TELKOM
NIKA
, Vol.13, No
.3, Septembe
r 2015, pp. 8
89~893
ISSN: 1693-6
930,
accredited
A
by DIKTI, De
cree No: 58/DIK
T
I/Kep/2013
DOI
:
10.12928/TELKOMNIKA.v13i3.1726
889
Re
cei
v
ed Ma
rch 9, 2
015;
Re
vised
Ma
y 16, 2015; Accepted June 2,
2015
Optical Fiber Bending Detection on Long Distance
OPGW using OTDR
M. F. M. Salleh*
1,2
, Z. Zakaria
1
1
T
e
lecommu
ni
cation R
e
se
arch & Innovati
on
(CeT
RI),
F
a
cult
y
of Electron
ic
& Computer E
ngi
neer
in
g,
Univers
i
ti T
e
knikal Mal
a
ysi
a
Melak
a
(UT
e
M),
Han
g
T
uah Ja
ya, 7610
0, Duri
an T
ungga
l, Melak
a
, Mala
ysi
a
2
Southern R
e
g
i
on, T
e
lecommunic
a
tion Infras
tructure M
ana
g
e
ment, ICT
Division, T
enag
a Nasio
n
a
l
Berh
ad,
Jala
n Mengk
ib
ol, 860
00, Klu
a
ng, Johor, Mal
a
y
s
ia
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: mfazli.ms
a@
tnb.com.m
y
, za
hr
ila
dh
a@utem
.edu.m
y
A
b
st
r
a
ct
In
Malaysi
a, thousa
nds of kil
o
meters of Optica
l Groun
d W
i
re (OPGW
)
have b
e
e
n
inst
alle
d by
a
utility co
mp
any
.For long dista
n
ce fiber
ca
bl
e
,
there is a po
ssibil
i
ty of opti
c
al fiber to be
nd w
i
th very sma
l
l
radi
us es
peci
a
l
l
y in
j
o
int c
l
osu
r
es w
h
ich
caus
ed
optica
l
pow
er to
attenu
ate
.
T
h
is atten
uati
on
is kn
ow
n a
s
‘be
nd
losses.
Bend
loss
incre
a
ses th
e total
pow
er atten
uat
ion
of o
p
tical fi
ber. In a
d
di
ti
o
n
, fo
r l
o
ng
di
stan
ce
fiber cab
l
e, it is imp
o
rtant to a
v
oid a
n
y extra l
o
ss as
the fibe
r itself attenuat
es
0.2 to 0.35 dB/km a
nd spl
i
c
e
loss a
b
o
u
t 0.1
dB e
a
ch.H
en
ce, in th
is stud
y, the
meth
od of
detecti
ng b
end loss as
w
e
ll as
o
p
tica
l
fi
be
r
ben
din
g
is pre
s
ented. T
he re
sult of
this study is expecte
d
to allow
fiber
i
ndustry pl
ayer
s to determine
the
exact locati
on
and pr
op
er rectificatio
n can b
e
done to so
lve
ben
d loss pr
obl
em.
Ke
y
w
ords
: opt
ical gr
oun
d w
i
re, bend l
o
ss, p
o
w
e
r attenuati
on, optica
l
fiber
bend
Copy
right
©
2015 Un
ive
r
sita
s Ah
mad
Dah
l
an
. All rig
h
t
s r
ese
rved
.
1. Introduc
tion
Optical
po
we
r
atten
uation
increa
se
s as the
len
g
th of fiber ca
ble
i
n
cre
a
ses.
Opti
cal
fib
e
r
itself cau
s
e
s
t
he p
o
wer to a
ttenuate a
b
o
u
t 0.2
dB
/km
for 1
550
nm
wavele
ngth t
o
0.35
dB/km
for
1310 nm wa
velength [1]. By
taking into account
other facto
r
s that can co
ntribute to the
attenuation o
f
power for lo
ng distan
ce
such a
s
dispersion lo
ss, scattering lo
ss
etc., bending
of
optical fibe
r a
l
so can affect
the powe
r
attenuatio
n [2].
