Specialty Optical Fibers Handbook

ER is merely the ratio of this ‘‘unwanted’’ power, to the amount of power

remaining in the launch axis, typically expressed in decibels:

ER ¼ 10 log

10

(P

u

=P

w

), (8:4)

where

P

u

¼ optical power transferred to the unwanted axis

P

w

¼ optical power remaining in the launch (wanted) axis.

In other words, an ER of 30 dB indicates a ratio of wanted to unwanted

optical power of 1000:1, 20 dB is 100:1, 10 dB is 10:1, and so on.

8.6.8 H-Parameter

Another frequently used measure of PM fiber’s performance is the so-called

H-parameter. The H-parameter is simply an ER, expressed as a decimal (not to be

confused with decibel) per unit length of fiber. For example, an