JP2012237840A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module in which a unit assembly and an optical receptacle are electrically insulated at a clearance and securely mounted and fixed to a stub without increasing external dimensions.SOLUTION: An optical module includes a unit assembly 12 having a metallic assembly housing 20 and a bush 16, and mounted with a plurality of optical element units 21-23; and an optical receptacle 11 having a metallic shell 18 and a sleeve holder 15, and in which a ferrule of an optical connector is inserted. In an electric insulation stub 13, the sleeve holder 15 and the bush 16 are pressed and fitted in at a clearance 14 which is electrically insulated. Insulation resin 19 is filled in the clearance 14. The insulation resin 19 is filled in a clearance which is regulated by at least either one of a projecting stepped portion having a diameter smaller than an outer diameter of the sleeve holder 15 or a projecting stepped portion having a diameter smaller than an outer diameter of the bush 16.

Description

  The present invention relates to an optical module including an optical element unit on which a photoelectric conversion element is mounted and an optical receptacle into which a ferrule of an optical connector is inserted.

  An optical module mounted on an optical transceiver or the like used for optical communication includes a photoelectric conversion element (hereinafter referred to as an optical element) such as a light emitting element or a light receiving element, and an optical element unit (or an optical element unit) on which these optical elements are mounted (or And an optical receptacle for positioning an optical connector ferrule connected to the optical fiber cable to form an optical optical coupling with the optical element.

  The optical element unit is configured, for example, by enclosing a stem having a lead terminal for transmitting an electric signal, which is mounted with an electronic component such as an optical element, with a metal casing or the like. The metal housing is welded to the stem by resistance welding or the like, for example, and the storage space for the electronic component mounted on the stem is sealed in an airtight state, thereby improving the reliability of the electronic component. Further, an optical lens or the like for condensing the propagated light is attached and fixed to the housing.

The optical receptacle is aligned and fixed with respect to the optical element unit so that the light condensed by the optical lens is in a position where it is optically coupled with high efficiency. The optical receptacle may be positioned using a joint sleeve or not.
When the optical module having the above structure is mounted on an optical transceiver or the like, it is positioned and fixed in a predetermined storage portion.

  When the frequency of use of the optical transceiver is increased, electrical noise radiated from the optical module, electrical noise radiated from the circuit board at the rear stage of the optical element unit, and electrical noise propagated from the outside and invaded become a problem. . Usually, in order to suppress these electrical noises, the optical receptacle of the optical module has a structure shielded with a metal material or a metal coating in order to suppress the emission and penetration of electrical noise.

  This shield made of a metal material is grounded (referred to as a frame ground) via a housing or the like of a communication device, and is designed to suppress the influence of static electricity in addition to the suppression of electrical noise. On the other hand, the ground of the signal circuit that controls and drives the optical elements of the optical module (referred to as signal ground) is connected to the ground conductor provided on the circuit board via the stem and ground pins of the optical element unit. Designed to be.

  When the frame ground and the signal ground are electrically connected, electrical noise is likely to propagate between the device housing and the circuit board, which may adversely affect the operation of the device. In addition, static electricity from the device casing is easily propagated to the circuit board side, which causes a surge breakdown of the circuit portion. Therefore, a structure in which the frame ground and the signal ground are electrically separated is required in the optical module.

  For example, in Patent Document 1 and Patent Document 2, as shown in FIGS. 3A and 3B, an optical receptacle 1 to which an external optical fiber is connected and an optical element unit 2 on which the optical element is mounted are described as stub ferrules. 3 discloses an optical module having an electrically insulating structure. In this optical module, an annular groove 4a (FIG. 3A) or a V-shaped groove 4b (FIG. 3B) is provided in an electrically insulating stub ferrule 3, and an optical receptacle is provided at one end of the grooves 4a and 4b. The metal holder 5 on the 1 side is press-fitted and the metal holder 6 on the optical element unit 2 side is press-fitted to the other end. The concave grooves 4a and 4b prevent conduction caused by press-fitted metal marks or the like of the holders 5 and 6 so that electrical insulation between the holders 5 and 6 can be secured.

