Free-space optical (FSO) links for high-speed communications between buildings must consider detrimental environmental effects including interference from sunlight in the receiver's instantaneous field of view (IFOV). Sunlight can degrade receive sensitivity resulting in link disruptions, even with significant optical filtering. Thus it is important to characterize this environmental effect for designing and testing optical transceivers. Background light levels are highly dependent on the geometry and environmental conditions of a specific link making general statements difficult. However, we have characterized the likelihood and frequency of direct or reflected sunlight passing into or near a terminal's IFOV. We have also measured detector solar power levels under sunny and partly cloudy conditions, and measured detector sensitivity degradation as a function of background light levels. This paper presents a summary of our results.
Free-space optical links for high-speed network communications between buildings must consider the detrimental environmental effects of terminal base disturbances. Terminal base motion results in tracking and pointing losses, which cause link outages if the base motion is sufficiently large (beyond terminal field of regard) or fast (too fast for the tracking system to reject). Thus it is important to characterize this environmental effect for design and test of optical terminals. Base motion is highly dependent on the installation environment of a specific link making general statements difficult. We have characterized terminal base disturbance levels through a combination of vibration measurements in numerous buildings, data gathered from operating links, and review of building stiffness and wind statistics in various cities. This paper presents a summary of our results.
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