Optical isolator

Details Optical isolator Optical isolator

1992-11-05

1995-01-10

Shafer, Ricky D.

Optical: systems and elements

Optical modulator

Light wave temporal modulation

359484, 359497, 372703, G02B 530

Patent

active

053812611

DESCRIPTION:

BRIEF SUMMARY
DETAILED DESCRIPTION OF THE INVENTION

1. Applicable Field of Invention
The present invention relates to an optical isolator for obstructing reflected light in the input/output of an optical system such as a fiber optic communication or an optical disk which uses a semiconductor laser and more particularly to an isolator which is not influenced by incident light and not sensitive to the change in temperature or to the fluctuation in the wavelength of light.
2. Conventional Art
It is known that in the semiconductor laser which serves as a main light source in the input/output of the fiber optic communication and the optical disk, the oscillation thereof becomes unstable in response to beams reflected by the optical system such as the end surface of an optical fiber, the connection point between optical fibers, a connecting lens or an optical connector and as a result, operation characteristic becomes deteriorated greatly, i.e., noise increases, the output fluctuates or the like. In order to solve the unstable operation performance of the semiconductor laser and achieve a stable light source to be used for an optical communication, various optical isolators have been developed.
An optical isolator comprising a Rochon prism used as a polarizer and an analyzer; Faraday rotors made of YIG (yttrium iron garnet) monocrystal or Bi-replaced garnet; and an annular permanent magnet consisting of such as SmCo for magnetizing the Faraday rotors in the forward direction is widely known. The optical isolator having such a construction has a disadvantage that only a certain plane of polarization is effective and a beam, not coincident with the polarization direction of the optical isolator, which has been incident on the optical isolator is greatly lost. If the optical isolator is used by inserting it between optical fibers, an optical isolator not dependent on polarized beams is preferable because the linear polarization is not maintained in optical beams which transmit the optical fibers.
In this situation, as a construction displaying isolation effect for all planes of polarization without being dependent on a certain polarization direction, an optical isolator of polarization-undependent type utilizing the separation/synthesis of ordinary beams and extraordinary beams by means of not a Rochon prism but a flat double refractive crystal such as calcite has been proposed. For example, according to an optical isolator proposed by Mr. Matsumoto in Japanese Patent Laid-Open Publication No. 55-22729, it comprises a lens, a first flat double refractive crystal, one magnetic optical material (Faraday rotor), optical rotatoty crystal (or anisotropic crystal), and a second flat double refractive crystal arranged in a row in the order from the incident side and a permanent magnet for magnetizing a magnetic optical material.
But the optical isolator having the conventional construction as disclosed in Japanese Patent Laid-Open Publication No. 55-22729 has a great disadvantage that it is sensitive to the change in temperature and the fluctuation in the wavelength of light and thus many reflected beams from the backward direction pass through the incident point. Some constructions for eliminating such a disadvantage have been proposed. For example, a shown in FIG. 22, an optical isolator 150 proposed by Mr. Chang in European Patent Publication No. 0352002 comprises five flat double refractive crystals (anisotropic crystals) 152, 156,160, 164, and 168; four Faraday rotors (irreversible rotors) 154, 158, 162, and 166 each disposed between adjacent parallel flat double refractive crystals. The direction (walk-off direction) of the optical axis of each of the second, third, fourth, and fifth flat double refractive crystals 156, 160, 164, and 168 has an angle of 135.degree., 180.degree., 315.degree., and 90.degree. with respect to the optical axis of the first flat double refractive crystal 152 and the four Faraday rotors 154,158, 162, and 166 rotate the polarization plane by 45.degree. in the same direction. The thickness of the first t

REFERENCES:
patent: 4239329 (1980-12-01), Matsumoto
patent: 4974944 (1990-12-01), Chang
patent: 5151955 (1992-09-01), Ohta et al.
Chang et al.; "High-Performance Single-Mode Fiber Polarization-Independent Isolators"; Optics Letters; vol. 15, No. 8; Apr. 15, 1990.
Chang et al.; "Polarization Independent Isolator Using Spatial Walkoff Polarizers"; IEEE Photonics Technology Letters; vol. 1, No. 3; Mar. 1989.

Affiliated with

Also associated with

Rating

Optical isolator does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical isolator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical isolator will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-855005