Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2001-01-04
2002-09-03
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
Reexamination Certificate
active
06445485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to methods and systems that control the states of polarization of optical beams.
2. Description of Related Art
As optical fibers are becoming more and more ubiquitous in the optical communications industry, the effects of polarization mode dispersion (PMD) caused by subtle defects of optical fibers become increasingly important. Generally, PMD occurs when an optical signal propagates through a birefringent optical fiber causing various components of the optical signal to travel at varying velocities, thus causing multiple images of the optical signal to appear at a receiver.
To aid in compensating for signal distortion arising from PMD, polarization-state controllers have been provided within the industry that “adjust” the state of polarization of an optical signal. However, these conventional controllers suffer from several problems, such as being unwieldy in size or capability. Therefore, there is a need for new methods and systems to control the states of polarization of optical signals.
SUMMARY OF THE INVENTION
The invention provides methods and systems for micro-machined polarization-state controllers of optical signals. Particularly, the invention provides methods and systems relating to compact and versatile polarization-state controllers such that the state of polarization of an optical signal can be manipulated to any point on a Poincaré sphere diagram. These polarization-state controllers can be formed by cascading a number of simple polarization rotators and 45° rotators integrated on a number of silicon substrates. Each polarization rotator can split a received optical signal into its fast and slow components. The fast and slow components can then be controllably delayed relative to each other using one or more adjustable micro-machined micro-mirrors and then recombined to form a single adjusted optical signal, thus controllably rotating the polarization state of the received optical signal.
Other features and advantages of the present invention are described below and are apparent from the accompanying drawings and from the detailed description which follows.
REFERENCES:
patent: 4799796 (1989-01-01), Musha
patent: 5793485 (1998-08-01), Gourley
patent: 5999303 (1999-12-01), Drake
patent: 6188477 (2001-02-01), Pu et al.
Frigo Nicholas J.
Goldstein Evan L.
Lin Lih-Yuan
Pu Chuan
Tkach Robert William
AT&T Corp.
Epps Georgia
O'Neill Gary W
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