JP6390291B2 - Optical connector - Google Patents

Description

  The present invention relates to an optical connector.

  Patent Documents 1 and 2 describe techniques related to optical connectors for optically coupling optical fibers and optical elements. In these optical connectors, a recess is formed in the ferrule that holds the optical fiber, the end face of the optical fiber is exposed at one of a pair of side surfaces facing each other in the recess, and a lens is formed on the other side. . The light emitted from the end face of the optical fiber reaches the lens through the recess and is collimated by the lens. This light is emitted from the end surface of the ferrule located on the back side with respect to the other side surface of the recess.

US Patent Application Publication No. 2011/0229077 US Patent Application Publication No. 2012/0177327

  As an optical connector for connecting an optical fiber to another optical fiber or an optical element, there is one in which a lens is formed on the inner side of a ferrule, such as the optical connector described in Patent Documents 1 and 2. However, as in Patent Documents 1 and 2, when a concave portion is formed in a ferrule and a lens is formed on the inner surface thereof, a space is formed between the optical fiber and the lens. Therefore, an interface having a large refractive index difference occurs at the boundary between the optical fiber and the space and at the boundary between the space and the lens. If a part of the light is reflected at these interfaces, the connection loss increases (reflection attenuation). Note that the required coupling efficiency is higher when the optical fibers are connected to each other than when the optical fibers and the optical elements are connected. Therefore, such a problem becomes more conspicuous when connecting optical fibers.

  An object of this invention is to provide the optical connector which can suppress the increase in a connection loss.

  An optical connector according to the present invention is optically coupled to an optical waveguide member and the optical waveguide member, and is incident on the optical waveguide member from the connected optical connector, or emitted from the optical waveguide member to the connected optical connector. And a lens disposed on an optical path between the optical waveguide member and the connection end, a first optical path between the optical waveguide member and the lens, and a lens and the connection end. The second optical path between them is occupied by a medium having a refractive index larger than that of air, and the medium on the first optical path side and the medium on the second optical path side have a refractive index difference from each other with the lens as a boundary. Have.

  ADVANTAGE OF THE INVENTION According to this invention, the optical connector which can suppress the increase in connection loss can be provided.

FIG. 1 is a perspective view showing an optical connector according to the first embodiment of the present invention. FIG. 2 is a side sectional view showing a II-II section shown in FIG. FIG. 3 is a partial perspective sectional view of the optical connector. FIG. 4 is an enlarged cross-sectional view showing the optical path connecting the tip surface and the flat surface of the optical fiber. FIG. 5 is a perspective view of the ferrule as viewed obliquely from the front. FIG. 6 is a perspective view of the lens array as viewed obliquely from the rear. FIG. 7 is a cross-sectional view schematically showing how a pair of optical connectors are connected to face each other. FIG. 8 is a diagram for explaining a resin material suitable as a medium on the first optical path side, that is, when the lens array is made of PEI, as a medium on the second optical path side. FIG. 9 is a diagram illustrating temperature characteristics of the optical connector. FIG. 10 is a diagram illustrating temperature characteristics of the optical connector. FIG. 11 is a side sectional view showing an optical connector according to the second embodiment of the present invention. FIG. 12 is an enlarged cross-sectional view showing the optical path connecting the tip surface and the surface of the optical fiber. FIG. 13 is an enlarged cross-sectional view of an optical connector according to a modification of the second embodiment.

[Description of Embodiment of Present Invention]
First, the contents of the embodiments of the present invention will be listed and described.

  An optical connector according to the present invention is optically coupled to an optical waveguide member, and passes light incident on the optical waveguide member from the connection-destination optical connector or light emitted from the optical waveguide member to the connection-destination optical connector. And a lens disposed on an optical path between the optical waveguide member and the connection end, a first optical path between the lens and the connection end, and a second between the optical waveguide member and the lens. The optical path is occupied by a medium having a refractive index larger than that of air, and the medium on the first optical path side and the medium on the second optical path side have a refractive index difference from each other with the lens as a boundary.

  In this optical connector, there is no space between the optical paths from the optical waveguide member through the lens to the connection end, and the optical path is occupied by a medium having a refractive index larger than that of air. Therefore, the refractive index difference existing in the optical path can be made smaller than the refractive index difference at the interface with air, and the reflection attenuation can be reduced. Thereby, the increase in connection loss can be suppressed effectively.

  The refractive index of the medium on the second optical path side may be smaller than the refractive index of the medium on the first optical path side. Thereby, for example, the lens can be suitably formed on the inner surface formed on the back side of the connection end. In this case, a material suitable for the ferrule may be selected as the medium on the second optical path side, and a material having a desired refractive index difference with respect to the medium on the second optical path side may be selected as the medium on the first optical path side. For example, the refractive index of the medium on the first optical path side may be included in the range of 1.5 to 1.6, and the refractive index of the medium on the second optical path side may be included in the range of 1.3 to 1.5. .

  Also, the absolute value of the optical loss when connected to another optical connector having the same configuration as the optical connector within ± 60 ° C. from the temperature at which the optical loss between the optical waveguide member and the connection end is minimized. May be 1 dB or less. Thereby, in the temperature range assumed at the time of use of an optical connector, the coupling efficiency of optical fibers can fully be obtained.

  In addition, the optical loss due to temperature change when connected to another optical connector having the same configuration as the optical connector within ± 60 ° C. from the temperature at which the optical loss between the optical waveguide member and the connection end is minimized. The fluctuation may be within ± 0.4 dB. Thereby, the fluctuation | variation of the coupling efficiency of optical fibers can fully be suppressed in the range of the temperature change assumed at the time of use of an optical connector. Preferably, the variation is within ± 0.3 dB, and more preferably, the variation is within ± 0.2 dB.

