JP2001154039A - Coated optical fiber, optical fiber assembly and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated optical fiber, in which the length of an optical path is controlled within range of a set value with high precision using a simple process. SOLUTION: In this coated optical fiber 10 having a core 11 and a cladding 12, the core 11 is provided with a region 21 where a refractive index is selectively changed by the change of an optically induced refractive index. Thus, the length of the optical path of the coated optical fiber is controlled to be within the range of the set value. The length of the optical path of the coated optical fiber 10 is precisely controlled by the refractive index and a length L' of the area 21, and a transmitting time is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber core and an optical fiber assembly, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with an increase in transmission capacity and an increase in transmission speed, optical fibers having characteristics such as low loss and wide band have been widely used as transmission media. In order to perform optical transmission at the same timing using a plurality of optical fibers, a plurality of optical fibers of the same type having the same length are used. Such a plurality of optical fiber cores may be used after being processed into an optical fiber assembly such as an optical fiber ribbon multi-core in a tape shape.

FIG. 7 shows a wiring sheet structure having multi-core optical fibers. The wiring sheet structure shown in FIG. 7 has a predetermined position 31 of a multi-core optical fiber 30 including eight optical fibers.
Have eight optical fiber cores 100 disassembled from the base material 20 on the sheet substrate 20, and the lengths of the optical fiber cores 100 are set to be the same. The transmission time of an optical signal is determined by the optical path length (nL), which is the product of the refractive index (n) of the core of the optical fiber and the length (L) of the optical fiber. The optical fiber 100 is used to adjust the length (L) of the optical fiber 100 to be the same and to make the optical path length (nL) the same.

[0004]

However, in practice, the physical lengths (optical fiber lengths) of a plurality of optical fiber cores vary, and the optical fiber cores 100
Due to the variation in the glass composition between the fibers and the stress when the structure of the optical fiber assembly is formed, etc.
The optical path length varies between the transmission paths of the optical fibers. As a result, the transmission time difference between the transmission paths of the optical fiber (hereinafter, this time difference (ΔT)
Is called "skew". ) Occurs. At present, even if an optical fiber ribbon with a low skew is used, the transmission time varies by about several picoseconds / m.

Conventionally, the skew of an optical fiber is mainly reduced by reducing the variation in the glass composition and by controlling the length of the optical fiber 100. Variations in glass composition can be reduced by using the same rod material. But,
In high-speed transmission of 1 terabit / second or more, it is required that the skew be 1 picosecond or less, and it is difficult to respond to this request by controlling the length.
Since the transmission time varies depending on the temperature of the optical fiber and the state of the applied stress, it is possible to adjust the skew by changing the temperature and the state of the stress. After going, it is not realistic to maintain that state. Therefore, a technique that can adjust the skew by a simple process is desired.

Further, in a wiring sheet structure in which a connector is attached to the end of a multi-core optical fiber, the optical fiber length (L) of each optical fiber core and the stress application state vary depending on the mounting accuracy of the connector. . as a result,
Since the optical path length of each optical fiber core varies, skew occurs due to the connector mounting accuracy.
In particular, in a wiring sheet structure in which a multi-core connector is attached to one end and a single-core connector or a multi-core connector is attached to the other end, it is difficult to align the mounting ends, and the mounting accuracy of the connectors deteriorates. Large wiring sheet structures are often produced.

The inventor of the present application measured the skew characteristics of the wiring sheet structure shown in FIG. 8 in order to investigate the occurrence of skew due to the connector mounting accuracy. The wiring sheet structure shown in FIG. 8 has multi-core optical fibers 30a and 30b each including eight optical fiber core wires of the same type having the same length.
The optical fiber 100 disassembled from the
Have on top. At one end of the multi-core optical fiber 30, a multi-core connector 40 (international standard IEC61754-5: type MT connecto
r), and the other end has a single-core connector 5
0 (international standard IEC61754-6: type MU connector) is attached. Each port of the optical fiber 100 is named as port numbers A1 to A16. The standard wiring length between the connectors at both ends of the wired 16 optical fiber cores 100 was 500 mm, and the optical fiber cores 100 were wired to the same length so as to reduce the skew as much as possible.

