JP2013045092A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module which is suitable for miniaturization.SOLUTION: In an optical module 10, a first light emitting device 14 and a photoreceiver 16 are disposed so as to face each other at a side face of a housing 12, and a second light emitting device 18 and an optic fiber 15 are disposed so as to face each other. Inside of the housing, a first optical filter 22, a second optical filter 26 and an optical isolator 14 are contained. By inclining an optical axis connecting the optical fiber and a second light emitter 18b ideally to a direction of a second side 12b with a slant polished optic fiber, the first light emitting device can be penetrated into the housing, the second light emitting device can be approached to a side face in which a photo detector is formed and a dimension of a lateral direction of the optical module can be reduced.

Description

  The present invention relates to an optical module used in, for example, an optical communication system.

  Patent Document 1 discloses an optical module for bidirectional optical communication. A light emitting element, a light receiving element, and an optical fiber are attached to the casing of the optical module.

JP 2008-209266 A

  The optical module disclosed in Patent Document 1 has been insufficiently miniaturized.

  SUMMARY An advantage of some aspects of the invention is that it provides an optical module suitable for miniaturization.

  An optical module according to the present invention includes a housing formed such that the first side surface and the second side surface face each other, and the third side surface and the fourth side surface face each other while connecting the first side surface and the second side surface, The first condensing lens and the first light emitting element are provided, and the first condensing lens is provided inside the housing so that the first condensing lens enters the housing from the first side surface. A first light-emitting device, a light-receiving condensing lens and a light-receiving element, a light-receiving device provided on the second side surface, and an optical fiber provided on the third side surface for transmitting optical signals bidirectionally A second light emitting device having a second condensing lens and a second light emitting element, the fourth light emitting device being provided on the second side surface of the fourth side surface from an intermediate position between the first side surface and the second side surface; Second transmission light reflected from the first light-emitting element and incident on the end face of the optical fiber after being reflected from the first light-emitting element. A first optical filter provided in the casing so as to be transmitted and incident on the end face of the optical fiber; and provided between the first optical filter and the optical fiber in the casing; And a second optical filter that transmits the second transmission light and enters the end face of the optical fiber, reflects the reception light from the optical fiber and enters the light receiving element, and the first optical filter in the housing. An optical isolator that is provided between the optical filter and the second optical filter, and that blocks the component that returns to the first light emitting element and the second light emitting element of the first transmission light and the second transmission light. It is characterized by having.

  According to the present invention, since the optical axis is adjusted so that the light emitting device enters the housing, an optical module suitable for downsizing can be provided.

It is a figure which shows the whole system containing the optical module which concerns on Embodiment 1 of this invention. It is a figure which shows the optical module which concerns on Embodiment 1 of this invention. It is a figure which shows operation | movement of the optical module which concerns on Embodiment 1 of this invention. It is a figure which shows the optical module of a comparative example. It is a figure which shows the optical module which concerns on Embodiment 2 of this invention. It is a figure which shows the optical module which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an entire system including an optical module according to Embodiment 1 of the present invention. The optical module 10 is a part of a 10 G-EPON (10 Gigabit-Ethernet Passive Optical Network) system. The 10G-EPON system consists of a station-side optical circuit terminator (OLT) installed in a station building, an optical branch line connecting the OLT and each subscriber house, and a subscriber side installed in the subscriber house. An optical circuit unit (ONU) is provided.

  The 10G-EPON system transmits data at transmission rates of 1 Gbps and 10 Gbps in both directions (ONU to OLT) and downlink (OLT to ONU). This bidirectional communication is performed by wavelength multiplexing a total of four wavelengths of signals set for each transmission rate and transmission direction using a single optical fiber.

  The OLT includes an optical module 10 (triplexer) to realize the above-described bidirectional communication. The optical module 10 is mounted on a transceiver conforming to a specification such as XFP (10 Gigabit Small Form-actor Pluggable).

