JP2005215219A - Bidirectional optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical component for a bidirectional optical communication, in which far-end crosstalks are reduced and which is constituted to be compact and is highly efficient. <P>SOLUTION: The bidirectional module has one optical fiber; a light-receiving element; a light-emitting element; and an optical component condensing and reflecting a light signal, and transmits and receives the signal through the one optical fiber, wherein the optical component forms a pentagonal section of a first face opposite to the end face of the optical fiber, a second face adjacent to the first face and opposite to the light-receiving element, a third face opposite to the second face, adjacent to the first face and opposite to the light-emitting element, a fourth face which reflects received light incident from the first face to the second face, and a fifth face which reflects the transmitted light, made incident from the third face toward the first face, condensing lenses for condensing the received light are formed integrally with the first face and the second face of the optical component, respectively, condensing lenses for condensing the transmitted light are formed integrally with the first face and the third face, respectively, optical isolators are arranged between the second face of the optical component and the light-receiving element, and between the third face of the optical component and the light-emitting element, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical component used for bidirectional optical communication in which light is transmitted / received through a single optical fiber, and in particular, is disposed opposite to an end face of the optical fiber to guide received light emitted from the optical fiber to a light receiving element. The present invention relates to a bidirectional optical module that causes transmission light emitted from a light emitting element to enter an end face of an optical fiber.

  FIG. 5 shows an example of a conventional bidirectional optical module 40. In this example, a prism 11 which is an optical component and condensing lenses 12 to 15 integrally formed on the surface are used. In FIG. 5, the alternate long and short dash line indicates the optical fiber axis 21 a disposed with respect to the optical component 40.

  As shown in FIG. 5, the optical fiber 21, the prism 11 that is an optical component, the light receiving element 22 and the light emitting element 23 constitute a bidirectional optical module 40, and light is transmitted and received. As shown in FIG. 5, the axis 21a of the optical fiber 21 disposed in close proximity to the condensing lenses 12 and 14 located on the surface 11a of the prism 11 is not the interface between the condensing lenses 12 and 14, as shown in FIG. The lens 12 is slightly shifted to the condensing lens 12 side.

In addition, the inclination angles β ₁ and β ₂ formed by the surface 11d forming the reception-side reflection surface and the surface 11e forming the transmission-side reflection surface with respect to the optical fiber axis 21a are set at angles smaller than 45 °.

  Further, the light receiving element 22 is arranged not in the front surface of the condensing lens 13 but in a direction away from the surface 11a of the prism 11 in the direction of the axis 21a with respect to the front surface of the condensing lens 13. Similarly, the light emitting element 23 is also arranged not in front of the condensing lens 15 but in a direction away from the surface 11a in the direction of the axis 21a with respect to the front of the condensing lens 15. The element surfaces 22a and 23a of the light receiving element 22 and the light emitting element 23 are both parallel to the direction of the axis 21a.

Received light 31 emitted from the end face of the optical fiber 21 is condensed by the condensing lens 12 and incident on the prism 11, reflected by the surface 11 d, directed to the surface 11 b, and condensed by the condensing lens 13. Yes. At this time, in this conventional example, the received light 31 is incident obliquely with respect to the element surface 22 a of the light receiving element 22. On the other hand, the transmission light 32 emitted from the light emitting element 23 is condensed by the condensing lens 15 and enters the prism 11, faces the surface 11 a, is condensed by the condensing lens 14, and is an end face of the optical fiber 21. Is incident.
JP 2003-337264 A

  In such a bi-directional optical module, crosstalk and coupling efficiency are major problems in performance, and reduction of crosstalk and coupling efficiency is an important issue.

  Crosstalk means that in this type of optical component, the transmitted light leaks to the receiving side of the local station and enters the light receiving element of the local station. What is caused by reflection at the optical interface or near the end face of the optical fiber is called near end crosstalk. On the other hand, each optical interface at the branching part of the counterpart station, the far end face of the optical fiber, and further the reflection caused by the light receiving element face and the light emitting element face of the counterpart station are called far end crosstalk.

  In the bidirectional optical module shown in FIG. 5, this far-end crosstalk cannot be significantly reduced.

  That is, as shown in FIG. 5, since the inclination angles of the surfaces (reflective surfaces) 11d and 11e of the prism 11 are gentle, the received light 31 and the transmitted light 33 are shown in FIG. The light reflected by 11e travels backward (in a direction away from the surface 11a), and enters and exits the element surfaces 22a and 23a of the light receiving element 22 and the light emitting element 23 arranged in that direction obliquely. . Therefore, the light reflected by these element surfaces 22 a travels further rearward, and a part of the light emitted by the element surface 23 a is incident on the end face of the optical fiber 21.

