Passive Optical Networks

6.2.1 Protection or Restoration

In fault management of optical networks, there are two common approaches

to assure the network survivability, namely preplanned protection and dynamic

restoration. Preplanned protection aims to incorporate protection lightpath at

the network design stage and automatic protection switching can be readily

performed to the designated protection lightpath, once any network failure is

detected. The traffic restoration time can be kept very short. On the contrary,

dynamic restoration would search for the spare lightpaths or network resources

for restoring the disrupted traffic only after the occurrence of network failures.

Although the amount of spare resources can be preallocated, the traffic restor-

ation time may be long ...