
8.6.6 Beat Length (L
p
)
Beat length is arguably the parameter that best represents the fundamental
ability of a PM fiber to preserve polarization. Beat length is particularly useful
because, unlike H-parameter or extinction ratio (ER), it is independent of fiber
length or the way in which the fiber has been deployed. H-parameter and ER will
both be affected adversely by high winding tensions, small coil diameters, point
intrusions, or multilayered winds, whereas beat length will remain constant. For
this reason, beat length is an invaluable tool that enables you to compare the PM
properties of different fibers; put quite simply, the shorter the beat ...