JP2000241764A - Optical circulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily assemble and to attach a large number of ports for entering and outgoing light. SOLUTION: This circulator is equipped with a first separating and mixing means 1 with respect to the propagation direction of light, second separating and mixing means 2 having almost perpendicular separation direction of polarized light to the first separating and mixing means 1, first polarization plane rotator 3 which is independent from the propagation direction of light, second polarization plane rotator 4 which depends on the propagation direction of light, third separating and mixing means 5, 6 divided into two parts with respect to the propagation direction of light, third polarization plane rotator 7 which depends on the propagation direction of light, fourth polarization plane rotator 8 which does not depend on the propagation direction of light, fourth separating and mixing means 9 having almost the same separation direction of polarized light as the second separating and mixing means 2, and fifth separating and mixing means 10 showing an almost the same separation direction of polarized light as the first separating and mixing means 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical passive component,
It mainly belongs to optical circulators used for organizing optical signal paths in optical communication.

[0002]

2. Description of the Related Art In an optical communication system, as the use of optical fiber amplifiers becomes active, the demand for optical circulators used for organizing optical signal paths and optical switches using optical circulators is increasing.

In a wavelength multiplex communication system,
It is considered that a large amount of a structure combining a narrow band filter and an optical circulator is required. Furthermore, the optical circulator is considered to be one of the optical devices that are in great demand in realizing an optical communication system in the future.

[0004] There are various conventional structures of a polarization-independent optical circulator having various structures. Among them, the optical circulator described in Japanese Patent No. 2539563 is a typical structure. .

This optical circulator separates light incident from a certain position of the first birefringent crystal into two polarization components, and the electric field oscillation of the light separated by the birefringent crystal by two reciprocal polarization rotators. The directions are aligned, and after that, after passing through the Faraday rotator arranged, the optical path is shifted by the second birefringent crystal. Thereafter, the direction of the electric field oscillation of the light transmitted through the Faraday rotator and separated by the birefringent crystals by the two reciprocal polarization rotators is made orthogonal, and two components are synthesized by the third birefringent crystal.

The light incident from the opposite direction does not shift its optical path in the second birefringent crystal, and as a result, exits at a position different from the first birefringent crystal incident position. The above operation is a basic operation of the optical circulator.

[0007]

In the optical circulator described in the prior art, a reciprocal polarization rotator or a non-reciprocal polarization rotator is used to make an electric field oscillation direction parallel or orthogonal. It is necessary to provide two or more units arranged along the traveling direction of the vehicle.

In this structure, two or more reciprocal polarization rotators or a plurality of non-reciprocal polarization rotators are arranged along a traveling direction of an incident light beam and a bonding surface of the plurality of reciprocal polarization rotators is connected. The lines need to be approximately parallel. Otherwise, light impinges on the bonding surface of a plurality of reciprocal polarization rotators or a plurality of non-reciprocal polarization rotators arranged along the traveling direction of the incident light, causing loss. Therefore, the conventional optical circulator has a problem that a very high bonding accuracy is required in disposing the optical element.

[0009] Therefore, the object of the present invention is to assemble easily,
An object of the present invention is to provide an optical circulator to which a number of light input / output ports can be attached.

[0010]

According to the present invention, there is provided an optical circulator having a plurality of light input / output ports, wherein a first separation / combination with respect to a light traveling direction is viewed from at least one of the light input / output ports. Means, a second separation / combination means whose polarization separation direction is substantially perpendicular to the first separation / combination means, and at least one first light independent of the light traveling direction.
A polarization plane rotation element, at least one second polarization plane rotation element depending on the light traveling direction, a third separating / combining means divided into two parts with respect to the light traveling direction, and at least one A third polarization plane rotation element that depends on the light traveling direction, and at least one fourth polarization plane rotating element that does not depend on the light traveling direction.
A polarization plane rotating element, a fourth separation / combination means whose polarization separation direction is substantially equal to the second separation / combination means, and a fifth separation / combination means whose polarization separation direction is substantially equal to the first separation / combination means. Wherein the polarization separation directions of the third separation / synthesis means are opposite to each other, and the first separation / synthesis means, the fifth separation / synthesis means, and the third separation / synthesis means are provided. An optical circulator is obtained, wherein the polarization separation directions of the means are substantially parallel to each other.

