LAUSR

Abstract For fully utilizing the system frequency response of optical intensity-modulation and direct-detection (IM/DD) passive optical network (PON) transmission system, this paper demonstrates a novel adaptive quadrature amplitude modulation (QAM) encoder /decoder for bit and power loading based on adaptively modulated orthogonal frequency division multiplexing (AM-OFDM). The applied adaptive QAM encoder/decoder supports all the M-QAM formats on each sub-carrier instead by ranging the order of modulation format on different sub-carriers. Simulation results show that the adaptive QAM coder/decoder can be used for variable transmission channel with different transmission distances between optical line terminal (OLT) and optical network units (ONUs). Meanwhile, the margin-adaptive loading algorithms minimizes the bit error rate (BER) for a given bit rate. In addition, compared the fixed 16QAM scheme, the receiver sensitivity performance of the adaptive QAM scheme is improved by 5.2 dB for 30 km standard single-mode fibre (SSMF) transmission at the -8.12 dB m received optical power (ROP).