Dan Armstrong <dan@beanfield.com> writes:

  

Forgive me, but

Isn't Sonet usually deployed in a ring?  Why the heck would a fiber
this important not be?
    

sonet, obviously, does not *have* to be in a ring, but it often is.
unfortunately, a fair percentage of the time, the additional
protection offered by a ring topology is a mirage, due to a
configuration known as "collapsed backbone".  in this instance, both
pairs of fiber ride in the same conduit for some portion of the
distance (most notably laterals to building entrances, but sometimes
for a fair distance down the street).  the driving factor in building
this way is usually cost savings.

while this arrangement does protect against failures of optics and
electronics (which in fairness are indeed more common than fiber
cuts), it provides no protection against hungry construction (or in
this case, lawn maintenance) equipment.

                                        ---rob