Demonstration of optical duobinary transmission system using phase modulator and optical filter

We experimentally demonstrate an optical duobinary transmission system employing a phase modulator and a narrow-bandwidth optical filter. Compared to the conventional duobinary signal generated by using an electrical low-pass filter, the demonstrated duobinary signal 1) provides improved receiver sensitivity; 2) overcomes the problem associated with word lengths; and 3) substantially relaxes the performance sensitivity to the driver and modulator response, while maintaining narrow spectral bandwidth and high dispersion tolerance.