loss between the light emitting element and the transmitting optical waveguide increases even if the size of the transmitting core is reduced. do not do. On the other hand, if the size of the transmission side core is reduced, the coupling loss between the transmission side optical waveguide and the transmission side optical fiber can be reduced. When the size in the width direction and the height direction of the transmission side core is sufficiently reduced, the shape of the cross section perpendicular to the optical axis direction of the transmission side core is a rectangle that is short in the width direction.

  As described above, in the optical module having the reflection surface arranged in the transmission-side optical waveguide, the spread of light at the stage where the incident light reaches the incident-side end surface of the transmission-side core with respect to the size in the width direction of the transmission-side core. Is smaller than the size and the size of the transmitting core in the height direction is such that the incident light reaches the end surface opposite to the incident side end surface and the light in the optical axis direction at the end surface The cross-sectional shape and dimensions of the transmission-side optical waveguide may be set so that the spread becomes smaller than the size of the transmission-side core in the height direction. Thereby, the coupling loss between the transmission side optical waveguide and the transmission side optical fiber can be reduced without increasing the coupling loss between the light emitting element and the transmission side optical waveguide.

  (2) Further, in the above-described optical module, the reception-side core has a cross-sectional dimension in which an image of light projected from the reception-side optical fiber through the reception-side lens to the reception-side core is accommodated, and is perpendicular to the optical axis direction. The receiving-side core may have a substantially square cross-sectional shape, and the receiving-side lens may reduce the light emitted from the receiving-side optical fiber to a range smaller than the numerical aperture of the receiving-side optical waveguide. Thereby, the coupling loss between the receiving side optical fiber and the receiving side optical waveguide can be reduced.

  (3) In the above-described optical module, the transmission-side core has a cross-sectional dimension in which an image of light projected on the transmission-side optical fiber is accommodated in the core of the transmission-side optical fiber. The light emitted from the waveguide may be reduced to a range smaller than the numerical aperture of the transmission side optical fiber. Thereby, the coupling loss between the transmission side optical fiber and the transmission side optical waveguide can be further reduced.

(4) In the above-described optical module, the size in the width direction of the transmission side core is L _core-y, and the size in the height direction perpendicular to the width direction of the transmission side core is L _core-z. The distance between the light emitting surface of the element and the incident side end face of the transmitting core is L1, the size in the height direction of the transmitting core is L2, the emission angle of the light emitting element is NA _VCSEL, and the refractive index of the _clad is n _clad The refractive index of the transmitting core is n _core , the emission diameter of the light emitting element is φ _VCSEL , the mounting error in the width direction of the light emitting element is ΔY _VCSEL, and the mounting error of the light emitting element in the optical axis direction of the transmitting core is When ΔX _VCSEL , the following two expressions may be satisfied. Thereby, the above-described optical module can be suitably realized.

  (5) In order to solve the above-described problem, an optical coupling structure according to the present invention includes a light emitting element, a reflective surface including a transmission side core and a portion provided inside the transmission side core, and transmits from the light emitting element. A transmission-side optical waveguide that reflects light incident along a light incident direction that intersects the optical axis direction of the side core (hereinafter referred to as incident light) by a reflecting surface and guides the light in the optical axis direction. The transmission-side core has the width of the transmission-side core in the width direction intersecting the light incidence direction when the incident light reaches the surface of the transmission-side core on which incident light is incident (hereinafter referred to as the incident-side end surface). The spread of light in the direction of the optical axis at the end surface when the incident light is assumed to have reached the end surface opposite to the end surface on the incident side is perpendicular to the width direction of the transmission-side core. It is formed to be smaller than the size in the height direction. The cross-sectional shape of the transmitting core in the cross section perpendicular to the optical axis direction is a rectangular shape that is short in the width direction.

  (6) The above-described optical coupling structure further includes a transmission-side lens that collects light emitted from the transmission-side optical waveguide, and a transmission-side optical fiber into which the light that has passed through the transmission-side lens is input. May be. The transmission-side core has a cross-sectional dimension in which an image of light projected on the transmission-side optical fiber is accommodated in the core of the transmission-side optical fiber, and the transmission-side lens transmits light emitted from the transmission-side optical waveguide to the transmission side. You may reduce to the range smaller than the numerical aperture of an optical fiber.

