JPS6059571B2 - light switch - Google Patents

Description

[Detailed Description of the Invention] In the practical application of optical communication and optical information processing systems using optical fibers, there is a demand for low-loss optical switches for switching, relaying, and exchanging terminal equipment and transmission lines. It's increasing.

Various optical switches have already been proposed that have bypass functions and transmission line switching functions in the event of a failure or maintenance/inspection of a transmission line or terminal device, but most of these have 1 function as described below.
It is an optical switch with n inputs and n outputs, or n inputs and 1 output. The present invention provides an optical switch with n inputs and n outputs, and aims to achieve low loss and sufficiently reduce the amount of crosstalk.

A general one-input, two-output optical switch that has been proposed in the past will be explained based on FIG. 1.

In FIG. 1, 1 is an input optical fiber, and 2 and 3 are output optical fibers. Numerals 4 to 6 are converging rod lenses provided on the same optical axis for the optical fibers 1 to 3, respectively.

The rod lenses 4 to 6 are lenses whose refractive index is highest on the optical axis and decreases parabolically toward the periphery, and has a length of L/4 when the period length is L. . A rod lens 7 is located between the rod lenses 4 and 5 and has a refractive index distribution similar to that of 4 to 6, and has a larger outer diameter than the other rod lenses 4 to 6 and a length of L/2. belongs to.

The rod lens 4 is located at the center between the optical axes of the rod lenses 5 and 6, and is configured to switch the optical path from 1 to 2 or from 1 to 3 by moving the rod lens 7 in the direction of the arrow. As mentioned above, conventionally used optical switches are either 1 input and 2 outputs or 2 inputs and 1 output, and when multiple outputs are required for multiple inputs, a large number of optical switches are required and the shape is large. There are drawbacks such as increased size and higher price.

The present invention eliminates the above-mentioned drawbacks, and one embodiment of the present invention will be described below with reference to the drawings. A and B in Figure 2
2 shows a two-input, two-output optical switch as an embodiment of the present invention. A in FIG. 2 shows the optical path before the optical switch is switched, and B in the same figure shows the optical path after the switch is switched.

In A and B of FIG. 2, 11 and 12 are input optical fibers, and 13 and 14 are output optical fibers. Reference numerals 15 to 18 are rod lenses provided on the same optical axis for the input and output optical fibers 11 to 14, respectively.

The rod lenses 15 to 18 are lenses whose refractive index is highest on the optical axis and decreases parabolically toward the periphery, and has a length of L/4, where L is the period length. It is. All rod lenses described below are of the same type. 19 and 20 are the rod lenses 16 and 20, respectively.
15 with a rod lens placed between 16, 17, and 18.
-18 had the same tendency of refractive index distribution.

The rod lens 19 has a diameter larger than the size of the other rod lenses 15, 16 and 17, 18 arranged side by side, and
The length is cut at a cycle of /2.

Similarly, 20 rod lenses have a length cut with a period of L. However, if rod lenses 19 and 20 have the same refractive index distribution, the distance between the human power fibers 11 and 12 and the output fibers 13 and 14 must be changed at the time of switching because the lens lengths are different. As a countermeasure, the rod lens 20 is of the same length as the rod lens 19, and the refractive index distribution is used so that the period is twice that of the rod lens 19. Next, the arrangement of each part will be described.

The rod lenses 15, 17 and 16, 18 are provided on the same optical axis, and have a structure in which the fire axes of the target lenses 19, 20 are moved to the center between the optical axes of the rod lenses 15, 16. . Now considering the output optical path of the human-powered fibers 11 and 12. A in FIG. 2 is converted into a parallel beam by rod lenses 15 and 16 each having a length of L/4.

Next, the light that enters the rod lens 19 having a length of L/2 as a parallel beam passes through the lens as shown by the solid line and the broken line, and the light emitted from the rod lens 15 is parallel to the rod lens 18. The light enters as light and is propagated to the output fiber 14. Similarly, the light emitted from the rod lens 16 is propagated to the input fiber 13. Next, when switching to the second rod lens 20 shown in B using an appropriate switching mechanism, the rod lens 15 is switched to the second rod lens 20 shown in FIG.
The parallel beam emitted from the rod lens 20 passes through a path as shown by the solid line, enters the rod lens 17 as parallel light, and is propagated to the output fiber 13.

