JP2001091900A - Optical isolator and its assembling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an isolator which does not necessitate an additional screening of non-defective by means of an optical measuring system after completing the assemblage, widely shortens the assembling time, widely reduces a production cost and has individually small variance of optical characteristic. SOLUTION: In an optical isolator having a polarizer 10, an azimuth rotator 30 and an analyzer 20, polarizing direction display parts 10a and 20a are respectively formed on the polarizer 10 and the analyzer 20, the polarizer 10 and the analyzer 20 are held respectively by holders, on which polarizing direction indicating parts 12 and 22 are formed. The optical isolator is assembled on the basis of the polarizing direction indicating parts 12 and 22 of an optical polarizer holder 11 and an analyzer holder 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator used for optical fiber communication using a semiconductor laser and an optical fiber amplifier.

[0002]

2. Description of the Related Art Semiconductor lasers (hereinafter abbreviated as LDs)
In the case, when the emitted light is reflected outside and enters the active layer again as return light, the oscillation wavelength and output fluctuate. For this reason, it is indispensable to prevent return light in order to perform highly reliable optical communication such as high-speed and high-density signal transmission and high-precision optical measurement. Used. The basic principle of the function of the optical isolator will be described with reference to FIG.

The optical isolator comprises an optical element such as a polarizer 51, an optical rotator 52, an analyzer 53, and a magnet for applying a magnetic field to the optical rotator 52. FIG. 8 (a)
As shown in (5), for the light 59 traveling in the forward direction, the polarization component 55 that matches the polarization plane of the polarizer 51 is selected by the polarizer 51 and enters the optical rotator 52. The length of the optical rotator 52 is determined so that the polarization plane of the incident light is rotated by 45 degrees while the light passes by the Faraday effect.
After passing through 2, the polarization plane 56 of the light
It has rotated 5 degrees. Therefore, if the polarization plane 57 of the analyzer 53 is rotated by 45 degrees with respect to the polarization plane of the polarizer 51, light is emitted without any loss at the analyzer 53.

[0004] On the other hand, as shown in FIG. 8 (b), the light 60 incident from the opposite direction is selected by the analyzer 53 after the light on the polarization plane 57 rotated 45 degrees with respect to the polarizer 51.
It is further rotated 45 degrees by the optical rotator 52. Therefore,
Polarization component 58 shifted by 90 degrees with respect to the polarization plane of polarizer 51
Is incident on the polarizer, no component passes through the polarizer 51, and all light incident from the opposite direction is removed.

FIG. 9 is a sectional view showing a conventional optical isolator.

The polarizer 51 is fixed to a polarizer holder 61 in advance, and the analyzer 53 is fixed to an analyzer holder 62 in advance, and the optical rotator 52 is either directly to the polarizer holder 61 or the analyzer holder 62 or to another. It is fixed together with either the polarizer 51 or the analyzer 53 via a holder, and measures the maximum of the isolation value while measuring the isolation with an optical measurement system including a semiconductor laser, a lens, a power meter, and the like. According to the values, the polarizer holder and the analyzer holder were fixed by bonding, soldering, YAG laser welding or the like.

[0007]

However, in the conventional structure, small elements of about 1 mm are assembled one by one while measuring the isolation by an optical measurement system, which is complicated for manufacturing an optical isolator. Since it takes time and effort to assemble while measuring one by one, the dispersion of the optical characteristic values for each product is very large. There was a problem that did not become.

Further, since the polarizer 51 and the analyzer 53 cannot be distinguished from their appearance in terms of their polarization directions, the polarizer 51
And it is difficult to align the analyzer 53 by 45 degrees.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is directed to an optical isolator having a polarizer, a rotator, and an analyzer. Is formed.

In an optical isolator having a polarizer, an optical rotator and an analyzer, the polarizer and the analyzer are respectively held by holders, and a polarization direction display section is formed in each of the holders.

