JP2003342031A - Base material for photonic crystal optical fiber and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a novel base material for a photonic crystal optical fiber having almost no limitation in length and a method for manufacturing the same. SOLUTION: A plurality of grooves 5 are formed along the longitudinal direction on the outer peripheral portion of a quartz glass rod 3 having a core 2 at an axial center portion and an inner peripheral portion of a quartz glass tube 4 combined therewith.
a and 5b are processed, and the quartz glass rod 3 and the quartz glass tube 4 are combined so that the respective grooves 5a and 5b coincide with each other. As a result, the length of the hole 5 is not limited, and the long photonic crystal optical fiber preform 1 can be easily obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photonic crystal optical fiber (PC) which enables communication of a larger capacity among optical fibers used in the field of optical communication.
F: Photonic Crystal Fiber)
The present invention relates to a base material and a method for manufacturing the same.

[0002]

2. Description of the Related Art An optical fiber capable of high-capacity and high-speed communication is indispensable for constructing an optical communication network. However, the speeding up of optical signals in recent and future optical communication networks, Along with the increase in information, there is a demand for an even larger capacity optical fiber, and as a new optical fiber satisfying this demand, an optical fiber called a so-called photonic crystal optical fiber is now drawing attention.

This photonic crystal optical fiber is a photonic crystal (PC: PC) having a uniform two-dimensional periodic structure in the longitudinal direction of the fiber as a clad covering the core.
It is an optical fiber using Photonic Crystal, and is roughly classified into two types according to the difference in the guiding principle. That is, one is a photonic band gap (PBG: Ph) in the region corresponding to the cladding.
This is a method of opening an optical band gap and confining the light wave in the core by black reflection. The other is to use the difference in the refractive index between the core and the clad as in the conventional optical fiber to make the light wave by total reflection. It is to be confined in the core.

In the latter photonic crystal optical fiber utilizing total reflection, the conventional optical fiber has a core with an additive such as germanium to make the refractive index different from that of the cladding. This is achieved by forming holes in the clad to reduce the effective refractive index. This photonic crystal optical fiber has an ultra-wide band single mode transmission region, a large effective core area, a high refractive index difference (High- △), and a large structure dispersion due to the design of the holes in the cladding. It has characteristics that cannot be realized.

In such a photonic crystal optical fiber, as shown in FIG. 2, a soot base material is deposited around the core a made of silica glass to which an additive is added by the VAD method or the like to form a clad b. After that, a plurality of holes c are formed in the clad b near the core a to make the length 20
A quartz glass base material d having a diameter of 0 mm and an outer diameter of about 25 to 50 mm is formed, and thereafter, the silica glass base material d is heated and softened in the same manner as in a normal optical fiber drawing step to obtain a predetermined fiber diameter of 100 to 100 mm. It will be obtained by drawing a line of about 150 μm.

[0006]

By the way, since the holes c of the quartz glass preform d are formed from the end face side by a mechanical grinding method or an ultrasonic machining method, the quartz glass preform d of the quartz glass preform d is formed. The length is limited, and the maximum is 20 at present.
The limit is about 0 mm.

Therefore, if the outer diameter is 50 mm, there is a drawback that the spinning cost can be about 20 km per spinning and the manufacturing cost becomes very high. Also, there is no particular problem if it is a few holes, but if the number of holes is increased to tens or more in the future or if the hole diameter is reduced, the work will take a lot of labor and time, and the manufacturing cost will be further increased. I will upload it.

Therefore, the present invention has been devised to effectively solve such a problem, and its purpose is to provide a novel base material for a photonic crystal optical fiber whose length is almost unlimited, and The manufacturing method is provided.

[0009]

In order to solve the above problems, the present invention provides a photonic crystal light having a plurality of holes extending in the longitudinal direction in a clad near a core, as set forth in claim 1. In a preform for obtaining a fiber, it is composed of a quartz glass rod having a core at the axial center and a quartz glass tube covering the periphery of the quartz glass rod, and a boundary portion between the quartz glass rod and the quartz glass tube. In addition to providing the above-mentioned holes, the holes are formed by grinding grooves on the outer peripheral surface of the quartz glass rod and the inner peripheral surface of the quartz glass tube, respectively.

The photonic crystal optical fiber preform having such a structure has the outer peripheral portion of the quartz glass rod and the inner peripheral portion of the quartz glass tube along the longitudinal direction thereof, respectively. It is possible to easily manufacture by processing a plurality of grooves by combining the quartz glass rod and the quartz glass tube so that the respective grooves are aligned.

That is, the holes formed from the end surface side by the conventional mechanical grinding method or ultrasonic machining method are
Since the groove is formed by grinding along the boundary between the quartz glass rod and the quartz glass tube, the length of the obtained base material is not limited, and the base material for long photonic crystal optical fibers is not limited. Can be easily obtained.

