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Unformatted text preview: Line-of-Sight Optical Communications It is desired to build a line-of-sight laser optical communications system con-
necting the Van Leer Electrical Engineering building and the Bell South building.
The distance between the buildings is 1045 m. For safety reasons, a Visible wavelength
is needed. Therefore, it is decided to use a semiconductor diode laser of wavelength
620.0 nm. Also, for safety reasons, the diameter of the laser beam at the Bell South
receiver needs to be no more than 150 mm. A beam—expander collimator is to be used with the diode laser at Georgia Tech. Calculate, showing all work, the output diameter of the beam from the collimator
at Georgia Tech in order to produce a beam of 150 mm diameter at Bell South. Express
your answer in millimeters accurately to four signiﬁcant ﬁgures. Put your ﬁnal answer in the space provided. Output laser beam diameter : mm. Line-of-Sight Optical Communications Far—ﬁeld angle measured to Bell South building 0 z W = 0.0001435md = 0.008224deg
1045m Far—ﬁeld angle due to diffraction by an aperture (collimator) of diameter D 9:3
g = 5.4995 mm 4
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This note was uploaded on 04/29/2008 for the course ECE 4500 taught by Professor Gaylord during the Spring '08 term at Georgia Institute of Technology.
- Spring '08