The difference in these delays is called " differential delay " ( D ).
2.
Several heuristics based algorithms exist, that attempt to minimize the differential delay to provide a solution.
3.
In reality, the differential delay that might be required to equalise may be many hundreds of microseconds.
4.
However, it creates differential delay whereby each path that is created, represented by a VT has a different propagational delay across the network.
5.
The major problem with differential delay is the requirement for high speed buffers at the receiving node to store incoming information while all paths converge.
6.
This need for buffer space eventually increases the network cost, so it is very important to select paths that minimize the differential delay, which is directly proportional to the buffer space required.
7.
Essentially, one splits the output of the fiber into two principal polarizations ( usually those with " d & tau; " " d & omega; " = 0, i . e . no first-order variation of time-delay with frequency ), and applies a differential delay to bring them back into synch.
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