Further, the variation due to the temperature change of the difference between the refractive index of the medium on the first optical path side and the refractive index of the medium on the second optical path side may be 15.0 × 10 ⁻⁵ / ° C. or less. For example, by using a medium having such characteristics on the first optical path side and the second optical path side, the variation in optical loss can be made within ± 0.4 dB.

Further, the fluctuation due to the temperature change of the difference between the refractive index of the medium on the first optical path side and the refractive index of the medium on the second optical path side may be 10.0 × 10 ⁻⁵ / ° C. or less. For example, by using a medium having such characteristics on the first optical path side and the second optical path side, the fluctuation of the optical loss can be made within ± 0.3 dB.

Further, the fluctuation due to the temperature change of the difference between the refractive index of the medium on the first optical path side and the refractive index of the medium on the second optical path side may be 5.0 × 10 ⁻⁵ / ° C. or less. For example, by using a medium having such characteristics on the first optical path side and the second optical path side, the variation in optical loss can be made within ± 0.2 dB.

  Further, the lens, the connection end, and the medium occupying the first optical path are integrally formed, and the optical waveguide member and the lens may be opposed to each other via the medium occupying the second optical path. Thereby, the form which a connection end exposes in the edge part of an optical connector is suitably realizable. In this case, since the lens is not exposed at the end of the optical connector, it is possible to provide an optical connector in which the end face can be easily cleaned.

[Details of the embodiment of the present invention]
Hereinafter, an aspect of the optical connector of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is a perspective view showing an optical connector 1 according to the first embodiment of the present invention. FIG. 2 is a side sectional view showing a II-II section shown in FIG. FIG. 3 is a partial perspective sectional view of the optical connector 1. The optical connector 1 holds (fixes) the multi-core optical fiber bundle F1, and the end portion of the optical connector 1 faces the end portion of the optical connector that similarly holds the optical fiber, thereby allowing optical connection between the optical fibers. Connector to perform. In FIG. 3, the illustration of the optical fiber bundle F1 is omitted. The optical connector 1 includes a resin ferrule 10 that holds the optical fiber bundle F <b> 1 and a resin lens array 30 that is fixed to one end of the ferrule 10. In the following description, the width direction of the optical connector 1 is described as the X direction, the height direction is defined as the Y direction, and the direction intersecting the X direction and the Y direction (the insertion direction of the optical fiber bundle F1) is described as the Z direction.

  As shown in FIGS. 1 and 2, the ferrule 10 has a rear end 11 and a front end 21. At the rear end 11, an opening 12 for inserting the optical fiber bundle F1 is formed. The opening 12 communicates with the fiber holding hole 13. The fiber holding hole 13 is provided for the purpose of holding each optical fiber F2 (optical waveguide member) constituting the optical fiber bundle F1, and is formed to penetrate from the opening 12 to the front end 21. The fiber holding holes 13 are formed in multiple stages (for example, two stages) in the Y direction, and a plurality of fiber holding holes 13 at each stage are arranged side by side in the X direction. As shown in FIG. 3, each fiber holding hole 13 includes a large-diameter portion 13a formed on the opening 12 side, and a small-diameter portion 13b formed on the front end 21 side that is continuous with the large-diameter portion 13a. Become. The large diameter portion 13a holds the portion of the optical fiber F2 covered with the coating 51, and the small diameter portion 13b holds the portion of the optical fiber F2 (bare fiber) from which the coating 51 has been removed.

  The front end 21 has a fiber holding surface 23 in which the fiber holding hole 13 is formed. The tip surface of the optical fiber F2 is exposed from the fiber holding surface 23. In one example, the fiber holding surface 23 and the tip surface of the optical fiber F2 are flush with each other. An open portion 25 is formed above the fiber holding surface 23 (upward in the Y direction). In a state where the ferrule 10 and the lens array 30 are in contact with each other, the open portion 25 communicates from above the fiber holding surface 23 to between the light incident / exit surface 32 of the lens array 30 and the front end 21. . By introducing an adhesive 50 (not shown in FIG. 3) from the opening 25, the optical fiber F2 inserted into the fiber holding hole 13 is fixed to the fiber holding hole 13, and the ferrule 10 and the lens array 30 are also fixed. Are fixed to each other. The adhesive 50 is filled with a depth that covers all of the end face of the optical fiber F <b> 2 and the lens 34.

  The lens array 30 has a front surface 41 and a back surface 31. The surface 41 includes a flat surface 43 through which the optical axis from the optical fiber F2 held in the fiber holding hole 13 of the ferrule 10 passes. The flat surface 43 is a connection end in the present embodiment, and is optically coupled to the distal end surface of the optical fiber F2. The flat surface 43 allows light incident on the optical fiber F2 from the counterpart optical connector at the connection destination or light emitted from the optical fiber F2 to the counterpart optical connector at the connection destination.

  The back surface 31 includes a light incident / exit surface 32. The light incident / exit surface 32 faces the front end surface of the optical fiber F2, and allows light incident or emitted from the front end surface to pass therethrough. The light incident / exit surface 32 is provided with a lens 34 disposed on the optical path between the optical fiber F <b> 2 and the flat surface 43. The lens 34 collimates the light from the optical fiber F2 or condenses the light toward the optical fiber F2. The number of lenses 34 corresponding to the number of fiber holding holes 13 is provided. The optical axis of each lens 34 substantially coincides with the optical axis of each optical fiber F2 held in each fiber holding hole 13.

