Yun Jiang Rao

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We propose and demonstrate a Fabry-Perot (F-P) optical fiber tip sensor for high-resolution refractive-index measurement fabricated by using 157-nm laser micromachining, for the first time to our knowledge. The sensor head consists of a short air F-P cavity near the tip of a single-mode fiber and the fiber tip. The external refractive index is determined(More)
A fiber-optic curvature sensor based on the single-mode-multimode-single-mode (SMS) fiber structure is developed. Several notches in the transmitted spectrum of the SMS fiber structure are generated due to the multimode interference effect. The dependence of the wavelength shifts and intensity changes of three transmission notches on the applied curvature(More)
Micro Fabry-Perot (F-P) interferometers (MFPIs) are machined in a single-mode fiber (SMF) and a photonic crystal fiber (PCF) by using a near-infrared femtosecond laser, respectively. The strain and temperature characteristics of the two MFPIs with an identical cavity length are investigated and the experimental results show that the strain sensitivity of(More)
An ultra-long phase-sensitive optical time domain reflectometry (Φ-OTDR) that can achieve high-sensitivity intrusion detection over 131.5km fiber with high spatial resolution of 8m is presented, which is the longest Φ-OTDR reported to date, to the best of our knowledge. It is found that the combination of distributed Raman amplification with heterodyne(More)
A phase-sensitive optical time-domain reflectometry (Φ-OTDR) with 175 km sensing range and 25 m spatial resolution is demonstrated, using the combination of co-pumping second-order Raman amplification based on random fiber lasing, counter-pumping first-order Raman amplification, and counter-pumping Brillouin amplification. With elaborate arrangements, each(More)
We demonstrate an all-fiber optical Fabry-Perot interferometer (FPI) strain sensor whose cavity is a microscopic air bubble. The bubble is formed by fusion splicing together two sections of single-mode fibers (SMFs) with cleaved flat tip and arc fusion induced hemispherical tip, respectively. The fabricated interferometers are with bubble diameters of(More)
We report a simple and robust all-fiber in-line Fabry-Pérot interferometer (FPI) with an air bubble cavity, which is fabricated by directly splicing a multimode photonic crystal fiber (MPCF) to a conventional single-mode fiber with a commercialized fusion splicer. The air microbubble inserted between the two fibers has two smooth glass-air(More)
A novel tunable fiber ring laser configuration with a combination of bidirectional Raman amplification and dual erbium-doped fiber (EDF) amplification is proposed for realizing high optical signal-to-noise ratio (SNR), long-distance, quasi-distributed fiber Bragg grating (FBG) sensing systems with large capacities and low cost. The hybrid Raman-EDF(More)
The combination of Raman amplification and optical pulse coding (OPC) is proposed to reduce the frequency uncertainty in a long-distance Brillouin optical time-domain analyzer (BOTDA) under higher spatial resolution. The experimental characterization of temperature sensing with measurement accuracy ~ 1°C under ~ 2.5-m spatial resolution over a whole(More)
In this paper, we report two fiber-optic temperature sensors based on silica/polymer microfiber knot resonators (SMKR/PMKR). The structures of these sensors are composed of three layers, MgF(2) crystal plate is adopted as the substrate, and the sensing knots are covered by a thin MgF(2) slab to keep it steady and immunity to the environment fluctuations.(More)