JPS6154204B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switch used in optical fiber communication equipment, etc., and more particularly to a small, high-performance, and easy-to-assemble optical switch that can switch optical paths between a large number of optical fibers. .

Conventionally, optical switches (hereinafter referred to as m-channel optical switches, where m is a positive integer) capable of switching optical paths between a large number of optical fibers have the structure shown in FIG. The structure shown in the figure has been reported. The example shown in Figure 1 is a 4-channel optical switch described in Proceedings 856 of the National Conference of the Institute of Electronics and Communication Engineers in 1981. FIG. 1a shows an overall perspective view, and FIG. 1b shows a cross-sectional view. Switching of the optical path between the optical fiber 101 and the connected fibers 102, 103, 104, and 105 is performed using a rectangular parallelepiped iron block 1 that is attached in a shape that the optical fiber 101 passes through.
06 with four electromagnets 107, 108, 109, 1
10 to the four corners of the acrylic case 111 and abut the optical fibers against each other. In such an optical switch, since the optical fiber itself is moved, the mechanical damage to the optical fiber is considered to be large, and during assembly, the connected fibers 102, 103, 104
This method has drawbacks such as having to adjust the wires 105 one by one and fixing them at optimal positions. The example shown in Figure 2 is a four-channel optical switch that was also described in Proceedings of the 1986 National Conference of the Institute of Electronics and Communication Engineers. Figure 2 a shows the overall perspective view;
FIG. b shows a diagram of the principle. optical fiber 201
The light emitted from the beam is made into a parallel beam by a convergent light transmitter (hereinafter referred to as a rod lens) 206,
The light is reflected in the right angle direction by the rotating mirror 211 and enters the rod lens 207, where it is refocused and coupled into the optical fiber 202. When the rotary mirror 211 is rotated by the step motor 212, the light emitted from the optical fiber 201 is transferred to the optical fibers 203 and 20.
It can also be combined with 4,205,206,
Optical fiber 201 and optical fibers 202, 203,
204 and 205 can be switched. This type of optical switch has the advantage that there is no need to move the optical fibers themselves, and there is less mechanical damage. This method has drawbacks such as high material costs because it must be adjusted and fixed, and one rod lens with a length of 1/4 pitch is required for each fiber to be connected.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to provide an m-channel optical switch that causes less mechanical damage, allows the selection of any channel, is easy to assemble, is inexpensive, compact, and has high performance. .

According to the present invention, a first optical fiber having an outer diameter d ₁ and n fibers having an outer diameter d ₂ smaller than the outer diameter d ₁ densely arranged on the circumference of the first optical fiber (n is positive integer), and d ₁ = d ₂ (1-sin
The optical fiber bundle has a relationship of π/n)/sinπ/n and two end faces perpendicular to the central axis, and a total reflection film is provided on the end face on the side not adjacent to the optical fiber. a rod lens having a length of about 1/4 of the meandering pitch of the light, the rod lens having the end surface having the total reflection film facing the end surface of the optical fiber bundle, and the central axis of the rod lens being the center of rotation. a rotating body that is housed eccentrically by 1/4 (d ₁ + d ₂ ) from the axis, and whose central axis of rotation substantially coincides with the central axis of the first optical fiber; rotating the rotating body so as to coincide with any one of n lines bisecting the distance between the central axis of the optical fiber and the central axis of each of the second to n+1 optical fibers; An optical switch is obtained which is characterized in that it switches the optical path and, instead of the first optical fiber, an outer diameter d ₁
An optical switch characterized in that it uses an optical fiber housed in a cylinder with its central axis aligned with the optical fiber.

