Ultra-Narrow-Bandwidth Silicon Photonic Tunable Second-Order CROW Filter with Low Insertion Loss for Carrier-Extracted Self-Coherent (CESC) Detection

We demonstrate a silicon photonic tunable CROW filer with $1.26-\mathrm{GHz} 3-\mathrm{dB}$ bandwidth, $4.62-\mathrm{GHz} 20-\mathrm{dB}$ bandwidth, $4-\mathrm{dB}$ insertion loss and $60-\mathrm{dB}$ extinction ratio based on a $1-\mu \mathrm{m}$ width ridge waveguide. Applied in the CESC system, achieving a $168.3 \mathrm{~Gb} / \mathrm{s}$ transmission rate over 100-km SMF, the performance of this CROW filter is well verified.