BER CHARACTERISTICS OF PI 4 DQPSK MICROWAVE SUBCARRIER SIGNALS ON OPTICAL-FIBER USING MACH-ZEHNDER MODULATOR NONLINEAR UP-CONVERSION/

The nonlinear transfer characteristic of a Mach-Zehnder modulator is u tilized to up-convert an unmodulated electrical input signal at 4.1 GH z and a pi/4 DQPSK modulated signal at 5.1 GHz to produce an unmodulat ed optical subcarrier at 16.4 GHz and a pi/4 DQPSK modulated optical s ubcarrier at 17.4 GHz. Using a dc biased laser source at 1551 nm, the up-converted 50 Mbs pi/4 DQPSK optical subcarrier at 17.4 GHz is trans mitted over up to 50 km of standard single-mode fiber and its BER is m easured. The experiment demonstrates that the BER is measured. The exp eriment demonstrates that the BER performance is degraded by less than 1 dB (electrical) by the optical up-conversion scheme.