JPH07113986A - Method for assembling optical isolator and method for measuring isolation - Google Patents

Abstract

PURPOSE:To provide the method capable of assembling an optical isolator body while adjusting the isolation of the optical isolator and the method for measuring the optical isolator capable of determining the isolation during the course of assembly of the optical isolator body. CONSTITUTION:A step for constituting a measuring system which is arranged with a light source 7, a lens system 6, a polarizer 2, an analyzer 4 and a photodetector 5 in this order and receives the light emitted from this light source 7 and passes through the lens system 6, the polarizer 2 and the analyzer 4 with the photodetector 5, a step for arranging the optical isolator body 1 between the polarizer 2 and the analyzer 4, a step for measuring the max. value and min. value of the light receiving level of the photodetector 5 and determining the ratio to the min. value and the max. value and a step for adjusting the rotating positions of respective parts constituting the optical isolator body 1 so as to minimize the ratio are executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling an optical isolator and a method for measuring the isolation, in which isolation can be easily checked at the stage of assembling an optical isolator body used for optical fiber communication or the like.

[0002]

2. Description of the Related Art FIG. 8 is a schematic view showing the structure and function of an example of an optical isolator main body. As shown in FIG. 8, the optical isolator main body 1 includes a birefringent crystal plate 11, a half-wave plate 12, a magneto-optical crystal plate 13 having a Faraday effect,
The birefringent crystal plate 14 and the magnet 15 are provided. The birefringent crystal plate 11, the half-wave plate 12, the magneto-optical crystal plate 13 and the birefringent crystal plate 14 are sequentially arranged along the light guiding direction, and the magnet 15 magnetizes the magneto-optical crystal plate 13. It is located in. Here, the birefringent crystal plate 11 is arranged with its crystal optical axis inclined with respect to the light guiding direction, and the incident light 10 incident on the birefringent crystal 11 has oscillating planes perpendicular to each other. It is separated into two rays (ordinary ray and extraordinary ray). In the birefringent crystal plate 11, the ordinary ray travels straight, while the extraordinary ray travels obliquely, but after exiting the birefringent crystal plate 11, they travel straight as parallel rays along the propagation direction. The half-wave plate 12 is tilted in the counterclockwise direction by 67.5 degrees from the direction in which the crystal optical axis of the birefringent crystal plate 11 is projected onto the surface (hereinafter referred to as the projection direction), toward the traveling direction of light. Has a crystal axis in the
The ordinary ray and the extraordinary ray emitted from the birefringent crystal plate 11 are −22.5 and 6 from the crystal axis of the half-wave plate 12, respectively.
It is tilted 7.5 degrees. Therefore, by passing through the half-wave plate 12, the ordinary ray rotates 45 degrees clockwise in the traveling direction of the light and the extraordinary ray rotates counterclockwise by 13 degrees.
Rotate 5 degrees. As a result, the polarization directions of these lights are apparently rotated 45 degrees clockwise. Further, the magneto-optical crystal plate 13 has a Faraday effect, and the polarization direction of the light beam that has passed through this crystal plate is rotated by 45 degrees. The birefringent crystal plate 14 has a function similar to that of the birefringent crystal plate 11 and is arranged such that its crystal optical axis is in the same direction as that of the birefringent crystal plate 11.

In the above structure, in order to avoid returning light reflected by the optical isolator itself, the incident light rays and the surface of each element are arranged with a certain inclination so that they are not perpendicular to each other.

Next, the operation of the optical isolator body 1 will be described.

The unpolarized light 10 incident from the left side is separated into lights (ordinary rays and extraordinary rays) having mutually perpendicular polarization planes in the crystal of the birefringent crystal plate 11. Each light is 1
The polarization planes apparently rotate 45 degrees clockwise in the / 2 wavelength plate 12, and further, the polarization planes rotate 45 degrees clockwise by the magneto-optical crystal plate 13. Therefore, the ordinary ray and the extraordinary ray emitted from the birefringent crystal plate 11 are incident on the birefringent crystal plate 14 with their polarization planes rotated by 90 degrees. Here, since the birefringent crystal plate 14 is arranged such that its crystal optical axis is in the same direction as that of the birefringent crystal plate 11, the ordinary ray and the extraordinary ray of the birefringent crystal plate 11 are respectively It is incident on the birefringent crystal plate 14 as an extraordinary ray and an ordinary ray. Then, of these two lights, the extraordinary ray advances obliquely and the two lights are combined again and emitted.

