JP2012018291A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module capable of preventing breakage of a lens and ensuring mounting accuracy of the lens when the lens is fixed to an inner hole of a housing, and having a lens fixing structure providing high workability.SOLUTION: A lens holder 3 has a lens holding part 3a for holding an optical lens 2, a press-fit part 3b to be press-fitted into an inner hole, and a connection part 3c for connecting the lens holding part 3a and the press-fit part 3b. The outer diameter of the lens holding part 3a is formed to be smaller than the inner diameter of the inner hole. A gap 4 is formed between the inner hole of a housing 1 and the lens holding part 3a. A groove is formed on the outer periphery of the connection part 3c. When the optical lens 2 is fixed to the lens holder 3, and the lens holder 3 is press-fitted into the inner hole of the housing 1 of a lens mounting unit 10, a stress generated at the time of the press-fitting does not directly act on the optical lens 2. This prevents the breakage of the optical lens.

Description

  The present invention relates to an optical module that transmits and receives optical signals.

  An optical module for transmission used in optical communication uses light from a laser diode (LD) as signal light, and the signal light is collected by a lens and coupled to a communication optical fiber. . The receiving optical module collects the signal light transmitted through the optical fiber with a lens and receives it with a receiving photodiode (PD). There is also a single-fiber bidirectional transmission / reception optical module that performs both transmission and reception using a single optical fiber.

  In the optical module for optical communication described above, when a plurality of signal lights having different wavelengths are multiplexed and transmitted / received using a plurality of transmission LDs and reception PDs, an optical path between an optical element such as an LD or PD and an optical fiber In the system, an optical isolator, a prism, a wavelength demultiplexing filter (hereinafter referred to as “WDM filter”) or the like is arranged. In such an optical module, the optical path length becomes long, and it is difficult to adjust and set the focal position and working distance of the lens.

In connection with this, various proposals have conventionally been made for the lens fixing structure in the optical module.
Usually, when fixing a lens in an optical module, it is bonded and fixed with an adhesive, solder, low-melting glass or the like. Further, for example, Patent Document 1 includes a light receiving and emitting element 103, an optical fiber fixture 104, and an optical coupling lens 102 as shown in FIG. In the optical module in which the holding part 101 is press-fitted and fixed, the contact part of the holding part 101 with the optical coupling lens 102 is a thin part 102a.

  Further, in Patent Document 2, as shown in FIG. 8, an optical module in which an optical semiconductor element 203, an optical fiber stub 204, and at least one spherical lens 202 are coaxially fixed and these three components are optically coupled. The ball lens 202 is fixed to the exterior member 201 of the optical module via an annular press-fit ring 205, and the press-fit ring 205 and the exterior member 201 are fixed by welding.

JP-A-2005-070568 Japanese Patent Laid-Open No. 2-173604

  However, when a quartz lens is used, in the optical module disclosed in Patent Document 1, the optical coupling lens 102 is cracked because the optical coupling lens 102 is directly pressed into contact with the holding component 101. The possibility of cracking remains.

  Further, in the optical module disclosed in Patent Document 2, it is necessary to use a material having a larger elastic coefficient than the exterior member 201 as the material of the press-fitting ring 205 in order to prevent lens cracking. The problem of mounting accuracy due to misalignment remains. In addition, this problem increases the possibility of external stress due to temperature rise or the like. Furthermore, the method of directly fixing the lens to the optical module housing with an adhesive, solder, low melting point glass or the like has a problem that it takes time to fix and the workability is poor.

  The present invention has been made in view of these circumstances, and when fixing the lens to the inner hole of the housing, the lens can be prevented from cracking, the mounting accuracy of the lens can be secured, and the lens excellent in workability. It is an object of the present invention to provide an optical module having a fixing structure.

  An optical module according to the present invention is an optical module in which an optical lens is fixed to a lens holder, and the lens holder is fixed by press-fitting into an inner hole of a housing of a lens mounting unit. The lens holder includes a lens holding portion that holds an optical lens; A press-fitting portion that is press-fitted into the inner hole of the housing, and a connecting portion that connects the lens holding portion and the press-fitting portion, and the outer diameter of the lens holding portion is smaller than the inner diameter of the housing, A gap is formed between the hole and the lens holding portion.

  In the optical module according to the present invention, the lens holder and the housing of the lens mounting unit may be made of the same material, for example, stainless steel. Further, the connecting portion of the lens holder may include a groove having an outer diameter smaller than the outer diameter of the lens holding portion, and the thickness of the lens holder may be minimized in this connecting portion. Furthermore, the thickness of the lens holding portion may be larger than the thickness of the press-fit portion.

