Performance assessment of interleaver filters for next-generation mobile transport

The evolution of passive optical networks (PONs) is rapidly progressing, with the next generation aiming to surpass 100Gb/s/λ and target 200Gb/s/λ—a typical fourfold increase over the current 50Gb/s/λ power splitter (PS)-based PON standard. This paper outlines current research and development challenges in PONs and explores potential advancements using programmable photonic Nyquist-shaped Interleaver (NS-INT) filters paired with coherent point-to-multipoint (P2MP) digital subcarrier multiplexing (DSCM) transceivers. Specifically, we evaluated, based on analytical estimations and simulations, two NS-INT implementations for mobile transport: one based on ring resonators-assisted filters and a second utilizing an optical 18-tap cascaded asymmetric Mach–Zehnder Interferometer (aMZI). We compare their effectiveness in optimizing filtering and minimizing crosstalk (XT) across various coupling coefficient scenarios. Furthermore, we assess the feasibility of these designs by examining their performance under XT and signal impairment caused by filter narrowing effects, particularly in the presence of signal-to-filter center frequency misalignment. Bit error rate (BER) evaluations demonstrate a tolerance to frequency misalignments of up to 3 GHz across all architectures. Among them, our cascaded aMZI design exhibits superior performance, attributed to its inherent optical finite impulse response (FIR) filter characteristics as a minimum-phase filter.