<s>
A	O
fiber-optic	B-Algorithm
sensor	I-Algorithm
is	O
a	O
sensor	O
that	O
uses	O
optical	B-Architecture
fiber	I-Architecture
either	O
as	O
the	O
sensing	O
element	O
(	O
"	O
intrinsic	O
sensors	O
"	O
)	O
,	O
or	O
as	O
a	O
means	O
of	O
relaying	O
signals	O
from	O
a	O
remote	O
sensor	O
to	O
the	O
electronics	O
that	O
process	O
the	O
signals	O
(	O
"	O
extrinsic	O
sensors	O
"	O
)	O
.	O
</s>
<s>
Depending	O
on	O
the	O
application	O
,	O
fiber	O
may	O
be	O
used	O
because	O
of	O
its	O
small	O
size	O
,	O
or	O
because	O
no	O
electrical	O
power	O
is	O
needed	O
at	O
the	O
remote	O
location	O
,	O
or	O
because	O
many	O
sensors	O
can	O
be	O
multiplexed	B-Architecture
along	O
the	O
length	O
of	O
a	O
fiber	O
by	O
using	O
light	O
wavelength	O
shift	O
for	O
each	O
sensor	O
,	O
or	O
by	O
sensing	O
the	O
time	O
delay	O
as	O
light	O
passes	O
along	O
the	O
fiber	O
through	O
each	O
sensor	O
.	O
</s>
<s>
Time	O
delay	O
can	O
be	O
determined	O
using	O
a	O
device	O
such	O
as	O
an	O
optical	B-Protocol
time-domain	I-Protocol
reflectometer	I-Protocol
and	O
wavelength	O
shift	O
can	O
be	O
calculated	O
using	O
an	O
instrument	O
implementing	O
optical	O
frequency	O
domain	O
reflectometry	O
.	O
</s>
<s>
Fiber-optic	B-Algorithm
sensors	I-Algorithm
are	O
also	O
immune	O
to	O
electromagnetic	O
interference	O
,	O
and	O
do	O
not	O
conduct	O
electricity	O
so	O
they	O
can	O
be	O
used	O
in	O
places	O
where	O
there	O
is	O
high	O
voltage	O
electricity	O
or	O
flammable	O
material	O
such	O
as	O
jet	O
fuel	O
.	O
</s>
<s>
Fiber-optic	B-Algorithm
sensors	I-Algorithm
can	O
be	O
designed	O
to	O
withstand	O
high	O
temperatures	O
as	O
well	O
.	O
</s>
<s>
Optical	B-Architecture
fibers	I-Architecture
can	O
be	O
used	O
as	O
sensors	O
to	O
measure	O
strain	O
,	O
temperature	O
,	O
pressure	O
and	O
other	O
quantities	O
by	O
modifying	O
a	O
fiber	O
so	O
that	O
the	O
quantity	O
to	O
be	O
measured	O
modulates	O
the	O
intensity	O
,	O
phase	O
,	O
polarization	O
,	O
wavelength	O
or	O
transit	O
time	O
of	O
light	O
in	O
the	O
fiber	O
.	O
</s>
<s>
A	O
particularly	O
useful	O
feature	O
of	O
intrinsic	O
fiber-optic	B-Algorithm
sensors	I-Algorithm
is	O
that	O
they	O
can	O
,	O
if	O
required	O
,	O
provide	O
distributed	O
sensing	O
over	O
very	O
large	O
distances	O
.	O
</s>
<s>
Temperature	O
can	O
be	O
measured	O
by	O
using	O
a	O
fiber	O
that	O
has	O
evanescent	O
loss	O
that	O
varies	O
with	O
temperature	O
,	O
or	O
by	O
analyzing	O
the	O
Rayleigh	O
Scattering	O
,	O
Raman	B-Architecture
scattering	I-Architecture
or	O
the	O
Brillouin	B-Algorithm
scattering	I-Algorithm
in	O
the	O
optical	B-Architecture
fiber	I-Architecture
.	O
</s>
<s>
Optical	B-Architecture
fibers	I-Architecture
are	O
used	O
as	O
hydrophones	O
for	O
seismic	O
and	O
sonar	B-Application
applications	O
.	O
</s>
<s>
The	O
German	O
company	O
Sennheiser	O
developed	O
a	O
laser	O
microphone	O
for	O
use	O
with	O
optical	B-Architecture
fibers	I-Architecture
.	O
</s>
<s>
A	O
fiber-optic	B-Architecture
microphone	O
and	O
fiber-optic	B-Architecture
based	O
