JP2882908B2 - Image fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fiber formed by bundling a large number of optical fibers, and to an image fiber capable of increasing its density.

[0002]

2. Description of the Related Art Conventionally, an image fiber using a silica-based optical fiber has been widely used in industrial and medical fields. FIG. 2 shows an example of such an image fiber.
The following are known. This image fiber 1 comprises a core 2, a clad 3, and a jacket 4.
A plurality of optical fibers 5 having a layer structure are aligned and spun. Here, the core 2 forming the optical fiber 5 is made of pure quartz, the clad 3 is made of quartz glass doped with F or B ₂ O ₃ , the jacket 4 is made of pure quartz, and the cladding of the optical fiber 5 is formed by spinning. The cross section of the jacket 3 and the jacket 4 is hexagonal.

[0003]

However, the jacket 4 which is the third layer following such a core and a clad.
However, the image fiber using the optical fiber having the above disadvantage has a disadvantage that the pixel interval becomes large due to the jacket 4 and the density cannot be increased, and the flexibility is inferior. In addition, the jacket 4 is not only optically unnecessary, but also has a problem that unnecessary light propagates and causes a noise component.

The reason why such a jacket 4 must be provided is that the difference in viscosity between the glass forming the core and the glass forming the cladding increases, and when the image fiber is spun without the jacket, bubbles are generated and the yield is reduced. This is because it becomes extremely bad. That is, F and B ₂ O ₃ doped in the cladding have the effect of lowering the refractive index and lowering the viscosity, and when SiCl ₄ is used as a glass material for the cladding, This is because Cl having an effect of lowering the viscosity is also contained.

The present invention has been made in view of the above circumstances, and has as its object to provide an image fiber which does not require a jacket, can be reduced in diameter and density, and has improved flexibility. .

[0006]

Means for Solving the Problems] image fiber of the present invention, a 1-2% by weight of Cl, 0.1 wt% or less of F
And a clad made of quartz glass doped with B ₂ O ₃ and / or F that does not contain Cl and reduces the viscosity of the core during melting.
Optical fiber that reduces the viscosity difference between the core and clad during melting by suppressing the decrease in viscosity during melting of the clad.
The configuration using a bar is a means for solving the above problem.

[0007]

According to the image fiber of the present invention, the core is made of quartz gas.
With use of the lath, by using F and / or B ₂ O ₃ doped quartz glass is a dopant having an effect of lowering the refractive index in the cladding, to give the desired refractive index difference, also lowering the viscosity to core effect Doping with C1 and F, which are dopants having the following, lowers the viscosity of the core and suppresses the decrease in the viscosity of the clad by making the clad not contain C1, thereby reducing the difference in viscosity between the core and the clad. It is. This makes it possible to use an optical fiber that does not require a jacket when manufacturing an image fiber, and to obtain an image fiber having a two-layer structure including only a core and a clad.

Further, by using an alkoxysilane such as Si (CH ₃ O) ₄ or Si (C ₂ H ₅ O) ₄ as a glass material for forming the clad, a clad containing no Cl can be formed. This is preferable because the lowering of the viscosity of the glass forming the cladding can be further prevented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. FIG. 1 is a sectional view showing an embodiment of the image fiber of the present invention. In the figure, reference numeral 1 denotes an image fiber, 2 denotes a core, 3 denotes a clad, and 5 denotes an optical fiber. The core 2 constituting the optical fiber 5 of this example has about 1% by weight of Cl and about 0.1% by weight.
The cladding 3 is made of quartz glass doped with 1% by weight of F, containing no Cl and doped with about 3% by weight of F. Such an optical fiber 5 was formed as follows.

First, a soot preform was formed by a normal VAD method using SiCl ₄ as a glass raw material, and this was sintered in a Cl gas atmosphere. In this sintering process, the flow rate of Cl gas is set to 2 l / min, SF ₆ gas is introduced at a flow rate of 0.2 l / min, and about 1% by weight of Cl and about 0.1% Of F was doped.

Next, Si (CH ₃ O) ₄ is used as a glass raw material on the periphery of the obtained core 2 and low-temperature plasma CVD is performed.
To form a soot preform by law, this SF ₆
It was sintered in a gas atmosphere. Here, by appropriately setting the flow rate of SF ₆ , the doping amount of F doped in the cladding 2 can be controlled.

The obtained preform was melt-drawn to form an optical fiber 5 having an outer diameter of 200 μm. The optical fiber 5 thus formed has a small difference in viscosity between the core 2 and the clad 3.

In a state where 10,000 optical fibers 5 were bundled, they were heated and melted, spun and integrated to form an image fiber 1. No bubbles were observed during the spinning process of the image fiber 1. Thus, using the optical fiber 5 that does not require a jacket, the image fiber 1 having a higher pixel density and a smaller diameter than that of the conventional image fiber having the same number of pixels was obtained.

B ₂ O ₃ can also be used as a dopant for the glass forming the cladding, and it is desirable to use BH ₃ , BF _3, or the like as a raw material.

[0015]

As described above, the image fiber of the present invention has a core made of silica glass doped with 1 to 2% by weight of C1 and 0.1% by weight or less of F, and does not contain C1. A cladding made of silica glass doped with B ₂ O ₃ and / or F, and having a viscosity at the time of melting the core.
Lowering the viscosity of the clad during melting,
Optical fiber that reduces the difference in melting viscosity between
It is composed of fiber . Therefore, the difference in viscosity between the core and the clad is reduced, and an image fiber can be formed using a two-layer optical fiber that does not require a jacket. Therefore, an image fiber having a small pixel interval, a high density, a small diameter, and excellent flexibility can be obtained, and can be applied to a narrow portion. Further, noise in image transmission can be prevented, and a clear image can be obtained.

Further, since the image fiber is made of quartz glass, it can be used in a radiation environment or an ultraviolet environment, and furthermore, the core is doped with F to improve radiation resistance. It can be used in By doping the core with Cl and preventing the clad from containing Cl,
The difference in the refractive index between the core and the clad can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an image fiber of the present invention.

FIG. 2 is a cross-sectional view showing an example of a conventional image fiber.

[Explanation of symbols]

1 image fiber, 2 core, 3 clad, 5
Optical fiber

────────────────────────────────────────────────── (5) References JP-A-63-189806 (JP, A) JP-A-63-313103 (JP, A) JP-A-2-14850 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G02B 6/06 C03C 3/06 C03C 13/04

Claims (2)

(57) [Claims] 2. The method according to claim 1, wherein the core comprises 1-2% by weight of Cl and 0.1% by weight of Cl.
Wt.% Or less of F-doped quartz glass, the cladding is Cl-free, B ₂ O ₃ and / or F
Is composed of quartz glass doped with, which reduces the viscosity of the core when melting and reduces the viscosity of the cladding when melting.
Viscosity during melting between core and clad
Image file made of optical fiber with a small difference
Ba. 2. A glass raw material forming the cladding of claim 1, wherein the image fiber alkoxysilanes.