FIG. 9 shows the results of the measured skew characteristics. 9, the vertical axis represents the skew characteristic [ps], and the horizontal axis represents the port numbers (A1 to A1) of the optical fiber core 100.
A16). From FIG. 9, it can be seen that skew has occurred due to variations in connector mounting accuracy. The difference between the maximum value (A7) and the minimum value (A1 or A5) of the skew characteristics was 1.17 ps. The measurement wavelength when measuring the skew characteristic is 1550 n.
m, and the measurement accuracy was about 0.02 ps. The skew characteristics were evaluated by converting the optical path length measurement by Optical Low-Coherence Reflectometry into skew, and the device used for the measurement was manufactured by Ando Electric (AQ741).
0).

If the skew required for the wiring sheet structure shown in FIG. 8 is, for example, within 1.0 ps, the wiring sheet structure is defective. However, the port number A1
And the skew of the optical fiber 100 of A5 is 0.1
If it can be increased by 7ps or more, the port number A7
1.0ps difference from the skew of the optical fiber 100
Therefore, this wiring sheet structure can be a non-defective product. As described above, if the skew can be adjusted after the wiring sheet structure is manufactured,
Since the yield can be improved, the manufacturing cost can be significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a main object of the present invention is to control the optical path length within a set value with high accuracy by using a simple process, thereby reducing the skew. It is an object of the present invention to provide a tailored optical fiber core and an optical fiber assembly. Another object of the present invention is to provide a method for manufacturing such an optical fiber core and an optical fiber assembly.

[0011]

SUMMARY OF THE INVENTION An optical fiber core according to the present invention is an optical fiber core having a core and a clad, wherein the core has a refractive index selectively changed by a photo-induced refractive index change. Region, whereby the optical path length is controlled within a set value.

An optical fiber assembly according to the present invention is an optical fiber assembly having a plurality of optical fiber cores, wherein each of the plurality of optical fiber cores has a core and a clad, and wherein the plurality of optical fiber cores are provided. At least one of the cores has a region in which the refractive index is selectively changed by a light-induced refractive index change, thereby causing a variation in the optical path length of each of the plurality of optical fiber cores. Is controlled within the set value.

[0013] A method for manufacturing an optical fiber core according to the present invention comprises the steps of preparing an optical fiber core having a core that undergoes a light-induced refractive index change by light irradiation and a clad surrounding the core. Measuring the optical path length of the core, and changing the refractive index by selectively irradiating light to a partial area of the core so that the optical path length matches a set value. The method for manufacturing an optical fiber assembly is a method for manufacturing an optical fiber assembly having a plurality of optical fiber cores, the optical fiber core having a core that causes a light-induced refractive index change by light irradiation, and a clad surrounding the core. Preparing a plurality of wires, measuring each optical path length of the plurality of optical fiber core wires, and setting each of the plurality of optical path lengths within a set value range. Like
Changing a refractive index by selectively irradiating a part of the core of at least one of the plurality of optical fibers with light.

In one embodiment, the method further includes attaching a connector to at least one end of each of the plurality of optical fiber cores, and the step of changing the refractive index includes:
This is performed after the connector mounting step.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present inventors can control the optical path length by irradiating the core of an optical fiber core with light and causing a light-induced refractive index change in the core, thereby reducing the skew. They have found that they can be adjusted, leading to the present invention.

As described above, the optical path length (n
Since L) is the product of the refractive index (n) of the core and the length (L) of the optical fiber, the optical path length increases in proportion to the refractive index (n) of the core. Therefore, if a region having a high refractive index is formed by causing a light-induced refractive index change in a part of the core, the entire optical path length of the optical fiber becomes longer, so that the transmission time of the optical signal can be made longer. Therefore, by forming a region having a high refractive index in a part of the core, it is possible to correct the dispersion of the delay between the optical fibers and adjust the skew. Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) Embodiment 1 according to the present invention will be described with reference to FIGS. FIG. 1 schematically shows a cross section of an optical fiber core wire 10 according to the present embodiment. The optical fiber core 10 includes a core 11, a clad 12 formed around the core 11, and a coating layer 14 covering the outer surface of the clad 3. The portion composed of the core 11 and the clad 12 is referred to as an optical fiber 1
It will be referred to as 3.

