Benefits and requirements of flexible-grid ROADMs and networks [invited]

Due to claims of enhanced spectral efficiency and the ability to accommodate future modulation formats, flexible-grid networks in which the center wavelength and passband width of the optical channels can be set on the fly have attracted wide attention. A flexible-grid reconfigurable optical add/drop multiplexer (ROADM) requires more than a flexible-grid wavelength-selective switch, and a flexible-grid network requires far more than flexible-grid ROADMs. We discuss the technologies required to enable flexible-grid networks. We examine the potential benefits of using flexible-grid ROADMs and compare this approach with alternative strategies.