<s>
Cladding	B-Device
in	O
optical	B-Architecture
fibers	I-Architecture
is	O
one	O
or	O
more	O
layers	O
of	O
materials	O
of	O
lower	O
refractive	O
index	O
in	O
intimate	O
contact	O
with	O
a	O
core	B-Device
material	O
of	O
higher	O
refractive	O
index	O
.	O
</s>
<s>
The	O
cladding	B-Device
causes	O
light	O
to	O
be	O
confined	O
to	O
the	O
core	B-Device
of	O
the	O
fiber	O
by	O
total	O
internal	O
reflection	O
at	O
the	O
boundary	O
between	O
the	O
core	B-Device
and	O
cladding	B-Device
.	O
</s>
<s>
Light	O
propagation	O
within	O
the	O
cladding	B-Device
is	O
typically	O
suppressed	O
for	O
most	O
fibers	O
.	O
</s>
<s>
However	O
,	O
some	O
fibers	O
can	O
support	O
cladding	B-Device
modes	O
in	O
which	O
light	O
propagates	O
through	O
the	O
cladding	B-Device
as	O
well	O
as	O
the	O
core	B-Device
.	O
</s>
<s>
Depending	O
upon	O
the	O
quantity	O
of	O
modes	O
that	O
are	O
supported	O
,	O
they	O
are	O
referred	O
to	O
as	O
multi-mode	B-Device
fibers	I-Device
and	O
single-mode	B-Device
fibers	I-Device
.	O
</s>
<s>
Improving	O
transmission	O
through	O
fibers	O
by	O
applying	O
a	O
cladding	B-Device
was	O
discovered	O
in	O
1953	O
by	O
Dutch	O
scientist	O
Bram	O
van	O
Heel	O
.	O
</s>
<s>
The	O
fact	O
that	O
transmission	O
through	O
fibers	O
could	O
be	O
improved	O
by	O
applying	O
a	O
cladding	B-Device
was	O
discovered	O
in	O
1953	O
by	O
van	O
Heel	O
,	O
who	O
used	O
it	O
to	O
demonstrate	O
image	O
transmission	O
through	O
a	O
bundle	O
of	O
optical	B-Architecture
fibers	I-Architecture
.	O
</s>
<s>
Early	O
cladding	B-Device
materials	O
included	O
oils	O
,	O
waxes	O
,	O
and	O
polymers	B-Language
.	O
</s>
<s>
Lawrence	O
E	O
.	O
Curtiss	O
at	O
the	O
University	O
of	O
Michigan	O
developed	O
the	O
first	O
glass	O
cladding	B-Device
in	O
1956	O
,	O
by	O
inserting	O
a	O
glass	O
rod	O
into	O
a	O
tube	O
of	O
glass	O
with	O
a	O
lower	O
refractive	O
index	O
,	O
fusing	O
the	O
two	O
together	O
,	O
and	O
drawing	O
the	O
composite	O
structure	O
into	O
an	O
optical	B-Architecture
fiber	I-Architecture
.	O
</s>
<s>
A	O
cladding	B-Device
mode	O
is	O
a	O
mode	O
that	O
is	O
confined	O
to	O
the	O
cladding	B-Device
of	O
an	O
optical	B-Architecture
fiber	I-Architecture
by	O
virtue	O
of	O
the	O
fact	O
that	O
the	O
cladding	B-Device
has	O
a	O
higher	O
refractive	O
index	O
than	O
the	O
surrounding	O
medium	O
,	O
which	O
is	O
either	O
air	O
or	O
the	O
primary	O
polymer	B-Language
overcoat	O
.	O
</s>
<s>
Modern	O
fibers	O
have	O
a	O
primary	O
polymer	B-Language
overcoat	O
with	O
a	O
refractive	O
index	O
that	O
is	O
slightly	O
higher	O
than	O
that	O
of	O
the	O
cladding	B-Device
,	O
so	O
that	O
light	O
propagating	O