In a part of the core 11, a region (light-induced refractive index change region) 21 having a length L 'in which the refractive index is selectively changed by the light-induced refractive index change is formed. Area 21
Are formed, for example, by irradiating the core 11 with ultraviolet rays. Refractive index and length L 'of formed region 21
Thus, the optical path length of the optical fiber 10 is controlled within a set value. That is, by changing one or both of the refractive index and the length L 'of the region 21, the optical path length of the optical fiber core 10 can be controlled within a set value.

FIG. 2 shows the refractive index of the region 21.
From FIG. 2, the region 21 has a refractive index (1.5
It can be seen that it shows a higher refractive index (1.545) than 40). When the optical fiber length L is, for example, 250 mm,
The optical path length of the optical fiber having the region 21 having the length L ′ of 100 mm is 385.5 mm from the following equation (I).

Optical path length = (250−100) × 1.540 + 100 × 1.545 (I) The optical path length of the optical fiber without the region 21 is 250
1.540 (core refractive index) in mm (optical fiber length L)
Is 385.0 mm, and by forming the region 21, the optical path length of the optical fiber core wire is 385.0 mm.
It can be seen that the length has increased from 0 mm to 385.5 mm.

FIG. 3 shows the relationship between the skew characteristics and the ultraviolet irradiation energy density. The vertical axis in FIG.
The change in the skew characteristic [ps] is shown, and the horizontal axis is the energy density [J / c] of the ultraviolet irradiation applied to the optical fiber.
m ² ]. FIG. 3 shows that there is a certain relationship (substantially proportional relationship) between the amount of change in the skew characteristic and the ultraviolet irradiation energy density. Therefore, the skew characteristics can be adjusted with high accuracy by controlling the ultraviolet irradiation energy. Specifically, area 2
By controlling the length L ′ of one and the ultraviolet irradiation energy density (or ultraviolet irradiation time), for example, the resolution level is set to, for example, 2.5 p with an accuracy of 0.02 ps or less.
The skew characteristic can be adjusted to about s / m.

The wavelength of the ultraviolet light applied to the optical fiber is 266 which is the fourth harmonic (4ω) of the Nd-YAG laser.
Irradiation was performed in a 100 mm section in the length direction of the fiber by moving the movable mirror. The maximum average power is 10 mW, and the pulse width is 50 ns.
Ultraviolet light operable at Hz was used. The average beam size was 2 mm in the fiber axis direction. For the purpose of evaluating the initial characteristics, the optical fiber from which the coating layer 14 was removed was irradiated with ultraviolet rays. The optical fiber core was subjected to a high-pressure hydrogen treatment of 20 MPa at room temperature for 2 weeks.

Next, details of the optical fiber core 10 according to the present embodiment will be described. Core 12 of optical fiber core 10
As the light-induced refractive index change, it is possible to use a material obtained by adding a dopant of Sn, Sn and Al, Sn and B, or Sn, Al and B in addition to Ge having the same concentration as that of the optical fiber of the normal specification. Is preferred in order to constantly increase the Here, the normal specification optical fiber is an optical fiber core to be connected to the optical fiber core 1, and such an optical fiber core has a relative refractive index difference with respect to its core. It is manufactured by doping Ge in an amount of about 0.9%. The above optical fiber core 10
In addition to the same amount of Ge (an amount that the relative refractive index difference becomes 0.9%) as the core of the optical fiber of the above-mentioned normal specification, the core 11 has a concentration of 10000 ppm or more, preferably 10 ppm or more.
000 to 15000 ppm of Sn, or such a concentration of Sn and 1000 ppm or less of Al may be co-doped. In the present embodiment, in addition to the same amount of Ge as that of the core of the optical fiber of the normal specification, Sn having a concentration of 15000 ppm and Al having a concentration of 900 ppm were co-doped. The above-mentioned doping may be performed by various known methods. For example, in the case of performing the doping by liquid immersion, the above-mentioned Sn compound (for example, SnCl ₂ .2H ₂ O) is mixed with methyl alcohol and immersed in the solution. I just need.