JP 2007-133225 A JP 2009-58555 A

According to the configuration shown in FIG. 3, the optical element unit on which the optical element is mounted and the optical receptacle to which the optical connector is connected are electrically insulated by the electrically insulating stub ferrule. Thereby, propagation of electrical noise and surge breakdown due to static electricity can be prevented, and the metal portion of the optical receptacle can be prevented from acting as an antenna.
However, in Patent Documents 1 and 2, it is a single optical element unit in which either a light receiving element or a light emitting element is mounted on an optical receptacle, and the optical element unit has a small shape with a relatively small mass. Is.

  On the other hand, with the advancement of optical communication technology, an optical access system represented by FTTH (Fiber To The Home) uses an optical module that performs two-way communication with one optical fiber. In this case, the optical module includes, for example, three optical element units including two transmitting optical element units on which light emitting elements having different wavelengths are mounted and one receiving optical element unit on which a light receiving element is mounted. Unit aggregates are used. This unit aggregate has a large mass and a large shape. In addition, the unit assembly and the optical receptacle need to be optically coupled with high accuracy without deviation in the optical axis. For this purpose, the fixing strength (impact resistance) of the unit assembly and the optical receptacle is attached. Etc.) must be secured.

  The unit assembly and the optical receptacle are assembled and fixed to the stub (stub ferrule) by press-fitting, but in conventional optical modules consisting of small-sized optical element units with small mass, the press-fitting Even if the length is sufficient, there is a possibility that sufficient fixing strength cannot be obtained in an optical module composed of a unit assembly on which a plurality of optical element units are mounted. For this reason, the optical coupling state may fluctuate due to the moment caused by the impact. On the other hand, a method of increasing the above press-fitting fitting length is conceivable, but this method increases the outer dimensions of the optical module, and there is a problem that it becomes impossible to meet the requirements of miniaturization and industry standards. is there.

  The present invention has been made in view of the above-described situation, and the unit assembly and the optical receptacle are electrically insulated through the gap and firmly attached and fixed to the stub without increasing the outer dimension. The purpose is to provide an optical module.

An optical module according to the present invention includes a unit assembly in which a plurality of optical element units are mounted having a metal collective housing and a bush, and a ferrule of an optical connector having a metal shell and a sleeve holder. An optical module comprising an optical receptacle, wherein a sleeve holder and a bush are press-fitted into an electrically insulating stub with a gap that is electrically insulated, and the gap is filled with an insulating resin. It is characterized by being.
The insulating resin is filled in a gap regulated by at least one convex step portion having a diameter smaller than the outer diameter of the sleeve holder or a convex step portion having a diameter smaller than the outer diameter of the bush. Is preferred.

  According to the optical module of the present invention, even in an optical module including a plurality of optical element units, the unit assembly and the optical receptacle are electrically insulated without increasing the external dimensions of the optical module, and sufficient impact is achieved. It can be mounted and fixed with a fixed strength having resistance.

It is a figure explaining an example of the optical module by this invention. It is a figure explaining the electrical insulation part of the unit assembly and optical receptacle by this invention. It is a figure explaining a prior art.

  Embodiments of the present invention will be described with reference to the drawings. In the figure, 10 is an optical module, 11 is an optical receptacle, 12 is a unit assembly, 13 is a stub, 13a is an optical fiber, 13b is an inner end of the stub, 14 is a gap, 15 is a sleeve holder, 15a is a press-fitting hole, 15b is Convex step portion, 16 is a bush, 16a is a press-fitting hole, 16b is a convex step portion, 17 is a sleeve, 18 is a metal, 19 is an insulating resin, 20 is a collective housing, 21 and 22 are optical element units for transmission, 23 Indicates an optical element unit for reception.

  The optical module 10 of the present invention is intended for an optical module having an optical receptacle 11 and a unit assembly 12 including a plurality of optical element units as shown in FIG. The optical receptacle 11 and the unit assembly 12 are formed by a stub 13 (also referred to as a stub ferrule) that optically couples an optical fiber inserted on the optical receptacle 11 side and an optical element on the unit assembly 12 side. It is intended for a structure that is connected and integrated.

