JPH09189925A - Method for switching light radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remotely controllable optical switch which can switch light radiation without using any movable part and outputs light through various ports. SOLUTION: For the method for switching light radiation, the optical switch 10 is used, and polar optical radiation passes through a magnetooptic material 20 in this optical switch 10. A magnetic field applicator 16 applies a magnetic field to the magnetooptic material 20 in the direction wherein the rotation of the optical radiation passing through the magnetooptic material 20 is switched. A polar walk-off element receives the optical radiation from the magnetooptic material 20 and the position of the optical radiation from this walk-off element depends upon the direction of the magnetic field.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical switch for switching light emission without the use of mechanically moving parts.

[0002]

2. Description of the Related Art Some optical switches use mechanically movable parts, which force the optical fiber to a plurality of different positions to act as switches. This type of switch can be manufactured inexpensively and is easily accepted if the switch can be easily maintained or replaced. Another type of switch is based on lateral movement of the optical fiber (similar to switching train lines), or by a quarter plate half.
Utilizing the rotation of the plate and the polar device. Switches of this kind have the disadvantages of slow switching speed, mechanical wear, high power consumption and immobility after long periods of inactivity.

In the undersea optical fiber communication system,
All-optical switches with no mechanical moving parts are desirable.
Such switches must be remotely controllable and require high reliability. The reason is that it is difficult to maintain and repair switches on submarine cables. Attempts have been made to use electro-optical polar controllers, polar rotators using the Faraday effect, garnet waveguides and other similar devices as optical switches. A simple Faraday rotator using a thin plate-shaped garnet such as yttrium-iron-garnet has been designed and used as an optical isolator. This type of optical isolator functions as a one-way filter using the unidirectional characteristic of a Faraday rotator fixed by a rare earth permanent magnet. Also, there is no device that switches or obtains the required polarity during operation.

[0004]

SUMMARY OF THE INVENTION It is an object of the invention to provide an optical switch whose light emission can be switched without moving parts and which can be controlled remotely through various ports. In particular, such an optical switch is advantageous in undersea applications where it is difficult to maintain.

[0005]

According to the invention, a method of switching optical radiation uses the optical switch of the invention, in which polar optical radiation passes through a magneto-optical material. The magnetic field applicator applies a magnetic field to the magneto-optical material in a direction that switches the rotation of optical radiation through the magneto-optical material. A polar walk-off element receives optical radiation from a magneto-optical material, and the position of the optical radiation emanating from this walk-off element depends on the direction of the magnetic field.

According to one aspect of the invention, the magneto-optical material comprises garnet. Magnetic field applicator (magnetic field applying device)
Applies a magnetic pulse.

According to another aspect of the invention, an optical circulator has ports for optical radiation to enter and exit. The magnetic field applicator applies a magnetic field to the optical circulator and switches the direction of optical radiation passing through the optical circulator. The optical circulator of the present invention is a 4-port circulator and is made of magneto-optical material.

[0008]

1 and 2, an optical switch 10 comprises a four-port optical circulator 12 having a port 14 through which light radiation enters and exits. A magnetic field applicator 16 applies a magnetic field to the 4-port optical circulator 12 to switch the direction of light emission passing through the 4-port optical circulator 12. This 4-port optical circulator 1
2 consists of a magneto-optical material 20, usually garnet. The magnetic field applicator 16 has a pulse generator 22 which applies magnetic field pulses to the magneto-optical material 20 resulting in 4
The direction of light radiation passing through the port optical circulator 12 is reversed as shown in FIG.

FIG. 3 illustrates another optical switch that uses the walk-off device 30 to receive optical radiation from the Faraday rotator 32. At this time, walk-off device 3
The position of the optical radiation, which originates from 0, depends on the direction of the magnetic field.
The walk-off device 30 is made of a birefringent crystal material. The half-aperture-half-wave plate 34 switches the polarity of the light beam passing therethrough, but does not change the polarity of the light beam passing beside it. As shown, the switching magnet device 40 reverses the magnetic field. The switching magnet device 40 is composed of a magnetizing coil.
The letter M with an arrow indicates the direction of the magnetic field.

As shown in FIG. 1, the optical switch 1 of the present invention.
Zero has no moving parts and can be controlled remotely, which can be used in submarine fiber optic communication systems. This optical switch 10 has 180 degrees of orthogonal magnetization indicated by −M →, ← M− in the Faraday rotator 32 made by Garnet.
Switch in the direction of degrees. The Faraday rotator 32 has a high Faraday effect, eg in Bi-doped rare earth garnets, and sufficient remnant magnetic field in the switching magnet arrangement 40 is required to maintain polar rotation after each switching event. For the Faraday rotator 32,
Both the switching magnetic field and the residual magnetic field are provided by the single highly saturated, high residual, rectangular BH loop semi-hard magnetic field material of the switching magnet device 40. The magnetic field from the solenoid 42 is amplified due to the high saturation magnetization of the switching magnet device 40.