  Accordingly, in FIG. 5A, the path of the light reflected by the element surfaces 22a and 23a is not close to the path where the light is incident. That is, the path where the reflected light is incident is traced back to the optical fiber 21 again. However, the far-end crosstalk of the partner station does not occur, and the far-end crosstalk cannot be significantly reduced in this respect.

  Further, the light receiving element 22 is arranged not in front of the condensing lens 13 but in a direction away from the surface 11a of the prism 11 in the direction of the axis 21a with respect to the front surface of the condensing lens 13. Similarly, the light emitting element 23 is also arranged not in front of the condensing lens 15 but in a direction away from the surface 11a in the axis 21a direction with respect to the front of the condensing lens 15. The coupling efficiency is called coupling between the light source and the fiber when light enters the optical fiber from the light source. A comparison between the total light power emitted from the light source and the power of the light incident on the fiber is called coupling efficiency, and the above arrangement has a problem in coupling efficiency.

  Further, as shown in FIG. 5B, the light emitting element 23 is also arranged not in front of the condensing lens 15 but in a direction away from the surface 11a in the axis 21a direction with respect to the front surface of the condensing lens 15. As a result, the coupling efficiency of light cannot be increased, and thus an optical component for bidirectional optical communication having high reliability cannot be obtained.

  The object of the present invention has been made in view of such problems, and the technical problem is that both the far-end crosstalk can be greatly reduced and the coupling efficiency can be increased. The object is to provide a dioptric module.

  In order to solve the above-described problems, the present invention includes a single optical fiber, a light receiving element and a light emitting element, and an optical component that collects and reflects an optical signal, and transmits and receives through the single optical fiber. In the bidirectional module to perform, the optical component includes a first surface facing the end surface of the optical fiber, a second surface adjacent to the first surface and facing the light receiving element, and the second surface. A third surface facing the surface and adjacent to the first surface and facing the light emitting element; and a fourth surface that reflects received light incident from the first surface toward the second surface. And a fifth surface that reflects the transmission light incident from the third surface toward the first surface, form a pentagonal cross section, and the first surface and the second surface of the optical component. A condensing lens for condensing the received light is integrally formed on each of the surfaces, and is formed on the first surface and the third surface. A condensing lens for condensing the transmission light is integrally formed, and between the second surface of the optical component and the light receiving element, and between the third surface of the optical component and the light emitting element. In addition, an optical isolator is arranged respectively.

  The fourth surface and the fifth surface of the optical component each have an angle of 45 ° or less with respect to the axial direction of the optical fiber.

  Furthermore, a lens for condensing the transmission light and a lens for condensing the reception light are respectively formed on the first surface of the optical component.

  Further, the radius of the lens for condensing the transmission light and the lens for condensing the reception light are different.

Further, the fourth and fifth surfaces of the optical component are provided with a total reflection dielectric thin film made of one or more of Al, Au, SiO, MgF ₂ , TiO ₂ , and SiO ₂ .

  The total reflection dielectric thin film has a thickness of 1 nm to 100 nm.

  Furthermore, the first surface and the fifth surface of the optical component are each made spherical or aspherical.

  As described above, according to the present invention, the configuration in which the optical isolator is disposed between the second surface of the prism and the light receiving element prevents crosstalk on the receiving side by blocking reflection from the light receiving element surface. In addition, the optical isolator is arranged between the third surface of the prism and the light emitting element, so that a part of the received light incident from the first surface is the third surface. It is possible to obtain a bidirectional optical module having a high coupling efficiency and high performance without adversely affecting the light emitting element by blocking the received light reflected toward the.

  Further, in the present invention, since the reflecting surface side of the prism is configured by the shape of the condensing lens, it is possible to improve the light coupling efficiency and the photoelectric conversion efficiency, to be small in size, and to be inexpensive. A bidirectional optical module can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. In addition, the same code | symbol shall be used about the same thing as a prior art example.

  FIG. 1 is a view showing an embodiment of an optical component 60 used in the bidirectional optical module of the present invention, where (a) shows a front view and (b) shows a side view. In this example, the receiving light path (light receiving element side) and the transmitting light path (light transmitting element side) are integrally formed using the same material, so that the manufacturing cost can be reduced.

