Optical port
= Optical port
An <optical port> specifies where and in which direction a beam enters or leaves an <optical instrument>. To attach one <complex amplitude> to it, also specify the beam's transverse field profile, <electromagnetic polarization>, <frequency> and reference plane for <wave phase>. Reversing propagation changes the input/output assignment. Four geometrical connections do not imply four independent input <complex amplitudes> in the chosen two-input configuration.