[0011]

According to the present invention, light is not separated and combined without using a plurality of reciprocal polarization rotators or non-reciprocal polarization rotators arranged along the traveling direction of incident light as in the prior art. Two sets of separating / combining means (birefringent crystals) whose directions are opposite to each other are provided along the traveling direction of the incident light beam.

In the present invention, Patent Registration No. 25395
Rather than having the birefringent crystal at the center of the optical element determine the two optical paths having the same polarization direction incident on the birefringent crystal as in the optical circulator of the invention described in No. 63,
After passing through two separation / combining means for separating two electric field vibration components and combining the two electric field vibration components incident on different optical paths into the same optical path, the electric field vibration components transmitted through the polarization plane rotation element are perpendicular to each other. Two light beams are incident on two birefringent crystals whose light separation and synthesis directions are opposite to each other, one of which is a birefringent crystal and the light emission position is shifted, and the other is emitted as it is to determine the optical path. I do. afterwards,
The light passes through the polarization plane rotation element, separates the two electric field vibration components, and is emitted again from one place through two separation / combining means for combining the two electric field vibration components incident on different optical paths into the same optical path.

In general, an optical circulator using a Faraday rotator can be formed as an optical switch by a mechanism for reversing the direction of a magnetic field applied to the Faraday rotator.

The behavior of the light beam incident on the first separation / combination means is that the light beam incident on one surface of the first separation / combination means is separated into two orthogonal electric field vibration components by the first separation / combination means. After that, the light is incident on one surface of the second separation / combination means, and the emission position of one of the two orthogonal electric field vibration components is shifted.

Thereafter, the light passes through the first and second plane-rotating elements. At that time, the direction of the electric field oscillation at the time of incidence is substantially maintained. Further, each of the light is incident on two third combining / separating means whose light separating / combining directions are opposite to each other, one is a birefringent crystal, the light emitting position is shifted by birefringence and emitted, and the other is emitted as it is.

Thereafter, the light passes through the third and fourth deflection surface rotating elements. At this time, the direction of the electric field oscillation at the time of incidence is substantially maintained, the light is incident on one surface of the fourth separation / combination means, and the emission position of one of the two orthogonal electric field oscillation components is shifted. Then, in the light beam incident on one surface of the fourth separating / combining means, two electric field vibration components orthogonal to each other are combined at one place by the fifth separating / combining means.

The behavior of the light beam incident on the first separation / combination means and exiting from the fifth separation / combination means is such that the light beam incident on one surface of the fifth separation / combination means is the fourth separation / combination means. The light is separated into two orthogonal electric field vibration components by the means, and then enters one surface of the fourth separation / combination means, and the emission position of one of the two orthogonal electric field vibration components is shifted.

Thereafter, the light passes through the third and fourth plane-rotating elements. At this time, the electric field vibration component rotates about 90 degrees from the electric field vibration component at the time of incidence. Further, each of the light is incident on two third separation / combination means whose light separation / combination directions are opposite to each other, one is a birefringent crystal, the light emission position is shifted by birefringence, and the other is emitted as it is. .

Thereafter, the light passes through the first and second plane-rotating elements. At this time, the direction of the electric field oscillation is rotated by about 90 degrees from the direction of the electric field oscillation at the time of incidence. Then, the light is incident on one surface of the second separation / combination means, and the emission position of one of the two orthogonal electric field vibration components is shifted. Further, the light beam incident on one surface of the first separation / combination means is different from the light beam when two electric field vibration components orthogonal to each other are incident on one surface of the first separation / combination means. Combined in one place at different locations.

Further, when the magnetic field applied to the Faraday rotator as the first to fourth polarization plane rotating elements is reversed, the light beam incident on one surface of the first separating / combining means is the first light. After the light beam incident on one surface of the separation / combination means is separated into two orthogonal electric field vibration components by the second separation / combination means, the light beam is incident on one surface of the third separation / combination means and becomes orthogonal. One emission position of the two electric field vibration components shifts.

Thereafter, the light passes through the third and fourth deflected plane rotating elements. At this time, the direction of the electric field oscillation is rotated by about 90 degrees from the direction of the electric field oscillation at the time of incidence. Further, each of the light is incident on two third separation / combination means whose light separation / combination directions are opposite to each other, one is a birefringent crystal, the light emission position is shifted by birefringence, and the other is emitted as it is. .

