Signal Encoding for Fiber-Optic Link
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Communication Controllers are made to enable digital processors to communicate over high-speed communication links using fiber-optic cables. Assuming an HDLC data stream is being generated, then means should be provided to enable recovering, at the receiving end, a clock signal (RC) correctly synchronized with the data (RD). A solution is provided here which applies NRZI coding to an HDLC data stream. A clockless, NRZI, transmission coding is used which offers twice the data, for a given bandwidth, compared to usually used coding for fiber-optic data links. The HDLC protocol defines the start and end of an information frame by a "flag" consisting of six consecutive "1" bits. If, in the frame, there is a succession of "1" bits to be transmitted, a "0" bit is inserted after five consecutive "1" bits.