Fast-Response Fiber-Optic FPI Temperature Sensing System Based on Modulated Grating Y-Branch Tunable Laser

In this paper,a cost-effective and miniaturized instrument is proposed,which is based on a tunable modulated grating Y-branch(MG-Y)laser for rapid temperature measurement using a Fabry-Perot interferometer(FPI)sensor.The FPI sensor with a 1463-μm cavity length is a short segment of a capillary tube sandwiched by two sections of single-mode fibers(SMFs).This system has a broad tunable range(1527 nm-1567 nm)with a wavelength interval of 8 pm and a tuning rate of 100 Hz.Temperature sensing experiments are carried out to investigate the performance of the system by demodulating the absolute cavity length of the FPI sensor using a cross-correlation algorithm.Experimental results show that the sensor can reach the response time as short as 94 ms with the sensitivity of 802 pm/C.Benefiting from the homemade and integrated essential electrical circuits,the entire system has the small size,low cost,and practical application potential to be used in the harsh environment for rapid temperature measurement.

All-Fiber Liquid-Level Sensor Based on In-Line MSM Fiber Structure

We propose and demonstrate an all-fiber liquid-level sensor using an in-line multimode-single-mode-multimode (MSM) fiber structure. A piece of single-mode fiber (SMF) is spliced to two sections of equivalent multimode fiber (MMF) which are used as both mode splitter and mode coupler. The cladding mode will be excited when the light propagates from MMF to SMF, and then it will be combined with fundamental mode to form a Mach-Zehnder interferometer (MZI) when the light propagates from SMF to the other MMF. The liquid level is detected by the selected resonant dips shift of the transmission spectrum. A sensing sensitivity of 264.6 pm/mm is achieved for the proposed sensor with an SMF length of 26mm. Due to its compact structure, easy fabrication, and high sensitivity, the proposed liquid-level sensor is attractive for practical applications in a variety of fields, such as marine detection and chemical processing.

4-Mercaptopyridine Modified Fiber Optic Plasmonic Sensor for Sub-nM Mercury(II)Detection

In this paper,we propose and demonstrate a high-performance mercury ion sensor with sub-nM detection limit,high selectivity,and strong practicability based on the small molecule of the 4-mercaptopyridine(4-MPY)modified tilted fiber Bragg grating surface plasmon resonance(TFBG-SPR)sensing platform.The TFBG-SPR sensor has a rich mode field distribution and a narrow bandw idth,which can detect the microscopic physical and chemical reactions on the sensor surface with high sensitivity without being disturbed by the external temperature.For the environmental compatibility and highly efficient capture of the toxic mercury ion,4-MPY is modified on the sensor surface forming a stable(4-MPY)-Hg-(4-MPY)structure due to the specific combination between the nitrogen of the pyridine moiety and the Hg+via multidentate N-bonding.Moreover,gold nanoparticles(AuNPs)are connected to the sensor surface through the(4-MPY)-Hg-(4-MPY)structure,which could play an important role for signal amplification.Under the optimized conditions,the limit of detection of the sensor for mercury ions detection in the solution is as low as 1.643×10^(-10)M(0.1643 nM),and the detection range is 1×10^(-9)M-1×10^(-5)M.At the same time,the mercury ion spiked detection with tap water shows that the sensor has the good selectivity and reliability in actual water samples.We develop a valuable sensing technology for on-time environmental Hg t detection and in-vivo point of care testing in clinic applications.