headphone	O
are	O
useful	O
in	O
areas	O
with	O
strong	O
electrical	O
or	O
magnetic	O
fields	O
,	O
such	O
as	O
communication	O
amongst	O
the	O
team	O
of	O
people	O
working	O
on	O
a	O
patient	O
inside	O
a	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
machine	O
during	O
MRI-guided	O
surgery	O
.	O
</s>
<s>
Optical	B-Algorithm
fiber	I-Algorithm
sensors	I-Algorithm
for	O
temperature	O
and	O
pressure	O
have	O
been	O
developed	O
for	O
downhole	O
measurement	O
in	O
oil	O
wells	O
.	O
</s>
<s>
The	O
fiber-optic	B-Algorithm
sensor	I-Algorithm
is	O
well	O
suited	O
for	O
this	O
environment	O
as	O
it	O
functions	O
at	O
temperatures	O
too	O
high	O
for	O
semiconductor	O
sensors	O
(	O
distributed	B-Algorithm
temperature	I-Algorithm
sensing	I-Algorithm
)	O
.	O
</s>
<s>
Optical	B-Architecture
fibers	I-Architecture
can	O
be	O
made	O
into	O
interferometric	O
sensors	O
such	O
as	O
fiber-optic	B-Device
gyroscopes	I-Device
,	O
which	O
are	O
used	O
in	O
the	O
Boeing	O
767	O
and	O
in	O
some	O
car	O
models	O
(	O
for	O
navigation	O
purposes	O
)	O
.	O
</s>
<s>
They	O
are	O
also	O
used	O
to	O
make	O
hydrogen	B-Algorithm
sensors	I-Algorithm
.	O
</s>
<s>
Fiber-optic	B-Algorithm
sensors	I-Algorithm
have	O
been	O
developed	O
to	O
measure	O
co-located	O
temperature	O
and	O
strain	O
simultaneously	O
with	O
very	O
high	O
accuracy	O
using	O
fiber	B-Device
Bragg	I-Device
gratings	I-Device
.	O
</s>
<s>
Fiber	B-Algorithm
optic	I-Algorithm
sensors	I-Algorithm
are	O
also	O
particularly	O
well	O
suited	O
for	O
remote	O
monitoring	O
,	O
and	O
they	O
can	O
be	O
interrogated	O
290km	O
away	O
from	O
the	O
monitoring	O
station	O
using	O
an	O
optical	B-Architecture
fiber	I-Architecture
cable	O
.	O
</s>
<s>
Brillouin	B-Algorithm
scattering	I-Algorithm
effects	O
can	O
also	O
be	O
used	O
to	O
detect	O
strain	O
and	O
temperature	O
over	O
large	O
distances	O
(	O
20	O
–	O
120kilometers	O
)	O
.	O
</s>
<s>
A	O
fiber-optic	B-Architecture
AC/DC	O
voltage	O
sensor	O
in	O
the	O
middle	O
and	O
high	O
voltage	O
range	O
(	O
100	O
–	O
2000V	O
)	O
can	O
be	O
created	O
by	O
inducing	O
measurable	O
amounts	O
of	O
Kerr	O
nonlinearity	O
in	O
single	B-Device
mode	I-Device
optical	I-Device
fiber	I-Device
by	O
exposing	O
a	O
calculated	O
length	O
of	O
fiber	O
to	O
the	O
external	O
electric	O
field	O
.	O
</s>
<s>
Fiber-optic	B-Algorithm
sensors	I-Algorithm
are	O
used	O
in	O
electrical	O
switchgear	O
to	O
transmit	O
light	O
from	O
an	O
electrical	O
arc	O
flash	O
to	O
a	O
digital	O
protective	O
relay	O
to	O
enable	O
fast	O
tripping	O
of	O
a	O
breaker	O
to	O
reduce	O
the	O
energy	O
in	O
the	O
arc	O
blast	O
.	O
</s>
<s>
Fiber	B-Device
Bragg	I-Device
grating	I-Device
based	O
fiber-optic	B-Algorithm
sensors	I-Algorithm
significantly	O
enhance	O
performance	O
,	O
efficiency	O
and	O
safety	O
in	O
several	O
industries	O
.	O
</s>
<s>
Fiber	B-Device
Bragg	I-Device
gratings	I-Device
are	O
sensitive	O
to	O
the	O
static	O
pressure	O
,	O
mechanical	O
tension	O
and	O
compression	O
and	O
fiber	O
temperature	O
changes	O
