<s>
Digital	B-Protocol
back-propagation	I-Protocol
(	O
DBP	O
)	O
is	O
a	O
technique	O
for	O
compensating	O
all	O
fiber	B-Architecture
impairments	O
in	O
optical	B-Application
transmission	I-Application
systems	I-Application
.	O
</s>
<s>
DBP	O
uses	O
the	O
back-propagation	O
algorithm	O
in	O
the	O
digital	O
domain	O
by	O
solving	O
the	O
inverse	O
nonlinear	O
Schrödinger	O
equation	O
of	O
the	O
fiber	B-Architecture
link	O
using	O
the	O
split-step	O
Fourier	O
method	O
(	O
SSFM	O
)	O
to	O
calculate	O
the	O
transmitted	O
signal	O
from	O
the	O
received	O
signal	O
.	O
</s>
<s>
In	O
principle	O
,	O
digital	B-Protocol
back-propagation	I-Protocol
is	O
capable	O
of	O
fully	O
reversing	O
the	O
effects	O
of	O
nonlinear	O
propagation	O
in	O
optical	B-Architecture
fibers	I-Architecture
,	O
yet	O
in	O
practice	O
it	O
is	O
limited	O
by	O
the	O
stochastic	O
nature	O
of	O
some	O
impairments	O
,	O
like	O
amplified	O
spontaneous	O
emission	O
and	O
polarization	O
mode	O
dispersion	O
.	O
</s>
