JPS62280703A - Polymer clad fiber - Google Patents

Abstract

PURPOSE:To attain the reduction of transmission loss even at low temperature and to reduce the projection of a clad due to temperature itinerancy by giving the clad a double structure of an internal and an external layer and forming the internal and external layers of organic high polymer materials which has a >=10 difference in Shore hardness (type A) and are mutually adhesive. CONSTITUTION:The internal and external layers 8a and 8b of the clad 8 are both formed of organic high polymer materials such as poly(methyl methacrylate), silicone resin, and an organic fluorine-based compound, and the materials forming the internal layer 8a and external layer 8b differ in hardness. The difference is Shore hardness (type A) between the materials of those internal and external layers 8a and 8b is set to >=10. Either of the internal layer 8a and external layer 8b may be formed of a soft material. When the internal layer 8a is formed of a soft material and the external layer 8b is formed of a hard material, the effect of prevention against the projection of the clad 8 is large. When the internal layer 8a is formed o a hard material and the external layer 8b is formed of a soft material, on the other hand, the effect of prevention against an increase in transmission loss at low temperature is large.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a polymer clad fiber whose cladding is formed of an organic polymer material.

"Prior Art" Polymer clad fibers are suitably used for short-distance communications such as large-diameter, high-volume optical link devices and in-house information communication networks.

FIG. 5 shows a conventional optical fiber core made of polymer clad fiber. This thing has core 1 made of glass material? This is when a polymer clad fiber 3 consisting of a cladding 2 made of a polymeric material is covered with a coating layer 4. The cladding 2 of the polymer clad fiber (hereinafter abbreviated as fiber) 3 is formed in one layer.

Further, the covering layer 4 is generally made of nylon or the like.

"Problems to be Solved by the Invention" In conventional polymer clad fibers, if the cladding 2 is made of a hard organic polymer material, the transmission loss at low temperatures will significantly worsen, making it difficult to use in cold regions. This creates a problem that it cannot be installed and used outdoors.

On the other hand, if the cladding 2 is made of a flexible material,
When subjected to temperature fluctuations, a problem arises in which it becomes difficult to connect the fiber end to the other end. That is, the fiber 3 is used after being covered with the coating layer 4, but when this coating layer 4 is formed, shrinkage strain remains in the coating layer 4. When this shrinkage strain is relaxed by being subjected to temperature fluctuations, the covering layer 4 expands. When the club 2 is made of a soft material, the cladding 2 is expanded as the coating layer 4 is expanded, and as a result, the cladding 2 protrudes from the end of the fiber 3.

Therefore, if the cladding 2 is made of a soft material,
There is a problem in that it is difficult to use outdoors where temperature fluctuations are likely to occur.

As described above, conventional polymer clad fibers have the disadvantage that they are difficult to use unless the temperature environment is favorable, regardless of whether the cladding 2 is made of a hard material or a soft material.

"Means for Solving the Problems" Therefore, in the polymer clad fiber of the present invention, the cladding has a double structure consisting of an inner layer and an outer layer, and the material forming the inner layer and the material forming the outer layer are different from each other. The above-mentioned problems were solved by using an organic polymer material that has a difference in hardness (type A) of 0 or more and has mutual adhesive properties.

"Example" Hereinafter, the polymer clad fiber of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an optical fiber core made of an embodiment of the polymer clad fiber of the present invention, so the reference numeral 5 in the figure is a polymer clad fiber (hereinafter abbreviated as fiber), and the reference numeral 6 is a coating layer. .

The fiber 5 is formed from a core 7 and a cladding 8, and the cladding 8 is composed of two layers: an inner layer 8a and an outer layer 8b. The core 7 of the fiber 5 is made of a glass material such as pure quartz, doped glass, or fluoride glass that has high transparency in the wavelength range from ultraviolet to infrared.

In addition, both the inner and outer layers 8a and 8b of the cladding 8 are made of a transparent organic polymer material such as polymethyl methacrylate, silicone resin, or a fluorine-based compound. This cladding 8 is made up of an inner layer 8a and an outer layer 8b.
are made of materials with different hardnesses. The materials forming these inner and outer layers 8a and 8b have a hardness (
Type A) is selected so that the difference is 10 or more. If the difference in hardness between the materials forming the inner and outer layers 8a and 8b becomes undesirable, the fiber 5 will have a large transmission loss at low temperatures and the protrusion m of the cladding 8 will become large, which is not preferable.

Either the inner layer 8a or the outer layer 8b may be formed of a soft material.If the inner layer 8a is formed of a soft material and the outer layer 8b8 is formed of a hard material, the effect of preventing the cladding 8 from protruding is greater. be. Conversely, the inner layer 8a is made of a hard material, and the outer layer 8
When b is made of a soft material, it is highly effective in preventing an increase in transmission loss at low temperatures.

