JPH06324288A - Polarization independent type optical isolator - Google Patents

Abstract

PURPOSE:To lessen the deterioration of the isolation of the polarization independent type optical isolator and to increase the degrees of freedom in design. CONSTITUTION:This polarization independent type optical isolator consists of three or four pieces of double refractive wedge plates 31 to 33 and one or two pieces of 45 deg. Faraday rotor 35 and is arranged with these plates and rotor by selecting the wedge angle, optical axis bearings and inclination bearings of the double refractive wedge plates 31 to 33 and the magnetic field direction of the 45 Faraday rotor 35 that the sum of the vectors of all the double refractive wedge plates 31 to 33 turns zero with two beams of the polarized light orthogonal with a forward direction and that the sum of the vectors of all the double refractive wedge plates 31 to 33 do not turn zero with two beams of the polarized light in the reverse direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization independent optical isolator.

[0002]

2. Description of the Related Art FIG. 6 is a diagram of a conventional example, (A) is a forward optical path diagram, (B) is a reverse optical path diagram, and FIG. 7 is a configuration diagram of another conventional example.

In the figure, in the polarization independent optical isolator, the optical axis azimuth P coincides with the tilt azimuth, and the first birefringent wedge plate 11 whose tilt azimuth is downward and the optical axis azimuth P are aligned with the tilt azimuth. Second birefringent wedge plate with tilt direction upward
12 and a 45-degree Faraday rotator 15 interposed between the first birefringent wedge plate 11 and the second birefringent wedge plate 12.

The optical axis direction P of each birefringent wedge plate is installed so as to be perpendicular to the optical axis, and
The optical axis direction P of the birefringent wedge plate 11 and the optical axis direction P of the second birefringent wedge plate 12 are inclined by 45 degrees.

Reference numeral 3 denotes a lens for making the light emitted from the output side optical fiber 1 enter the optical isolator as parallel light rays, and 4 denotes
It is a lens that collects the light emitted from the optical isolator on the input side optical fiber 2.

As shown in FIG. 6A, the light in the forward direction emitted from the output side optical fiber 1 becomes parallel rays by the lens 3 and reaches the first birefringent wedge plate 11 to reach the first birefringent wedge plate 11. The birefringent wedge plate 11 separates the polarized light into two polarized lights having orthogonal polarization planes, refracts in different directions and travels to reach the 45 ° Faraday rotator 15.

Then, the plane of polarization of each polarized light is rotated by 45 degrees by the 45 degree Faraday rotator 15 and reaches the second birefringent wedge plate 12. At this time, one polarized light is incident on the second birefringent wedge plate 12 as ordinary light (shown by a solid line), and the other polarized light is incident on the second birefringent wedge plate 12 as extraordinary light (shown by a dotted line).

As described above, the optical axis azimuth P of the first birefringent wedge plate 11 and the optical axis azimuth P of the second birefringent wedge plate 12 are inclined by 45 degrees, so that they are separated from each other. The polarized light becomes parallel light, reaches the lens 4, and is condensed on the incident end surface of the input side optical fiber 2 by the lens 4,
To proceed.

On the other hand, the light reflected back from the input side optical fiber 2 is the second birefringent wedge plate as shown in FIG. 6 (B).
The polarization plane is separated into two polarizations orthogonal to each other by 12 and refracted in different directions to proceed to the 45 degree Faraday rotator 15.

And by the 45 degree Faraday rotator 15,
The polarization plane of each polarization is opposite to the direction of the forward direction.
It rotates 45 degrees and reaches the first birefringent wedge plate 11. At this time, the relationship between the ordinary light and the extraordinary light is reversed. That is, the ordinary light is extraordinary light and the extraordinary light is ordinary light.
Since it is incident on 11, the two polarized lights are not parallel, and even if they are condensed by the lens 3, they are not condensed on the exit end face of the core of the output side optical fiber 1.

