Subcarrier Multiplexing Based Transponder Design

Abstract

This thesis presents the design and demonstration of high-speed transponders using analogue implemented subcarrier multiplexing (SCM) technique to simplify digital signal processing (DSP) for different applications. A 144-Gb/s filter bank multicarrier (FBMC) transceiver is numerically demonstrated for 2-km standard single mode fibre (SSMF) transmission. Without nonlinear or chromatic dispersion (CD) compensation nor channel equalization, the FBMC system outperforms the orthogonal frequency division multiplexing (OFDM) counterpart, and the transmission penalty for the 8-subcarrier FBMC system is 2.4 dB. For amplifier-free 80-km transmission, a 134-Gb/s coherent transceiver utilizing heterodyne detection and doubly differential (DD) quadrature phase shift keying (QPSK) is numerically demonstrated. Without CD compensation nor carrier recovery, transmission penalty and performance degradation for frequency offsets within ±2 GHz is negligible. To further improve interface rate, a 200-Gb/s DD QPSK transceiver using hybrid-assisted tandem single sideband (TSSB) modulation and digital coherent detection is numerically verified. However, guard bands and QPSK used in both transponders result in low spectral density, and conventional DD decoding degrades receiver sensitivity by 7 dB. To overcome these problems, a 209-Gb/s coherent transponder utilizing DD two amplitude/eight-phase shift keying (2ASK-8PSK) and 11-tap multi-symbol DD decoding is experimentally demonstrated, with an implementation penalty of 5.9 dB and a performance penalty of 1 dB for 100-km transmission. For long-haul application, a 62-GBaud SCM 16-ary quadrature amplitude modulation (16QAM) transceiver employing a single in-phase quadrature (IQ) mixer, simple transmitter-side DSP, and sub-band detection is demonstrated, giving spectral efficiency of ~2.7 b/s/Hz/polarization and OSNR penalty of 6.6 dB. By resorting to hybrid-assisted TSSB modulation, the aggregate symbol rate of the SCM transmitter is improved to 86 GBaud. With sub-band coherent detection and a 31-tap multi-input multi-output (MIMO) equalizer, an implementation penalty of 2 dB and spectral efficiency of ~3.6 b/s/Hz/polarization are achieved.