In this paper we review recent developments in multicore optical fibers with continuous gratings suitable for various distributed sensing applications including shape, temperature, strain and acoustic signals. We describe an integrated optical fiber assembly for shape sensing. Our shape sensor module consists of a length (>1m) of twisted multicore optical fiber with fiber Bragg gratings inscribed along its length. Our fiber has a compact 200 micron coated diameter, a twist of 50 turns per meter and grating reflectivities greater than 0.001% per cm of array, suitable for high efficiency scatter measurements over many meters of fiber. Multicore fiber splicing with an OFS Fitel splicer is also demonstrated. A UV transparent coating protects the fiber at near pristine mechanical strength, while allowing for reel to reel processing during grating inscription without stripping the coating. We then demonstrate a shape reconstruction algorithm with the fiber to obtain various shapes using only the core reflected light. Finally, we describe enhanced Rayleigh-like scattering fibers with spatially continuous scattering over a large optical bandwidth, suitable for improved distributed strain, temperature and acoustic sensing using interrogator algorithms that traditionally use fiber Rayleigh backscattering.
