Two-dimensional optical fibre cantilever accelerometer

Focused Ion Beam (FIB) machining has been demonstrated to be capable of fabricating nano and micro scale elements onto optical fibres. In this paper we exploit FIB to fabricate core aligned 45° mirrors at the end of multi-core fibres (MCF). The resulting fibre is used as a component in a two dimensional optical fibre accelerometer. The mirror is produced using a two step process: first a scanning process is used to make a rough cut to define the overall mirror structure. This is followed by a polishing process to create an optical surface finish. The machined 45° mirror can be accurately aligned with optical fibre core, which avoids issues associated with the alignment of external turning mirror components. Proof-of-concept tests demonstrate the use of such a fibre as a two axis acceleration sensor that is interrogated interferometrically. The sensor operated between 0.5g and 4.5g with a cross talk of -24.3dB between axes.