Thereafter, the light passes through the third and fourth plane-rotating elements. At this time, the direction of the electric field oscillation is rotated by about 90 degrees from the direction of the electric field oscillation at the time of incidence. Then, the light is incident on one surface of the fourth separating / combining means, and the emission position of one of the two orthogonal electric field vibration components is shifted.

Further, in the light beam incident on one surface of the fifth separating / combining means, two orthogonal electric field vibration components are combined at one place by the fifth separating / combining means. However, the combined position is different from the case where the direction of the magnetic field is not reversed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the optical circulator of the present invention will be described with reference to the drawings. FIG. 1 shows an arrangement of optical elements in the optical circulator according to the first embodiment.

This optical circulator has three or more light input / output ports. When viewed from at least one light input / output port among the three or more light input / output ports, the optical elements are used as optical elements 1-10. A first birefringent crystal (first separating / combining means) 1 with respect to the traveling direction, and a second birefringent crystal (second separating crystal) whose polarization separation direction is substantially perpendicular to the first birefringent crystal 1. Combining means) 2, at least one first polarization plane rotating element 3 independent of the light traveling direction, and at least one
A second polarization plane rotating element 4 depending on the light traveling direction of the sheet,
Two third birefringent crystals (first separation / synthesis means) 5, 6 divided into two in the light traveling direction, and at least one third polarization plane rotating element 7 depending on the light traveling direction; A fourth polarization plane rotating element 8 independent of at least one light traveling direction, a fourth birefringent crystal whose polarization separation direction is substantially equal to that of the second birefringent crystal 2 (fourth separation / combination means) 9
And a fifth birefringent crystal (fifth separating / combining means) 10 whose polarization separation direction is substantially equal to that of the first birefringent crystal 1.

The polarization separation directions of the two third birefringent crystals 5 and 6 are opposite to each other, and the first birefringent crystals 1 and 5
The polarization separation directions of the birefringent crystal 10 and the third birefringent crystals 5 and 6 are substantially parallel to each other.

In this embodiment, a rutile single crystal is used as the first to fifth birefringent crystals 1, 2, 5, 6, 9, and 10.
Bismuth-substituted gadolinium iron garnet which is a Faraday rotator as first and fourth polarization plane rotators 3, 8 independent of light traveling direction, second and third polarization plane rotators 4, 7 dependent on light traveling direction As a quartz half-wave plate,
A 3/2 wavelength plate, a 5/2 wavelength plate, or one type of optical rotator is used.

More specifically, first and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 adjacent to each other in a desired light traveling direction and second and third polarization planes The light of a predetermined wavelength transmitted through the plane rotation elements (1/2 wavelength plate, 3/2 wavelength plate, 5/2 wavelength plate, or a kind of optical rotator) 4, 7 has substantially the polarization plane of the incident light. In the opposite light traveling direction, the relationship that the polarization plane of the incident light is rotated by approximately 90 degrees is defined as the first and fourth directions.
Polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 and second and third polarization plane rotators (1/2 wavelength plate, 3/2 wavelength plate, 5/2 wavelength plate, or Optical rotation).

The Faraday rotator (bismuth-substituted gadolinium iron garnet) has no absorption edge near 1580 nm of bismuth-substituted terbinium iron garnet,
It can be used in a wide wavelength range from the 1300 nm band to the 2000 nm band. This can be said to be suitable for application in wavelength multiplexing communication, which has recently become popular.

The optical elements 1 to 10 include first to fifth optical elements.
Birefringent crystals 1, 2, 5, 6, 9, 10 and first and fourth polarization plane rotating elements 3, 8 independent of the light traveling direction, second and third polarization planes dependent on the light traveling direction Rotating element 4,
Reference numeral 7 is a parallel plate. The first to fifth birefringent crystals 1, 2, 5, 6, 9, and 10 are rutile parallel plates, and the first to fourth birefringent crystals (rutile parallel plates).
1, 2, 5, 6, 9 all have the same thickness, and the fifth birefringent crystal (rutile parallel plate) 10 is almost twice as thick as the first birefringent crystal (rutile parallel plate) 1. have.

FIGS. 2 to 4 show a state in which the optical elements 1 to 10 described in FIG. 1 are actually configured including the samarium cobalt-based magnet 12. Referring to FIGS. 2 to 4, first and fourth polarization plane rotators using bismuth-substituted gadolinium iron garnet (Faraday rotator; bismuth-substituted gadolinium iron garnet)
3 and 8, an external magnetic field 24 needs to be applied, and the samarium cobalt-based magnet 12
Is advantageous in terms of magnetic field strength and long-term reliability. A spacer 13 made of alumina is provided between the optical elements 1 to 10 and the magnet 12 in order to reduce distortion due to a difference in thermal expansion coefficient.
Is sandwiched between.

