Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-04-11
2001-08-28
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C708S422000
Reexamination Certificate
active
06281995
ABSTRACT:
BACKGROUND
The present invention relates generally to wavelength division multiplexed optical links, and more particularly, to wavelength division multiplexed optical links and signal processing methods that are limited by crosstalk arising from transmission non-idealities and from inadequate optical filtering at the receiver optical demultiplexer.
Previous techniques used to reduce the wavelength spacing of wavelength division multiplexed optical links have involved improving optical filtering schemes to separate more narrowly spaced wavelength division multiplexed channels. However, this has proved difficult for channel spacing below 50 GHz.
Accordingly, it is an objective of the present invention to provide for wavelength division multiplexed optical links and signal processing methods that use cross tap equalization to reduce crosstalk arising from inadequate optical filtering and thus enable narrower optical channel spacing.
SUMMARY OF THE INVENTION
To accomplish the above and other objectives, the present invention provides for improved wavelength division multiplexed optical links and signal processing methods that employ cross tap equalization to reduce crosstalk arising from inadequate optical filtering. In practicing the present invention, after optical filtering and photodetection, the wavelength division multiplexed signals adjacent to either side of a signal whose crosstalk is to be reduced are sampled, weighted and are then subtracted from the signal whose crosstalk is to be reduced. This is done using adaptive correlation, and is performed simultaneously on all signals, each with respect to its respective adjacent channels. Thus, crosstalk is removed electrically after photodetection. The present invention permits use of more closely spaced optical carriers to be used in the wavelength division multiplexed optical link.
REFERENCES:
patent: 4355368 (1982-10-01), Zeidler et al.
patent: 4989201 (1991-01-01), Glance
Spickerman Ralph
Waugh Geoffrey S.
Float Kenneth W.
Lockheed Martin Corporation
Negash Kinfe-Michael
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