A coating layer 14 covering the optical fiber 13
Is formed by a single coat following the above-described drawing step of the optical fiber 13. The material for forming the coating layer 14 and the thickness of the coating layer 14 may be appropriately determined according to required conditions. For example, the elastic modulus of the optical fiber 13 (Young's modulus E), the thermal expansion coefficient (linear thermal expansion coefficient α), the temperature coefficient of the refractive index (thermo-optic coefficient ξ), and the elastic modulus (Young's modulus) of the material of the coating layer ), Thermal expansion coefficient (linear thermal expansion coefficient) and the like. Further, as a material for forming the coating layer 14, it is preferable to use an ultraviolet-curable resin having a property of transmitting ultraviolet rays. The coating layer 14 is formed by using an ultraviolet ray transmitting type ultraviolet curable resin.
Is formed, ultraviolet irradiation can be performed without removing the coating layer 14, so that a structure that prevents the strength of the optical fiber core 10 from deteriorating can be achieved. As the ultraviolet ray transmitting type ultraviolet curable resin, the photo-induced refractive index change region 21 is used.
What is necessary is to transmit at least a specific wavelength band (for example, a wavelength band of 240 nm to 270 nm) of the ultraviolet light to be applied to form the ultraviolet ray. A material that absorbs ultraviolet light having a wavelength shorter or longer than the specific wavelength band to cause a curing reaction may be used. That is,
The ultraviolet absorption characteristics vary depending on the wavelength. The coating layer 14 is formed of a resin that is of an ultraviolet transmission type in the specific wavelength band, but is an ultraviolet curing type in a wavelength range shorter or longer than the specific wavelength range. Is most preferred. As such a resin, for example, 240 n for urethane acrylate or epoxy acrylate is used.
A compound containing a photoinitiator (photoinitiator) that initiates and accelerates the curing reaction by receiving ultraviolet rays in a wavelength range shorter than m or a wavelength range longer than 270 nm may be used.

Table 1 below shows preferred examples of parameters of the optical fiber core 10 according to the present embodiment. The “secondary coating diameter” in the table means the diameter of the optical fiber 10 including the coating layer 14.

[0025]

[Table 1] The optical fiber core 10 according to this embodiment has a region 21 in which the refractive index is selectively changed, whereby the optical path length of the optical fiber core is controlled within a set value. Therefore, it is possible to manufacture an optical fiber having an optical path length controlled within a set value with higher accuracy than before, and thus it is possible to provide an optical fiber having a specified transmission time with a high yield. .

Next, a method of manufacturing the optical fiber core 10 according to the present embodiment will be described. FIG. 4 shows an optical fiber 1
0 is a flowchart showing each step of the manufacturing method No. 0.

First, an optical fiber core having a core 11 which undergoes a light-induced refractive index change by light irradiation and a clad 12 surrounding the core 11 is prepared (step S1). The core 11 of the prepared optical fiber core is co-doped with a predetermined concentration of, for example, Sn and Al in addition to Ge having the same concentration as that of the optical fiber of the normal specification, for the purpose of steadily increasing the light-induced refractive index change. It is preferred that Also, the core 11
Before selectively irradiating a part of the region with ultraviolet rays, the core 1
It is preferable to perform hydrogen filling on 1 in order to increase the photoinduced refractive index change. Specifically, the prepared optical fiber core wire may be placed in a sealed container filled with hydrogen and left at room temperature under a pressure of about 20 MPa for about two weeks.

Next, the optical path length of the prepared optical fiber core is measured (step S2). The measurement of the optical path length may be performed according to a known method. For example, Ando Electric (AQ741
Optical path length measurement can be performed by Optical Low-Coherence Reflectometry of 0).

