JPH0121281Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to a multi-core fiber having a plurality of cores.

[Prior art and its problems]

Conventional optical cables are made by sequentially applying modified silicone resin and silicone resin on a bare optical fiber to form a bare wire, and then a secondary coating made of nylon resin or the like is applied on top of the bare wire to form a core wire with an outer diameter of about 0.8 to 1 mm. Nylon resin is made by twisting multiple core wires together.
It is made by covering it with a sheath made of PVC resin, etc.

However, in an optical cable having such a configuration, the finished diameter of the cable tends to be larger than the number of bare optical fibers that are accommodated as optical transmission lines. That is, since a primary coating layer and a secondary coating layer are provided on each bare optical fiber and are twisted together, the number of accommodated optical fibers becomes small in relation to the outer diameter of the cable. When applying such an optical cable to, for example, an optical cable composite overhead ground wire,
Since there is a limit to the outer diameter of the combined optical cable,
There was a problem that it was not possible to combine large-capacity optical cables.

[Purpose of invention]

This idea was made in view of the above circumstances,
It is an object of the present invention to provide a multi-core fiber that can constitute a relatively small-diameter, high-capacity optical cable.

〔composition〕

The multi-core fiber of this invention has at least one
A large number of cores capable of single mode transmission are positioned around one core capable of multimode transmission, and these cores capable of single mode transmission are arranged at intervals such that they are not electromagnetically influenced by each other. This is what happens.

〔Example〕

The drawing shows an example of the multi-core fiber of this invention. In the drawing, reference numeral 1 is a multi-core fiber having a total of seven cores. The core 3 in the center is capable of multimode transmission and has a graded index type refractive index distribution, and the six cores in the outer periphery surrounding this core 3 have a step index type refractive index. , and a core 4 capable of single mode transmission with a small diameter. Note that the spacing between these cores 4, 4 is such that they are not influenced by each other in terms of electromagnetic waves.

In order to make such a multi-core fiber into a cable, the fiber 1 is coated with, for example, a modified silicone resin and a silicone resin in sequence, and a nylon resin is applied thereon, or a plurality of coated multi-core fibers are assembled. This is done by

[Effect]

When the multi-core fiber 1 having such a structure is used to make a cable, the cable diameter can be reduced until the fiber has a large number of cores. For example, if cores 3 and 4 are cladded to have an outer diameter of 120 μm, the diameter of fiber 1 is 120 x 3 + 15 (jacket thickness) x
2=390μm. If a primary coating layer and a secondary coating layer are formed on this with a thickness of 400μm, the outer diameter will be 1190μm.
It is a 7-core cable of m. On the other hand, in the conventional method, the fiber diameter including cladding is the same.
The thickness of the primary coating layer and secondary coating layer is 120μm.
When formed to a thickness of 400 μm, the core wire has an outer diameter of 920 μm.
When seven of these are twisted together, it becomes a seven-core cable with an outer diameter of 920 μm x 3 = 2760 μm. Therefore, a cable with the same capacity can be obtained with an outer diameter smaller than 1/2.

In addition, since the core 3 of graded index type capable of multi-mode transmission is placed in the center,
When used as a cable, it is easily affected by bending.
The graded index type core 3, which has a large deterioration in transmission characteristics, is not subjected to severe bending.
No deterioration of transmission characteristics occurs. On the other hand, the core 4 on the outer periphery, which is capable of single mode transmission, is not easily affected by bending, so even if it is slightly bent due to being located on the outside,
There is no significant deterioration in transmission characteristics.

Furthermore, different types of cores can be installed in one fiber 1, such as a core 3 capable of multi-mode transmission, a core 4 capable of single-mode transmission, etc., so a single fiber can be used for multiple purposes. It can also be used for purposes.

〔Example〕

Next, an example of a method for manufacturing the multi-core fiber 1 having such a structure will be explained.

First, for example, seven fiber base materials each having a cladding layer and serving as the base of each core 3, 4 are prepared by a VAD method or the like. Then, a core base material capable of transmitting a tamode with a graded index type refractive index distribution is arranged in the center, and around this, six core base materials capable of transmitting a single lume mode are arranged, and quartz glass It is housed in a jacket consisting of. Then, the entire jacket is heated and melt-spun from its ends. By paying attention to the spinning conditions and using a material with a low melting temperature for the cladding material, the internal voids are filled with the cladding material.
A multi-core fiber 1 having a substantially circular cross-section as shown in the drawings is obtained.

[Effect of idea]

As explained above, the multi-core fiber of this invention has a core capable of multi-mode transmission on the inside and a core capable of single-mode transmission on the outside, so that a single fiber has multiple cores. It is something. Therefore, by simply providing a primary coating layer and a secondary coating layer on this fiber, a multi-core optical cable can be made, and the outer diameter can be significantly smaller than an optical cable with a conventional structure even though it has the same capacity. I can do it. Therefore, the obtained optical cable is suitably used for optical cable composite overhead ground wires, etc., which have a limited cable diameter.

[Brief explanation of drawings]

The drawing is a sectional view showing an example of the multi-core fiber of this invention. 1...Multi-core fiber, 3...Core capable of multimode transmission, 4...Core capable of single mode transmission.

Claims (1)

[Scope of utility model registration request] A plurality of cores capable of transmitting a single mode are positioned around at least one core capable of transmitting a multimode, and the cores capable of transmitting a single mode are spaced apart from each other so that they are not electromagnetically influenced by each other. A multi-core fiber characterized by being arranged.