JPH04177316A - Light isolator - Google Patents

Abstract

PURPOSE:To improve assembly efficiency per one layer, and to obtain an isolator of high reliability by providing parts where a solder is not provided on at least one part of the inner diametrical part, the outer diametrical part, and the end surface of a holder, and on at least one part of the outer periphery of a permanent magnet. CONSTITUTION:Metallization (Ni-Au alloy) for solder connection is provided on the entire surface of rotation holders 4a, 4b, and of a permanent magnet 3 and a spacer 9, while the metallization is not provided on the inner diametrical part 12 as well as the outer diametrical part 13 of the rotation holder 4a, 4b, and also on an end part 15 of the permanent magnet 3. Superfluous extrusion of the solder can be prevented due to the portion on which metallization is not provided. The connection method of high reliability is thus achieved and a light isolator of high reliability can be obtained thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical isolator applied to high-speed, large-capacity optical communication systems, etc., and relates to improving the reliability of this optical isolator.

In recent years, high-performance semiconductor lasers have been used as light sources as optical communications have become faster and larger.

This semiconductor laser is sensitively affected by reflected light from an optical fiber or the like, and there is a phenomenon in which the oscillation characteristics of the laser become unstable. In order to prevent this reflected return light from reaching the semiconductor laser, an optical isolator with high reverse direction loss is essential.

A laser module with an optical isolator, which has a structure in which an optical fiber is attached to this semiconductor laser, is being used. Optical components such as these optical isolators are required to have high reliability, so conventional resin fixing using adhesives or the like produces gas and is therefore inferior in reliability. Therefore, a fixing method other than resin is required to fix the optical components. For this fixing method, a fixing method using solder is used.

[Prior Art] FIG. 4 is a diagram for explaining the structure of an optical isolator, in which 1 is a Faraday rotator, 2a and 2b are polarizers, and 3 is a diagram for explaining the structure of an optical isolator.
4a', 4b' are the hollow permanent magnets, 4a' and 4b' are the polarizers 2a,
A rotary holder 2b is used to fix the optical isolator, and an outer case 6 is used to reinforce the overall strength of the optical isolator.

When assembling an optical isolator using the conventional technique as shown in FIG. 5, a Faraday rotator 1 and two polarizers 2a, 2
b is the axial hole 10a of the rotating holder 4a', 4b',
Holes 5a, 5 for inserting from 10b and pouring adhesive
Add adhesive from b and 5c and fix.

Reference numeral 9 shown in FIGS. 4 and 5 is a ring-shaped spacer that prevents direct contact between the Faraday rotator 1 and the polarizer 2b.

In the above-mentioned prior art, the optical isolator was assembled using a fixing method using resin such as adhesive. It has long been a problem that resin-based adhesives generate gas after curing. For this reason, optical components using resin bonding are inferior in high reliability. For this reason, there was a problem in that it was not possible to realize a high-performance and highly reliable optical isolator.

Therefore, an invention was made to connect and magnetize by soldering (see Japanese Patent Laid-Open No. 1-200223).

[! Problems to be Solved by 11 Mei] In the above-mentioned soldering bonding, solder was inserted through the holes 5a, 5b, and 5c and soldered by laser beam irradiation, similar to the conventional adhesive bonding. In this case, there was a problem in that the solder melted unevenly and lacked reliability.

To solve the above problem, we adopted plate-shaped solder bonding for the optical isolator, which consists of a Faraday rotator, a hollow permanent magnet containing it, and polarizers in front and on both sides of the Faraday rotator. It is possible to do so.

However, if the amount of melted solder is excessive, the solder will melt to the outer periphery of the optical isolator, changing the outer diameter, making it impossible to incorporate the optical isolator into high-precision optical equipment such as semiconductor laser modules. There were no problems.

Therefore, an object of the present invention is to provide a highly reliable bonding method and a highly reliable optical isolator made possible for the first time by the method.

