JPH1152293A - Optical isolator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate optical alignment at the time of assembly and to realize miniaturization and economization. SOLUTION: Light in a forward direction from an optical waveguide 1a having TEC(terminal expanded core) structure is changed to parallel beams at a lens part 1c; the 1st half of the light is transmitted through a 1/2 wavelength plate 3a and a magnetic garnet 5 and made incident on a lens part 1; and the 2nd half of the light is transmitted through the magnetic garnet 5 and a 1/2 wavelength plate 3b, made incident on a lens part 1b, synthesized with the 1st half of the light and emitted through an optical waveguide 1b. The transmitted light in a reverse direction from the waveguide 1b is changed to the parallel beams at a lens part 1d; the 1st half of the light is transmitted through the magnetic garnet 5 and the plate 3a and made incident on the lens part 1c; and the 2nd half of the light is transmitted through the plate 3b and the magnetic garnet 5, made incident on the lens part 1c and negated with the 1st half of the light each other so as not to be transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator that transmits only forward transmission light with low loss and blocks reverse return light, and more particularly, as an optical passive component, mainly for optical communication related optical signal transmission. The present invention relates to an optical isolator used for organizing paths.

[0002]

2. Description of the Related Art In an optical communication system, use of an optical fiber amplifier for directly amplifying an optical signal as it is without replacing the optical signal with an electric signal has been studied in recent years. In this case, an Er-doped optical fiber having a specific length is installed in the amplifier, and the amplified signal light and pumping light are transmitted therethrough to obtain amplified light. It is indispensable for an optical fiber amplifier to use an optical isolator that transmits only transmitted light in the forward direction with low loss and blocks return light in the reverse direction.

There are two types of optical isolators: a polarization-dependent type that transmits only a specific polarization component of the transmitted light in the forward direction, and a polarization-independent type that transmits all components of the transmitted light. Although both optical isolators are used in an optical communication system, the polarization-dependent type is often used in the vicinity of an optical communication laser, and the polarization-independent type is often used in the middle of an optical fiber through which signal light passes. Of these, a polarization-independent optical isolator having a relatively complicated structure is of the type using a parallel birefringent flat plate (Japanese Patent Laid-Open No. 54-159245) and the type using a tapered birefringent plate (Japanese Patent Publication No. 61-159). No. 58809) have been proposed.

[0004] An example of the polarization-independent optical isolator shown in FIG. 10 is proposed by Shintaku et al. (Spring 1997 IEICE General Conference C-3-98, p283, Newly-structured polarization-independent optical isolator). An optical isolator having a magnetic garnet 101 as one Faraday rotator, two half-wave plates 102, and two lens mechanisms 103, and having optical fibers 104a and 104b at both ends. Also, 105 is a magnet for applying a magnetic field to the magnetic garnet 101. In the optical isolator of FIG. 10, when separating transmitted light, it does not separate into polarized light components orthogonal to each other, but the same intensity where polarized components are mixed. To separate the light. The two types of separated light include the same amount of the same polarization component, and in the case of forward transmission light incident from the optical fiber 104a, the light is combined again at the end face of the optical fiber 104b after passing through the exit lens. In this case, since the two separated lights to be combined are in a mutually reinforcing relationship, the transmitted light passes through the optical isolator without attenuation. It is most desirable that the light transmitted through the magnetic garnet 101, which is a Faraday rotator between the two lenses 103, and the half-wave plate 102 be parallel light.

On the other hand, in the case of transmitted light in the opposite direction in this optical isolator, the lights separated after passing through the optical fiber 104b have a relationship of canceling each other when they are combined at the end of the optical fiber 104a. Therefore, the backward transmitted light does not pass through the optical fiber 104a, and it can be seen that the optical device functions as an optical isolator.

In recent years, a wavelength division multiplexed signal (W), which simultaneously transmits optical signals of a plurality of wavelengths through one optical fiber, has been developed.
As the DM (DM) technology advances, an optical device capable of simultaneously processing a plurality of optical signals is required. The optical isolator is also required to have a parallel-type structure for simultaneously processing a plurality of optical signals independently, and an array-type structure in which a plurality of optical isolators having the same structure are arranged side by side has been proposed.

[0007]

As described above, WD
With the development of the M technology, an array-type optical isolator capable of simultaneously processing a plurality of optical signals has been demanded. The above-mentioned polarization-independent optical isolator shown in FIG. 10 was used for this array-type optical isolator. In this case, the following problem occurs.

That is, in the polarization-independent optical isolator shown in FIG. 10, the two separated lights do not follow completely different paths in a state where they are separated from each other. It is considered that each half of the transmitted light is half. Since the two types of transmitted light are combined again into one light after passing through different optical elements, the notation is made that they are separated into two, but in reality, the boundary between the two separated lights is It is considered to be a region where the light intensity of the transmitted light is usually the maximum because the boundary is located at the center of the light transmission region. Since such transmitted light passes through the half-wave plate, which is a different optical element, the light transmitted through the side area of the optical element scatters or interferes with the irregular behavior. Is thought enough. It is considered that the influence of such light becomes remarkable especially in the case of transmitted light in the reverse direction.