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 3 shows an embodiment of the configuration of an optical fiber bundle terminal according to the present invention. This embodiment is a case of a 10-channel optical switch, in which a first optical fiber 301 with an outer diameter of d ₁ is surrounded by a first optical fiber 301 with an outer diameter of d ₂ .
The second to eleventh optical fibers 302 to 31 are
1, 10 are placed. Here, between the outer diameter _d1 of the first optical fiber 301 and the outer diameter _d2 of the second to eleventh optical fibers 302 to 311, _d1 = _d2 (1-
The following relationship holds true: sinπ/10)/sinπ/10.
Therefore, if the second to eleventh optical fibers 302 to 311 are arranged on the circumference of the first optical fiber 301 so that their outer circumferences touch each other, the first optical fiber 301 becomes the center. 2nd to 11th optical fibers 302
311 can be arranged closely together on the circumference of radius 1/2 (d ₁ +d ₂ ) and at equal intervals on the circumference with high accuracy. In practice, the core diameter of the first optical fiber 301 and the second to eleventh optical fibers 302 to 311 are
It is desirable that the core diameters of the two are approximately the same. At this time, the ratio of the core diameter to the outer diameter of the first optical fiber 301 is different from the ratio of the core diameter to the outer diameter of the second to eleventh optical fibers 302 to 311. By the way, due to the remarkable improvement in fiber manufacturing and spinning technology in recent years, fiber fibers with an arbitrary ratio of core diameter to outer diameter have been made.
The optical fiber 301 can be obtained with high dimensional accuracy.

FIG. 4 is a diagram showing an embodiment of a 10-channel optical switch constructed using the fiber bundle terminal shown in FIG. 3. FIG. 4 shows a partially cutaway perspective view, and FIGS. 5 and 6 show the principle of operation of the optical switch.

Referring to FIG. 4, a rotation support 402 is attached to the rotation shaft of a step motor 403, and a rod lens 401 whose length is 1/4 the pitch of the meandering light is loaded onto the rotation support 402. has been done. Here, the central axis of the rod lens 401 is eccentrically located by 1/4 (d ₁ + d ₂ ) from the rotational central axis of the rotational support 402 . However, d ₁ is the outer diameter of the first optical fiber 301, and d ₂ is the outer diameter of the second to eleventh optical fibers.
is the outer diameter of the optical fibers 302 to 311. A total reflection film R is applied to one of the two end faces of the rod lens 401. In addition, the optical fiber 301 is placed close to the end face on which the total reflection film R is not applied
An optical fiber bundle consisting of .about.311 is arranged such that its central axis coincides with the central axis of the rotating support. Here, to explain the optical principle of coupling between optical fibers, as described in IEICE Photonics and Quantum Electronics Study Group material OQE76-88, one of the authors of which is one of the inventors of this application. , the light emitted from the optical fiber 301 located at the center of the densely arranged optical fibers was transmitted through the rod lens 401 at approximately 1/4 pitch of the meandering pitch, where it became almost parallel and the size of the spot expanded. The beam becomes a beam, is reflected by the total reflection surface R, and propagates through the rod lens 401 again, and at the end face of the rod lens 401, the beam is converged again and connected to the optical fiber (any one of the optical fibers 302 to 311) to be coupled. is combined with Next, the optical path switching mechanism will be explained using FIGS. 5 and 6. In FIG. 5, the central optical fiber 301 is arranged on the rotation center axis _c1 , 311 are arranged at equal intervals on the circumference of a radius 1/2 (d ₁ +d ₂ ) centered on the rotation center axis c ₁ . The light emitted from the optical fiber 301 enters the rod lens 401, is reflected by the reflective film R provided on one end face of the rod lens 401, and is located at a position axially symmetrical to the optical fiber 301 with respect to the central axis _c2 of the rod lens 401. Coupled to optical fiber 302. FIG. 6 shows the rotation center axis c ₁ of the rod lens 401 from the state of FIG. 5.
The figure shows the state in which the light from the optical fiber 301 is coupled to the optical fiber 303 by rotating the optical fiber 301 by about 36 degrees. Similarly, light from optical fiber 301 can also be coupled into optical fibers 304-311. As described above, Rod lens 40
1 around the rotation center axis _c1 , the optical fiber 301 and the optical fiber 302 to
The optical path can be switched between 311 and 311.

