1.25Gb/s WDM bi directional transceiver module using DFB-LD and PLC with spot-size conversion region

We have newly developed a 1.25 Gb/s WDM bi-directional transceiver module using a DFB-LD for broadband optical access network systems. In order to realize high optical output power, an optical coupling structure using a spot-size conversion (SSC) region for the Planar-Lightwave-Circuit (PLC) has been developed. Low LD-waveguide coupling loss of 6.5 dB has been attained without increasing PLC insertion loss, including fiber-waveguide coupling loss. We have confirmed that the transceiver module adopting an optical isolator-less structure achieves stable single mode operation and negligible power penalty for receiver sensitivity after 20 km transmission under the optical feedback level of up to -15dB.