2 October 2008 Audio communications with a mid-IR laser
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Abstract
We have demonstrated audio communications with a mid-IR laser. The laser is a frequency doubled Q-switched CO2 system producing approximately 12ns pulses at 4.6μm. The audio signal was encoded on the beam by means of pulse frequency modulation (PFM) with a carrier frequency of 37kHz. A 1mm diameter, low noise thermoelectrically cooled IR photovoltaic detector with electrical bandwidth 250MHz was used to detect the laser beam. A custom-built circuit stretched the resultant electrical pulses to approximately 1.5μs, before being demodulated. High quality audio signals were received and recorded, and still images were successfully transmitted using slow scan television techniques. The demonstration was conducted at the Defence Science & Technology Organisation's laser range at Edinburgh, South Australia in July 2008. The distance was 1.5km, with a slant path (8m to 1.5m). The maximum range using this system is estimated to be tens of kilometres.
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Kenneth J. Grant, Bradley A. Clare, Wayne Martinsen, Miro Dubovinsky, William Isterling, Daniel Wright, Kerry A. Mudge, "Audio communications with a mid-IR laser", Proc. SPIE 7115, Technologies for Optical Countermeasures V, 71150I (2 October 2008); doi: 10.1117/12.803579; https://doi.org/10.1117/12.803579
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