Next, the refractive index is changed by selectively irradiating a part of the core 11 with ultraviolet rays so that the optical path length measured in the step S2 coincides with the set value.
1. A light-induced refractive index change region 21 is formed in Step 1 (Step S).
3). The set value is determined based on given specifications. The UV irradiation area (or the length L 'of the area 14) and the UV irradiation energy density (or UV irradiation time) are determined so that the optical path length of the optical fiber core matches the set value.

In the case of an optical fiber core having a coating layer 14 formed of an ultraviolet ray transmitting type ultraviolet curing resin, the coating layer 1
By irradiating ultraviolet rays (e.g., 266 nm) from above the light-receiving layer 4, the light-induced refractive index change region 21 can be formed in the core 11. Further, in the case of an optical fiber core having a coating layer 14 formed of a resin other than an ultraviolet transmission type ultraviolet curable resin, ultraviolet irradiation may be performed after removing the coating layer 14 in a region to be irradiated with ultraviolet rays. Optical fiber 1
It is also possible to adopt a method of forming the coating layer 14 after performing the step S3 for No.3. In this way, by forming the light-induced refractive index change region 21 in the core 12 of the optical fiber core, the optical fiber core 10 having an optical path length that matches the set value can be obtained. The location where the region 21 is formed is not particularly limited. It may be formed at the end of the optical fiber core 10 or at the center. Further, a plurality of regions 21 may be formed.

According to the present embodiment, the optical path length of the optical fiber can be adjusted by controlling the ultraviolet irradiation area and the ultraviolet irradiation energy density. Thus, it is possible to provide an optical fiber core whose optical path length is controlled within a set value. Therefore, when a large number of optical fiber cores are manufactured, the manufacturing cost can be reduced. (Embodiment 2) Embodiment 2 according to the present invention will be described with reference to FIGS. FIG. 5 schematically shows an optical fiber assembly 200 according to the present embodiment.

The optical fiber assembly 200 has a 32-core wiring sheet structure provided with four multi-core optical fibers 30 including eight optical fiber cores 10 on a sheet base 20. At least one core 11 of the 32 optical fiber cores 10 has a region in which the refractive index is selectively changed by the photo-induced refractive index change, whereby the 32 optical fiber cores are formed. Are controlled within a set value. That is, at least one of the 32 optical fiber cores 10 shown in FIG. 5 is the optical fiber core 10 of the first embodiment shown in FIG. The variation in the optical path length of each of the 32 optical fibers is controlled within a set value by the refractive index change region 21. Note that the content of the optical fiber core 10 of the first embodiment is omitted for simplification of description, and the following mainly describes differences from the first embodiment.

A multi-core connector 40 (international standard IEC61754-5: type MT connector) is attached to one end of the multi-core optical fiber 30, and a single-core connector 50 (international standard IEC61754-6: type MT connector) is attached to the other end. MU connector) is attached. The standard wiring length between the connectors at both ends of the 32 wired optical fiber core wires 10 is, for example, 500 mm. The sheet substrate 20 supporting the multi-core optical fiber 30 includes:
For example, it is formed of a PET material (thickness: 200 μm), the multi-core optical fiber 30 and the sheet substrate 20 are bonded using a silicone-based adhesive, and the bonding surface is, for example, a fluororesin (thickness: 50 μm). ) Is laminated.

Next, a method for manufacturing the optical fiber assembly 200 will be described. FIG. 4 is a flowchart showing each step of the method for manufacturing the optical fiber core 10.

First, a plurality of optical fiber cores 10 having a core 11 causing a light-induced refractive index change by light irradiation and a clad 12 surrounding the core 11 are prepared (step S1).
1). In the present embodiment, four multi-core optical fibers 30 are prepared. Each core 11 of the optical fiber core 10 has a predetermined concentration of, for example, Sn and Al in addition to Ge having the same concentration as that of the optical fiber of the normal specification, for the purpose of steadily increasing the photo-induced refractive index change. It is preferably doped. If necessary, it is preferable to fill the core with hydrogen before selectively irradiating an ultraviolet ray to a part of the core in order to increase the photo-induced refractive index change. In addition, for the purpose of irradiating ultraviolet rays without removing the coating layer, it is preferable to prepare the optical fiber core 10 having the coating layer 14 formed of an ultraviolet ray transmitting type ultraviolet curing resin.

