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Maximizing telecomminaction backbone fiber utilization

In the late eighties one proposal for providing high speed data to remote rural areas was to install a Wave Divisional Multiplexer on the telecommunications backbone fiber optic cable. The shelf for the WDM’s was taken from an obsolete AT&T 405 M bps transport system. This shelf was housed in a stainless steel enclosure that AT&T built to their reliability standards. The customer premise equipment would have been a DMX-1000 low capacity multiplexer that was fitted with a 1550 nm laser from the obsolete 405 M bps transport system. The DMX-1000 had three interfaces at 45 Mbps and provided twenty eight DS-1’s per interface. The 1550 nm system would allow additional capacity to be added by adding wavelengths that are separated by 20 nm, when the technology became available.


The DMX-1000 was never utilized because AT&T fitted the fiber interface with their highest power 1550 nm laser which cost more than the project budget would allow. I was negotiating with AT&T to get an interface that was fitted with an intermediate range laser when Wiltel bought Lightnet, my employer. Wiltel was of the opinion that high speed data to remote areas would always be a niche market and that the size of the market would not justify its development. AT&T would have treated the fiber from the WDM to the customer premise as a backbone fiber and did not consider it compatible with their business plan since the reliability that could be guaranteed would be below that which was the standard for their backbone. Sprint, which owned half of the fiber optic cable involved, never commented on the project. The beta test for the WDM housing was completed by installing the enclosure in a handhold along the railroad track at the Paces Ferry Road crossing, Atlanta, GA. The backbone utilized 1550 nm and the fiber to Lighnet’s control center was 1300 nm, pending the appropriate equipment from AT&T.


The fiber from the WDM to the remote location would utilize 1550 nm laser technology because the range is longer than that of the 1300 nm lasers and the ability to add capacity by adding additional wavelengths. The use of the WDM on the backbone fiber between sites would provide access to pockets of significant population density without having to build a new facility on the network or cause repeater sites to need to be expanded beyond the existing easements. On the spans where the WDM was to be installed the original 1300nm repeater spacing would have continued to be used even after the conversion to 1550 nm so that the power lost at the WDM would not degrade reliability and would allow for repairs if there was a cable cut in the future. The use of erbium amplifiers would greatly extend the range of the fiber to a remote location. These WDM’s would be installed adjacent to an existing right of way so that the fiber could be installed with a minimal expense. Once the fiber is terminated at a customer location anyone could utilize the capacity. The local telephone company, a cable company, utility or start-up company could sell capacity if the appropriate regulations are in place. If erbium amplifiers are used on the backbone fiber and the original repeater spacing is feasible then more than one WDM could be installed between sites. This would create a new network in areas where the population density would make the endeavor economically feasible and dependence on wireless network is not inherently the best option.


I have not been involved in telecommunications for several years, but I believe such an endeavor would be feasible. There should be enough obsolete equipment available that would support the project at a reasonable cost.

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1 vote
Idea No. 242