.	O
</s>
<s>
The	O
efficiency	O
of	O
fiber	B-Device
Bragg	I-Device
grating	I-Device
based	O
fiber-optic	B-Algorithm
sensors	I-Algorithm
can	O
be	O
provided	O
by	O
means	O
of	O
central	O
wavelength	O
adjustment	O
of	O
light	O
emitting	O
source	O
in	O
accordance	O
with	O
the	O
current	O
Bragg	B-Device
gratings	I-Device
reflection	O
spectra	O
.	O
</s>
<s>
Extrinsic	O
fiber-optic	B-Algorithm
sensors	I-Algorithm
use	O
an	O
optical	B-Architecture
fiber	I-Architecture
cable	O
,	O
normally	O
a	O
multimode	B-Device
one	O
,	O
to	O
transmit	O
modulated	B-Application
light	O
from	O
either	O
a	O
non-fiber	O
optical	O
sensor	O
,	O
or	O
an	O
electronic	O
sensor	O
connected	O
to	O
an	O
optical	O
transmitter	O
.	O
</s>
<s>
Extrinsic	O
fiber-optic	B-Algorithm
sensors	I-Algorithm
provide	O
excellent	O
protection	O
of	O
measurement	O
signals	O
against	O
noise	O
corruption	O
.	O
</s>
<s>
The	O
modulated	B-Application
voltage	O
level	O
at	O
the	O
output	O
of	O
the	O
PRT	O
can	O
then	O
be	O
injected	O
into	O
the	O
optical	B-Architecture
fiber	I-Architecture
via	O
the	O
usual	O
type	O
of	O
transmitter	O
.	O
</s>
<s>
It	O
is	O
well-known	O
the	O
propagation	O
of	O
light	O
in	O
optical	B-Architecture
fiber	I-Architecture
is	O
confined	O
in	O
the	O
core	O
of	O
the	O
fiber	O
based	O
on	O
the	O
total	O
internal	O
reflection	O
(	O
TIR	O
)	O
principle	O
and	O
near-zero	O
propagation	O
loss	O
within	O
the	O
cladding	O
,	O
which	O
is	O
very	O
important	O
for	O
the	O
optical	O
communication	O
but	O
limits	O
its	O
sensing	O
applications	O
due	O
to	O
the	O
non-interaction	O
of	O
light	O
with	O
surroundings	O
.	O
</s>
<s>
Therefore	O
,	O
it	O
is	O
essential	O
to	O
exploit	O
novel	O
fiber-optic	B-Architecture
structures	O
to	O
disturb	O
the	O
light	O
propagation	O
,	O
thereby	O
enabling	O
the	O
interaction	O
of	O
the	O
light	O
with	O
surroundings	O
and	O
constructing	O
fiber-optic	B-Algorithm
sensors	I-Algorithm
.	O
</s>
<s>
In	O
the	O
above-mentioned	O
fiber-optic	B-Architecture
structures	O
,	O
the	O
enhanced	O
evanescent	O
fields	O
can	O
be	O
efficiently	O
excited	O
to	O
induce	O
the	O
light	O
to	O
expose	O
to	O
and	O
interact	O
with	O
the	O
surrounding	O
medium	O
.	O
</s>
<s>
Due	O
to	O
the	O
rapid	O
progress	O
of	O
functional	O
materials	O
in	O
recent	O
years	O
,	O
various	O
sensing	O
materials	O
are	O
available	O
for	O
fiber-optic	B-Architecture
chemical	O
sensors	O
and	O
biosensors	O
fabrication	O
,	O
including	O
graphene	O
,	O
metals	O
and	O
metal	O
oxides	O
,	O
carbon	O
nanotubes	O
,	O
nanowires	O
,	O
nanoparticles	O
,	O
polymers	O
,	O
quantum	O
dots	O
,	O
etc	O
.	O
</s>
<s>
Consequently	O
,	O
the	O
surrounding	O
changes	O
will	O
be	O
recorded	O
and	O
interrogated	O
by	O
the	O
optical	B-Architecture
fibers	I-Architecture
,	O
realizing	O
sensing	O
functions	O
of	O
optical	B-Architecture
fibers	I-Architecture
.	O
</s>
<s>
Currently	O
,	O
various	O
fiber-optic	B-Architecture
chemical	O
sensors	O
and	O
biosensors	O
have	O
been	O
proposed	O
and	O
demonstrated	O
.	O
</s>