  According to the present invention, since the stress to the optical lens during press-fitting can be relaxed with a simple structure, it is possible to prevent the lens from cracking. Further, since the lens holder is fixed to the inner hole of the housing by press-fitting, the mounting accuracy of the lens can be secured and the assembling workability is excellent. Furthermore, it is possible to suppress the variation of the optical axis of the lens due to a change in environmental temperature.

It is the schematic which shows an example of the optical module by this invention. It is a figure which shows the basic structure of the lens mounting unit in the optical module of this invention. It is sectional drawing of the lens mounting unit in the optical module of this invention. It is a figure for demonstrating the fixing structure of the condensing lens in the optical module of this invention. It is a cross-sectional perspective view at the time of fixing the condensing lens in the optical module of this invention to the lens holder. It is a figure which shows the other example of the lens holder in the optical module of this invention. It is a figure which shows an example of the conventional optical module. It is a figure which shows the other example of the conventional optical module.

Hereinafter, preferred embodiments of the optical module of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of an optical module of the present invention, and FIG. 2 is a diagram showing an example of a basic structure of a lens mounting unit in the optical module of the present invention.

  The optical module shown in FIG. 1 has a lens mounting unit 10. This lens mounting unit 10 is employed on an optical line terminal (OLT) side in a system targeting single-core bidirectional optical transmission, and includes first and second transmission devices. 30 and 40 and one receiving device 50 are assembled to the lens mounting unit 10. The condensing lens 2 corresponds to the optical lens of the present invention, and FIG. 2 does not show the fixing structure of the condensing lens 2 to the housing 1 of the lens mounting unit 10.

  In this embodiment, the lens mounting unit 10 has one condenser lens 2 for the first and second transmitting devices 30 and 40 and one receiving device 50. The lens mounting unit 10 forms a condensing optical system with the condensing lens 2 and the fiber (stub end) 20, and the transmitting devices 30 and 40 and the receiving device 50 are the other condensing points of the condensing lens 2. It is fixed in an aligned state.

  The receiving device 50 is above the cut filter 13, the first transmitting device 30 is on the optical axis of the first WDM filter 11, that is, in the direction in which the optical axis of the stub 20 is extended, and the second transmitting device 40 is the second WDM. The optical axis of the filter 12, that is, the optical axis of the stub 20 is attached in a direction bent by 90 ° by the second WDM filter 12.

  FIG. 3 is a cross-sectional view of the lens mounting unit in the optical module of the present invention, and FIG. 4 is a diagram for explaining a fixing structure of the condenser lens. FIG. 5 is a cross-sectional perspective view when the condenser lens is fixed to the lens holder.

  The condenser lens 2 is fixed to the lens holder 3, and the lens holder 3 is press-fitted into the inner hole of the housing 1 of the lens mounting unit 10. Here, the lens holder 3 is formed in a cylindrical shape and has an axis coinciding with the axis of the inner hole of the housing 1. The lens holder 3 includes a lens holding portion 3a for fixing the condenser lens 2, a lens holder press-fitting portion 3b for press-fitting the lens holder 3 itself into the inner hole of the housing 1, and a lens holding portion 3a. It is comprised from the connection part 3c which connects the lens holder press-fit part 3b. Here, the diameter of the lens holder 3 is 3.5 mmφ, the length of the lens holding portion 3 a is about 1.2 mm, and the length of the lens holder press-fitting portion 3 b is 1 mm.

  Here, the inner hole of the housing 1 of the lens mounting unit 10 has a circular cross section, for example, and the outer surface of the lens holder press-fitting portion 3 b of the lens holder 3 also corresponds to the cross section of the inner hole of the housing 1. It is formed in a circular shape so that it can be press-fitted. The outer diameter of the lens holder press-fitting portion 3b is formed to be, for example, about 5 μm larger than the inner diameter of the inner hole of the housing 1.

  Further, the outer surface of the lens holding portion 3a is opposed via a minute gap, for example, about 10 μm so as not to contact the inner surface of the housing 1 when the lens holder 3 is press-fitted into the housing 1. The outer diameter is made smaller than the outer shape of the lens holder press-fitting portion 3b. Here, it is important that the outer diameter of the lens holding portion 3 a is slightly smaller than the inner diameter of the housing 1. When the gap between the two is large, when the lens holder 3 is inserted into the housing 1, the lens holder 3 may be inserted and press-fitted in an inclined state, which is not preferable.

  The condensing lens 2 is made of glass, and as a method for fixing the lens 2 to the lens holding portion 3a of the lens holder 3, an existing technique using an adhesive, solder, low melting point glass, or the like can be used. Further, in order to relieve stress on the condenser lens 2, it is desirable to form the lens holding portion 3a so as to be thicker than the lens holder press-fitting portion 3b.

