WDM–TDM NG-PON Power Budget Extension by Utilizing SOA in the Remote Node

Today, even in access networks, data traffic is enormously increasing, a trend that causes existing passive optical network (PON) infrastructures to become bottlenecks in a tele- and data-communication infrastructure, which is aimed to be both broadband and seamless. Thus, two major objectives are considered for next-generation PONs (NG-PONs), i.e., first, bandwidth increase, and second, reach extension to reduce deployment costs. Here, we describe a new reach extension scheme that at the same time allows increasing the number of subscribers in the network. The amplification technique is based on a bidirectional semiconductor optical amplifier (SOA). It is shown that the extender configuration not only meets the bandwidth and budget requirements for NG-PONs but also remarkably improves them. Differential (quadrature) phase-shift keying (D(Q)PSK) signals are investigated in this paper. Hybrid wavelength-division multiplexing/time-division multiplexing (WDM/TDM) transmission up to 120-Gb/s downstream and 40-Gb/s upstream are experimentally demonstrated. The access budget of 33.4 dB is achieved at 10 Gb/s on every WDM channel in case of DPSK enabling a splitting ratio of 1:512 per wavelength. Furthermore, optical power budget of 40 dB is obtained when DQPSK is used, where a splitting ratio of 1024 per wavelength can be supported. Additionally, a cost-efficient chirped managed directly modulated laser scheme is proposed for DPSK signal generation in U.S. scenario enabling a high-power budget performance low-cost transmitter configuration, which appears suitable for NG-PON application. The proposed technique also alleviates nonlinear impairments [specifically, cross-phase modulation (XPM)], which appear in dense WDM transmission.