Path: utzoo!utgpu!watmath!clyde!att!osu-cis!killer!vector!nobody From: jbn@glacier.stanford.edu (John B. Nagle) Newsgroups: comp.dcom.telecom Subject: Re: Laser Beam as a ethernet backbone Message-ID: Date: 11 Dec 88 23:08:24 GMT Sender: chip@vector.UUCP Lines: 29 Approved: telecom-request@vector.uucp X-Submissions-To: telecom@bu-cs.bu.edu X-Administrivia-To: telecom-request@vector.uucp X-TELECOM-Digest: volume 8, issue 199, message 3 This comes up every once in a while, and the definitive information is as follows. The FCC has jurisdiction over "Radio", according to the Communications Act of 1934, as amended. "Radio Waves or Hertzian Waves" are defined in 47 CFR Ch. 1 part 2 subpart A section 2.1 as "Electronic waves of frequencies arbitrarily lower than 3,000 GHz, propagated in space without artificial guide." So FCC regulation stops at 3,000 GHz. The 3,000 GHz limit is by international agreement (Radio Regulations, Geneva, 1982). This limit is in the very long infrared range. In article donp@apollo.COM (Don Preuss) writes: >X-Administrivia-To: telecom-request@vector.uucp >X-TELECOM-Digest: volume 8, issue 196, message 6 > >The National Institutes of Health has one of these set up >between two buildings. It took the company a few >trys to get it right, and the latest I heard was that they >are still getting a large number of retransmits. Rain and snow are serious problems. One thing that helps is to use large collecting optics at both ends, so that the beam occupies a physically larger diameter but remains collimated. Usually a large parabolic reflector is used. This will improve operation in light rain and snow. In heavy precipitation, though, optical systems just don't work. To get through heavy rain, you must use a wavelength bigger than raindrops. John Nagle