JP2005070568A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module whose characteristic is stabilized, which can be easily assembled at low cost, and which is friendly to the global environment as the optical module which is equipped with light emitting and receiving elements, optical fiber fixtures and a lens for optical coupling and is formed by press fitting and fixing the lens for optical coupling to holding components. <P>SOLUTION: In the optical module which is equipped with the light emitting and receiving elements, the optical fiber fixtures and the lens for optical coupling and is formed by press fitting and fixing the lens for optical coupling to the holding components, an abutment part of the holding components and the lens for optical coupling is provided with a thin-walled part or through-hole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical module used for optical communication.

  In general, an optical module is a device in which an optical semiconductor element (for example, a semiconductor light emitting element such as a laser diode or a semiconductor light receiving element such as a photodiode) and an optical component (for example, a lens or an optical fiber ferrule) are aligned and held. The semiconductor device includes a semiconductor element, a lens, the optical semiconductor element, a component that holds the lens, and a component that holds the optical fiber ferrule. The optical semiconductor element and the optical fiber are optically coupled via the lens. .

  When manufacturing an optical module, the optical semiconductor element, the lens, and the optical fiber are usually aligned in an optically optimal positional relationship, and the optical semiconductor element is attached to a component that incorporates the lens and fixes the optical fiber. Fix it. For example, when the optical semiconductor element is a laser diode, the laser diode is operated, the emitted light is extracted from the optical fiber, and the laser diode is fixed at a position where the amount of the extracted laser emitted light is maximized.

  Various coupling lenses such as spherical lenses, aspherical lenses, and gradient index rod lenses are used as lenses incorporated into optical modules. Among them, it is inexpensive because high-precision products can be easily manufactured only by machining. Since there is an orientation and there is no directivity at all, there is an advantage that an orientation adjustment at the time of lens mounting is unnecessary and it is easy to assemble, and a spherical lens is often used.

  FIG. 7A shows an example of a conventional optical module with a fixed lens. A lens receiving portion 12 is formed inside the lens holding component 1, and the lens 2 is dropped into the lens holding portion 12 and fixed with an adhesive 13, solder, low melting point glass or the like. In terms of cost, an adhesive was used for fixing the lens. As the adhesive at this time, an epoxy-based thermosetting or photo-curing type is usually used, and after bonding, annealing treatment is performed for a predetermined time for shape stabilization.

  As a solution to this problem, there is a press-fit fixing method.

  FIG. 7B is an example of an optical module using a conventional lens press-fitting process. At one end of the lens holding component 1, the thickness T of the lens holding component 1 is managed up to the press-fitting position of the lens 2 in order to press-fit the lens 2. Since the thickness T of the lens holding component 1 is extremely thin, it cannot be directly joined to the ring 5. For this reason, the auxiliary sleeve 15 is required, and the number of parts increases. Further, since the auxiliary sleeve 15 is used, the outer diameter is increased, the entire optical module 400 is also increased, and downsizing is difficult.

  8A to 8D show conventional press-fitting fixation. In FIG. 8A, a locking projection 17a and a lens receiving portion 17b for sandwiching the lens 2 in the lens holding component 17 are provided.

  Further, as shown in FIG. 8A, the lens holding part 17 is provided with a lens receiving part 17b, and a plurality of locking projections 17a into which the outer peripheral part of the lens 2 is press-fitted are provided on the lens 2 insertion side. There is also a structure in which 2 is fixed to the lens receiving portion 17b through the locking projection 17a (see Patent Document 1).

  FIG. 8B is a front view of FIG.

  In FIG. 8C, the lens holding component 18 is provided with a claw-like protrusion 18 a for fixing the lens 2. FIG. 8D is a front view of FIG.

Further, as shown in FIG. 8C, in the lens receiving portion 18b of the lens holding component 18 using a resin such as plastic, the lens insertion side is a claw-shaped projection 18a, and the inside of the claw-shaped projection 18a. There is also a structure in which the lens 2 is inserted (see Patent Document 2).
JP-A-11-84197 Japanese Patent Laid-Open No. 11-174282

  As shown in FIG. 7A, the lens receiving part 12 is formed inside the lens holding component 1, the lens 2 is dropped into the lens holding part 12, and the lens 2 is fixed with an adhesive 8 or the like. There was a problem. First, there was an application work of the adhesive 8, and this work was extremely difficult. For example, when the coating amount is large, the lens surface is soiled. Conversely, when the coating amount is small, the problem of insufficient adhesion is unavoidable. Further, after applying the adhesive, a certain amount of time is required until the adhesion is stabilized, and workability is poor. Furthermore, in the case of fixing with such an adhesive 8, there has been a problem that the optical axis is liable to be displaced when the resin is cured.