  FIG. 4 is an enlarged cross-sectional view showing an optical path connecting the tip surface of the optical fiber F2 and the flat surface 43. As shown in FIG. An alternate long and short dash line in the figure represents an optical axis of light incident on or emitted from the optical fiber F2. In the present embodiment, the first optical path L1 between the lens 34 and the flat surface 43 and the second optical path L2 between the optical fiber F2 and the lens 34 are larger than the refractive index (1.0) of air. Occupied by a medium having a rate. That is, the first optical path L1 is occupied by the constituent material of the lens array 30, and the lens 34, the flat surface 43, and the medium occupying the first optical path L1 are integrally configured as the lens array 30. The second optical path L2 is occupied by the adhesive 50, and the optical fiber F2 and the lens 34 are opposed to each other via a medium (adhesive 50) that occupies the second optical path L2. Then, with the lens 34 as a boundary, the medium on the first optical path L1 side and the medium on the second optical path L2 side have a difference in refractive index.

  In the present embodiment, the refractive index of the medium on the second optical path L2 side is smaller than that of the medium on the first optical path L1 side. In one embodiment, the refractive index of the medium on the first optical path L1 side with respect to the wavelength of 0.8 μm is included in the range of 1.5 to 1.6, and the refractive index of the medium on the second optical path L2 side with respect to the same wavelength is 1. It is included in the range of 3 to 1.5. Specific examples of the medium on the first optical path L1 side (that is, the lens array 30) include PEI (polyetherimide) which is a transparent resin having a light transmittance of 90% or more. Specific examples of the medium on the second optical path L2 side include resins having a transmittance of 90% or more, such as silicone resins, fluorine resin materials, cyclic olefin resins, and organic-inorganic hybrid resins. Examples of the constituent material of the ferrule 10 include PPS (polyphenylene sulfide) which is a resin material having a small linear expansion coefficient, PEI which is a transparent resin, and the like. The ferrule 10 and the lens array 30 are preferably made of materials having substantially the same linear expansion coefficient, and more preferably made of the same material.

Further, as will be described later, the same configuration as that of the optical connector 1 is set within ± 60 ° C. (hereinafter referred to as the use temperature range) from the temperature at which the optical loss between the optical fiber F2 and the flat surface 43 is minimized. The absolute value of the optical loss when connected to another optical connector 1 is preferably 1 dB or less. Also, within the above operating temperature range, the variation in optical loss due to temperature change when connected to another optical connector 1 having the same configuration as the optical connector 1 is preferably within ± 0.4 dB, More preferably within ± 0.3 dB, even more preferably within ± 0.2 dB. In addition, the fluctuation due to the temperature change of the difference between the refractive index of the medium on the first optical path L1 side and the refractive index of the medium on the second optical path L2 side is preferably 15.0 × 10 ⁻⁵ / ° C. or less. still preferable to be .0 × ^{10 -5} / ℃ less, further preferable to be 5.0 × ^{10 -5} / ℃ or less.

  Here, the connection mode between the ferrule 10 and the lens array 30 will be further described. FIG. 5 is a perspective view of the ferrule 10 as viewed obliquely from the front. FIG. 6 is a perspective view of the lens array 30 as viewed obliquely from the rear.

  As shown in FIG. 5, the front end 21 of the ferrule 10 further has a contact surface 24 that contacts the lens array 30. The abutment surface 24 is provided so as to surround three directions, excluding the upward direction (upward in the Y direction), among the four directions of the fiber holding surface 23. The contact surface 24 has a shape that is recessed toward the rear end 11 with respect to the fiber holding surface 23. When the optical fiber F2 is fixed to the fiber holding hole 13, the optical fiber F2 is inserted into the fiber holding hole 13 and then fixed with an adhesive, and then the fiber holding surface 23 including the tip surface of the optical fiber F2 is formed. Polished. At this time, since the abutment surface 24 is recessed toward the rear end 11 with respect to the fiber holding surface 23, the fiber holding surface 23 can be easily polished. The contact surface 24 includes a first connection surface 24a provided in the left-right direction (both sides in the X direction) of the fiber holding surface 23, and a first lower end surface 24b provided in the downward direction (downward in the Y direction) of the fiber holding surface 23. It consists of. The first connection surface 24a and the first lower end surface 24b are flush with each other.

  A first connection portion 22 to which the lens array 30 is connected is formed on the first connection surface 24a. The 1st connection part 22 is a hole in which the 2nd connection part 35 (refer FIG. 6) which is a guide pin of the lens array 30 mentioned later is inserted. The first connection portion 22 is formed on each of the first connection surfaces 24a on both sides in the X direction. That is, the first connection portions 22 are formed on both sides in the X direction at the front end 21 so as to sandwich the fiber holding holes 13 arranged side by side in the X direction.

