All-optical polarization-insensitive non-return-to-zero-to-pulsewidth tunable return-to-zero conversion

We demonstrate polarization-insensitive non-return-to-zero (NRZ)-to-pulsewidth tunable return-to-zero (RZ) conversion based on a Raman amplifier (RA)-based pulse compressor and a fiber-based NRZ-to-RZ converter, which consists of a polarization diversity loop. We measure the bit-error rate (BER) characteristics of the input NRZ signal and the converted RZ signals. The power penalty of less than 0.2 dB between the converted RZ signals with different power ratios proved the polarization insensitivity. Moreover, by changing the Raman pump power of the RA-based pulse compressor, the pulsewidths of the converted RZ signals were flexibly tuned from 10 to 2 ps, which proved NRZto-RZ conversion with pulsewidth tunability. In all cases, clear eye diagrams were obtained. (C) 2013 The Japan Society of Applied Physics