Next, let us consider the light incident from the right side.
The incident ray 10 ′ is separated by the birefringent crystal plate 14 into two rays having a plane of polarization perpendicular to each other (a straight ray advancing ordinary ray and an obliquely advancing extraordinary ray). The two light rays are incident on the magneto-optical crystal plate 13, and the polarization planes of the respective lights are rotated 45 degrees counterclockwise in the traveling direction due to the non-reciprocity of the magneto-optical crystal plate 13. Further two rays pass through the half-wave plate 12. At this time, the polarization planes of the respective lights are apparently 4 clockwise in the traveling direction.
Since the light is rotated by 5 degrees, the polarization of the two lights will be
It returns to the state when it passed. Therefore, the birefringent crystal plate 1
The ordinary ray and the extraordinary ray of the birefringent crystal plate 14 reaching 1 enter the birefringent crystal sheet 11 as the ordinary ray and the extraordinary ray, respectively. Emit to different positions.

In this way, the optical isolator of FIG. 8 has an incident position of non-polarized light which is incident from the left side and an outgoing position of non-polarized light which is reverse to the optical path and is incident from the right side. Can be completely separated.

In such an optical isolator main body, it is necessary to accurately adjust the position of the element and the crystal axis. Above all, the positioning of the half-wave plate is delicate because the crystal axis of the half-wave plate must be fixed in a predetermined direction. Furthermore, since forward loss, return loss, and isolation must all be satisfied at the same time, it is necessary to confirm their characteristics at the stage of assembling these optical isolators.

Isolation is represented by the ratio of the power levels of light traveling in the opposite direction through the optical isolator before and after passing through the isolator. Therefore, conventionally, it was not possible to check at the stage of assembling the optical isolator body. Then, conventionally, as shown in FIG. 9, the main body 1 is fixed in the housing 16, and the optical fibers 18 are attached to both sides of the housing 16 via the collimating lenses 17, and then the measurement is performed.

Further, since the isolation is greatly affected by a slight deviation of the optical axis, the collimating lens 17 is arranged before and after the isolator main body 1 so that the optical axes are correctly aligned when measuring the isolation. There must be. However, it is not easy to accurately adjust the optical axis in this way, and there is also a problem that the operation requires a long time.

The object of the present invention is to solve these problems.
An object of the present invention is to provide a method capable of assembling an optical isolator main body while adjusting the isolation of the optical isolator, and an isolation measuring method capable of obtaining the isolation during the assembling of the optical isolator main body.

[0012]

According to a first aspect of the present invention for achieving the above object, a light source, a lens system, a polarizer, an analyzer and a light receiver are arranged in this order, and the light is emitted from the light source.
Step of configuring a measurement system in which the light receiver receives the light transmitted through the lens system, the polarizer, and the analyzer; arranging components forming an optical isolator main body between the polarizer and the analyzer Measuring the maximum value and the minimum value of the light receiving level of the light receiver when the analyzer is rotated, and obtaining the ratio of the minimum value to the maximum value; and so that the ratio becomes minimum. And a step of adjusting the rotational positions of the respective parts constituting the optical isolator main body, and the assembling method of the optical isolator.

A second aspect of the present invention is a light source, a lens system,
Steps of arranging a polarizer, an analyzer and a light receiver in this order, and forming a measurement system in which the light emitted from the light source and transmitted through the lens system, the polarizer and the analyzer are received by the light receiver Arranging components forming the optical isolator body between the polarizer and the analyzer;
Measuring, for each rotational position of the component, a maximum value and a minimum value of a light receiving level of the light receiver when the analyzer is rotated; and a ratio of the minimum value to the maximum value is a minimum. And a step of adjusting the position of the component to the rotational position of the component.

According to a third aspect of the present invention, in the first or second aspect, the measurement of the maximum value and the minimum value and the rotational position adjustment based on this measurement are performed for each component of the optical isolator main body. It is a method of assembling a characteristic optical isolator.

According to a fourth aspect of the present invention, in the first or second aspect, the measurement of the maximum value and the minimum value, and the rotational position adjustment by this measurement are performed for each component of the optical isolator main body. This is a method of assembling an optical isolator, which is characterized by repeating this a plurality of times.

According to a fifth aspect of the present invention, in the first to fourth aspects, a ½ wavelength plate is arranged immediately after the polarizer,
In the method of assembling the optical isolator, the position of the polarizer with respect to the main body of the optical isolator in the rotational direction is aligned by rotating the half-wave plate.