It is desirable that the soft material forming the inner and outer parts 158a and 8b has a hardness of about 25 to 70 on the Noyoa hardness (A type). In addition, hard materials have Shore hardness (Δ type)
It is desirable that it is 45 or more. Hardness of soft material 25
If the value is outside the range of ~70, a sufficient buffering effect by the soft material cannot be obtained, resulting in a problem of worsening transmission loss at low temperatures. Furthermore, if the hardness of the hard material is less than 45, it will not be possible to sufficiently reduce the protrusion of the cladding 8 because it will not provide sufficient resistance to the expansion of the coating layer 6, which will be described later.

The material forming the inner layer 8a and the material forming the outer layer 8b of the cladding 8 must have adhesive properties to each other.

The adhesive strength between these inner and outer layers 8a and 8b was determined to be 100/100% using Chiban Cellotape (trade name) in the substrate test.
It is desirable that it be 100 or more. Inner and outer layers 8 a, 8
If the adhesive strength between the layers 8a and 8b is weak, a problem arises in that when the fiber 5 is subjected to a temperature change, the inner and outer layers 8a and 8b are likely to peel off.

Furthermore, the adhesive strength between the inner layer 8a of the cladding 8 and the core 7 is as follows:
It is necessary that it is 80/loo or more. If this adhesive strength is weak, the fiber 5 will be bent and the core 7
, the problem arises that the cladding 8 is likely to peel off.

The thickness of the cladding 8 made of the above-mentioned material is usually about 50 μm. The thickness of the inner layer 1w8a and the thickness of the outer layer 8b are such that the ratio is 1/1 within the coverage range.
99 to 99/[, but inside and outside 18a
, 8b is approximately 50,150, the best results are obtained.

Naturally, the refractive index of the material forming the inner layer 8a of the rad 8 must be lower than the refractive index of the glass material forming the core 7, and usually NA=0.3 to 0.4. is set to On the other hand, the outer layer 8b of the cladding 8
The refractive index of the material forming the inner layer 8 may be high or low, but in order to prevent the so-called cladding mode from seeping out, it is necessary to
It is desirable that the refractive index be set to be approximately the same as or lower than the refractive index of the material a. When the ratio of the thicknesses of the inner and outer layers 18a and 8b is 50150 to 998, the outer layer 8b is made of a material having a refractive index higher than that of the material forming the inner layer 8a.
Even if it is formed, it will not be recorded at all.

The coating 56 protects the fiber 5, improves its strength, and facilitates handling, and is usually made of nylon, polyethylene resin, or the like.

"Function" The polymer clad fiber of the present invention has less transmission loss at low temperatures and also has less protrusion of the cladding 8.

Although the reason is not clear, the present inventors consider the reason as follows.

First, in the polymer clad fiber of the present invention, since either the inner layer 8a or the outer layer 8b of the cladding 8 is formed of a soft material, even if the coating layer 6 shrinks at low temperatures, the layer 8a formed of the soft material Alternatively, the stress is relieved by 8b. As a result, the increase in transmission loss of the fiber 5 at low temperatures is reduced.

Moreover, even if the shrinkage strain in the coating layer G is relaxed and the coating layer 6 is expanded by repeatedly subjecting the IW layer 6 coated to the fiber 5 to temperature changes, the polymer clad fiber of the present invention does not have a cladding strain. Since either the inner B 8 a or the outer 118 b of the cladding 8 is formed of a hard material, the layer 8 a or 8 b formed of this hard material exerts a large resistance against the expansion of the covering layer 6, and the protrusion of the cladding 8 is prevented. suppressed.

If soft materials and hard materials are used that have a hardness difference of 10 or more on the Shore hardness, 12
The interaction between 58a and 8b produces the above effect in a favorable direction, reducing the amount of protrusion of the cladding and reducing the increase in transmission loss at low temperatures.

"Experimental Example" Experimental Example 1 Various optical fiber cores having the structure shown in FIG. 1 were prepared by changing the hardness of the material forming the outer layer 8b. The amount of protrusion of the cladding 8 after the heat cycle test was examined.

The specifications of the created optical fiber core wire are as follows.

Core: Made of pure quartz, outer diameter 200μ, inner layer of scraps...
...Made of polymeric resin, outer diameter 250μ, hardness (Shore A) = 5G, refractive index (value at 25℃ against sodium D line, same below) n = 1.408 Outer layer ...・In Table 1, a to ``and h'' are made of ricone resin, and g and i in Table 1 are made of organic fluorine compound with outer diameter 3.
00μ shoulder hardness and refractive index are II as shown in Table 1! Covering layer: Made of nylon, outer diameter 900 μm. The optical fiber core wires were tested as follows.

1) Measurement of increase in transmission loss at low temperature The transmission loss at a temperature of -20°C was compared with the transmission loss at a temperature of 20°C. The test length was 1200 m, and a light source with a wavelength of 0.85 μm was used.

2) One optical fiber core wire with a protrusion length of 2ffl is heated at 0°C to 60°C x 3
After 0 IRL heat cycle tests, the length of the cladding protruding from the end of the optical fiber was measured.

The results are shown in Table 1.