  In the embodiment shown in FIG. 4, a groove having a depth of about 0.3 mm and a width of about 0.5 mm is provided on the lens holding portion 3a side along the outer periphery of the connecting portion 3c. Thereby, the thickness from the bottom of the groove to the inner hole of the holder press-fit portion 3b can be reduced, and mechanical distortion exerted on the press-fit portion 3b from the housing 1 is applied to the lens via the lens holding portion 3a. It can alleviate being affected.

  In assembling the optical module of the present invention, when the condenser lens 2 is assembled into the inner hole of the housing 1 of the lens holding unit, the condenser lens 2 is first fixed to the lens holding portion 3a of the lens holder 3 by an existing method. Thereafter, the lens holder 3 to which the lens 2 is fixed is pressed into the housing 1. Since the lens holding portion 3a and the lens holder press-fitting portion 3b are formed at positions separated from each other in the optical axis direction, when the lens holder 3 to which the condenser lens 2 is fixed is press-fitted into the casing 1, Does not act directly on the condenser lens 2. For this reason, the condensing lens 2 can be steadily prevented from cracking or cracking.

  In addition, it is desirable that the material of the lens holder 3 be the same material as that of the housing 1, for example, stainless steel. Thereby, the stress accompanying shrinkage | contraction of the housing | casing 1 and the lens holder 3 accompanying the change of environmental temperature can be relieved, and the optical axis fluctuation | variation of the condensing lens 2 can be suppressed. Moreover, the workability at the time of processing the housing 1 and the lens holder 3 is facilitated, and the lead time can be shortened.

FIG. 6 is a diagram showing another example of the lens holder in the optical module of the present invention.
In the lens holder 3 shown in FIG. 6, with respect to the groove 3d developed on the lens holding part 3a side of the connecting part 3c in FIG. 4, the developing distance to the lens holding part 3a side is shortened, and the groove 3d is also developed on the press-fitting part 3b side. is doing. That is, the groove 3d exists on either the holding part 3a or the press-fitting part 3b, and the depth from the bottom of the groove to the inner hole of the press-fitting part 3b is increased by thorough the depth of about 0.3 mm. The thickness is about 0.3 mm and has the thinnest thickness at the bottom, which is even thinner than the example of FIG. Further, in the lens holding portion 3a, the length of the region that secures a clearance of about 10 μm with respect to the inner hole of the housing 1 is lengthened, and the process of inserting the holder 3 into the inner hole of the housing 1 is further stabilized. It has become.

As described above, in the present embodiment, the inner hole of the housing 1 of the lens mounting unit has a circular cross section, and the outer surface of the lens holder 3 has a circular cross section, but the inner hole of the housing 1 does not necessarily have a circular cross section. In addition, the outer surface of the lens holder 3 may have a shape that can be press-fitted into the inner hole of the housing 1. For example, it is possible to make the inner hole of the housing 1 into a polygonal shape such that a lens holder having a cylindrical shape can be fixed by press fitting.
The optical module according to the present invention is not limited to a single-fiber bidirectional optical module, and can be applied to all modules in which a lens is fixed to a lens holder and then the lens holder is fixed to a lens mounting member by press-fitting. is there.

DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Lens, 3 ... Lens holder, 4 ... Gap, 10 ... Lens mounting unit, 11 ... 1st WDM filter, 12 ... 2nd WDM filter, 13 ... Cut filter, 20 ... Stub, 30 ... 1st sending Trust device, 40 ... second transmitting device, 50 ... receiving device, 101 ... holding component, 102 ... optical coupling lens, 103 ... light receiving / emitting element, 104 ... optical fiber fixture, 201 ... exterior member, 202 ... Ball lens, 203... Optical semiconductor element, 204.

Claims (5)

  An optical module in which an optical lens is fixed to a lens holder, and the lens holder is fixed by press-fitting into an inner hole of a housing of a lens mounting unit, wherein the lens holder includes a lens holding unit that holds the optical lens; A press-fitting part that is press-fitted into an inner hole; and a connecting part that connects the lens holding part and the press-fitting part. The outer diameter of the lens holding part is smaller than the inner diameter of the inner hole, An optical module, wherein a gap is formed between an inner hole and the lens holding portion, and a groove is formed on an outer periphery of the connecting portion.   The optical module according to claim 1, wherein the lens holder and the housing of the lens mounting unit are made of the same material.   The optical module according to claim 1, wherein the groove is provided on the lens holding unit side from the connecting portion.   The said groove | channel is formed ranging over the said lens holding | maintenance part and the said press-fit part, and has a part in which the thickness of the said lens holder becomes the minimum in the said connection part. 2. The optical module according to 2.   The optical module according to claim 1, wherein the lens holding portion has a thickness that is greater than a thickness of the press-fit portion.

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