[Details of the embodiment of the present invention]
Specific examples of the optical module and the optical coupling structure according to the embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to the claim are included. In the following description, the same reference numerals are given to the same elements in the description of the drawings, and redundant descriptions are omitted.

  FIG. 1 is a front view of an optical module 10 according to an embodiment of the present invention, and shows a state in which the optical module 10 is disassembled. The optical module 10 includes an optical module transmitter 11 and an optical module receiver 12. FIG. 2 is a side sectional view taken along line II of the optical module transmitter 11 shown in FIG. FIG. 3 is a sectional side view of the optical module receiver 12 shown in FIG. 1 taken along the line II-II. In FIG. 1 to FIG. 3, an XYZ orthogonal coordinate system is also shown for easy understanding. 4 to 7, FIG. 10, and FIG. 11, the XYZ orthogonal coordinate system is shown, but the coordinate system in each figure is the same.

  As shown in FIG. 1, the optical module 10 includes an optical waveguide module 20, a jack connector 30, a plug connector 40, a transmission side optical fiber 51, and a reception side optical fiber 52. The optical waveguide module 20 includes a waveguide module transmission unit 21 and a waveguide module reception unit 22. The waveguide module transmission unit 21 includes a transmission-side optical waveguide 61, a VCSEL 71, and a transmission-side IC 81 as shown in FIG. 2 described later, but these are not shown in FIG. Further, as shown in FIG. 3 to be described later, the waveguide module receiver 22 includes a reception-side optical waveguide 62, a PD 72, and a reception-side IC 82, but these are not shown in FIG.

  As illustrated in FIG. 2, the waveguide module transmission unit 21 includes a waveguide substrate 91, a VCSEL 71 and a transmission-side IC 81 provided on the waveguide substrate 91. A transmission-side optical waveguide 61 is formed on the waveguide substrate 91, and a transmission-side waveguide mirror 61 a (one form of reflection surface) is disposed inside the transmission-side optical waveguide 61. The VCSEL 71 is a light emitting element in the present embodiment, and is arranged side by side in the Z-axis direction (the thickness direction of the waveguide substrate 91) with respect to the transmission side optical waveguide 61. In one example, the VCSEL 71 is disposed side by side in the Z-axis direction with respect to the transmission-side waveguide mirror 61 a and is disposed immediately above the transmission-side optical waveguide 61. The VCSEL 71 emits light P1 toward the transmission-side waveguide mirror 61a. Other optical components such as a lens are not provided between the VCSEL 71 and the transmission-side waveguide mirror 61a, and these are optically coupled directly. The transmission side IC 81 is, for example, a laser diode driver (LDD).

  The transmission-side optical fiber 51 is held by the plug connector 40 and is arranged side by side in the Z-axis direction with respect to the waveguide module transmission unit 21 with the jack connector 30 interposed therebetween. Inside the jack connector 30, a transmission side lens 101 for condensing the light P1 emitted from the transmission side optical waveguide 61 is disposed. The core 51 a of the transmission side optical fiber 51 is optically coupled to the transmission side optical waveguide 61 through the transmission side lens 101, and inputs the light P 1 that has passed through the transmission side lens 101. The transmission side optical waveguide 61 is further provided with a mirror 61 d for guiding the guided light P <b> 1 to the transmission side optical fiber 51.

  As shown in FIG. 3, the waveguide module reception unit 22 includes a waveguide substrate 91 that is common to the waveguide module transmission unit 21, a photodiode (PD) 72 and a reception-side IC 82 provided on the waveguide substrate 91. Have A reception-side optical waveguide 62 is formed on the waveguide substrate 91, and a reception-side waveguide mirror 62 a is disposed inside the reception-side optical waveguide 62. The PD 72 is a light receiving element in the present embodiment, and is arranged side by side in the Z-axis direction (the thickness direction of the waveguide substrate 91) with respect to the reception-side optical waveguide 62. In one example, the PD 72 is disposed side by side in the Z-axis direction with respect to the reception-side waveguide mirror 62 a and is disposed immediately above the reception-side optical waveguide 62. The PD 72 receives the light P2 guided through the reception-side waveguide mirror 62a. The receiving side IC 82 is, for example, a transimpedance amplifier (TIA).

