sampled coherent receivers [43, 44] through off-line DSP. It is expected that
polarization-diversity DSCOR can similarly provide the EPMDC function. To
compensate for PMD, we can rewrite Eqn (4.38) so that the coef ficients h
ij
of
the matrix H are replaced by FIR filters:
z
1
kðÞ
z
2
kðÞ
=
X
B=2
l = B=2
h
11
lðÞ h
12
lðÞ
h
21
lðÞ h
22
lðÞ
y
1
k þlðÞ
y
2
k þlðÞ
;
(4.42)
k is the sampling time index. To eff ectively compensate for PMD, the FIR filter
length B þ1 of the equalization filters h
ij
(l) should be longer than the maximum
differential group delay divided by the sampling time T
s
.
The constant modulus algorithm using an unrestricted full FIR filter in place of
each of the matrix coefficients can be potentially simplified by accepting certain
performance restrictions, ...