It is very difficult to reduce the scattered light to zero due to the structure of the optical isolator. A factor that further increases such scattered light is that when the transmitted light between the two lenses is not parallel light, the transmitted light is incident on the end face of the optical element from an oblique direction. (Because the end face of the element is parallel, the amount of light reflected and scattered at the end face is very small.) Since the installation position of the half-wave plate is structurally different in the transmission path of the two separated lights, In order to install an independent lens in the optical path, where the end faces of the optical element of the two separated light are not aligned and the stepped area becomes a source of reflection / scattering, including the part that becomes the holder, A certain amount of volume is absolutely necessary in the optical path, and as a result, the optical distance between the two optical fibers 104a and 104b becomes longer, which is necessary for bonding and fixing the half-wave plate installed on the front and back of the Faraday rotator. Precise positioning It is difficult, and because both the optical element is a half the size of each Faraday rotator, a slight overflow of the bonding agent at the time of bonding can be considered the reason for such to scatter transmitted light.

This problem also occurs in an array type optical isolator. In the case of the array type, optical alignment must be performed for all of a large number of optical isolator configurations. Difficulties are a particular problem. In the case of an array type optical isolator, it is required that the optical alignment at the time of assembling the optical elements be completed only once at the same time for all the optical isolator configurations.

[0011] The present invention has been made in view of the above,
It is an object of the present invention to provide an optical isolator which facilitates optical alignment at the time of assembly, and is downsized and economical.

[0012]

According to a first aspect of the present invention, there is provided a first plurality of optical waveguides each having a lens portion formed at one end thereof and disposed in parallel with each other.
A second plurality of optical waveguides having a lens portion formed at one end of each of the first plurality of optical waveguides facing each of the lens portions and disposed in parallel with the first and second optical waveguides;
A first half of light from each lens unit of the first plurality of optical waveguides, and a Faraday rotator disposed between the lens units of the plurality of optical waveguides. A first 1/1 joined to a first half of a first surface of the Faraday rotator facing a lens portion of the first plurality of optical waveguides so that light is directly transmitted through the Faraday rotator. 2
A wave plate and a second half of a second surface of the Faraday rotator opposite to the first surface, the second surface of the Faraday rotator being separated from a second half of the second surface of the Faraday rotator. A second half of the light is transmitted and incident on the lens portion of the second plurality of optical waveguides, and the first half of the light from the Faraday rotator is directly transmitted to the second plurality of optical waveguides. The gist of the present invention is to include a second half-wave plate incident on the lens unit and a magnetic field applying unit for applying a magnetic field to the Faraday rotator.

According to the present invention, the transmitted light in the forward direction from the first plurality of optical waveguides becomes parallel light at the lens portion, and the first half of the light is converted to the first light. The second half of the light enters the lens portion of the second plurality of optical waveguides via the half-wave plate and the Faraday rotator, and the second half light passes through the second half-wave plate via the Faraday rotator and the second half-wave plate. Are incident on the lens portions of the plurality of optical waveguides, and are combined with the first half light,
The light transmitted through the second plurality of optical waveguides and emitted, and the transmitted light in the opposite direction from the second plurality of optical waveguides becomes parallel light at its lens portion, and the first half of the light is a Faraday rotator,
The light enters the lens portion of the first plurality of optical waveguides via the first half-wave plate, and the second half of the light enters the first half via the second half-wave plate and the Faraday rotator. Are incident on the lens portions of the plurality of optical waveguides, and cancel each other out with the first half of the light so that they cannot be transmitted.

According to a second aspect of the present invention, there is provided a first plurality of optical waveguides disposed in parallel, and one end of each of the first plurality of optical waveguides connected to one end of each of the first plurality of optical waveguides, The light incident from one side of each of the two
A first plurality of light combining / branching means that branches into two, emits from the other side of each pair, combines light incident from the other side of each pair, and emits from each one side;
One end of each pair is provided on the other side of each pair of the first plurality of light combining / branching means to separately guide the first and second lights branched by the first plurality of light combining / branching means. A first plurality of pairs of optical waveguides connected to each other and having a pair of lens portions formed at the other end of each pair,
A pair of lens portions are formed at one end of each pair and are disposed in parallel with the respective pair of lens portions formed at the other end of each pair of the first plurality of optical waveguides. A second pair of optical waveguides, and one end of each pair is connected to the other end of each pair of the second plurality of optical waveguides. The light incident on one side of each pair from the other end of each pair is synthesized, emitted from each other side, and the light incident from each other side is split into two. A second plurality of light combining / branching means for emitting light from one side of each pair, and a second plurality of light waveguides connected to the other side of the second plurality of light combining / branching means and arranged in parallel And between each pair of lens portions of the first and second pairs of optical waveguides And light from each one of the lens units of each pair of the first plurality of optical waveguides is directly incident on one side, and each of the second plurality of optical waveguides is A Faraday rotator in which light from each one of the pair of lens parts is directly incident on the other side,
A first half-wave plate disposed between one surface of the Faraday rotator and the other lens unit of each pair of lens units of the first plurality of optical waveguides; A second half-wave plate disposed between the other surface of the Faraday rotator and each of the other lens units of the pair of lens units of the second plurality of optical waveguides; It is essential to have a magnetic field applying means for applying a magnetic field to the Faraday rotator.

