JPH10186193A - Optical fiber cable and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cable which withstands a high temp. and is capable of extremely reducing the sectional area for laying without impairing buffer and protective functions by coating an optical fiber with a protective film consisting of powder ceramics contg. a binder. SOLUTION: The optical fiber 11 is, for example, a quartz fiber and the outer periphery thereof is coated with the protective film 12 consisting of the powder ceramics contg. the binder. The protective film 12 is unfired or half-fired ceramics and has flexibility. If, for example, the optical fiber 11 is the quartz fiber of 125μm, the preferable layer thickness of the protective film 12 is 1803mm. The optical fiber 11 coated with the protective film 12 consisting of the unfired or half-fired ceramics in such a manner has the specified flexibility at the time of laying and the heat resistance to prevent the melting of the protective film 12 even under a high-temp. environment is imparted to the fiber. If the optical fiber 11 is particularly fine, the bending by the protective film 12 consisting of the ceramics is suppressed and, therefore, the optical fiber having the resistance to damaging is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable in which an optical fiber is covered with a protective layer, and a method for manufacturing the same.

[0002]

2. Description of the Related Art When an optical fiber is inserted into a reinforcing cable, a small axial distortion (microbend) occurs along the fiber. The microbend provides optical coupling between the various guided modes of the fiber, causing light attenuation. For this reason, conventionally, when an optical fiber is formed into a cable, the outer periphery of the fiber is covered with a cushioning material made of soft nylon or other resin, thereby minimizing microbending and providing strength against cracks and vibration. There is also known a loose tube structure in which an optical fiber is disposed in a protective tube having an inner diameter larger than its outer diameter so that a space is provided between the optical fiber and the covering member.

[0003]

However, the protective layer made of resin is weak to heat and melts when used in a high-temperature region, so that the function as the protective layer is impaired. In addition, the loose tube structure
The laying cross-sectional area per optical fiber is increased. In particular, when a multi-core fiber is formed, this appears as a significant problem. The present invention has been made in view of the above circumstances, and provides an optical fiber cable which can withstand high temperatures without impairing a buffer function and a protection function, and which can have an extremely small laid cross-sectional area, and a method of manufacturing the same. It is intended to provide.

[0004]

The optical fiber cable according to the present invention is characterized in that the optical fiber is covered with a protective layer made of powdered ceramics containing a binder. The optical fiber cable according to the present invention is also characterized in that a plurality of optical fibers are each covered with a protective layer made of powdered ceramics containing a binder and then pressure-bonded. In the present invention, preferably, the protective layer has flexibility in an unfired or semi-fired state. Further, at least a part of the protective layer may be in a sintered state.

The method for manufacturing an optical fiber cable according to the present invention comprises, first, a step of supplying a slurry prepared by preparing a binder and powdered ceramics with a solvent on a carrier film, and a step of supplying the slurry supplied on the carrier film in this step. A step of passing the optical fiber through the inside, a step of adjusting the thickness of the slurry adhered to the outer periphery of the optical fiber by this step, and heating and drying the slurry of the outer periphery of the optical fiber whose thickness has been adjusted in this step. Forming a protective layer of fired or semi-fired ceramics. The method for manufacturing an optical fiber cable according to the present invention comprises, secondly, a step of manufacturing an optical fiber, and passing the optical fiber drawn out in this step through a slurry container prepared by preparing a binder and powdered ceramics with a solvent. And a step of heating and drying the slurry on the outer periphery of the optical fiber to form an unfired or semi-fired ceramic protective layer.

According to the present invention, since the optical fiber is covered with the protective layer made of powdered ceramics containing a binder, the protective layer functions as a cushioning material due to its flexibility, and suppresses microbending of the optical fiber. And the laying cross-sectional area can be reduced. Moreover, since the protective layer is made of ceramics having high heat resistance, it does not melt even in a high temperature environment. In particular, if the ceramic protective layer is unfired or semi-fired, the protective layer has a certain flexibility, elasticity and plasticity and can withstand a certain amount of bending, so that the workability of fiber laying is not impaired. Absent. After laying, a portion requiring a particularly high protection function is appropriately sintered to improve the protection function. In addition, if the optical fiber is very thin and easy to bend, it may be easily broken during the operation beyond the allowable bending range. According to the present invention, however, the protective layer made of ceramics gives a large resistance to bending. Therefore, it is less susceptible to damage.

