In quantum optics, are fiber beam splitters described by the same operators as free space beam splitters?
For example, a free-space non-polarizing beam splitter introduces a phase shift for the reflected component. Is it still true for a 2x2 fiber optic coupler? If it is, how do we know which output fiber corresponds to the transmitted component and which to the reflected component?
And is the same operator used for a free-space polarizing beam splitter and for a fiber-based polarization beam splitter?