Further, in the optical isolator having the polarizer, the optical rotator and the analyzer, the polarizer and the analyzer are respectively held by holders and assembled with reference to the polarization direction display section of each holder.

That is, by confirming the polarization direction at the stage of the large wafer of the polarizer and the analyzer and forming the polarization direction display portion, the product can be assembled only by the alignment after that, and the conventional optical system can be assembled. Compared with the method of assembling while measuring with a measuring system, the assembling time is greatly reduced, the manufacturing cost can be greatly reduced, and variations in optical characteristics of each one can be eliminated.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1A is a longitudinal sectional view of the optical isolator of the present invention. FIG. 1B is a side view of the polarizer holder to which the polarizer is fixed. FIG. 1C is a side view of the analyzer holder to which the analyzer is fixed.

The polarizer 10 has a rectangular shape, and the polarization plane is aligned with the long side to form a polarization direction display section 10a. The polarization direction of the polarization direction display section 12 formed on the polarizer holder 11 is also matched. Fixed in state. Similarly, the analyzer 20 also has a rectangular shape, and the polarization plane is aligned with the long side to form a polarization direction display section 20a.
The polarization direction of the concave polarization direction display section 22 formed in
It is fixed in a state shifted by 5 degrees clockwise. The optical rotator 30 is fixed directly to one of the polarizer holder 11 and the analyzer holder 21 or via another holder.
A cylindrical magnet 40 for applying a magnetic field is disposed. Then, with the convex polarization direction display section 12 of the polarizer holder 11 and the concave polarization direction display section 22 of the analyzer holder 21 fitted together, the polarizer holder 11 and the analyzer holder 2
1 are joined by YAG laser welding.

By providing the polarization direction display sections 12 and 22 in this manner, the alignment can be easily performed only by aligning them.

In FIG. 1, the polarizer 10 is provided with an optical rotator 30. However, the same effect can be obtained by attaching the optical rotator 30 to the analyzer 20.

Although the names of the polarizer 10 and the analyzer 20 are different for the purpose of use, usually the same optical element is used, and an absorbing polarizer or a birefringent polarizer can be used.

The rotator 30 is preferably a flat Faraday rotator made of terbium-bismuth garnet or gadolinium-bismuth garnet.
A self-magnetic-field-holding Faraday rotator that can rotate light without using the magnet 40 can also be used.

The polarizer holder 11 and the analyzer holder 21
Metal such as stainless steel, nickel-iron alloy and nickel-cobalt-iron alloy can be used. Although a permanent magnet can be used as the magnet 40, it is preferable to use a permanent magnet having a high magnetic field density, such as a samarium-cobalt alloy.

Next, various embodiments of the shapes of the polarizer 10 and the analyzer 20 are shown in FIGS. 2 (a) to 2 (k).

FIGS. 2A to 2E are rectangles, ellipses, trapezoids, rhombuses, and isosceles triangles, whose polarization planes are aligned in the long-side direction. FIG. 2F shows an irregular polygon, but the polarization direction is adjusted to the long side of the polygon, and the polarization display unit 10a (2
0a). FIG. 2 (g) shows a modified star shape, which also has its polarization plane aligned in the longitudinal direction. FIG.
(H) to (k) are squares and circles, but concave and convex portions are partially provided, and the polarization direction is adjusted to that direction.

Here, FIGS. 2A to 2G show the shape itself as the polarization direction display section 10a (20a) of the polarization plane.
(H) to (k) show the concave or convex portions in the polarization direction display section 1.
Although 0a (20a) is used, other shapes may be used as long as the polarization direction of the polarization plane can be recognized.

Next, various embodiments of the polarizer holder 11 and the analyzer holder 21 are shown in FIG.

Since the polarizer holder 11 and the analyzer holder 21 are made of metal, a hole 13 is provided in the light passage so as not to block the light, and the polarizer 10 or the analyzer 20 is provided in this portion. Fixed. The hole 13 has a circular shape, but may be formed in various shapes such as a rectangle, an ellipse, a trapezoid, and a rhombus.

