Improvement of cascaded semiconductor optical amplifier gates by using holding light injection

The cascadability of semiconductor optical amplifier (SOA) gates by using holding light injection is numerically and experimentally investigated. Our experimental results show that the signal bit error rate after two cascaded SOA gates will be larger than 10/sup -9/ without holding light injection; however 11 SOA gates can be cascaded with holding light injection. The results show that the number of cascaded SOA gates by using holding light injection can be strongly increased.