Bend loss is i
n
trodu
ce
d by Mode Field
Diameter (MF
D
) [3, 4]. MFD rep
r
e
s
ent
s the area
in whi
c
h the li
ght goe
s thro
ugh a
nd in
clu
des th
e core
and a
part of
the cla
dding.
A smalle
r mo
de
field diam
eter indi
cate
s tha
t
light is more
tightly
co
nfin
ed to th
e fibre
ce
ntre
and, t
herefo
r
e
is le
ss
pron
e to lea
k
age when the
fibre is loo
p
e
d
[4]. Figure
1 sho
w
s the relation
ship of
light powe
r
a
nd
MFD where
the diameter of co
re a
nd the wave
length
s
are
the importa
n
t
paramete
r
s in
determi
ning t
he se
nsitivity of bend lo
ss.
Figure 1. The
relation
ship
betwe
en light
and MFD
The total nu
mber of mod
e
s supp
orted
in a
curved,
multimode fib
r
e is the
r
efore relate
d
to the index profile, the prop
agatin
g wavele
ngth,
and the radi
us of curvat
ure a
s
sho
w
n in
Equation (1).
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 16
93-6
930
TELKOM
NIKA
Vol. 13, No. 3, September 20
15 : 889 – 893
890
∞
1
∆
(
1
)
Whe
r
e N
∞
is the n
u
mbe
r
of mode
s
su
pporte
d in
a
straig
ht fibre,
α
define
s
th
e ind
e
x
profile,
∆
i
s
t
he
core-clad
d
ing in
dex dif
f
eren
ce, n
2
i
s
the
claddi
ng
index,
k = 2
π
/
λ
an
d
R is
the
radiu
s
of cu
rv
ature of the b
end [5].
Ho
wever, si
n
g
le mode fibre has a large
r
mode field
diamete
r
at 1550 nm than
at 1310
nm and
at 1
625 nm
than
at 1550
nm.
Larg
e
r
mod
e
fi
elds
are
sensitive to lat
e
ral off
s
et du
ring
spli
cing, b
u
t they are
more
sen
s
itive to l
o
sse
s
in
curre
d
by ben
ding
durin
g in
stall
a
tion or i
n
th
e
cabli
ng p
r
o
c
e
ss [4]. 15
50n
m is mo
re
se
nsitive to ben
d in the fibre
than 13
10nm
. This indi
cat
e
s
that longer
wavelength
will enco
unter lo
ss d
ue to the bendi
ng at the same
radi
u
s
, R.
Bend lo
ss is
measured in
dB and
ha
s d
i
rect
re
latio
n
ship with
ra
diu
s
of b
endi
ng
with th
e
critical ra
diu
s
of curvatu
r
e, R
c
is define
d
by [6] and [7]
as Equatio
n (2).
.
(
2
)
W
h
er
e R
c
is the
criti
c
al
rad
i
us
of b
endin
g
, n
2
i
s
the
re
fractive i
ndex
of the
cl
ad
a
nd
NA
is
the nume
r
i
c
al
apertu
re
of the fibre
and
λ
is th
e wavelength. Fig
u
r
e 2
sh
ows t
he sen
s
itivity of
different wav
e
length
s
on b
end ra
diu
s
.
Figure 2. 1310 nm vs. 15
50 nm on dia
m
eter of ben
d [5]
Optical Ti
me
-Do
m
ain
Refl
ectomete
rs a
r
e the id
eal
tools for
det
ecting a
nd l
o
catin
g
bend
s in
a fib
r
e lin
k. As
be
nd is sen
s
itive to lon
ger wavelength
s
b
u
t not for
sh
o
r
ter
wavele
ng
ths,
most of the
o
perato
r
s u
s
e
two wavelen
g
t
hs fro
m
OT
DR to te
st the
fibre lin
ks. Th
e wavel
ength
s
that comm
onl
y used fo
r det
ecting
ben
d l
o
ss are 13
10
nm and
155
0
nm. The
s
e t
w
o
wavelen
g
t
h
s
will be u
s
ed i
n
this pap
er f
o
r that pu
rpo
s
e. For futu
re
analysi
s
on
bendi
ng lo
ss
sho
u
ld be ta
ken
betwe
en 1
3
1
0
nm an
d 1
625 nm, o
r
betwe
en 1
5
5
0
nm an
d 1
625 nm,
whi
c
h a
r
e
relev
ant
wavelengths
for DWDM testing.