  The reception-side optical fiber 52 is held by the plug connector 40 and is arranged side by side in the Z-axis direction with respect to the waveguide module reception unit 22 with the jack connector 30 interposed therebetween. Inside the jack connector 30, a receiving side lens 102 for collecting the light P <b> 2 emitted from the receiving side optical fiber 52 is disposed. The core 52 a of the reception side optical fiber 52 is optically coupled to the reception side optical waveguide 62 through the reception side lens 102. The receiving side optical waveguide 62 is further provided with a mirror 62 d for guiding the light P <b> 2 from the receiving side optical fiber 52 to the receiving side optical waveguide 62.

Here, FIG. 4 is an enlarged sectional view showing a part of FIG. FIG. 5 is an enlarged cross-sectional view showing a part of FIG. FIG. 6 is a cross-sectional view taken along the line III-III of the optical waveguide module 20 shown in FIGS. FIG. 7 is a top view of the optical waveguide module 20 shown in FIG. 6 viewed from the positive direction of the Z axis.
As shown in FIGS. 4, 6, and 7, a plurality of transmission side optical waveguides 61 and a plurality of reception side optical waveguides 62 are provided, respectively (four cases are illustrated in the figure). The transmission-side optical waveguide 61 includes a transmission-side core 61b that guides light, and a transmission-side cladding 61c that has a lower refractive index than the transmission-side core 61b and covers the transmission-side core 61b. The transmission side core 61b and the transmission side clad 61c are made of, for example, a resin (polymer). The shape of the cross section perpendicular to the optical axis direction of the transmission-side core 61b is a rectangular shape with the Z-axis direction as the long direction and the Y-axis direction as the short direction. The transmission-side clad 61 c is common to the plurality of transmission-side optical waveguides 61. The transmission side core 61 b and the transmission side clad 61 c are arranged on the substrate 93.

  A transmission-side waveguide mirror 61 a is disposed inside the transmission-side optical waveguide 61. The transmission-side waveguide mirror 61a is constituted by, for example, a boundary surface between the medium constituting the transmission-side optical waveguide 61 and air, and the angle formed with the optical waveguide direction (X-axis direction) is, for example, 45 degrees. It is arranged inclining in the Z-axis direction with respect to the X-axis direction. The transmission-side waveguide mirror 61a includes a portion 61e provided inside the transmission-side core 61b. Light P1 (see FIG. 2) incident from the VCSEL 71 along the light incident direction (for example, the Z-axis direction) intersecting the optical axis direction (X-axis direction) of the transmission-side core 61b is transmitted from the transmission-side waveguide mirror 61a. The light is reflected at the portion 61e and guided inside the transmitting core 61b along the optical axis direction.

  8 and 9 are diagrams conceptually showing an example of the trajectory of the light P1 emitted from the VCSEL 71. FIG. FIG. 8 is a view as seen from the Y axis negative direction side. FIG. 9 is a view as seen from the Z axis positive direction side. As shown in these figures, the light P1 emitted from the VCSEL 71 reaches the portion 61e of the transmission-side waveguide mirror 61a while spreading in a conical shape, and after being reflected by the portion 61e, is further spread and then the inside of the transmission-side core 61b. Is guided.

  As shown in FIGS. 5, 6, and 7, the reception-side optical waveguide 62 includes a reception-side core 62 b that guides light, and a reception that has a lower refractive index than the reception-side core 62 b and covers the reception-side core 62 b. Side cladding 62c. The shape of the cross section perpendicular to the optical axis direction of the receiving core 62b is a substantially square shape. The reception-side cladding 62c is common to the plurality of reception-side optical waveguides 62, and is provided as a common layer with the transmission-side cladding 61c. The reception side core 62 b and the reception side cladding 62 c are disposed on the substrate 93.