  As shown in FIG. 6, the back surface 31 of the lens array 30 further includes a contact surface 33 that contacts the ferrule 10. The abutment surface 33 is provided so as to protrude toward the front end 21 of the ferrule 10 with respect to the light incident / exit surface 32, and a second connection surface 33a provided in the left-right direction (both sides in the X direction) of the light incident / exit surface 32. , And a second lower end surface 33b provided in the lower direction (lower in the Y direction) of the light incident / exit surface 32. The second connection surface 33a and the second lower end surface 33b are flush with each other. A rib 36 is provided at the upper end of the light incident / exit surface 32 so as to protrude from the light incident / exit surface 32 to the front end 21 side (opening portion 25 side) of the ferrule 10. The length of the rib 36 protruding from the light incident / exiting surface 32 toward the front end 21 is shorter than the length of protrusion of the contact surface 33. Further, the ribs 36 are provided on both sides in the X direction at the upper end of the light incident / exiting surface 32 so as to be connected to a part of the protruding portion constituting the second connection surface 33a. Thereby, even when the adhesive 50 introduced from the opening portion 25 is cured and a volume change occurs, the light incident / exit surface 32 and the flat surface 43 of the lens array 30 are firmly supported to the left and right via the ribs 36. Therefore, the light incident / exit surface 32 and the flat surface 43 are less likely to warp.

  The second connection surface 33 a is provided with a second connection portion 35 that is connected to the first connection portion 22 of the ferrule 10. The second connection portion 35 is a tapered guide pin inserted into the hole-shaped first connection portion 22, and is provided on each of the second connection surfaces 33a on both sides in the X direction. The second connection portion 35 protrudes from the second connection surface 33 a toward the front end 21 of the ferrule 10 in a state where it is combined with the ferrule 10. Since the tip end of the second connection portion 35 is tapered, the second connection portion 35 can be easily inserted into the first connection portion 22. Moreover, the 1st connection part 22 and the 2nd connection part 35 are arrange | positioned in the Y direction center vicinity in the front end 21 and the back surface 31, respectively. Thereby, the ferrule 10 and the lens array 30 are stably supported via the first connection portion 22 and the second connection portion 35. In the ferrule 10 and the lens array 30, the second connection portion 35 is inserted into the first connection portion 22, and the contact surfaces 24 and 33 come into contact with each other, whereby the separation distance between the lens 34 and the fiber holding surface 23 of the ferrule 10. Is determined.

  More specifically, the first connection surfaces 24a provided on both sides in the X direction of the ferrule 10 and the second connection surfaces 33a provided on both sides in the X direction of the lens array 30 abut. Further, the first lower end surface 24b provided at the lower end in the Y direction of the ferrule 10 and the second lower end surface 33b provided at the lower end in the Y direction of the lens array 30 come into contact with each other, and the lower end contact shown in FIGS. A contact portion 16 is formed. In the lower end contact portion 16, the second lower end surface 33 b protrudes to the front end 21 side of the ferrule 10 from the back surface 31, and the first lower end surface 24 b is closer to the rear end 11 side of the ferrule 10 than the fiber holding surface 23. It is formed so as to be recessed (to form a step) and to accommodate the second lower end surface 33b. Therefore, the lower end abutting portion 16 is formed at a location recessed toward the rear end 11 side of the ferrule 10 with respect to the fiber holding surface 23, and when the adhesive 50 is introduced from the opening portion 25, the adhesive 50 It is possible to make the structure difficult to leak.

  In addition, above the small diameter portion 13b of the fiber holding hole 13 shown in FIG. 3, a receding portion 28 that is a surface inclined obliquely upward from the front end 21 toward the rear end 11 is formed. By forming the retreating portion 28, the opening portion 25 can be widened upward, and the adhesive 50 can be easily introduced even in the configuration in which the rib 36 is provided.

  Refer to FIG. 1 again. The surface 41 of the lens array 30 further includes a third connection portion 44 that is connected to the counterpart optical connector. The third connection portions 44 are formed on both sides in the X direction across a region where light enters and exits the lens array 30 (that is, the flat surface 43). Further, the third connection portion 44 is disposed near the center in the Y direction on the surface 41. One third connection portion 44a is a tapered guide pin protruding from the front surface 41, and the other third connection portion 44b is a hole recessed toward the back surface 31 side for inserting the guide pin. The optical connector 1 is turned upside down by sharing the positional relationship between the third connection portion 44a that is a guide pin and the third connection portion 44b that is a hole into which the guide pin is inserted. Can be connected without. As a result, all connections can be made using the optical connector 1 having the same shape, and the cost reduction is realized by the absence of male and female connectors, the common use of dies, and the like. .

  FIG. 7 is a cross-sectional view schematically showing how a pair of optical connectors 1 are connected to face each other. When the pair of optical connectors 1 face each other, a space H may be provided between these surfaces 41. Such a distance H is suitably realized by, for example, the third connecting portion 44a shown in FIG. 1 being longer than the depth of the third connecting portion 44b. The optical fibers F2 and the lens 34 of the one optical connector 1 and the optical fibers F2 and the lens 34 of the other optical connector 1 are arranged so that the optical axes thereof coincide with each other. Connected.

  In the present embodiment, the tip surface of the optical fiber F2 is disposed at the focal position of the lens 34. Thereby, the beam B emitted from the optical fiber F2 enters the light incident / exit surface 32 of the lens array 30 through the second optical path L2, collimates at the lens 34, and then the first optical path L1 in the lens array 30. And is emitted from the flat surface 43. When the optical connector 1 is connected to the other (opposite) optical connector 1, the collimated beam B enters the flat surface 43 of the other optical connector 1, and the first in the lens array 30 of the optical connector 1. It propagates along the optical path L1 and reaches the lens 34 on the light incident / exit surface 32. Then, the beam B is collected by the lens 34 and enters the front end surface of the optical fiber F2 through the second optical path L2.

