JPH0323430A - Optical switch - Google Patents

Abstract

PURPOSE:To enable fast operation and multi-mode optical switching by making the optical axis of the crystal of an input/output part and the optical axis of the crystal of a center part for optical path conversion opposite in direction, utilizing a large refractive index difference obtained by impressing an electric field selectively by an electrode couple, and switching an optical path by refraction on a border surface slanting to waveguide light. CONSTITUTION:When a voltage is impressed to electrode couples 27a and 27b, waveguide light guided in input part crystal parts 21 and 22 is refracted large by the oblique border surface 26 of the center part crystal 23 for optical path conversion and travels to output part crystal parts 24 and 25 which are different from crystal parts at the time of straight traveling. Further, the light is refracted large even by the oblique border surface 26 between the center crystal 23 for optical path conversion and output part crystal parts 24 and 25 and outputted from those output part crystal parts 24 and 25. Thus, couples of input part crystal parts 21 and 22 and output part crystal parts 24 and 25 are provided on an input and an output side for the center part crystal 23 for optical path conversion, and the input and output sides are combined mutually when the voltage is impressed and not impressed to enable the 2X2 multi- mode optical switching.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical switch that utilizes an electro-optic effect and is used in fields such as optical transmission using optical fibers and optical alarm processing.

2. Description of the Related Art Conventionally, there is an optical switch for a mallet that utilizes an electro-optic effect, as shown in FIG.

First, on a substrate made of an electro-optical material such as LiNbO, transparent regions having a refractive index higher than that of the substrate, for example regions (=optical waveguides) in which Ti is thermally diffused, are placed close to each other and parallel to each other. It is said to be a three-dimensional optical waveguide formed in Electrode pairs 4a, 4b, 5a are parallel to such a waveguide.
, 5b are formed. Therefore, these electrode pairs 4,
By applying a voltage to the waveguide 5, the refractive index of the waveguide is changed by the electro-optic effect, the optical coupling of the optical waveguide 2.3 is electrically controlled, and the output waveguide is switched.

However, although such optical switches exhibit excellent switching performance for single-mode waveguides, the extinction ratio decreases for multi-mode waveguides where the waveguide width is large, etc. Performance will deteriorate.

For this reason, an optical switch compatible with multimode waveguides is disclosed in Japanese Patent Application Laid-Open No. 121024/1983. Figure 6 shows the optical switch.
First, a transparent thin film 7 having a refractive index higher than that of the substrate 6 is formed on a substrate 6 such as glass to form a slab waveguide 8. On the transparent thin film 7, a parallelogram-shaped thin plate 9 made of an electro-optical material such as KDP, which has a refractive index lower than that of the slab waveguide 8, is arranged so as to obliquely cross the guided light from the input fiber 10. It is set in. A pair of electrodes 11a and Ilb are formed on this thin plate 9 to sandwich the guided light.

Therefore, electrode pair 1. Applying a voltage between Ia and 1lb,
The refractive index of the thin plate 9 is changed, and the slab waveguide 8 below it is
By controlling the equivalent refractive index of the transparent thin film 7, the optical path to the output fibers 12 and 13 is switched.

There is also an optical switch as disclosed in Japanese Patent Laid-Open No. 60-192926. FIG. 7 shows the optical switch.

This consists of two electro-optic crystals 14.15 in the shape of a right triangle.
crystal composite light that is integrated by touching the guided light from the input fiber 16, 17 at oblique boundary surfaces 14a, 15a, with the optical axes facing in opposite directions as shown by arrows A and B. It's a switch. These electro-optic crystals 14.1
Electrode pairs l8a and +8b are provided on both sides of the electro-optic crystals 14, 15 to generate an electric field parallel to the optical axis. Therefore, these electrode pairs 18a, 18
When a voltage is applied between b, the polarity of the refractive index change becomes opposite between the electro-optic crystal 14 and the electro-optic crystal 15, whose optical axes are in opposite directions. The refraction of light due to the difference in refractive index between the electro-optic crystals 14 and 15 is used to switch the optical path to the output fibers 19 and 20.

