JPS5916893Y2 - optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in optical fibers used, for example, in optical transmission.

As is well known, for example, an optical fiber used for optical transmission is provided with a fiber material having a curvature index of n2 on the outer periphery of a fiber material having a refractive index of nl, as shown in FIGS. 1(a) and 1(l).

The relationship between the refractive indexes of this fiber material is nl>n2, and the incident light travels through the fiber material having a refractive index n1 while being reflected on the inner surface of the fiber material having a refractive index n2.

By the way, these optical fibers are generally very thin in diameter, and joining these thin optical fibers is a difficult task.

Generally, in the case of a permanent connection by splicing or the like, this is not so much of a problem as the outer diameter of the optical fiber only needs to be constant, but mechanical joining using a connector or the like is a work that requires extremely high precision.

That is, when joining optical fibers, the centers of the optical fibers must be aligned accurately due to optical loss, and it is extremely difficult to do this with extremely thin optical fibers.

Therefore, in order to easily do this, it is possible to increase the diameter of the connecting end of the optical fiber, but if the diameter is simply increased, the optical energy will be concentrated in the center of the optical fiber, resulting in If the centers of the optical fibers are not aligned reliably, the loss of optical energy will be large and the connection will not be easy.

This idea was made based on the above circumstances, and its purpose is to form a reflective part in the center of the optical fiber and to increase the diameter of the connecting end, thereby causing light energy loss. Facilitates mechanical connection without
Moreover, it provides an optical fiber that is easy to manufacture.

An embodiment of this invention will be described below with reference to the drawings.

In FIGS. 2a, 1) and 2c, reference numeral 10 denotes an outer peripheral reflecting portion formed of a fiber material having a refractive index of n1.

A core wire, that is, an optical path section 11 is formed inside the outer circumferential reflecting section 10 using a fiber material having a refractive index of n2.

In the center of this optical path section 11, for example, a central reflection section 12 is formed of a fiber material having a refractive index of n3.

The relationship of the refractive index of the optical fiber 13 configured in this way is nl<n2. n3<n2, and substantially n1=n3<n2.

Moreover, this optical fiber 13 has a large diameter portion A as shown in the figure.
, an inclined part B, and a narrow diameter part C, and the large diameter part A is used as a connecting end.

Further, in the large diameter part A and the small diameter part C, an outer peripheral reflective part 10,
Optical path section 11. The central reflecting section 12 is parallel to the direction of light propagation, and in the inclined section B, the tangent between the optical path section 11 and the peripheral reflecting section 10 is θ with respect to the direction of propagation of light, as shown in FIG.
1, and the tangent between the optical path section 11 and the central reflection section 12 is at an angle of .theta.2 with respect to the traveling direction of the light.

This angle θ1. The relationship between θ2 is θ1>θ2, and the maximum value of this angle is defined by the refractive index of the fiber material.

In the above configuration, the incident light travels within the optical path section 11 after being totally reflected by the outer peripheral reflecting section 10 and the central reflecting section 12 having different refractive indexes, as shown by the arrows in FIG.

Incidentally, in order to actually manufacture an optical fiber having the above shape, it is simple and appropriate to first form a large diameter section A, and then heat this to form the inclined section B and the narrow diameter section C.

Also, the angle θ1 of the inclined portion B. The relationship of θ2 is obtained during thermoforming.

According to the above configuration, the optical path section 11 having a refractive index n2 is formed inside the outer circumferential reflecting section 10 having a refractive index n1, and the central reflecting section 12 having a refractive index n3 is further formed in the center of this optical path section 11. , this refractive index relationship is at least nl〈n
2. It is set as n3<n2.

Therefore, by adopting such a configuration, it is possible to increase the diameter of the connection end A, and it is possible to easily align the centers when connecting optical fibers through this large diameter part A, and it is possible to use a connector, etc. mechanical connections can be easily made.

Moreover, such a configuration has the advantage of reducing optical energy loss because connection can be performed reliably.

Further, the optical fiber 13 having this configuration can be manufactured by first forming a large diameter portion A as a connection end portion, and then easily reducing the diameter by heat forming.

Note that this invention is not limited to the above embodiments,
For example, the slope portion B is not limited to a linear slope, but may be curved as shown in FIG.

This curved slope can be easily formed by thermoforming and has good light transmission efficiency.

Further, as a manufacturing method for the optical fiber 13, the refractive index may be changed by a diffusion method on the surface of the fiber material, and further, the outer peripheral reflecting portion 10, the optical path portion 11. The boundary portion of the central reflective portion 12 may be of a step index type or a graded index type.

As detailed above, according to this invention, by forming a reflective part in the center of the optical fiber and increasing the diameter of the connecting end, mechanical connection is facilitated without causing optical energy loss. In addition, it is possible to provide an optical fiber that is easy to manufacture.

[Brief explanation of the drawing]

Figures 1a and 1) are a vertical cross-sectional view and a side cross-sectional view, respectively, showing an example of a conventional optical fiber, and Figure 2 is a longitudinal cross-sectional view of an embodiment of the optical fiber according to this invention. , the same figure is a side sectional view, the same figure C is a longitudinal sectional view of a different part from the same figure a, and FIG.
FIG. 4 is a diagram for explaining the traveling state of light in the optical fiber shown in FIG. 2, and FIG. 5 is a diagram for explaining another embodiment of this invention. DESCRIPTION OF SYMBOLS 10...Outer reflecting part, 11... Optical path part, 12... Central reflecting part, A... Connection end part.

Claims (1)

[Scope of utility model registration request] It is composed of an outer peripheral reflecting part with a refractive index of n1, an optical path part formed within the outer peripheral reflecting part and having a refractive index of n2, and a central reflecting part formed in the center of this optical path part and with a refractive index of n3, and each of the above refractive indexes is The relationship is at least nl<n2. n
3<n2, and the diameters of the outer peripheral reflecting portion, the optical path portion, and the central reflecting portion at the connection end portion are gradually increased in diameter.