Optical free-space communications at middle-infrared wavelengths

Mapping Intimacies ◽

10.1117/12.516517 ◽

2004 ◽

Cited By ~ 4

Author(s):

Rainer Martini ◽

Chris Glazowski ◽

Edward A. Whittaker ◽

Warren W. Harper ◽

Yin-Fong Su ◽

...

Keyword(s):

Free Space ◽

Space Communications ◽

Infrared Wavelengths ◽

Middle Infrared

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Perspectives on advances in high-capacity, free-space communications using multiplexing of orbital-angular-momentum beams

APL Photonics ◽

10.1063/5.0031230 ◽

2021 ◽

Vol 6 (3) ◽

pp. 030901

Author(s):

Alan E. Willner ◽

Zhe Zhao ◽

Cong Liu ◽

Runzhou Zhang ◽

Haoqian Song ◽

...

Keyword(s):

Angular Momentum ◽

Orbital Angular Momentum ◽

Free Space ◽

High Capacity ◽

Space Communications

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Reflectance characteristics of cumulative defoliation of balsam fir

Canadian Journal of Forest Research ◽

10.1139/x88-154 ◽

1988 ◽

Vol 18 (8) ◽

pp. 1008-1016 ◽

Cited By ~ 18

Author(s):

D. G. Leckie ◽

P. M. Teillet ◽

G. Fedosejevs ◽

D. P. Ostaff

Keyword(s):

Near Infrared ◽

Spectral Characteristics ◽

Broad Band ◽

Integrating Sphere ◽

Simple Relationship ◽

Spectral Bands ◽

Infrared Wavelengths ◽

Remote Sensing Techniques ◽

Middle Infrared ◽

Airborne Sensors

Knowledge of the spectral characteristics of trees with varying degrees of needle loss is essential for developing remote sensing techniques for assessing defoliation. Spectra covering the range 400–2400 nm were acquired for single tree crowns suffering varying degrees of cumulative defoliation due to the spruce budworm (Choristoneurafumiferana (Clem.)), using a spectrometer mounted in the bucket of a boom truck. Spectra over the range 360–1100 nm were also obtained for the components of defoliated trees (i.e., needles, bare branches, and lichen), using a separate spectrometer and integrating sphere. Estimates of defoliation symptoms of each tree were made from the ground and above the tree. Changes in reflectance had a close and simple relationship with the defoliation symptoms measured. The spectral differences due to cumulative defoliation that were observed were broad-band features. The best spectral regions for differentiating levels of cumulative defoliation symptoms were the blue, red, shorter near-infrared wavelengths, and middle-infrared. Although currently available satellite and airborne sensors operate in these spectral regions, defoliation assessment may be improved by the use of optimized spectral bands.

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