Optical QPSK homodyne transmission of 280 Mbit/s

Future optical transmission systems in the multi-gigabit per second range have to consider the effects of fibre dispersion on the received optical signal. One way to overcome these problems is the use of higher bandwidth efficient modulation schemes. This paper presents the theory and first experimental results of an optical QPSK transmission system at a total bit rate of 280 Mbit/s. Instead of an optical 90 degrees -hybrid, a 3*3 fibre coupler and a signal processing unit in the electrical part of the receiver were used. The operation of the transmission experiment is illustrated by an oscilloscope pattern of the transmitter and receiver signals.