That is, the return light from the input side optical fiber 2 does not enter the output side optical fiber 1. The conventional example shown in FIG.
This is a polarization-independent optical isolator disclosed in JP-A-60-130934.

In FIG. 7, in the polarization independent optical isolator, the optical axis azimuth P coincides with the tilt azimuth and the tilt azimuth is downward, and the optical axis azimuth P is the tilt azimuth. A second birefringent wedge plate 22 having a matching and upward tilt direction and a first 45-degree Faraday rotator 25 interposed between the first birefringent wedge plate 21 and the second birefringent wedge plate 22.
And the optical axis azimuth P is inclined 45 degrees to the tilt azimuth, the tilt azimuth is leftward, and the third birefringent wedge plate 23 disposed behind the second birefringent wedge plate 22 and the optical axis azimuth P are The fourth birefringent wedge plate 24 that matches the tilt direction and is tilted to the right 24
23rd third birefringent wedge plate and fourth birefringent wedge plate
And a second 45 degree Faraday rotator 26 interposed between 24.

That is, the conventional example shown in FIG. 7 is a combination of a first-stage optical isolator and a second-stage optical isolator. The optical axis direction P of the first birefringent wedge plate 21 and the optical axis direction P of the second birefringent wedge plate 22 are 45.
The optical axis direction P of the second birefringent wedge plate 22 and the optical axis direction P of the third birefringent wedge plate 23 are the same.
The optical axis direction P of the third birefringent wedge plate 23 and the optical axis direction P of the fourth birefringent wedge plate 24 are inclined by 45 degrees.

The magnetic field direction of the first 45-degree Faraday rotator 25 and the magnetic field direction of the second 45-degree Faraday rotator 26 are opposite directions. As described above, the polarization-independent optical isolator in which the first-stage optical isolator and the second-stage optical isolator are combined is used when the forward light passes through the first-stage optical isolator. The light is separated into polarized light, and each polarized light is further separated into two polarized light by the second-stage optical isolator, and becomes parallel light of four polarized light, which is condensed by the lens 4 and travels through the input side optical fiber 2.

Further, since the light in the opposite direction passes through the second-stage optical isolator and the first-stage optical isolator, the deterioration of isolation due to incompleteness of the 45 degree Faraday rotator or the like becomes extremely small. There is an advantage.

[0016]

However, in the conventional optical isolator, the wedge angles of all the birefringent wedge plates are equal, the optical axis azimuth P and the tilt azimuth are parallel or 45 degrees, and the arrayed birefringent wedges are used. Whether the tilt direction of the board is parallel,
They are orthogonal.

That is, the conventional optical isolator has a problem that the degree of freedom in design is limited. The present invention has been made in view of the above circumstances, and an object thereof is to provide a polarization-independent optical isolator with less isolation deterioration and greater design freedom.

[0018]

In order to achieve the above object, the present invention comprises three or four birefringent wedge plates and one or two 45 degree Faraday rotators, and the birefringent wedge plates. When the tilt azimuth of is defined as the vector direction and (wedge angle × refractive index) is defined as the absolute value of the vector, the sum of the vectors of all birefringent wedge plates is So that the sum of the vectors of all birefringent wedge plates does not become zero for two orthogonal polarizations in opposite directions, the wedge angle of the birefringent wedge plate, the optical axis direction, the tilt direction, and The magnetic field direction of the 45-degree Faraday rotator is selected and arranged.

When it comprises three birefringent wedge plates and one 45-degree Faraday rotator, as shown in FIG.
First birefringent wedge plate 31 with wedge angle α, wedge angle α
Second birefringent wedge plate 32, 45 degree Faraday rotator 35,
And a third birefringent wedge plate 33 having a wedge angle of 2 ^1/2 α are arranged in this order, and the first birefringent wedge plate 31 and the second birefringent wedge plate 32 are relatively arranged with respect to the optical axis. The second birefringent wedge plate 32 and the third birefringent wedge plate 33 are installed at an angle rotated by 45 degrees relative to the optical axis at an angle rotated by 90 degrees.

