JP2003029090A - Two-optical-fiber holding ferrule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical component which has superior optical characteristics and is in simple structure and a manufacturing method for the optical component. SOLUTION: The two-optical-fiber holding ferrule has a 1st-stage insertion hole part where two optical fiber tip parts are arranged coaxially in parallel and held and fixed so that bare fiber external-diameter parts are adjacent to each other and such a 2nd-stage ellipse insertion hole that the shape of a sectional through hole in a holding member communicating with the 1st-stage insertion hole of the holding part is similar to the 1st-stage insertion hole as one size shape expansion part to overall length; and two optical fiber coating line parts are provided in the 2nd-stage insertion hole in parallel and the whole holding member which holds those optical fibers is made of the same material by integral molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrule for holding an optical fiber used in optical communication and optical measuring devices.

[0002]

2. Description of the Related Art In recent years, an optical communication system that uses laser light as a transmission signal for information communication and transmits and receives various kinds of information and data at high speed via an optical fiber is rapidly spreading. Various optical devices such as an optical isolator, an optical attenuator, and an optical circulator are used in such an optical communication system. In particular, an optical fiber amplifier for amplifying an optical signal by light is suitable for high gain, low noise, and wavelength division multiplexing. It has advantages such as that it plays an important role in current optical communication technology.

The optical fiber amplifier (301) shown above is
Generally, as shown in FIG.
0, and a polarization combiner 330 part for polarization combining the excitation lights,
And WDM (Wavelength Division Mu) that multiplexes the excitation light.
Ltiplexer) module 340 part, respectively, polarization maintaining fiber 310, two optical fiber holding ferrule 350, uniaxial birefringent crystalline parallel plate 331, one optical fiber holding ferrule 351, lens 332, 343, 344, single mode optical fiber 311, The optical amplifying Er-doped fiber 312, WDM filter 341, optical isolator 342, etc.

At the same time, the optical fiber amplifier 301
In order to realize high-density mounting of optical transmission equipment and its spread, it is necessary to realize downsizing and cost reduction. The WDM module device 340 portion shown in FIG. It is miniaturized and provided in combination.

In these devices, the above-mentioned two optical fiber holding ferrules 350 are used at the introduction portion of the connecting portion. In the conventional configuration, as shown in FIG. 4 (b) and FIG. 6 which is a partially enlarged view thereof, a circular cross-sectional shape having an inner diameter hole size slightly larger than twice the optical fiber diameter (diameter for two fibers) is used. Insert the optical fiber 10 into the insertion hole 7 of the ferrule 41,
A holding structure 40 that holds two pieces of 10 'and holds them together and fixes them with another member such as an adhesive or the like, or two optical fibers 10 as shown in FIG. A combination holding structure 50 with a two-core two-hole type ferrule 51 having two independent pores has been used so that it can be held and fixed in the hole 8.

[0006]

However, the conventional combination coupling type having a circular cross-sectional shape having an inner diameter slightly larger than twice the optical fiber diameter as shown in FIG. 6 has the following problems. It was First, since the insertion hole 7 of the ferrule 41 for holding the tip end of the optical fiber strand is a hole having a circular vertical cross-section, for example, when the diameter of the optical fiber strand is 125 μ, the clearance at the time of insertion is taken into consideration. If the diameter slightly larger than twice is assumed to be 252μ, the variation in the arrangement position of the two optical fiber strands becomes large within the diameter of the insertion hole 7.

That is, as shown in FIG. 8, a circular insertion hole 7 having an inner diameter slightly larger than twice the diameter of the optical fiber.
Two optical fibers 10 and 1 arranged to be inscribed in
The 0'strand causes a slight deviation from the reference center position with respect to the central axis X of the ferrule 41 as indicated by a broken line M, and there is a great problem in positional accuracy. Also, -40 to 80
The long-term reliability heat cycle test at 500 ° C for 500 cycles could not be cleared.

Further, as shown in FIG. 4 (a), in the combined structure with the holding component 42, the wire portions of the two optical fibers 10 and 10 'are adjacently fixed in the ferrule 41 in a predetermined direction. However, when the ferrule 41 is then assembled integrally with the holding component 42 side, the ferrule 41 may be dislocated in the rotational direction and may be fixed in a twisted state.

