Effect of input-output coupling on the sensitivity of coupled resonator optical waveguide gyroscopes

We analyze how the evanescent coupling, κ_e, between the outermost resonators and input/output waveguides of an N-resonator coupled resonator optical waveguide (CROW) gyroscope affects the transmission and sensitivity to rotations. For constant coupling between resonators κ, rotation sensitivities increase as both κ_e → 0 and κ_e → 1 while between these two limits the sensitivity has a minimum. In the weak coupling regime, κ_e → 0, the sensitivity is enhanced by Fabry-Perot oscillations due to the impedance mismatch at the input/output waveguide-CROW interface, while in the strong coupling regime, κ_e → 1, the sensitivity is reduced because the outermost resonators no longer contribute to the CROW transmission. For small N the sensitivity is proportional to N², while at larger N the sensitivity begins to decrease due to resonator losses.