Digital processing in the optical communications

Digital processing role in the optical communications is analyzed together with its historical evolution and perspectives. If optical systems at their early stage included weak digital processing in the electrical domain, a fast evolution towards completely all-optical technologies arises due to the bottleneck caused by the electronics bandwidth limitation. With the return of coherent communications, digital processing migrated again back to the electronic domain. Nowadays, algorithm complexity capable of mitigating for linear and nonlinear fibre impairments is becoming unsustainable due to huge level of parallelization and power demand. For such a reason one possible evolution will include processing both in the electronic and optical domain.