Patent Grant
8915100
The present application is based on Japanese Patent Application No. 2010-218026, filed on Sep. 29, 2010, the entire contents of which are hereby incorporated by reference.
1. Technical Field
The present invention relates to an optical fiber end processing method and an optical fiber end processing apparatus for processing an end of an optical fiber having a plurality of holes around a core part.
2. Description of the Related Art
In recent years, a new optical fiber is focused, which is called a holey fiber or a photonic crystal fiber having a plurality of holes around a core part, and a broad application of the new optical fiber to an optical code for communication and an optical device, etc., is examined (for example, see patent document 1).
When the holes 4 formed on the clad part 3 are opened on an end face of the holey fiber 1, moisture enters into the holes 4 or condensation occurs inside the holes due to temperature variation, thus reducing a mechanical strength of the holey fiber 1 or generating a fluctuation of optical characteristics in some cases.
Further, when optical fibers are connected to each other, using a connecting member such as a mechanical splice or a MT connector, etc., a method of reducing a reflection on a connection end face and a connection loss by filling an interspace between a connection end face of one of the optical fibers and a connection end face of the other optical fiber, with a liquid refractive index matching material. When this connection method is applied to the holey fiber 1 as shown in
Further, in a single-core optical connector which requires no refractive index matching material, there is a problem that when the connection end face of the holey fiber 1 is polished, an abrasive or a polishing debris that enters into the holes 4 goes outside after polishing and is caught by the connection end face, thus damaging the fiber end face or deteriorating the optical characteristics due to an interspace generated in this part.
In order to cope with this problem, conventionally the following technique is proposed.
Patent document 1 describes a method for closing pores (holes) of a photonic crystal fiber end, by a closing material with lower refractive index than that of the core part.
Patent document 2 describes a method for collapsing hollow parts (holes) of the optical fiber by heating the optical fiber end and softening the clad part, or a method for sealing the hollow parts by filling the hollow parts with resin, as a method for sealing the hollow parts (holes) of the optical fiber.
Patent document 3 describes a method for melting and closing the holes by arc discharge applied to a position away from the end face of the optical fiber.
The method for sealing the holes by melting the optical fiber itself having the holes by heating described in the patent document 2, has an advantage that there is no problem of aging deterioration, because moisture, etc., is completely prevented from entering into the holes, compared with the method for sealing the holes using the closing material made of resin described in patent document 1. However, the method for melting the end of the optical fiber has a problem that a shape of a core is disturbed and optical loss is easily generated; when a cantilever optical fiber end is heated, a heated portion is bent or expanded due to unbalance of surface tension in a peripheral direction of the optical fiber in a molten state, thus making it difficult to obtain a desirable shape; and the optical fiber end is expanded and is hardly enter into a hole of a ferrule for connector.
Further, according to patent document 3, it is important that two parts of the optical fiber end are respectively fixed to V-grooves, thus enhancing positional accuracy between two V-grooves and suppressing axial shift or angular deviation of the optical fiber between V-grooves as much as possible, so that the bending of the closing part of the holes due to heating and melting is suppressed to be small. However, even if the positional accuracy is enhanced between two V-grooves, there is a problem as follows. Although the optical fiber is placed on the V-groove after coating is removed, there is a possibility that a minute coating refuse remains on a surface of the optical fiber. Then, such a coating refuse adheres to the V-groove portion or a V-groove presser, and the positional accuracy of the optical fiber by a V-groove component is deteriorated, thereby generating deformation and bending of the hole closing part of the optical fiber. Further, not only the coating refuse but also dust floating in the air, and fibers of a cotton-swab for cleaning can also have an adverse influence. In addition, slight deformation and bending are generated in the hole closing part of the optical fiber when being heated and melted, due to incompleteness of the accuracy of the V-groove itself and the V-groove presser, thus inevitably generating a variation in the loss of the optical fiber.
Note that as the method for sealing the holes of the holey fiber, it can be considered that a general optical fiber is fusion-spliced to the connection end face of the holey fiber. However, in this method, the axial shift or angular deviation, and expansion are easily generated in a fusion-spliced part. When such axial shift, angular deviation and expansion are generated, it is difficult to fit the holey fiber into the ferrule, and a surface of the holey fiber is easily damaged during the fitting work, thus posing a problem in workability and reliability. Further, loss in a fusion-spliced part between the holy fiber and the optical fiber is easily excessively generated, if compared with the method for heating and melting the optical fiber between V-grooves described in the patent document 3.