  FIG. 1 shows a configuration in which a light emitting element and a light receiving element can be arranged to face each other in an optical component having a structure in which the reception light path and the transmission light path are integrally formed of the same material. In an embodiment, the optical component 60 is configured using a prism 62 having a pentagonal cross-sectional shape.

  As shown in FIG. 1A, the second surface 62b and the third surface 62c adjacent to the first surface 62a of the prism 62, respectively, and the first surface 62a are provided for receiving and transmitting. Two condensing lenses 63 and 64 are integrally formed, and condensing lenses 65 and 66 are also integrally formed on the second surface 62b and the third surface 62c, respectively.

  As shown in the side view of FIG. 1B, the second surface 62b and the third surface 62c are perpendicular to the first surface 62a, respectively, and the remaining pentagonal fourth surface 62d and fifth The surface 62e is an indented surface, and the corner 62f formed by the fourth surface 62d and the fifth surface 62e is close to the first surface 62a as shown in FIG. Located in position.

  In this prism 62, a portion located above the corner portion 62f in FIG. 1B constitutes a light receiving portion, and a portion located below the corner portion 62f constitutes a light transmitting portion. Two condensing lenses 63 and 64 for reception and transmission are integrally formed on the first surface 62a of the prism 62 having the shape as described above, which faces the end face of the optical fiber. Each of the optical lenses 63 and 64 has a structure in which a part thereof is cut out and the cut out parts are continuously coupled. Further, condensing lenses 65 and 66 are integrally formed on the second surface 62b and the third surface 62c, respectively, and the fourth surface 62d and the fifth surface 62e functioning as reflecting surfaces are spherical. It is supposed to make.

  In this embodiment, the optical component 60 is configured such that the condensing lenses 63 to 66 are integrally formed on the prism 62 as described above, and the surfaces 62d and 62e are spherical or aspherical. ing. Furthermore, it is manufactured using an inexpensive resin (for example, acrylic, polycarbonate, amorphous polyoprene fin, etc.) with high transparency (transmittance). At this time, for example, the condensing lenses 63 to 66 and the surfaces 62d and 62e The prism 62 can be integrally formed by two-color molding. In addition, you may manufacture the condensing lenses 63-66, the surfaces 62d and 62e, and the prism 62 with general optical system glass.

The inclination angles α ₁ and α ₂ formed by the surface 62d forming the reception-side reflection surface and the surface 62e forming the transmission-side reflection surface with respect to the optical fiber axis 21a are set to 45 ° or less, and 35 ° or more. An angle of about 45 ° or less is preferable.

The fourth surface 62d that reflects the reception light incident from the first surface 62a of the prism 62 toward the second surface 62b and the transmission light that is incident from the third surface toward the first surface 62a. A total reflection film 67 is formed on the reflection surface of the fifth surface 62e to be reflected. The total reflection film 67 is formed of a dielectric multilayer film of a metal film such as aluminum or gold and a non-metal film, or the total reflection film 67 is selected from Al, Au, SiO, MgF ₂ , TiO ₂ , and SiO _2. It is preferable to use one or more of these.

  The total reflection film 67 is a highly reliable film having a high reflectance in a wide range of ultraviolet, visible, and infrared regions. In order to increase the reflectance of the total reflection film 67, a multilayer dielectric film is used, and the total reflection film 67 preferably has a thickness in the range of 1 nm to 100 nm, and the wavelength range of 500 nm to 850 nm. The total reflectance is preferably 99.5% or more. By setting it within this range, the strength of the film surface of the total reflection film 67 is strong, the cleaning can be endured, and strong outgoing light can be emitted from the transmission side and the reception side.

  By forming the total reflection film 67 on the fourth surface 62d and the fifth surface 62e, the emitted light can be coupled to the fiber from the transmission side and the reception side without waste, so that the yield can be improved.

  FIG. 2 shows a bidirectional optical module of the present invention using the optical component 60 shown in FIG. The light emitting element 23 is disposed opposite to the condensing lens 66 on the surface 62c of the prism 62, while the light receiving element 22 is disposed opposite to the condensing lens 65 on the surface 62b of the prism 62, whereby the light emitting element 23 and the light receiving element 22 are arranged. Are arranged in parallel with each other. The optical fiber axis 21 a of the optical fiber 21 coincides with the optical fiber axis 21 a of the condensing lens 63 on the receiving side on the surface 62 a of the prism 62.

