Reconfigurable optical frequency comb and its applications

The concept of wavelength division multiplexing (WDM) has revolutionized the field of optical communications. However, the immense demand for bandwidth shows no sign of abating and is pushing service providers to deploy communication networks with increased capacity. Optical transport networks will soon require channel data rates in excess of 100 Gb/s in order to continue to meet the ever increasing demand for bandwidth. Bandwidth flexible optical networks, that dynamically adjust transmission parameters and allocate the bandwidth according to the traffic demands, have been proposed in the literature to support 400 Gb/s and 1 Tb/s super channels [1]. In such systems, techniques including coherent optical OFDM and Nyquist WDM transmission [2] may be employed to achieve channel spacing at or close to the symbol rate. These high capacity transmission systems are well served by optical frequency comb (OFC) sources that can enable the reduction or elimination of guard bands by featuring fixed frequency spacing between the carriers, in contrast to arrays of independent lasers that do not. Moreover, an OFC that offers wavelength and free spectral range (FSR) tunability allows a single source to be easily adapted. Hence, in order to be successfully employed in such flexible systems, OFC sources should exhibit good spectral flatness, high frequency stability, low linewidth, and reconfigurable central wavelength and FSR. In this work, the authors present a reconfigurable gain switched optical frequency comb [3–5] and demonstrate its optimum features. In addition, several applications of this comb will be reviewed [6, 7].