  FIG. 2 is a diagram showing the optical module according to Embodiment 1 of the present invention. The optical module 10 combines a light emitting element for transmitting a 1 Gbps downstream signal, a light emitting element for transmitting a 10 Gbps downstream signal, and a light receiving element capable of receiving both 1 Gbps and 10 Gbps signals into a single optical fiber. It is a thing. Hereinafter, the optical module 10 will be described in detail.

  The optical module 10 includes a housing 12. In FIG. 1, only the outline of the housing 12 is shown. The housing 12 includes a first side surface 12a, a second side surface 12b, a third side surface 12c, and a fourth side surface 12d. The first side surface 12a and the second side surface 12b are opposed to each other. The third side surface 12c and the fourth side surface 12d face each other while connecting the first side surface 12a and the second side surface 12b.

  A first light emitting device 14 is provided on the first side surface 12a. The first light emitting device 14 includes a first condenser lens 14a and a first light emitting element 14b formed of a laser diode. The first condenser lens 14 a is located inside the housing 12. Accordingly, the first light emitting device 14 enters the inside of the housing 12 by the distance L from the first side surface 12a.

  A light receiving device 16 is provided on the second side surface 12b. The light receiving device 16 includes a light receiving condensing lens 16a and a light receiving element 16b formed of a photodiode. The light receiving condensing lens 16a is provided along the second side surface 12b.

  An optical fiber 15 is provided on the third side surface 12c. The end face of the optical fiber 15 is obliquely polished so as to be inclined by about 6 to 8 degrees with respect to the light propagation direction in the fiber core (region where light is confined inside the fiber). By the way, when the end face of the optical fiber is perpendicular to the light propagation direction in the fiber core, the light transmitted from the subscriber side is reflected by the end face and returns to the subscriber side again, and the standard of return loss (OLT) Will not be able to satisfy the standard (which must not reflect a certain amount of light) on the ONU. In order to prevent this, the end face of the optical fiber 15 is obliquely polished. When the end surface of the optical fiber 15 is obliquely polished by 6 to 8 degrees, the optical axis optimally coupled to the optical fiber 15 is inclined by 3 to 4 degrees with respect to the light propagation direction of the fiber core from Snell's law.

  A second light emitting device 18 is provided on the fourth side surface 12d. The second light emitting device 18 includes a second condenser lens 18a and a second light emitting element 18b formed of a laser diode. The second light emitting device 18 is provided on the second side surface 12b side of the fourth side surface 12d. That is, the second light emitting device 18 is provided on the second side surface 12b side from the intermediate position between the first side surface 12a and the second side surface 12b on the fourth side surface 12d. The reason why the second light emitting device 18 is provided on the second side surface 12b side is to tilt the optical axis for optimally coupling the optical fiber 15 and the second light emitting element 18b toward the second side surface 12b.

  Each of the first light-emitting element 14b, the light-receiving element 16b, and the second light-emitting element 18b forms a converging optical system via one condenser lens and is coupled to the optical fiber 15. As shown in FIG. 2, the direction parallel to the first side surface 12a and the second side surface 12b is referred to as a “longitudinal direction”. A direction perpendicular to the longitudinal direction and parallel to the third side surface 12c and the fourth side surface 12d is referred to as a “short direction”.

  Inside the housing 12, a first optical filter 22, an optical isolator 24, and a second optical filter 26 are provided. The second optical filter 26 is provided between the first optical filter 22 and the optical fiber 15. The optical isolator 24 is provided between the first optical filter 22 and the second optical filter 26.

  The first optical filter 22 and the second optical filter 26 guide the light emitted from the first light emitting element 14 b or the second light emitting element 18 b so as to be coupled to the optical fiber 15. The second optical filter 26 guides received light to the light receiving element 16b. The optical isolator 24 is provided so that the light emitted from the first light emitting element 14b and the second light emitting element 18b does not return to these.