in	O
the	O
cladding	B-Device
is	O
rapidly	O
attenuated	O
and	O
disappears	O
after	O
only	O
a	O
few	O
centimeters	O
of	O
propagation	O
.	O
</s>
<s>
An	O
exception	O
to	O
this	O
is	O
double-clad	B-Device
fiber	I-Device
,	O
which	O
is	O
designed	O
to	O
support	O
a	O
mode	O
in	O
its	O
inner	O
cladding	B-Device
,	O
as	O
well	O
as	O
one	O
in	O
its	O
core	B-Device
.	O
</s>
<s>
The	O
inclusion	O
of	O
a	O
glass	O
cladding	B-Device
greatly	O
reduces	O
the	O
attenuation	O
caused	O
by	O
these	O
surface	O
irregularities	O
.	O
</s>
<s>
This	O
is	O
due	O
to	O
the	O
light	O
scattering	O
less	O
at	O
the	O
glass/glass	O
interface	O
than	O
it	O
would	O
have	O
at	O
the	O
glass/air	O
interface	O
for	O
a	O
fiber	O
without	O
cladding	B-Device
.	O
</s>
<s>
The	O
two	O
primary	O
factors	O
that	O
allow	O
for	O
this	O
are	O
the	O
smaller	O
change	O
in	O
index	O
of	O
refraction	O
seen	O
between	O
two	O
surfaces	O
of	O
glass	O
,	O
as	O
well	O
as	O
surface	O
irregularities	O
on	O
the	O
cladding	B-Device
not	O
interfering	O
with	O
the	O
light	O
beams	O
.	O
</s>
<s>
The	O
inclusion	O
of	O
glass	O
cladding	B-Device
is	O
also	O
an	O
improvement	O
over	O
just	O
applying	O
a	O
polymer	B-Language
coating	O
,	O
as	O
glass	O
will	O
typically	O
be	O
stronger	O
,	O
more	O
homogenous	O
,	O
and	O
cleaner	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
inclusion	O
of	O
a	O
cladding	B-Device
layer	O
also	O
allows	O
for	O
the	O
usage	O
of	O
smaller	O
glass	O
fiber	B-Device
cores	I-Device
.	O
</s>
<s>
With	O
most	O
glass	O
fibers	O
have	O
a	O
cladding	B-Device
that	O
raises	O
the	O
total	O
outer	O
diameter	O
to	O
125	O
microns	O
.	O
</s>
<s>
The	O
numerical	O
aperture	O
of	O
a	O
multimode	B-Device
optical	I-Device
fiber	I-Device
is	O
a	O
function	O
of	O
the	O
indices	O
of	O
refraction	O
of	O
the	O
cladding	B-Device
and	O
the	O
core	B-Device
:	O
</s>
<s>
Which	O
will	O
give	O
the	O
maximum	O
angle	O
at	O
which	O
the	O
incidence	O
light	O
can	O
enter	O
the	O
core	B-Device
and	O
maintain	O
total	O
internal	O
reflection	O
:	O
</s>
<s>
is	O
the	O
index	O
of	O
refraction	O
of	O
the	O
cladding	B-Device
.	O
</s>
<s>
Fiber	B-Architecture
optic	I-Architecture
cores	O
and	O
cladding	B-Device
are	O
typically	O
made	O
from	O
highly	O
purified	O
silica	O
glass	O
due	O
to	O
its	O
excellent	O
transmission	O
of	O
light	O
.	O
</s>
<s>
ClearCurve	B-Device
is	O
a	O
fiber	B-Architecture
optic	I-Architecture
cable	O
created	O
by	O
Corning	O
in	O
which	O
alterations	O
to	O
the	O
cladding	B-Device
allow	O
for	O
a	O
fiber	O
to	O
be	O
made	O
hundreds	O
of	O
times	O
more	O
flexible	O
than	O
traditional	O
fibers	O
.	O
</s>