  A reception-side waveguide mirror 62 a is disposed inside the reception-side optical waveguide 62. The reception-side waveguide mirror 62a is constituted by, for example, a boundary surface between the medium constituting the reception-side optical waveguide 62 and air, and the angle formed with the optical waveguide direction (X-axis direction) is, for example, 45 degrees. It is arranged inclining in the Z-axis direction with respect to the X-axis direction. Light P2 (see FIG. 2) guided along the optical axis direction of the reception-side core 62b is reflected by the reception-side waveguide mirror 62a and enters the PD 72.

  Here, the size and shape of the transmission side core 61b of the present embodiment will be described. The transmission side core 61b is formed so as to satisfy the following two conditions.

FIG. 10 is a diagram for explaining the first condition. As shown in the figure, the transmission-side core 61b is configured such that the light P1 incident from the VCSEL 71 is in the positive Z-axis direction of the transmission-side core 61b in the width direction (Y-axis direction) intersecting the light incident direction (Z-axis direction). The light spread D1 at the stage of reaching the side end face (that is, the face facing the VCSEL 71; hereinafter referred to as the incident end face) 61f is smaller than the width L _{core-y of} the transmitting core 61b in this direction. Has been. In this case, even if the light P1 incident on the transmission-side core 61b from the VCSEL 71 hits the side surface 61g of the transmission-side core 61b before reaching the transmission-side waveguide mirror 61a, the light P1 is reflected on the side surface, 61a can be reached.

FIG. 11 is a diagram for explaining the second condition. As shown in the figure, under the second condition, it is assumed that the transmission-side core 61b extends also on the back surface side of the transmission-side waveguide mirror 61a, and the incident-side end surface of the transmission-side core 61b is connected to the back surface side. Assume that there is an opposing end face 61h. Furthermore, it is assumed that the incident light P1 passes through the transmission-side waveguide mirror 61a and reaches the end face 61h. At this time, the transmission-side core 61b has a height direction (Z-axis) where the spread D2 of the incident light P1 in the optical axis direction of the transmission-side core 61b on the end surface 61h is perpendicular to the width direction (Y-axis direction) of the transmission-side core 61b. (Direction) is smaller than L _core-z . In this case, all the light P1 incident on the transmission side core 61b from the VCSEL 71 reaches the transmission side waveguide mirror 61a and can be reflected.

When the transmission-side core 61b satisfies the first and second conditions described above, for example, when the cross section perpendicular to the optical axis of the light P1 incident on the transmission-side core 61b from the VCSEL 71 is circular, the width of the transmission-side core 61b The minimum value allowed for L _core-y is smaller than the minimum value allowed for the height L _core-z of the transmitting core 61b. Therefore, when considering reducing the cross-sectional area of the transmission-side core 61b, the shape of the cross-section perpendicular to the optical axis direction of the transmission-side core 61b is such that the Z-axis direction is the longitudinal direction and the Y-axis direction is the short-side direction. It becomes a rectangular shape.

The above first and second conditions are specifically formulated. Regarding the first condition, it is only necessary that the light P1 enters the transmission side core 61b. Therefore, the condition regarding the width L _core-y of the transmission side core 61b in the Y-axis direction is expressed by the following equation (1).

Regarding the second condition, the spread D2 of the incident light P1 in the optical axis direction of the transmission-side core 61b on the end surface 61h is larger than the size L _{core-z in} the height direction (Z-axis direction) of the transmission-side core 61b. Should be small. Such a condition is represented by the following formula (2).

However, each parameter in the above formulas (1) and (2) is as follows. It is assumed that the NA of the transmission side optical waveguide 61 is larger than NA _VCSEL .
L1: Distance between the VCSEL 71 and the transmission side core 61b (in this embodiment, equal to the height direction (Z-axis direction) size of the transmission side cladding 61c)
L2: Size of the transmitting core in the height direction (Z-axis direction)
NA _VCSEL : Angle of emission of light P1 from _VCSEL 71
n _clad : Refractive index of the transmission side cladding 61c
n _core : Refractive index φ _VCSEL : _VCSEL 71 emission diameter ΔY _VCSEL : _VCSEL 71 mounting error in the Y-axis direction ΔX _VCSEL : _VCSEL 71 mounting error in the X-axis direction Also, the above equations (3) and (4) Since the inside of the tangent (tan) in FIG. 2 is a dimensionless quantity, the following mathematical formulas (5) and (6) are obtained when converted into angular quantities (unit: radians).

