Specialty Optical Fibers Handbook

selecting and concatenating M fibers from the production fiber PMD distribu-

tion, then determining the probability of a maximum PMD being exceeded.

A typical specification may state that the LDV for a given fiber product is

0:04 ps=km

1=2

for M ¼ 20 and Q ¼ 10

3

. This says that when 20 fibers are

randomly concatenated to form links, only 0.1% (Q



100) of these links will

have PMD above 0:04 ps=km

1=2

. Clearly, a specification that requires more

fibers to be used (larger M) or higher fraction of fibers exceeding the specifica-

tion (high Q) is weaker than a low M, low Q specification. The computation of

LDV is often done using the Monte Carlo technique, ...