Highly sensitive and simple method for refractive index sensing of liquids in microstructured optical fibers using four-wave mixing

Temperature-insensitive refractive index sensing by use of micro Fabry–Pérot cavity based on simplified hollow-core photonic crystal fiber

“…However, such a sensor can only use the liquids with a RI higher than that of silica (∼1.46). To operate at around 1.33 of RI, a liquid-filled PCF sensor based on four-wave mixing has been demonstrated, with a high sensitivity of 8800 nm∕RIU, however, a large length of PCF (∼1 m) has to be used [11].A key issue that existed in the above mentioned configurations is temperature cross-sensitivity because it limits the sensor reliability. One of the solutions to this issue is the use of fiber-optical FP cavity as it exhibits very low temperature sensitivity of ∼1 pm∕°C, due to the small thermo-expansion coefficient of silica.…”

“…However, such a sensor can only use the liquids with a RI higher than that of silica (∼1.46). To operate at around 1.33 of RI, a liquid-filled PCF sensor based on four-wave mixing has been demonstrated, with a high sensitivity of 8800 nm∕RIU, however, a large length of PCF (∼1 m) has to be used [11].…”

“…To date, most of optical fiber RI sensors are based on fiber Bragg grating (FBG) [1], long-period fiber grating (LPFG) [2,3], FabryPérot (FP) or Mach-Zehnder interferometer [4,5], microfiber [6], selectively infiltrated photonic crystal fiber (PCF) coupler [7,8] and many other interesting structures [9][10][11].…”

Label-free optical biosensor based on a dual-core microstructured polymer optical fiber

“…In addition, MOF based sensors have achieved considerable attention especially in the context of labelfree fiber-optic biosensing, in which biomolecules does not require the sample to be marked with fluorescent dyes but rather relies on the detection of tiny refractive index changes due to bonding events, e.g., with antibodies or antigens. Rindorf et al experimentally demonstrated a sensitivity of 1.4 nm shift of a long-period grating resonance per nm biolayer (1.4 nm/nm) [7], and Ott et al [21] theoretically demonstrated a sensitivity of 10.4 nm/nm using the inherent nonlinearity of the photonic crystal fiber (PCF) for Four-Wave-Mixing (FWM)-based label-free biosensing, and thus an experimental work on using the inherent material nonlinearity of the fiber in a FWM sensing scheme has been investigated [22].…”

Nonlinear fiber-optic strain sensor based on four-wave mixing in microstructured optical fiber

“…The fiber-optic FWM sensor technology can offer high sensitivity due to the extreme sensitivity of FWM to the dispersion profile [7] and it does not require fiber postprocessing. It was recently verified that highly sensitive refractive index sensing, and thus also biosensing, can indeed be achieved with the FWM technique [6,8].…”