An object of the present invention is to provide an optical fiber end processing method and an optical fiber end processing apparatus, capable of largely reducing an increase of a loss due to incompleteness of positioning of an optical fiber.
According to an aspect of the present invention, there is provided an optical fiber end processing method, for processing an end of an optical fiber comprising a core part; a clad part surrounding an outer periphery of the core part; and a plurality of holes formed along an axial direction of the core part around the core part in the clad part, the optical fiber end processing method comprising:
an optical fiber fixing step of fixing two parts of the optical fiber;
a first heating step of heating a tip end side part of the optical fiber between two fixed parts fixed in the optical fiber fixing step, and melting the optical fiber of the tip end side heating part, after the optical fiber fixing step;
a second heating step of heating a part on a base end side of the optical fiber between the two fixed parts away from the tip end side heating part in a state that the two fixed parts of the optical fiber are fixed, and making the holes of the optical fiber disappear, after the first heating step; and
a removing step of removing the tip end side heating part after the second heating step.
As an optical fiber end processing apparatus that executes the optical fiber end processing method, it is preferable to use an optical fiber end processing apparatus comprising:
a fiber fixing unit that fixes two parts of the optical fiber;
a heating unit that heats the optical fiber; and
a control unit that controls a heating operation by the heating unit for heating a different part of the optical fiber between the fixed parts at two parts fixed by the fiber fixing unit.
According to other aspect of the present invention, there is provided an optical fiber end processing method, for processing an end of an optical fiber comprising a core part; a clad part surrounding an outer periphery of the core part; and a plurality of holes formed along an axial direction of the core part around the core part in the clad part, the optical fiber end processing method comprising:
a fiber fixing step of fixing the optical fiber and a supporting fiber in a state that each end face is opposed to each other;
a first heating step of heating the optical fiber and the supporting fiber, and fusion-splicing the optical fiber and the supporting fiber, after the fiber fixing step;
a second heating step of heating a part of the optical fiber positioned between a fixed part of the optical fiber and the fusion-spliced part, away from the fusion-spliced part, in a state that the optical fiber and the supporting fiber are fixed, and making the holes of the optical fiber disappear, after the first heating step; and
a removing step of removing the fusion-spliced part after the second heating step.
As an optical fiber end processing apparatus that executes the optical fiber end processing method, it is preferable to use an optical fiber end processing apparatus comprising:
a fiber fixing unit that fixes the optical fiber and the supporting fiber respectively;
a heating unit that heats the optical fiber and the supporting fiber; and
a control unit that controls a heating operation by the heating unit for heating a different part of the optical fiber and the supporting fiber fixed by the fiber fixing unit.
An embodiment of an optical fiber end processing method and an optical fiber end processing apparatus according to the present invention will be described hereafter.
Note that the optical fiber of the present invention may be the optical fiber having a plurality of holes formed along the axial direction of the core part around the core part, and a holey fiber and a photonic crystal fiber, etc., correspond thereto. The optical fiber (holey fiber) having a hole structure of
Similarly to other optical fiber, the holey fiber is used in a state that resin coating is applied thereto. However, the coating needs to be removed in a case of a fiber connection or an optical component connection. When the holes 4 of the holey fiber 1 are closed and sealed, first, a resin coating 5 of a resin coated holey fiber 6 is removed to obtain the holey fiber 1 in a bare state, and as shown in
Next, as shown in
Next, the holey fiber 1 between the V-grooves 11, 11 is melted by electric discharge heating. The electric discharge heating is performed by arranging a pair of discharge electrodes 15, 15 in the interspace 13 for example. A discharge plasma region 16 is formed between the discharge electrodes 15, 15, and the holey fiber 1 in the discharge plasma region 16 is heated. A discharge circuit equivalent to that of a commercially available fusion splicer may be connected.