The optical axes azimuth P of the first birefringent wedge plate 31 and the second birefringent wedge plate 32 are parallel to each other, and the second birefringent wedge plate 32 and the third birefringent wedge plate 33 are The optical axis azimuth P is inclined by 45 degrees.

In the case of comprising three birefringent wedge plates and two 45 ° Faraday rotators, as shown in FIG.
A first birefringent wedge plate 41 with a wedge angle α, a first 45 ° Faraday rotator 45, a second birefringent wedge plate 42 with a wedge angle α, a second 45 ° Faraday rotator 46, and a wedge angle α. The third birefringent wedge plate 43 of is arranged in this order, and the respective first, second and third birefringent wedge plates 41, 42, 43 are
It is installed at an angle of 120 degrees relative to the optical axis.

The optical axis direction P of the first birefringent wedge plate 41 and the second birefringent wedge plate 42 is inclined by 45 degrees, and
The birefringent wedge plate 42 and the third birefringent wedge plate 43 are structured such that the optical axis direction P is inclined by 45 degrees.

In the case of four birefringent wedge plates and two 45-degree Faraday rotators, as shown in FIG.
A first birefringent wedge plate 51 with a wedge angle α, a first 45 ° Faraday rotator 55, a second birefringent wedge plate 52 with a wedge angle α, a third birefringent wedge plate 53 with a wedge angle α, a third 2's
A 45-degree Faraday rotator 56 and a fourth birefringent wedge plate 54 having a wedge angle α are arranged in this order, and the first, second, third, and fourth birefringent wedge plates 51, 52, 53, 54 are arranged. Is installed at an angle rotated by 90 degrees relative to the optical axis.

The optical axis direction P of the first birefringent wedge plate 51 and the second birefringent wedge plate 52 is inclined by 45 degrees, and
The birefringent wedge plate 53 and the fourth birefringent wedge plate 54 are structured such that the optical axis direction P is inclined by 45 degrees.

[0025]

The present invention has three or four birefringent wedge plates and one
If two or more 45 degree Faraday rotators are used and the tilt direction of the birefringent wedge plate is defined as the vector direction and (wedge angle × refractive index) is defined as the absolute value of the vector, all birefringent wedge plates Make sure that the vector sum is zero for two polarizations in which the planes of polarization in the forward direction are orthogonal, and that the vector sum of all birefringent wedge plates is not zero for two polarizations in the opposite direction and orthogonal. Are arranged in.

An arrangement in which the sum of the vectors of all the birefringent wedge plates does not become zero for two polarized lights whose polarization planes in opposite directions are orthogonal to each other means that the optical axes of the respective birefringent wedge plates. The azimuth P is almost perpendicular to the optical axis, the optic axis azimuths P of the adjacent birefringent wedge plates are parallel, and
In the case of a birefringent wedge plate with a 45 ° Faraday rotator interposed, the optical axis azimuth P forms an angle of 45 °.

Because of the above-mentioned structure, the light in the forward direction that has entered the birefringent wedge plate at the frontmost stage (first birefringent wedge plate) passes through the birefringent wedge plate at the final stage, and is incident on the incident light. Parallel light.

Therefore, by using the condenser lens, it is incident on the input side optical transmission line and travels along the input side optical transmission line. On the other hand, the light in the opposite direction incident on the last stage birefringent wedge plate is
When the light passes through the birefringent wedge plate of the first stage (first birefringent wedge plate), it becomes light that is not parallel to the incident light. Therefore, it does not enter the output side optical transmission line.

The above configuration can be achieved by selecting and combining the wedge angle of the birefringent wedge plate, the optical axis direction and the magnetic field direction of the 45 ° Faraday rotator.
Greater flexibility in design.

