JPH03236014A - Optical switch - Google Patents

Abstract

PURPOSE:To provide the optical switch which is low in insertion loss and has high performance with ease at a low cost by providing a total reflecting mirror between a pair of planar optical waveguides having a parabolic shape in such a manner that this mirror can be inserted and retreated. CONSTITUTION:The total reflecting mirror 5 is disposed between a pair of the planar optical waveguides 6a and 6b having the end face of the parabolic shape in such a manner that this mirror can be inserted and retreated. The guided light from an optical fiber 1a of the entrance port existing in one focal position of the parabola is reflected by the end face of the parabola so as to be paralleled with the major axis of the parabola and is emitted from the optical fiber 1d existing in the focal position of the optical waveguide 6b opposite thereto while the mirror 5 is held retreated. The entering light of the optical fiber 1a is switched to the optical fiber 1b in the other focal position when the mirror 5 is inserted. Since the optical waveguides on the same substrate are used, the propagation loss is low and since the waveguides are not moved, the cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical switches. More specifically, the present invention relates to an optical switch configured using a planar optical waveguide, and in particular to a novel optical switch configuration that can be advantageously applied to forward path switching for optical communication. .

2. Description of the Related Art As optical communication technology advances, various complex optical signal transmission systems are being constructed.

One of the optical devices most frequently used in such optical signal transmission systems is an optical switch, and in particular, an optical switch that has the function of switching optical transmission lines is indispensable in the configuration of any optical system.

FIGS. 4(a) and 4(b) are diagrams showing a typical configuration example of a known optical switch and its operation, as described in Paper B660 published by the Institute of Electronics, Information and Communication Engineers in 1988.

As shown in the figure, this optical switch includes a pair of blocks 33 and 34 on which the front ends of three optical fibers 31a to 31C and 32a to 32C are respectively mounted. 1
The pairs of blocks are arranged adjacent to each other, and usually one is fixed and the other is configured to be movable in the direction indicated by the arrow in the figure by an actuator (not shown). Moreover, each optical fiber 31a to 31a to 32a to c is
When the blocks 33 and 34 face each other, the optical fibers 31
A and 32a, 31b and 32b, and 31C and 32c are arranged so as to be optically coupled to each other.

In addition, in the optical switch shown in FIG. 4, the optical fiber 31a
The rear end and the rear end of the optical fiber 32C are coupled by an optical fiber 35 for connection. In addition, the optical fiber 31
The rear end of b connects optical fiber 3 to the input port from the optical transmission line.
The rear ends of 1C are respectively coupled to optical transmitters 36,
On the other hand, the rear end of the optical fiber 32a is coupled to an optical receiver 37, and the rear end of the optical fiber 32b is coupled to an output port to an optical transmission line.

FIG. 4(a) shows the normal mode state of this optical switch. That is, in this state, the propagating light that has entered from the input port is input to the receiver 37 via the optical fibers 31b and 32a. Further, the optical signal emitted from the transmitter 36 is sent to the output port via the optical fiber 31C and the optical fiber 32b. Therefore, a device (not shown) including the receiver 36 and transmitter 37 is bidirectionally coupled to an optical transmission path (not shown) connected to the input port and the output port.

On the other hand, No. 41D(b) shows the bypass mode of this optical switch. That is, when either block 33 or 34 moves and the two face each other directly, optical fibers 31a and 32a, 31b and 32b, and 31C and 32C are coupled, respectively. Therefore, in this state, the propagating light injected from the input port is directly transmitted to the output port via the optical fibers 31b and 32b.

On the other hand, the optical signal output from the transmitter 36 is transmitted through the optical fiber 3.
1c, 32c, 35.31a and 32a directly to the receiver 37. Therefore, the device including the receiver 36 and the transmitter 37 is disconnected from the optical transmission line (not shown) connected to the input port and the output port.

By operating as described above, this optical switch is used for operations such as connecting or disconnecting a specific node from the bus in an optical LAN system, for example.

In addition, FIG. 5(a) and 5(a) show another example of a conventional optical switch, as shown in the paper C4 of the Institute of Electronics, Information and Communication Engineers published in 1985.
92 is a diagram showing the configuration and operation of the optical switch described in No. 92.

