A 0.155, 0.622, and 2.488 Gb/s automatic bit rate selecting clock and data recovery IC for bit rate transparent SDH-systems

Optical data transmission is inherently bit rate transparent, i.e., a bit signal can be transmitted regardless of its bit rate. The bit rate transparent part of a network, the all-optical part, allows flexible routing which can be used to combine and reconfigure network parts with different bit rates, to reconfigure the network because of varying loads or defects and to offer flexible access for service providers. However in the electronic part of the system a conventional clock and data recovery circuit (CDR) prohibits bit rate transparent operation, as it operates only at the bit rate it is designed for. This circuit represents a bit-rate transparent single-chip CDR for SDH-systems. The design comprises a bit rate detection circuit for automatic bit rate selection and a fully-integrated CDR for bit rates 0.155, 0.622 and 2.488Gb/s. The chip meets SDH specifications for the three bit rates.