[0007] The thicker the protective layer of ceramics, the lower the flexibility and the smaller the allowable bending radius. Therefore, the thickness of the protective layer is determined depending on how much the bending radius is allowed. When powder ceramics with a particle size of several to several tens of μm are used, at least several to several tens of ceramic particles must be stacked in order to achieve a good protection function. The thickness of the protective layer is preferably 50 to 200 μm. When the optical fiber cable according to the present invention is placed in a high-temperature environment, the ceramic protective layer is baked and hardened, but there is no problem even if the ceramic protective layer is cured unless work requiring deformation is performed, and the function as the protective layer is exhibited. it can.

According to the first manufacturing method of the present invention, an optical fiber cable in which the thickness of a protective layer made of ceramics is accurately adjusted by applying a manufacturing process of a green sheet using a normal doctor blade or the like is applied. Can be.
Further, according to the second manufacturing method of the present invention, the resin coating step in the ordinary optical fiber manufacturing step is simply replaced with a ceramic coating step, and the conventional step can be easily performed without any particular complication or significant change. An optical fiber cable coated with a protective layer made of ceramics can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a heat-resistant optical fiber cable 10 according to one embodiment of the present invention. The optical fiber 11 is, for example, a quartz fiber, and its outer periphery is covered with a protective layer 12 made of powder ceramic containing a binder. The protective layer 12 is an unfired or semi-fired ceramic and has flexibility. If the optical fiber 11 is a 125 μm φ quartz fiber, the protective layer 12
Is preferably 180 μm.

Several methods for manufacturing such an optical fiber cable 10 are conceivable. FIG. 2 shows a method of forming a ceramic protective layer 12 on an optical fiber 11 by applying a doctor blade method for producing a green sheet. An appropriate film 21 is stretched between rolls 22a and 22b via guide rollers 23a and 23b, and transported in one direction as indicated by arrows in the figure. The optical fiber 11 to be coated with the ceramic is conveyed on the film 21 and wound around a roll 27.

[0011] Between the guide rollers 23a and 23b,
A slurry container 24 containing a slurry 25 prepared by preparing a binder and powdered ceramics with a solvent is arranged, and the slurry 25 is supplied little by little from the container 24 onto the film 21 to be conveyed.
The optical fiber 11 transported on the film 21 is passed through the slurry 25. A doctor blade 26 for scraping the slurry 25 is disposed behind the container 24. The doctor blade 26 has a through hole 31 for the optical fiber 11 at the bottom as shown in FIG.
Here, the slurry 25 around the optical fiber 11 is adjusted to have a substantially constant thickness.

In the guide roller 23b, the film 2
1 and the optical fiber 11 are separated from each other, and the optical fiber 11
, And is heated by a heater 30 and wound up on a roll 27 via a guide roller 28. As shown in FIG. 4, the guide roller pairs 29a and 29b have grooves formed in the outer periphery thereof, each of which has a semicircular cross section, and a through hole 32 through which the optical fiber 11 can be passed is formed in the opposed portion thereof. The optical fiber 11 passes through the through hole 32.
The guide roller pair 29a, 29b may be in a freely rotatable state or a fixed state, or may be rotationally driven in a direction against the conveyance of the optical fiber 11.

By passing through the doctor blade 26 and the pair of guide rollers 29a and 29b, the thickness of the slurry around the optical fiber 11 is adjusted to be substantially constant. The heat-resistant optical fiber cable 10 in which the protective layer 12 made of semi-fired ceramic is formed with a substantially uniform thickness is obtained.

According to this embodiment, the optical fiber 11
Protective layer 1 made of unfired or semi-fired ceramic
2, the fiber has a certain flexibility at the time of laying the fiber and has a heat resistance such that the protective layer does not melt even in a high temperature environment. In particular, when the optical fiber 11 is thin, since the bending is suppressed by the protective layer 12 made of ceramics, the fiber is hardly damaged.

FIG. 5 shows an embodiment in which the step of forming a protective layer using ceramics is incorporated in the fiber manufacturing step. This embodiment is a case of a drawing method usually used for manufacturing a multi-component fiber, and an optical fiber 11 is drawn out from a crucible 51 where a raw material melt is formed by an electric furnace 52. Below the crucible 51, the same slurry 5 as in the previous embodiment is provided.
The slurry container 53 in which No. 4 was prepared is arranged, and the protective layer coating part is comprised. That is, through holes 55 and 56 through which the optical fiber 11 can pass are formed in the bottom portion and the lid portion 57 of the container 53, and the optical fiber 11 passes through the inside of the slurry container 53 through these through holes 55 and 56. Let it. Then, the optical fiber coated with the slurry is heated by a heater 5.
By heating and drying in step 8, an optical fiber cable 10 having a protective layer made of unfired or semi-fired ceramics can be obtained.

