Current status of micro- and nano-structured optical fiber sensors

Recently developed micro- and nano-structured optical fiber sensors, with particular reference to surface plasmon resonance (SPR) fiber sensors and photonic crystal fiber (PCF) sensors are reviewed. SPR fiber sensors can have diverse structures such as D-shape, cladding-off, fiber tip or tapered fiber structures. Some of the recently developed novel structures include the use of various types of fiber gratings in SPR fiber sensors. PCF sensors cover diverse recent developments on photonic-bandgap fiber, holey fiber, hole-assisted fiber and Bragg fiber sensors. Major applications of these include gas sensors and bio-sensors. These micro- and nano-structured fiber sensors have attracted considerable research and development interest, because of their distinct advantages, which include high sensitivity, small sensor head footprint and the flexibility of the optical fibers. They are also of academic interest, and many novel ideas are continuously developed.