A sixth aspect of the present invention is the method for assembling an optical isolator according to any one of the first to fourth aspects, characterized in that a quarter wavelength plate is arranged immediately before the polarizer.

A seventh aspect of the present invention is a light source, a lens system,
Steps of arranging a polarizer, an analyzer and a light receiver in this order, and forming a measurement system in which the light emitted from the light source and transmitted through the lens system, the polarizer and the analyzer are received by the light receiver Arranging an optical isolator body between the polarizer and the analyzer; measuring a maximum value and a minimum value of a light receiving level of the light receiver when the analyzer is rotated; and the minimum value And a step of setting a value expressed in decibels of the ratio of the above to the maximum value as an isolation;

According to an eighth aspect of the present invention, in the seventh aspect, a half-wave plate is arranged immediately after the polarizer, and the alignment of the polarizer with respect to the optical isolator main body in the rotation direction is performed. This is a method for measuring isolation, which is characterized by performing rotation of a half-wave plate.

A ninth aspect of the present invention is the isolation measuring method according to the seventh aspect, characterized in that a quarter wavelength plate is arranged immediately before the polarizer.

In the assembling method of the present invention, the light source, the lens system,
A measurement system having a polarizer, an analyzer and a light receiver is configured,
Arrange the components that make up the optical isolator body between the polarizer and the analyzer, and configure the optical isolator so that the ratio of the minimum and maximum values of the light receiving level of the light receiver when the analyzer is rotated is minimized. It suffices to adjust the rotational position of the component. This makes it possible to assemble an optical isolator having the best isolation characteristics. Specifically, the analyzer is rotated for each rotational position of each component to measure the minimum and maximum values of the received light level, and the component is set to the rotational position that minimizes the ratio of the minimum value to the maximum value. Good. It is efficient to perform these rotational positions in order for each part. Further, better isolation characteristics can be obtained by repeating the adjustment for each part a plurality of times.

When the ratio of the above-mentioned minimum value to the maximum value is expressed in decibels, isolation is achieved, and the final value of the optical isolator can be measured at the assembly stage. After adjusting the isolation of the isolator body in this way, it can be incorporated into the housing,
The assembly and adjustment of the entire optical isolator can be performed accurately and in a short time.

The method of the present invention as described above is also characterized in that it is not necessary to perform precise axis alignment because no lens is used in front of the light receiver for the measurement, and the measurement can be easily performed. Furthermore, in carrying out the method of the present invention, a half-wave plate is inserted immediately after the polarizer, or a half-wave plate is inserted immediately before the polarizer.
By inserting the / 4 wavelength plate, the measurement can be further simplified as described later.

Therefore, by applying the measuring method of the present invention, the alignment of the components can be adjusted while measuring the isolation of the optical isolator body.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

First, the measurement principle of the present invention will be described with reference to FIG. Here, the configuration of the optical isolator main body 1 is the same as the configuration shown in FIG. 8, and duplicated description will be omitted. An explanation of the function of the optical isolator main body 1 is shown in FIG. In FIG. 1, each element is shown in a front view seen from the forward incidence side, and the arrow in each element shows the crystal axis when seen from the forward incidence direction. The direction of rotation of the plane of polarization is represented as clockwise or counterclockwise with respect to the light traveling direction.

As shown in FIG. 1, unpolarized incident light 10 incident in the forward direction is separated by a birefringent crystal plate 11 into two linearly polarized lights (ordinary rays and extraordinary rays) whose polarization planes are orthogonal to each other. To do. These two rays are then 1 /
As a result, the polarization planes of the two-wave plate 12 are apparently rotated by 45 ° in the clockwise direction. Further, the planes of polarization of these rays are rotated by 45 ° clockwise in the magneto-optical crystal plate 13. Therefore, in the two light rays emitted from the magneto-optical plate 13, the ordinary ray and the extraordinary ray in the birefringent crystal plate 11 become the extraordinary ray and the ordinary ray in the birefringent crystal plate 14, which are Is synthesized.