[0030]

The present invention will be described in detail with reference to the drawings. The same reference numerals denote the same objects throughout the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an optical path diagram of an embodiment of the present invention, (A) is a forward optical path diagram, and (B) is an optical path diagram.
Is a reverse optical path diagram, FIG. 3 is a configuration diagram of another embodiment of the present invention, FIG. 4 is a configuration diagram of yet another embodiment of the present invention, and FIG. 5 is an optical path diagram of yet another embodiment of the present invention. Is.

In FIG. 1, the polarization independent optical isolator comprises a first birefringent wedge plate 31 having a wedge angle α, a second birefringent wedge plate 32 having a wedge angle α, and a 45 ° Faraday rotator 35. And a third birefringent wedge plate 33 having a wedge angle of 2 ^1/2 α are arranged in this order.

The first birefringent wedge plate 31 has an optical axis direction P
Is orthogonal to the tilt direction, and the tilt direction is to the right. In the second birefringent wedge plate 32, the optical axis direction P is parallel to the tilt direction, and the tilt direction is upward.

The magnetic field direction H of the 45 ° Faraday rotator 35 is
Matches in the forward direction. The third birefringent wedge plate 33 is
The optical axis azimuth P is parallel to the tilting azimuth, and the tilting azimuth is 45 degrees, which is a left-down direction.

Reference numeral 3 is a lens for making the light emitted from the output side optical fiber 1 incident on the optical isolator as parallel rays, and 4 is a lens for converging the light emitted from the optical isolator onto the input side optical fiber 2.

In the polarization independent optical isolator as described above, the forward light emitted from the output side optical fiber 1 becomes parallel rays by the lens 3 as shown in FIG. Of the birefringent wedge plate 11, the first birefringent wedge plate 11 splits the polarization plane into two polarized light beams orthogonal to each other, refracts in different directions, and travels to reach the second birefringent wedge plate 32.

At this time, one polarized light is ordinary light (shown by a solid line).
Is incident on the second birefringent wedge plate 12, and the other polarized light is incident on the second birefringent wedge plate 12 as extraordinary light (shown by a dotted line).

Since the optical axis azimuth P of the first birefringent wedge plate 31 and the second birefringent wedge plate 32 are the same, the polarization planes of the respective polarizations do not change, and the second birefringent wedge plate is the same. 32
However, it refracts in different directions and progresses, reaching the Faraday rotator 35 of 45 degrees.

Then, the plane of polarization of each polarization is set to the right (when viewed from the forward direction) by 45 degrees Faraday rotator 35.
The third birefringent wedge plate 33 is reached after rotating three degrees. Since the optical axis direction P of the third birefringent wedge plate 33 is inclined by 45 degrees with respect to the second birefringent wedge plate 32, one polarization is the ordinary ray (shown by the solid line) and the third birefringent wedge plate 33. The other polarized light enters the third birefringent wedge plate 33 as extraordinary light (shown by a dotted line).

Here, as described above, the third birefringent wedge plate 33 has a wedge angle of 2 ^1/2 α, and the optical axis direction P of the second birefringent wedge plate 32 and the third birefringence. The optical axis direction P of the wedge plate 33 is inclined by 45 degrees.

Therefore, the two polarized lights become parallel light, pass through the optical isolator, reach the lens 4, are condensed on the incident end face of the input side optical fiber 2 by the lens 4, and travel in the input side optical fiber 2.

On the other hand, the light that is reflected back from the input side optical fiber 2 is the third birefringent wedge plate as shown in FIG.
The polarization plane is split into two polarizations orthogonal to each other by 33, refracted in different directions and proceed to reach the 45 ° Faraday rotator 15.

Then, by the 45 degree Faraday rotator 15,
The opposite direction to the forward direction (counterclockwise when viewed from the forward direction)
Then, the planes of polarization of the respective polarized lights are rotated by 45 degrees and reach the second birefringent wedge plate 32.

