Composed multicore fiber structure for direction-sensitive curvature monitoring

Abstract

The present work deals with a curvature sensor that consists of two segments of asymmetric multicore fiber (MCF) fusion spliced with standard single mode fiber (SMF). The MCF comprises three strongly coupled cores; one of such cores is at the geometrical center of the MCF. The two segments of MCF are short, have different lengths (less than 2 cm each), and are rotated 180° with respect to each other. The fabrication of the sensor was carried out with a fusion splicing machine that has the means for rotating optical fibers. It is demonstrated that the sensor behaves as two SMF–MCF–SMF structures in series, and consequently, it has enhanced sensitivity. The device proposed here can be used to sense the direction and amplitude of curvature by monitoring either wavelength shifts or intensity changes. In the latter case, high curvature sensitivity was observed. The device can also be used for the development of other highly sensitive sensors to monitor, for example, vibrations, force, pressure, or any other parameter that induces periodic or local curvature or bending to the MCF segments.

Mode-division and spatial-division optical fiber sensors

“…Phase-shifted modal interferometers. The concept of phase-shifted modal interferometers was introduced in 2020 [134,140,141]. The idea consists of placing two supermode interferometers in series, but the interferometers must have a proper difference in their lengths.…”

“…Moreover, intensity changes can be monitored at high speed with a suitable photodetector. Phase-shifted supermode interferometers are suitable for sensing vibrations, acoustic waves, or any event that may bend one interferometer [41,141].…”

Ratiometric Temperature Sensing Using Highly Coupled Seven-Core Fibers

“…In recent years, an increasing interest has been demonstrated in implementing multicore fibers (MCFs) in fiber sensing systems [ 1 , 2 , 3 ]. Measurements and detection in deformation [ 4 , 5 , 6 , 7 , 8 ], refractive index [ 9 , 10 , 11 , 12 ], temperature [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], curvature [ 22 , 23 , 24 ], vibration [ 25 ], and polarization state [ 26 ] have been reported using MCF devices. MCFs have been described as revolutionary waveguides, as these fibers have allowed new alternatives for developing sensing systems whose performances cannot be easily achieved using conventional fiber optics [ 22 ].…”

Twin-core fiber sensor integrated in laser cavity

“…The spectral overlap of the broad peaks of C-band sensors generally constrains their use to single point measurements. To overcome this limitation, efforts such as cascading MCF segments have been made, at the expense of increasing the complexity and length of the sensor 26 , 27 . Anyhow, due to the attractive features of coupled MCF-based sensors, it would be of interest to develop a technique to improve their spectral efficiency and allow for multiplexing, making it possible their use as multipoint sensors for applications such as structural health monitoring.…”