On the other hand, the unpolarized light beam 1 which is incident in the opposite direction
0'is separated by the birefringent crystal plate 14 into two linearly polarized lights (ordinary rays and extraordinary rays) whose polarization planes are orthogonal to each other. These rays are then, at the magneto-optic crystal plate 13,
The plane of polarization is rotated counterclockwise by 45 ° in the direction of travel, and the passage of the half-wave plate 12 causes the plane of polarization to eventually appear to be rotated clockwise by 45 °. Become. Therefore, 2 that exited the half-wave plate 12
As for the two rays, the ordinary ray and the extraordinary ray at the birefringent crystal plate 14 become the ordinary ray and the extraordinary ray at the birefringent crystal plate 11 as they are, are not synthesized by the birefringent crystal plate 11, and are deviated from the forward incident position. It is emitted to the position.

Here, the emitted light when entering in the forward direction is only the non-polarized light ray 10-1 when the respective elements are ideally arranged. However, when the crystal axes of any of the elements deviate from the ideal direction, side spots 10-2 and 10-3 appear. On the other hand, when the respective elements are ideally arranged, the emitted lights when they are incident in the opposite directions are only the emitted lights 10'-1 and 10'-2. However, if the crystal axis of any of the elements deviates from the ideal direction, the side spot 10'-3 appears at the forward incident position.

Normally, the birefringent crystal plates 11 and 14 have a thickness of about 1 mm, whereas the half-wave plate 13 has a small thickness of 0.1 mm, which is difficult to handle. That is, it is difficult to control the positioning of the half-wave plate 12 during assembly. Therefore, it is the direction of the crystal axis of the half-wave plate 12 that is most easily displaced when positioning each element. The thickness of the magneto-optical crystal plate 13 is usually about 0.4 mm, which is relatively difficult to handle, but the direction of the crystal axis of the magneto-optical crystal plate 13 does not affect the property of rotating the polarization plane.

Therefore, the crystal axis of the half-wave plate 12 is Δθ from the set direction θ ₀ (direction inclined by 67.5 ° from the direction in which the crystal axes of the birefringent crystal plates 11 and 14 are projected on the surface).
Consider the case where they are just off. As shown in FIG. 2 (A), the linearly polarized light 10a (which vibrates in the x-axis direction in the figure) that is incident in the forward direction from the left passes through the half-wave plate 12 and the magneto-optical crystal plate 13. The plane of polarization is rotated by 90 degrees and emitted as emitted light 10b. At this time, if the crystal axis of the half-wave plate 12 is deviated from the set value by Δθ, the polarization direction of the outgoing light is 90 degrees rotated from the state at the time of incidence, and the polarization direction of the polarization plane is the incidence plane. A side spot 10c that is identical to

Here, the linearly polarized light 10a in the x-axis direction is expressed by the following equation (1) when the intensity is 1.

[0033]

[Equation 1]

The angle θ between the plane of polarization of the emitted light 10b and the x-axis is the angle of rotation of the plane of polarization of the half-wave plate 12,
It can be represented by the sum of the rotation angle of the plane of polarization of the magneto-optical crystal plate 13, and is represented by the following equation (2).

[0035]

## EQU00002 ## .theta. =-2 (22.5 + .DELTA..theta.)-45 = -90-2..DELTA..theta. (2) Therefore, the outgoing light is expressed by the following equation (3).

[0036]

[Equation 3]

On the other hand, when the incident linearly polarized light vibrates in the y-axis direction (becomes an extraordinary ray of the birefringent crystal plate 11), similarly, the emitted light is represented by the formulas (4) to (6). You can ask.

[0038]

[Equation 4]

Therefore, in any case, the intensity ratio (extinction ratio) of the side spots is expressed by the following equation (7) (approximate is when Δθ is sufficiently small).

[0040]

[Equation 5]

Further, when the extinction ratio is expressed in dB, the following equation (8)
Is the street.

[0042]

[Equation 6]

Next, the backward incidence will be examined.

As shown in FIG. 2 (B), linearly polarized light 10'a (oscillating in the x-axis direction in the figure) incident from the right side must pass through the magneto-optical crystal plate 13 and the half-wave plate 12. Therefore, the output light 1 having a polarization plane in the same direction as the original state
It is emitted as 0'b. Where, as mentioned above,
When the crystal axis of the wave plate 12 is deviated by Δθ, the emitted light is a side spot having a polarized plane rotated by 90 degrees from the state of the incident plane, in addition to the emitted beam 10′b having the same polarization direction as that of the incident plane. 10'c is produced.

In this case, the angle θ formed by the polarization plane of the outgoing light with the x-axis and the outgoing light component are expressed by equations (9) and (1), respectively.
0).

