JP2004133104A - Optical communication module - Google Patents

Abstract

An optical communication module is provided which solves the problem of difficulty in adjusting the optical axis of the conventional optical communication module and which is easy to assemble.
An optical communication module includes at least an optical fiber and a lens, wherein the lens has an optical curved surface focusing inside or on an end surface thereof, and holds the optical fiber at a position facing the optical curved surface. Holding means, and the optical fiber is held by the holding means of the lens so that the end face thereof is located at the focal point of the lens, whereby the position adjustment and the optical axis adjustment of the end of the optical fiber are completed. Or at least it became easier. In addition, the number of components used in the optical communication module can be reduced, and highly accurate optical axis adjustment has become possible.
[Selection diagram] Fig. 3

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical communication module.
[0002]
In data communication using an optical fiber, it is necessary to transmit and receive a large amount of information at high speed. In recent years, a new technology called a wavelength division multiplexing transmission system has appeared, and it is possible to further increase the speed and increase the capacity. Under such circumstances, the demand for optical communication components is increasing more and more, and cost reduction and improvement in reliability have been issues for component suppliers.
[0003]
[Prior art]
Heretofore, in the optical communication component mounting module, when assembling the optical components in combination, the optical axes of the optical components have been adjusted and aligned one by one and fixed with resin or metal. However, in this method, the adjustment takes time, there is a problem in manufacturing efficiency, and it has been a factor that an inexpensive product cannot be supplied. This is because high precision is required particularly for positioning the optical fiber and optical components such as lenses connected thereto. For example, in a wavelength division multiplexing transmission system, a so-called WDM filter module for selectively extracting only a signal of a specific wavelength has a structure having three terminals of incident light, transmitted light, and reflected light. Conventionally, as shown in FIG. 1, this module was composed of five parts: a dual capillary, a first collimating lens, a filter element, a second collimating lens, and a single capillary. The optical axis of each of these components is fixed in an adjusted and aligned state, and sealed in a metal tube or the like. In the case of such a structure, the accuracy of aligning the center of the core of the optical fiber inserted into the capillary with the position of the focal point of each collimating lens requires a typical value within ± 5 μm, and the optical axis has The degree of parallelism was also required, which required a very advanced position and optical axis adjustment process.
[0004]
As means for solving the above problem of optical axis adjustment, the following Patent Documents 1 and 2 are known.
[0005]
Patent Literature 1 discloses a sleeve-integrated lens in which an edge portion of a lens portion functions as a sleeve for introducing and positioning an optical fiber. However, the sleeve formed integrally with the lens disclosed in Patent Document 1 is a member for fixing the ferrule portion of the optical fiber with a ferrule. Therefore, the ferrule is an indispensable part, the number of parts is increased, and an axis shift occurs between the fiber and the ferrule, and between the ferrule and the sleeve, and there is a problem that it is difficult to perform high-precision optical axis alignment.
[0006]
On the other hand, Patent Document 2 discloses an optical fiber coupler in which a transparent spacer for positioning adjustment is provided between a lens and a fiber. However, the positioning of the fiber is performed only in the thickness of the transparent spacer, that is, only in the optical axis direction, and there is no function of positioning the spacer itself in the direction perpendicular to the optical axis. Therefore, the alignment in the vertical direction with respect to the optical axis is performed by attaching the fiber to the ferrule and between the ferrule and a cylindrical member such as a sleeve. Then, as in Patent Document 1, the ferrule becomes an essential part, the number of parts increases, and it becomes difficult to perform high-precision optical axis alignment.
[0007]
[Patent Document 1]
JP-A-7-134225 [Patent Document 2]
JP-A-5-34545
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION It is an object of the present invention to solve the problem that the optical axis adjustment is difficult in the conventional optical communication module, and to provide an optical communication module that can be easily assembled.
[0009]
[Means for Solving the Problems]
A first aspect of the present invention is an optical communication module including at least an optical fiber and a lens, wherein the lens has an optical curved surface that focuses on an inside or an end surface thereof, and faces the optical curved surface. An optical communication module, comprising: holding means for holding the optical fiber at a position, wherein the optical fiber is held by the holding means for the lens such that an end face thereof is located at the focal point of the lens. Things.