  As shown in FIG. 2, the received light 15a emitted from the end face 21b of the optical fiber 21 is collected by the condensing lens 63 and is incident on the prism 62 to be a spherical or aspheric curved surface. The light is totally reflected by the total reflection film 67 on the surface 62 d, reaches the surface 62 b, is condensed by the condensing lens 65, passes through the optical isolator 55, and enters the light receiving element 22. When a part of the received light 15a incident on the light receiving element 22 is reflected by the surface of the light receiving element 22a, the reflected light 15aa is again incident on the optical isolator 55 as shown in FIG. It is blocked by the optical isolator 55.

  As described above, the reflected light 15aa is reflected by the surface of the light receiving element 22a and is blocked by the optical isolator 55, so that crosstalk can be greatly reduced.

  As shown in FIG. 2, a part of the received light 15a emitted from the end face 21b of the optical fiber 21 is condensed by the condensing lens 64 and enters the prism 62, and has a spherical or aspherical shape. The outgoing light totally reflected by the total reflection film 67e of 62e and totally reflected is received light 15a1, and the received light 15a1 reaches the surface 62c, is condensed by the condensing lens 66, and enters the optical isolator 55. As a result, the received light 15a1 is blocked by the optical isolator 55.

  As described above, the received light 15a1 is blocked by the optical isolator 55, so that it is possible to avoid performance degradation of the light emitting element 23 and to improve stable light emission and coupling efficiency.

  FIG. 4 shows how the light transmitting side is performed using the optical component 60 shown in FIG. 1, and the light emitting element 23 is disposed opposite to the condensing lens 66 on the surface 62c of the prism 62. Thus, the light emitting elements 23 are arranged in parallel to face each other. The optical axis of the optical fiber 21 coincides with the optical fiber axis of the condensing lens 64 on the transmission side on the surface 62 a of the prism 62.

  The transmission light 16a emitted from the light emitting element 23 passes through the optical isolator 55, is collected by the collecting lens 66, enters the prism 62, and is a total reflection film 67 on the surface 62e having a spherical or aspherical shape. Is totally reflected, reaches the surface 62a, is condensed by the condensing lens 64, and is incident on the end surface 21b of the optical fiber 21.

  Thus, by using the prism 62 having the shape as shown in the figure, the transmission light path and the reception light path can be separated, and the light emitting element 23 and the light receiving element 22 can be arranged to face each other. The light receiving element 22 or the light emitting element 23 is arranged such that the surface 62a of the prism 62 is not shifted in the direction of the axis 21a with respect to the front surface of the condensing lens 65 or the condensing lens 66.

  As an example of the bidirectional optical module of the present invention, the one shown in FIG. 2 was prepared. An optical fiber, a prism having a pentagonal cross section, two optical isolators, a light receiving element, and a light emitting element were bonded to each other.

The material of the prism and the condensing lens is BK7 which is a general optical system glass, the prism 62 and the reflection angle α ₁ + α ₂ are 90 °, and the condensing lens 63 has a radius of 2.5 mm. The lens 64 has a radius of 1.5 mm, the condensing lenses 65 and 66 have a radius of curvature of 1.0 mm, the light receiving element 22 has an opening shape of 0.12 mm, and the light emitting element 23 has a size of 0.5 mm. 0.5 mm × t 0.1 mm.

A metal film of the total reflection film 67 was formed of Au, SiO, MgF ₂ , TiO ₂ , and SiO _{2 on} the reflection surfaces of the fourth surface 62d and the fifth surface 62e. The total reflection film 67 is formed to have a multilayer laminated film thickness of 75 nm, a wavelength range of 500 nm to 850 nm, and a total reflectance of 99.5% or more.

On the other hand, what was shown in FIG. 5 as a comparative example was produced. The comparative example is different from the embodiment of the present invention in that the reflection angle β ₁ + β ₂ is 80 °, and the light receiving element 22 or the light emitting element 23 has an axis 21a with respect to the front surface of the condensing lens 13 or the condensing lens 15. The surface 11a of the prism 11 is arranged at a position shifted in the direction.

  Eleven samples of the bidirectional optical module of the inventive example and the comparative example were prepared, and the optical characteristics (coupling efficiency, crosstalk) were measured. The optical characteristics were measured under the conditions that the light wavelength λo was 670 nm and the light output intensity of the light emitting diode was 0 dBm or 1 mW. For the measurement system, Agilent 86142B Optical Spectrum Analyzer manufactured by Agilent was used, and an optical power sensor module (light wavelength λo of 670 nm) was used as a fixed laser light source module (LED).