Table 1 As can be seen from the results in Table 1, when the difference in hardness between the inner layer 8a and the outer layer 58b is 10 or more, both the increase in transmission loss at low temperatures and the amount of protrusion of the cladding 8 after the heat cycle test are It is decreasing, and a few notable cases can be seen.

Experimental Example 2 By changing the thickness of the inner layer 8a and outer layer 8b, +1 as shown in FIG.
Various types of Vt fiber cores were prepared, and the temperature characteristics of transmission loss and the amount of cladding protrusion after heat cycle tests were investigated for each core wire.

The specifications of the optical fiber core wire created were as follows.

Core: Made of pure quartz, outer diameter 250μ, shoulder inner layer...
...Made of organic fluorine thread compound, outer diameter is shown in Table 2, hardness (Shore A) = 79, refractive index n = 1.410 Outer layer...Made of Noricone resin, outer diameter 350μ Skin hardness -48, Refractive index: -1,/104 Covering layer: made of nylon, outer diameter: 900 μm As a comparative example, a layer in which the cladding was formed in one layer was prepared. The cladding of this comparative example was made of silicone resin, and had a hardness of 65 and a refractive index of 1.408.

Further, tests on these optical fiber core wires were conducted as follows.

1) Temperature characteristics of transmission loss Based on the transmission loss at a temperature of 20°C, the temperature is set to 0.
The increase in transmission loss (m8) when the temperature was lowered to 0C1-20℃ and -40℃ was investigated. The test length was I 000 m, and a light source with a wavelength of 085 μm was used.

2) Protrusion 4+i Same as Experimental Example 1.

The test results for the temperature characteristics of transmission loss are shown in FIG. 2, and the test results for the protrusion amount are shown in Table 2.

From the results of the first pair in Table 2, the inner layer 8a made of a material with high hardness
If the cladding is thick, the effect of suppressing the protrusion of the cladding is large;
On the other hand, it has been found that when the outer layer 8b made of a soft material is thick, it is highly effective in suppressing an increase in transmission loss.

Roofing Example 3 A cord consisting of two polymer clad fibers as shown in FIG. 3 was prepared, and the temperature characteristics of transmission loss and the amount of protrusion of the cladding after a heat cycle test were determined.

The created code consists of a core 7, a cladding 8, and a covering layer 6.
The optical fiber core wire 9 consisting of the above is coated with a tension member IO manufactured by Közler, and two of these are coded with a source +1 made of polyvinyl chloride resin.

The specifications of the code are as follows.

Core: Made of pure quartz, outer diameter 200μ, inner layer...
... Made of silicone resin, outer diameter 250 μm, hardness (Shore A) -42, refractive index n = 1.403 Outer layer ... Made of silicone resin, outer diameter 300 μm, hardness = 82, refractive index = 1, 41/I Sheath layer: Made of nylon, outer diameter 900 μm Sheath: Outer diameter 281, Width in groove direction 56. (2) As a comparative example, a cord having a single cladding layer was prepared and subjected to the same test. The cladding of this comparative example is made of silicone resin, with a hardness of 65 and a refractive index of 1.408.
Met.

The test method also tested the temperature characteristics of transmission loss for cord length 70.
The test was the same as Experimental Example 2 except that the test was performed at 0a+.

The test results of the temperature characteristics of the transmission characteristics are shown in FIG. 4, and the test results of the protrusion amount are shown in Table 3.

Table 3 "Effects of the Invention" As explained above, the polymer clad fiber of the present invention has a cladding having a double structure consisting of an inner layer and an outer layer,
The inner layer and outer layer have a hardness difference of 10 based on Shore hardness (type A).
In addition, since it is formed of an organic polymer material that has adhesive properties to each other, the transmission loss is as low as 6 at low temperatures.

Furthermore, even when used as a core wire or coded, there is little protrusion of the cladding due to temperature fluctuations, and connections with connectors etc. can be made without any problem. Therefore, with this polymer clad fiber, it is possible to obtain a versatile optical fiber core wire or cord that can be used in harsh environments such as in cold regions or outdoors where temperature changes are large.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an optical fiber core made of an example of the polymer clad fiber of the present invention, Fig. 2 is a graph showing the temperature characteristics of transmission loss obtained in Experimental Example 2, and Fig. 3 is a graph showing the temperature characteristics of the transmission loss obtained in Experimental Example 2. A cross-sectional view showing a cord made of the polymer clad fiber of the invention, Fig. 4 is a graph showing the temperature characteristics of transmission loss obtained in Experimental Example 3, and Fig. 5 shows an optical fiber core made of the conventional polymer clad fiber. FIG. 5... Polymer clad fiber (fiber), 7.
... Core, 8... Clad, 8a... Inner layer, 8b.
...outer layer.

Claims (1)

[Claims] In a polymer clad fiber consisting of a core made of a glass material and a cladding made of an organic polymer material, the cladding has a double structure of an inner layer and an outer layer, and the material forming the inner layer and the material forming the outer layer have Shore hardness ( A polymer clad fiber characterized by using an organic polymer material having a hardness difference of 10 or more according to type A) and having mutual adhesiveness.