  FIG. 12 is a conceptual diagram of the optical module transmission unit 11 for explaining a condition different from the first and second conditions. In FIG. 12, the VCSEL 71, the transmission-side optical waveguide 61, the transmission-side lens 101, and the transmission-side optical fiber 51 are shown in a straight line for easy understanding. As shown in the figure, the image of the light P 1 emitted from the transmission side optical waveguide 61 is projected onto the core 51 a of the transmission side optical fiber 51. The size of the transmission-side core 61b is set so that the image (width W3) of the light P1 at that time can be accommodated in the core 51a (diameter D3). Note that the transmission side lens 101 may reduce the light P1 emitted from the transmission side optical waveguide 61 within a range smaller than the numerical aperture of the transmission side optical fiber 51.

  Next, the receiving core 62b will be described. FIG. 13 is a conceptual diagram of the optical module receiver 12. In FIG. 13, for easy understanding, the reception side optical fiber 52, the reception side lens 102, the reception side optical waveguide 62, and the PD 72 are shown in a straight line. As shown in the figure, the image of the light P <b> 2 emitted from the reception side optical fiber 52 is projected onto the reception side core 62 b of the reception side optical waveguide 62 through the reception side lens 102. The size of the receiving side core 62b is set so that the image (width W4) of the light P2 at that time can be accommodated in the receiving side core 62b (diameter D4). When this condition is satisfied by the receiving core 62b, when the cross section perpendicular to the optical axis of the light P2 incident on the receiving core 62b from the receiving optical fiber 52 is circular, the width of the receiving core 62b is allowed. And the minimum value allowed for the height in the Z-axis direction of the receiving core 62b are equal to each other. Accordingly, when considering reducing the cross-sectional area of the reception-side core 62b, the cross-sectional shape perpendicular to the optical axis direction of the reception-side core 62b is a substantially square shape. The reception side lens 102 may reduce the light P2 emitted from the reception side optical fiber 52 within a range smaller than the numerical aperture of the reception side optical waveguide 62.

  The effect which the optical coupling structure of the optical module 10 provided with the above structure show | plays is demonstrated. First, the transmission side will be described. The light P1 emitted from the VCSEL 71 enters the transmission-side optical waveguide 61, is reflected by the transmission-side waveguide mirror 61a, and is guided through the transmission-side core 61b of the transmission-side optical waveguide 61. The The guided light P <b> 2 exits from the transmission side optical waveguide 61, passes through the transmission side lens 101, and is input to the transmission side optical fiber 51. At this time, coupling loss may occur between the VCSEL 71 and the transmission side optical waveguide 61 and between the transmission side optical waveguide 61 and the transmission side optical fiber 51.

  Looking at the coupling loss between the VCSEL 71 and the transmission-side optical waveguide 61, the coupling loss generally increases as the size (cross-sectional dimension) of the transmission-side core 61b decreases. However, in the range where the size of the transmission-side core 61b satisfies the above first and second conditions, the incident light P1 reaches the transmission-side waveguide mirror 61a without leakage and is reflected and reflected inside the transmission-side core 61b. Waveguided. Therefore, even if the size of the transmission-side core 61b is reduced within a range that satisfies the first and second conditions, the coupling loss between the VCSEL 71 and the transmission-side optical waveguide 61 does not increase. On the other hand, regarding the coupling loss between the transmission-side optical waveguide 61 and the transmission-side optical fiber 51, the coupling loss is reduced as the size of the transmission-side core 61b is smaller. Therefore, by reducing the size of the transmission-side core 61b within a range that satisfies the first and second conditions, the coupling loss can be reduced as the entire optical module transmission unit 11. That is, the coupling loss between the transmission side optical waveguide 61 and the transmission side optical fiber 51 can be reduced without increasing the coupling loss between the VCSEL 71 and the transmission side optical waveguide 61.

  Further, as in the present embodiment, the size of the transmission-side core 61b may satisfy the above-described mathematical expressions (1) and (2). Thereby, the optical module 10 having the above-described effects can be suitably realized.