  The optimum input wavelength of the optical isolator 24 is optimized to an intermediate temperature between the maximum value and the minimum value of the operating temperature range of the optical module 10, and is intermediate between the emission wavelength of the first light emitting element 14b and the emission wavelength of the second light emitting element 18b. Is set to the value of The operating temperature range of the optical module 10 according to Embodiment 1 of the present invention is 0 ° C. to 80 ° C. Therefore, the optimum input wavelength of the optical isolator 24 is optimized to 40 ° C., and is set to an intermediate value between the emission wavelength of the first light emitting element 14b and the emission wavelength of the second light emitting element 18b.

  FIG. 3 is a diagram illustrating the operation of the optical module according to Embodiment 1 of the present invention. The first optical filter 22 reflects the first transmission light emitted from the first light emitting element 14b to enter the end face of the optical fiber 15, and transmits the second transmission light emitted from the second light emitting element 18b to transmit the optical fiber. 15 is incident on the end face. The second optical filter 26 transmits the first transmission light and the second transmission light to be incident on the end face of the optical fiber 15, and reflects the reception light from the optical fiber 15 to be incident on the light receiving element 16b. The optical isolator 24 blocks a component (referred to as return light) that returns to the first light emitting element 14b and the second light emitting element 18b from the first transmission light and the second transmission light.

  With the configuration as described above, the first transmission light emitted from the first light emitting element 14b is collected by the condenser lens 14a, then reflected by the first optical filter 22, and passed through the optical isolator 24 and the second optical filter 26. The light passes through and enters the end face of the optical fiber 15. The second transmission light emitted from the second light emitting element 18 b is collected by the condenser lens 18 a, and then passes through the first optical filter 22, the optical isolator 24, and the second optical filter 26 and enters the end face of the optical fiber 15. To do. The received light from the optical fiber 15 is reflected by the second optical filter 26, collected by the condenser lens 18a, and incident on the light receiving surface of the light receiving element 16b.

  By the way, the optical fiber 15 is obliquely polished, and the optical axis that optimally couples the optical fiber 15 and the second light emitting element 18b is inclined in the direction of the second side face 12b. In FIG. 3, a broken line parallel to the second side surface 12b is drawn to make this inclination easy to understand.

  Prior to the description of the characteristics of the optical module according to Embodiment 1 of the present invention, a comparative example will be described in order to clarify its significance. FIG. 4 is a diagram illustrating an optical module of a comparative example. The optical module 100 of the comparative example includes an optical fiber 104. The end face of the optical fiber 104 is formed perpendicular to the light propagation direction in the fiber core. The optical axis that optimally couples the optical fiber 104 and the second light emitting element 18b extends in a direction parallel to the second side surface 12b.

  The optical module 100 of the comparative example includes an optical isolator 106 in the immediate vicinity of the first condenser lens 14a. An optical isolator 108 is provided in the immediate vicinity of the second condenser lens 18a. Thereby, the first transmission light passes through the optical isolator 106 before entering the first optical filter 22. The second transmitted light passes through the optical isolator 108 before entering the first optical filter 22.

  In the optical module 100 of the comparative example, since the optical axis that optimally couples the optical fiber 104 and the second light emitting element 18b extends in a direction parallel to the second side surface 12b, the first optical filter 22 and the second optical filter 26 are a casing. It is arranged in the center in the short direction. In addition, two optical isolators are required. Due to these factors, it is difficult to downsize the optical module 100 of the comparative example. In particular, when the optical module is mounted on an XFP-sized transceiver, it is difficult to satisfy the dimensional constraints in the short direction of the optical module.

  However, in the optical module 10 according to Embodiment 1 of the present invention, the optical axis that optimally couples the optical fiber 15 and the second light emitting element 18b is inclined in the direction of the second side surface 12b. The first optical filter 22, the optical isolator 24, and the second optical filter that are provided on the second side surface 12b can be disposed close to the second side surface 12b. When the first optical filter 22, the optical isolator 24, and the second optical filter 26 are arranged close to the second side surface 12b, the optimal arrangement position of the first light emitting device 14 (the position where the coupling with the optical fiber 15 is optimal). Also approaches the second side surface 12b side. Accordingly, the first light emitting device 14 can be made to enter the inside of the housing 12 by the distance L, so that the size of the optical module 10 in the short direction can be shortened.

