Signal processing is required in many types of photonic communication systems and networks - from on-chip data transfer to ultra-long haul transmission. As spectrally efficient modulation formats become more prevalent in these applications, advances in the requisite signal processing for transmitters and receivers are ever more important. This includes techniques for mitigating the effects of transmission impairments and non-ideal components/devices, key transmitter/receiver functions, forward error correction, and enabling technologies. Software defined networks, space division multiplexed systems, Tb/s superchannel systems, and broadband hybrid wireless-optical communication systems are of particular interest.