Fiber optic light sensor
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We describe a low-cost fiber optic sensor for measuring photosynthetically active radiation (PAR) in turbulent flow. Existing technology was combined in a novel way for probe development addressing the need for a small but durable instrument for use in flowing water. Optical components including fiber optics and a wide-spectrum light detector were used to separate light collection from electronic detection so that measurements could be completed in either the field or laboratory, in air or underwater. Connection of the detector to Arduino open-source electronics and a portable personal computer (PC) enabled signal processing and allowed data to be stored in a spreadsheet for ease of analysis. Calibration to a commercial cosine-corrected instrument showed suitable agreement with the added benefit that the small sensor face allowed measurements in tight spaces such as close to the streambed or within leafy or filamentous plant growth. Subsequently, we applied the probe in a separate study where over 35 experiments were successfully completed to characterize downward light attenuation in filamentous algae in turbulent flow.
KeywordsFiber optic sensor Photosynthetically active radiation PAR Light Meter Optics
The authors wish to thank the Montana-Wyoming USGS Science Center for loan of their Li-COR 192 m used in support of this work. The authors also wish to thank Kevin Chudyk for layout, assembly, and testing of the photodiode detector breakout board circuitry. Portions of this work were presented at SPIE Photonics Europe Innovation Village April 13–18, 2014.
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