Bidirectional OFDM-MMWOF transport system based on mixed QAM modulation format using dual mode colorless laser diode and RSOA for next generation 5-G based network

Abstract

A hybrid bidirectional orthogonal frequency division multiplexing–millimeter wave over fiber (OFDM-MMWOF) transport system based on mixed quadrature amplitude modulation (QAM) format using dual-mode colorless laser diode and reflective semiconductor optical amplifier for next-generation 5G based networks is proposed and experimentally demonstrated. Here, an orthogonal quadruple frequency MMW is generated via optical heterodyne scheme. In case of downlink transmission, 10 Gbps baseband signal is transmitted over 80-km single-mode fiber (SMF) plus 500-m free space optical (FSO) distance and for the uplink, 5 Gbps baseband signal is transmitted over 80-km SMF plus 100-m FSO distance. For wireless transmission, 12.5 Gbps/60 GHz downlink MMW signal is generated and transmitted over 80-km SMF as well as 100-m wireless distance. 6.5 Gbps/30 GHz uplink MMW signal is communicated over 80-km SMF plus 50-m wireless distance. OFDM scheme with mixed QAM modulation technique enhances our spectral efficiency and simultaneously reduces inter symbol interference, inter-carrier interference, dispersion, etc. for long reach communication. The feasibility and reliability of our system is established by achieving low bit error rate (10-3), good error vector magnitude (<10.5% for 32 QAM and < 12.5% for 16 QAM), appropriate signal to noise ratio, and clear constellation diagram.