glen@aecom.YU.EDU (Glen M. Marianko) (02/04/88)
We are planning a 3000ft. run of fiber optic cable across campus at present to run ethernet, but also to support the emerging FDDI standard should we choose to move to FDDI at a later date. Based upon the info given to me to date I have the following specs: Fiber Cable: 62.5/125 Multimode Graded Index Capacity: 200-500 MHz per kilometer dB Loss: 1.8dB per kilometer maximum Connectors: SMA 905/ST/Amphenol Duplex My greatest concern is this 200-500 MHz rating. What does it mean, exactly? Is 200 sufficient, or is 500 mandatory? One vendor said that 100 would likely be ok, but since we already approach 1km total length, 200 would be best. About connectors, as I understand it, there is no standard so there is a free-for-all. What's best considering we'll start with ethernet over fiber and later migrate to FDDI? Anyone suceessfully using FDDI yet? How about the Fibronix product? Is it worth while starting with FDDI right away or just waiting. HELP! Thanks... -- Glen Marianko - glen@aecom.yu.edu Supervisor of Data Communications Albert Einstein College of Medicine
eshop@saturn.ucsc.edu (Jim Warner) (02/05/88)
In article <1591@aecom.YU.EDU> glen@aecom.YU.EDU (Glen M. Marianko) writes: > > Fiber Cable: 62.5/125 Multimode Graded Index > Capacity: 200-500 MHz per kilometer > dB Loss: 1.8dB per kilometer maximum > Connectors: SMA 905/ST/Amphenol Duplex > >My greatest concern is this 200-500 MHz rating. What does it mean, >exactly? .... It isn't "MHz per kilometer". That would imply that the longer cable runs have greater bandwidth. It's "MHz-kilometer". You divide this number by the length of your cable to find the bandwidth of the fiber segment. You can write the spec as 200 MHz-Km or greater. The actual signalling rate on a 100 MHz FDDI ring is 125 MHz. But a 3000 ft run is less than 1 KM so a 200 MHz-KM cable will have adequate bandwidth. "dB per kilometer" is correct. The "dB" is a measure of signal amplitude loss, and the longer the cable, the greater the loss.