FIGS. 5 to 7 show the movement of the beam and the behavior of the plane of polarization in the five-port optical circulator having the configuration shown in FIGS. 5 to 7
Reference numerals 25 and 26 attached to the middle arrows indicate external magnetic fields. 5 to 7, which light input / output port (1) to
In (5), it can be seen that the optical circulator operates as a polarization independent optical circulator.

That is, as shown in FIGS. 5 to 7,
The route is from port (1) to port (2), port (2) to port (3), port (3) to port (4), port (4) to port (5), port (5). ) Indicates that the light travels outside the optical elements 1 to 10. However, if the optical elements 1 to 10 are large in the vertical direction in FIGS. 5 to 7, it can be understood that they operate as the port (6).

The behavior of the polarization plane in the optical elements 1 to 10 when traveling from the port (1) to the port (2) depends on the behavior of the optical elements 1 to 1 when traveling from the port (39 to the port (4)).
It can be seen that the behavior of the polarization plane within 0 is the same.

From this, it can be seen that in the optical circulator according to the present embodiment, the number of light input / output ports (1) to (5) is increased without increasing the number of optical elements 1 to 10. .

FIG. 8 shows the positions of the ports (1) to (14) viewed from the port (1) side. The dotted line in FIG. 8 is the third birefringent crystal (rutile parallel plate) shown in FIG.
This is a division surface 41 of a rutile parallel plate divided in the light traveling direction corresponding to 5 and 6. Also, reference numeral 27 in FIG.
Reference numerals to 40 denote light input / output ports (1) to (14). FIG. 9 shows the progress of light between the light input / output ports (1) to (14). Reference numerals 42 to 51 in FIG. 9 denote incoming and outgoing light at the light incoming and outgoing ports (1) to (10).

As described above, in the optical circulator, the first and fourth polarization plane rotation elements 3 and 8 that are independent of the light traveling direction are Faraday rotation elements, and the second and third polarization plane rotating elements that are dependent on the light traveling direction. The polarization plane rotation elements 4 and 7 are a half-wave plate, a 3 / 2-wave plate, a 5 / 2-wave plate or a type of optical rotator, and the first and fourth polarization plane rotations adjacent to each other in a certain light traveling direction. The elements (Faraday rotators) 3, 8 and the second and third polarization plane rotators (1/1 /
The light of a certain wavelength transmitted through the two-wavelength plate or the optical rotator 4 and 7 has a Faraday relationship in which the polarization plane of the incident light is substantially preserved and the polarization plane of the incident light is rotated by approximately 90 degrees in the opposite light traveling direction. Rotating element and 1/2 wavelength plate, 3/2 wavelength plate, 5 /
It has a two-wave plate or a rotator.

More specifically, the thickness of each of the optical elements 1 to 10 is the first to fourth birefringent crystals (rutile parallel plates) 1, 2, 2,
5, 6, 9 are 1 mm, the fifth birefringent crystal (rutile parallel plate) 10 is 2 mm, and the first and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 are 0.1 mm. 5mm, polarization plane rotation element (quartz 1/2
Wave plate) 4,7 is 0.092mm, about 7.2m in total
m. First and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3,
8, the polarization plane rotation angle is 45 degrees, and the C-axis angles of the second and third polarization plane rotation elements (1/2 wavelength plates) 4 and 7 are 22.5 degrees.
It is. In this case, adjacent first and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 and second and third polarization plane rotators (1/2 wavelength plates) 4, 7 Means that the positions may be interchanged. Adjacent first and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 and second and third polarization plane rotators (1 /
The light of a certain wavelength transmitted through the two-wavelength plates 4 and 7 preserves the polarization plane of the incident light, and in the opposite light traveling direction, the polarization plane of the incident light is rotated by 90 degrees.

The light transmitted through the optical elements 1 to 10 can be easily adjusted for the axes of the respective light input / output ports, and can be easily adjusted.
It is desirable that the thickness is close to a parallel light beam from the degree of freedom in designing the thickness.

