Planar lightwave circuit six-port technique for optical measurements and characterizations

The six-port approach is a well-established technique at microwave frequencies, where it has been extensively used as a simple and accurate means to measure complex reflection coefficients with a simple setup. However, its possible application at optical frequencies has not been sufficiently investigated. In this paper, a simple architecture to construct an optical six-port with a planar lightwave circuit (PLC) based on multimode interference (MMI) couplers is proposed for the first time. The proposed PLC is simulated, and the obtained results show a promising performance of the circuit in a wide wavelength range. This novel architecture will allow, in the near future, extending the successful six-port measurement technique up to optical frequencies.