Problems to be Solved by the Invention The optical switch shown in FIG. 6 can be used for multimode transmission lines. However, the slab waveguide 8
Since the switching operation is performed by changing the equivalent refractive index of , the change in refractive index is small and the angle of refraction of light is small, so the switching width of the optical path is restricted.

Furthermore, according to the optical switch shown in FIG. 7, since the polarity of the refractive index change due to the electro-optic effect is reversed for the electro-optic crystal 14.15, the difference in refractive index between the two at the interface can be made large. Can be done. However, since the guided light from the electro-optic crystal 15 enters the output fiber 19.20 at a certain angle, the coupling efficiency is poor.

Furthermore, although these optical switches are compatible with multi-modes, their basic operation is just an optical switch with input×output=1×N.

Means for Solving the Problem In the invention described in claim 1, at least two optical fibers whose optical axes are opposite to each other and are in contact with each other at a boundary surface obliquely intersecting the guided light are integrated.
a plurality of electro-optic crystals each consisting of one input crystal, a center crystal for optical path conversion, and two output crystals, and an electrode pair that generates an electric field parallel to the optical axis within these electro-optic crystals;
A power supply means for selectively applying a voltage to this electrode pair was constructed.

! l'J In the invention described in claim 2, there is provided an optical waveguide made of an electro-optic material formed on a substrate with the optical axis perpendicular to the substrate surface, and a boundary having a shape located on both sides of the optical waveguide and obliquely intersecting the guided light. A plurality of electrode pairs that generate an electric field parallel to the optical axis in the optical waveguide, including at least two pairs of input electrodes having surfaces and insulated from each other, a pair of center electrodes for optical path conversion, and two pairs of output electrodes. and a power supply means for selectively applying voltages in opposite directions to at least the input part electrode pair, the output part electrode pair, and the central part electrode pair for optical path conversion to these electrode pairs.

According to the invention recited in claim 1, no change in refractive index occurs in the plurality of electro-optic crystals when no voltage is applied to the electrode pair;
The guided light passes straight through the input crystal, the center crystal for optical path conversion, and the output crystal. When a voltage is applied to the electrode pair, a change in refractive index occurs in each electro-optic crystal, but since these crystals are integrally joined with their optical axes facing in opposite directions, there is a large refractive index between the crystals. It makes a difference. Therefore, the guided light guided into the input crystal is largely refracted at the oblique interface with the center crystal for optical path conversion, and travels toward the output crystal, which is different from when it travels straight. Further, the light is largely refracted at the oblique boundary between the optical path converting central crystal and the output crystal, and is output from the output crystal. Here, a pair of input crystals and an output crystal are provided on the input and output sides of the central crystal for optical path conversion, and the input and output sides are mutually connected when voltage is applied or when no voltage is applied. By combining these, 2×2 multimode optical switching becomes possible. In addition, it is easy to output in a state perpendicular to the output end face of the output crystal, and the coupling efficiency with the output fiber etc. is not impaired.

According to the second aspect of the invention, when no voltage is applied to each electrode pair, no refractive index change occurs in the optical waveguide made of the electro-optic material, and the guided light passes straight through the optical waveguide and is output. Next, when a voltage is applied to each electrode pair, a refractive index change occurs in the optical waveguide portion corresponding to each electrode pair. At this time, are the electrode pairs an input part electrode pair, an output part electrode pair, and a central part for optical path conversion?
By applying a voltage in the opposite direction to the Ilt pole pair, an electric field in the opposite direction is applied to the optical waveguide in the optical axis direction, and the refractive index difference between the regions corresponding to these electrode pairs becomes large. . Therefore, the guided light guided into the crystal corresponding to the pair of entrance electrodes is largely refracted at the part corresponding to the boundary surface of the oblique pair of central electrodes for optical path conversion, and is refracted to the central pair of electrodes for optical path conversion. Proceed through the corresponding crystal toward a region corresponding to a different pair of output electrodes than when traveling straight. Further, the light is largely refracted and output at the oblique boundary surface portion to the region corresponding to the output section @ pole pair. Here, one pair of input part electrodes and one pair of output part electrodes are provided on the input and output sides of the center electrode pair for optical path conversion, and the input and output electrodes are connected to each other when voltage is applied or when no voltage is applied. By combining the sides with each other, 2×2 multimode optical switching is possible.