  The effects obtained by the optical connector 1 of the present embodiment described above will be described. In this optical connector 1, there is no space between the optical path L1 and the optical path L2 from the optical fiber F2 through the lens 34 to the flat surface 43, and the optical paths L1 and L2 have a refractive index larger than the refractive index of air. Occupied by a medium having Therefore, the refractive index difference existing in the optical path can be made smaller than the refractive index difference caused by the interface with air, and reflection attenuation due to Fresnel reflection can be reduced. Thereby, the increase in connection loss can be suppressed effectively.

  Further, as in the present embodiment, the refractive index of the medium (adhesive 50) on the second optical path L2 side may be smaller than the refractive index of the medium (lens array 30) on the first optical path L1 side. Thereby, the lens 34 can be suitably formed on the inner side surface (light incident / exit surface 32) formed on the back side of the connection end (flat surface 43). In this case, a material suitable for the lens array 30 is selected as the medium on the first optical path L1 side, and a material having a desired refractive index difference with respect to the medium on the first optical path L1 side as the medium on the second optical path L2 side. Can be selected. Further, since the beam reflection between the optical fiber F2 and the lens 34 and the medium (adhesive 50) on the second optical path L2 side is further reduced, the connection loss can be more effectively suppressed.

  In addition, as shown in FIG. 7, in this embodiment, light is exchanged between the optical connectors in the form of a collimated beam having an enlarged beam diameter. Therefore, for example, optical characteristics are hardly deteriorated due to dust or the like attached to the end face (that is, the surface 41) of the optical connector 1, and the positioning accuracy between the optical connectors 1 (that is, the accuracy of the third connection portions 44a and 44b) is low. Even in this case, the optical characteristics are not easily deteriorated (wide tolerance).

  Further, as in the present embodiment, the lens 34, the connection end (flat surface 43), and the medium occupying the first optical path L1 are integrally configured as a lens array 30, and the optical fiber F2 and the lens 34 are Alternatively, they may be opposed to each other via a medium (adhesive 50) occupying the second optical path L2. Thereby, the form which a connection end exposes in the edge part of the optical connector 1 is suitably realizable. Since the lens 34 is not exposed at the end of the optical connector 1, the connection end can be made flat. Thereby, the optical connector 1 with easy cleaning of an edge part can be provided.

  As described above, the absolute value of the optical loss between one optical fiber F2 and the other optical fiber F2 when connected to another optical connector 1 having the same configuration as the optical connector 1 is as follows. In the operating temperature range, it is preferably 1 dB or less. In the present embodiment, since there is a space between the flat surfaces 43, it is inevitable that a refractive index interface between the medium (lens array 30) occupying the first optical path L1 and the air occurs. However, there is no interface between each medium and air inside both optical connectors 1. Therefore, a connector with a lens capable of optical coupling with good optical characteristics within a temperature range assumed at the time of use is provided.

  Here, FIG. 8 is a diagram for explaining a resin material suitable as a medium on the second optical path L2 side when the medium on the first optical path L1 side, that is, the lens array 30 is made of PEI. The horizontal axis in FIG. 8 represents the refractive index, and the vertical axis represents the refractive index change per 1 ° C. temperature change. As described above, the refractive index of the medium on the second optical path L2 side used in this embodiment is larger than the refractive index of air and smaller than the refractive index of the medium on the first optical path L1 side. Accordingly, as the medium on the second optical path L2 side, the area A1 in the figure (the refractive index is smaller than the refractive index (PEI: 1.64) of the medium on the first optical path L1 side. In the figure, the refractive index is 1.0 to 1). .3 is omitted) is preferably used.

Further, in the optical connector 1 of the present embodiment, it is desirable that the fluctuation of the optical characteristics within the use temperature range is small in order to keep the optical coupling efficiency favorable against the temperature fluctuation within the use temperature range. For example, in FIG. 8, among the materials included in the region A1, the material included in the region A2 is preferable, the material included in the region A3 is more preferable, and the material included in the region A4 is most preferable. In the region A2, the refractive index change is larger than 0 (/ ° C.) and is 2.2 × 10 ⁻⁴ (/ ° C.) or less (that is, the refractive index difference from the medium on the first optical path L1 side is 1.2 × 10 ^{− 4} (/ ° C.), and the region A3 has a refractive index change larger than 0 (/ ° C.) and not more than 1.7 × 10 ⁻⁴ (/ ° C.) (that is, with the medium on the first optical path L1 side). Refractive index difference represents a range of 0.8 × 10 ⁻⁴ (/ ° C.), and region A4 has a refractive index change larger than 0 (/ ° C.) and 1.3 × 10 ⁻⁴ (/ ° C.) or less ( That is, it represents a range where the refractive index difference with the medium on the first optical path L1 side is 0.4 × 10 ⁻⁴ (/ ° C.). This will be described in detail below.

FIG. 9 is a diagram showing the temperature characteristics of the optical connector 1 according to the present embodiment, and shows the fluctuation of the optical characteristics (light loss) due to temperature changes when the two optical connectors 1 are arranged facing each other. Yes. In FIG. 9, four graphs G11 to G14 show cases where resins having different refractive index temperature dependencies are used as the medium on the second optical path L2 side. The medium on the first optical path L1 side is PEI. The refractive index of PEI at the design reference temperature is 1.64, and the temperature change rate of the refractive index is −9 × 10 ⁻⁵ (/ ° C.). The refractive index of the medium on the second optical path L2 side at the design reference temperature is 1.45 to 1.50.