At this time, the relationship between the ordinary light and the extraordinary light is reversed. That is, since the ordinary light enters the second birefringent wedge plate 32 as the extraordinary light and the extraordinary light enters the second birefringent wedge plate 32, the two polarized lights are refracted in the expanding direction unlike the optical path in the forward direction and are refracted in the first birefringence. It reaches the refraction wedge plate 31, and is refracted by the first birefringent wedge plate 31 in the direction of further expansion.

Therefore, since the light travels in the direction away from the lens 3, it hardly enters the output side optical fiber 1. In FIG. 3, the polarization independent optical isolator comprises a first birefringent wedge plate 41 having a wedge angle α, a first 45 ° Faraday rotator 45, and a second birefringent wedge plate 42 having a wedge angle α.
And the second 45 degree Faraday rotator 46 and wedge angle α
And the third birefringent wedge plate 43 of FIG.

The first birefringent wedge plate 31 has an optical axis direction P
Is orthogonal to the tilt azimuth, and the tilt azimuth is upward. First
The magnetic field direction H of the 45-degree Faraday rotator 45 coincides with the forward direction. The optical axis direction P of the second birefringent wedge plate 42 is parallel to the tilt direction.

In the second 45-degree Faraday rotator 46, the magnetic field directions H coincide with each other in the opposite direction, and the third birefringent wedge plate 43 is used.
, The optical axis azimuth P is tilted by 30 degrees in the tilt azimuth. First, second, and third birefringent wedge plates 41, 42, 43, respectively
Is installed at an angle rotated by 120 degrees relative to the optical axis, and the optical axis direction P of the first birefringent wedge plate 41 and the second birefringent wedge plate 42 is inclined by 45 degrees, The optical axis direction P of the second birefringent wedge plate 42 and the third birefringent wedge plate 43 is inclined by 45 degrees in the negative direction.

In the polarization-independent optical isolator shown in FIG. 3, the three birefringent wedge plates are arranged so that the wedge angles are equal and the tilt azimuth forms an intersection angle of 120 degrees.
That is, since the sum of the vectors of the three birefringent wedge plates is zero, two polarized lights (ordinary and extraordinary) whose forward polarization planes are orthogonal to each other pass through the polarization independent optical isolator in parallel. To do.

On the other hand, the first, second and third birefringent wedge plates
A 45-degree Faraday rotator is interposed between each of 41, 42, and 43, and the first, second, and third birefringent wedge plates 41, 42,
The optical axis direction P of 43 is inclined by 45 degrees. Therefore, the sum of the vectors of the two polarizations in which the polarization planes of the separated light in the opposite direction are orthogonal to each other does not become zero, and the light propagates from the first birefringent wedge plate 41 in different angular directions.

As described above, in the case of using two 45 degree Faraday rotators, the deterioration of isolation due to imperfections of the 45 degree Faraday rotator and the like is extremely small. If the outer shapes of the birefringent wedge plate and the 45-degree Faraday rotator are disc-shaped and housed in a cylindrical holder, the birefringent wedge plate can be easily held at an inclination of 120 degrees. .

The polarization-independent optical isolator shown in FIG. 4 includes a first birefringent wedge plate 51 having a wedge angle α and a first birefringent wedge plate 51.
45 degree Faraday rotator 55, second birefringent wedge plate 52 with wedge angle α, and third birefringent wedge plate with wedge angle α
53, the second 45 degree Faraday rotator 56, and the wedge angle α
And the fourth birefringent wedge plate 54 are arranged in this order.

The first birefringent wedge plate 41 has an optical axis direction P
Is parallel to the tilt direction, and the tilt direction is upward. First
The magnetic field direction H of the 45-degree Faraday rotator 55 coincides with the forward direction, and the optical axis azimuth P of the second birefringent wedge plate 52 is tilted by 45 degrees in the tilt azimuth.