  Further, as in the present embodiment, the transmission-side core 61b may have a cross-sectional dimension in which the image of the light P1 projected on the transmission-side optical fiber 51 can be accommodated in the core 51a of the transmission-side optical fiber 51. The transmission side lens 101 may reduce the light P <b> 1 emitted from the transmission side optical waveguide 61 to a range smaller than the numerical aperture of the transmission side optical fiber 51. Thereby, the coupling loss between the transmission side optical fiber 51 and the transmission side optical waveguide 61 can be further reduced.

  Next, the receiving side will be described. The light P2 emitted from the reception-side optical fiber 52 passes through the reception-side lens 102 and is input to the reception-side optical waveguide 62. Then, the light P2 is reflected by the mirror 62d and guided through the reception-side core 62b. The guided light P2 is reflected by the reception-side waveguide mirror 62a and input to the PD 72. At this time, coupling loss may occur between the reception side optical fiber 52 and the reception side optical waveguide 62 and between the reception side optical waveguide 62 and the PD 72.

  Therefore, as in the present embodiment, the receiving core 62b has a cross-section in which the image of the light P2 projected from the receiving optical fiber 52 to the receiving core 62b via the receiving lens 102 is accommodated in the receiving core 62b. Further, the receiving side lens 102 may reduce the light P2 emitted from the receiving side optical fiber 52 within a range smaller than the numerical aperture of the receiving side optical waveguide 62. Thereby, the coupling loss between the receiving side optical waveguide 62 and the receiving side optical fiber 52 can be reduced.

  The optical module and the optical coupling structure according to the present invention are not limited to the above-described embodiments, and various other modifications are possible. For example, in the above-described embodiment, the transmission side optical fiber 51 is arranged in the direction (Z axis direction) intersecting the optical axis direction of the transmission side optical waveguide 61 with respect to the transmission side optical waveguide 61, and the mirror 61d is The transmission side optical fiber 51 and the transmission side optical waveguide 61 are optically coupled to each other. Similarly, the reception-side optical fiber 52 is disposed in a direction (Z-axis direction) intersecting the optical axis direction of the reception-side optical waveguide 62 with respect to the reception-side optical waveguide 62, and receives the reception-side light via the mirror 62d. The fiber 52 and the receiving side optical waveguide 62 are optically coupled. The present invention is not limited to these configurations. For example, the transmission-side optical fiber 51 is arranged side by side in the optical axis direction (X-axis direction) of the transmission-side optical waveguide 61 with respect to the transmission-side optical waveguide 61. These optical axis directions and the optical axis direction of the transmission-side optical waveguide 61 may coincide with each other. Similarly, the reception-side optical fiber 52 is arranged side by side in the optical axis direction (X-axis direction) of the reception-side optical waveguide 62 with respect to the reception-side optical waveguide 62. The optical axis direction of the waveguide 62 may coincide with each other.

  In the above-described embodiment, the VCSEL is exemplified as the light emitting element and the PD is exemplified as the light receiving element. However, the light emitting element and the light receiving element are not limited to these.

  DESCRIPTION OF SYMBOLS 10 ... Optical module, 11 ... Optical module transmission part, 12 ... Optical module reception part, 20 ... Optical waveguide module, 21 ... Waveguide module transmission part, 22 ... Waveguide module reception part, 30 ... Jack connector, 40 ... Plug connector 51 ... transmission side optical fiber, 51a ... core, 52 ... reception side optical fiber, 52a ... core, 61 ... transmission side optical waveguide, 61a ... transmission side waveguide mirror, 61b ... transmission side core, 61c ... transmission side cladding, 61d ... mirror, 62 ... reception side optical waveguide, 62a ... reception side waveguide mirror, 62b ... reception side core, 62c ... reception side cladding, 62d ... mirror, 91 ... waveguide substrate, 93 ... substrate, 101 ... transmission side lens , 102... Reception side lens, P1... Incident light.