Similarly, the light emitted from the rod lens 16 is propagated to the output fiber 18. FIG. 3 shows another embodiment of an optical switch with two inputs and two outputs.

In FIG. 3, 21 and 22 are input optical fibers, and 23 and 24 are output optical fibers. 25 and 26 are rod lenses L/
4 in length.

27 is a rod lens with a length of L/2, which can be switched with a rod lens 28 having a period of length L and an actual length of a-, which is the same as the rod lens 27.

The input and output fibers 21 to 24 are each connected to a rod lens 25,
It is arranged at a position close to the optical axis of No. 26 and at a point symmetrical to the optical axis.

By doing so, the light emitted from the rod lens 25 becomes a substantially parallel line, passes through the rod lens 27, enters the rod lens 26, and the light emitted from the lens is propagated to optical fibers 23 and 24, respectively. Here, the optical axis relationship of the rod lenses 25 to 27 is the same, or the rod lenses 27
Although the rod lenses 25 and 26 must be located point-symmetrically with respect to the optical axis, by arranging them in this manner, it is possible to perform the same optical fiber switching operation as in the embodiment shown in FIG. An embodiment of an optical switch with 6 inputs and 6 outputs is shown and explained in FIGS. 4 to 6.

In FIGS. 4 and 5, 31 to 36 are input fibers,
41 to 46 are output fibers, 51 to 56 are L/4 rod lenses provided with their optical axes aligned with each of the input fibers 31 to 36, and 61 to 66 are similarly provided to the output fibers 41 to 46. It is a L/4 rod lens.
37 is a rod lens of L/2, 38 is synchronized and the actual length is L
This is a rod lens configured to be the same as that of the /2.

39 is a cylindrical vibrator provided coaxially with the rod lenses 37 and 38.

Although this cylindrical vibrator is used for positioning, an optical fiber may also be used. The switching states of FIGS. 4 and 5 are schematically shown in FIG. 6.

When the rod lens 37 is used, coaxial opposing fibers, for example 31 and 41, are connected as shown by the solid line.

When switching to the rod lens 38, as shown by the broken line, the fibers are positioned symmetrically with respect to the optical axis of the rod lens,
For example, 31 and 44, and 32 and 45 are connected. In the above embodiment, it is possible to switch from six input fibers to six output fibers at the same time, and the actual size is shown in Fig. 2, as can be seen by comparing the diameters of the switching rod lenses. It is possible to obtain a compact optical switch that is almost the same as the conventional one.

Furthermore, since the switching mechanism utilizes the characteristics of a converging rod lens, it does not require strict mechanical precision and is cost effective compared to conventional optical switches that match fibers with an area about the same size as the end faces of the fibers. is also advantageous.
In the above embodiment, the switching rod lens 19,
27, 37 was defined as L/2, which is generally Rll.
Of course, /2 is sufficient. Similarly, the rod lenses 20, 28, and 38 may also be (n+1)L/2 (n is an integer). As described above, according to the present invention, it is possible to switch an even number of optical fibers at the same time with one optical switch, and because the lens is used for magnification, mechanical precision can be relatively relaxed, and low-loss transmission can be achieved. It is possible.

Furthermore, even if the number of optical fibers is large, the entire optical switch can be made compact, and its structure is simple and maintenance is easy, thereby providing an optical switch of high industrial value.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional optical switch, and Fig. 2 is a block diagram showing an embodiment of the optical switch of the present invention. Fig. 3 is a configuration diagram showing another embodiment, Fig. 4 is a perspective view showing an embodiment with 6 inputs and 6 outputs, Fig. 5 is a right side view of the embodiment shown in Fig. 4, and Fig. 6 is a state diagram. FIG. 2 is an explanatory diagram showing a connection switching state of a transmission line.

Claims (1)

[Claims] 1 A converging rod lens having a refractive index that is highest on the axis and decreases parabolically toward the periphery is installed between the even number of opposing optical fibers, with L/4, nL/2 , L/4(
However, L is the period length, n is an integer), and n
An optical switch characterized in that a rod lens having a length of L/2 is switched to a rod lens having a length of (n+1)L/2. 2. The optical switch according to claim 1, wherein the refractive index distributions of the 2 nL/2 rod lens and the (n+1)L/2 rod lens are made to be different so that the lens lengths are equal in actual size. .