High extinction switching of SOAs for in-band crosstalk reduction in PON

Burst-mode operation in next-generation large-split, long-reach 10 Gbit/s passive optical networks (PONs) poses challenging requirements on optical network unit (ONU) design. One critical requirement in high-split networks is to suppress the ONU off-state emissions sufficiently to prevent penalties arising from in-band crosstalk. Proposed and demonstrated is the use of semiconductor optical amplifiers (SOAs) to provide this high-extinction ONU gating function. A novel experimental technique for accurate characterisation of the dynamic extinction introduced by the SOAs is described, which is based on the bit error rate penalty induced by the interference from the SOA off-state emissions. The experimental results indicate that the proposed ONU design can allow the operation of PONs with 512-way splits.