<s>
In	O
a	O
single-mode	B-Device
optical	I-Device
fiber	I-Device
,	O
the	O
zero-dispersion	B-Device
wavelength	I-Device
is	O
the	O
wavelength	O
or	O
wavelengths	O
at	O
which	O
material	O
dispersion	O
and	O
waveguide	O
dispersion	O
cancel	O
one	O
another	O
.	O
</s>
<s>
In	O
all	O
silica-based	O
optical	B-Architecture
fibers	I-Architecture
,	O
minimum	O
material	O
dispersion	O
occurs	O
naturally	O
at	O
a	O
wavelength	O
of	O
approximately	O
1300nm	O
.	O
</s>
<s>
Single-mode	B-Device
fibers	I-Device
may	O
be	O
made	O
of	O
silica-based	O
glasses	O
containing	O
dopants	O
that	O
shift	O
the	O
material-dispersion	O
wavelength	O
,	O
and	O
thus	O
,	O
the	O
zero-dispersion	B-Device
wavelength	I-Device
,	O
toward	O
the	O
minimum-loss	O
window	O
at	O
approximately	O
1550nm	O
.	O
</s>
<s>
Such	O
fiber	O
is	O
called	O
dispersion-shifted	B-Device
fiber	I-Device
.	O
</s>
<s>
Another	O
way	O
to	O
alter	O
the	O
dispersion	O
is	O
changing	O
the	O
core	O
size	O
and	O
the	O
refractive	O
indices	O
of	O
the	O
material	O
of	O
core	O
and	O
cladding	B-Device
.	O
</s>
<s>
Because	O
fiber	B-Architecture
optic	I-Architecture
materials	O
are	O
already	O
highly	O
optimized	O
for	O
low	O
scattering	O
and	O
high	O
transparency	O
alternative	O
ways	O
to	O
change	O
the	O
refractive	O
index	O
were	O
investigated	O
.	O
</s>
<s>
As	O
a	O
straightforward	O
solution	O
tapered	O
fibers	O
and	O
holey	B-Device
fibers	I-Device
or	O
photonic	B-Device
crystal	I-Device
fibers	I-Device
(	O
PCF	O
)	O
were	O
produced	O
.	O
</s>
<s>
Essentially	O
they	O
replace	O
the	O
cladding	B-Device
by	O
air	O
.	O
</s>
<s>
As	O
these	O
narrow	O
waveguides	O
(	O
~	O
1-3μm	O
core	O
diameter	O
)	O
are	O
combined	O
with	O
ultrashort	O
pulses	O
at	O
the	O
zero-dispersion	B-Device
wavelength	I-Device
pulses	O
are	O
not	O
instantly	O
destroyed	O
by	O
dispersion	O
.	O
</s>
<s>
The	O
term	O
is	O
also	O
used	O
,	O
more	O
loosely	O
,	O
in	O
multi-mode	B-Device
optical	I-Device
fiber	I-Device
.	O
</s>
<s>
This	O
is	O
more	O
accurately	O
called	O
the	O
minimum-dispersion	B-Device
wavelength	I-Device
.	O
</s>
<s>
The	O
rate	O
of	O
change	O
of	O
dispersion	O
with	O
respect	O
to	O
wavelength	O
at	O
the	O
zero-dispersion	O
point	O
is	O
called	O
the	O
zero-dispersion	B-Device
slope	I-Device
.	O
</s>
<s>
Doubly	B-Device
and	O
quadruply	B-Device
clad	I-Device
single-mode	B-Device
fibers	I-Device
have	O
two	O
zero-dispersion	O
points	O
.	O
</s>