3 (a) to 3 (e) are rectangles, ellipses, trapezoids, rhombuses, and isosceles triangles, and the polarization direction is aligned with the long side direction to form the polarization direction display section 12 (22). FIG. 3 (f) shows an irregular polygon, but the polarization direction is adjusted to the long side to form the polarization direction display section 12 (22).
FIG. 3 (g) shows a modified star shape, which also has its polarization plane aligned in the longitudinal direction. FIGS. 3 (h) to 3 (k) are squares and circles, but concave and convex portions are partially provided, and the polarization direction is adjusted to that direction.

Here, FIGS. 3 (a) to 3 (g) show the shape itself as the polarization direction display section 12 (22) of the polarization plane.
(H) to (k) show the concave or convex portions in the polarization direction display section 1.
Although 2 (22) is used, other shapes may be used as long as the polarization direction of the polarization plane can be recognized.

In addition to these embodiments, as shown in FIG. 4, a marking 14 is formed on the surface or the outer periphery of the polarization holder 11 or the analyzer holder 22 with a YAG laser, Magic (registered trademark) or the like, and the marking 14 is formed. Polarization direction display section 12 (2
Exactly the same effect can be achieved even in 2).

Next, a method for assembling the optical isolator according to the present invention will be described. FIG. 5 is a flowchart showing a method of assembling the optical isolator according to the present invention.

The processing method of the polarizer 10 and the analyzer 20 is as follows.
An optical element in which the polarization plane direction of a large wafer-shaped polarization element is checked in advance with a polarizing plate, marked with oily magic or the like, and a small polarization direction display unit of about 1 mm is formed in accordance with the marking direction. The method of cutting is used.

The cutting method may be a method of punching out by ultrasonic processing, a method of laser processing, or a method of jetting using a water flow. If the shape is rectangular, there is a method of grinding each side with a flat toothed grindstone. Next, the polarization direction display section 10a of the polarizer 10 is replaced with the polarization direction display section 1 of the polarizer holder 11.
Fix according to 2. In this state, the polarization direction of the polarizer 10 and the polarization direction display section 12 of the polarizer holder 11 match. Next, the optical rotator 30 is fixed to the polarizer holder 11.

The polarization direction display section 20a of the analyzer 20 is fixed in a direction shifted clockwise by 45 degrees from the polarization direction display section 22 of the analyzer holder 21.

As a fixing method, any method such as bonding, press-fitting, soldering, and attaching a glass having a low melting point to both the polarizer 10 and the analyzer 20 can be used.

Finally, the polarization direction display section 12 of the polarizer holder 11 and the polarization direction display section 22 of the analyzer holder 21 are fixed so as to coincide with each other. Fixing method is soldering, bonding, Y
Any method of AG laser welding may be used.

As shown in FIG. 6A, a method for matching the polarization direction display sections 12 is to provide a convex polarization direction display section 12 on the polarizer holder 11 and a concave polarization direction display section on the analyzer holder 21. A method of combining these concaves and convexes by providing the polarization direction display sections 12 and 22 as shown in FIG.
6A, a sensor or image processing is used to automatically control the position. Alternatively, as shown in FIG. May be used.

Also, these assembling methods are merely examples, and if the assembling method is based on the polarization direction display portions 12 and 22 of the polarizer holder 11 and the analyzer holder 21,
Exactly the same effect can be obtained by other methods.

For example, the polarization direction display section 12 is formed on the side of the polarizer 10 shifted from the polarization direction by 45 °, and the analyzer 20 forms the polarization direction display section 22 so as to match the polarization direction. It may be something.

Further, the polarization direction display sections 12 and 22 of the polarizer 10 and the analyzer 20 are made to coincide with the respective polarization directions, and these polarization direction display sections 12 and 22 are connected to each other by 45 degrees.
A similar effect can be obtained by a method of joining the two with a stagger.