Next, a connector is attached to at least one end of each of the optical fibers 10 (step S12). Specifically, a multi-core connector 4 is connected to one end of the multi-core optical fiber 30.
0 (for example, international standard IEC61754-5: type MT connector)
And a single-core connector 50 (for example, international standard IEC61754-
6: type MU connector). Next, after the multi-core optical fiber 30 (a plurality of optical fiber cores 10) to which the connectors 40 and 50 are attached is arranged on the sheet base 20, the multi-core optical fiber 30 and the sheet base 20 are bonded with a silicone-based adhesive. Then, the bonding surface is laminated with, for example, a fluororesin (thickness: 50 μm). Note that the connectors 40 and 50 may be attached to the multi-core optical fiber 30 after the multi-core optical fiber 30 is arranged on the sheet base 30.

Next, the optical path length of each of the optical fibers 10 is measured (step S13). In the optical fiber assembly 200 in which the multi-core connector 40 and the single-core connector 50 are combined, it is difficult to accurately position the optical fiber assembly 200. Therefore, the optical path lengths of the optical fiber core wires 10 often vary. The measurement of the optical path length may be performed according to a known technique. For example, Ando Electric (AQ741
Optical path length measurement can be performed by Optical Low-Coherence Reflectometry of 0).

Next, the photo-induced refractive index change region 21 is formed in the core 11 so that each of the optical path lengths measured in step S13 falls within the range of the set value (step S14). In other words, a part of the core 11 of at least one of the 32 optical fiber cores 10 is selectively provided in a part of the core 11 of the 32 optical fiber cores 10 such that each of the plurality of optical path lengths falls within the set value range. Is irradiated with ultraviolet rays to change the refractive index. Specifically, the following may be performed.

First, based on the longest optical path length among the optical path lengths measured in step S13, an optical fiber core 10 not included in the range of the set value is selected from the reference.
The set value may be determined based on the given specification.

Next, for each of the selected optical fiber cores 10, an area to be irradiated with ultraviolet rays (or a length L ′ of the area 14) and an ultraviolet ray so as to have an optical path length within a range from a reference to a set value. Determine the irradiation energy density (or UV irradiation time).

Next, under the determined conditions, ultraviolet rays (for example, 26
6 nm), thereby forming a photo-induced refractive index change region 21 in the core 11. The location where the region 21 is formed is not particularly limited. The optical fiber core 10 may be formed at a location where the optical fiber core is multi-core, or may be formed at a location where the optical fiber core 10 is disassembled.

As described above, the plurality of optical fiber cores 1
The optical fiber assembly 200 in which all the optical path lengths of 0 are within the set value range can be obtained. Note that, similarly to the first embodiment, it is preferable to fill the core 11 with hydrogen before irradiating the core with ultraviolet rays in order to increase the photoinduced refractive index change. Further, in the case of the optical fiber core wire 10 having the coating layer 14 formed of an ultraviolet transmission type ultraviolet curable resin, the ultraviolet ray can be irradiated from above the coating layer 14. After removing the coating layer 14 in the region to be irradiated with ultraviolet light,
Ultraviolet irradiation may be performed.

If the connector mounting accuracy is relatively good, or if the range of the set value required by the given specifications is not strict, step S1 is performed.
After adjusting the respective optical path lengths of the optical fiber core wires 10 according to 4, the step S12 of attaching the connector may be executed. In this embodiment, the multi-core optical fiber 3
Although 0 was used, the present invention is not limited to this, and for example, a core structure such as a tube structure (for example, a loose tube) may be used.

The optical fiber assembly 200 of the present embodiment
At least one of the cores 11 of the plurality of optical fiber cores 10 has a region 21 in which the refractive index is selectively changed by the light-induced refractive index change, whereby the plurality of optical fiber cores 10 Are controlled within a set value. For this reason, when a connector is attached to an optical fiber core, variation in the optical path length can be controlled to be smaller than variation in the optical path length determined by the mounting accuracy of the connector, and an optical fiber assembly with extremely low skew can be provided. it can. According to the manufacturing method of the present embodiment, even after the connector is attached, the optical path length of the optical fiber core can be controlled by a simple process, so that the yield of the optical fiber assembly can be improved. As a result, manufacturing costs can be reduced.