According to the second aspect of the present invention, the transmitted light in the forward direction from the first plurality of optical waveguides is branched by the first optical coupling / branching means, and the branched first and second optical waveguides are separated. The light passes through a first plurality of pairs of optical waveguides and becomes parallel light at a lens portion thereof, and the first light is a first half-wave plate, a Faraday rotator, and a lens portion of a second plurality of pairs of optical waveguides. On the other hand, the second
Through one of the plurality of pairs of optical waveguides to reach the second optical coupling / branching means, where the second light is a Faraday rotator and a second half.
The wavelength plate, the other of the lens parts of the second plurality of pairs of optical waveguides, and the other of the second plurality of pairs of optical waveguides pass through to the second optical coupling / branching means, where the light is combined with the first light, and the second light is combined. Out of the plurality of optical waveguides, and transmitted light in the opposite direction from the second plurality of optical waveguides is branched by the second optical coupling / branching means, and the branched first and second lights are converted into the second light by the second optical coupling / branching means. The light becomes parallel light at the lens portion through the plurality of pairs of optical waveguides, and the first light is one of the Faraday rotator, the first half-wave plate, and one of the lens portions of the first plurality of pairs of optical waveguides. Through one of the plurality of pairs of optical waveguides to reach the first optical coupling / branching unit, and the second light is transmitted through the second optical waveguide.
, A Faraday rotator, the other of the lens portions of the first plurality of pairs of optical waveguides, and the other of the second plurality of pairs of optical waveguides, to the first optical coupling / branching means, With each other and cannot be transmitted.

Further, the present invention according to claim 3 provides the invention according to claim 1.
In the invention described in (2), the first and second plurality of optical waveguides and the first and second plural pairs of optical waveguides are optical waveguides having a TEC structure having an enlarged portion as the lens portion. Make a summary.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the first and second pluralities of optical waveguides and the first and second plural pairs of optical waveguides are provided with the lens. The gist of the present invention is that the optical waveguide has a spherical lens having a spherical lens as a portion.

According to a fifth aspect of the present invention, there is provided a first plurality of optical waveguides having a PLC structure arranged in parallel,
A second plurality of optical waveguides having a PCL structure, wherein one end of each of the first plurality of optical waveguides is disposed in parallel with one end facing each other; and the first and second plurality of optical waveguides A first half of light from one end of each of the first plurality of optical waveguides, and a second half of the light from the Faraday rotator disposed between the opposite ends of the Faraday rotator. A first half-wave plate bonded to a first half of a first surface of the Faraday rotator opposite one end of each of the first plurality of optical waveguides so as to directly pass through the rotator; And a second half of a second surface of the Faraday rotator opposite to the first surface, the second half being from a second half of a second surface of the Faraday rotator. Half of the light is transmitted, enters the second plurality of optical waveguides, and the Faraday rotator The first half of the light has a second half-wave plate directly incident on the second plurality of optical waveguides, and a magnetic field applying means for applying a magnetic field to the Faraday rotator. And

According to a fifth aspect of the present invention, a PLC
The transmitted light in the forward direction from the first plurality of optical waveguides having the structure is separated into two lights by the PLC structure, and the first half light is transmitted through the first half-wave plate and the Faraday rotator. , PL
A second plurality of optical waveguides having a C structure;
Half of the light passes through the Faraday rotator and the second half-wave plate, reaches the second plurality of optical waveguides having the PLC structure, is combined with the first half of the light, and is combined with the second half. And the transmitted light in the opposite direction from the second plurality of optical waveguides is split into two lights by the PCL structure, and the first half light is a Faraday rotator, a first half-wave plate. To the second plurality of optical waveguides, and the second half of the light passes through the second half-wave plate and the Faraday rotator,
When the plurality of optical waveguides are combined by the PLC structure of the second plurality of optical waveguides, they cannot be transmitted because they cancel each other out with the first half light.

[0020] Further, the present invention described in claim 6 is based on claim 1.
In the invention described in any one of the first to fifth aspects, the light transmission surfaces of the Faraday rotator and the first and second half-wave plates are arranged to be inclined from a plane perpendicular to the transmitted light. That is the gist.

According to the present invention, the light transmitting surfaces of the Faraday rotator and the first and second half-wave plates are disposed obliquely from a plane perpendicular to the transmitted light. Therefore, it is possible to prevent the reflected light from the optical element from returning to the optical waveguide and re-entering the optical waveguide.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are a top view and a vertical sectional view, respectively, showing the configuration of an optical isolator according to a first embodiment of the present invention. In the figure, 1a and 1
b denotes an optical waveguide having a TEC (Thermal Expanded Core) structure, and each end is provided with lens portions 1c and 1d formed by enlarging the core portion by heating. 3a and 3b are half-wave plates, and 5
Is a magnetic garnet 5 which is a Faraday rotator, and 7
Is a substrate. In FIG. 1, means for applying a magnetic field to the magnetic garnet 5, which is a Faraday rotator, is omitted.

In the optical isolator thus configured, the transmitted light in the forward direction from the plurality of optical waveguides 1a having the TEC structure becomes parallel light at the lens portion 1c.
The first half of the light passes through the half-wave plate 3a and the magnetic garnet 5 which is a Faraday rotator in this order, enters the lens unit 1d without passing through the half-wave plate 3b, and passes through the second half. Half of the light does not pass through the half-wavelength plate 3a, and the magnetic garnet 5, 1/2
The light passes through the wave plate 3b in order, enters the lens portion 1d, is combined with the first half light, and exits through the optical waveguide 1b.

The transmitted light in the opposite direction from the optical waveguide 1b having the TEC structure becomes parallel light at the lens portion 1d, and the first half of the light passes through the magnetic garnet 5 and the half-wave plate 3a. Then, the second half light is transmitted through the half-wave plate 3b and the magnetic garnet 5 and is incident on the lens unit 1c, and is canceled by the first half light. It cannot be transmitted.

The lens portions 1c and 1d have a function as lenses by expanding the diameter of the optical fiber to several times by heating the core portion thereof.
Among the optical waveguides 1a and 1b having the TEC structure, those using an optical fiber are also called core expanded fibers. Then, light emitted from the optical waveguide 1a having the TEC structure becomes parallel light.