[0046]

[Equation 7]

On the other hand, in the case where the linearly polarized light which is incident in the opposite direction is the linearly polarized light which vibrates in the y-axis direction, the following equation can be similarly obtained.

[0048]

[Equation 8]

Therefore, in any case, the component corresponding to the side spot is represented by sin ² (2 · Δθ).

The isolation of such an optical isolator is represented by the ratio of the backward incident light intensity (1 ² ) to the side spot component of the backward outgoing light. Therefore, the isolation is expressed by the following equation (13).

[0051]

[Equation 9]

The isolation thus obtained agrees with the extinction ratio shown by the equation (8). Therefore, if the absolute value of the extinction ratio is reduced, the absolute value of isolation is also reduced, and the characteristics are improved.

By the way, the extinction ratio expressed by the equation (7) is
It is a ratio of the minimum power level and the maximum power level obtained by the method of the present invention. Therefore, when the position of each element is adjusted by the method of the present invention so as to minimize the ratio between the minimum power level and the maximum power level, as a result, an optical isolator main body having excellent isolation characteristics is assembled. It is clear that

3 to 5 exemplify a measuring system for carrying out the method of the present invention.

In the measurement system shown in FIG. 3, a polarizer 2 is arranged on one side of the optical isolator body 1 and an analyzer 4 is arranged on the other side. Further, a lens 6 is further provided on the side of the polarizer 2.
The light source 7 is arranged, and the light receiver 5 is arranged on the analyzer 4 side.

The measurement system shown in FIG. 4 has the configuration shown in FIG. 3 and further includes a half-wave plate 3 disposed between the optical isolator body 1 and the polarizer 2.

The measurement system shown in FIG. 5 has the configuration of FIG. 3 and further includes a quarter wavelength plate 8 arranged between the polarizer 2 and the lens 6.

In the method of the present invention, for example, the measurement system as shown in FIGS. 3 to 5 is used, and the light from the light source 7 is incident on the optical isolator main body 1 as linearly polarized light as an ordinary ray or an extraordinary ray through the lens 6. To do. Then, the analyzer 4 is rotated to measure the minimum power level and the maximum power level obtained by the light receiver 5, and the optical isolator main body 1 is configured so that the ratio of maximum power level / maximum power level is minimized. Adjust the position of the element.

The position adjustment of each element by the method of the present invention needs to be performed in order, but as described above, the position adjustment of the ½ wavelength plate that greatly affects the isolation characteristic is performed first, and then the double adjustment is performed. It is preferable to align the refraction crystal plate. Since the magneto-optical crystal plate has almost no influence on the characteristics even if it is tilted by about ± 5 degrees, it is usually unnecessary to perform the alignment by the method of the present invention. Of course, the alignment according to the method of the present invention may be performed only for the half-wave plate.

According to the method of the present invention, isolation can be evaluated by measuring the extinction ratio. The extinction ratio may be measured by receiving all the outgoing lights that are orthogonal to each other. Therefore, it is not necessary to attach the collimator lens to the light receiver side and adjust its installation as in the past.
Measurement can be easily performed by using a light receiver having a large light receiving area.

Next, a specific example of the present invention will be described.

While measuring the isolation by the above method, the directions of the half-wave plate 12 constituting the isolator body, and the inclinations of the surfaces of the birefringent crystal plates 11 and 14 and the magneto-optical crystal plate 13 were adjusted. As a result, the forward loss was adjusted to 0.5 dB, the return loss was adjusted to 58 dB, and the isolation was adjusted to 40 dB or more.

The specific procedure is as follows.

A. First, a measurement system as shown in FIG. 3 is prepared, and the polarization directions of the polarizer 2 and the analyzer 4 are made the same so that light can pass through both.

B. Next, only the incident-side birefringent crystal plate 11 is placed in the optical axis of the measurement system, and the directions of the polarization directions of the polarizer 2 and the analyzer 4 are finely adjusted so that the transmitted light is maximized. .

C. Then, the half-wave plate 12, the magneto-optical crystal plate 13, and the birefringent crystal plate 14 are inserted. At this time, the polarization state of the light emitted from the isolator body is 90
° It is rotating.

D. Next, the half-wave plate 12 is slightly rotated left and right to be in the minimum transmission state in which the emission intensity is minimized and the minimum power is measured. From this state, the analyzer 4
Measure the maximum power by rotating it to the maximum transmission state.
Then, the extinction ratio is calculated from the above equation (8) (extinction ratio = 3
5.0 dB).