  In FIGS. 8A and 8C, since the lens fixing shape of the lens holding component is complicated, the lens holding component is expensive. Further, FIG. 8C has a limitation that it can be applied only to a lens holding part made of resin such as plastic because of its shape.

  There are also regulations on environmentally hazardous substances internationally, and when environmentally hazardous substances are contained in auxiliary materials such as adhesives, solder, and low-melting glass, restrictions are imposed such as prohibition of use.

  In the conventional optical module, there are various restrictions and concerns depending on auxiliary materials such as adhesive, solder, and low melting point glass used when fixing the lens. For example, in the case of an adhesive, there is a possibility of deteriorating the characteristics of the lens and the optical semiconductor element due to the problem of outgas emitted from the adhesive. In the case of solder, the lens and the holding parts need to be plated, and the work becomes complicated. In the case of low-melting glass, the lens is cracked if the melting point and linear expansion coefficient of the lens, the holding parts, and the low-melting glass used are not properly matched. In any case, there are restrictions on environmentally hazardous substances, and secondary materials such as adhesives, solder, and low-melting glass should not be used.

  There is a press-fitting method that does not use an auxiliary material such as an adhesive, solder, or low-melting glass. However, it is difficult to process a member to be used by providing the locking projection 17a in the lens holding component 17 as in Patent Document 1 described above. The degree was high and it was a factor of cost increase.

  Similarly, in the above-mentioned Patent Document 2, it is necessary to form a claw-like protrusion 18a having a very complicated shape on the lens holding component 18, which causes a cost increase. Further, there is a limitation of the lens holding component 18 made of resin such as plastic.

  As described above, the press-fitting is difficult to adopt because the size of the press-fitted parts is strict and the shape is complicated.

  An object of the present invention is to provide a press-fit structure that does not require strict dimensional control of components without using auxiliary materials such as an adhesive, solder, and low-melting glass when fixing a lens. Furthermore, since the lens holding structure is extremely simple, a more inexpensive optical module is provided.

  The present invention is intended to solve these problems, and includes an optical module including a light receiving and emitting element, an optical fiber fixture, and an optical coupling lens, wherein the optical coupling lens is press-fitted and fixed to a holding component. A thin portion or a through hole is formed in a contact portion of the component for use with the optical coupling lens.

  In addition, the shape of the coupling lens is a spherical shape, a cylindrical shape, or a cubic shape.

  Further, the thickness of the thin part of the holding part is in the range of 0.1 mm to 0.5 mm.

  Further, the width of the thin portion of the holding part is in the range of 0.1 mm to 1.0 mm.

  In addition, a buffer material is interposed in a contact portion between the holding component and the optical coupling lens.

  As described above, in the optical module of the present invention, since the press-fitting method is used for fixing the lens, no auxiliary materials such as adhesive, solder, and low melting point glass are used. For this reason, cost reduction of a member can be aimed at. Further, the deterioration of the light transmission characteristics due to the adhering of the auxiliary material to the lens is eliminated, and the stable characteristics of the lens can be obtained. Furthermore, since there is no need for environmentally hazardous substances, the product is friendly to the global environment.

  Further, since the shape of the lens holding component is extremely simple, the cost of the lens holding component is also reduced. Further, since the holding parts are simple, the shape of other parts connected when the optical module is configured is also simplified, and an inexpensive optical module as a whole is realized.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1A is a cross-sectional view showing an example of the optical module of the present invention. As shown in FIG. 1A, in an optical module 100, a lens 2, an optical fiber pigtail 4, and an optical semiconductor element 6 are optically coupled. Physically, the optical fiber pigtail 4 is fixed to the sleeve 3 by welding or the like, and the sleeve 3 and the lens holding component 1 are also fixed by welding or the like. Similarly, the optical semiconductor element 6 is fixed to the ring 5 by welding or the like, and is fixed to the ring 5 and the lens holding component 1 by welding or the like. When each component is fixed by welding, an alignment step is required to fix the component at an optically optimal position.

