Multi-band CAP for Next-Generation Optical Access Networks Using 10-G Optics

40-Gb/s/λ multi-band carrierless amplitude and phase (CAP) modulation long-reach passive optical networks were demonstrated using 10-G class transceivers only. A major issue of multi-band CAP is that it is vulnerable to timing error, and this work has offered quantitative analysis about it in detail for the first time. A novel simple timing recovery approach, partial differential quadrature amplitude modulation constellation encoding and decoding schemes together with blind multimodulus algorithm equalization are proposed to address the issue efficiently, enabling zero-overhead signal recovery. Results show that it can offer excellent system tolerance to timing error of at least ±0.1 symbol period even for the highest frequency CAP sub-band. The characteristics of the transceiver are measured, and optimization of critical system parameters is performed including the CAP sub-band count, 10-G Mach–Zehnder intensity modulator operation conditions, optical launch power, and wavelength offset asymmetrical optical filtering. For downlink using erbium-doped fiber amplifier preamplifiers, successful 40-Gb/s multi-band CAP signal transmission over an 80-km (90-km) single-mode fiber is achieved with a link power budget of 33 dB (29 dB) considering a forward error correction threshold bit error ratio of 3.8 × 10−3.