Supermode Bragg Grating Inscribed in a Strongly Coupled Seven-Core Fiber for Multi-Parameter Sensing Applications

A supermode Bragg grating inscribed in a strongly coupled seven-core fiber (SCF) for multi-parameter sensing is proposed and demonstrated. There are two Bragg resonance notches observed in the transmission spectrum, corresponding to HE11-like and HE12-like supermodes of the SCF. Since the SCF is spliced between two standard single mode fibers with central alignments at both ends, the transmission spectrum of the device also contains an interferometric profile due to the Mach-Zehnder interference of the supermodes. The responses of the device to temperature and strain are experimentally characterized, respectively. The interference spectrum and the grating spectrum exhibit different responses to strain and temperature. This device is potentially useful for simultaneous measurement of temperature and strain.