  The lens holding component 1 is provided with a thin portion 1a by forming a groove in a part of the outer periphery, and the lens 2a is fixed inside the thin portion 1a, and the thin portion 1a is in an optically optimal position. Is formed. Depending on the design, the alignment of the semiconductor element 6 and the optical pigtail 4 in the Z-axis direction is not necessary, and the number of man-hours can be reduced.

  FIG. 1B is an enlarged view of the lens holding component 1.

  The lens holding component 1 may be a cylindrical shape or a prismatic shape, but is preferably a cylindrical shape that can be easily processed. The shape of the light path portion 8 into which the lens 2 is inserted is preferably a cylindrical shape that can be easily processed. The width W of the thin portion 1a is preferably 0.1 to 1.0 mm. As the width W of the thin portion 1a increases, the thin portion 1a is more likely to be deformed when the lens 2 is press-fitted and fixed. However, if the width W exceeds 1.0 mm, the fixing position accuracy of the lens 2 deteriorates. Since 1a is hard to deform | transform, it cannot fix.

  If the thickness T of the lens holding component 2 in the thin portion 1a is about 0.1 to 0.5 mm, the thin portion 1a is likely to be elastically deformed, and the press-fitting position accuracy is stabilized. If the thickness is less than 0.1 mm, the strength of the thin portion 1a cannot be obtained, and the function as an optical module cannot be achieved. Moreover, if the thin part 1a exceeds 0.5 mm, the thin part 1a becomes difficult to deform.

  Since the thin portion 1a is a portion that tends to be weak in strength, the strength can be increased by forming the fillet portion 1b with an R surface or the like.

  When the lens 2 is press-fitted and fixed by the thin portion 1a, the large diameter side 8a of the lens holding component 1 is slightly larger than the size of the lens 2 (large diameter side 8a)> (diameter of the lens 2). The pushing force is reduced and work efficiency is increased. That is, until the thin portion 1a, a counterbore is provided on the large-diameter side 8a of the optical path portion 8, and the small-diameter side 8b is preferably the same as the press-fit fixing portion in the vicinity of the thin portion 1a ((small diameter Side 8b) <(diameter of lens 2)).

  Thus, when the fixed position accuracy of the lens 2 is good, the man-hours for optical alignment are reduced, and the shape of the lens holding component 1 is simple, so that the entire optical module 100 is simplified, This leads to cost reduction.

  FIGS. 2A to 2D are embodiments of the present invention in the lens holding component 1 according to the type of the lens 2. FIG. 2A is a cross-sectional view in which a horizontally long lens 2 is press-fitted into the lens holding component 1. In general, aspherical lenses often have this shape. FIG. 2B is a cross-sectional view in which the vertically long lens 2 is press-fitted into the lens holding component 1. FIG. 2C is a cross-sectional view in which the cylindrical lens 2 is press-fitted into the lens holding component 1. This shape is often found in gradient index rod lenses. FIG. 2D is a cross-sectional view in which the cubic lens 2 is press-fitted into the lens holding component 1. In the case of the cubic lens 2, the contact portion 1 c with the thin portion 1 a of the lens holding component 1 is the four points of the corner portion 2 a of the lens 2, and it is not necessary to reduce the thickness except for the contact portion 1 c. The portion that is not the thin portion 1a serves as a reinforcing beam 1d.

  The cylindrical or cubic lens 2 needs to be processed on the C surface and the R surface with respect to the corner 2a in order to prevent lens cracking and chipping during press-fitting.

  As the material of the lens 2, borosilicate glass or quartz glass is used.

  The material of the lens holding component 1 is SUS303, which is easy to process and elastically deforms. For example, in the case of configuring as a copper alloy such as brass or phosphor bronze or an optical module, the components are easily fixed by welding. Stainless steel such as SUS304 and SUS430, an alloy of 50Ni-Fe and 49Ni-Fe, or a metal such as SF20T and ASTM-F15 is preferable.

  In order to increase the stability of the lens holding, it is preferable to use the buffer material 7 for the lens contact portion 1c of the lens holding component 1. As the material of the buffer material 7, a shape that conforms to the shape of the lens 2 that comes into contact with the lens holding component 1 is good, and therefore, lead, gold, copper, Ni, aluminum, and the like that easily cause plastic deformation are suitable. Further, as the role of the buffer material 7, the lens holding component 1 may be subjected to a clad tube or a plating process.

