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Technology Stocks : LAST MILE TECHNOLOGIES - Let's Discuss Them Here -- Ignore unavailable to you. Want to Upgrade?

To: MikeM54321 who wrote (6634)	3/12/2000 4:40:00 PM
From: Frank A. Coluccio	Read Replies (2) \| Respond to of 12823

re: Infrared Lasers used in free space systems and EYE SAFETY Hello Mike, It really isn't a joking matter. Somewhere else on these boards, I don't recall where exactly, someone made a blanket statement about the safety of 1.4 to 1.5 um wavelengths. I'm sure that this was innocent enough, but the fact is that safety can only be assessed after power levels and beam concentrations have been fully understood, along with other parameters such as which wavelengths are used, filters on viewfinders and other aids, etc. ------ Under normal conditions, it may or may not be safe to look into a low-powered system's transmitter without any residual side effects. But don't do it. As a matter of habit it's best not to do this, anyway. But even low-power systems can impart damage to the cornea or retina, or both, dependent on which wavelength is used and its intensity, and if passed first through an optical aid such as a telescope or a pair of binoculars that has a high-enough optical gain factor associated with it, and not been outfitted with the proper filters. ------ You ask me for personal experiences, eh? Have you been speaking with Dave Horne? smiles Fact is, I did have one such experience on top of a roof one day in California at a flat-top industrial complex outside of San Jose where they were using IR shots between buildings for Ethernet traffic. As an aside, I agreed to go on this troubleshooting exercise to this high visibility client of theirs during a visit to the Coast, to determine why intermittent outages were occurring. It turned out to be a tree that had grown very close to the narrow IR path between two buildings, and which in fact only acted up by getting in the eway of things slightly (but enough to cause high error counts which caused an excessive number of re-transmissions) on windy days. It was this owner of the then-popular IR firm (ISHER Corp.) who pointed out the tree culprit to me. A few moments later I took the binoculars out of the bag, and began to put it up to my eyes, when attempted to smack them out of my hands. I thought that he was losing it for a moment, until he quickly apologized and explained why he did it. He explained to me something I should have already been aware of but didn't think of at the moment, and that was the dangers associated with looking directly into the distant "spot" through any form of optical magnification aid, such as the binoculars which I was using at the time. He then provided me with the proper filters which allowed me to see the spot (and only the spot), in a way that was both a bit eery and at the same time extremely definitive for alignment purposes. These same filters are used in the actual transceiver viewfinders along with cross-hairs for alignment purposes by technicians, in case you were wondering. This entire issue of safety using higher powered devices has been an issue that I have been processing in the back of my mind now for about a week, ever since the buzz over the new gizmo became a matter of public 'focus.' I hesitate to cry out that there is a fire in the theater, or a wolf wearing jammies, just yet, as I am awaiting some answers on this subject from a reputable source, and will post them when I receive them. Until then, I personally would NOT use a high powered telescope or pair of binoculars anywhere in the vicinity where there is widespread experimentation or actual use of these newer devices right now, as in, for example, while doing site seeing. Especially since the LASERS being used in these newer systems are said to be rated in terms of actual watts, as opposed to lower-powered devices which I had been accustomed to using in the past). OTOH, they may have groomed, spread, or otherwise fashioned their beams to be relatively innocuous, I simply don't know enough about their approach at this time. Perhaps once I've finished reading their patents later on this afternoon I'll know more about how they plan to address this matter. But the general list of considerations which I've presented here remain relevant in most similar situations, nonetheless. Stay tuned, but not necessarily focused. grin FAC