High speed pseudo-random binary sequence generation for testing and data scrambling in gigabit optical transmission systems

Pseudo-random binary sequences (PRBS) have many applications in digital and RF communication systems. This paper describes the techniques used to build a sequence generator operating at up to 2.5 Gbit/sec. The unit has been developed for use in the testbed of RACE Project 1036 to provide signals for DFB lasers in a 16 channel wavelength and time division multiplexed (WTDM) optical network. The sequences will be used to drive twelve laser modules transmitting optical signals at wavelengths adjacent to four active channels in the test bed which carry multiplexed data corresponding to the STM-16 level (2.5 Gbit/sec) of the CCITT synchronous digital hierarchy (SDH). This will allow optical and electrical crosstalk measurements to be made and the performance of a fully populated optical network to be assessed. This paper shows that at gigabit/second data rates it is advantageous to generate these sequences as a parallel word and then perform parallel to serial conversion in order to minimize the amount of logic operating at high data rates