[Means for Solving the Problems] The optical isolator of the present invention comprises a Faraday rotator 1 and a hollow permanent magnet 3 for magnetizing the Faraday rotator, and polarizers 2a and 2b are arranged on both sides of each Faraday rotator. The polarizer 2b and the Faraday rotator 1 are fixed to the disc-shaped holder 4b through the ring-shaped spacer 9 by soldering, and the other polarizer 2a is also fixed to the holder 4.
Fix it to a with solder. In this optical isolator, the rotating holders 4a, 4b, the permanent magnet 3, and the spacer 9 are metallized (Ni-Au alloy) for solder bonding on the entire surface. is not metalized. Further, the end portion 15 of the permanent magnet 3 is also not metalized. The feature is that this non-metalized portion prevents excessive solder from protruding.

[Example code] Examples of the present invention will be described in detail below.

FIG. 1 is a configuration diagram for explaining one embodiment of the present invention. In this figure, a polarizer 2b, a spacer 9, and a Faraday rotator 1 are stacked in order on a rotating holder 4b, a plate-shaped solder foil 7b is sandwiched between each component, and the solder is melted to be fixed. Further, at this time, it is also possible to fit a plate-shaped solder foil 7c between the rotary holder 4b and the permanent magnet 3, and insert and fix each of them from above the magnet. Here, the permanent magnet 3 is not magnetized so that the Faraday rotator 1 can be easily mounted.

The rotary holders 4a, 4b, the permanent magnet 3, and the spacer 9 are metallized (Ni--Au alloy) for solder bonding except for the inner diameter portion 12 and outer diameter 8i113 of the rotary holder. Furthermore, metallization is applied except for the end portion 15 of the permanent magnet 3. By not applying metallization, unnecessary protrusion of solder can be prevented. This is because solder does not spread to areas that are not metalized. After each component is fixed, a magnetic field to be applied to the Faraday rotator 1 can be obtained by magnetizing the permanent magnet 3.

It will be understood that with such a structure, the assembly method is much simpler than the prior art mounting method shown in FIG. 5, and unnecessary protrusion of solder can be prevented.

FIG. 2 is another configuration diagram for explaining the present invention in detail. In this case, the polarizer 2a is the rotating holder 4a.
It is fixed in the center with a plate-shaped solder i7b. The holder is metallized (Ni--Au alloy) for solder bonding except for the inner diameter part 12 and outer diameter part 13 of the rotary holder.

FIG. 3 is a perspective view of an optical isolator explaining the present invention in detail. Here, the rotation holder 48 is also fixed with a ring-shaped solder i7a. In order to join the rotary holder 4a, a solder i7a having a lower melting point than solder 7b and 70 is used. Even if the solder foil 7a is melted during assembly, the unmetallized portion can prevent the solder from excessively protruding, and the dimensions of the outer periphery of the optical isolator will not change.

[Effects of the Invention] As is clear from the above description, by using the structure of the present invention, a highly reliable optical isolator can be realized while further improving assembly efficiency.

[Brief explanation of the drawing]

1 to 3 are structural diagrams for explaining the present invention in detail, and FIGS. 4 and 5 are structural diagrams for explaining the prior art. 1; Faraday rotator, 2a, 2b; polarizer, 3; permanent magnet, 4a, 4b, 4a', 4b'; rotating holder 5a, 5b
, 5c; Through hole, 6; Outer case 7a, 7b, 7c; Plate solder foil 9; Spacer, 10a, 10b; Insertion port, 12; Inner diameter part, 13; Outer diameter part, 15; Magnet end FIG.

Claims (1)

[Claims] (1) An optical isolator having a solder joint consisting of a Faraday rotator, a hollow permanent magnet enclosing the Faraday rotator, polarizers on both sides of the Faraday rotator, and a holder for fixing the polarizer. An optical isolator characterized in that a portion to which solder does not adhere is provided at one or more locations on the inner diameter portion, the outer diameter portion, the end face, and the outer circumference of the permanent magnet.