Therefore, the optical fiber 1 has a large transmission loss due to micro-bending and a twisted optical fiber 1.
Springback causes 0 and 10 'to constantly generate strong stress in the surrounding adhesive, and the two optical fibers 10 and 10' may move a little in the holding part 41 when the heat cycle test or the like is performed. There were many.

On the other hand, as shown in FIG. 5, in the connection type having a structure having two independent insertion holes 8 and 8'so that the two optical fibers 10 and 10 'can be separately held one by one,
There were the following issues. That is, in a polarization beam combiner 70 as shown in FIG. 7, two ferrules in parallel with each other, that is, the ferrule in FIG.
As the distance between the two parallel holes of 51 becomes larger, it is necessary to increase the thickness dimension of the uniaxial birefringent crystal parallel plate 71 in the optical axis direction, which is contrary to the miniaturization and cost reduction of parts. Will end up. Furthermore, in both of the above, since the ferrule part and the holding part are separate parts that combine separate parts, the assembly accuracy as well as the number of parts,
It is also an obstacle to lowering the price in terms of the number of bonding steps.

The above-mentioned problems are common to a device having a structure in which optical elements are bonded together with an adhesive, such as an optical attenuator or an optical circulator, and an object of the present invention is to consider the above problems. An optical component having excellent optical characteristics and having a simple structure, and a method for manufacturing the optical component are provided.

[0012]

SUMMARY OF THE INVENTION The present invention is to solve the above problems, and in the invention described in claim 1, the two optical fiber element tip portions are arranged in parallel in the same axial direction, and the optical fiber elements are mutually arranged. A first-stage insertion hole having an oval in longitudinal cross-section, which penetrates in the direction of the central axis of a substantially cylindrical body that is held and fixed in a state where the wire outer diameter portions are adjacent to each other, and a holding member that communicates with the first-step insertion hole of the tip holding portion Inside, the two optical fiber covered wire portions are held in parallel, and the cross-sectional shape of the axial through hole is at least one dimension expansion portion with respect to the entire length of the through hole. And a second-stage insertion hole having an oval vertical cross section and holding these optical fibers by the insertion holes, the entire holding member is a two-fiber holding ferrule integrally formed of the same material.

That is, as shown in FIG. 2, two optical fibers
10, 10 'The tips (fiber strands) are arranged in parallel and have a structure in which they are held and fixed in close contact with each other,
The cross-sectional shape of the insertion hole 6 that penetrates the holding portion that serves as the ferrule has an oval oval shape as shown in FIGS. 2 (a) and 9, and the entire ferrule holding member 1 has the same integral shape. It is made of a material.

According to the second aspect of the invention, the shape of the communication hole between the first-stage insertion hole and the subsequent oval second-stage insertion hole similar to the first-stage insertion hole, which is the enlarged dimension and shape, is formed. However, the two ferrules for holding two optical fibers which are continuous insertion holes having an oval shape in vertical cross section, which are connected by an R-shaped taper surface having a curvature in the axial direction, are used.

As shown in FIG. 2 (b), the cross-sectional shape of the penetrating insertion hole is similar to that of a longitudinal cross section of a similar shape in which at least two different caliber sizes are connected in the entire axial length. By making a continuous communication hole consisting of
It is possible to prevent the two optical fibers from being twisted in a twisted shape at the time of insertion as well as after the insertion. Therefore, microbending due to twisting does not occur, and strong springback due to twisting disappears, so that heat cycle tests and the like can be performed. Even if it goes, the two optical fibers do not move inside the holding component.

Further, in order to prevent microbending due to bending of the optical fiber, it is preferable that the bending radius of curvature of the optical fiber core portion is not less than 30 mm. Specifically, as shown in FIG. 2 (b), the distance between the optical fiber coating end portion A and the position B at which the optical fiber bare wire portion that first contacts the wall surface of the inner diameter insertion hole of the ferrule for holding two optical fibers. Is about 2 mm or more, the desired radius of curvature or more can be maintained.

Further, in the third and fourth aspects of the present invention, the entire holding member for holding the optical fiber is integrally molded with a sintered body having a metal composition or a ceramic composition such as alumina or zirconia.
This is a holding ferrule.

