Skip to Content
Find More Like This
Return to Search

Subcarrier multiplexing with dispersion reduction and direct detection

United States Patent

January 21, 1997
View the Complete Patent at the US Patent & Trademark Office
Lawrence Livermore National Laboratory - Visit the Industrial Partnerships Office Website
An SCM system for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream.
Sargis; Paul D. (Modesto, CA), Haigh; Ronald E. (Tracy, CA), McCammon; Kent G. (Livermore, CA)
The Regents of the University of California (Oakland, CA)
08/ 502,732
July 14, 1995
The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.