First, as shown in
At this time, if rubbish or dust generated in the resin coating 5, etc., removed from the resin coated holey fiber 6, adheres to the V-groove 11 or the V-groove presser 14, the holey fiber 1 is grasped by the V-grooves stages 12, 12 at both sides of the holey fiber 1 in a state that the axial shift and angular deviation are generated, and therefore a stress is generated in the holey fiber 1 (further, the axial shift and the angular deviation are also generated due to incompleteness of the accuracy of the V-groove itself of the V-groove stage 12 and the V-groove presser 14 in some cases). Therefore, the heating and melting part of the holey fiber 1 by discharge heating is deformed so that the stress of a non-melting part is relaxed. After sufficient heating and relaxing the stress, electric discharge is stopped.
Such a deformation of the heating and melting part will be further described, using an explanatory view of a processing principle of
Next, as shown in
In a first heating and melting zone A, being a first heating part, large deformation occurs when a fiber fixing state is poor due to the axial shift between fixing parts of the hole fiber 1, and a large loss is generated when light is passed therethrough. Meanwhile, in a second heating and melting zone B, being a second heating part, the holey fiber 1 is straight and the stress is not generated, and therefore almost no deformation such as bending occurs even if the holey fiber 1 is heated and melted, excluding disappearance of the holes 4 of the holey fiber 1 and reduction of a diameter of the holey fiber 1.
In addition, electric discharge heating can be automatically executed by providing a control unit 17 that controls an electric discharge heating operation for heating a different part of the optical fiber 1 between the V-grooves 11 and 11 at two places fixed by the V-groove component 10, by electric discharging electrodes 15, 15, and by setting an operation program in the control unit 17 for continuously executing the electric discharge heating operation twice as described above.
Next, as shown in
When the holey fiber 1 is fitted into the ferrule of the connector, a discharge position is set so that a length from a coating edge of the resin coating 5 of the resin coated holey fiber 6, to the second heating and melting zone B is set to a defined value. The reason why the first heating and melting zone A is removed, is that if the deformed first heating and melting zone A exists, the holey fiber 1 cannot be inserted into a fiber guide hole in the ferrule.
In a mechanical splice and the connector attached on-site with the mechanical splice incorporated therein, the second heating and melting zone B of the holey fiber 1 is preferably set as a connection end face. Therefore, when the holey fiber 1 is applied to the mechanical splice and the connector of site attachment with the mechanical splice incorporated therein, the holey fiber 1 is preferably cut at a position of the second heating and melting zone B where the holes 4 disappear. However, there is no inconvenience particularly in cutting the holey fiber 1 at a position between the first heating and melting zone A and the second heating and melting zone B, while the holes 4 remain on the connection end face of the holey fiber 1. In a case of a liquid matching agent, the air enclosed in the holes 4 comes out on the connection end face at a high temperature, thereby involving a problem that an adverse influence is given thereto. However, such an adverse influence can be prevented by applying the matching agent to the end face of the holey fiber 1 and excluding the air in the holes 4 by heating with warm air, as pre-processing of the connection.
Note that in the second discharge heating shown in
The fine moving mechanism is a mechanism capable of sliding the optical fiber between the V-grooves without axial shift, and is employed by all commercially available fusion splicers for an optical fiber ribbon, and almost all non-alignment type fusion splicers for a single optical fiber, which is an existent technique.
Further, in the aforementioned embodiment, preferably the first heating and melting zone A and the second heating and melting zone B are not overlapped on each other. This is because since the first heating and melting zone A is deformed in a certain length range, when a part of the second heating and melting zone B is overlapped thereon, the second heating and melting zone B is slightly affected by the deformation of the first heating and melting zone A at a second melting time. Further, instead of changing the position of the discharge electrodes 15, 15, independent discharge electrodes are disposed at each position, and the electric discharge may be caused as needed by switching the electrodes.
Further, when the discharge heating is performed by using a normal fusion splicer, the holes 4 can be closed or sealed by a length of about 0.5 mm. Longer length of the closing part may sometimes contribute to improving a yield rate in a connectorizing work. In order to increase the length of the closing part in the aforementioned embodiment, for example, the discharge electrode 15, 15 may be moved in a right direction of
Note that if the discharge heating is continued while moving the discharge electrodes, and the electric discharge is weakened in a middle, to stop a melting operation, such a discharge heating is substantially equivalent to the discharge heating performed twice.
