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 3.44 n m / g / c m 3 . 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.

Aiming at the problems of weak dynamic response and difficulty in diagnosis of early damage of rolling bearings, a diagnosis method for early damage of rolling bearings is proposed. Taking radial rolling bearings as the main research object, the load symmetric structure of deep groove ball bearings is analyzed. Based on the mechanical second-order system theory, the sensor monitoring structure is constructed. The generalized resonance principle is used to identify weak signals, and the fiber Bragg grating is used for signal sensing. The signal is obtained through the fiber Bragg grating high-speed demodulator. When a continuous periodic generalized resonance wave appears in the amplitude–frequency analysis of the signal, and there is a high-frequency resonance frequency, it can be proved that the bearing is faulty. The diagnosis method can effectively avoid the interference of low-frequency signals, the frequency spectrum is pure and there is no electromagnetic interference. It fully shows that the fiber Bragg grating sensor is suitable for the monitoring and diagnosis of the early weak fault of the bearing.

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

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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.