  FIGS. 3A to 3C show another embodiment of the present invention in the lens holding component 1.

  3A, the lens holding component 1 is provided with a through hole 1e instead of the thin portion 1a. In addition to elastic deformation of the lens holding component 2, the lens 2 is fixed by fitting a part of the lens 2 into the through hole 1e. Although the number of through holes 1e may be one, in order to obtain stable fixation of the lens 2, it is preferable that there are two or more through holes 1e. The shape of the through hole 1e may be round or square. For example, when the lens 2 is a spherical lens having a diameter of 1.0 mm, the diameter of the through hole 1e is preferably set to 0.2 mm or less. When the diameter is larger than 0.2 mm, the small diameter side 8b of the lens holding component 1 becomes too narrow with respect to the lens 2, and the lens 2 cannot be press-fitted and fixed. Another effect of the through hole 1e is air flow in the optical module 100. In general, when moisture accumulates inside the optical module, condensation may occur on the lens 2 in the optical module in accordance with the outside air temperature of the optical module, which may deteriorate lens characteristics, for example, transmitted light characteristics. By forming the through hole 1e for air flow in the optical module, moisture does not accumulate in the optical module 100 and no condensation occurs.

  FIG. 3B shows a structure in which a groove is formed on the inner peripheral surface of the lens holding component 1 and a Ni thin portion 1 f is provided. Since the thin portion 1b is not formed in the outer diameter portion 1g of the lens holding component 1, the restriction when inserting and fixing a sleeve (not shown) as another component to the lens holding component 1 can be removed. For example, when a thin portion 1f is formed on the outer diameter portion 1g of the lens holding component 1 when the sleeve is inserted into the lens holding component 1 and welding is performed from the outer periphery for fixing, the position is welded. It is a restriction that cannot be done.

  FIG. 3C shows a case where two lenses 2 are fixed to the lens holding component 1.

  As shown in FIG. 3C, it is possible to fix a plurality of lenses 2 to one lens holding component 1 relatively easily. In addition, since the lens 2 is arranged on the same axis as the lens holding component 1 only by press-fitting, no alignment process is required for the two lenses 2.

  FIG. 4 shows an optical module 200 according to another embodiment of the present invention. The receptacle-type lens holding component 9 has a receptacle function for inserting an optical connector (not shown), and an optical fiber stub 10 is fixed inside the receptacle-type lens holding component 9.

  FIG. 5 shows the lens press-fitting procedure of the present invention. FIG. 5A shows the lens 2 to be press-fitted with the lens holding component 1. When it is necessary to manage the position and direction of the AR coating or the like on the lens 2 to be press-fitted, the direction is confirmed in advance and set in the lens holding component 1. FIG. 5B is a diagram in which the lens 2 is press-fitted into the lens holding component 1. The outer periphery of the lens 2 is press-fitted into the lens 2 using a press-fitting jig 11 while avoiding the optical axis that is near the center of the lens 2. It is preferable to use resin-made silicon or the like for the press-fit contact portion 11b of the press-fit jig 11 so that the lens 2 is not scratched or displaced during press-fit. FIG. 5C shows a state in which the lens 2 is securely pressed into the lens holding component 1.

  As described above, in the optical module of the present invention, since the press-fitting method is used for fixing the lens, no auxiliary materials such as adhesive, solder, and low melting point glass are used. For this reason, cost reduction of a member can be aimed at. Further, the deterioration of the light transmission characteristics due to the adhering of the auxiliary material to the lens is eliminated, and the stable characteristics of the lens can be obtained. Furthermore, since there is no need for environmentally hazardous substances, the product is friendly to the global environment.

  Further, since the shape of the lens holding component 1 is extremely simple, the cost of the lens holding component 1 is also reduced. In addition, since the lens holding component 1 is simple, the shape of other components connected when the optical module 100 is configured is also simplified, and an inexpensive optical module as a whole is realized.

  As shown in FIG. 1, an optical module 100 is manufactured by press-fitting a lens 2 into a lens holding component 1 having a thin portion 1 a according to the present invention. The material for the lens holding component 1 was SUS304, and the lens 2 was a spherical lens.

  Further, as shown in FIG. 7A, an optical module 400 in which the lens 2 was bonded and fixed to the lens holding component 1 was manufactured as a comparative example. Similar to the optical module 100, the material of the lens holding component 1 is SUS304, and the lens 2 is a spherical lens. The adhesive was a thermosetting type epoxy adhesive.

