Enhanced chromatic dispersion tolerance of 11 Gbit/s RSOA-based WDM PON using 4-ary PAM signal

For the cost-effective realisation of the next-generation wavelengthdivision-multiplexed passive optical network (WDM PON), the possibility is evaluated of using the 4-ary pulse-amplitude-modulated (PAM) signal for the high-speed (> 10 Gbit/s) operation of the TOcan packaged reflective semiconductor optical amplifier (RSOA) having a 3 dB bandwidth of only about 2.2 GHz. The results show that, owing to the compact spectrum of the 4-ary PAM signal, the deleterious effects of this limited bandwidth as well as the sensitivity degradations caused by the chromatic dispersion can be significantly alleviated. As a result, an error-free transmission of 11 Gbit/s, 4-ary PAM signal over 20 km of singlemode fibre can be demonstrated.