On the capacity improvement achieved by bandwidth-variable transceivers in meshed optical networks with cascaded ROADMs

We investigate the capacity improvement achieved by bandwidth-variable transceivers (BVTs) in fiber links with cascaded reconfigurable optical add and drop multiplexers (ROADMs). It is shown that BVTs with flexibilities in both symbol rate and spectral efficiency enable one to optimize capacity by balancing optical filtering tolerance and signal required signal-to-noise ratio (SNR). Compared with a fixed symbol rate transceiver with standard quadrature amplitude modulations (QAMs), BVTs can increase average capacity by up to 17% in both simulations and experiments.