Design and evaluation of a reconfigurable optical add-drop multiplexer with flexible wave-band routing in SDM networks

Abstract

Space-division multiplexing (SDM) is expected to increase the capacity of photonic networks. Reconfigurable optical add-drop multiplexers (ROADMs) for SDM-based networks must have high scalability in terms of port count. However, the ROADM architecture adopted in present networks cannot support large numbers of ports due to the limited port count of wavelength-selective switches. In this paper, we propose a ROADM architecture composed of space switches and wavelength-routing switches. Space switches have lower per-port cost than wavelength-routing switches. However, space switches cannot route optical paths on a wavelength basis, unlike wavelength-routing switches. By combining these two types of switches, the ROADM port count can be cost-effectively expanded virtually unlimitedly. Numerical simulations show the routing performance of our ROADM; they elucidate that the maximum fiber increment penalty is about 5% compared to the reference scheme. Experiments detail the transmission performance of the ROADM, where 32 Gbaud DP-4QAM/8QAM/16QAM signals are aligned on a 50 GHz grid, are examined.