As described above, by integrally molding and using the same material, the number of parts is reduced, the bonding and assembling work is reduced, and the cost can be reduced. In addition, the accuracy of parts is also improved.
As a method of integrally molding, there are a general ceramics injection molding method and a MIM (Metal Injection Mold) method.
In the IM method, a resin binder is added to a metal powder and kneaded to obtain a low-viscosity state that allows injection molding, and injection molding is performed in a mold.
After taking out, after performing a degreasing process for removing the resin binder, main sintering is performed.

According to a fifth aspect of the invention, there is provided an optical communication / optical measurement device using the above-mentioned two optical fiber holding ferrules. As a result, it is possible to improve the accuracy and reliability of the ferrule for holding the optical fiber of the conventional type, and to reduce the cost.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION [Examples] The two-fiber-holding ferrule according to the present invention will be described in detail below with reference to Examples. It should be noted that the structure of the drawings is schematically shown to the extent that the invention can be understood, and is not limited to the illustrated example of the outer shape of the present invention. First, the integral sintering manufacturing process by the MIM method will be described below as an example of the manufacturing method. As the material itself, in addition to stainless steel containing a metal material, a general alumina and zirconia-based ceramic material is used. It does not matter if it is used in injection molding.

First, stainless steel SUS304L is used as an example of a metal material for forming the ferrule body. In order to make this metal material into a powder form, 2-8 by atomizing method
Spherical powder of about μm is added, and a resin binder is added and kneaded sufficiently. This is injected into the metal mold by injection of the above material into a metal mold in which the final shape of the sintered shape is finished as shown in FIG. 1, and then the molded body is taken out from the metal mold to remove the resin binder. Degreasing treatment was performed and further main sintering was performed.

The sintered body generally shrinks during the main sintering, but since the shrinkage rate is almost proportional to the size of the product, the shape of the ferrule for holding two optical fibers of the present invention is inserted. The hole size is 125 μm in the minor axis width direction and 2 in the major axis width direction.
Sintering can be performed accurately with a small dimensional size of about 50 μm. Therefore, by the MIM method, it is possible to manufacture a ferrule for holding two optical fibers, which has a longitudinal cross-sectional oval shape of a similar shape having different through-dimensions in the through-hole cross-sectional shape over the entire length.

After the main sintering, the two optical fibers were passed through the insertion holes of the ferrule, and the optical fiber and the ferrule were fixed with an adhesive. Then, the ferrule tip and the optical fiber end were inclined and optically polished. The AR mirror (non-reflective coating) treatment was applied to the finished edge mirror surface to complete the process.

A polarization combiner of the type shown in FIG. 7 was actually manufactured using this, and a temperature cycle test of −40 ° C. to 80 ° C. was carried out. As a result, there was no deterioration in insertion loss and optical components with stable characteristics. was gotten.

The greatest advantage of the present invention is an effect which cannot be obtained with the conventional type in which two holes are inserted into a normal circular insertion hole. It is in a structure for holding two optical fiber strands toward the longitudinal center of the oval through hole. That is, as shown in FIG. 9, when the elliptical insertion holes 6 are arranged adjacent to each other in the major axis direction, the centers of the two optical fiber cores and the major axis (X) of the elliptical insertion holes 6 are always on the same line. Can be located in.

For example, while the optical fiber strand is 125 μ, the oval insertion hole 6 has a width dimension of 126 μ on the minor diameter side and a width dimension of 252 μ on the major diameter side, while the long axis of the two inserted optical fibers (X ) And the center of the optical fiber strand are not misaligned.

Further, the adjoining state of the optical fiber tips in the major axis direction is such that the hole shape has a curvature in the axial direction at the communicating portion with the oval second step insertion hole similar to the first step insertion hole described above. It is always held constant by the continuous insertion hole inner peripheral wall surface shape of the longitudinal cross section oval which is connected by the R-shaped tapered surface. Its structure is as follows.

As shown in FIG. 2B, the cross-sectional shape of the insertion hole continuing from the first stage to the second stage, the optical fiber coating end portion A and the optical fiber bare wire portion extending from the end portion A are covered. The distance from the position B that first contacts the wall surface of the inner diameter hole of the ferrule for holding the optical fiber is set to about 2 mm, the optical fiber wire extending to the tip is bent at the position B in the figure, and a gentle curve is drawn to draw the other side of each other. It is placed so that it touches the optical fiber side while applying a slight bending.

