Multi-port technology for microwave and optical communications

In this work some of the latest advances in multi-port technology in microwave and optical frequencies are reviewed. At microwaves frequencies, multilayer technologies are clearly improving the capabilities of six-port networks designs to cover wider frequency bands with minimum imbalances. This is making feasible new applications such as ultra-wideband phase shifter-less frequency discriminator. However, it is in the optical communications field where multi-port networks have become the preferred option for coherent receiver implementation. Recently, six-port based optical coherent receivers have started to be commercialized and there are promising studies that demonstrate how five-port networks can even enhance the performance of such receivers in the next generation of optical coherent receivers.