  In FIG. 9, as an example, the design reference temperature at which the optical loss is the lowest is 20 °. The optical loss at the design reference temperature is 0.6 dB in the graphs G11 to G14. In an optical connector for connecting optical fibers to each other, it is desirable that the fluctuation range (relative value with respect to the optimum value) of the optical loss is within ± 0.4 dB within the operating temperature range (that is, within the design reference temperature ± 60 ° C.). . Thereby, the fluctuation | variation of the coupling efficiency of optical fiber F2 can fully be suppressed in the range of the temperature change assumed at the time of use of the optical connector 1. FIG. The fluctuation range of the optical loss is preferably within ± 0.3 dB, and more preferably within ± 0.2 dB in consideration of the optical loss fluctuation due to the dimensional variation of the ferrule 10 at the time of manufacture. In addition, it is desirable that the absolute value of optical loss within the operating temperature range be within 0.1 dB.

In the graphs G11 to G14, the temperature change rate of the refractive index of the medium on the second optical path L2 side is −2 × 10 ⁻⁴ (corresponding to the region A2 in FIG. 8) and −1.5 × 10 ⁻⁴ (FIG. 8). Of the optical loss with respect to the temperature change in the case of -1 × 10 ⁻⁴ (corresponding to the region A4 in FIG. 8) and −5 × 10 ⁻⁵ (corresponding to the region A4 in FIG. 8). It shows the fluctuation. As shown in the graph G11, when the temperature change rate of the refractive index is −2 × 10 ⁻⁴ , the absolute value of the optical loss at a temperature of 80 ° C. is 1.5 dB, and the relative value (increase amount) of the optical loss. Is 0.9 dB. Further, as shown in the graph G12, when the temperature change rate of the refractive index is −1.5 × 10 ⁻⁴ , the absolute value of the optical loss at a temperature of 80 ° C. is 1.2 dB, and the relative value of the optical loss. (Increase amount) is 0.6 dB. On the other hand, as shown in the graph G13, when the temperature change rate of the refractive index is −1 × 10 ⁻⁴ , the absolute value of the optical loss at a temperature of 80 ° C. is 0.8 dB, and the relative value of the optical loss. (Increase amount) is 0.2 dB, which is favorable. As shown in the graph G14, when the temperature change rate of the refractive index is −5 × 10 ⁻⁵ , the absolute value of the optical loss at a temperature of 80 ° C. is 0.7 dB, and the relative value of the optical loss (increase) Amount) is 0.1 dB, which is even better.

To summarize the above considerations, by defining the temperature variation difference in refractive index between the medium on the first optical path L1 side and the medium on the second optical path L2 side, light having desired optical characteristics within the operating temperature range is obtained. A connector 1 is obtained. That is, in order for the fluctuation value of the optical loss within the operating temperature range to be within ± 0.4 dB, the refractive index fluctuation difference with respect to the temperature change of each medium on the first optical path L1 side and the second optical path L2 side is 15 It may be 0.0 × 10 ⁻⁵ / ° C. or less. Further, since the fluctuation value of the optical loss within the operating temperature range is within 0.3 dB, the refractive index fluctuation difference with respect to the temperature change of each medium on the first optical path L1 side and the second optical path L2 side is 10. It may be 0 × 10 ⁻⁵ / ° C. or less. Further, since the fluctuation value of the optical loss within the operating temperature range is within 0.2 dB, the refractive index fluctuation difference with respect to the temperature change of each medium on the first optical path L1 side and the second optical path L2 side is 5. It may be 0 × 10 ⁻⁵ / ° C. or less.

  When PEI is used as the medium on the first optical path L1 side, as shown in FIG. 8, it is difficult to realize the above characteristics if a silicone resin or a fluororesin is used as the medium on the second optical path L2 side. The above-mentioned characteristics can be suitably realized by using a system resin, an organic-inorganic hybrid resin, or the like.

FIG. 10 is a diagram illustrating temperature characteristics of the optical connector 1 according to the present embodiment. In FIG. 10, a graph G21 shows a case where a cyclic olefin resin is used as a medium on the second optical path L2 side, and a graph G22 shows a case where an organic-inorganic hybrid resin is used as a medium on the second optical path L2 side. ing. In these graphs G21 and G22, the medium on the first optical path L1 side is PEI. The refractive index of the cyclic olefin resin at the design reference temperature (20 ° C.) is 1.50, the temperature change rate of the refractive index is −1 × 10 ⁻⁴ / ° C., and the refractive index fluctuation difference with PEI with respect to the temperature change is 1 ×. 10 ⁻⁵ / ° C. The refractive index of the organic-inorganic hybrid resin at the design reference temperature (20 ° C.) is 1.48, the temperature change rate of the refractive index is −1.3 × 10 ⁻⁴ / ° C., and the refractive index with the PEI with respect to the temperature change. The variation difference is 4 × 10 ⁻⁵ / ° C.

  As shown in the graph G21, when a cyclic olefin resin is used as the medium on the second optical path L2 side, the absolute value of the optical loss is 0.75 dB even at 80 ° C., and the relative value of the optical loss within the operating temperature range is It was 0.05 dB, and good results were obtained. Further, as shown in the graph G22, when an organic-inorganic hybrid resin is used as the medium on the second optical path L2 side, the absolute value of the optical loss is 0.8 dB even at 80 ° C., and the optical loss within the operating temperature range. The relative value was 0.1 dB, and good results were obtained.

(Second Embodiment)
FIG. 11 is a side sectional view showing an optical connector 2 according to the second embodiment of the present invention. The optical connector 2 holds (fixes) the multi-core optical fiber bundle F1, and optically connects the optical fibers by abutting the end of the optical connector 2 that similarly holds the optical fiber. It is a connector. The optical connector 2 includes a resin ferrule 60 that holds the optical fiber bundle F1.