In this embodiment, the half-wave plate 3a,
3b and the magnetic garnet 5 constitute an optical element,
Assuming a transmitted light of 1.55 μm which is a communication wavelength band, the thickness of the magnetic garnet 5 is generally about 500 μm, and when the 波長 wavelength plates 3 a and 3 b are made of quartz,
Their thickness is about 90 μm each.

The optical isolator of the present embodiment is different from the conventional optical isolator shown in FIG. 10 in that the optical waveguides 1a, 1d integrally having lens portions 1c, 1d by the TEC structure.
By providing a plurality of 1b in parallel, an arrayed optical isolator is formed. Then, the lens portions 1c,
Since 1d is provided integrally with the optical fibers serving as the optical waveguides 1a and 1b, the optical alignment work and optical adjustment at the time of assembling are easy, and the total length of the optical isolator is shortened, thereby reducing the size. Accordingly, the area of each optical element used can be reduced, and the cost can be reduced. Assuming the above-mentioned transmitted light of 1.55 μm, the distance between the optical waveguides 1a and 1b on both sides is 1 m.
m or less.

That is, in the optical isolator of the present embodiment, the optical adjustment of the optical waveguide and the lens unit can be performed in advance by the optical waveguides 1a and 1b having the TEC structure integrally having the lens units 1c and 1d. It is possible to facilitate the optical positioning work of the assembling type of the isolator, and to reduce the size of the optical element. Further, the transmitted light between the lens portions 1c and 1d of the respective optical waveguides is always maintained as a parallel light or a state close to the parallel light, so that the optical characteristics of the optical isolator can be improved. Since no optical adjustment between the waveguides 1a and 1b is required,
Since adjustment after assembly is easy and a structure for separately holding the lens portion is not required, a very small element is sufficient, and the total length of the optical isolator can be shortened. Furthermore, the area occupied by the optical element composed of the Faraday rotator and the half-wave plate required for one optical isolator structure can be reduced, and the cost can be reduced. In the array type optical isolator as in the present embodiment, only the optical element is commonly used, a large number of independent light input / output ends are provided, and a large number of independent optical isolator functions can be provided. In addition, the area occupied by the optical element per optical isolator structure can be reduced, and the number of optical isolator structures that can be arrayed for optical elements of the same size can be increased.

FIGS. 2A and 2B are a top view and a vertical sectional view, respectively, showing the configuration of an optical isolator according to a second embodiment of the present invention. In the optical isolator according to the second embodiment shown in FIG. 5, the magnetic garnet 5 constituting the Faraday rotator in the optical isolator shown in FIG.
The configuration is different from that of the optical isolator of the above-described first embodiment in other respects.

The optical element composed of the half-wave plates 3a and 3b and the magnetic garnets 9a and 9b used in the optical isolator of the second embodiment is manufactured in the form of being vertically divided into two equal parts. First, a magnetic garnet 9 which is a rectangular Faraday rotator and a half-wave plate 3 of the same shape are attached to each other, cut into two or more pieces, and then two of them, that is, magnetic garnets 9a, 9
b and the half-wave plates 3a and 3b are taken out and combined. It is desirable that the magnetic garnets 9a and 9b and the half-wave plates 3a and 3b are elements cut out from the same block.
The thicknesses of the half-wave plates 3a and 3b are equal, and the Faraday rotation angle and the direction of the optical axis of the half-wave plate are also equal to each other. In addition, since it is an array type optical isolator, it is desirable that the shape of the element cut out and combined is an elongated rectangle.

By using such an optical element,
The step at the connection point between the two optical elements can be made almost zero. One of the causes of scattering and refraction of the light transmitted through the connection point is the presence of the step. By eliminating the step, optical characteristics such as insertion loss and isolation of the optical isolator can be improved. . As in the case of the first embodiment described above, the communication wavelength band 1..
Assuming a transmitted light of 55 μm, the magnetic garnet 9
The thickness of each of the optical elements at the central portion is approximately 90 μm when the half-wave plates 3 a and 3 b are made of quartz. In this embodiment, the thickness is about 600 μm, which is slightly shorter than that of the above-described embodiment by 100 μm. In the upper and lower two-stage optical elements, the optical axes of the half-wave plates 3a and 3b are required to have an angle of 45 ° or 135 °. In the case where the optical axes are formed from the same optical element block, the optical axis is oriented symmetrically with respect to the plane of the connection point.
22.5 ° or ± 67.5 ° (= ± 22.5 ° + ± 4
5 ゜).

Next, a method of assembling the array-type optical isolators of the first and second embodiments configured as described above will be described. First, a plurality of waveguide structures are formed in parallel on a substrate 7 made of glass, Si, or the like.
Then, a part of each waveguide is enlarged by a method such as a heat treatment, and T
The optical waveguide has an EC structure. Then, the central portion of each enlarged optical waveguide is dug down in a groove shape to cut the optical waveguide having the TEC structure, and the magnetic garnet 5 as the Faraday rotator and the half-wave plate 3 are cut into the groove.
An elongated optical element combining a and 3b is provided, finely adjusted and fixed.

In this method, optical adjustment cannot be performed by moving the optical waveguides 1a and 1b having the TEC structure on both sides, but the optical waveguide 1 having the TEC structure on both sides cannot be adjusted.
Since a and 1b are always installed at opposing positions, T
When manufacturing the optical waveguides 1a and 1b having the EC structure, attention should be paid so that a sufficient coupling efficiency can be obtained.
Optical adjustment for moving a and 1b between each other is not particularly necessary. Thus, the array-type optical isolator of the present embodiment can be efficiently manufactured.

