A new distributed fibre optic chemical sensor based on evanescent wave polarimetric interferometry is proposed with the underlying objective to apply the technology to gas chromatography. It allows real-time monitoring of the displacement of a chemical substance along a capillary. Theoretical analysis, modelling and fabrication of a special fibre containing an off-axis capillary is presented. Proof of the principle is experimentally demonstrated with liquid droplets.
Two fibre-optic probes are combined for the simultaneous monitoring of colour and refractive index of liquids, including highly coloured ones. It is shown how, through modelling, the design can be adapted to cover different ranges of refractive index, light absorption and sensitivity.
Background
Studying the anti-predatory behavior of mammals represents an important challenge, especially for fossorial small mammals that hide in burrows. In the Arctic, such behaviors are critical to the survival of lemmings considering that predation risks are high every summer. Because detailed information about how lemmings use burrows as hideouts is still lacking, we developed a 1.59 g photosensitive collar to record any event of a small mammal moving between a dark area (e.g., burrow) and a bright area (e.g., outside the burrow). Tests of how collars affected lemming behavior were conducted in captivity in Cambridge Bay, Nunavut, Canada, in November 2019 and field tests were conducted on Bylot Island, Nunavut, Canada, in August 2021.
Results
The device was made of two chemical batteries and a printed circuit board (PCB) equipped with a photosensor and a real-time clock that recorded amplitude transient thresholds of light (lux) continuously. In accordance with ethical use of such devices, we verified that no abnormal loss of body mass was observed in captive or free-ranging lemmings, and no difference in recapture rates were observed between those with and without a collar, though we could not test this for periods longer than 108 h. Measurements of light intensities revealed consistent patterns with high lux levels at mid-day and lowest during the night. Lemmings showed clearly defined behavioral patterns alternating between periods outside and inside burrows. Despite 24-h daylight in the middle of the summer, August nighttime (i.e., 11 PM to 4 AM) lux levels were insufficient for amplitude transient thresholds to be reached.
Conclusion
By taking advantage of the long periods of daylight in the Arctic, such technology is very promising as it sets new bases for passive recording of behavioral parameters and builds on the prospect of further miniaturization of batteries and PCBs.
Smart laser-based material processing systems require complete monitoring of the laser beam characteristics. The development of such monitoring units depends strongly on the beam sampling device employed. Beam samplers compatible with a randomly polarized 1 kW average power Nd:YAG laser has been realized by etching an holographic grating directly onto the surface of a high quality fused silica substrate [1].
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