In the above embodiment, as shown in FIG. 3, the ten optical fibers are arranged around one optical fiber 301 having a larger outer diameter than the ten optical fibers, but as shown in FIG. ₂ are equal optical fibers 501-51
1, the optical fiber 501 is formed into a cylinder 5 with an outer diameter of d ₃ .
12 and an optical fiber 502 around it.
It is also clear that a structure of an optical fiber bundle in which .about.511 are arranged may be sufficient. In this case, the outer diameter of the cylinder 512
d ₃ and the outer diameter d ₂ of the optical fibers 502 to 511
It goes without saying that if the outer diameter of the cylinder is determined so that d ₃ =d ₂ (1-sin π/n)/sin π/n, an optical switch similar to that of the previous embodiment can be obtained.
Also, the length of the focusing optical transmission body used in this invention is 1/
It is clear that the length is not limited to 4 pitches, but may be an odd number multiple of 1/4 pitch.

Finally, the features of the present invention are listed as follows:
It is easy to assemble because it is possible to use an optical fiber bundle terminal that brings together a book of optical fibers and this optical fiber, or a plurality of optical fibers arranged concentrically around a cylinder containing the optical fibers. , by appropriately selecting the ratio of the outer diameter of the optical fiber placed at the center of the optical fiber bundle to the outer diameter of the optical fiber placed on its circumference, an optical switch with any number of channels of 3 or more can be obtained; The optical fiber is fixed and is not susceptible to mechanical damage, so it is highly reliable as an optical switch, requires only one rod lens, so it is inexpensive, and uses a small step motor. This makes it possible to reduce the overall size of the optical switch to approximately 25mmφ x 40mm, making it compact, and by applying anti-reflection coating to the end faces of the optical fiber and rod lens that meet, the insertion loss of light in the optical switch is minimized. It is capable of high performance, etc.

[Brief explanation of the drawing]

Figures 1a and b are a partially cutaway perspective view and sectional view of a conventional structure, respectively; Figures 2a and b are a partially cutaway perspective view and a principle diagram of a conventional structure; Figures 3 and 7 are FIG. 4 is a partially cutaway perspective view of the embodiment of the present invention, and FIGS. 5 and 6 show the switching operation state of the optical switch of the present invention. FIG. 301-311... Optical fiber, 401... Rod lens, 402... Rotating body, 403... Step motor, R... Total reflection surface, 501-511...
...Optical fiber, 512...Cylinder.

Claims (1)

[Scope of Claims] 1. An optical fiber bundle including a first optical fiber with an outer diameter d ₁ and a plurality of optical fibers with an outer diameter d ₂ arranged in a dense structure around the optical fiber. , the refractive index distribution decreases approximately in proportion to the square of the distance from the central axis placed on the end face of this optical fiber bundle, and the pitch at which light propagates in a meandering manner is approximately (2N−
1) a rod lens having a length of /4 pitch (N is a positive integer) and two end faces perpendicular to the central axis, and a reflective film formed on the end face opposite to the optical fiber bundle side; The rod lens is held such that the center axis of the rod lens has a rotation center axis on the center axis of the first optical fiber, and the center axis of the rod lens is located at a position offset by 1/4 (d ₁ + d ₂ ) from the rotation center axis. 1. An optical switch comprising: a rotating support; the rotating support is rotated to switch the optical path between the first optical fiber and a predetermined optical fiber forming the dense structure. 2. A cylindrical member with an outer diameter d ₃ in which a first optical fiber with an outer diameter d ₁ is housed so that their central axes coincide with each other, and a cylindrical member with an outer diameter d ₂ arranged so as to form a dense structure on the circumference of this cylindrical member. An optical fiber bundle including a plurality of optical fibers, a refractive index distribution that decreases approximately in proportion to the square of the distance from the central axis arranged at the end face of the optical fiber bundle, and a pitch agreement in which light propagates in a meandering manner. A rod lens having a length of (2N-1)/4 pitch (N is a positive integer) and two end faces perpendicular to the central axis, and a reflective film formed on the end face opposite to the optical fiber bundle side. The rod lens has a central axis of rotation on the central axis of the first optical fiber, and the rod lens is positioned such that the central axis of the rod lens is located at a position offset by 1/4 (d ₃ + d ₂ ) from the central axis of rotation. 1. An optical switch comprising: a rotating support for holding the optical fiber; and rotating the rotating support to switch the optical path between the first optical fiber and a predetermined optical fiber forming the dense structure.