FIGS. 3A and 3B are a top view and a vertical sectional view, respectively, showing the configuration of an optical isolator according to a third embodiment of the present invention. The optical isolator according to the third embodiment shown in FIG. 11 has lens units 11c and 11d integrated with the optical isolator according to the first embodiment shown in FIG. 1 instead of the optical waveguides 1a and 1b having the TEC structure. Waveguides 11a and 11b with a spherical lens formed in
Is used, and other configurations, operations, and effects are the same as those of the optical isolator of the first embodiment.

Optical waveguides 11a and 11b with spherical lenses
Are several tens to several hundreds in diameter at the tip of the core of the optical fiber.
It has a structure in which the μm spherical lens portions 11c and 11d are bonded or fused, and with appropriate design, the emitted light can be made into parallel light.

FIGS. 4A and 4B are a top view and a vertical sectional view, respectively, showing the structure of an optical isolator according to a fourth embodiment of the present invention. The optical isolator according to the fourth embodiment shown in FIG. 9 is different from the optical isolator shown in FIG. 3 in that the magnetic garnet 5 constituting the Faraday rotator is divided into upper and lower parts, and the first and second magnetic garnets 9a, 9
2B, and is configured like the magnetic garnets 9a and 9b of the second embodiment shown in FIG. 2, and other configurations, operations, and effects are the same as those of the first to third embodiments described above. It is the same as the form of the optical isolator.

Next, a method for assembling the array type optical isolators of the third and fourth embodiments configured as described above will be described. In the present embodiment, the optical waveguides 11a and 11b with a spherical lens after the groove processing of the substrate 7 is performed.
Since it is difficult to manufacture the optical isolator of the first and second embodiments, it is not practical. Therefore, in the case of the optical isolator using the optical waveguides 11a and 11b with the spherical lenses as in the third and fourth embodiments, a plurality of parallel V-shaped grooves are formed on the substrate 7 and these are formed. A method may be considered in which a groove for an optical element is formed in a direction orthogonal to the groove, and an elongated optical element is provided therein. In this case, optical adjustment is required for each optical isolator component. Optical waveguides 11a, 11 with a spherical lens with relatively excellent optical coupling efficiency
Although the method of manufacturing an optical isolator using b has a problem in terms of ease of assembly, it is considered to be advantageous in terms of optical characteristics of the optical isolator.

FIGS. 5A and 5B are a top view and a longitudinal sectional view, respectively, showing the structure of an optical isolator according to a fifth embodiment of the present invention. The optical isolator according to the fifth embodiment shown in FIG. 7 has first and second optical couplers 13a and 13b provided in the optical waveguides 1a and 1b, respectively, in the optical isolator according to the first embodiment shown in FIG. Are significantly different from each other, and these optical couplers 13a,
A plurality of pairs of optical waveguides 1a ′ and 1a ″ each having a TEC structure are provided between the branch output terminal 13b and the optical element including the magnetic garnet 5 and the half-wave plates 3a and 3b.
b ', 1b ", and lens portions 1c', 1c": 1d ',
1d "is formed.

In the array-type optical isolator thus configured, the transmitted light in the forward direction from the plurality of optical waveguides 1a is divided into two light beams having the same intensity, phase and degree of polarization by the first optical coupler 13a. The first and second light beams are independently converted into parallel light beams at the lens portions 1c 'and 1c "via a plurality of pairs of optical waveguides 1a' and 1a" each having a TEC structure. The light of 1 is 1 /
The two-wavelength plate 3a passes through the magnetic garnet 5 constituting the Faraday rotator, and the second light is transmitted through the magnetic garnet 5, 1
/ 2 wavelength plate 3b. Then, further, the first and second lights are respectively provided with a plurality of pairs of lens portions 1d ', 1d.
d ", passing through a plurality of pairs of optical waveguides 1b 'and 1b"
Of the second optical coupler / demultiplexer 13b.
The first and second lights are combined and emitted from the plurality of optical waveguides 1b. Also, the transmitted light in the opposite direction from the plurality of optical waveguides 1b is split by the second optical coupler / splitter 13b, and the split first and second lights are transmitted through the plurality of pairs of optical waveguides 1b 'and 1b ". Lever part 1d ', 1
d ″ becomes parallel light, and the first light is magnetic garnets 5, 1
/ 2 wavelength plate 3a, one of lens portions 1c ', optical waveguide 1
a ', and reaches the first optical splitter 13a. The second light is a half-wave plate 3b, a magnetic garnet 5, and a lens unit 1.
c ", through the optical waveguide 1a" and through the first optical coupler 13
As a result, the first light and the first light cancel each other out and cannot be transmitted.

In the optical isolator of the fifth embodiment shown in FIG. 5, the optical waveguides 1a 'and 1
a ″ and the optical waveguides 1b ′ and 1b ″,
Instead, an optical waveguide with a spherical lens and other components may be used.

FIGS. 6A and 6B are a top view and a vertical sectional view, respectively, showing the structure of an optical isolator according to a sixth embodiment of the present invention. The optical isolator according to the sixth embodiment shown in the same drawing is different from the optical isolator according to the fifth embodiment shown in FIG. 5 in that the Faraday rotator is shown in FIGS. 2 and 4 instead of the integrated magnetic garnet 5. The difference is that the magnetic garnets 9a and 9b divided into two parts are used as described above, and other configurations, operations and effects are the same.

