Efficient preamble scheme for burst-mode detection in coherent TFDM-PON

Abstract

Coherent technology is a promising solution for the future passive optical networks (PONs) to meet the demand for higher bandwidth. Recently, time and frequency division multiplexing (TFDM) PON based on digital subcarrier multiplexing (DSCM) has attracted increasing interest due to its flexible bandwidth allocation and notably low latency advantages. However, upstream burst-mode detection is a critical challenge when adopting a coherent TFDM PON system. To accelerate digital signal processing (DSP) convergence with a minimal preamble length, we propose an upstream system scheme and an efficient burst-mode preamble design. The scheme employs single-polarization and residual carrier modulation combined with specialized spectrum allocation to reduce the cost and shorten the preamble length. The designed preamble uses the same training unit to jointly implement frame synchronization, fine frequency offset estimation (FOE), polarization compensation, and channel estimation. This integration significantly reduces the preamble length. The design is experimentally verified in a 200-Gb/s TFDM upstream transmission over 20-km standard single-mode fiber (SSMF). Using a 20.48-ns preamble with 256 training symbols (TS), a receiver sensitivity of approximately −27 dBm is achieved at the bit error rate (BER) threshold of 1 × 10 −2 .