Abstract
Free-space IR transmission provides high bandwidth and
good security with small-sized and low-cost links, for
instance, for high-bit-rate wireless LANs. Some
robustness against shadowing is achieved using diffuse
channels, but disadvantages are high path loss and
multipath propagation. We use ray-trace simulation
software to analyze IR channels in realistic office
rooms. Simulations are performed to test the methods and
to specify the bandwidth and power budget requirements of
diffuse links. Both diffuse and specular reflections as
well as shadowing effects due to furniture are
considered. Based on the study, novel Monte Carlo
ray-tracing software, such as ASAP (Advanced System
Analyses Program), are suitable for analyzing the
multipath dispersion and the optical power budget of
infrared links in realistic indoor environments. The
simulations also reveal the benefits of quasidiffuse link
configurations, which are composed of multibeam
transmitters with restricted beam divergences as well as
of detectors with narrow fields of view. For
implementation of multibeam transmitters we design an
array-type diffractive element that modifies the beams of
a 2-D vertical-cavity surface- emitting laser (VCSEL)
array. A single element providing the largest 50-deg
illumination angle is fabricated for demonstration. The
measured diffraction efficiency is in fair agreement with
the calculated one after considering the properties of
the real VCSEL beam.
Original language | English |
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Pages (from-to) | 899-910 |
Journal | Optical Engineering |
Volume | 41 |
Issue number | 4 |
DOIs | |
Publication status | Published - 2002 |
MoE publication type | A1 Journal article-refereed |
Keywords
- optical links
- wireless LAN
- WLAN
- Monte Carlo
- Monte Carlo method
- ray tracing
- surface emitting lasers
- semiconductor laser arrays
- multipath channels