  Then, the coupling efficiency at the time of producing five optical modules was evaluated. In order to see the difference depending on the fixing method of the lens holding component 1, the same optical fiber pigtail 4 and optical semiconductor element 6 were used, and the lens holding component 1 was replaced and evaluated. The optical input Pi to the optical module 100 emitted from the optical semiconductor element 6 is measured, and the optical output Po from the optical fiber pigtail 4 is measured via the lens 2.

  The coupling efficiency η (%) was η = Po / Pi × 100, the measurement wavelength was 1310 nm, and the optical input was 1 mW.

The results are shown in Table 1.

  The maximum value of the coupling efficiency L does not change between the present invention and the conventional example, but the minimum value is different. This is because the effective diameter of the lens 2 is blocked by the adhesive 13 and the light transmission characteristics deteriorate.

  Moreover, the light output fluctuation | variation Po (dB) as an optical module in the high temperature, high humidity test (condition; 85 degreeC, 85% RH, 1000 hours) was evaluated. The graph of the result is shown to Fig.6 (a) and (b).

  FIG. 6A shows the light output characteristics in the high-temperature and high-humidity test of the optical module 100 according to the present invention. FIG. 6B shows light output characteristics in a high temperature and high humidity test of the optical module 400 according to the conventional example.

  The light output fluctuation of the conventional example has already deteriorated after 500 hours and continues to deteriorate after 1000 hours.

  In contrast, the light output fluctuation of the present invention is stable even after 1000 hours. The reason why the optical output characteristic of the optical module 400 of the conventional example is remarkably deteriorated can be presumed to be an optical axis deviation due to the adhesive 13 fixing the lens 2 being softened or swollen by absorbing moisture.

(A) is sectional drawing which shows embodiment of the optical module of this invention. (B) is an enlarged sectional view of a lens holding component. (A) thru | or (d) are sectional drawings which show embodiment of each lens in the lens holding component of this invention. (A) thru | or (c) are sectional drawings which show other embodiment in the components for lens holding | maintenance of this invention. It is sectional drawing which shows other embodiment of the optical module of this invention. (A) thru | or (c) are sectional drawings which show the lens press-fit procedure in the lens holding component of this invention. (A) And (b) is the graph which compared the Example and the prior art example. (A) is sectional drawing which shows embodiment of the optical module using the adhesion method which is the conventional lens fixing method.

(B) is sectional drawing which shows embodiment of the optical module using the press injection method which is the conventional lens fixing method.
(A) And (c) is sectional drawing in the conventional lens holding component, (b) And (d) is a front view of (a) and (c), respectively.

Explanation of symbols

1: Lens holding part 1a: Thin part 1b: Fillet part 1c: Contact part 1d: Beam part 1e: Through hole 1f: Thin part 1g: Outer diameter part 2: Lens 2a: Corner part 3: Sleeve 4: Light Fiber pigtail 5: Ring 6: Optical semiconductor element 7: Buffer material 8: Optical path portion 8a: Large diameter side 8b: Small diameter side 9: Receptacle type lens holding component 9a: Thin portion 10: Optical fiber stub 11: Press fit treatment Tool 11b: Press-fit contact portion 12: Lens receiving portion 13: Adhesive 14: Lens holding component 15: Sleeve 16: Lens holding component 17: Lens holding component 17a: Projection 17b: Lens receiving portion 18: Lens holding Component 18a: Claw-shaped protrusion 18b: Lens receiving part 100: Optical module 200: Optical module 300: Optical module 400: Optical module

Claims (5)

In an optical module comprising a light receiving and emitting element, an optical fiber fixture, and an optical coupling lens, and wherein the optical coupling lens is press-fitted and fixed to a holding component, the contact portion of the holding component with the optical coupling lens is thin. An optical module characterized in that a part or a through hole is formed. 2. The optical module according to claim 1, wherein the coupling lens has a spherical shape, a cylindrical shape, or a cubic shape. 2. The optical module according to claim 1, wherein the thickness of the thin part of the holding part is in the range of 0.1 mm to 0.5 mm. 2. The optical module according to claim 1, wherein a width of the thin part of the holding part is in a range of 0.1 mm to 1.0 mm. 2. The optical module according to claim 1, wherein a buffer material is interposed in a contact portion between the holding component and the optical coupling lens.

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