Specialty Fiber Coupler: Fabrications and Applications

Abstract

We review the research on specialty fiber couplers with emphasis placed on the characteristics that make them attractive for biomedical imaging, optical communications, and sensing applications. The fabrication of fiber couplers has been carried out with, in addition to conventional single mode fiber, various specialty fibers such as photonic crystal fiber, double clad fiber, and hole-assisted fiber with a Ge-doped core. For the fiber coupler fabrication, the side polishing and the fused biconical tapered methods have been developed. These specialty fiber couplers have been applied to optical coherence tomography, fluorescence spectroscopy, fiber sensors, and optical communication systems. This review aims to provide a detailed statement on the recent progress and novel applications of specialty fiber couplers.

Optical Fiber Sensors: Working Principle, Applications, and Limitations

“…The interferometric fiber consists of a light beam splitter and a light beam combiner in any configuration. [53] In sensing applications, one of the optical path lengths is configured to be influenced by the external perturbations. The interferometric fiber detects quantitatively the perturbation by presenting a change in the wavelength, phase, intensity, frequency, or bandwidth.…”

Microsphere Coupled Off-Core Fiber Sensor for Ultrasound Sensing

“…These open-air cavity FPIs are typically fabricated through expensive and complex methods, such as fs laser micro-machining [ 14 ]. The sensing capabilities of these type of fiber optic sensors have been exploited and enhanced through new and old fiber optic technology innovations, such as fiber grating [ 15 , 16 , 17 ], surface plasmon resonance [ 18 ], and specialty fibers [ 19 ].…”

Interferometric Fiber Optic Sensors

“…Furthermore, their sensing abilities have been considerably enhanced by utilizing innovative fiber optic technologies of fiber gratings, fiber interferometers, Brillouin/Raman scattering, surface Plasmon resonance (SPR), micro-structured fibers, nano-wires, specialty fiber couplers, etc. [ 11 – 16 ]. Indeed, some fiber optic sensors are used for real time deformation monitoring of aircrafts, ships, bridges, and constructions [ 17 ].…”

“…A fiber optic interferometer uses the interference between two beams that have propagated through different optical paths of a single fiber or two different fibers. So, they require beam splitting and beam combining components in any configurations [ 16 ]. Of course, one of the optical paths should be arranged to be easily affected by external perturbations.…”