Embodiment An embodiment of the invention set forth in claim 1 will be described based on FIGS. 1 and 2. FIG. First, five pieces of electro-optic crystals 21 to 25 made of LiNbO or the like are provided. The electro-optic crystal 23 is formed into a rhombus shape when viewed from above, and serves as a central piece for changing the optical path. The electro-optic crystals 21 and 22 are formed in the shape of a right triangle with a hypotenuse having a length corresponding to one side of the optical path converting central crystal 23, and serve as input crystals. The electro-optic crystals 24 and 25 are also formed in the shape of a right triangle with a hypotenuse having a length corresponding to one side of the optical path converting central crystal 23, and serve as output crystals.

These crystals 21 to 25 have optical axes oriented in the directions indicated by arrows A and B in FIG. 1 at t. As shown in the figure, there is a central crystal 23 for optical path conversion and the remaining crystals 2+, 22, 24.
．． 25, the crystal axes are in opposite directions. With such orientation, these crystals 2l to 25 form crystal 2.
3 as the center, they are integrated into a rectangular shape by close contact or adhesion at a boundary 26 that obliquely intersects the guided light. A pair of electrodes 27a and 27b to which a voltage is selectively applied by a power supply means (not shown) is provided over the entire surface of both surfaces of the rectangular crystal. In addition, the input fiber 28.29 is connected to the collimating lens 30.3 at the input end of the input crystals 21 and 22.
1. At the output end of the output crystal 24.25, the input fiber 32.33 is connected to the condensing lens 34.
．． 35.

In such a configuration, the light from the input fiber 28 is collimated by the collimating lens 30 and guided into the optical switch of this embodiment, specifically, into the input crystal 2l,
Becomes guided light. In this case, unless a voltage is applied between the electrode pair 27a, 27b, the refractive index of each crystal 21-25 does not change. Therefore, the guided light guided into the input crystal 21 travels straight as it is, passes through a part of the central crystal 23 for optical path conversion, the output crystal 24, and is condensed by the condensing lens 34 while entering the output fiber 32. Output. Thus, light from input fiber 28 is guided into output fiber 32. This is the same for, for example, light from the input fiber 29 side, which travels straight and is guided into the corresponding output fiber 33.

Consider the case where a voltage is applied between the electrode pair 27a and 27b. When an electric field is applied to the crystals 21 to 25 in the optical axis direction, the refractive index changes Δn due to the electro-optic effect. Here, a central crystal 23 for optical path conversion and other crystals 21,
22, 24.25, the optical axis is in the opposite direction, and the refractive index change also appears with opposite polarity. For example, the central crystal 2 for optical path conversion
If the refractive index change of 3 is Δn, other crystals 21, 22,
The refractive index change of 24.25 becomes -Δn. Therefore, the central crystal 23 for optical path conversion and the other crystals 21, 22, 24.2
The refractive index difference between the two and 5 is relatively large by 2·Δn. Therefore, from the input fiber 28 to the input crystal 2l
The guided light is refracted by an angle ψ (oblique to the guided light) at the interface 26 with the optical path converting central crystal 23, as shown by the imaginary line in FIG. Proceed through the central crystal 23 for conversion. Furthermore, this time it is refracted at the boundary 26 with the output crystal 25, converted into a state parallel to the manually guided waveguide light, travels straight through the output crystal 25, and passes through the condensing lens 35.
The light is focused and guided into the output fiber 33. Therefore, when a voltage is applied between the electrode pair 27a, 27b, light from the input fiber 28 is guided into the output fiber 33. This also applies to the light from the input fiber 29 side, which is refracted and guided into the output fiber 32.

