Signal Remodulation of OFDM-QAM for Long Reach Carrier Distributed Passive Optical Networks

The passive optical network (PON) using orthogonal frequency-division multiplexing (OFDM) is a subject of many research works recently. The OFDM signal is especially good for long reach (LR)-PON due to its high tolerance to chromatic dispersion and high spectral efficiency. We study, for the first time, the possibility of using OFDM for signal remodulation in LR-PONs. Three different colorless optical networking unit (ONU) architectures, electroabsorption modulator-based, reflective semiconductor optical amplifier-based and injection-locked Fabry-Perot laser diode-based ONUs, are tested and compared. Error-free operations are achieved in 100-km fiber transmission without dispersion compensation.

I. Introduction

To economically sustain the growth of broadband services for end users, it would be required that the price of bandwidth reduces with volume at a rate which has not been achieved by any technology. Since the underlying optical components [e.g., lasers and optical receivers (Rxs)] cannot price decline at the required rate, the only answer to reduce the cost is to reduce the amount of equipment in the network. The long reach (LR) (100 km) passive optical network (PON) using dense wavelength-division-multiplexing (DWDM) technology is considered as a promising candidate for the future [1]–[3]. These LR-PONs can reduce the number of network elements and interconnection interfaces, and are predicted to significantly reduce the capital and operational cost. Although LR-PONs are as yet a research concept, the potential benefits they offer are such that they are a very worthy research topic [1]–[3].