A Regenerative Variable Optical Buffer for NRZ and RZ Packets

We demonstrate a regenerative variable optical buffer suitable for both non-return-to-zero and return-to-zero intensity-modulated packets. The buffer is based on a re-circulating fiber loop that exploits a regenerative amplification stage based on cross-gain-compression in a semiconductor optical amplifier. This buffer does not suffer from any transient effect at the packets' edges, and due to its working principle, can be used for packets of different length. We report experimental results showing the buffering operation of 1-s long 10-Gbps packets up to 100 circulations (making possible a maximum buffering time of 130 s) with a bit error rate showing 0.5 dB power penalty every 10 rounds. The case of the buffering of noisy packets is also investigated. We find that because of the regenerative feature of the amplification stage, packets with different input noise levels show a similar quality at the output. In particular, signal regeneration is possible up to certain buffering times and depends on the input noise values.