Peter wrote:

I hate to be a doom sayer, but any chump with a couple of tools and rudimentary knowledge can lift manholes, cut cables and jump to another location in minutes. No amount of diversity could defend against a concerted attack like that unless you start installing very special low-level routes away from street level into many many buildings.

While it is impossible to stop someone (a terrorist) from cutting fiber, it is possible to limit his ability to do damage. It is possible to create alternative routes to be used in such cases. Then while the primary route may be down, the alternate route will be used and no terrorist should be able to locate the alternative route since this is something known only to the telecom carrier and is definitely not public knowledge. While this is not new to anyone, what is new is that cutting the cost of this alternate route for every fiber is the key to making no single points of failures. This means that carriers must be able NOT to double equipment just because another link is used. There is such a solution and it is the use of optical protection. optical networks can be protected in the optical domain without the cost of additional equipment - adding only the cost of the optical protection equipment which is an order of magnitude lower than that of the high data rate equipment. This allows the carriers to double up on equipment only once (to deal with equipment failure using today's redundancy schemes) and use the SAME double equipment to protect from fiber cuts as well by providing disaster recovery architectures in the optical domain. Gil