According to this embodiment, the step of coating the ceramic protective layer can be incorporated into the ordinary optical fiber manufacturing process without greatly changing the process. Although the embodiment of the drawing method is described with reference to FIG. 5, the present invention can be similarly applied to a process of manufacturing a silica-based optical fiber. That is, for the production of quartz optical fiber, CVD
A vapor-phase deposition method such as VAD (Vapor-phase Axitial Deposition) or the like is used, and a ceramic protective layer is formed on the optical fiber drawn by these methods in the same process as in the embodiment of FIG. Can be.

FIG. 6 shows still another embodiment. In this embodiment, as shown in (a), a green sheet 61 in a semi-dry state formed by, for example, a doctor blade method is wound around an optical fiber 11 and heated and dried.
As a result, a ceramic protective layer can be formed on the optical fiber 11 as in the previous embodiment. When this method is developed, a large number of optical fibers are wound around a green sheet in a semi-dry state, bundled and heated while being pressed, as shown in FIG. An optical fiber cable embedded in the protective layer 12 without any gap can be easily produced.
When this optical fiber cable is used for an image fiber or the like, it is preferable that the protective layers at both ends are sintered and fixed in advance. The optical fiber cable according to the present invention is, for example, an OTDR (Optical Time Domain Refl) which detects a fire or the like by laying in a tunnel and detecting a time difference of return light.
ectmetry) It is suitable as a temperature sensor or an image fiber for observing the inside of a nuclear reactor.

[0018]

As described above, according to the present invention, by covering an optical fiber with a protective layer made of powdered ceramics containing a binder, the protective layer functions as a cushioning material due to its flexibility. Microbending can be suppressed and the laid cross-sectional area can be reduced. Further, since the protective layer is made of a ceramic having high heat resistance, it does not melt even in a high temperature environment. In particular, if the ceramic protective layer is in an unfired or semi-fired state, the protective layer has elasticity and plasticity, can withstand certain bending, and gives a large resistance to bending in the case of a thin optical fiber. Can be

[Brief description of the drawings]

FIG. 1 shows an optical fiber cable according to an embodiment of the present invention.

FIG. 2 shows a step of forming a protective layer of the optical fiber of the embodiment.

FIG. 3 shows a doctor blade used in the protective layer forming step.

FIG. 4 shows a guide roller pair used in the protective layer forming step.

FIG. 5 shows a method of manufacturing an optical fiber cable according to another embodiment.

FIG. 6 shows a method of manufacturing an optical fiber cable according to another embodiment.

[Explanation of symbols]

10 ... optical fiber cable, 11 ... optical fiber, 12 ...
Protective layer (ceramic), 21 ... film, 24, 53
... Slurry container, 26 ... Doctor blade, 29a, 29b
... guide roller pair, 30, 58 ... heater, 51 ... raw material crucible, 61 ... green sheet.

Claims (6)

[Claims] 1. An optical fiber cable comprising an optical fiber covered with a protective layer made of powdered ceramics containing a binder. 2. An optical fiber cable comprising a plurality of optical fibers each covered with a protective layer made of powdered ceramics containing a binder and pressure-bonded. 3. The optical fiber cable according to claim 1, wherein the protective layer has flexibility in an unfired or semi-fired state. 4. The optical fiber cable according to claim 1, wherein at least a part of the protective layer is in a sintered state. 5. A step of supplying a slurry prepared by preparing a binder and a powdered ceramic with a solvent on a transport film; a step of passing an optical fiber through the slurry supplied on the transport film in this step; Adjusting the thickness of the slurry adhered to the outer periphery of the optical fiber by heating and drying the slurry at the outer periphery of the optical fiber whose thickness has been adjusted in this step to form an unfired or semi-fired ceramic protective layer. And a method for manufacturing an optical fiber cable. 6. A step of manufacturing an optical fiber, a step of passing the optical fiber drawn in this step through a slurry container prepared by preparing a binder and a powdered ceramic with a solvent, and applying a slurry to the outer periphery of the optical fiber; Heating and drying the slurry around the optical fiber to form a protective layer of unfired or semi-fired ceramics.