FREMONT, Calif. -- Optoplex Corporation recently shipped a highly customized differential quaternary phase-shift keying (DQPSK) demodulator to be utilized in a field trial for a next-generation 40 Gb/s fiber-optic transmission systems to be deployed by a major European service provider in 2007 and beyond.

Differential phase-shift keying (or DPSK) is touted as the most promising modulation format for optical communication systems, offering a 3-dB improvement in receiver sensitivity compared with standard on-off keying. The four-level version of DPSK, DQPSK, transmits two bits for every symbol, has an additional advantage over conventional binary DPSK in that it has a narrower optical spectrum, which tolerates more dispersion (both chromatic and polarization-mode), allows for stronger optical filtering, and enables closer channel spacing. As a result, DQPSK is the only modulation format which allows processing of 40Gb/s data-rate in a 50-GHz channel spacing system.

With DQPSK, the bandwidth of the drive electronics needs only be half of the bit rate, so 43 Gb/s signals can be generated with 21.5 Gb/s equipment. This allows system providers the expanded flexibility of reducing system cost by using low-speed drive electronics.

Optoplex’s DPSK and DQPSK demodulators are designed specifically for the next generation optical communication systems utilized by commercial, defense and space exploration markets.

Optoplex Corp.