  When the first light-emitting element and the light-receiving element are arranged on one side surface, the first light-emitting element and the light-receiving element must be sufficiently spaced to suppress mutual interference. Therefore, it is necessary to increase the longitudinal dimension of the housing. However, according to the optical module 10 according to the first embodiment of the present invention, the first light emitting element 14b is fixed to the first side surface 12a, and the light receiving element 16b is fixed to the second side surface 12b. Is provided. Therefore, the longitudinal dimension of the optical module can be shortened while ensuring a sufficient distance between the first light emitting element 14b and the light receiving element 16b. If the length in the longitudinal direction is shortened, the distance between the second condenser lens 18a and the optical fiber 15 can be shortened. Therefore, the coupling magnification changes due to fluctuations in operating temperature by reducing the imaging magnification of the condenser lens 18a (tracking error). Can be reduced.

  If the optical isolator is disposed in the immediate vicinity of the light emitting element as in the comparative example, an optical isolator having a large light receiving diameter is required to prevent optical vignetting, which is disadvantageous for miniaturization of the optical module. The optical isolator is desirably disposed in the vicinity of the optical fiber 15 where the spot diameter of the transmission signal light is further reduced. According to the optical module 10 according to Embodiment 1 of the present invention, since the optical isolator 24 is disposed between the first optical filter 22 and the second optical filter 26, the optical isolator 24 can be disposed in the vicinity of the optical fiber 15. Therefore, the optical isolator 24 can be reduced in size and cost.

  By the way, in order to suppress the above-mentioned return light, it is desirable to suppress a change in the optimum input wavelength of the optical isolator. However, the optimum input wavelength of the optical isolator is temperature dependent. That is, the optimum input wavelength of the optical isolator changes in proportion to the temperature change amount of the optical module. Therefore, for example, when the optimum input wavelength of the optical isolator is optimized to “10 ° C.” and set to an intermediate value between the emission wavelength of the first light emitting element 14 b and the emission wavelength of the second light emitting element 18 b, The change in the optimum input wavelength of the optical isolator is small, but at 80 ° C., it becomes very large.

  Therefore, the optimum input wavelength of the optical isolator 24 is optimized to an intermediate temperature (40 ° C.) between the maximum value and the minimum value of the operating temperature range of the optical module 10, and the emission wavelength of the first light emitting element 14b and the second light emitting element 18b. An intermediate value of the emission wavelength was set. Therefore, even when the temperature of the optical module becomes 0 ° C. or 80 ° C., it is possible to avoid the change in the optimum input wavelength of the optical isolator from becoming large. In this way, the component (return light) that returns to the first light-emitting element 14b and the second light-emitting element 18b in the first transmission light and the second transmission light is attenuated by one optical isolator 24 while suppressing the change in the optimum input wavelength. be able to. The attenuation of the return light needs to satisfy the standard of relative intensity noise.

  The optical module according to Embodiment 1 of the present invention can be variously modified. For example, the operating temperature range of the optical module 10 is not limited to 0 ° C. to 80 ° C.

Embodiment 2. FIG.
FIG. 5 is a diagram illustrating an optical module according to Embodiment 2 of the present invention. The optical module according to Embodiment 2 of the present invention has much in common with the optical module according to Embodiment 1 described above. Therefore, the difference from the optical module according to Embodiment 1 described above will be mainly described.

  A first optical filter 50 is fixed on the fourth side surface 12 d side of the optical isolator 24. On the other hand, the second optical filter 52 is fixed to the third side surface 12 c side of the optical isolator 24. The first optical filter 50, the optical isolator 24, and the second optical filter 52 are integrated so as to form one component 54.