In the optical circulator of the present embodiment, the insertion loss at the center wavelength is 0.5 dB or less at the light input / output port, and the isolation is 50 dB or more. In addition, since all polarization components have the same emission position,
PDL does not occur in principle.

Further, the optical circulator of the present embodiment uses two first and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 for rotating a so-called 45-degree polarization plane. In this case, the center wavelengths of these two first and fourth polarization plane rotators (Faraday rotator; bismuth-substituted gadolinium iron garnet) 3, 8 are shifted from each other, so that a wider wavelength range can be obtained. High isolation can be obtained.

FIG. 10 shows a second embodiment of the optical circulator. In FIG. 10, the same parts as those in the first embodiment described with reference to FIG.

Referring to FIG. 10, in optical elements 1 to 10 in the optical circulator, a square hysteresis curve is used as a Faraday rotator, which is the first and fourth polarization plane rotators 3 and 8 independent of the light traveling direction. A magnetized magnetic garnet is used.

As shown in FIGS. 5 to 7, the optical circulator of the first embodiment can increase the number of light input / output ports in any manner, but the number of optical elements 1 to 10 is three. Although there is no difference between the optical circulator and the 10-port optical circulator, the optical elements 1 to 10 must be large.

The first and fourth polarization plane rotating elements 3 and
In the bismuth-substituted gadolinium magnetic (iron) garnet used as 8, the direction of magnetization and the light traveling direction must be substantially parallel, and in the configuration having many light input / output ports in the first embodiment, the The lithium cobalt magnet 12 must be large.

However, magnetic garnets (Eu _0.9 Ho _1.1 Bi _1.0 Fe _4.2 Ga) having a square hysteresis curve are used as the first and fourth polarization plane rotators 3 and 8.
_{When 0.8} O ₁₂ ) is used, the magnetic garnet once magnetized and having a square hysteresis curve maintains the magnetization of about 350 Oe even after removing the external magnetic field, and the magnet is unnecessary. Reference numerals 64 and 65 attached to arrows in FIG. 10 indicate internal magnetization.

Therefore, the present embodiment greatly contributes to downsizing and high performance of the optical circulator. Also this effect, a bismuth-substituted gadolinium iron garnet 5-port optical circulator illustrated in FIGS. 5 to 7 Eu _0.9 H
o _1.1 Bi _1.0 Fe _4.2 Ga _0.8 O ₁₂ can also be obtained.

FIGS. 11 and 12 show a third embodiment of the optical elements 1 to 10 and the magnetic field applying means of the optical switch according to the present invention.

Referring to FIGS. 11 and 12, in this optical switch, a magnetic field applying means for the first and fourth polarization plane rotating elements 3 and 8 (Faraday rotators) independent of the light traveling direction in the optical circulator. It is possible to change the direction including the reversal of the magnetization of the Faraday rotator by means for switching the direction of the current applied to the current devices provided in the yokes 66, 68, 69 made of semi-hard magnetic material.

The configuration of the optical elements 1 to 10 is the same as that of the first embodiment, and the light emission port can be switched by reversing the direction of the magnetic field.

As means for switching the direction of the magnetic field, a coil 67 is provided around a yoke 66 made of an anti-hard magnetic material. Two yokes 68 and 69 made of two anti-hard magnetic materials are interposed between the optical elements 1 to 10 and the yoke 66. The configuration of the optical elements 1 to 10 is the same as the configuration of the first embodiment, and the light emission port can be switched by reversing the magnetic field direction.

The optical switch includes a coil 67 and a yoke 66 made of an anti-hard magnetic material as means for switching the magnetic field direction.
And applying a current to the coil 67 to reverse the direction of magnetization of the yoke 66 made of an anti-hard magnetic material. In addition, since the yoke 66 maintains the magnetic field even after the current is stopped in this embodiment, a self-holding optical switch can be obtained.

FIGS. 13 to 15 show the light input / output ports when the direction of the magnetic field is reversed with respect to the relationship between the movement of light between the light input / output ports and the behavior of the polarization plane described in FIGS. It shows the relationship between the movement of light between them and the polarization plane behavior. Note that the reference numeral 7 attached to the arrow in FIGS.
Reference numerals 1 and 72 denote external magnetic fields.

Referring to FIG. 13 to FIG. 15, the route of the port is from port (5) to port (4), port (4).
To port (3), port (3) to port (2)
From port (2) to port (1), it can be seen that the light travels from port (1) to outside the optical elements 1 to 10. Also, if the optical elements 1 to 10 are large in the vertical direction in FIGS. 11 and 12, it can be understood that they operate as the port (0).