  The optical receptacle 11 protects the sleeve 17 by being held by the sleeve 17 into which the ferrule is inserted, the stub 13 into which the base end portion of the sleeve is fitted, the sleeve holder 15 press-fitted into the stub, and the sleeve holder. The metal shell 18 is made up of. The sleeve 17 is formed of, for example, a ceramic material such as zirconia, and is formed of a split sleeve that can be slit and expanded and contracted in the radial direction. The sleeve 17 has a function of positioning the ferrule and facilitating its attachment and detachment, and is elastically fitted to one end of the stub 13 and held.

  The sleeve holder 15 is made of metal, has a press-fitting hole 15a, and is fixed to the stub 13 by press-fitting. The sleeve holder 15 has a function of holding the sleeve 17 and the metal shell 18 in a predetermined position, and supporting and fixing the optical module by being coupled to a frame or the like of the mounted device to perform electromagnetic shielding. The metal shell 18 protects the sleeve 17 from an external force, performs an electromagnetic shield, and is pressed into the sleeve holder 15 to be integrated.

  For example, three optical element units are assembled in the unit assembly 12 using a metal assembly case 20. The first optical element unit 21 is an optical element unit for transmission of 10 Gbps (wavelength 1577 nm) using, for example, an EML element (Electro-absorption Modulator Integrated Laser Diode) as a light emitting element. . The second optical element unit 22 is an optical element unit for transmission of 1 Gbps (wavelength 1490 nm) using, for example, a DML element (Direct Modulation Laser Diode) as a light emitting element. The third optical element unit 23 is an optical element unit for reception using a light receiving element of 10 Gbps (wavelength 1270 nm) or 1 Gbps (wavelength 1310 nm), for example.

  The three optical element units 21, 22, and 23 are optically coupled to the optical fiber 13a of the stub 13 using an optical isolator, a wavelength demultiplexing filter, a condenser lens, and the like. In the optical element units 21 and 22 for transmission using a light emitting element such as a laser, this optical coupling is performed by using a joint sleeve or the like for alignment and then welding to the collective housing 20 with a YAG laser or an adhesive. Fixed. Further, the receiving optical element unit 23 is aligned without using a joint sleeve (a joint sleeve may be used) and fixed to the collective housing 20 by welding with a YAG laser or an adhesive.

  The collective housing 20 is positioned in contact with a metal bush 16 that is press-fitted into the stub 13 in advance, and is fixedly attached to the bush 16 by welding a portion indicated by X with a YAG laser or the like. By fixing the collective housing 20 to the bush 16, the lower end of the stub 13 (the optical coupling end of the optical fiber 13 a) and the optical elements of the optical element units 21 to 23 are optically optically coupled.

  The stub 13 is formed of a material having electrical insulation, and can be formed of a ceramic material such as zirconia, similar to the sleeve 17 of the optical receptacle 11. A short optical fiber 13 a is disposed at the center of the stub 13. The optical fiber 13 a optically couples the optical fiber of the optical connector positioned by the sleeve 17 and the optical element on the unit assembly 12 side. In addition to optically coupling the optical receptacle 11 and the unit assembly 12 as described above, the stub 13 also has a function as a member that is mechanically connected and integrated.

The sleeve holder 15 of the optical receptacle 11 and the bush 16 of the unit assembly 12 are press-fitted into the stub 13 with a gap 14 that is electrically insulated, and are attached to the stub 13 so as not to be electrically connected to each other. Fixed.
In the present invention, in particular, the insulating resin 19 is filled in the gap 14 to increase the press-fitting length of the sleeve holder 15 and the bush 16 with respect to the stub 13. With this configuration, it is possible to increase the fixing strength of the unit assembly 12 including the optical receptacle 11 and the plurality of optical element units, and it is possible to suppress the fluctuation of the optical coupling state due to an impact or the like.

  FIG. 2 is a partially enlarged view for explaining an electrically insulating portion between the optical receptacle 11 and the unit assembly 12. FIG. 2 (A) is a cross-sectional view, and FIG. 2 (B) and FIG. It is a figure to do.

  As shown in FIG. 2A, the sleeve holder 15 is fixed to the stub 13 by press-fitting through the press-fitting hole 15a, and the bush 16 is fixed to the stub 13 by press-fitting through the press-fitting hole 16a. The The sleeve holder 15 and the bush 16 are fixed while holding a predetermined gap 14 that is electrically insulated. The protruding amount of the inner end 13b of the stub 13 protruding from the bush 16 is controlled and regulated by a jig or the like.