In the third birefringent wedge plate 53, the optical axis azimuth P is orthogonal to the tilt azimuth, and the second 45 ° Faraday rotator is used.
In 56, the magnetic field directions H coincide with the opposite directions, and the optical axis azimuth P of the fourth birefringent wedge plate 54 is tilted by 45 degrees in the tilt azimuth.

The respective first, second, third and fourth birefringent wedge plates 51, 52, 53 and 54 are relatively arranged around the optical axis.
It is installed at an angle rotated by 90 degrees. In the polarization independent optical isolator as described above, the light in the forward direction emitted from the output side optical fiber 1 becomes parallel rays by the lens 3 as shown in FIG. 5, and the light is directed to the first birefringent wedge plate 51. Reached
The first birefringent wedge plate 51 splits the polarization plane into two polarizations (shown by a solid line and a dotted line) that are orthogonal to each other, refracts in different directions, proceeds, and enters the first 45-degree Faraday rotator 55.

Then, the plane of polarization of each polarization is rotated by 45 degrees by the first 45 degree Faraday rotator 55 and reaches the second birefringent wedge plate 52. At this time, one polarized light is incident on the second birefringent wedge plate 52 as ordinary light (shown by a solid line), and the other polarized light is incident on the second birefringent wedge plate 52 as extraordinary light (shown on a dotted line).

Since the second birefringent wedge plate 52 and the first birefringent wedge plate 51 are arranged at an angle with the tilt azimuth rotated by 90 degrees, when they are incident on the second birefringent wedge plate 52, respectively. Polarized light is refracted in each incident plane, changes its traveling direction, and is incident on the third birefringent wedge plate 53.

Here, since the optical axis direction P of the second birefringent wedge plate 52 and the third birefringent wedge plate 53 is inclined by 45 degrees, the two polarized lights incident on the third birefringent wedge plate 53 are , And both of them enter the third birefringent wedge plate 53 as extraordinary light, and separate the respective polarized lights into two polarized lights whose polarization planes are orthogonal to each other.

On the other hand, since the third birefringent wedge plate 53 and the first birefringent wedge plate 51 are different in the inclination azimuth by 180 degrees, the respective four polarizations are the angles refracted by the first birefringent wedge plate 51. Refract in the direction to correct.

Then, the second 45-degree Faraday rotator 56 is reached, the plane of polarization of each polarization is rotated by 45 degrees, and the fourth plane is rotated.
Reach the birefringent wedge plate 54 of. At this time, the fourth birefringent wedge plate 54 and the second birefringent wedge plate 52 have an inclination direction of 18 degrees.
Since they are different from each other by 0 degree, the respective four polarized lights are refracted in the direction for correcting the angle refracted by the second birefringent wedge plate 52.

That is, since the sum of the vectors of the four birefringent wedge plates becomes zero, the four polarized lights become parallel lines and enter the lens 4, and are condensed on the incident end face of the input side optical fiber 2. Further, since the sum of the vectors of the four birefringent wedge plates does not become zero, the light in the opposite direction spreads from the first birefringent wedge plate 51 in different angular directions and travels to the output side optical fiber 1. Does not enter.

[0061]

As described above, the present invention selects all the birefringent wedge plates by selecting the wedge angle of the birefringent wedge plate, the optical axis direction, the tilt direction, and the magnetic field direction of the 45 ° Faraday rotator. 2 is the sum of the vectors of the
The birefringent wedge plate and the 45-degree Faraday rotator are set so that the sum of the vectors of all birefringent wedge plates does not become zero for two polarized lights in which the opposite polarization planes are orthogonal to each other. By arranging and, the deterioration of isolation is small and the degree of freedom in design is large, which is an excellent effect in practical use.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an optical path diagram of an embodiment of the present invention, (A) is a forward optical path diagram, and (B) is a reverse optical path diagram.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is a configuration diagram of still another embodiment of the present invention.

FIG. 5 is an optical path diagram of another embodiment of the present invention.

