DQPSK optical packet switching using an SG-DBR laser

In this paper we demonstrate a 10.7 Gbaud DQPSK transmission system employing an SG-DBR transmitter, our laser is a simple butterfly packaged device without a wavelength locker, microcontroller or other circuitry. The back mirror current was biased to operate with single mode static operation at wavelengths 1553.54 nm and 1547.3nm respectively. A dual parallel Mach Zehnder (DPMZ) modulator (biased close to the null points) was driven by the complementary PRBS outputs of a 10.7Gb/s Pulse Pattern Generator (PPG) decorrelated by 12 bits using an electrical delay. A 10.7Gb/s one-bit-delay interferometer was implemented at the receiver side to differentially demodulate the in-phase or quadrature data independently. The BER was calculated separately for the I and Q components of the received signal at each wavelength as shown. Receiver sensitivities of between -29dBm and -30dBm at a BER of 1x10^-9 were observed for I and Q on each channel.