[0010]
In the optical communication module of the present invention, the holding means for holding the optical fiber of the lens is formed on the lens surface as, for example, a cylindrical concave portion into which the optical fiber can be inserted as schematically shown in FIG. The position of the bottom of the cylindrical concave portion and the direction of the central axis of the cylindrical portion are formed in advance with appropriate precision so that the tip of the optical fiber to be connected can be positioned at the focal position of the lens. Then, the optical axis of the optical communication module according to the present invention can be adjusted only by inserting the optical fiber into the cylindrical concave portion and holding the optical fiber by bringing the end face of the optical fiber into contact with the bottom of the cylindrical concave portion. Since the optical component having this joint is molded integrally with the optical component body and the optical fiber joint by molding, if the mold is manufactured, if the processing accuracy of the mold member corresponding to the joint is ensured, At the time of assembling the molded optical component, the adjustment of the position and / or the adjustment of the optical axis of the end of the optical fiber is completed or at least simplified simply by placing the tip of the optical fiber at the joint.
[0011]
The shape of the joint is basically a cylindrical shape into which an optical fiber can be inserted. However, as long as the object of the present invention can be achieved, other shapes such as a concave portion on a rectangular parallelepiped can be used for processing convenience. Further, as shown in the right diagram of FIG. 2, in order to facilitate insertion of the optical fiber at the time of assembling, a structure in which the opening is widened on the optical fiber insertion side, that is, a so-called tapered structure can be provided. With this structure, there is also an advantage that the mold member can be easily pulled out of the molded body during molding. Further, as another holding means of the optical fiber, a V-groove in which the optical fiber can be installed may be mentioned. A V-groove integrated lens in which a member having a V-groove formed with an optical fiber and a lens are integrated can be used for the optical communication module of the present invention.
[0012]
Further, in the past, it was usual that the focus of the lens was formed in a hollow outside the lens. In the present invention, the focal point formed by the lens is formed inside or at the end of the lens itself. Further, since the optical fiber is directly held at the focal position, components such as a conventionally used ferrule become unnecessary, and the number of components can be reduced. Therefore, it is possible to reduce the deviation of the optical axis generated between the components, and it is possible to perform the optical axis alignment with higher accuracy.
[0013]
According to a second aspect of the present invention, there is provided an optical communication module including at least an optical fiber, a lens, and a spacer made of a transparent member, wherein the lens has an optical curved surface that focuses on the inside or an end face of the spacer. The spacer is located opposite the lens, and has holding means for holding the optical fiber on the side opposite to the side facing the lens, and the optical fiber has an end face The present invention relates to an optical communication module, which is held by holding means of the spacer so as to be located at the focal point of the lens.
[0014]
The second embodiment is an example of an optical communication module having at least an optical fiber, a lens, and a spacer. In the lens of the second embodiment, the focus of the lens is not on the lens itself but on the inside of the spacer, which is a component other than the lens, or on the end face thereof. The spacer has optical fiber holding means, and holds the optical fiber such that the end face of the optical fiber comes to the focal position of the lens. As in the first embodiment, the holding means may be, for example, a cylindrical recess, and the optical axis can be automatically aligned only by holding the optical fiber in the recess. Further, the focal point of the lens is not formed in a hollow state as in a conventional ordinary lens, but is formed inside or at an end face of a transparent member called a spacer. Therefore, similarly to the first embodiment, the optical fiber can be directly held on the spacer, and advanced axis adjustment is also possible. In the present invention, the spacer needs to be a member transparent to the wavelength used for optical communication due to its nature. Further, the spacer may be an optical component having an optical function such as a filter.
[0015]
【Example】
The following examples illustrate the invention in detail.
(Example of 3-terminal filter module for WDM)
As a first embodiment of the present invention, a lens component having the structure shown in FIG. 4 will be described. This is an example in which the present invention is applied to the second collimator lens of the WDM three-terminal filter module. FIG. 3 shows a schematic diagram when this is configured as a module.
[0016]
The lens of this embodiment has an optical curved surface on the filter element side as shown in FIG. An optical fiber holding unit is provided on the side facing the optical curved surface, and the holding unit and the optical curved surface are formed integrally. Mold molding was performed using optical glass as a lens material. The optical fiber holding means of the present embodiment was a cylindrical recess. Also, the opening of the cylindrical concave portion was expanded in a tapered shape.
[0017]
The curved surface of the lens is designed so that the focal point of the lens is located on the center of the bottom surface of the cylindrical concave portion. As the curved surface of this lens, a so-called aspherical lens having different curvatures at the peripheral portion and the central portion was used. The rotation center axis of the cylindrical concave portion is designed to be located on the optical axis of the lens. Also, optical glass, transparent resin, or the like is suitable as a constituent material of the lens. When direct connection with an optical fiber is performed using the optical fiber holding means according to the present invention, it is necessary to minimize coupling loss.However, the refractive index of the lens material should be the same as the refractive index of the core of the optical fiber to be joined. Thereby, both can be easily connected in a process described later.
