A. M. Khan's research while affiliated with Integral University and other places

The wavelength division multiplexing (WDM) technology is widely used in optical communication networks that provide bandwidth up to 10 Tbps, but these networks are unable to meet the emerging demands of heterogeneous, high, and flexible bandwidth traffic. To cater to these issues, elastic optical networks (EONs) have become the best solution for the torrent of flexible Internet traffic demands. In view of these, the advanced modulation format techniques such as BPSK, QPSK, and 16-QAM are used in EONs for the high-speed data transmission and the establishment of the lightpath (i.e., optical path between the source and the destination nodes) which is adjusted based on the client's need. In this paper, the broad review of literature has been presented and classifies the routing and spectrum allocation (RSA) problem in EONs with their main features and shortcomings. Apart from that, various aspects of fragmentation, modulation technology, quality-of-transmission, traffic grooming, survivability, energy savings, and network traffic scheduling are discussed in brief. Based on the thorough study, we identify the major research challenges which open huge opportunity for the researchers in the flexible technology-based EONs.