  The ferrule 60 has a rear end surface 61 and a front end surface 71. In the rear end face 61, an opening 62 for inserting the optical fiber bundle F1 is formed. The opening 62 communicates with the fiber holding hole 63. The fiber holding hole 63 is provided for the purpose of holding each optical fiber F2 (optical waveguide member) constituting the optical fiber bundle F1, and is formed to penetrate from the opening 62 to the front end face 71. A plurality of fiber holding holes 63 are arranged side by side in the X direction.

  The ferrule 60 has a side surface 81 that connects the rear end surface 61 and the front end surface 71. An opening 64 is formed in the side surface 81. The opening 64 is recessed toward the side surface 82 opposite to the side surface 81, and has inner side surfaces 64a and 64b that intersect the optical axis direction of the optical fiber F2. The inner side surfaces 64a and 64b face each other. The fiber holding hole 63 communicates between the opening 62 and the inner surface 64b, and the optical fiber F2 protrudes from the inner surface 64b toward the inside of the opening 64. The distal end surface of the optical fiber F2 is positioned in contact with the inner side surface 64a. An adhesive (not shown) is introduced into the opening 64, and the tip of the optical fiber F <b> 2 is fixed to the ferrule 60.

  A recess 72 is formed in the front end surface 71 of the ferrule 60. A lens 84 is provided on the bottom surface of the recess 72. The lens 84 collimates the light from the optical fiber F2 or condenses the light toward the optical fiber F2. The number of lenses 84 corresponding to the number of fiber holding holes 63 is provided. The optical axis of each lens 84 substantially coincides with the optical axis of each optical fiber F <b> 2 held in each fiber holding hole 63.

  The optical connector 2 further includes a resin portion 73 that embeds the recess 72. The surface 73 a of the resin portion 73 is formed flat so as to be flush with the front end surface 71 of the ferrule 60. The surface 73a is a connection end that allows the optical axis from the optical fiber F2 to pass through, and is optically coupled to the distal end surface of the optical fiber F2 via the lens 84. In other words, the lens 84 is disposed on the optical path between the optical fiber F2 and the surface 73a. The surface 73a allows light that is incident on the optical fiber F2 from the connection partner optical connector or light emitted from the optical fiber F2 to the connection partner optical connector.

  FIG. 12 is an enlarged cross-sectional view showing an optical path connecting the tip surface of the optical fiber F2 and the surface 73a. In the present embodiment, the first optical path L3 between the lens 84 and the surface 73a and the second optical path L4 between the optical fiber F2 and the lens 84 are larger than the refractive index of air (1.0). Occupied by a medium having That is, the first optical path L3 is occupied by the constituent material of the resin portion 73. The second optical path L4 is occupied by the constituent material of the ferrule 60, and the lens 84, the inner surface 64a, and the medium occupying the first optical path L3 are integrally configured as the ferrule 60. Then, with the lens 84 as a boundary, the medium on the first optical path L3 side and the medium on the second optical path L4 side have a refractive index difference.

  In the present embodiment, the refractive index of the medium on the second optical path L4 side is larger than that of the medium on the first optical path L3 side. In one embodiment, the refractive index of the medium on the second optical path L4 side for the wavelength of 0.8 μm is included in the range of 1.5 to 1.6, and the refractive index of the medium on the first optical path L3 side for the same wavelength is 1. It is included in the range of 0 to 1.5.

  Even an optical connector having the configuration of the present embodiment can achieve the same effects as those of the first embodiment. That is, in the optical connector of the present invention, in addition to the lens array and the ferrule being configured separately, they can be configured as a single unit. Further, either a configuration in which a lens is formed on the back side of the connection end or a configuration in which a lens is formed at the connection end may be used. In the present embodiment, since the lens array and the ferrule are integrally formed, the number of parts can be reduced.

(Modification)
FIG. 13 is a diagram illustrating a modification of the second embodiment. The difference from the second embodiment in the present modification is the magnitude relationship between the lens orientation and the refractive index before and after the lens. That is, in this modification, a lens 85 is provided instead of the lens 84 shown in FIG. The difference between the lenses 84 and 85 is that the lens 84 of FIG. 12 is convex forward (Z-axis positive direction), whereas the lens 85 of this modification is convex backward (Z-axis negative direction). Is a point.

  In this modification, the refractive index of the medium on the second optical path L4 side is smaller than that of the medium on the first optical path L3 side. In one embodiment, the refractive index of the medium on the first optical path L3 side with respect to the wavelength of 0.8 μm is included in the range of 1.5 to 1.6, and the refractive index of the medium on the second optical path L4 side with respect to the same wavelength is 1. It is included in the range of 0 to 1.5.

  Even with the configuration of this modification, the same effects as those of the second embodiment described above can be obtained.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in each of the above embodiments, the case where the first optical path and the second optical path are each occupied by a single material has been exemplified. However, in the present invention, the first optical path and the second optical path are each occupied by two or more materials. May be. For example, a part of the ferrule and an adhesive may be interposed between the tip surface of the optical waveguide member and the lens. Further, an adhesive and a part of the ferrule may be interposed between the lens and the connection end.