The state of the normal mode is shown in FIG. 5(a), and the state of the switching mode is shown in FIG. 5(a).

As shown in the figure, this optical switch mainly consists of two pairs of optical fibers 41a and 42a and 41b and 42b facing each other, and a square prism 43 disposed between these two pairs of optical fibers. It is configured. Note that the prism 43 is configured to be rotatable by an actuator (not shown).

FIG. 5(a) is a diagram showing the normal mode of this optical switch, in which each optical fiber 41a141b,
The end face of the prism 43 is configured to be at an angle of 45° with respect to the optical axis at the ends of the prisms 42a and 42b. Therefore, in this state, the output light emitted from one of the optical fibers, for example 41a and 41b, enters the end face of the prism 43 at right angles, and then enters the optical fiber 42a facing the prism 43.
and 42b.

FIG. 5(b) is a diagram showing the switching mode of this optical switch. At this time, each optical fiber 41a, 41b, 4
With respect to the optical axis at the ends of 2a, 42b, the prism 4
3 is rotated so that its end face is at a right angle, and the light emitted from the optical fibers 41a and 41b enters the end face of the prism 43 at an angle. Therefore, each emitted light is refracted when entering the prism 43 and when exiting the prism 43,
The connection state of the propagating light changes. That is, the optical fiber 41a
The emitted light is injected into the optical fiber 42b, and the output light from the optical fiber 4
The emitted light from 1b is injected into the optical fiber 42a.

Through the above-described operation, this optical switch can switch the connection state of two pairs of optical transmission lines.

Problems to be Solved by the Invention The conventional optical switch shown in FIG. 4 is configured to change the coupling state by mechanically displacing a block holding an optical fiber. Therefore, when manufacturing it, the desired function cannot be obtained unless the positioning and displacement of the blocks are controlled very precisely. Furthermore, in the optical switch shown in FIG. 5 as well, the shape and optical quality of the prism itself, as well as its arrangement and amount of rotation must be controlled with extremely high precision. Optical switches that require such precise machining and assembly inevitably end up being extremely expensive.

In addition, with conventional optical switches that mechanically operate optical devices that propagate optical signals, the connection state of the transmission line changes slightly depending on the position of the flock or prism, making it difficult to maintain low insertion loss. There are also problems.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and provide a novel optical switch that is easy to manufacture and inexpensive, and has a stable and low insertion loss. .

According to the means for solving the problem, that is, the present invention, first and second end surfaces draw straight lines parallel to each other, and a third end surface each draws a part of a parabola.
a pair of first and second planar optical waveguides, each of which has a horizontal cross-sectional shape defined by a first end face and a fourth end face, the first end faces facing each other in parallel and being formed on the same plane; ; a total reflection mirror that can be inserted between the pair of first end surfaces in parallel to the first end surface; and one pair of incident light coupled to each of the eight second end surfaces of the first and second planar optical waveguides. an optical switch with a port or an output port: the first
and in the second leading waveguide, the third end surface is
and a parabolic shape having a major axis at a predetermined angle that is not perpendicular to the second end surface and having a focal point on the second end surface, and the fourth end surface is The second planar optical waveguide has a horizontal cross-sectional shape that is axisymmetric with the third end surface about a predetermined straight line that intersects both of the second end surfaces at a right angle. has the same shape as the waveguide and is arranged symmetrically about a straight line parallel to the first end surface; the input port or the output port coupled to the first and second planar optical waveguides; , one at each focal point of a parabola defining the third and fourth end surfaces of each planar optical waveguide; and a second position where it retreats from the area sandwiched between the first end faces of the first and second planar optical waveguides. An optical switch is provided.

Operation The optical switch according to the present invention has a unique configuration consisting of a pair of planar optical waveguides having a predetermined shape and one total reflection mirror.

