Load-balanced adaptive routing flexible grouping spectrum and core assignment in SDM-EONs based on mixed super-channel

•The effective load balancing is achieved by genetic algorithm-assisted offline/online weight-updating strategies.•The fragmentation suppression is realized with less than half of the previous complexity and no transmission disruption.•More than 80% of spectrum fragments are suppressed due to the flexible-grouping mechanism.•The service blocking probability is kept as zero when the traffic load is lower than 300 Erlang in NSFNET and USNET.•The quality of service (QoS) of transmission requests with high priority is greatly enhanced.