An in-line in-fibre ring cavity multi-parameter sensor with a tuneable refractive index response

摘要

An in-line fibre ring cavity is fabricated by writing two blazed gratings next to each other to form a Fabry Perot cavity. A visibility of fringes as good as 0.032 in the reflection spectrum and 0.76 for transmission is obtained for the interference between the forward propagating guided mode and the reverse propagating ghost mode of the blazed grating. The ability to measure the external refractive index and the variability of this response with cavity length is demonstrated.