If the quartz glass tube is vertically divided into two or more pieces as described in claim 2, the groove processing on the quartz glass tube can be performed more easily.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 and FIG. 3 show an embodiment of a photonic crystal optical fiber preform (hereinafter simply referred to as fiber preform) 1 according to the present invention.

As shown, this fiber preform 1
Is composed of a quartz glass rod 3 having a core 2 in the axial center and a quartz glass tube 4 covering the periphery of the quartz glass rod 3, and a boundary portion S between the quartz glass rod 3 and the quartz glass tube 4. A plurality of holes 5, 5 ... (Four in this embodiment) are provided along the longitudinal direction. That is, the core 2 located at the axial center of the quartz glass rod 3 has a conventional fiber preform d as shown in FIG.
Of the core 2 and the quartz glass tube 4
Corresponds to the clad b of the conventional fiber preform d, and the core 2 and the core a, the peripheral portion of the core 2 and the quartz glass tube 4 and the clad b are made of quartz glass of the same component, respectively. Made of

The holes 5 provided along the boundary portion S between the quartz glass rod 3 and the quartz glass tube 4 respectively have outer peripheral grooves 5a formed on the outer peripheral surface of the quartz glass rod 3,
The inner peripheral groove 5b is formed on the inner peripheral surface of the quartz glass tube 4, and the outer peripheral groove 5a and the inner peripheral groove 5b are aligned at the same position as the conventional hole c by matching the positions of the outer peripheral groove 5a and the inner peripheral groove 5b. A hole 5 having a cross-sectional shape and cross-sectional area is formed.

The quartz glass tube 4 has a dividing line S2 extending in the radial direction about the axis of the quartz glass rod 3.
Can be vertically divided into two parts, and a pair of divided pipe members 4a, 4a are combined to form an internal hollow tubular body.

Next, in order to obtain the fiber preform 1 of the present invention having such a structure, first, the quartz glass rod 3 and the quartz glass tube 4 (tube member 4a) are manufactured separately, and then, As shown in FIG. 4, a spherical diamond grindstone 6 or the like is used to form a plurality of inner circumferential grooves 5b in the longitudinal direction of the inner circumferential surface of the quartz glass tube 4 at equal intervals and in parallel (in the present embodiment, 4). When processing the inner circumferential groove 5b, the grindstone 6 side may be moved in the longitudinal direction of the quartz glass tube 4, but the grindstone 6 may be fixed and the quartz glass tube 4 side may be moved. . Next, as shown in FIG. 5, a plurality of outer peripheral grooves 5a are formed in the longitudinal direction of the outer peripheral surface of the quartz glass rod 3 by using a spherical diamond grindstone 6 or the like, together with the processing of the outer peripheral groove 5a on the quartz glass tube 4. Books are formed at equal intervals and in parallel (four in the present embodiment). After that, for example, the quartz glass rod 3 is fitted into the one tube member 4a of the quartz glass tube 4 and assembled, and the quartz glass rod 3 side is rotated to accurately set the outer peripheral groove 5a and the inner peripheral groove 5b. By arranging well and then combining the other tube member 4a, as shown in FIG. 3, the fiber matrix of the present invention having holes 5 at equal intervals along the boundary between the quartz glass rod 3 and the quartz glass tube 4 is formed. The material 1 can be easily obtained.

According to such a manufacturing method, the length of the holes 5 can be formed almost indefinitely, so that it is possible to obtain an extremely long fiber which cannot be obtained by the conventional manufacturing method. The base material 1 can be easily and surely obtained. As a result, it becomes possible to continuously obtain a long-distance photonic crystal optical fiber from one fiber preform 1, and it is possible to exhibit excellent production efficiency, and to reduce the manufacturing cost of the photonic crystal optical fiber. It can greatly contribute to the reduction. Further, even if the number of the holes 5 increases or the diameter of the holes decreases, it is possible to easily cope with it by increasing the number of the grindstones 6 and processing them at the same time or changing the size of the grindstones 6. The labor and time required for the work are not significantly increased, and the manufacturing cost of the fiber preform 1 itself is lower than that of the conventional manufacturing method.

In this embodiment, the fiber preform 1 is used.
Is composed of two members, a quartz glass rod 3 and a quartz glass tube 4 combined around the quartz glass rod 3. However, as shown in FIG. 6A, the quartz glass tube 4 is further divided into an inner peripheral tube 4b and an outer peripheral tube 4c. Alternatively, the inner peripheral groove 5b may be formed on the inner peripheral tube 4b side as shown in FIG. 6B.
Further, according to the present embodiment, since the outer peripheral pipe 4c is located at the outermost periphery and acts so as to hold each member inside thereof, it is not necessary to use a special restraint means.

Further, as shown in FIG. 7, this inner peripheral tube 4b
If it is further divided (four in this embodiment), it becomes possible to perform groove processing more easily.

