Abstract
Next-generation access networks require provision of wireless services and high data rate to meet the huge demands for mobility and multiple services. Moreover, reusing the currently deployed optical distribution networks (ODNs) is highly beneficial and cost effective for providing the new high data rate wireless demands. In this paper, bidirectional radio over fiber passive optical network (RoF-PON) capable of handling multiple-input-multiple-output (MIMO) streams at low cost, high spectral efficiency and backward compatibility with currently deployed PUN, is proposed. To the best of our knowledge, all the existing RoF MIMO solutions have not considered compatibility with currently deployed ODNs. Eight laser diodes (LDs) at the central office (CO) are enough for the whole system, instead of having LD or optical transmitter at each remote antenna unit (RAU), which makes a colorless and cost-effective RAU. Twenty four wavelengths are generated using optical comb technique. Each two 16-QAM MIMO signals that have the same carrier frequency in the downstream (DS) transmission are optically combined using polarization-division-multiplexing (PDM), where each two upstream (US) MIMO signals are time division multiplexed. The PDM configuration doubles spectral efficiency with a power penalty of only 1.5 dB. The proposed architecture is a bidirectional asymmetric RoF-PON with total 40/10 Gb/s for DS/US transmission. Even after transmission over 20 km SMF and splitting ratio of 32, acceptable transmission performance and widely separated constellation diagrams for the 16-QAM signals are achieved, with bit error rate (BER) of 10(-6) for DS signals and 10(-3) for the US signals which can be reduced down to 10(-6) by using forward error correction (FEC). (C) 2015 Elsevier B.V. All rights reserved.