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Biological Sensing
Published in Marcelo Martins Werneck, Regina Célia da Silva Barros Allil, Plastic Optical Fiber Sensors, 2019
Regina Célia da Silva Barros Allil
In a multi-mode optical fiber, the light propagation takes place by the principle of total internal reflection (TIR); as a consequence, the incidence angle of the traveling optical ray is required to be higher than that of the critical angle. In the core-cladding interface, an EW is generated that extends with a range from 50 to 1000 nm into the cladding depending on the wavelength, the refractive index, and the angle of incidence [42].
Optical Fibers
Published in Johan Meyer, Justice Sompo, Suné von Solms, Fiber Lasers, 2022
Johan Meyer, Justice Sompo, Sune von Solms
The above condition provides a rough estimate of a fundamental limitation of step-index fibers. The effect of intra-modal dispersion in multi-mode optical fiber is significantly reduced by using graded-index fibers.
Review on the Developments and Potential Applications of the Fiber Optic Distributed Temperature Sensing System
Published in IETE Technical Review, 2021
Ramji Tangudu, Prasant Kumar Sahu
R. R. Lombera et al. [48] proposed, and demonstrated for the performance enhancement of Brillouin OTDA-based DTS system using graded-index multi-mode gold-coated optical fiber. With the proposed optical fiber, the DTS system can sense up to 600°C of temperature with ∼ 10°C of an average sensing resolution. In this work, the two ends of the gold-coated multi-mode fiber were spliced with standard silica graded-index multimode optical fiber, and mono-mode optical fiber for the short region to provide access from both ends of the Brillouin OTDA system. In the proposed Brillouin OTDA-based DTS system, the length of sensing (gold-coated multi-mode) fiber was 80 m. From 72 m position to 80 m position of the sensing fiber was affected by the temperature, which has ranging from 50°C to 600°C. The proposed DTS system offered consistent performance for sudden increasing or decreasing the temperature on the sensing fiber. To get these results, 8 mW of probe peak power, and 2 W of pump peak power were transmitted from the DFBLD device. The major drawbacks of the proposed sensing system were more complexity from the double-ended access scheme, and 20 dB/km of attenuation loss from gold-coated multi-mode optical fiber [48].
Deep learning based force recognition using the specklegrams from multimode fiber
Published in Instrumentation Science & Technology, 2023
Jie Lu, Han Gao, Yuanyuan Liu, Haifeng Hu
The schematic of experimental setup is shown in Figure 1. The output light of the laser source (λ 1550 nm) is coupled to the multimode fiber focusing lens, which is beneficial to excite higher order modes. The two ends of the multi-mode optical fiber are fixed with fiber clips. The distance between two clips is 24.8 cm, and the force is applied to the fiber in this range using a dynamometer. The output speckle of the multimode fiber is collimated by an objective and CCD camera (Flir Fg-p5g-50s4m-c) to record the specklegrams projected to the imaging plane. The force is applied on the fiber by the probe as shown in Figure 1b.