An advantage of the optical isolators according to the fifth and sixth embodiments is that the two separated light beams having passed through the optical multiplexer / demultiplexer are independently guided to the optical elements. Light passing through the vicinity of the surface at the connection point becomes substantially zero, and the influence of reflection and scattering caused by the presence of this surface can be almost completely eliminated. Therefore, it is possible to configure an optical isolator that is more excellent in optical characteristics than the above-described embodiments. In this case, in each region having an independent optical isolator configuration, the optical waveguides 1a, 1a ', 1a ", 1b, 1 having two TEC structures are provided.
It is necessary to precisely control the optical path length of each separated light including b 'and 1b ". This can be performed by optically adjusting the distance between the end faces of the optical waveguides having the TEC structure during assembly. However, compared to the embodiments shown in FIGS.
It is inevitable that the total length of the optical isolator is slightly increased due to the presence of the two optical couplers 13a and 13b and the optical waveguide having the TEC structure in each region. However, for example, an optical waveguide is formed on a glass substrate by PLC (Planar Lightwave).
If the configuration is made as an optical waveguide having a (Circuit) structure, and the function of the optical coupler is given to the PLC structure, the size can be reduced.

Further, in the fifth and sixth embodiments, the transmitted light is two kinds of independent separated lights separated from each other by the optical couplers 13a and 13b. It is not necessary to consider the reflection and scattering caused by light. With this structure, an optical isolator having better optical characteristics than the embodiment of FIGS. 1 to 4 can be constructed, but four optical waveguides 1a ', 1a ", 1b', 1 for each transmitted light.
b "and two optical couplers 13a and 13b, the configuration becomes slightly larger. In addition, it is necessary to sufficiently manage the entire length of the optical waveguide and the junction area so that the optical path length difference of the two separated lights does not occur. In order to prevent the optical path length difference from occurring, a PLC in which an optical waveguide is formed on a substrate such as glass is used.
A method using a (Planar Lightwave Circuit) structure or a method of fixing and processing an optical fiber on a glass substrate, a Si substrate, or the like is effective. In addition, as a method of embodying this method, when an optical waveguide having a PLC structure performs the function of the optical coupler, instead of installing the optical waveguide at the center of the Faraday rotator and the half-wave plate, Set up slightly shifted.

FIGS. 7A and 7B are a perspective view and a longitudinal sectional view, respectively, showing the structure of an optical isolator according to a seventh embodiment of the present invention. The optical isolator according to the embodiment shown in the figure has a configuration in which an optical waveguide having a PLC structure is formed on a glass substrate as described above, and the function of an optical coupler is achieved by the optical waveguide. In FIG. 7, 3a and 3b and 9a and 9b respectively correspond to 1
A magnetic garnet constituting a half-wave plate and a Faraday rotator, and 15a and 15b are optical waveguides having a PLC structure. Reference numeral 7 denotes a substrate.

In the optical isolator thus configured, the forward transmitted light entering from the left side optical waveguide 15a having the PLC structure is split into two lights in the PLC structure region, and each of them is independent of the magnetic garnet 9a, 9a. The light passes through the 9b and the half-wave plates 3a and 3b, enters the right optical waveguide 15b having a PLC structure, is synthesized by the PLC structure, and emerges from the optical waveguide 15b. And
When the transmitted light is separated by the PLC structure of the left optical waveguide 15a, the phases thereof are shifted by 90 °, but this is the same phase when re-combined by the PLC structure of the right optical waveguide 15b. The offset cancels out and does not affect the result.

The transmitted light in the opposite direction, which is incident from the right optical waveguide 15b, is synthesized by the PLC structure of the optical waveguide 15b, separated into two lights, and is independently independent of the magnetic garnets 9a, 9b and 1/2 wavelength. The light passes through the plates 3a and 3b, enters the optical waveguide 15b having the left PLC structure, is canceled by each other when recombined in the PLC structure, and cannot pass through the inside of the array type optical isolator.

In the embodiment shown in FIG. 7, the magnetic garnets 9a and 9b constituting the Faraday rotator are formed of two-part elements, but instead of FIGS. 1, 3 and 5, A magnetic garnet, which is an integrated Faraday rotator as shown in FIG.

In both optical waveguides 15a and 15b on the substrate 7, the transmitted light is linearly incident on the half-wave plate side in the optical isolator of FIG.
9b (Faraday rotator) is incident so as to wrap around. By appropriately designing the shape and area of the optical waveguide, incident light can be divided into two separated lights having the same light intensity, and can be separately incident on the half-wave plate and the magnetic garnet. . However, the phase of the separated light on the magnetic garnet side is delayed by 90 °. By forming such an optical waveguide on a substrate, the optical coupler of the present embodiment can be easily formed.

FIGS. 8A and 8B are a top view and a longitudinal sectional view, respectively, showing the structure of an optical isolator according to an eighth embodiment of the present invention. The optical isolator according to the eighth embodiment shown in FIG. 11 is an optical element comprising magnetic garnets 9a and 9b, which are Faraday rotators, and half-wave plates 3a and 3b in the optical isolator according to the second embodiment shown in FIG. The light transmission surface of the optical element is arranged so as to be inclined from the vertical plane with respect to the transmitted light, thereby preventing deterioration of optical characteristics due to light reflection on the surface of the optical element. Is the same as the optical isolator of the second embodiment shown in FIG.