FIG. 6 is a diagram of a conventional example, (A) is a forward optical path diagram, and (B) is a reverse optical path diagram.

FIG. 7 is a block diagram of another conventional example.

[Explanation of symbols]

 1 Output side optical fiber 2 Input side optical fiber 3,4 Lens 11,21,31,41,51 First birefringent wedge plate 12,22,32,42,52 Second birefringent wedge plate 23,33, 43,53 Third birefringent wedge plate 24,54 Fourth birefringent wedge plate 15,35 45 degree Faraday rotator 25,45,55 1st 45 degree Faraday rotator 26,46,56 Second 45 Degree Faraday rotator

Claims (4)

[Claims] 1. A birefringent wedge plate comprising three or four birefringent wedge plates and one or two 45-degree Faraday rotators, wherein the tilt direction of the birefringent wedge plate is the vector direction, (wedge angle × refractive index). Is defined as the absolute value of the vector, the sum of the vectors of all the birefringent wedge plates becomes zero for the two polarizations whose forward polarization planes are orthogonal, and The wedge angle of the birefringent wedge plate, the optical axis azimuth, the tilt azimuth, and the magnetic field direction of the 45 ° Faraday rotator are set so that the sum of the vectors does not become zero for two polarized lights whose polarization planes in opposite directions are orthogonal. , A polarization-independent optical isolator characterized by being selected and arranged. 2. A first birefringent wedge plate (3) having a wedge angle α.
1), a second birefringent wedge plate (32) with a wedge angle α, a 45 ° Faraday rotator (35), and a third birefringent wedge plate (33) with a wedge angle 2 ^1/2 α are in this order. The first birefringent wedge plate (31) and the second birefringent wedge plate (32) are arranged so that the second birefringent wedge plate (31) and the second birefringent wedge plate (32) are rotated relative to each other by 90 degrees about the optical axis. The wedge plate (32) and the third birefringent wedge plate (33) are installed at an angle relatively rotated by 45 degrees about the optical axis, and the first birefringent wedge plate (31) and the third birefringent wedge plate (31) are provided. The optical axis direction is parallel to that of the second birefringent wedge plate (32), and the optical axis direction of the second birefringent wedge plate (32) and the third birefringent wedge plate (33) is inclined by 45 degrees. The polarization independent optical isolator according to claim 1, characterized in that 3. A first birefringent wedge plate (4) having a wedge angle α.
1), a first 45 degree Faraday rotator (45), a second birefringent wedge plate (42) with a wedge angle α, a second 45 degree Faraday rotator (46), and a third with a wedge angle α. Birefringent Wedge Plate (43)
Are arranged in this order, and each of the first, second, and third birefringent wedge plates (41, 4
2, 43) are installed at an angle of relative rotation of 120 degrees about the optical axis, and the first birefringent wedge plate (41) and the second birefringent wedge plate are provided.
The optical axis azimuth of (42) is inclined by 45 degrees, and the optical axis azimuth of the second birefringent wedge plate (42) and the third birefringent wedge plate (43) are inclined by 45 degrees. The polarization independent optical isolator according to claim 1, wherein 4. A first birefringent wedge plate (5) having a wedge angle α.
1), first 45 degree Faraday rotator (55), second birefringent wedge plate (52) with wedge angle α, third birefringent wedge plate (53) with wedge angle α, second 45 degree A Faraday rotator (56) and a fourth birefringent wedge plate (54) having a wedge angle α are arranged in this order, and each of the first, second, third and fourth birefringent wedge plates is arranged.
(51,52,53,54) are installed at an angle rotated by 90 degrees relative to the optical axis, and the first birefringent wedge plate (51) and the second birefringent wedge plate are provided.
The optical axis azimuth is inclined by 45 degrees with respect to (52), and the optical axis azimuth P is inclined by 45 degrees with respect to the third birefringent wedge plate (53) and the fourth birefringent wedge plate (54). The polarization independent optical isolator according to claim 1, characterized in that.