The behavior of the plane of polarization in the optical elements 1 to 10 when traveling from the port (5) to the port (4) depends on the behavior of the optical elements 1 to 1 when traveling from the port (3) to the port (2).
It can be seen that the behavior of the polarization plane within 0 is the same.

From this, it can be seen that in the optical switch according to the present embodiment, the number of light input / output ports can be increased without increasing the number of optical elements 1 to 10. Furthermore, it can be said that the optical switch in the present invention reverses the external magnetic fields 71 and 72 to reverse the direction of light transmission between the ports.

FIG. 16 shows the direction of application of the magnetic field and the movement of light between the light input / output ports. Reference numerals 42 to 5 in FIG.
Reference numeral 1 denotes incoming / outgoing light at the light input / output ports (1) to (10). Reference numeral 73 in FIG. 16 indicates an external magnetic field that can be reversed in direction. Further, reference numerals 74 to 8
Reference numeral 3 indicates the progress of light between the light input / output ports when the external magnetic field is reversed.

FIGS. 17 and 18 show a fourth embodiment of the optical element and the magnetic field applying means of the optical switch according to the present invention.

Referring to FIGS. 17 and 18, in this optical switch, a magnetic field applying means for the first and fourth polarization plane rotators 3 and 8 (Faraday rotators) independent of the light traveling direction in the optical circulator. It is possible to change the direction including the reversal of the magnetization of the Faraday rotator by means for switching the direction of the current applied to the current devices provided in the yokes 85, 87, 88 made of semi-hard magnetic material.

The configuration of the optical elements 1 to 10 is the same as that of the first embodiment, and the light emission port can be switched by reversing the direction of the magnetic field.

As means for switching the direction of the magnetic field, a coil 86 is provided around a yoke 85 made of an anti-hard magnetic material. Between the optical elements 1 to 10 and the yoke 85, yokes 87 and 88 made of two anti-hard magnetic materials are interposed.

As a means for switching the direction of the magnetic field, a coil 86 is wound around the soft magnetic ferrite yokes 85, 87, 88, and a current flows through the coil 86 to reverse the direction of magnetization of the yoke made of an anti-hard magnetic material. As a method of reversing the direction of the magnetic field applied to the first and fourth polarization plane rotators (Faraday rotators) 3 and 8, a means for switching the direction of the current applied to the current device provided in the soft magnetic ferrite is used. The switching speed can be increased. Also in this embodiment, since the yoke keeps the magnetic field even after the current is stopped, it is possible to form a self-holding optical switch.

As the soft magnetic ferrite of the present invention, Mn-Zn ferrite, Ni-based ferrite, Li-based ferrite, Ni-Z
N-based ferrite and Li-Zn-based ferrite are preferred. Also, by using these as magnetic core materials,
Switching from DC to about 100 MHz becomes possible.

FIGS. 19 and 20 show a method of manufacturing an optical element according to the fifth embodiment of the present invention. In this embodiment, no adhesive is used for joining the optical circulator and the optical switch component.

FIGS. 19 and 20 are views in which each optical element of the method for manufacturing an optical element is inserted into the concave metal case 112. FIG. All optical elements 113 to 121 are 2 mm x 1 mm
The rutile parallel plate 117 is 2m in total.
m × 1 mm.

The concave metal case 112 is made of a material having a low magnetic permeability or a magnet, and has grooves 122 to 130 for inserting respective optical elements. These grooves 122-1
After each optical element is inserted into 30, it is fixed with gold tin solder or glass solder.

In the first embodiment, the crystal 1 /
Although a two-wavelength plate was used, its thickness was very small, 0.092 mm, and it was difficult to use this embodiment. So 3/2
It is also effective to use a wave plate and a 5/2 wave plate.

As described above, the structure in which the constituent members are fixed with gold tin solder or glass solder without using an adhesive is excellent in environmental resistance performance and has little change with time. Further, since there is no adhesive in the light transmitting surface, the light damage resistance is excellent.

However, since it is impossible to mass-produce the optical elements by bonding them with a large plate, the price is inevitably higher than the optical element produced by the production method shown in the first embodiment. . Therefore, which manufacturing method is used is selected according to the purpose of use of the optical circulator and the optical switch.