Claims (6)

A light emitting element;
Light having a reflection surface including a transmission side core and a portion provided inside the transmission side core, and incident from the light emitting element along a light incident direction intersecting with an optical axis direction of the transmission side core (hereinafter referred to as a light incident direction) , Referred to as incident light) is reflected by the reflecting surface and guided in the optical axis direction;
A transmission side lens for condensing the light emitted from the transmission side optical waveguide;
A transmission-side optical fiber to which light that has passed through the transmission-side lens is input;
A receiving optical fiber;
A receiving lens that collects light emitted from the receiving optical fiber;
A receiving-side optical waveguide having a receiving-side core that guides light that has passed through the receiving-side lens;
A light receiving element to which light emitted from the receiving side optical waveguide is input;
With
In the width direction in which the spread of light at the stage when the incident light reaches the surface of the transmitting core on which the incident light is incident (hereinafter referred to as an incident-side end surface) intersects the light incident direction. It is formed so as to be smaller than the width of the transmission side core, and the spread of light in the optical axis direction at the end surface when it is assumed that the incident light has reached the end surface facing the incident side end surface, It is formed to be smaller than the size in the height direction perpendicular to the width direction of the transmission side core,
The optical module, wherein a cross-sectional shape of the transmitting core in a cross section perpendicular to the optical axis direction is a rectangular shape short in the width direction. The receiving-side core has a cross-sectional dimension in which an image of light projected onto the core of the receiving-side optical waveguide from the receiving-side optical fiber via the receiving-side lens is accommodated, and in a cross section perpendicular to the optical axis direction The receiving core has a substantially square cross-sectional shape,
The optical module according to claim 1, wherein the reception side lens reduces light emitted from the reception side optical fiber to a range smaller than a numerical aperture of the reception side optical waveguide. The transmitting-side core has a cross-sectional dimension in which an image of light projected on the transmitting-side optical fiber is accommodated in the core of the transmitting-side optical fiber;
The optical module according to claim 1, wherein the transmission side lens reduces the light emitted from the transmission side optical waveguide to a range smaller than a numerical aperture of the transmission side optical fiber. The size in the width direction of the transmission side core is L _core-y , the size in the height direction perpendicular to the width direction of the transmission side core is L _core-z, and the light emitting surface of the light emitting element and the light emitting surface The distance from the incident side end face of the transmission side core is L1, the size in the height direction of the transmission side core is L2, the emission angle of the light emitting element is NA _VCSEL, and the refractive index of the cladding is n _clad. The refractive index of the transmitting core is n _core , the emission diameter of the light emitting element is φ _VCSEL , the mounting error of the light emitting element in the width direction is ΔY _VCSEL, and the light emission in the optical axis direction of the transmitting core The optical module according to any one of claims 1 to 3, which satisfies the following two expressions when an element mounting error is ΔX _VCSEL .

A light emitting element;
Light having a reflection surface including a transmission side core and a portion provided inside the transmission side core, and incident from the light emitting element along a light incident direction intersecting with an optical axis direction of the transmission side core (hereinafter referred to as a light incident direction) , Referred to as incident light) is reflected by the reflecting surface and guided in the optical axis direction;
With
In the width direction in which the spread of light at the stage when the incident light reaches the surface of the transmitting core on which the incident light is incident (hereinafter referred to as an incident-side end surface) intersects the light incident direction. It is formed so as to be smaller than the width of the transmission side core, and the spread of light in the optical axis direction at the end surface when it is assumed that the incident light has reached the end surface facing the incident side end surface, It is formed to be smaller than the size in the height direction perpendicular to the width direction of the transmission side core,
The optical coupling structure, wherein a cross-sectional shape of the transmitting core in a cross section perpendicular to the optical axis direction is a rectangular shape short in the width direction. A transmission side lens for condensing the light emitted from the transmission side optical waveguide;
A transmission-side optical fiber to which light that has passed through the transmission-side lens is input;
Further comprising
The transmitting-side core has a cross-sectional dimension in which an image of light projected on the transmitting-side optical fiber is accommodated in the core of the transmitting-side optical fiber;
6. The optical coupling structure according to claim 5, wherein the transmission side lens reduces light emitted from the transmission side optical waveguide to a range smaller than a numerical aperture of the transmission side optical fiber.

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