Table 1 shows the optical property evaluation results of the optical devices of Examples and Comparative Examples of the present invention under the above measurement conditions.

  As a result, the average of 11 coupling efficiencies in the example of the present invention was 0.10 dB, and the average of crosstalk was −65 dB. The average of the 11 coupling efficiencies of the comparative example was 0.3 dB, and the average of far-end crosstalk was −60 dB. Therefore, it was confirmed that the examples of the present invention had sufficiently better optical characteristics than those of the comparative examples, and those values were also stable.

  As is clear from the above results, in the comparative example, the light receiving element and the light emitting element are not shifted from the prism surface in the axial direction with respect to the front surface of the condensing lens, not the front surface of the condensing lens. The crosstalk and coupling efficiency values are much worse than the results of the example. The light emitted from the light emitting element has a very poor fiber coupling efficiency because the light emitting element is not disposed in front of the condensing lens.

  On the other hand, according to the embodiment of the present invention, by using the condensing lens effect on the reflection side of the prism having the shape as shown in the figure, it is possible to suppress the spread of light and transmit and receive light. The coupling efficiency has been improved, and the occurrence of far-end crosstalk has been significantly reduced by using an optical isolator. In addition, the light receiving element or the light emitting element is arranged without shifting the prism surface in the axial direction with respect to the front surface of the condensing lens, thereby realizing a bidirectional optical module having high reliability.

The optical component used for the bidirectional | two-way optical module of this invention is shown, (a) is a front view, (b) is a side view. It is sectional drawing which shows the bidirectional | two-way optical module of this invention. It is sectional drawing which shows the bidirectional | two-way optical module of this invention. It is sectional drawing which shows the bidirectional | two-way optical module of this invention. The conventional bidirectional optical module is shown, (a) is sectional drawing which shows a receiving side, (b) is a transmission side.

Explanation of symbols

11, 62 Prism 11a, 11b, 11c, 11d, 11e, 62a, 62b, 62c, 62d, 62e Surfaces 12, 13, 14, 15, 63, 64, 65, 66 Condensing lenses 15a, 15a1, 31 Received light 15aa Reflected light 16a, 32, 33 Transmitted light 21 Fiber 21a Optical fiber shaft 21b End face 22 of optical fiber Light receiving element 22a, 23a Element surface 23 Light emitting element 40, 60 Optical component 55 Optical isolator 62f Corner portion α ₁ , α ₂ , β ₁ , β ₂ tilt angle

Claims (7)

In a bidirectional module that has one optical fiber, a light receiving element and a light emitting element, and an optical component that collects and reflects an optical signal, and performs transmission and reception through the one optical fiber,
The optical component includes a first surface facing the end surface of the optical fiber, a second surface adjacent to the first surface and facing the light receiving element, facing the second surface, and A third surface adjacent to the first surface and facing the light emitting element; a fourth surface that reflects the incoming light incident from the first surface toward the second surface; And a fifth surface that reflects the transmission light incident from the third surface toward the first surface, and forms a pentagonal cross section.
A condensing lens for condensing the received light is integrally formed on the first surface and the second surface of the optical component, respectively, and the transmission light is condensed on the first surface and the third surface, respectively. A condensing lens is integrally formed,
A bidirectional optical module, wherein an optical isolator is disposed between the second surface of the optical component and the light receiving element, and between the third surface of the optical component and the light emitting element. 2. The bidirectional optical module according to claim 1, wherein the fourth surface and the fifth surface of the optical component each have an angle of 45 ° or less with respect to the axial direction of the optical fiber. 3. The bidirectional optical module according to claim 1, wherein a lens for condensing the transmission light and a lens for condensing the reception light are formed on the first surface of the optical component. . 4. The bidirectional optical module according to claim 3, wherein a radius of the lens for condensing the transmission light is different from that of the lens for condensing the reception light. The total reflection dielectric thin film made of at least one of Al, Au, SiO, MgF ₂ , TiO ₂ , and SiO ₂ is provided on the fourth surface and the fifth surface of the optical component. The bidirectional optical module according to any one of? 6. The bidirectional optical module according to claim 5, wherein the total reflection dielectric thin film has a thickness of 1 nm to 100 nm. The bidirectional optical module according to any one of claims 1 to 6, wherein the fourth surface and the fifth surface of the optical component have spherical or aspheric curved surfaces, respectively.

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