That is, the main feature of the optical switch according to the present invention is that it uses a planar waveguide whose side surface has an end face shaped like a parabola. As detailed below,
In the optical switch according to the present invention, guided light is injected into a planar optical waveguide having such a shape from a port coupled to a position corresponding to the focal point of the parabola. Therefore,
The light that propagates within the planar optical waveguide and is reflected by the parabolic end face becomes a light ray parallel to the long sleeve of the parabola formed by this end face. Such parallel light rays are emitted from the end face of each planar optical waveguide on the opposite side to the incident side, and are again injected into the facing planar optical waveguide having the same shape.

Here, the parallel light beam injected into the facing second planar optical waveguide propagates as a light beam parallel to the long axis of the parabola formed by the end face of the second planar optical waveguide.

Therefore, the parallel light beam reflected by the parabolic end face of the second planar optical waveguide converges at the focal point of the parabola. Thus, in one or more such processes the propagating light can be extracted from the port coupled to the focal point of this second planar optical waveguide, the light injected into the parabolic focal point in one planar optical waveguide is no longer The light is emitted from the focal point of a symmetrical parabola of one planar optical waveguide.

Further, when a total reflection mirror is inserted between the end faces of the pair of planar optical waveguides, the injection light emitted from one of the planar optical waveguides is again injected into the planar optical waveguide as a parallel beam. The parallel light beam reinjected into the original planar optical waveguide is reflected by the parabolic end face opposite to the first reflected parabolic end face, and converges at the focal point of the parabola. Therefore, light injected from the negative port is emitted from the port connected to the other focal point.

As a result of the above-described effects, in the optical switch according to the present invention, depending on whether or not a total reflection mirror is inserted, the light incident on one port can be emitted from the port connected to the other planar optical waveguide. It is possible to switch whether the light is emitted from the other port of the planar optical waveguide into which it was first injected.

Furthermore, a 2×2 switching optical switch can be constructed by connecting a port to each pair of focal points of each guide waveguide and using a double-sided total reflection mirror as the total reflection mirror to be inserted.

In such an optical switch according to the present invention, all the leading waveguides in the switch are formed on the same substrate, so there is no need to adjust the optical axis between the waveguides during assembly.

In addition, since light enters or exits from the focal point of the parabola for each leading waveguide whose side end face is shaped like a parabola, each light beam is Be tolerant of filter alignment accuracy. Further, the total reflection mirror only needs to be parallel to the mutually opposing end surfaces of each planar optical waveguide when inserted, and its initial position, amount of movement, and position at the destination can be easily controlled.

Therefore, compared to conventional optical switches, it can be manufactured through a much easier manufacturing process, and its manufacturing cost is significantly reduced. Furthermore, since each guide waveguide is a planar optical waveguide integrally formed on one substrate, propagation loss is small, resulting in an optical switch with low insertion loss.

Note that the shapes of the pair of planar optical waveguides and the substrate that supports them can be selected as appropriate depending on the application, but when no total reflection mirror is inserted, Since it is necessary to propagate the light beam to the optical waveguide, care must be taken to ensure that the distance between the two does not become excessive. Furthermore, light leaks to the outside through the gap between the pair of planar optical waveguides, so from this point of view as well, it is preferable that the distance between them be narrow.

Hereinafter, the present invention will be described in more detail with reference to the drawings, but the following disclosure is only one embodiment of the present invention, and does not limit the technical scope of the present invention in any way.

Embodiment FIG. 1 is a diagram showing a specific example of the configuration of an optical switch according to the present invention.

As shown in the figure, this optical switch is mainly composed of a pair of planar optical waveguides 6a and 6b whose front ends face each other, formed on a substrate 2, and a movable total reflection mirror 5. . Further, a pair of optical fibers 1a and 1b and lc and 1d are coupled to the rear end of each planar optical waveguide 6a and 6b as an input port or an output port, respectively. In addition, each planar optical waveguide 6 is provided at the center of the substrate 2.
A groove 7 is provided by removing the substrate 2 between the end faces of a and 6b. According to a preferred embodiment of the present invention, the planar optical waveguide 6a exposed in the groove 7,
The end face of 6b is coated with a non-reflective coating.

The total reflection mirror 5 has total reflection characteristics on both sides and is configured to be movable within the groove 7.

That is, it is configured so that it can take a first position that avoids the area between the end faces of the planar optical waveguides 6a and 6b facing each other, and a second position that completely blocks the space between them. The total reflection mirror 5 is configured to be parallel to the end surfaces of the planar optical waveguides 6a and 6b at least in its second position.

