A compact 4 × 10-Gb/s CWDM ROSA module for 40G Ethernet optical transceiver

For 40GBASE-LR4 application, we designed and fabricated a 4 × 10-Gb/s CWDM receiver optical sub-assembly (ROSA) module integrated with a collimator, an optical demultiplexer (DMUX), and a TO part. The TO part includes focusing lenses, photodiodes (PDs), transimpedance amplifiers (TIAs), and high-speed TO header. The optical DMUX has insertion loss of −1.2 dB and adjacent crosstalk of less than 30 dB. The focusing lenses in the TO part show aspherical lens shape and provide high alignment tolerance of more than ±300µm for single and array lens types. Especially, electrical crosstalk was less than −40 dB and optical crosstalk was negligible in the TO part. The developed 4 × 10-Gb/s ROSA module shows 3-dB OE bandwidth of about 9.1 GHz GHz and an average receiver sensitivity of −17.7 dBm for four channels at extinction ratio of 6 dB and bit error rate of 10⁻¹².