Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Reexamination Certificate
1999-06-30
2001-08-14
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
C385S047000, C385S011000
Reexamination Certificate
active
06275637
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of fiber optics and, more specifically, to reflection type optical isolators.
BACKGROUND
Fiber optics are used in many applications including telecommunication and instrumentation. These applications transmit data by pulsing light waves through optical fibers. These optical fibers typically consist of one or more cores surrounded by a cladding, and a protective jacket. Optical components coupled to these fibers operate on light propagated through them, for example, optical isolators.
Optical isolators are used in fiber optic systems to propagate signals in a direction while preventing propagation of signals along a reverse of the direction. These optical isolators are often used to prevent unwanted signal reflections from being transmitted back to a signal's source. Typical optical isolators have components to separate, rotated, and recombine orthogonally polarized light. These components function to propagate light beams from the input to the output of the isolator while diverting light beams traveling in the opposite direction to prevent them from reaching the input port.
One type of optical isolator uses an isolator core positioned in-line between two lenses to couple light from an input fiber to an output fiber. The isolator core has, in sequence, an input walk-off crystal, a Faraday rotator, a half-wave plate, and an output walk-off crystal. In the forward direction, the input walk-off crystal divides an incident light beam from the input fiber into two polarized rays that are rotated by the Faraday rotator and the half-wave plate and then recombined by the output walk-off crystal. A Faraday rotator is a non-reciprocal device that rotates the polarization of light rays in the same direction regardless of which direction rays are passed through the device.
In the reverse direction, the output walk-off crystal also divides a light beam into two polarized rays. However, the non-reciprocal function of the Faraday rotator prevents the polarization of light traveling in the reverse direction from being rotated back to a position that will allow the two rays to be recombined by the input walk-off crystal. In this manner, light is prevented from reaching the input fiber in the reverse direction through the isolator core.
One problem with such an optical isolator is that the number and size of individual components adds to the overall length and size of the optical isolator, thereby decreasing its desirability.
SUMMARY OF THE INVENTION
The present invention pertains to an optical isolator. The optical isolator may include a thermally expanded multiple core fiber having at least one input core and at least one output core. The optical isolator may also include an isolator core coupled to the thermally expanded multiple core fiber to propagate light from the at least one input core to the at least one output core and inhibit the propagation of light from the at least one output core to the at least one input core.
Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.
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Chang Kok Wai
Huang Yong
Greene Kevin E.
JDS Uniphase Corporation
Lacasse Randy W.
Lacasse & Associates
Palmer Phan T. H.
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