A Fiber Bragg Grating (FBG) based force sensor with high-sensitivity and temperature compensation capability. It can be used to accurately measure the contact force (CF) between medical equipment and tissues or organs in minimally invasive surgery (MIS). To achieve temperature compensation, a novel design incorporating dual elastomer-based dual FBGs is employed, and its effectiveness is verified through finite element simulation. After temperature compensation, the developed sensor has a sensitivity of 54 pm/N, a resolution of 0.019 N, and a root-mean-square error (RMSE) of 0.064 N. The utilization of temperature disturbances for measuring distal contact force demonstrates a substantial enhancement compared to direct measurement methods. Additionally, in vitro experiments are conducted using a silicone vascular model, demonstrating the sensor’s capability to detect certain alterations in vascular pathways. Finally, a simulated palpation liver experiment confirmed that the designed force sensor can preliminary detect of the relative hardness of the tissue based on the magnitude of the CF. In vitro experiments have proved that the designed FBG force sensor has a practical value in MIS.
To mitigate the failure of a Hilbert transform-based fixed-threshold multi-peak demodulation algorithm in distributed Fiber Bragg Grating (FBG) sensing systems with light noise, an adaptive multi-peak demodulation algorithm based on the Hilbert transform is proposed in this paper. The algorithm adopts the thought of Divide and Conquer, including reflection spectrum segmentation and single peak detection. Multiple sub-spectra of the FBG multi-peak spectrum is segmented by the Hilbert transform and calculating adaptive threshold method, and then the Gaussian fitting algorithm is used to achieve the precise positioning of the spectral peaks. Theoretical analyses and simulation results show that the algorithm using an adaptive threshold as a threshold of splitter can greatly improve the portability of the algorithm in complex situations, and improve the algorithm’s noise resistance, demodulation speed, and accuracy. It shows that the algorithm provides a new way of demodulation for distributed FBG sensing systems.
Four-wave mixing created by pump-probe structure with small frequency spacing and enough high power is demonstrated and discussed by introducing single optical beam into semiconductor laser with external cavity, in which the injected beam is called as probe wave whose frequency detuning is controlled within ±50 GHz, and lasing resonance mode is selected as pump wave. Based on the nonlinear interactions of pump wave, probe wave and conjugate signals, microwave signals with different frequencies are simultaneously achieved. The frequency of microwave signal is tunable by adjusting the spacing between pump and probe wave.
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