Therefore, according to this embodiment, the extinction ratio is large and high-speed operation is possible, and the 2×2 multimode optical switch function can be easily achieved.

Next, an embodiment of the invention according to claim 2 will be described with reference to FIGS. 3 and 4. The optical switch of this embodiment is not composed of a plurality of pieces of electro-optic crystal as in the previous embodiment, but is based on a single rectangular electro-optic crystal. That is, the base is a slab waveguide 38 as an optical waveguide in which an electro-optic crystal 37 is grown on a rectangular substrate 36. Here, the electro-optic crystal 37 has its optical axis aligned with the substrate 36.
It is shaped so that it is perpendicular to the plane. A plurality of electrode pairs are formed on both sides of such a slab waveguide 38. First, as in the case of the input crystals 21 and 22, two input electrode pairs 3 9 a and 3 9 are formed in a right triangle shape.
b, 40a, and 40b are provided.

Further, as in the case of the optical path converting central crystal 23, one pair of optical path converting central electrodes 41a formed in a diamond shape,
4lb is provided.

Further, two pairs of output electrodes 42a and 42b formed in a right triangle shape as in the case of the output crystal 24.25,
43a and 43b are provided.

By combining these electrode pairs, the slab waveguide 38
However, in order to electrically insulate and separate adjacent electrode pairs, a slightly larger diamond-shaped frame is provided around the center electrode pair 41a, 4lb for optical path conversion. An insulating layer 44 is provided. A voltage is selectively applied to each of these electrode pairs by a power supply means (not shown), but as shown by arrows A and B in FIG. , 4lb, and the direction of the voltage applied between the other electrode pairs 39a, 39b, 40a.
, 40b, 42a, 42b, 43a, and 43b, the directions of the voltages are set to be opposite to each other. Further, the oblique sides of each electrode pair 39a to 43b form a boundary surface 45 obliquely intersecting the guided light. The slab waveguide 38, the electrode pairs 39a to 43b, or the insulating layer 44 can be easily formed by using a well-known technique such as a thin film formation technique, a delivery growth technique, or photolithography.

In addition, the input part electrode pair 39a, 39b of the slab waveguide 38
, 40a, 40b are connected to input fibers 46, 47.

Similarly, the output section of the slab waveguide 38? Ia pole pair 42a,
Output fibers 48 and 49 are coupled to the output end faces at positions corresponding to 42b, 43a, and 43b.

Here, in this embodiment, the collimated waveguide lens 5 is connected to the coupling part of the input fibers 46 and 47 of the slab waveguide 38.
0.51 is formed, and a waveguide lens 52.53 for focusing light is formed at the coupling part of the output fiber 48.49.

In this embodiment, these waveguide lenses 50 to 53 are formed as distributed index lenses by thermal diffusion of metal to the electro-optic component 37.

In such a configuration, light from input fiber 46 is collimated by waveguide lens 50 and guided through slab waveguide 38 . At this time, unless a voltage is applied between each electrode pair 39a to 43b, the electro-optic crystal 37 does not change its refractive index.

Therefore, the guided light guided from the input fiber 46 passes straight through the electro-optic crystal 37 and passes through the corresponding waveguide lens 5.
2 and output into an output fiber 48. This also applies to the light from the input fiber 47 side, which travels straight and is guided into the corresponding output fiber 49.

Consider the case where @rE is applied between each electrode pair 39a to 43b. When an electric field is applied to the electro-optic crystal 37 in the optical axis direction, the refractive index changes Δn. Here, the direction of the voltage applied between the center electrode pair 41a and 4lb for optical path conversion and the other electrode pairs 39a, 39b, 40a, 40b,
The direction of the voltage applied between 42a, 42b, 43a, and 43b is opposite to '? The refractive index change that occurs in the electro-optic crystal 37 corresponding to the r1 pole shape also appears in reverse polarity. For example, if the refractive index change in the region corresponding to the lit pole pair 41a, 4lb is Δn, then the other electrode pair 39a, 39b
, 40a, 40b, 42a, 42b, 43a, 43b, the refractive index change is −Δn. Therefore, the refractive index difference between these regions is relatively large by 2·Δn.

