Evanescent wave long-period fiber grating within D-shaped optical fibers for high sensitivity refractive index detection

A review for optical sensors based on photonic crystal cavities

“…The measurement results can also provide guidance for some other sensors, such as biosensors, chemical sensors, mechanical sensors and gas sensors, in which the change of these measurement parameters can all be converted into RI variations. As for RI sensor, there are also some other optical systems, such as surface plasma resonance (SPR) [57], modal interference [58], evanescent wave [59], and Fabry-Perot (F-P) cavity [60]. In Table II, we have summarized the best values of detection limit and compared the advantages and disadvantages of these optical systems for their applications in refractive index measurement.…”

Long Period Gratings in New Generation Optical Fibers

“…To overcome this limits, we recently proposed a different approach to realize evanescent-wave D-fiber based LPGs (Quero et al, 2011). First of all, the D-fiber supplied by KVH (see Fig.…”

“…Recently, the same kind of evanescent-wave LPG -but PCF-based -has been proposed for SRI and temperature measurements demonstrating higher sensitivities as compared with conventional LPGs (H. Kim et al, 2011). As regards the more flexible evanescent-wave D-fiber based LPG recently proposed by us (Quero et al, 2011), it was characterized versus the SRI: Fig. 10(b) shows the wavelength shift of the attenuation bands located at ~1360 and ~1440 nm (see Fig.…”

Effects of surface roughness on optical properties and sensitivity of fiber-optic evanescent wave sensors

“…However, the sensitivity of FOEW sensors is directly affected by attenuation of the evanescent waves on the unclad fiber surface (sensing region) [7]. Different types of sensors based on variations in the shape of the unclad fiber region and fiber end region have been created to improve the sensitivity [8][9][10][11]. Pulido and Esteban [8] and Ahmad and Hench [12] discovered that the sensitivity of tapered fiber sensors depends on the radius of the fiber, taper waist length, and launch angle.…”

“…Gupta et al [9,13] and Prabhakar and Mukherji [14] investigated the dependence of the sensitivity on the fiber bending diameter in U-shaped and C-shaped probes, respectively. In addition, the sensitivity of D-shaped sensors increases as the distance between the core layer and flat surface decreases [10,15]. The sensitivity of these sensors can be further optimized by creating double pass evanescent field absorption from a suitable fiber end shape (hemispherical, triangular, or wedgeshaped) [11,16,17].…”