
16-11Electric Current Sensors
Optical ber is made from materials that have much lower sensitivity than the magneto-optic crystals
us
ed
fo
r
bu
lk
se
nsors,
bu
t
th
eir
se
nsitivity
ca
n
be in
creased
by usi
ng
a hi
gher
nu
mber
of tu
rns
of th
e
b
er
wo
und
ar
ound
th
e
me
asured
co
nductor
. Fi
ber-optic
se
nsors
ar
e
sim
ple
de
vices;
th
ey
su
er
fr
om
th
e
s
purious
b
irefringence
i
nduced
i
n
b
ent
bers
[
29]
.
Co
mmercially
av
ailable
al
l-ber
cu
rrent
se
nsors
are ma
nufactured
by AB
B
si
nce
20
05
. e
se
de
vices
al
so
us
e
tw
o
ci
rcularly
po
larized
li
ght
wa
ves
tr
avelling
in th
e
sa
me
di
rection
. e pha
se
di
erence
ca
used
by th
e
ma
gnetic
e
ld
is me
asured
by th
e
in
terferometer
. i
s