Sensing characteristics of all-solid photonic bandgap fiber modal interferometers

Abstract

ABSTRACT We demon strate an all-solid photonic bandgap fiber modal interferometer by concatenating two tapers separated with a middle section of the fiber. U nlike the conventional devices , our structure has a lower effective index in the core and a higher effective index in the cladding , which produce novel sensing characteristics. The measured sensing sensitivities are ~63pm/ qC for temperarure and ~ 1.74nm/ N for the axial stress, respectively . Keywords: Modal interference, all -solid photonic bandgap fiber, sensor 1. INTRODUCT ION An o ptical fiber modal interferometer that allow s interference between two fiber modes with dissimilar effective mode indices is of great importance for the applications in both optical communication and sensing areas [1]. The devices are in general realized by excit ing different fiber modes with assistance of the long -period/titled Bragg gratings, abrupt fiber tapers, or connection of standard single -mode fibers to special fibers such as polarization maintaining or photonic crystal fibers [2]-[3]. Compa ratively, interferometers with tapers are appealing due to their advantages such as easy realization, relatively compactness, and high integration. Nowadays, the fiber taper interferometers are mainly constructed using the conventional or the index -guidin g photonic crystal fibers. In this work, we realize the interferometer using an all -solid photonic bandgap fiber (AS -PBF). Two abrupt tapers are separated with a middle section of the AS -PBF. Both the axial stress and temperature sensing characteristics ar e investigated.