40 Gb/s duobinary and modified duobinary transmitter based on an optical delay interferometer

We present a novel 40 Gb/s duobinary and modified duobinary transmitter design based on differential phase shift keying (DPSK) and an optical one-bit-delay interferometer. Using this transmitter design, we demonstrate experimentally 40 Gb/s modified duobinary transmission over 2,000 km with a bit error ratio (BER) of 1x10^-8 without using forward error correction (FEC).