Optical waveguides – With optical coupler – Input/output coupler
Patent
1993-05-03
1995-03-28
Healy, Brian
Optical waveguides
With optical coupler
Input/output coupler
385 6, 385 11, 385 36, 385 31, 359280, 359281, 359282, 359283, G02B 632, G02F 109
Patent
active
054025095
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an optical device for optically connecting a pair of optical fibers (a first and a second optical fiber) and, more particularly, relates to an optical device having two or more functions including the function of an optical isolator and suitable for use in such an optical system as an optical amplification system and a two-way optical transmission system.
2. Description of the Related Art
As references disclosing optical devices for connecting a first optical fiber with a second optical fiber, specifications of U.S. Pat. No. 4,548,478 and Japanese Patent Publication No. 61-58809 are known. The optical devices disclosed in such specifications have the function of an optical isolator, of which the forward transmittance is not dependent on the polarization state of the input light beam (polarization-independent isolator). The polarization-independent optical isolator in principle couples all of the light rays output from a first optical fiber to a second optical fiber and couples none of the light rays output from the second optical fiber to the first optical fiber. Hereinafter, the polarization-independent isolator will be briefly referred to as "optical isolator".
The optical isolator of the described type has many uses. For example, in an optical amplification system provided with an optical amplification medium of the optical pumping type, there is used an optical isolator to prevent formation of an optical resonator structure including the optical amplification medium in the resonating optical path. As a practicable optical amplification system including an optical amplification medium of the optical pumping type, there is known an optical fiber amplifier including, as the optical amplification medium, an optical fiber (doped fiber) at least the core of which is doped with a rare earth element such as Er, Nd, and Yb.
In the optical fiber amplifier, signal light and pumping light are introduced into the doped fiber and the signal light is directly amplified on the principle of stimulated emission at the wavelength of the signal light. Therefore, in order to construct an optical fiber amplifier, a multiplexer for introducing the signal light and the pumping light supplied through separate routes into a single doped fiber and other peripheral parts become indispensable. If an optical device having functions of two or more of such peripheral parts is realized, it will be very useful in simplifying the structure of an optical amplification system or the like.
Accordingly, an object of the present invention is to provide an optical device being simple in structure and having two or more functions including the function of an optical isolator.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an optical device for optically connecting a first optical fiber and a second optical fiber with an optical path provided between the first and second optical fibers, which comprises a first and a second lens disposed in the optical path for collimating light beams emitted from excitation ends of the first and second optical fibers, respectively, into a beam of virtually parallel rays, a first and a second double refraction element disposed between the first and second lenses, each thereof having an optical axis in a predetermined relationship with the optical path, a first magnetooptic element disposed between the first and second double refraction elements for rotating the plane of polarization of transmitted light therethrough by an angle of 45.degree., and an excitation port disposed in a predetermined position in the vicinity of the excitation end of the second optical fiber for emitting at least a linearly polarized light beam corresponding to either of the ordinary ray and the extraordinary ray in the second double refraction element, and in which a beam of parallel rays obtained by having a light beam from the excitation end of the first optical fiber collimated by the first lens is pass
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Fujitsu Limited
Healy Brian
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