Optical isolator

Details Optical isolator Optical isolator

1997-07-30

2001-08-14

Spyrou, Cassandra (Department: 2872)

Optical: systems and elements

Polarization without modulation

Polarization using a time invariant electric, magnetic, or...

C359S282000

Reexamination Certificate

active

06275336

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an optical isolator which is positioned between a semiconductor laser as a light source and a light-transmitting part, for instance, in an optical transmission system to thus prevent a laser beam reflected by the optical transmission part from returning to the light source.
A copper wire conductor had been used in the information transmission and, recently, the information is transmitted by an optical fiber in the telecommunication by personal computer and the like on behalf of multimedia because the improvement in the capacity of the information transmission is desired and thus an optical fiber has larger transmission than a copper wire conductor. The base part of the telecommunication line has almost finished exchanging for the optical fiber. Though the branch part is under exchanging, the capacity of the information transmission in the branch part may be smaller than that of the base part because the optical fiber is more expensive than the copper wire conductor.
An optical isolator, which is the device of an optical fiber system to prevent a laser beam reflecting on an optical fiber face to a semiconductor light source, is required cheaper. However, optical elements incorporated into the optical isolator are often formed from expensive materials such as oxide single crystals. Moreover, the precision must strictly be controlled when combining such elements. As has been explained above, the production cost of the optical isolator increases because of high cost of assembly thereof and costs required for parts such as a holder.
As a means for saving the cost for assembly, there has been known a method which comprises adhering, in advance, optical elements to one another and then cutting it into pieces having a desired size. However, the optical isolator assembled according to this method is insufficient in the resistance to thermal shock and the adhered plane thereof easily undergoes peeling off due to temperature change. For this reason, if such an optical isolator is used over a long period of time, the quality thereof is impaired
SUMMARY OF THE INVENTION
The present invention has been developed for solving the foregoing problems and an object of the present invention is, accordingly, to provide an optical isolator which permits the reduction of the production cost and which is excellent in the thermal shock resistance.
The optical isolator of the present invention comprises a Farady rotator and birefringent crystals or glass polarizers, whereby the Farady rotator be adhered to the birefringent crystals or glass polarizers through adhesive layers and that the glass transition point of the adhesive be not more than −40° C.
The optical isolator of the other embodiment of the present invention comprises a Farady rotator and birefringent crystals or glass polarizers, whereby the Farady rotator is adhered to the birefringent crystals or glass polarizers through adhesive layers, the adhesive has rubber elasticity in 10 to 40° C., the thickness of the adhesive layer is 10 to 100 &mgr;m, the area of optical plane in the optical isolator is not more than 2 mm
2
.


REFERENCES:
patent: 4679918 (1987-07-01), Ace
patent: 5341235 (1994-08-01), Watanabe et al.
patent: 5452122 (1995-09-01), Tsuneda et al.
patent: 5573833 (1996-11-01), Imamura et al.

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