  The gap 14 is filled with a heat-resistant thermosetting insulating resin (for example, epoxy resin) 19 and cured to be integrated with the stub 13. By filling the gap 14 with the insulating resin 19, even when a moment due to impact is applied to the bush 16, stress is applied to the sleeve holder 15 via the insulating resin 19, and the bush 16 and the sleeve holder 15 are integrated. It becomes. For this reason, it is equivalent to making the outer dimensions of the optical modules the same and substantially increasing the press-fitting length of the sleeve holder 15 and the bush 16 and effectively suppressing the occurrence of displacement due to impact or the like. be able to.

  Further, a convex step portion 15b having a smaller diameter than the outer diameter of the sleeve holder is provided on the gap forming side of the sleeve holder 15, and a convex step portion 16b having a smaller diameter than the outer diameter of the bush is also provided on the gap forming side of the bush 16. The electrically insulating gap 14 is formed between the small-diameter convex steps 15b and 16b, and an insulating resin 19 is filled in the gap regulated by the convex steps. For this reason, it is possible to manage the filling so that the insulating resin 19 does not protrude outward from the convex steps 15b and 16b.

  As shown in FIG. 2B, the unit housing 20 of the unit assembly is welded by a YAG laser or the like at a portion indicated by X on the outer periphery of the bush 16. Since the insulating resin 19 is formed with an outer diameter regulated by the small-diameter convex step portions 15b and 16b formed inside the outer diameter of the bush 16, it becomes a shadow of the bush 16 and is not easily affected by welding. It becomes. As a result, it is possible to suppress the insulation resin from deteriorating due to the quality change of the insulating resin and the splash during welding.

  As shown in FIG. 2 (C), the protruding step portions 15b and 16b are not provided on both the sleeve holder 15 and the bush 16, but are only provided on one side to restrict filling of the insulating resin 19. can do. In this case, the convex step 16a on the bush 16 side is omitted, and only the convex step 15b on the sleeve holder 15 side is used, so that it is not easily affected by welding by the YAG laser as in the case of FIG. can do.

  In the optical module shown in FIG. 1, when the bushing press-fitting length was 0.84 mm and the transmission loss after applying an impact of 500 G without using an insulating resin was measured, the loss increased by 0 to 3 dB. was there. When the loss after applying an impact of acceleration 500G was measured without using an insulating resin with the press-fitting length of the bushing set to 1.4 mm, there was a loss increase of 0 to 1.5 dB. That is, even if the impact resistance can be improved somewhat by increasing the press-fitting length of the bush, it is not sufficient.

On the other hand, when the press-fitting length of the bush was 0.84 mm, the gap was filled and hardened with insulating resin, and the loss after applying an impact of 500 G acceleration was measured, the loss increased by less than 0.5 dB. It was.
From the result of the impact test, it was confirmed that it is more effective for impact resistance to leave the press-fit fitting length as it is and to fill the gap with resin than to increase the press-fit length of the bush.

DESCRIPTION OF SYMBOLS 10 ... Optical module, 11 ... Optical receptacle, 12 ... Unit assembly, 13 ... Stub, 13a ... Optical fiber, 13b ... Inner end of stub, 14 ... Gap, 15 ... Sleeve holder, 15a ... Press-fit hole, 15b ... Convex step , 16 ... bush, 16a ... press-fitting hole, 16b ... convex step part, 17 ... sleeve, 18 ... metal shell, 19 ... insulating resin, 20 ... collective housing, 21, 22 ... optical element unit (for transmission), 23 ... Optical element unit (for reception).

Claims (2)

A unit assembly having a metal collective housing and a bush and mounted with a plurality of optical element units; and an optical receptacle having a metal shell and a sleeve holder into which an optical connector ferrule is inserted. An optical module,
An optical module, wherein the sleeve holder and the bush are press-fitted into an electrically insulating stub with a gap that is electrically insulated, and the gap is filled with an insulating resin.   The insulating resin is filled in the gap regulated by at least one convex step portion having a diameter smaller than the outer diameter of the sleeve holder or a convex step portion having a diameter smaller than the outer diameter of the bush. The optical module according to claim 1.

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