As a result, at the centers of the adjacent optical fiber strands, a force is always exerted in the direction in which the two fibers are in contact with each other on the central axis in the major axis direction of the ellipse, so that the distance between the cores of the optical fibers is reduced. It is possible to maintain the axial direction with high accuracy and at all times.

Thus, the diameter of the conventional optical fiber is 2
Like a ferrule with a circular cross-sectional shape that has an inner diameter hole size slightly larger than double (diameter for two), one of the two fibers is misaligned or rotated with respect to the axial center position of the circular hole. There is no occurrence of microbending due to twisting in the direction. Further, even in the heat cycle test, the two optical fibers do not move largely in the holding portion, so that reliability and quality are always stable.

Further, since the two optical fiber tips have a structure in which they are fixed in a state in which they are aligned in parallel and adjacent to each other, in the polarization combiner as shown in FIG. 7, for example, the optical axis of a parallel plate made of a uniaxial birefringent crystal The thickness in the direction can be made shorter than before.

[0032]

As described above, according to claim 1 of the present invention, a ferrule capable of holding and fixing two optical fiber tips in the same axial direction in parallel with each other while closely adhering to each other on the central axis. A tip insertion hole structure is obtained.

When this is viewed from the side of the optical fiber insertion port, the cross-sectional shape of the through hole communicating to the oblong holding portion at the tip of the ferrule has an oval shape similar to that of the holding portion inserting hole. Since the ellipses are connected to each other in a narrowed shape, the two optical fibers can be sequentially fed into the curved tapered hole having no step and can be positioned in a predetermined arrangement while always maintaining the mutual positional relationship. Furthermore, after the insertion is completed, the optical fiber coating portion can be easily fixed to the ferrule holding member side by filling the base portion of the ferrule on the insertion port side with an adhesive.

According to the second aspect of the present invention, the through-hole cross-sectional shape is a continuous insertion hole having an oval cross-sectional shape of two different diameters over the entire length in the axial direction. It is possible to prevent twisting of the two optical fibers in a twisted shape. Therefore, microbending due to twisting does not occur, and large springback due to twisting disappears, and even if a heat cycle test is performed, the two optical fibers do not move inside the holding component.

Further, in order to prevent the bending radius of curvature of the optical fiber core from becoming 30 mm or less, the position where the optical fiber coating end portion and the optical fiber bare portion extending from the optical fiber core portion first come into contact with the inner diameter wall surface of the ferrule for holding two optical fibers. The distance between and is about 2 mm or more, and the optical fiber wires are placed in the insertion hole so that they are in contact with each other while drawing a gentle curve, so microbending can be prevented and the center position accuracy is further improved. be able to.

According to the third aspect of the present invention, the entire holding member for holding the optical fiber is integrally formed of a ceramic sintered body of alumina or zirconia composition.
Individual manufacturing costs for separate parts can be omitted, the number of parts can be reduced, adhesive assembly work can be eliminated, and cost can be reduced. In addition, even in connection with other parts, the parts accuracy of the connecting portion is improved.

Further, in the invention according to claim 4, it is possible to improve the accuracy and reliability and to reduce the cost as compared with the conventional assembly-type coupling ferrule for holding an optical fiber, which contributes to the high performance of optical communication equipment and the like. be able to.

In summary, the effects of the present invention are summarized as follows: the cross-sectional shape of the insertion hole penetrating through the ferrule is a continuous hole having an oval cross-sectional shape with two different diameters over the entire axial length. As a result, it is possible to prevent the two optical fibers from being twisted in a twist shape after the insertion. Therefore, microbending due to twisting does not occur, and springback due to twisting is eliminated, so that even if a heat cycle test is performed, the two optical fibers do not move inside the holding component.

Further, since the ferrule is integrally molded and made of the same material, the number of parts is reduced, the bonding and assembling work is eliminated, the cost can be reduced, the parts accuracy is improved, the optical characteristics are excellent, and the structure is improved. An optical component that is easy to obtain can be obtained.