[0018]
FIG. 5 shows an enlarged view of the cylindrical concave portion. The diameter of the cylindrical recess is preferably designed with a clearance of +0.5 to +5.0 microns with respect to the diameter of the optical fiber to be inserted, and more preferably +0.5 to +2.0 microns. This clearance is the accuracy of the deviation between the center of the optical fiber and the focal point of the lens when the optical fiber is inserted and connected to the lens. When the deviation has an accuracy of +5.0 μm or less, the connection loss is 0.1 dB or less, which is a usable range. Actually, the accuracy at the time of manufacturing the mold, that is, the processing accuracy of the center of the convex portion of the cylindrical concave member corresponding to the optical axis of the lens is added. Since this precision is substantially on the order of ± 3 μm, a good connection state can be realized if the diameter of the cylindrical concave portion of the guide is +2.0 μm or less with respect to the diameter of the inserted fiber. The lower the lower limit of the clearance is, the smaller the connection loss is. However, if the lower limit of the clearance is substantially 0.5 μm or less, there is a problem that a gap between the optical fiber and the optical fiber is too small to be easily inserted at the time of assembly. 0.5 microns or more is reasonable.
[0019]
Further, since the purpose of this configuration is to facilitate positioning of the end of the optical fiber and determination of the optical axis, the depth of the cylindrical concave portion is an arbitrary value within a range that can achieve this purpose. As a preferable state, it is preferable that the diameter is deeper than the diameter of the fiber to be inserted, in order to keep the angle of the center of the optical fiber core with respect to the optical axis of the lens in parallel. On the other hand, when the cylindrical concave portion is deep, there is a problem that the mold member forming the joining portion is difficult to come off from the molded body during molding. In consideration of these points, it is preferable that the depth d of the cylindrical concave portion is in a range represented by the following expression with respect to the diameter Φ of the fiber to be inserted.
Φ ≦ d ≦ 5 × Φ
[0020]
Next, an assembly process of the optical communication module of the present invention will be described. The assembly drawing is shown in FIG. The components include an optical fiber for incident light, an optical fiber for reflected light, a dual capillary that is a member for holding the two optical fibers, and an optical fiber holding unit that can directly join the two optical fibers by applying the present invention. A first collimating lens, a thin film filter element for WDM, and a lens for converging transmitted light, a second collimating lens capable of directly joining an optical fiber for transmitted light by applying the present invention, Optical fiber, and a sleeve for mounting these optical components.
[0021]
The optical fiber is held by the capillary in such a manner that the tip of the optical fiber is protruded in advance beyond the depth of the joint. The capillary may be made of a known member such as zirconia or quartz. Further, the shape can be arbitrarily configured according to the completed form of the module. In this embodiment, the shape is made cylindrical, and the diameter is made the same as that of the collimating lens. (Referred to as a sleeve). The optical axis of the lens is positioned with appropriate accuracy by designing the outer diameter of the lens and the inner diameter of the sleeve. Thereby, the optical axes of the first collimating lens and the second collimating lens are also roughly adjusted.
[0022]
On the other hand, since the function of the capillary is only to hold the optical fiber, its positioning accuracy may be low. In the present embodiment, the diameter of the cylindrical space through which the optical fiber of the capillary passes is set to 150 microns, and an inexpensive material having a large clearance with the optical fiber and low accuracy is used. The displacement of the core center of the optical fiber with respect to the optical axis is absorbed by the space between the capillary and the collimating lens and the space of the tapered portion of the opening provided in the concave portion of the lens, and is aligned in the concave portion. The space between the capillary and the sleeve, the space between the lens and the sleeve, and the like were fixed with an epoxy resin adhesive.
[0023]
The space between the end of the optical fiber and the bottom of the cylindrical concave portion of the lens is filled with a flowable substance such as a polymer material having the same refractive index as the lens member at the time of mounting, so that the lens and the optical fiber are optically scattered. -Connection can be made with less loss. Also, in order to mount the optical fiber more securely, irradiate high-power laser light from the lens side with a carbon dioxide gas laser, etc., with the tip of the optical fiber reaching the bottom of the joint, and Welding to the bottom surface of the concave portion of the lens enables more stable and low-loss bonding.