DESCRIPTION OF SYMBOLS 1, 2 ... Optical connector, 10 ... Ferrule, 11 ... Rear end, 12 ... Opening part, 13 ... Fiber holding hole, 13a ... Large diameter part, 13b ... Small diameter part, 16 ... Lower end contact part, 21 ... Front end, 22 DESCRIPTION OF SYMBOLS 1st connection part, 23 ... Fiber holding surface, 24 ... Contact surface, 24a ... 1st connection surface, 24b ... 1st lower end surface, 25 ... Opening part, 28 ... Retraction part, 30 ... Lens array, 31 ... Back surface 32 ... Light entrance / exit surface, 33 ... Contact surface, 33a ... Second connection surface, 33b ... Second lower end surface, 34 ... Lens, 35 ... Second connection portion, 36 ... Rib, 41 ... Surface, 43 ... Flat Surface 44, 3rd connection part 50 ... Adhesive, 51 ... Cover, 60 ... Ferrule, 61 ... Rear end face, 62 ... Opening part, 63 ... Fiber holding hole, 64 ... Opening part, 71 ... Front end face, 72 ... Recessed part 73 ... Resin part 81 ... Side face 82 ... Side face 84, 85 ... Lens, F1 ... Optical fiber Bar bundle, F2 ... optical fiber, L1, L3 ... first optical path, L2, L4 ... second optical path.

Claims (12)

A connection end that is optically coupled to the optical waveguide member and allows light incident on the optical waveguide member from the connection-destination optical connector or light emitted from the optical waveguide member to the connection-destination optical connector;
A lens disposed on an optical path between the optical waveguide member and the connection end;
With
The first optical path between the lens and the connection end, and the second optical path between the optical waveguide member and the lens are occupied by a medium having a refractive index greater than that of air,
The lens possess the medium and a refractive index difference from each other of said medium and said second optical path side of said first optical path side as a boundary,
The refractive index of the medium on the second optical path side is smaller than the refractive index of the medium on the first optical path side;
The refractive index of the medium on the first optical path side is included in a range of 1.5 to 1.6,
An optical connector in which a refractive index of the medium on the second optical path side is included in a range of 1.3 to 1.5 . Absolute value of optical loss when connected to another optical connector having the same configuration as the optical connector within ± 60 ° C. from the temperature at which the optical loss between the optical waveguide member and the connection end is minimized. There is 1dB or less, the optical connector according to claim 1. Optical loss due to temperature change when connected to another optical connector having the same configuration as the optical connector within ± 60 ° C. from the temperature at which the optical loss between the optical waveguide member and the connection end is minimized. variation of is within ± 0.4 dB, the optical connector according to claim 1 or 2. A connection end that is optically coupled to the optical waveguide member and allows light incident on the optical waveguide member from the connection-destination optical connector or light emitted from the optical waveguide member to the connection-destination optical connector;
A lens disposed on an optical path between the optical waveguide member and the connection end;
With
The first optical path between the lens and the connection end, and the second optical path between the optical waveguide member and the lens are occupied by a medium having a refractive index greater than that of air,
The medium on the first optical path side and the medium on the second optical path side have a refractive index difference from each other with the lens as a boundary,
Absolute value of optical loss when connected to another optical connector having the same configuration as the optical connector within ± 60 ° C. from the temperature at which the optical loss between the optical waveguide member and the connection end is minimized. Is an optical connector having 1 dB or less. A connection end that is optically coupled to the optical waveguide member and allows light incident on the optical waveguide member from the connection-destination optical connector or light emitted from the optical waveguide member to the connection-destination optical connector;
A lens disposed on an optical path between the optical waveguide member and the connection end;
With
The first optical path between the lens and the connection end, and the second optical path between the optical waveguide member and the lens are occupied by a medium having a refractive index greater than that of air,
The medium on the first optical path side and the medium on the second optical path side have a refractive index difference from each other with the lens as a boundary,
Optical loss due to temperature change when connected to another optical connector having the same configuration as the optical connector within ± 60 ° C. from the temperature at which the optical loss between the optical waveguide member and the connection end is minimized. An optical connector whose fluctuation is within ± 0.4 dB. The optical connector according to claim 3 or 5, wherein the variation is within ± 0.3 dB.   The optical connector according to claim 6, wherein the variation is within ± 0.2 dB. The refractive index of the medium of the first optical path side, fluctuation due to a temperature change in the difference between the refractive index of the medium of the second light path side is 15.0 × 10 -5 ^/ ℃ less, claim 3 Or the optical connector of 5. The variation due to a temperature change in the difference between the refractive index of the medium on the first optical path side and the refractive index of the medium on the second optical path side is 10.0 × 10 ⁻⁵ / ° C. or less. The optical connector as described in. The variation due to temperature change of the difference between the refractive index of the medium on the first optical path side and the refractive index of the medium on the second optical path side is 5.0 × 10 ⁻⁵ / ° C. or less. The optical connector as described in. The lens, the connection end, and the medium occupying the first optical path are integrally configured,
The optical connector according to claim 1, wherein the optical waveguide member and the lens face each other with the medium occupying the second optical path. A connection end that is optically coupled to the optical waveguide member and allows light incident on the optical waveguide member from the connection-destination optical connector or light emitted from the optical waveguide member to the connection-destination optical connector;
A lens disposed on an optical path between the optical waveguide member and the connection end;
With
The first optical path between the lens and the connection end, and the second optical path between the optical waveguide member and the lens are occupied by a medium having a refractive index greater than that of air,
The medium on the first optical path side and the medium on the second optical path side have a refractive index difference from each other with the lens as a boundary,
The medium on the first optical path side is a polyetherimide;
An optical connector in which a refractive index at 20 ° C. of the medium on the second optical path side is included in a range of 1.45 to 1.50.

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