FIGS. 21 and 22 show a sixth embodiment of the present invention in which prisms 131 to 134 composed of total reflection mirrors are provided before and after the optical element of the optical circulator and optical switch according to the present invention. By using this embodiment, the interval between the fiber collimators serving as the light input / output ports can be widened, and the fiber collimator can be easily attached.

[0071]

As described above, according to the optical circulator of the present invention, the first separation / combination means with respect to the light traveling direction and the second separation / combination direction whose polarization separation direction is substantially perpendicular to the first separation / combination means 1 are provided. A second separating / combining unit, a first polarization plane rotating element independent of the light traveling direction, a second polarization plane rotating element dependent on the light traveling direction, and two third divided into two parts with respect to the light traveling direction. Separation / combination means, a second polarization plane rotation element dependent on the light traveling direction, a third polarization plane rotation element independent of the light traveling direction, a fourth polarization plane direction substantially equal to the second separation / combination means 2 And a fifth separation / combination means having a polarization separation direction substantially equal to that of the first separation / combination means, so that the polarization is easy to assemble and to which a large number of light input / output ports can be attached. Independent optical circulator and optical switch Seisuru can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an arrangement of optical elements in a first embodiment of an optical circulator of the present invention.

FIG. 2 is a side sectional view when the optical element of FIG. 1 is actually configured including a magnet.

FIG. 3 is a left side sectional view of the optical element of FIG. 1;

FIG. 4 is a plan sectional view of the optical element of FIG. 1;

5 is an explanatory diagram showing beam movement and polarization plane behavior in the five-port optical circulator having the configuration of FIG. 1;

FIG. 6 is an explanatory diagram showing beam movement and polarization plane behavior in the 5-port optical circulator having the configuration of FIG. 1;

FIG. 7 is an explanatory diagram showing beam movement and polarization plane behavior in the five-port optical circulator having the configuration of FIG. 1;

FIG. 8 is an explanatory diagram showing the position of each port as viewed from the port (1) shown in FIG. 1;

FIG. 9 is an explanatory diagram showing the progress of light between ports shown in FIG. 1;

FIG. 10 is a perspective view showing an arrangement of optical elements in a second embodiment of the optical circulator of the present invention.

FIG. 11 is a plan view showing an optical element and a magnetic field applying means of an optical switch according to a third embodiment of the optical circulator of the present invention.

FIG. 12 is a front sectional view of FIG. 11;

FIG. 13 shows the relationship between the movement of light between the light input / output ports and the polarization plane behavior when the direction of the magnetic field is reversed, in contrast to the relation between the movement of light between the light input / output ports and the polarization plane behavior in FIG. FIG.

FIG. 14 shows the relationship between the movement of light between the light input / output ports and the polarization plane behavior when the direction of the magnetic field is reversed, in contrast to the relation between the movement of light between the light input / output ports and the polarization plane behavior in FIG. FIG.

FIG. 15 shows the relationship between the movement of light between the light input / output ports and the polarization plane behavior when the direction of the magnetic field is reversed, in contrast to the relation between the movement of light between the light input / output ports and the polarization plane behavior in FIG. FIG.

FIG. 16 is an explanatory diagram showing the direction of application of a magnetic field and the movement of light between each light input / output port.

FIG. 17 is a plan view showing an optical element and a magnetic field applying means of an optical switch according to a fourth embodiment of the optical circulator of the present invention.

18 is a front sectional view of FIG.

FIG. 19 is a plan sectional view showing a fifth embodiment of the method for manufacturing an optical element according to the present invention.

FIG. 20 is a plan sectional view of the optical element of FIG. 19;

FIG. 21 is a plan sectional view showing a sixth embodiment of the present invention having a prism having a total reflection mirror before and after the optical element portion of the optical circulator and the optical switch according to the present invention.

FIG. 22 is a plan sectional view of the optical circulator of FIG. 21;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st birefringent crystal 2 2nd birefringent crystal 3,8 1st polarization plane rotation element which does not depend on a light propagation direction 4,7 2nd polarization plane rotation element which depends on a light propagation direction 5,6th Birefringent crystal 3 9 Fourth birefringent crystal 10 Fifth birefringent crystal 11, 24, 25, 26, 71, 72 External magnetic field 12 Samarium cobalt magnet 13 Spacer 27, 28, 29, 30, 31, 31, 32, 33, 34, 3
5, 36, 37, 38, 39, 40 From the light input / output port (1) to (14) 42, 43, 44, 45, 46, 47, 48, 49, 5
0,51 Input / output light at the light input / output ports (1) to (10) 64,65 Internal magnetization 66 Yoke made of semi-hard magnetic material 67,86 Coil 68,69 Yoke made of semi-hard magnetic material 85,87,88 Soft Yoke made of magnetic ferrite 112 Metal case 131, 132, 133, 134 Prism 135 Support base

