Optical: systems and elements – Optical frequency converter
Reexamination Certificate
1999-01-06
2001-11-13
Lee, John D. (Department: 2874)
Optical: systems and elements
Optical frequency converter
C359S330000
Reexamination Certificate
active
06317252
ABSTRACT:
BACKGROUND
The present disclosure describes a system for copying an optical channel in an optical communications system. More specifically, the present system describes a special kind of four-wave mixing element which enables dynamic copying of single or multiple channels.
Fiber optic cable has the capability of carrying an enormous amount of information. Demand for bandwidth in long distance communication lines is growing rapidly because of applications like the Internet.
To accommodate this bandwidth growth, commercial fiber optic systems now employ wavelength division multiplexing “WDM” in which information is carried on many optical wavelengths spanning a wide optical bandwidth. Each wavelength is called a channel and can carry substantial amounts of information.
It may be desirable at some times to copy the information in one channel or a subset of channels.
For example, in applications such as next-generation-Internet, a fiber optical cable will carry multiple wavelengths and use packet switching techniques. Reading header information on a packet, for example, could require a device that can copy the channel which contains the packet. Once copied to a specific wavelength in the optical spectrum, the information can be conveniently filtered using a fixed wavelength filter and then read (i.e., detected). Clearly, it is important for the copying process to be non destructive.
SUMMARY OF THE INVENTION
The present system teaches a technique of modifying certain channel information in a way that allows the modified channel information to be separated from the other information.
The preferred mode carries this out by using a non-linear medium to mix the desired channel with a pump wave that shifts the information in the desired channel to a different frequency that corresponds to a resonant frequency of a cavity or resonator. The preferred non linear medium is a semiconductor four wave optical mixer that also provides optical gain for the resonator. The system also includes an optical Bragg filter, to create resonant enhancement of only a specified frequency sifted wave.
REFERENCES:
patent: 5195104 (1993-03-01), Geiger et al.
patent: 5233462 (1993-08-01), Wong
patent: 5243610 (1993-09-01), Murata
patent: 5619368 (1997-04-01), Swanson
patent: 5943161 (1999-08-01), Shinozaki et al.
patent: 5946129 (1999-08-01), Xu et al.
Hunziker Guido
Paiella Roberto
Vahala Kerry J.
California Institute of Technology
Fish & Richardson P.C.
Lee John D.
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