  According to the optical module according to the second embodiment of the present invention, the configuration of the first optical filter 50, the optical isolator 24, and the second optical filter 52 can be simplified by using one component 54. Can be downsized. Note that the optical module according to Embodiment 2 of the present invention can be modified at least as much as the optical module according to Embodiment 1.

Embodiment 3 FIG.
FIG. 6 is a diagram illustrating an optical module according to Embodiment 3 of the present invention. The optical module according to Embodiment 3 of the present invention has much in common with the optical module according to Embodiment 2 described above. Therefore, the difference from the optical module according to the second embodiment will be mainly described.

  The first optical filter 62 and the second optical filter 64 are fixed to the optical isolator 60 to form one component 66. The surface of the second optical filter 64 opposite to the surface fixed to the optical isolator 60 is fixed to the end surface of the optical fiber 15.

  The spot diameters of the first transmission light and the second transmission light are narrowed toward the optical fiber 15. Therefore, the optical isolator 60 can be made smaller as it is closer to the optical fiber 15. According to the optical module according to Embodiment 3 of the present invention, the optical isolator 60 can be reduced in size because the optical isolator 60 is brought close to the optical fiber 15 by bringing the component 66 into contact with the end face of the optical fiber 15. The optical module according to Embodiment 3 of the present invention can be modified at least as much as the optical module according to Embodiment 1.

  DESCRIPTION OF SYMBOLS 10 Optical module, 12 Housing | casing, 14 1st light-emitting device, 14a 1st condensing lens, 14b 1st light-emitting element, 15 Optical fiber, 16 Light-receiving device, 16a Condensing lens for light reception, 16b Light-receiving element, 18 2nd light emission Device, 18a second condenser lens, 18b second light emitting element, 22 first optical filter, 24 optical isolator, 26 second optical filter

Claims (5)

A housing formed such that the first side surface and the second side surface face each other, and the third side surface and the fourth side surface face each other while connecting the first side surface and the second side surface;
A first condensing lens and a first light emitting element, wherein the first condensing lens is located inside the housing, and is provided so as to enter the housing from the first side surface; A first light emitting device;
A light receiving device having a light receiving condensing lens and a light receiving element, provided on the second side surface;
An optical fiber provided on the third side surface for transmitting an optical signal bidirectionally;
A second light-emitting device having a second condenser lens and a second light-emitting element, the fourth light-emitting device being provided on the second side surface from an intermediate position between the first side surface and the second side surface on the fourth side surface;
The first transmission light emitted from the first light emitting element is reflected and incident on the end face of the optical fiber, and the second transmission light emitted from the second light emitting element is transmitted and incident on the end face of the optical fiber. A first optical filter provided in the housing;
Received light from the optical fiber that is provided between the first optical filter and the optical fiber in the housing, transmits the first transmission light and the second transmission light, and enters the end surface of the optical fiber. A second optical filter that reflects the light and makes it incident on the light receiving element;
A component that is provided between the first optical filter and the second optical filter in the casing and returns to the first light emitting element and the second light emitting element among the first transmission light and the second transmission light. An optical module comprising: an optical isolator that blocks light.   The optimum input wavelength of the optical isolator is optimized to an intermediate temperature between the maximum value and the minimum value of the operating temperature range of the optical module, and is intermediate between the emission wavelength of the first light emitting element and the emission wavelength of the second light emitting element. The optical module according to claim 1, wherein the optical module is set to a value of   The optical module according to claim 1, wherein an end face of the optical fiber is obliquely polished.   The first optical filter is fixed to the fourth side surface of the optical isolator, and the second optical filter is fixed to the third side surface of the optical isolator, so that the first optical filter, The optical module according to any one of claims 1 to 3, wherein an optical isolator and the second optical filter are integrated.   The optical module according to claim 4, wherein a surface of the second optical filter opposite to a surface fixed to the optical isolator is fixed to an end surface of the optical fiber.

Images