The switching magnet device 40 of the optical switch 10 of the present invention has a hollow thin wall cylinder shape, and the outer shape is 0.122 inch (3.0988 mm).
The inner shape is 0.082 inch (2.0828 mm) and the length is 0.32 inch (8.128 mm). When the 1.55 μm input light beam passes through the birefringent material, the birefringent material separates the light beam into two orthogonal polar states. One beam is half aperture-half wave plate 3
Rotate 90 degrees by 4. The two beams have the same polarity state and pass through the inside of the switching magnet device 40 to the Faraday rotator 32 made of garnet. The Faraday rotator 32 made of garnet has a pulse polarity state or a polarity state (-) of a magnetic field applied thereto.
Rotate -45 degrees depending on (as indicated by either M → or ← M−). Both beams then pass through a second birefringent material, which is the walk-off device 30. Comparing FIGS. 3A and C, changing the −M− direction changes the polarity of the beam, thereby forming a pair of different paths within the walk-off device 30.
The half-aperture-half-wave plate 34 flips the polarity when the polarity is ← M- (FIG. 3C), and does not flip the polarity otherwise (FIG. 3A).

At this point, the polarities of all beams in all possible paths are the same. The next half-aperture-half wave plate 26 flips one polarity of the pair of beams,
As a result, they are walked by the walk-off device 24 and output from either of the two output fibers.

While high coercivity magnetic materials typically produce high magnetic flux values in practical magnet applications, the presence of self-non-magnetic air gap features is unavoidable. This high coercivity is not always desirable in the design of the optical switch of the present invention because it provides only a limited magnetic field. The design rule for the magnetizing field (H _a ) for _a permanent magnet is H _a ≧ about 2.5 × H _c . Operation in low magnetic fields is undesirable
op) situation, resulting in a low magnetic moment and sometimes non-reproducible switching action.

The direction of light emission is reversible, in which case the light emission enters from one of the two ports (right side of FIG. 3),
Exit from one port (left side).

[0015]

As described above, since the optical switch of the present invention can be remotely controlled, it has an advantage in an application under the sea where it is difficult to maintain and manage the optical switch.

[Brief description of the drawings]

1A is a diagram showing a state in which light emission of the present invention is not switchable. B is a diagram showing an optical circulator as an optical switch of the present invention.

2A is a diagram showing a state where the light emission of the present invention is switched. FIG. 2B is a diagram showing an optical circulator as an optical switch of the present invention.

3A to 3D are diagrams showing a Faraday rotator optical switch according to the present invention.

[Explanation of symbols]

 1, 2 Input light radiation 1 ', 2'Output light radiation 10 Optical switch 12 4 port optical circulator 14 port 16 Magnetic field applicator (magnetic field applying device) 20 Magneto-optical material 22 Pulse generator 24 Walk-off device 26, 28, 34 Half-aperture-half-wave plate 30 Walk-off device 32 Faraday rotator 40 Switching magnet device 42 Solenoid 34 H Half-wave plate H / 2 Half-aperture-half-wave plate F Faraday rotator M Magnetic field direction

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 596077259 600 Mountain Avenue, Murray Hill, New Jersey 07974-0636 U.S.A. S. A. (72) Inventor Richard Heinrich Nehru USA, 18069 Pennsylvania, Olefield, Werba Drive 1330

Claims (11)

[Claims] 1. A) passing polar light radiation (1, 2) through a magneto-optical material (20); and (B) switching the direction of polarity of light radiation passing through the magneto-optical material (20). (16, 42) applying a magnetic field to the magneto-optical material for the purpose of: (C) directing the optical radiation into a polar walk-off device (3).
0) A method for switching light emission, comprising the step of passing through 0), wherein the position of the light emission exiting the walk-off device (30) depends on the direction of the magnetic field. 2. The method of claim 1, wherein said step (B) applies a magnetic field to the garnet material in the Faraday rotator (F, 32). 3. The step (B) comprises applying a magnetic field with magnetic pulses (22).
the method of. 4. A step of: (A) inputting light radiation (1, 2) into a port of an optical circulator (12) and outputting light radiation (1 ′, 2 ′) from another port; (B) A method of switching optical radiation, comprising the step of (16,22) applying a magnetic field to the optical circulator to switch the direction of optical radiation passing through the optical circulator (12). 5. The method of claim 4, wherein step (B) applies a magnetic field to the magneto-optical material in the Faraday rotator. 6. The method according to claim 5, wherein the step (B) applies a magnetic field by a magnetic pulse. 7. A magnetic field applicator (16, 40) for applying a magnetic field to the magneto-optical material in a direction that switches between (A) a magneto-optical material (20) and (B) rotation of light radiation passing through the magneto-optical material. And (C) a polar walk-off device (30) for receiving light radiation from the magneto-optical material, wherein the position of the light radiation exiting the polar walk-off device depends on the direction of the magnetic field. Characteristic optical switch. 8. The optical switch according to claim 7, wherein the magneto-optical material includes garnet. 9. The optical switch according to claim 8, wherein the magnetic field applicator applies a magnetic pulse. 10. An optical circulator (12) having (A) a port for inputting and outputting optical radiation, and (B) a magnetic field applicator for applying a magnetic field to the optical circulator to switch the position of the optical radiation passing through the optical circulator. (16) An optical switch comprising: 11. The optical switch according to claim 10, wherein the optical circulator is any one of a 4-port circulator, a 3-port circulator, and a circulator having 5 or more ports.