Therefore, from the input fiber 46 to the input part electrode pair 39a, 3
The guided light guided into the region corresponding to 9b is refracted at the boundary surface 45 corresponding to the hypotenuse, as shown by the imaginary line in FIG. However, it is also refracted at 45, and the center electrode pair 4 for optical path conversion is refracted.
Proceed through the area corresponding to 1a and 4lb. Furthermore, this time it is refracted twice at the boundary 45 with the output electrode pair 43a, 43b side, is converted into a state parallel to the input waveguide light, travels through the region corresponding to the output electrode pair 43a, 43b, and passes through the waveguide lens. 53 and guided into the output fiber 49. Therefore, when a voltage is applied to each electrode pair, the input fiber 46
The light from is guided into the output fiber 49. this is,
The same applies to the light from the input fiber 47 side, which is refracted and guided into the output fiber 48.

Accordingly, this embodiment also has a large light reduction ratio and is capable of high-speed operation, and can easily perform a 2×2 multimode optical switch function. In particular, according to this embodiment, the waveguide lenses 50 to 53 are formed in the output part of the electro-optic component 37, and the fibers 46 to 49
Since the optical switch element is coupled with the optical switch element, the coupling efficiency is improved and the optical switch element can be further miniaturized.

Effects of the Invention Since the present invention is configured as described above, according to the invention described in claim 1, the optical axes of the input/output part crystal and the central part crystal for optical path conversion are set in opposite directions, and the electrode pair selectively The optical path is switched by utilizing the large refractive index difference created by applying an electric field to the waveguide and refraction at the boundary surface obliquely intersecting the guided light, so the extinction ratio is large and high-speed operation is possible. A pair of input crystals and an output crystal are provided on the input and output sides of the optical path converting central crystal, and a voltage is applied to the electrode pair. ? By mutually combining the input and output sides with /no-applying B and 1, 2 x 2 multi-mode optical switching can be made possible, and the state is perpendicular to the output end of the output part crystal. It is easy to output the signal with a single electro-optic crystal, and it becomes possible to perform switching without impairing the coupling efficiency with the output fiber. With this structure, it can be easily manufactured by using techniques such as conventional thin film formation technology, crystal growth technology, or photolithography.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the invention as claimed in claim 1.
What about the 4th view and the 2nd view? ? FIG. 3 is an exploded perspective view showing an embodiment of the invention according to claim 2; FIG. 4 is a plan view showing the operation with the electrode pair omitted;
FIG. 5 is a perspective view showing a conventional example, FIG. 6 is a perspective view showing a different conventional example, and FIG. 7 is a perspective view showing a still different conventional example.

Claims (1)

[Claims] 1. At least two input crystals, a central crystal for optical path conversion, and two output crystals, whose optical axes are opposite to each other and are in contact with and integrated at a boundary surface obliquely intersecting the guided light. a plurality of electro-optic crystals, a pair of electrodes that generate an electric field parallel to the optical axis within these electro-optic crystals, and a power supply means that selectively applies a voltage to the pair of electrodes. switch. 2. An optical waveguide made of an electro-optic material formed on a substrate with the optical axis orthogonal to the substrate surface, and an optical waveguide that is insulated from each other by having boundary surfaces located on both sides of the optical waveguide and obliquely intersecting the guided light. A plurality of electrode pairs that generate an electric field parallel to the optical axis within the optical waveguide, each consisting of at least two input electrode pairs, a center electrode pair for optical path conversion, and two output electrode pairs, and at least an input electrode to these electrode pairs. 1. An optical switch comprising power supply means for selectively applying voltages in opposite directions to a pair of central electrodes, a pair of output electrodes, and a pair of central electrodes for optical path conversion.