Vernier Multicore Optical Fiber Sensors Optimized for Curvature Sensing

Implementing the Vernier effect in optical fiber sensors (OFSs) provides an enhanced sensitivity by cascading two interferometric devices. Despite the attractive advantages of Vernier sensing approaches, a formal analysis of the conditions required for optimizing their performance has not been fully addressed. Herein, we show that given an operational bandwidth (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {\lambda }_{\text {op}}$ </tex-math></inline-formula>), a Vernier configuration can be properly designed with a spectral shift (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {\lambda }_{\text {V}}$ </tex-math></inline-formula>) that matches the experimental operational bandwidth. To demonstrate our optimization approach, we use highly coupled multicore fibers (MCFs) as building blocks for constructing a Vernier arrangement for curvature sensing. Our results show that the MCF sensing devices are ideal for optimizing the performance of a Vernier arrangement, as demonstrated for a curvature range from 0 to1.58 m−1. For a targeted spectral shift of 200 nm, we achieved a blue shift of 206 nm. Moreover, a similar spectral shift toward longer wavelengths was obtained by simply exchanging the positions of the fiber devices. This approach using MCF-based Vernier configurations can be further extended to optimize the performance of temperature, pressure, and refractive index fiber sensors.