The optical fiber core 10 of the first embodiment
And the optical fiber assembly 200 of the second embodiment. That is, after preparing a plurality of optical fiber core wires 10 of the first embodiment in which the optical path length is controlled within a set value with higher accuracy than before, a connector is attached to each optical fiber core wire 10, and then a plurality of An optical fiber assembly 200 in which a region 21 is formed in at least one core of the optical fiber core 10 and the variation in the optical path length of each of the optical fiber cores is controlled within a set value.
Can also be produced.

[0046]

According to the present invention, by controlling the optical path length within the set value using a simple process, it is possible to provide an optical fiber core whose optical path length is adjusted with higher precision than before. . Further, according to the present invention, it is possible to provide a low-skew optical fiber assembly in which variations in the optical path lengths of a plurality of optical fiber core wires are controlled within a set value with a high yield using a simple process.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an optical fiber core wire 10 according to a first embodiment of the present invention.

FIG. 2 is a graph showing a core refractive index of a photo-induced refractive index change region.

FIG. 3 is a graph showing a change in a skew characteristic with respect to an ultraviolet irradiation energy density.

FIG. 4 is a flowchart illustrating a method of manufacturing the optical fiber core wire 10 according to the first embodiment.

FIG. 5 is a plan view schematically showing an optical fiber assembly 200 according to a second embodiment of the present invention.

FIG. 6 is an optical fiber assembly 20 according to a second embodiment.
9 is a flowchart illustrating a manufacturing method of the No. 0.

FIG. 7 is a plan view schematically showing a wiring sheet structure having a plurality of optical fibers.

FIG. 8 is a plan view schematically showing a wiring sheet structure having a multi-core optical fiber with connectors attached to both ends.

FIG. 9 is a graph showing a skew characteristic with respect to a port number of an optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Optical fiber core wire (optical fiber) 11 Core 12 Cladding 13 Optical fiber strand 14 Coating layer 20 Sheet base material 21 Light-induced refractive index change area 30 Multi-core optical fiber 40 Multi-core connector 50 Single-core connector 100 Optical fiber core 200 Optical fiber assembly (wiring sheet structure)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Norio Naka 3-4 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries, Ltd. Itami Works F-term (reference) 2H038 CA52 2H050 AB05X AB07X AB09X AB18X AC03 AC82 BB05Q BB07Q BB14Q BB17Q

Claims (5)

[Claims] 1. An optical fiber core having a core and a clad, wherein the core has a region in which a refractive index is selectively changed by a light-induced refractive index change, whereby an optical path length has a set value. The optical fiber core is controlled within. 2. An optical fiber assembly having a plurality of optical fiber cores, wherein each of the plurality of optical fiber cores has a core and a clad, and at least one of the plurality of optical fiber cores. The core of the present invention has a region in which the refractive index is selectively changed by a light-induced refractive index change, whereby the variation in the optical path length of each of the plurality of optical fibers is controlled within a set value. Fiber optic assembly. 3. A step of preparing an optical fiber core having a core that causes a light-induced refractive index change by light irradiation, and a step of measuring an optical path length of the optical fiber core; Selectively changing the refractive index by irradiating light to a part of the core so that the optical path length matches a set value. 4. A method for manufacturing an optical fiber assembly having a plurality of optical fiber cores, comprising: a plurality of optical fiber cores having a core that undergoes a light-induced refractive index change by light irradiation, and a cladding surrounding the core. The step of preparing, and the step of measuring the optical path length of each of the plurality of optical fiber cores, the plurality of optical fiber cores so that each of the plurality of optical path lengths falls within a set value range. Changing the refractive index by selectively irradiating a part of the core of at least one of the optical fiber cores with light to change the refractive index. 5. The method according to claim 4, further comprising attaching a connector to at least one end of each of the plurality of optical fibers, wherein the step of changing the refractive index is performed after the connector attaching step. Method of manufacturing optical fiber assembly.