E. Next, the exit-side birefringent crystal plate 14 is slightly rotated to the left and right, and is adjusted in the same manner as d to obtain the extinction ratio (extinction ratio = 38.5 dB).

F. The same adjustment as in d is performed again (extinction ratio =
39.5 dB).

G. Perform the same adjustment as for e again (extinction ratio =
40.5 dB).

H. Fix while holding the adjusted position of each crystal.

The method of fixing each crystal to form an optical isolator is not particularly limited. As an example of this method, a method of directly adhering each crystal plate by using an ultraviolet curable adhesive, a thermosetting adhesive such as an epoxy-based adhesive, or fixing an adapter holding the peripheral portion of each crystal plate For example, a method of fixing the adapters by bonding, soldering, welding, or the like, a method of inserting the peripheral edge of each crystal plate into a groove formed in the substrate and fixing it with an adhesive, and the like can be mentioned. When a groove is formed on a substrate to hold each crystal plate, the crystal plate may be tilted in the front-rear direction when the groove width is large. Therefore, it is necessary to finely adjust the direction.

After fixing the crystal plates to each other in this manner, this is fixed to a frame body provided with a magnet for magnetizing the magneto-optical crystal plate 13 or a cylindrical frame body made entirely of magnets. It is fixed to form the optical isolator main body 1, which is further incorporated in the housing. Further, the collimator lens and the optical fiber are assembled into the housing as needed.

An example of this is shown in FIGS. 6 and 7. Figure 6
An assembly obtained by fixing the birefringent crystal plate 11, the half-wave plate 12, the magneto-optical crystal plate 13 and the birefringent crystal plate 14 to the silicon substrate 21 is fixed to the cylindrical magnet 15,
It shows how the optical isolator body is assembled. Figure 7
FIGS. 7A and 7B are for explaining a state in which such an optical isolator main body is incorporated into a housing to form an optical isolator. FIG. 7A shows its appearance and FIG. 7B shows an internal configuration. It is shown schematically. In FIGS. 7A and 7B, the optical isolator main body 1 is incorporated in a cylindrical metal casing 16, and a lens 17 held by a lens holder 22 is attached to the casing 16. ing. A ferrule 24 is fixed to the lens holder 22 via a sleeve 23, and the end of the optical fiber 18 is held by the ferrule 24.

In the assembly of such an optical isolator, since the optical isolator main body 1 has already been adjusted and the isolation value of the main body is known at the same time, the entire assembly and adjustment can be completed in a short time.

In order to perform the measurement of the method of the present invention more effectively, it is desirable that the incident power level is constant. However, since the light incident on the polarizer 2 can have various polarization states, the power level of the linearly polarized light obtained by rotating the polarizer 2 is not always constant.

Therefore, in step b of the above-mentioned embodiment, it requires skill to find the maximum transmission state. That is, whether the intensity change of the emitted light occurs before and after the position where the angle between the crystal axis of the birefringent crystal and the polarization direction of the polarizer is 0 ° or 90 °, the polarization state of the light and the polarization of the polarizer It is difficult to distinguish whether the strength change occurs before and after the point where the direction matches. Therefore, to facilitate this work,
It is preferable to use the measurement system shown in FIG. 4 or FIG.

In the measuring system shown in FIG. 4, the half-wave plate 3 is inserted between the polarizer 2 and the optical isolator body 1. In this case, even if the angle of the polarizer 2 is arbitrary, 1 /
By rotating the two-wave plate 3, the polarization direction of the transmitted light can be rotated. Therefore, in step b of the above-described embodiment, the ½ wavelength plate 3 may be rotated instead of the polarizer 2. Thereby, the maximum transmission state can be easily found.

In the measurement system shown in FIG. 5, a quarter wavelength plate 8 is inserted on the incident side of the polarizer 2. In this case, the light incident on the polarizer 2 becomes circularly polarized light. Therefore, even if the polarizer 2 is rotated, the intensity of the transmitted light is constant. This similarly facilitates the work in step b of the above-described embodiment.

[0080]

As described above, according to the present invention,
The isolation of an optical isolator can be determined by simply measuring the maximum and minimum power levels when the analyzer is rotated about 90 degrees. Further, in this measurement, since no lens is used in front of the light receiver, there is no need to perform precise axis alignment, and there is a feature that measurement can be performed easily.