[0022]

EXAMPLE First, germanium was added as a dopant to the core 2 described above, and a soot base material for a single mode optical fiber was deposited on the core 2 by the VAD method.
The deposited soot base material is made into a transparent glass by a sintering furnace to manufacture a glass rod with an outer diameter of φ70 mm, and then this glass rod is rolled by a glass lathe from φ70 mm to φ15 m.
After being stretched to m, it was cut into 600 mm, and the diameter of the core 2 was confirmed by a preform analyzer. Then, the outer circumference of the glass rod having a length of 600 mm is treated with hydrofluoric acid to slightly reduce the outer diameter to less than φ15 mm, and then, as shown in FIG. Then, the outer peripheral grooves 5a were ground at equal intervals.

On the other hand, a quartz glass tube having an outer diameter of 40 mm and an inner diameter of 15 mm is vertically divided into two parts by a diamond cutter, and then, as shown in FIG. 6B, R1. After grinding two inner peripheral grooves 5b at equal intervals with a 5 mm spherical diamond grindstone 6, the processed surface is treated with hydrofluoric acid, and then, as shown in FIG.
As shown in (A), outer diameter φ80 mm, inner diameter φ40 mm
Grooves 5a, 5 in the outer peripheral tube 4c made of quartz glass.
Insert so that b matches, and then insert it with an outer diameter of 60 m
The preform 1 for a fiber of the present invention having a length of 1000 mm was manufactured by stretching to m.

Then, the fiber preform 1 thus obtained was drawn in the same manner as the conventional glass preform, and a photonic crystal optical fiber having a hole 5 with a diameter of 5 μm was formed to a length of about 200 km. Could be obtained continuously.

[0025]

In summary, according to the present invention, the portion corresponding to the clad is formed by the quartz glass rod and the quartz glass tube, and the portion corresponding to the hole is formed at the boundary between the quartz glass rod and the quartz glass tube. Since the groove is formed along with, the length of the hole is not limited, and a long base material for a photonic crystal optical fiber can be easily obtained. As a result, it becomes possible to continuously obtain a long-distance photonic crystal optical fiber from one fiber base material, and it is possible to exhibit excellent production efficiency, and to reduce the manufacturing cost of the photonic crystal optical fiber. It has an excellent effect that it can greatly contribute to the reduction.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a preform for a photonic crystal optical fiber according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a conventional base material for photonic crystal optical fiber.

FIG. 3 is a perspective view showing an embodiment of a photonic crystal optical fiber preform according to the present invention.

FIG. 4 is a conceptual diagram showing a state where an inner peripheral groove is ground on the inner peripheral surface of a quartz glass tube.

FIG. 5 is a conceptual diagram showing a state where an outer peripheral groove is ground on the outer peripheral surface of a quartz glass rod.

FIG. 6A is a perspective view showing another embodiment of the photonic crystal optical fiber preform according to the present invention. (B) is a conceptual diagram showing a state in which an inner peripheral groove is ground on the inner peripheral surface of an inner peripheral tube forming a quartz glass tube.

FIG. 7A is a perspective view showing another embodiment of the photonic crystal optical fiber preform according to the present invention. (B) is a conceptual diagram showing a state in which an inner peripheral groove is ground on the inner peripheral surface of an inner peripheral tube forming a quartz glass tube.

[Explanation of symbols]

1 Base material for photonic crystal optical fiber 2 cores 3 Quartz glass rod 4 quartz glass tube 4a Pipe member 4b inner tube 4c peripheral pipe 5 holes 5a peripheral groove 5b inner groove 6 whetstone S1 border S2 dividing line

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tatsuya Shirozawa             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor Kazumasa Ozono             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. F-term (reference) 4G021 BA00

Claims (3)

[Claims] 1. A base material for obtaining a photonic crystal optical fiber having a plurality of holes extending in the longitudinal direction in a clad near a core, and a quartz glass rod having a core at its axial center, The quartz glass rod covers the periphery of the quartz glass rod, and the holes are provided at the boundary between the quartz glass rod and the quartz glass tube, and the holes form the outer peripheral surface of the quartz glass rod and the quartz glass tube. A base material for a photonic crystal optical fiber, characterized in that each of the inner peripheral surfaces of the groove has a groove formed by grinding. 2. The preform for a photonic crystal optical fiber according to claim 1, wherein the quartz glass tube is vertically divided into two or more pieces. 3. The method for manufacturing a preform for a photonic crystal optical fiber according to claim 1 or 2, wherein a plurality of quartz glass rods and a quartz glass tube are provided along the longitudinal direction at the outer circumferential portion and the inner circumferential portion of the quartz glass tube, respectively. A method for manufacturing a preform for a photonic crystal optical fiber, which comprises processing a groove and combining a quartz glass rod and a quartz glass tube so that the grooves are aligned with each other.