Another advantage of the present invention is that when the ellipses are arranged adjacent to each other in the major axis direction, the core centers of the two optical fibers and the major axis of the ellipse are located on the same line,
And springback in the bending direction of the optical fiber,
Adjacent bare fibers always exert a force in a direction in which the two fibers are in contact with each other at the central axis in the longitudinal direction, so that the distance between the cores of the optical fibers can be accurately maintained and the opposing axial directions can be always maintained.

Therefore, like a conventional ferrule having a circular cross-sectional shape having an inner diameter hole size slightly larger than twice the diameter of the optical fiber (diameter for two), two fibers are provided with respect to the axial center position of the circular hole. There is no occurrence of microbending due to axial misalignment or twisting in the direction of rotation in one of the fibers. Of course, even in the heat cycle test,
Since the two optical fibers do not move in the holding part,
Quality is stable.

[Brief description of drawings]

FIG. 1 is an optical fiber 2 showing an example of an embodiment of the present invention.
It is the schematic which shows the internal structure of this holding ferrule.

FIG. 2 is an optical fiber 2 showing an example of an embodiment of the present invention.
It is a partially expanded schematic diagram which shows the internal structure of this holding ferrule.

FIG. 3 is a schematic diagram showing a configuration of an optical fiber amplifier.

FIG. 4 is a schematic diagram showing the structure of a conventional two-fiber holding ferrule.

FIG. 5 is a schematic diagram showing another structure of a conventional two-fiber holding ferrule.

6 is a partially enlarged schematic view showing the structure of the conventional two-fiber-holding ferrule of FIG.

FIG. 7 is a schematic diagram showing a configuration of a polarization beam combiner.

8 is a partially enlarged schematic view showing a structure of a holding portion of the conventional two-fiber holding ferrule of FIG.

FIG. 9 is a partially enlarged schematic view showing a holding part structure of the ferrule holding two optical fibers of the present invention of FIG. 2 (a).

[Explanation of symbols]

1, 41, 51, 73, 74 ferrules 2, 2'optical fiber 3 Adhesive part 6, 7, 8 insertion holes 10, 10 'optical fiber strand 42, 52 holding parts 43, 53 guide 70 Polarizer 71 Uniaxial birefringent crystalline parallel plate 72 lens 75, 76, 77 optical fiber

Claims (6)

[Claims] 1. A longitudinal section that penetrates in the direction of the central axis of a substantially cylindrical body in which the tips of two optical fiber strands are arranged parallel to each other in the same axial direction, and the outer diameter portions of the optical fiber strands are held and fixed to each other. The two optical fiber coated wire portions are held in parallel inside a first-stage insertion hole having an oval surface and a holding member communicating with the first-step insertion hole of the tip holding portion, and a cross section of the axial through hole. The shape has at least one dimensional shape enlarged portion with respect to the entire length of the through hole, and a second step through hole having a vertical cross section of an oval with a similar shape to the first step through hole, and these optical fibers are inserted into the through hole. A ferrule holding two optical fibers, characterized in that the whole holding member held in (1) is made of the same material by integral molding. 2. The communicating hole shape of the first-stage insertion hole and the subsequent oval second-stage insertion hole similar to the first-stage insertion hole, which is the enlarged dimension and shape, and has a curvature in the axial direction. The ferrule holding two optical fibers according to claim 1, wherein the ferrule is a continuous insertion hole having an oval shape in vertical cross section, which is connected by an R-shaped tapered surface. 3. The holding member for holding the optical fiber as a whole is a sintered body made of a resin binder kneaded material containing metal fine powder as a main raw material, and is integrally molded. Item 2. A ferrule that holds two optical fibers according to Item 2. 4. The holding member for holding the optical fiber as a whole is a sintered body made of a ceramic composition containing alumina or zirconia as a main raw material, and is integrally molded. A ferrule that holds two optical fibers as described in 2. 5. The ferrule for holding the optical fiber is an injection molding method (injection molding method).
The optical fiber holding ferrule according to any one of claims 1 to 4, wherein the ferrule has two optical fibers. 6. An optical communication system using the optical fiber holding ferrule according to any one of claims 1 to 5.
Optical measuring device.