Quantum input-output relations for a generic n-port ring cavity are
obtained by modeling the ring as a cascade of n interlinked beam splitters.
Cavity response to a beam impinging on one port is studied as a function of the
beam-splitter reflectivities and the internal phase-shifts. Interferometric
sensitivity and stability are analyzed as a function of the number of ports.Comment: 6 pages, 5 figures (low-res