FIGS. 2(a), (b), (C), and (d) are diagrams for explaining the detailed configuration and operation of the optical switch shown in FIG. 1.

As shown in FIG. 2(a), each of the planar optical waveguides 6a and 6b has the same shape, and herein, the planar optical waveguide 6a will be explained.

The horizontal cross-sectional shape of the planar optical waveguide 6a is parallel to each other.
and second end faces 61a and 62a, and third and fourth end faces 6 each drawing a part of a parabola as described later.
3a and 64a. The shape of the third end surface 63a is defined by the shape of the y-axis having a predetermined angle with respect to the first and second end surfaces 61a and 62a, and the y-axis perpendicular to the y-axis (y=ax" ]
The focal point F of this parabola is located on the second end surface 62a. Further, the fourth end surface 64 is connected to the first and second end surfaces 6.
The shape is such that the line is 1-symmetric with respect to the third end surface 63a, with the straight line A perpendicular to 1a and 62a as an axis. Therefore, the focus F of the parabola drawn by the fourth end surface 64a
, 1 are also located on the second end surface 62a. still,
Optical fiber la serving as an input port or an output port.

and 1b have focal points F0 and Fl on their respective second end faces.
, l, respectively.

The second planar optical waveguide 6b is arranged line-symmetrically with the first planar optical waveguide 6a with respect to the total reflection mirror 5 inserted therebetween, and has exactly the same shape.

Further, the optical fibers 1c and 1d, which serve as the input port or the output port for the second planar optical waveguide 6b, are also at the focal points F2 and F2° of the parabola drawn by the end surfaces 63b and 64b.
is combined with

Each of the planar optical waveguides 6a and 6b is fabricated by, for example, forming optical glass BK7 by exchanging B+ and Na'' by an ion exchange method, and then forming grooves 7 by an ion milling method or a grinding method. At this time, the shape of the waveguide can be controlled by utilizing lithography technology and using a mask to limit the location where ions are exchanged.

It is preferable that the thicknesses of the planar optical waveguides 6a and 6b match the core diameters of the optical fibers la, lb, IC, and 1d to be coupled. In addition, the planar optical waveguides 6a and 6
In order to improve the reflection characteristics on each side of b, as shown in FIG.
It is also effective to remove areas other than the waveguide on the surface of the substrate 2.

In FIG. 3, the same components as in FIG. 1 are given the same reference numerals.

Further, it is preferable that the input/output end faces of the planar optical waveguides 6a and 6b be coated with anti-reflection coating as described above, and specifically, an Mgf thin film formed by vapor deposition or sputtering can be applied.

The total reflection mirror 5 can be made of a multilayer film of 5iO7 and TiO7.

The optical switch configured as described above operates as follows.

FIG. 2 et al.) are diagrams showing the propagation state of the injected light when the total reflection mirror 5 is not inserted between the planar optical waveguides 6a and 6b.

As shown in the figure, among the light injected from the optical fiber 1a, which is the input port, into the planar optical waveguide 6a, the end face 63a
The propagating light reflected by the long axis of the parabola drawn by the end face 63 (
y-axis) and is emitted from the end surface 61a. This parallel light beam enters the planar optical waveguide 6b from the end face 61b, is reflected by the end face 64b, converges at the focal point F2', and is extracted from the optical fiber 1d. Although not shown in the figure, the optical fiber 1b and the optical fiber 1c are also
are similarly connected. That is, the optical switch in the state shown in FIG. 2(b) forms the following two-system coupled state.

FIG. 2(C) shows that in the optical switch shown in FIG.
FIG. 2 is a diagram showing the function of an optical switch when a total reflection mirror 5 is inserted between a pair of planar optical waveguides 6a and 6b.

As shown in the figure, among the light injected into the planar optical waveguide 6a from the optical fiber 1a, which is the input port, the propagating light reflected at the end face 63a is transmitted along the long axis (y) of the parabola drawn by the end face 63.
The light beam is emitted from the end surface 61a as a light beam parallel to the axis).