[0024]
As the filter element, a so-called thin film filter element in which a dielectric thin film was laminated in multiple layers on a glass substrate by a process such as vacuum deposition was used. In assembling this module, the filter element adjusts the angle of the thin film surface near perpendicular to the optical axis of the lens, so that the reflected light is used as an end face of the filter for reflected light, that is, for the filter for reflected light. The filter element was adjusted so as to condense light at the center of the bottom surface of the joint, and the filter element was fixed in this state with an adhesive.
[0025]
In another embodiment of the present invention, a structure having a V-shaped groove as schematically shown in FIG. 7 is integrally formed of the same material as the lens as a holding means for the optical fiber on the side where the optical fiber is connected to the lens. There are ways. The focal point of the lens is located at the tip of the V-groove on the lens side. When the end of the optical fiber is joined to the V-groove and the end of the optical fiber is attached to the V-groove, the tip of the optical fiber is located at the focal point of the lens and The central axis is located on the optical axis of the lens. When the optical fiber is mounted in the V-groove and fixed by bonding or the like, it is possible to join the optical fiber and the lens without adjusting the optical axis by a high technology.
[0026]
Further, in the embodiment, the example in which the present invention is applied to the aspherical lens using the optical glass has been described, but various other applications are possible. First, the material is not limited to optical glass, and it is particularly preferable to apply the present invention to mold molding using a transparent plastic material. In addition, a lens can be applied to a spherical lens or a lens having another configuration depending on its use and purpose. FIG. 8 shows an example in which the present invention is applied to a so-called GRIN (graded index) lens having a refractive index distribution inside the lens. In the case of this lens, since it is difficult to integrally mold with a mold as in the above-described embodiment, a resist is applied and exposed to light to form a mask, which is formed by a reactive ion etching method, or a FIB (Focused Ion). The method of the present invention can be realized by a method of directly processing according to Beam). In addition, as an element other than the thin film filter module, for example, a coupling lens for guiding a laser beam emitted from a laser to an optical fiber can be widely applied.
[0027]
【The invention's effect】
In the optical communication module, the optical communication module has at least an optical fiber and a lens, the lens has an optical curved surface that focuses on the inside or an end surface thereof, and has a holding unit that holds the optical fiber at a position facing the optical curved surface. Further, the optical fiber is held by the holding means of the lens so that the end face is located at the focal point of the lens, so that the position adjustment of the end of the optical fiber and / or the optical axis adjustment is completed, At least it will be easier. Further, the number of components used in the optical communication module can be reduced, and highly accurate optical axis adjustment can be performed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a conventional WDM three-terminal filter module.
FIG. 2 is a sectional view of a lens in which an optical fiber holding means is integrally formed.
FIG. 3 is a configuration diagram of an optical communication module of the present invention. (Example of WDM 3-terminal filter module)
FIG. 4 is a sectional view of a lens having an optical fiber holding means.
FIG. 5 is a sectional view showing an example in which the optical fiber holding means is formed as a concave portion. (Enlarged cross section of the recess)
FIG. 6 is a sectional view of the optical communication module of the present invention. (Example of WDM 3-terminal filter module)
FIG. 7 is a cutaway view showing an example in which the optical fiber holding means is formed as a V groove.
FIG. 8 is an explanatory diagram showing an example in which a GRIN lens is applied to an optical communication module.

Claims (4)

An optical communication module, comprising at least an optical fiber and a lens, wherein the lens has an optical curved surface that focuses on the inside or an end surface thereof, and holds the optical fiber at a position facing the optical curved surface. Means, and wherein the optical fiber is held by holding means for the lens such that an end face thereof is located at the focal point of the lens. An optical communication module, having at least an optical fiber, a lens, and a spacer made of a transparent member, wherein the lens has an optical curved surface that focuses on the inside or an end face of the spacer, and the spacer includes the lens and the lens. It has holding means for holding the optical fiber on the side opposite to the side facing the lens and opposite to the lens, and the optical fiber has the end face positioned at the focal point of the lens. An optical communication module which is held by spacer holding means. 3. The optical communication according to claim 1, wherein the holding means for holding the optical fiber of the lens or the spacer is formed as a concave portion for inserting the optical fiber on the surface of the lens or the spacer. module. 3. The optical communication according to claim 1, wherein holding means for holding the optical fiber of the lens or the spacer is formed in the lens or the spacer as a V-groove in which the optical fiber is installed. module.

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