The effect of the present invention can be sufficiently obtained if the angle deviation between the true polarization directions of the polarizer 10 and the analyzer 20 and the polarization direction display sections 12 and 22 is within 5 °. By using the above assembling method, it is possible to sufficiently accommodate an angle deviation of 5 ° or less.

That is, the present invention is an assembling method in which a polarization direction indicating portion of a polarization plane is formed when a polarizer and an analyzer are cut, and thereafter, a product is formed only by adjusting the position and orientation. It is no longer necessary to sort non-defective products using the same optical measurement system after assembly, and the assembly time has been greatly reduced, manufacturing costs have been greatly reduced, and optical characteristics of individual components have been reduced. Variations are gone.

[0041]

EXAMPLE Here, an experiment was conducted by the following method.

A polarizer, an analyzer, an absorption polarizer, a rotator, a Faraday rotator made of garnet, a magnet, a permanent magnet, and a stainless steel for the polarizer holder and the analyzer holder. An isolator sample was made.

Fifty samples assembled on the basis of the polarization direction display part shown in FIG. 6A of the present invention were prepared, and as a comparative example, fifty samples assembled by conventional optical measurement were prepared, and 1310 nm The isolation was measured at a wavelength of and the distribution of the measured values was examined.

FIG. 7 is a diagram showing the distribution of the isolation. The vertical axis shows the quantity and the horizontal axis shows the isolation value.

From these results, the average value is almost the same, but the variation is remarkably improved in the present invention as compared with the conventional example.

As described above, when the polarizer and the analyzer of the present invention are cut, the polarization direction display portion of the polarization plane is formed, and then the product is manufactured only by the alignment of the position. It became smaller and stable production became possible, and after the assembly was completed, it was no longer necessary to carry out further optical measurements to select those having a standard value.

[0047]

As described above, according to the present invention, a polarizer,
In an optical isolator having an optical rotator and an analyzer, a polarization direction display section is formed on the polarizer and the analyzer, and assembly is performed based on these polarization direction display sections. This eliminates the necessity of performing, and significantly reduces the assembly time and the manufacturing cost, and also eliminates variations in optical characteristics of individual components.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of an optical isolator of the present invention,
(B) is a side view of the polarizer holder to which the polarizer is fixed,
(C) is a side view of the analyzer holder to which the analyzer was fixed.

2 (a) to 2 (k) show various embodiments of the polarizer and analyzer of the present invention.

FIGS. 3A to 3K are views showing various embodiments of the polarizer holder and the analyzer holder of the present invention.

FIG. 4 is a view showing another embodiment of the polarization direction display section of the polarizer holder and the analyzer holder of the present invention.

FIG. 5 is a flowchart showing a method of assembling the optical isolator according to the present invention.

FIGS. 6A to 6C are diagrams illustrating a method of matching polarization direction display sections in the optical isolator according to the present invention.

FIG. 7 is a diagram showing the distribution of the isolation of the optical isolator according to the present invention and the conventional example.

FIG. 8 is a diagram showing the basic principle of the function of the optical isolator.

FIG. 9 is a longitudinal sectional view showing a conventional optical isolator.

[Explanation of symbols]

 10: Polarizer 10a: Polarization direction display unit 11: Polarizer holder 12: Polarization direction display unit 13: Hole 14: Marking 20: Analyzer 20a: Polarization direction display unit 21: Analyzer holder 22: Polarization direction display unit 30: Rotator 40: Magnet

Claims (3)

[Claims] 1. An optical isolator having a polarizer, a rotator, and an analyzer, wherein a polarization direction display section is formed on the polarizer and the analyzer. 2. An optical isolator having a polarizer, an optical rotator and an analyzer, wherein the polarizer and the analyzer are respectively held by holders, and a polarization direction display section is formed in these holders. 3. An optical isolator having a polarizer, an optical rotator, and an analyzer, wherein the polarizer and the analyzer are respectively held by holders, and assembled based on a polarization direction display section of each holder. How to assemble an isolator.