This parallel light beam is once emitted from the end surface 61a of the planar optical waveguide 6a, is reflected by the total reflection mirror 5, and is reflected by the end surface 61a of the planar optical waveguide 6a.
From 1a, the light enters the planar optical waveguide 6a again. At this time, the reflected light incident on the planar optical waveguide 6a becomes a ray parallel to the long sleeve (y' axis) of the parabola drawn by the end surface 64a.

Therefore, when this parallel ray is reflected by the end surface 64a,
It converges on the focal point FI' and is extracted from the optical fiber 1b. Note that when both surfaces of the total reflection mirror 5 have total reflection characteristics, the optical fibers lc and 1d are similarly coupled in the planar waveguide 6b.

That is, the optical switch in the state shown in FIG. 2(b) forms the following two-system coupled state.

Through the above-described operation, the optical switch shown in FIG. 1 realizes a 2×2 switching function.

Note that each end face 61a of the pair of planar optical waveguides 6a and 6b
The distance l between the total reflection mirror 5 and 61b is the total reflection mirror 5 inserted between them.
It can be selected as appropriate depending on the dimensions, etc., but as shown in FIG. 2(d), if the distance l is excessively large, optical coupling between the two will not be formed, so it should be made as narrow as possible. It is preferable to design.

As described in detail, the optical switch according to the present invention is composed of a pair of planar optical waveguides having a unique shape and a total reflection mirror. Here, the guided light to be processed propagates in a planar waveguide formed on one substrate, and this planar optical waveguide does not perform any mechanical operation. Therefore, its function and insertion loss do not depend on assembly accuracy and do not require precise adjustment, so that manufacturing man-hours and manufacturing costs can be reduced.

Furthermore, the light transmission path within the optical switch is a planar optical waveguide, and the number of times the light propagates to different media is small, so transmission loss is also reduced.

The optical switch according to the present invention having such characteristics can be advantageously used as an inexpensive and high-performance optical switch in a simple optical local area network and the like.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a specific configuration example of the optical switch according to the present invention, and FIG. FIG. 3 is a diagram showing another embodiment of the optical switch according to the present invention, and FIGS. 4(a) and (6) are diagrams illustrating the operation of the conventional optical switch. FIGS. 5(a) and 5(b) are diagrams showing a typical configuration example of another conventional optical switch and its operation. FIGS. [Main reference numbers] la, lb, IC, ld. 31a, 31b, 31c, 32a, 32b, 32c, 3
5.41a141b142a142b...Optical 7 fiber, 2...Substrate, 5...Total reflection mirror, 6a, 6b...Planar optical waveguide, 7...Groove, 33.34...Block, 36 ...Transmitter, 37...Receiver 61a, 61b...First end surface, 62a, 62b...Second end surface, 63a, 63b...Third end surface, 64a, 64b. Fourth end face

Claims (1)

[Scope of Claims] A horizontal cross-sectional shape defined by first and second end faces that draw straight lines parallel to each other, and third and fourth end faces that each draw a part of a parabola, and each The first end faces face each other in parallel and are formed on the same plane.
and a second pair of planar optical waveguides; a total reflection mirror that can be inserted between the pair of first end surfaces in parallel to the first end surface; each of the first and second planar optical waveguides; an optical switch having a pair of input ports or output ports coupled to each of two end faces; in the first and second optical waveguides, the third end face is
The fourth end surface has a parabolic shape having a major axis at a predetermined angle that is not perpendicular to the first and second end surfaces and has a focal point on the second end surface. 1st and 2nd
The second planar optical waveguide has a horizontal cross-sectional shape that is line symmetrical to the third end surface about a predetermined straight line that intersects at right angles to both end surfaces of the first planar optical waveguide. The input port or the output port coupled to the first and second planar optical waveguides has the same shape as and is arranged symmetrically about a straight line parallel to the first end surface; One total reflection mirror is coupled to each focal point of a parabola that defines the third and fourth end surfaces of each planar optical waveguide; It is configured to be movable between a first position where it shields the sandwiched region and a second position where it retreats from the region sandwiched between the first end faces of the first and second planar optical waveguides. An optical switch characterized by: