JPS61208037A - Optical switch - Google Patents

Abstract

PURPOSE:To improve the strength against oscillation, etc. and switching speed by providing magnetooptic materials to part between three pieces of crystal bodies of which the thicknesses have a specific ratio and which are arrayed in one row and impressing magnetically invertable external magnetism to such optical system. CONSTITUTION:Three double refractive bodies of which the thicknesses have 1:2:1 ratio are arrayed in one row. Incident light is first separated to two rays by the 1st double refractive crystal body 3. The rays are subjected to the rotation in the 45 deg. polarization direction by the magnetooptic material 6 and to the 45 deg. rotation by a half wave plate 8 if necessary. The optical paths of the two rays are adjusted by the 2nd double refractive crystal body 4 and thereafter the rays are again subjected to the rotation by the magnetooptic material 7 and a half wave plate 9 if necessary. The two rays are joined to each other by the 3rd double refractive crystal body 5 and are emitted therefrom. The Faraday rotation by the materials 6, 7 is controlled by the impressing direction of the external magnetic field during this time to control the optical path of the incident light, by which the optical switch is formed. The optical switch obtd. in such a manner has no movable parts, has the high strength against oscillation and can increase the switching speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical switch that switches the optical path of an optical fiber or the like.

(Prior Art) In recent years, optical fiber technology has improved, and optical communication systems using optical fibers have become significantly layered. In such optical communication devices, a means for switching the optical path through which light passes is necessary for the device to function efficiently, and a high-performance optical switch is essential. However, in the past, optical switches have mainly been made by driving electromagnets to change the optical system, such as by rotating a mirror or moving a prism.

Optical switches with these movable parts have a clear operating principle and are highly efficient; however, they are weak against strong external vibrations and require the optical system to be moved. There is a limit to operating speed, and high-speed switching is difficult to expect.

FIGS. 3 and 4 show the structure of one conventional mechanical type optical switch.

In FIG. 3, the light passing through the input optical fibers 31 and 31' is condensed by the microlens 32 and enters the movable prism 33, and the movement of the movable prism 33 changes the optical system, so that the output light changes. The light path changes.

In FIG. 4, the light passing through the input optical fiber 41 is condensed by the microlens 42 and reflected by the reflecting mirror 43, and the output light passes through the microlens 44 and the output optical fiber 45. The light is changed in the optical system by the rotation of the reflecting mirror 43.

(Problems to be Solved by the Invention) However, with the above configuration, since the optical switch cannot be performed without moving a fairly heavy prism, there are problems such as the switching time is slow and the strength against vibration is weak. Was.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a solid-state optical switch that has no moving parts, has high resistance to vibrations, etc., and has high switching speed.

(Means for Solving the Problems) In order to solve the above problems, the optical switch of the present invention has three birefringent crystals having a thickness ratio of 1=2:1 arranged in a row. A magneto-optical material is placed in a part between the three crystal bodies, and an external magnetic field capable of magnetic reversal is applied to the thus obtained optical system to switch the light incident on the optical system from an optical fiber or the like. It is equipped with a configuration in which it emits light.

(Function) With the above-described configuration, the present invention first separates incident light into two light beams using the first birefringent crystal.

45 by magneto-optical material as necessary for each ray.
After applying the rotation of the polarization direction by 45° and the 45° rotation by the half-wave plate, and adjusting the optical path of the two rays by the second birefringent crystal, again if necessary, the magneto-optic material and the half-wave plate are used. The third birefringent crystal unit merges the two light beams and emits them. During this time, the Faraday rotation of the magneto-optical material is controlled by the direction of application of the external magnetic field, and the optical path of the emitted light is selected by controlling the optical path of the incident light, thereby forming an optical switch.

The optical switch obtained in this way has no moving parts and can be called a solid-state element.

(Example) A first example of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is an explanatory diagram of an optical switch showing a first embodiment of the present invention. Figure 1 (aL (b) shows two types of light path states obtained by the operation of the switch. In the figure, 1 is the input optical fiber, 2 is the microlens, and 3 is the first optical fiber. , 4 indicates the second birefringent crystal, and 5 indicates the third birefringent crystal.The directions of the optical axes of the respective birefringent crystals are indicated by 3', 4', and 5'. Note that crystals 3 and 5 have the same thickness in the direction of light propagation, but crystal 4 has twice the thickness of crystals 3 and 5.Next, 6 is the first 7 is a second magneto-optical material having Faraday characteristics, 8 is a first half-wave plate, and 9 is a second half-wave plate.

Reference numerals 10 and 11 indicate the microlens and optical fiber of one of the two emitting sections, and 12 and 13 indicate the microlens and optical fiber of the other. On the other hand, an external magnetic field is applied to the magneto-optical material 6°7, but the direction of the magnetic field is, for example, 14°.
．． This is indicated by an arrow as shown in 15.

The external magnetic fields of direction 14 , 15 of these fields are oriented in the same direction, but they are formed by core 16 and coil 17 and core 18 and coil 19 . Note that these two cores 16 and 18 are made of semi-hard ferromagnetic material,
Although it is magnetized by the current flowing through the coil 17.19, the direction 14.15 of the magnetic field is maintained due to residual magnetization even after the current is turned off. To reverse the direction of the magnetic field, a current is passed in the opposite direction.

Note that the optical axis of the half-wave plate is selected and set in a direction so as to tilt the linearly polarized light by 45 degrees. The magneto-optic material 6°7 is configured to rotate the linearly polarized light by +45° or -45'' depending on the direction of the magnetic field.

The operation of the optical switch configured as described above will be explained.

First, in FIG. 1(a), the directions 14 and 15 of the magnetic field are applied from left to right, that is, in the direction in which the light travels. In FIG. 1(b), the light is applied in the direction opposite to the direction in which the light travels. First, in FIG. 1(a), light that enters as diverging light from an optical fiber 1 is turned into parallel light by a collimator microlens 2, and then enters a birefringent crystal 3. When the optical axis of a birefringent crystal 3 (for example, a crystal such as calcite) is in a direction such as 3', the incident light beam is split into two light beams 20 and 21 as shown. Within the birefringent crystal 3, the light ray 20 is normal light and the light ray 21 is extraordinary light. The light ray 20 that has passed through the birefringent crystal 3 then enters the birefringent crystal 4 . However, the light ray 21 that has passed through the crystal body 3 passes through the magneto-optic material 6 and the half-wave plate 8, and the linear polarization direction is rotated by 45 degrees and 45 degrees, that is, by 90 degrees, and the light beam 21 passes through the second birefringent crystal as normal light. enters the body 4. The light ray 21 exiting the birefringent crystal 4 does not pass through the magneto-optic material 7 and the half-wave plate 9, but enters the third birefringent crystal 5.
The light is focused by a microlens 10 and enters an optical fiber 11. Also, the light ray 2 emitted from the second birefringent crystal body 4
0 rotates the polarization direction by 45 degrees with the magneto-optical material 7, tilts it further by 45 degrees with the next half-wave plate 9, enters the third birefringent crystal 5 as extraordinary light, enters the microlens 10, and becomes light. It enters the fiber 11.

Next, in FIG. 1(b), if the direction 14.15 of the external magnetic field is reversed to the opposite direction from FIG. 1(a), the optical fiber 1
The light ray that enters the birefringent crystal 3 through the microlens 2 is split into two rays 22 and 23, and after the ray 22 passes through both the birefringent crystals 3 and 4 as normal light,
The polarization direction is rotated by 145 degrees using the magneto-optical material 7, tilted by +45 degrees using the next half-wave plate 9, and then enters the third birefringent crystal 5 as normal light, passes through the microlens 12, and enters the optical fiber 13. incident.

After the light ray 23 leaves the birefringent crystal 3, it passes through the magneto-optic material 6.
Rotate the linear polarization direction by 145 degrees, and use half-wave plate 8 to rotate the linear polarization direction by
After being tilted by 0° and rotated by a total of 0°, it enters the second birefringent crystal 4 as extraordinary light, passes through this, the polarization direction is rotated by -45° by the magneto-optic material 7, and the half-wave plate 9 De＋
It is tilted by 45° and rotated by a total of 0°, enters the third birefringent crystal 5, passes through the microlens 12, and enters the optical fiber 13.
incident on the

As explained above using FIGS. 1(a) and 1(b).

When a magnetic field is applied as shown in Figure 1 (,).

The light beam emitted from the optical fiber is ray 20.21-2.
When a magnetic field is applied in the opposite direction to that shown in FIG. 1(a), as shown in FIG. emit to.

Specifically, in configuring the optical circuit shown in FIG. 1, the first and third birefringent crystals 3 and 5 are 10 mm
10mm x 10mm calcite as the second birefringent crystal 4 10+m+ x 10nn x 20
A++ calcite was used. Further, as the magneto-optical materials 6 and 7, YIG (yttrium, iron, garnet) is used.
The half-wave plates 8 and 9 are made of mica, and the optical fiber 1 is made of mica.
, 11.13 is a multimode fiber with a core diameter of 150 μm, and the microlens 10.12 is a multimode fiber with a diameter of 1.
A 0-kaku rod lens was used. The external magnetic field was generated by a semi-rigid core and coil, and was driven at 2000e<. Infrared light with a wavelength λ=1.3 μm was used as a light source, and calcite coated with an antireflection film was used. 2 due to reversal of external magnetic field
The ratio of optical outputs emitted from two optical fibers is approximately 20 dB
Met. Further, the insertion loss was about 3 dB.

As described above, according to this embodiment, three birefringent crystals arranged in a line with a thickness ratio of 1:2:1 and a magneto-optical material placed in a part of the space between them are used. The optical system formed by the half-wave plate can be said to have the function of switching the light incident on the optical system into two optical paths and outputting the light by reversing the magnetic field applied to the magneto-optic material.

FIG. 2 is an explanatory diagram of an optical switch showing a second embodiment of the present invention. FIGS. 2(a) and 2(b) show two states of the light path obtained by the operation of the switch. In both FIGS. 2(a) and (b), 1 is the optical fiber on the incident side, 2 is the microlens, 3 is the first, 4 is the second, and 5 is the third. The second birefringent crystal is shown. Furthermore, the directions of the optical axes of the respective birefringent crystals are expressed as 3', 4', and 5'. Note that although the crystal bodies 3 and 5 have the same thickness in the direction of propagation of light, the crystal body 4 has twice the thickness of the crystal bodies 3 and 5. Next, 6 is the first magneto-optical material, 7 is the second Faraday characteristic, 8 is the first, and 9, 9' are the second Faraday characteristics.
This is the second half-wave plate. However, the second half-wave plate consists of two parts 9 and 9' having different optical axes. 10
and 11 indicate the microlens and optical fiber of one of the two output sections, and 12 and 13 indicate the microlens and optical fiber of the other. On the other hand, an external magnetic field is applied to the magneto-optical materials 6 and 7, and the direction of the magnetic field is set to 14.1, for example.
This is indicated by an arrow as shown in 5. Direction of magnetic field 14.1
The external magnetic fields of 5 are oriented in the same direction, but they are formed by core 16 and coil 17 and core 18 and coil 19. Note that these two cores 16.18 are made of semi-hard ferromagnetic material, and are magnetized by the current flowing through the coil 17.19, but even after the current is turned off, the direction of the magnetic field 14.15 is maintained due to residual magnetization. dripping To reverse the direction of the magnetic field, a current is passed in the opposite direction.

Note that the optical axis of the half-wave plate is selected and set in a direction so as to tilt the linearly polarized light by 45 degrees. The magneto-optic material is configured to rotate linearly polarized light by +45 or -45 depending on the direction of the magnetic field.

The operation of the optical switch configured as described above will be explained.

First, in Fig. 2(a), the direction of the external magnetic field is 14°1.
5 is applied from left to right on the plane of the paper, that is, in the direction in which the light travels. In FIG. 2(b), the light is applied in the direction opposite to the direction in which the light travels. Introduction.

In FIG. 2(a), light incident as diverging light from the optical fiber 1 is turned into parallel light by the collimator microlens 2, and then is directed to a birefringent crystal. A birefringent crystal 3 (for example, a crystal such as calcite) whose optical axis is 3'
In the case of the direction, the incident ray is split into two rays 20 and 21 as shown.

Within the birefringent crystal 3, the light ray 20 is normal light and the light ray 21 is extraordinary light. The light ray 20 that has passed through the birefringent crystal 3 enters the second birefringent crystal 4 without passing through the magneto-optic material 6 or the half-wave plate 8. However, the ray 2 that passed through the crystal 3
1 passes through the magneto-optical material 6 and the half-wave plate 8 and enters the second birefringent crystal 4 with the linear polarization direction rotated by 45 degrees and 45 degrees, that is, by 90 degrees. The light ray 20 exiting the birefringent crystal 4 has its polarization direction rotated by 45° in the magneto-optic material 7, and then tilted by -45° in the next half-wave plate 9' and rotated by a total of 0° to form the third compound. The light enters the refractive crystal 5, is focused by the microlens 10, and enters the optical fiber 11. In addition, the polarization direction of the light ray 21 emitted from the second birefringent crystal 4 is rotated by 45 degrees by the magneto-optic material 7, and further tilted by 45 degrees by the next half-wave plate 9, and is converted into the third compound as extraordinary light. The light enters the refractive crystal body 5, enters the microlens 10, and enters the optical fiber 11.

Next, in FIG. 2(b), if the direction 14.15 of the external magnetic field is reversed to the direction opposite to that in FIG. 2(a), the optical fiber 1
The light ray that has passed through the microlens 2 and entered the birefringent crystal 3 is split into two rays 22 and 23, and after the ray 22 passes through both the birefringent crystals 3 and 4 as normal light,
The polarization direction is rotated by 145° using the magneto-optical material 7, further tilted by -45° using the 5th-order half-wave plate 9, and enters the third birefringent crystal 5 as extraordinary light, which passes through the microlens 12 and enters the optical fiber. 13. After the light ray 23 exits the birefringent crystal 3, the linear polarization direction is rotated by 145 degrees by the magneto-optic material 6, tilted by +45 degrees by the half-wave plate 8, and rotated by a total of 0 degrees, and is converted into a second beam as extraordinary light. After passing through the second birefringent crystal body 4, the polarization direction is -45'' at the magneto-optical material 7.
The light is rotated, further tilted by -45° by the half-wave plate 9, enters the third birefringent crystal 5, passes through the microlens 12, and enters the optical fiber 13.

As explained above using FIGS. 2(a) and (b), when a magnetic field is applied as shown in FIG. 2(a),
The light beam entering from the optical fiber 1 is divided into two light beams 20 and 21, but ultimately exits to the optical fiber 11,
As shown in FIG. 2(b), when a magnetic field is applied in the opposite direction to that in FIG.
emit to. Its characteristics are similar to the first embodiment.

As described above, according to this embodiment, three birefringent crystals arranged in a line with a thickness ratio of 1=2=1 and a magneto-optic material arranged in a part of the space between them are used. The optical system formed by the half-wave plate has a function of reversing the magnetic field applied to the magneto-optic material, so that the light incident on the optical system can be divided into two optical paths with little loss and no moving parts. It can be switched and emitted.

(Effects of the Invention) The optical switch according to the present invention includes three birefringent crystals arranged in a row with a thickness ratio of 1:2:1, a magneto-optic material arranged in the space between them, and a half-wavelength The optical system formed by the plate has a function of reversing the magnetic field applied to the magneto-optic material, so that the light incident on the optical system can be controlled with little loss and without the need for moving parts.
It is possible to switch between two optical paths and emit light.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an optical switch in a first embodiment of the present invention, FIG. 2 is an explanatory diagram of an optical switch in a second embodiment of the present invention, and FIGS. 3 and 4 are conventional optical switches. FIG. 1, 31, 31', 41... optical fiber for incidence,
2゜10, 12, 32.44...Micro lens,
3,4.5...Birefringent crystal, 3', 4', 5''
... Optical axis direction of birefringent crystal, 6,7 ... Magneto-optical material, 8.9.9' ... Half-wave plate, 11.1
3... Optical fiber for output, 14.15... Direction of magnetic field + 16.18... Semi-rigid core, 17.19...
・Coil, 20, 21° 22.23...Light beam, 2
4.33...Movable prism, 25.43...Reflector.

Claims (2)

[Claims] (1) An optical system is formed by arranging a magneto-optical material and a half-wave plate in a part of the space between three birefringent crystals arranged in a row with a thickness ratio of 1:2:1, An optical switch characterized in that the light incident on the optical system is switched and emitted by reversing the magnetic field applied to the magneto-optical material. (2) The optical switch according to claim (1), wherein the reversible magnetic field applied to the magneto-optical material is generated by a coil and a semi-hard magnetic material.