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H079 AA03 BA02 CA06 DA13 EA11 EA33 KA05 KA17 2H099 AA01 BA06 CA08 DA05 5K002 AA07 BA02 BA04 BA06

Claims (11)

[Claims] 1. An optical circulator having a plurality of light input / output ports, comprising: a first separation / combination means with respect to a light traveling direction when viewed from at least one of the light input / output ports;
A second separation / combination means whose polarization separation direction is substantially perpendicular to the first separation / combination means, at least one first polarization plane rotation element independent of the light traveling direction,
A second polarization plane rotating element depending on the light traveling direction, a third separating / combining means divided into two parts with respect to the light traveling direction, and at least one third polarizing plane rotating element dependent on the light traveling direction A polarization plane rotation element, at least one fourth polarization plane rotation element independent of the light traveling direction, and a fourth separation / combination means whose polarization separation direction is substantially equal to the second separation / combination means. A fifth separation / synthesis unit having the polarization separation direction substantially equal to the first separation / synthesis unit, wherein the polarization separation directions of the third separation / synthesis unit are opposite to each other; An optical circulator, wherein the polarization separation directions of the first separation / combination means, the fifth separation / combination means, and the third separation / combination means are substantially parallel to each other. 2. The optical circulator according to claim 1, wherein said first to fifth separation / combination means are birefringent crystals. 3. The optical circulator according to claim 1, wherein said first to fifth separation / combination means and said first and second separation / combination means are provided.
An optical circulator wherein the fourth polarization plane rotating element is formed of a parallel plate. 4. The optical circulator according to claim 1, wherein at least one or more of the light input / output ports are provided.
An optical circulator having a prism composed of a total reflection mirror. 5. The optical circulator according to claim 1, wherein said first to fourth separation / combination means all have substantially the same thickness, and said fifth separation / combination means comprises said first to fourth separation / combination means. An optical circulator comprising a parallel flat plate having a thickness almost twice as large as the combining means. 6. The optical circulator according to claim 1, wherein the first and third polarization plane rotation elements independent of the light traveling direction are Faraday rotators, and the second and third polarization rotators dependent on the light traveling direction. The fourth polarization plane rotation element is ２
The Faraday rotator and the half-wave plate, which are composed of one type of a wave plate, a 3 / 2-wave plate, a 5 / 2-wave plate, or an optical rotator, and are adjacent to each other in the traveling direction of desired light.
The light having a predetermined wavelength transmitted through a wave plate, a 5 / 2-wave plate, or a type of optical rotator substantially preserves the polarization plane of the incident light, and in the opposite light traveling direction, the polarization plane of the incident light is substantially An optical circulator, wherein the Faraday rotator and the half-wave plate or the optical rotator have a relationship of rotating by 90 degrees. 7. The Faraday rotator according to claim 7, wherein the Faraday rotator is a means for applying a magnetic field to the Faraday rotator, wherein the Faraday rotator is provided with a yoke made of a semi-hard magnetic material and switches a direction of a current applied to a current device. An optical circulator characterized in that the optical circulator can be changed, including inverting the magnetization of the optical circulator. 8. The optical circulator according to claim 7, wherein said magnetic field applying means for said Faraday rotator is a means for switching the direction of an applied current to a current device provided in a soft magnetic ferrite. An optical circulator characterized by being an optical switch that can be changed, including inverting. 9. The optical circulator according to claim 1, wherein the first and third polarization plane rotations are independent of the light traveling direction. An optical circulator using a Faraday rotator using bismuth-substituted gadolinium iron garnet as an element. 10. An optical circulator according to claim 1, wherein light entering and exiting the optical switch according to claim 7 or 8 is substantially parallel light in the optical element or in the optical element and in the vicinity thereof. An optical circulator characterized in that: 11. The optical circulator according to claim 7, wherein a magnetic garnet having a square hysteresis curve is magnetized as the Faraday rotator that is the first and third polarization plane rotators independent of the light traveling direction. An optical circulator characterized by using an object.