FIGS. 9A and 9B are a top view and a vertical sectional view, respectively, showing the structure of an optical isolator according to a ninth embodiment of the present invention. The optical isolator according to the ninth embodiment shown in FIG. 14 is an optical element comprising magnetic garnets 9a and 9b, which are Faraday rotators, and half-wave plates 3a and 3b in the optical isolator according to the fourth embodiment shown in FIG. The light transmitting surface of the optical device is disposed so as to be inclined from the vertical surface with respect to the transmitted light. This is different from the optical isolator according to the fourth embodiment shown in FIG. 4 in that the configuration, operation and effect are the same.

As in the eighth and ninth embodiments, the optical element composed of the magnetic garnets 9a, 9b and the half-wave plates 3a, 3b is disposed at an angle, so that the reflected light on the surface of the optical element can be obtained. Can be prevented from reentering the optical waveguide as return light. It is necessary to tilt the optical element in a direction obliquely viewed in the top view. On the other hand, if the direction of inclination is defined as a direction obliquely viewed in the vertical cross-sectional view of each embodiment (the direction of tilt in FIGS. 8 and 9), the upper and lower joining portions of the optical element in the transmitted light in the forward and reverse directions are determined. Since the ratio of transmitted light increases, it causes deterioration of the optical characteristics of the optical isolator. Therefore, it is necessary to avoid tilting the optical element in this direction. In the case of an optical device using a Faraday rotator and a half-wave plate, the inclination angle is often 4 ° to 8 °.

In the optical isolators of the eighth and ninth embodiments, an oblique groove is formed in the substrate 7, and the magnetic garnets 9a and 9b and the half-wave plates 3a and 3b are formed in the oblique groove.
It is produced by disposing an optical element consisting of

In the eighth and ninth embodiments, the case where the optical waveguides 11a, 11b with the spherical lenses and the magnetic garnets 9a, 9b are used has been described. The integrated magnetic garnet 5 and the optical waveguides 1a and 1b having the TEC structure may be used.

In each of the above-described embodiments, the means for applying a magnetic field to the magnetic garnet, which is a Faraday rotator, is omitted in the drawing for simplification of the drawing.

[0056]

As described above, according to the present invention,
First and second plurality of optical waveguides each having a lens portion formed at one end are disposed in parallel so that the respective lens portions face each other, and a Faraday rotator and a half-wave plate are provided between the facing lens portions. Since an optical element consisting of is arranged to constitute an array-type optical isolator, the optical waveguide and the lens unit can be optically adjusted in advance and integrated, and the transmitted light between the lens units is always parallel light or close thereto. The optical characteristics of the optical isolator can be improved, and the optical adjustment between the optical waveguide and the lens portion is not required at the time of assembling, so that the adjustment after assembling becomes easy. In addition, a structure for separately holding the lens unit is not required, so that the size can be reduced, and the size of the optical element can be reduced, so that economy and improvement in optical characteristics can be achieved.

According to the present invention, a plurality of first and second pairs of optical waveguides each having a lens portion formed at one end are arranged in parallel so that the respective lens portions face each other. In addition to disposing an optical element comprising a Faraday rotator and a half-wave plate between the portions, a light combining / branching means is provided in the middle of each of the first and second plurality of optical waveguides, thereby branching and combining light. Since the transmitted light is separated and separated separately from each other by the light combining / branching means, there is no need to consider reflection and scattering due to the step structure at the end of the optical element, and the array has excellent optical characteristics. Type optical isolators can be configured.

Further, according to the present invention, the first and second plurality of optical waveguides having the PLC structure are arranged in parallel so as to face each other, and the Faraday rotator and the 1 / Since an optical element composed of a two-wavelength plate is provided, it is possible to branch and combine transmitted light with a PLC structure without providing an independent light combining / branching means, which enables downsizing and excellent optical characteristics. An array-type optical isolator can be configured.

According to the present invention, since the light transmitting surfaces of the Faraday rotator and the first and second half-wave plates are disposed obliquely from the surface perpendicular to the transmitted light, the optical element Can be prevented from returning to the optical waveguide and returning to the optical waveguide, and the effect of the reflected light on the surface of the optical element can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are a top view and a vertical sectional view showing a configuration of an optical isolator according to a first embodiment of the present invention.

FIGS. 2A and 2B are a top view and a vertical sectional view showing a configuration of an optical isolator according to a second embodiment of the present invention.

FIGS. 3A and 3B are a top view and a vertical sectional view illustrating a configuration of an optical isolator according to a third embodiment of the present invention.

FIGS. 4A and 4B are a top view and a vertical sectional view showing a configuration of an optical isolator according to a fourth embodiment of the present invention.

FIGS. 5A and 5B are a top view and a vertical sectional view showing a configuration of an optical isolator according to a fifth embodiment of the present invention.

FIGS. 6A and 6B are a top view and a vertical sectional view illustrating a configuration of an optical isolator according to a sixth embodiment of the present invention.

FIGS. 7A and 7B are a perspective view and a longitudinal sectional view showing a configuration of an optical isolator according to a seventh embodiment of the present invention.

FIG. 8 is a top view and a longitudinal sectional view showing a configuration of an optical isolator according to an eighth embodiment of the present invention.

FIGS. 9A and 9B are a top view and a vertical sectional view showing a configuration of an optical isolator according to a ninth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a conventional optical isolator.

