A sapphire fiber high temperature sensor based on Fabry-Perot interference was studied in the paper. A sapphire wafer served as the Fabry-Perot cavity was fixed to the end face of the sapphire fiber. The sensor was encapsulated in an alumina ceramic tube-ceramic sleeve structure to improve structural stability. Experiment results showed the sensor had a wide temperature measurement range of 25 °C-1550 °C. The temperature sensitivity reached 32.5 pm/°C at 1550 °C. Furthermore, the temperature was demodulated from the interference spectrum through fast Fourier transform algorithm. It was concluded that the sapphire fiber sensor with advantages of small size, good stability and a wide range of temperature measurement is very promising for measuring high temperature.

Nonlinear filtering algorithms have significant implications in the optimal estimation of navigation states and in improving the accuracy, reliability, and robustness of navigation systems. This manuscript surveys the developments of the nonlinear filtering algorithms (extended Kalman filtering (EKF), unscented Kalman filtering (UKF), Cubature Kalman filtering (CKF), particle filtering (PF), neural network filtering (NNF)) and adaptive/robust KF in integrated navigation systems. The principle, application, and existing problems of these nonlinear filtering algorithms are mainly studied, and the comparative analysis and prospect are carried out.

An optical fiber immunosensor with a low detection limit based on plasmon coupling enhancement is proposed for detecting human immunoglobulin G (IgG). Graphene oxide (GO)-gold nanorod composites are synthesized and modified onto a photonic crystal fiber (PCF) surface coated with a Au film. GO, as a biosensitive layer, is used to decorate the gold nanorods and concentrate target molecules. The experimental result indicates that the refractive index sensitivity is drastically enhanced to 22248 nm/RIU because of plasmon coupling. Correspondingly, the human IgG detection limit decreases to 6 ng/mL. Moreover, the PCF is insensitive to temperature fluctuation, which can further reduce the measurement error.

A new method is proposed for reducing the error of thermocouples in measuring the surface temperature of blades with cooling film. Both the measurement error and the conduction error of film cooling blade surface temperature were numerically investigated. Benefited from the optimized thermocouple fixation mode, the temperature measurement error can be reduced by 40% at least. The temperature measurement errors of surface fixed model and groove fixed model were analyzed and compared. Furthermore, the effects of different head gaps, film thickness and film temperature on the temperature measurement error are described in detail. Under the optimal parameters, the temperature measurement error of thermocouples can be decreased by 99.5%. Finally, the groove fixed model is studied experimentally and the results show that the temperature measurement error can be reduced by 99.83% under the optimal groove depth, which is in good agreement with the simulation results. This error analysis and reduction method attaches great significance to the improvement in the temperature measurement accuracy of turbine blades, as well as the research of new temperature measurement methods.

A colorimetric high-temperature sensor based on a sapphire fiber bundle is reported in this work. The radiation voltage ratio of two neighboring wavelengths is used to detect the temperature. The sapphire fiber bundle can increase the efficiency of radiation light collection. To improve mechanical properties and structural stability, the sensor probe is encased in a ceramic tube. Experimental results show that the sensor can be used in a wide temperature range of 648–1800 K with a measuring accuracy range from 0.4% to 1.8%. The sapphire fiber colorimetric high-temperature sensor effectively reduces the effects of various types of interferences in the measurement process because of the calibration procedure. In the field of high-temperature sensing, the proposed colorimetric sapphire fiber high-temperature sensor offers various application potentials.

In this paper, a sapphire fiber colorimetric thermometry system is used to achieve high-precision measurement of ultrahigh-temperature up to 2000K by correcting the reflected radiation error. Based on the principle of colorimetric temperature measurement, a radiometric thermometry system is constructed using sapphire fiber with a high melting point. Reflection errors on ceramic blades in high-temperature furnaces are eliminated by calibrating the reflected radiation. The experimental results show that the temperature measurement error of the sapphire fiber colorimetric thermometry system is less than 1% in the range of 1400-2000K. And the repeatability error of the experiment is ±0.9%, which achieves the high-precision measurement of ultrahigh-temperature by correcting the reflection error.