Therefore, by applying the measuring method of the present invention, the alignment of the components can be adjusted while measuring the isolation of the optical isolator body.

Further, by applying the method of the present invention, the isolation of the optical isolator main body can be adjusted and then incorporated into the housing, so that the entire optical isolator can be assembled and adjusted accurately and in a short time. You can

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the measurement principle of the method of the present invention.

FIG. 2 is a schematic diagram showing a case where linearly polarized light is incident on the optical isolator main body of FIG.

FIG. 3 is a schematic diagram showing an example of a measurement system for carrying out the method of the present invention.

FIG. 4 is a schematic diagram showing another example of a measurement system for carrying out the method of the present invention.

FIG. 5 is a schematic view showing another example of the measurement system for carrying out the method of the present invention.

FIG. 6 is a schematic view showing an example of assembly of an optical isolator main body.

FIG. 7 shows an assembled state of the optical isolator, (A) shows
FIG. 3 is an external view showing an optical isolator according to an example, and FIG. 3B is a schematic view showing the configuration of the optical isolator of FIG.

FIG. 8 is a schematic diagram showing the configuration and function of an example of an optical isolator main body.

FIG. 9 is a schematic view showing an optical isolator incorporating an optical fiber main body.

[Explanation of symbols]

 1 Optical Isolator Main Body 2 Polarizer 3 1/2 Wavelength Plate 4 Analyzer 5 Light Receiver 6 Lens System 7 Light Source 8 1/4 Wavelength Plate 11, 14 Birefringent Crystal Plate 12 1/2 Wavelength Plate 13 Magneto-Optical Crystal Plate

Claims (9)

[Claims] 1. A light source, a lens system, a polarizer, an analyzer and a light receiver are arranged in this order, and the light emitted from the light source and transmitted through the lens system, the polarizer and the analyzer is received by the light. A measuring system for receiving light with a detector; a step of arranging components constituting an optical isolator main body between the polarizer and the analyzer; of a light receiving level of the light receiver when the analyzer is rotated. Measuring a maximum value and a minimum value and obtaining a ratio of the minimum value to the maximum value; and adjusting a rotational position of each component forming the optical isolator body so that the ratio becomes a minimum. A method for assembling an optical isolator, comprising: 2. A light source, a lens system, a polarizer, an analyzer, and a light receiver are arranged in this order, and the light emitted from the light source and transmitted through the lens system, the polarizer, and the analyzer is received by the light. A measuring system for receiving light by a container; a step of arranging a component forming an optical isolator main body between the polarizer and the analyzer; when the analyzer is rotated for each rotational position of the component Measuring the maximum value and the minimum value of the light reception level of the light receiver; and adjusting the position of the part to the rotational position of the part where the ratio of the minimum value to the maximum value is the minimum;
A method for assembling an optical isolator, comprising: 3. The method for assembling an optical isolator according to claim 1, wherein the measurement of the maximum value and the minimum value, and the rotational position adjustment by the measurement are performed for each component of the optical isolator main body. 4. The method according to claim 1 or 2, wherein the measurement of the maximum value and the minimum value, and the rotational position adjustment by the measurement are performed for each component of the optical isolator main body, and this is repeated a plurality of times. Optical isolator assembly method. 5. The half-wave plate according to claim 1, wherein a half-wave plate is arranged immediately after the polarizer, and alignment of the polarizer with respect to the optical isolator main body in a rotational direction is performed.
An assembling method of an optical isolator, which is performed by rotating the half-wave plate. 6. The method for assembling an optical isolator according to claim 1, wherein a quarter wave plate is arranged immediately before the polarizer. 7. A light source, a lens system, a polarizer, an analyzer and a light receiver are arranged in this order, and the light emitted from the light source and transmitted through the lens system, the polarizer and the analyzer is received by the light receiving device. A measuring system for receiving light with a detector; a step of arranging an optical isolator main body between the polarizer and the analyzer; a maximum value and a minimum of a light reception level of the light receiver when the analyzer is rotated. A step of measuring a value; and a step of setting a value, which represents the ratio of the minimum value to the maximum value, in decibels, as the isolation. 8. The half-wave plate is arranged immediately after the polarizer, and the alignment of the polarizer with respect to the optical isolator main body in the rotational direction is performed by rotating the half-wave plate. A method for measuring isolation, which is characterized by being performed. 9. The method for measuring isolation according to claim 7, wherein a quarter-wave plate is arranged immediately before the polarizer.