pH sensor based on tilted fiber Bragg grating surface plasmon resonance with a polyaniline reaction deposition film layer.

In this paper, we propose a surface plasmon resonance (SPR) fiber-optic pH sensor combined with a tilted fiber Bragg grating (TFBG) by continuously coating gold and polyaniline (PANI) onto the surface of a TFBG. The micron-scale thickness polyaniline film provides the sensor with good sensitivity, and it achieves accurate measurement of pH values ranging from 2 to 12 by utilizing the pH-responsive mechanism of PANI and the surface plasmon resonance characteristics. Experimental results show that within the 2-12 pH range, the sensitivity of the TFBG surface plasmon resonance pH sensor based on PANI coating is 0.50335 nm/pH, and results demonstrate, a linear correlation coefficient between wavelength and pH value reaching 0.96614. This indicates significant potential for future engineering applications in real-world pH measurement using this sensor.

Realization of an ultra-high pressure dynamic calibrate system by drop hammer based on fiber Bragg grating strain sensor.

In this letter, we propose a novel technique for dynamic ultra-high pressure calibration that measured pressure by FBG based strain sensor. Generally, the traditional method of dynamic ultra-high pressure calibration by standard sensor is costly and it is difficult to improve the accuracy. Therefore, we prefer FBG strain sensor to replace the standard sensor to calibrate the ultra-high pressure. In this proposal, the calibration process is that the central wavelength of the FBG attached to the elastic element changes rapidly with the strain of the elastic element during the drop hammer impact, synchronously. This allows the calibration accuracy to be easily increased to 0.02% and the cost to be reduced by 1/100 compared to traditional calibration techniques. The experiment results show that coefficient of linear correlation between the strain waveform and the pressure signal reaches 0.999. The strain calibration based on FBG is of great significance to the measurement and calibration of dynamic ultra-high pressure sensors.

Fiber-optic airflow velocity sensing method based on a 45° tilt fiber grating combined with a single-walled carbon nanotube coated fiber.

We propose and experimentally demonstrate an airflow velocity sensing method based on a 45° tilt fiber grating (TFG) that is combined with a single-walled carbon nanotube (SWCNT) coated fiber Bragg grating (FBG). The principle behind which is to produce a dynamic thermal equilibrium between the light heating and the airflow cooling. For the first time, to the best of our knowledge, a 45°-TFG is used as the heating element for the hot-wire anemometer. By diagnosing the Bragg wavelength of the SWCNT coated FBG, the temperature variations of the sensing fiber are measured with respect to the airflow velocities, which vary from 0 to 1 m/s. Moreover, under low light power consumption of 20 mW, the proposed sensor is shown to have good performance. Experimental results reveal that the sensitivity of the sensor increases with the heating pump. Due to the advantages of its simplicity and reliability, alongside its high photo-thermal conversion efficiency, this technique has excellent potential for future use in remote monitoring with airflow velocity sensing.

Simultaneous measurement of liquid-level and density by detecting buoyancy and hydraulic pressure: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 6843 (2020)OPLEDP0146-959210.1364/OL.412738.

Simultaneous measurement of liquid-level and density by detecting buoyancy and hydraulic pressure.

In this Letter, we propose and experimentally demonstrate a method for simultaneous and complete discriminative measurement of liquid-level and density for the first time, to the best of our knowledge. The principle is to measure the responses of optical fiber sensing units caused by buoyancy and hydraulic pressure. By utilizing a designed steel diamond structure, the sensor sensitivity is significantly improved. The theoretical models and experimental methods are analyzed in detail. For large-range liquid-level measurement, a high sensitivity of 77.3 pm/cm with resolution of 0.129 mm (accuracy of 0.149‰) is achieved. As a trade-off between density measurement and sensor capability, a dual-parameter sensing is demonstrated experimentally, which features liquid-level sensitivity of 34.7 pm/cm and density sensitivity varying from 1 to 3.44nm/g/cm3. Taking advantage of the compact size, easy fabrication, and low cost, this method has great potential in real-time intelligent monitoring of reserves and quality for industrial storage of fuels and chemicals.

Optical Sensor of Thermal Gas Flow Based on Fiber Bragg Grating.

This paper aims at solving the problem of explosion proof in measurement of thermal gas flow using electronic sensor by presenting a new type of flow sensor by optical fiber heating. A measuring unit based on fiber Bragg grating (FBG) for fluid temperature and a unit for heat dissipation are designed to replace the traditional electronic sensors. The light in C band from the amplified spontaneous emission (ASE) light source is split, with one part used to heat the absorbing coating and the other part used in the signal processing unit. In the heating unit, an absorbing coating is introduced to replace the traditional resistance heating module to minimize the risk of explosion. The measurement results demonstrate a fine consistency between the flow and temperature difference in simulation. The method to enhance the measurement resolution of flow is also discussed.

Design of Novel FBG-Based Sensor of Differential Pressure with Magnetic Transfer.

In this paper, a differential pressure sensor with magnetic transfer is proposed, in which the non-electric measurement based on the fiber Bragg grating (FBG) with the position limiting mechanism is implemented without the direct contact of the sensing unit with the measuring fluid. The test shows that the designed sensor is effective for measuring differential pressure in the range of 0~10 kPa with a sensitivity of 0.0112 nm/kPa, which can be used in environments with high temperature, strong corrosion and high overload measurements.