Reflective Optical Fiber Sensors Based on Tilted Fiber Bragg Gratings Fabricated With Femtosecond Laser

Abstract

The fabrication of tilted fiber Bragg gratings (TFBGs) in non-photosensitized single-mode fiber by infrared femtosecond (fs) laser is reported for the first time to the best of our knowledge. The tilted grating structure is obtained by focusing laser pulses through a phase mask into a tilted positioned fiber sample, which is moving along with the interference fringe to form a grating region covering the entire fiber core and partial cladding. A reflective fiber probe based on the TFBG with a gold mirror sputtered on one end has been fabricated and its maximum refractive index (RI) sensitivity is 12.276 nm/RI unit in the RI range of 1.4091-1.4230 for the cladding mode LP020. A wavelength-power demodulated technique based on the sensors has been proposed to measure axial strain and temperature simultaneously, which is found suited to work in harsh environment, especially at high temperature up to 800 C.

Highly sensitive refractive index measurement based an a thinned fiber taper

“…Recently, optical fiber sensors have been extensively studied in chemical and biomedical applications due to their merits of corrosion resistance, small size, fast response, and immunity to electromagnetic interference [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Many kinds of fiber sensors for surrounding refractive index (SRI) measurement have been developed, such as fiber Bragg gratings (FBGs) [1][2][3], long period fiber gratings (LPFGs) [5][6][7], microstructured optical fibers (MOFs) [8], and varieties of optical fiber interferometers [11][12][13][14]. The fiber RI sensors based on thinned and tilted FBGs have high resolution, but they require precise and expensive fabrication technologies, including phase mask and laser source.…”

“…Microwave dual-band bandpass filters (BPFs) are important and essential components for the multiband wireless communication systems. Dual-band BPFs can be realized by cascading a wideband BPF with a narrowband bandstop filter [1], or combining two BPF using a match network with common input and output [2], which leads to a relatively large area. A transmission line is interrupted with multiple shunt stubs of equal and unequal lengths to construct dual-passbands, however they cause the large circuit size [3,4].…”

Liquid Seal for Temperature Sensing with Fiber-Optic Refractometers

“…Note that the lowest sensitivity of −0.52 nm/°C at 38 °C is also much higher than that of the bare TCFMI. The temperature sensitivity of our sensor is tens or hundreds of times higher than those of fiber grating-based sensors [4–6,10–12] and most interferometric fiber-optic sensors [7–9,13,14,22], and even higher than those of some liquid-sealed PCF-based sensors [15]. In our experiments, the resolution of used OSA is 0.020 nm, then the theoretical temperature resolutions of ~0.008 °C and ~0.038 °C can be achieved at near 10 °C and 38 °C, respectively, for the proposed liquid-sealed TCFMI.…”

A highly sensitive fiber Bragg grating diaphragm pressure transducer

“…It is well understood that electronic sensors have limited capabilities in certain conditions such as harsh environments where there is risk of sparks causing an explosion, in extreme temperatures and pressures [1], or high electromagnetic interference (EMI), such as overhead transmission lines [2]. These are the areas where optical fiber sensors offer an attractive alternative due to their small size and weight, immunity to EMI, and needing no power supply [3].…”