[Explanation of symbols]

 1a, 1b Optical waveguide having TEC structure 1c, 1d, 11c, 11d Lens portion 3a, 3b 1/2 wavelength plate 5, 9a, 9b Magnetic garnet (Faraday rotator) 7 Substrate 11a, 11b Optical waveguide with forward lens 13a , 13b Optical multiplexer / demultiplexer 15a, 15b Optical waveguide having PLC structure

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Akiyuki Kan, Nippon Telegraph and Telephone Corporation 3-2-1, Nishishinjuku, Shinjuku-ku, Tokyo Japan (72) Naoto Sugimoto 3-19, Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Nippon Telegraph and Telephone Corporation (72) Inventor Masayuki Kimura 6-7-1, Koriyama, Taishiro-ku, Sendai City, Miyagi Prefecture Tokin Co., Ltd. (72) Takuya Kawamura 6-7, Koriyama, Tashiro-ku, Sendai City, Miyagi Prefecture No. 1 Tokin Co., Ltd. (72) Inventor Haruhiko Tsuchiya 6-7-1, Koriyama, Taishiro-ku, Sendai, Miyagi Prefecture Tokin Co., Ltd.

Claims (6)

[Claims] 1. A lens unit formed at one end of each of the first plurality of optical waveguides disposed in parallel with each other, and a lens unit facing each of the lens units of the first plurality of optical waveguides. Formed at one end of each of the plurality of optical waveguides and disposed in parallel with each other, and a Faraday rotator disposed between lens portions of the first and second plurality of optical waveguides. A first light beam from each lens portion of the first plurality of optical waveguides;
Of the Faraday rotator facing the lens portion of the first plurality of optical waveguides so that half of the light is transmitted and the second half of the light is transmitted directly through the Faraday rotator. A first half-wave plate joined to one half of the Faraday rotator; a first half-wave plate joined to a second half of a second surface opposite to the first surface of the Faraday rotator; The second half light from the second half side of the second surface is transmitted and incident on the lens portions of the second plurality of optical waveguides;
A second half-wave plate that directly receives the first half light from the Faraday rotator into a lens portion of the second plurality of optical waveguides; and a magnetic field application that applies a magnetic field to the Faraday rotator. And an optical isolator. 2. A first plurality of optical waveguides arranged in parallel, and one end of each of the first plurality of optical waveguides is connected to one end of each of the first plurality of optical waveguides, and light is incident from one side of each of the first plurality of optical waveguides. A first plurality of light combining / branching units each of which splits light into two and emits light from the other side of each pair, combines light incident from the other side of each pair and emits the light from one side of each pair Means, and a respective pair on the other side of each pair of the first plurality of light combining / branching means for separately guiding the first and second lights respectively branched by the first plurality of light combining / branching means. Are connected to each other, and a pair of lens portions are formed at the other end of each pair, respectively, and at the other end of each pair of the first plurality of pairs of optical waveguides. Each of the paired lens portions formed is opposed to each other. A pair of lens portions are formed at one end of each pair, and a second plurality of pairs of optical waveguides are provided in parallel; and a second pair of optical waveguides are formed at the other end of each pair of the second plurality of optical waveguides. One side of each pair is connected to combine light incident on one side of each pair from the other end of each pair of the second plurality of optical waveguides, and from each other side. Outgoing and incident light from each other side
Split into two and exit from one side of each pair
A plurality of optical coupling / branching means; a second plurality of optical waveguides connected to the other side of the second plurality of optical coupling / branching means and arranged in parallel; The first plurality of pairs of optical waveguides are disposed between each pair of lens portions, and light from each one of the paired lens portions of the first plurality of optical waveguides is directly incident on one side; A Faraday rotator on which light from one lens unit of each pair of lens units of the second plurality of pairs of optical waveguides is directly incident on the other side; one surface of the Faraday rotator and the first surface; A first half-wave plate disposed between each pair of lens portions of the plurality of pairs of optical waveguides, and the other surface of the Faraday rotator and the second half-wave plate. Disposed between each pair of lens portions of the plurality of optical waveguides and the other lens portion. An optical isolator comprising: a second half-wave plate; and a magnetic field applying means for applying a magnetic field to the Faraday rotator. 3. The optical waveguide according to claim 1, wherein said first and second plurality of optical waveguides and said first and second plurality of pairs of optical waveguides are optical waveguides having a TEC structure having an enlarged portion as said lens portion. The optical isolator according to claim 1 or 2, wherein: 4. The method according to claim 1, wherein the first and second pluralities of optical waveguides and the first and second pluralities of pairs of optical waveguides are optical waveguides with a spherical lens having a spherical lens as the lens portion. The optical isolator according to claim 1 or 2, wherein: 5. A first plurality of optical waveguides having a PLC structure disposed in parallel, and one end of each of the first plurality of optical waveguides is disposed in parallel with one end of each of the first plurality of optical waveguides. A second plurality of optical waveguides having a PCL structure; a Faraday rotator disposed between opposing ends of the first and second plurality of optical waveguides; The Faraday rotator opposing one end of each of the first plurality of optical waveguides such that a first half of light from each one end is transmitted and a second half of light is transmitted directly through the Faraday rotator. A first half-wave plate joined to a first half of the first surface of the child, and a second half of a second surface of the Faraday rotator opposite the first surface. And a second half of the second face of the Faraday rotator from the second half side. Minute light is transmitted and is incident on the second plurality of optical waveguides, and the first half light from the Faraday rotator is directly incident on the second plurality of optical waveguides. An optical isolator comprising: a half-wave plate; and a magnetic field applying unit that applies a magnetic field to the Faraday rotator. 6. The light transmission surface of the Faraday rotator and the first and second half-wave plates are disposed so as to be inclined from a plane perpendicular to the transmitted light. Item 6. The optical isolator according to any one of Items 1 to 5.