<s>
Dispersion-shifted	B-Device
fiber	I-Device
(	O
DSF	O
)	O
is	O
a	O
type	O
of	O
optical	B-Architecture
fiber	I-Architecture
made	O
to	O
optimize	O
both	O
low	O
dispersion	O
and	O
low	O
attenuation	O
.	O
</s>
<s>
Dispersion	B-Device
Shifted	I-Device
Fiber	I-Device
is	O
a	O
type	O
of	O
single-mode	B-Device
optical	I-Device
fiber	I-Device
with	O
a	O
core-clad	O
index	O
profile	O
tailored	O
to	O
shift	O
the	O
zero-dispersion	B-Device
wavelength	I-Device
from	O
the	O
natural	O
1300	O
nm	O
in	O
silica-glass	O
fibers	O
to	O
the	O
minimum-loss	O
window	O
at	O
1550nm	O
.	O
</s>
<s>
The	O
group	O
velocity	O
or	O
intramodal	O
dispersion	O
which	O
dominates	O
in	O
single-mode	B-Device
fibers	I-Device
includes	O
both	O
material	O
and	O
waveguide	O
dispersion	O
.	O
</s>
<s>
However	O
,	O
when	O
used	O
in	O
wavelength	B-Architecture
division	I-Architecture
multiplexing	I-Architecture
systems	O
,	O
dispersion-shifted	B-Device
fibers	I-Device
can	O
suffer	O
from	O
four-wave	O
mixing	O
which	O
causes	O
intermodulation	O
of	O
the	O
independent	O
signals	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
nonzero	B-Architecture
dispersion	I-Architecture
shifted	I-Architecture
fiber	I-Architecture
is	O
often	O
used	O
.	O
</s>
<s>
Dispersion-shifted	B-Device
fiber	I-Device
is	O
specified	O
in	O
ITU-T	O
G.653	O
.	O
</s>