Further, the discharge plasma region 16 may be expanded and heated without moving the discharge electrodes 15, 15. In this case, it is effective to expand an interval between a pair of discharge electrodes 15, 15, and shift the discharge electrodes 15, 15 in a vertical direction to a paper face of
Note that non-patent document 2 published by the Optical Society of America (OSA) describes the fusion splicing technique using two pairs of discharging electrodes. Further, explanation is given heretofore on the assumption that the single optical fiber is processed. However, regarding a fiber ribbon obtained by making a plurality of holey fiber into a ribbon, the aforementioned processing can be executed by completely the same method only by increasing the number of V-grooves. At this time, all holey fibers need to be uniformly heated, and this is a publicly-known technique already realized by the fusion splicer. Regarding the fiber ribbon, the method using two pairs of discharging electrode is described in non-patent document 2, and a method of using a pair of discharge electrode is described in non-patent document 3.
According to a second embodiment of the present invention, the holey fiber end processing is performed, using the supporting fiber other than the holey fiber.
First, as shown in
Although the fusion splicer has a system in which the resin coating part is directly attached to the fine moving base, explanation is given here for a case that the resin coating part is attached to the fiber holders 20, 20 of the fusion splicer, and thereafter is attached to the fine moving base. The resin coating part 5 of the holey fiber 1 and the resin coating part 8 of the supporting fiber 7 are respectively attached to the fiber holder 20. A fiber stopper 22 is formed in the fiber holder body 21 of the fiber holder 20, and positioning of the coating edge is performed by making the coating edge of the fiber ribbon coating parts 5, 8 brought into contact with the fiber stopper 22. Designation mark 23 indicates a fiber clamp for pressing the resin coating parts 5, 8 to the fiber holder 20. In a state immediately after attaching both fibers 1, 7 to the fiber holder 20, as shown in
Thereafter, as shown in
Next, as shown in
Thereafter, as shown in
A moving operation of the discharge electrodes 15, 15 of this embodiment is enabled by a commercially available fusion splicer with aligning function. The fusion splicer with aligning function has a function of so-called sweep discharge, and by using this function, the discharge electrodes 15, 15 are reciprocated after fusion splicing, so that heating processing can be performed. Further, the discharge heating operation of this embodiment can be automatically executed by the fusion splicer by slightly changing an operation program of the fusion splicer. Expansion of the hole disappearance region (fiber heating and melting zone E) can be easily realized by similarly changing the operation program, by heating the holey fiber 1 while shifting the discharge electrodes 15, 15, when the second holey fiber 1 is discharge-heated. The positional information of the resin coating edge of the resin coating part 5 is already known by the fusion splicer by providing the fiber stopper 22 in the fiber holder 20, and therefore a length from the resin coating edge to a center of the fiber heating and melting zone E can be accurately controlled. Further, in a commercially available optical fiber cutter, cut operation can be performed in a state that the fiber is fitted into the fusion splicer, and therefore a highly accurate cut position can be obtained.
Note that in the description of the first and second embodiments, explanation is given for a case that the electric discharge is used for heating the optical fiber. However, a carbon dioxide laser and a carbon heater can also be used as a heat source, other than the electric discharge. Further, the optical fiber end processing method of the present invention is capable of suppressing the increase in the loss while keeping high reliability, and can be applied not only to a single fiber but also to multi-fiber connectors and splices, and can contribute to various utilization hereafter, such as holey fiber and photonic crystal fiber having holes.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-218026 | Sep 2010 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5321790 | Takahashi et al. | Jun 1994 | A |
| 6868213 | Sasaoka et al. | Mar 2005 | B2 |
| 20020159734 | Sasaoka et al. | Oct 2002 | A1 |
| 20060062533 | Hachiwaka et al. | Mar 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 2002323625 | Nov 2002 | JP |
| 2004004320 | Jan 2004 | JP |
| 2005024849 | Jan 2005 | JP |
| Entry |
|---|
| Machine translation of JP 2005024849, Optical Fiber Connector, Kurosawa et al., Jan. 27, 2005. |
| Masao Tachikura, Fusion mass-splicing for optical fibers using electric discharges between two pairs of electrodes, Applied Optics, vol. 23, No. 3, pp. 492-498 (Feb. 1984). |
| Masao Tachikura and Norio Kashima, Fusion mass-splices for optical fibers using high-frequency discharge, IEEE/OSA Journal of Lightwave Technologh, vol. LT-2, No. 1, pp. 25-31 (Feb. 1984). |
| Number | Date | Country | |
|---|---|---|---|
| 20120073330 A1 | Mar 2012 | US |