2. Rese
arch
Metho
d
The
scope
of
this
study i
s
to dete
c
t th
e be
nd l
o
ss
as
well
a
s
o
p
tical fib
e
r b
end. T
h
e
activities
are
divided i
n
to t
w
o. T
he fi
rst
activity is
to
d
e
tect a
n
y b
e
n
d
lo
sses that
occur al
ong
the
link
while the second activity invo
lves the ob
se
rvatio
n at site to
verify the test
s that have b
e
en
done in the first activity.
2.1. Bend Lo
ss De
tec
t
ion
This
activity involves two
different wa
velength
s
fro
m
OTDR
whi
c
h a
r
e
1310
nm an
d
1550 nm
wav
e
length
s
. As
discu
s
sed in
[5], the
value of bend losses captu
r
ed
by 1550 nm
will
be highe
r tha
n
1310 nm b
y
at least 0.2
d
B. This
will allow the pro
c
e
ss of dete
c
ting the prese
n
ce
of bend. As
shown in Figu
re 3, the 15
5
0
nm tr
a
c
e i
s
attenuated
more tha
n
13
10 nm at du
e
to
bend lo
ss at the sam
e
loca
tion.
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
1693-6
930
Optical Fib
e
r
Bending
Dete
ction on L
ong
Dist
an
ce OP
GW u
s
ing O
T
DR (M. F. M.
Salleh)
891
Figure 3. Tra
c
e compa
r
i
s
o
n
betwe
en 15
50 nm and 1
3
10 nm due to
bend lo
ss
Since the
r
e
might be mo
re than sin
g
le
location
s of bendi
ng for l
ong lon
g
dist
ance fiber
cabl
e, the
co
mpari
s
o
n
of l
o
ss valu
es h
a
s to
be
do
n
e
at e
a
ch lo
cation
whe
r
e t
here
is hig
h
l
o
ss
detecte
d by 1550 nm.
Table 1. Meth
od of detectin
g
bend lo
ss
1550 n
m
1310 n
m
Loss Diff
erent
Remark
Distan
ce
Loss
Distan
ce
Loss
A x
B
Y
x
-
y
If x-
y > 0.2dB, t
h
ere is
optical fiber bending
occur
Distance A and B
will be
slightly differen
t. The val
u
e of A and B
have to
be
compared
with joint clo
s
ure sche
dul
e provide
d
b
y
the proj
ect
owne
r. To d
e
cid
e
the exact location, the
distan
ce p
o
in
t toleran
c
e will be cal
c
ulat
ed by
mea
s
u
r
ing the ave
r
age di
stan
ce
betwee
n
ea
ch
high voltage t
r
an
smi
ssi
on towe
rs.
(
3
)
In this study, the distan
ce
point tolera
nce is
given by ±400 m whe
r
e the location
of bend
fiber will be determined by
acceptin
g the nearest
poi
nt to the loca
tion of j
o
int
cl
osure as
stated
by joint closure sched
ule.
2.2. Optical Fiber Ben
d
After the lo
ca
tion of rel
a
ted
joint cl
osure
s
have
be
en
determi
ned, t
he ob
se
rvatio
n on th
e
coilin
g o
p
tica
l fiber in
side
the joi
n
t
clo
s
ure
hav
e
b
een
don
e in
order to
se
e if the
r
e i
s
any
bendi
ng with
small
radiu
s
t
hat pro
bably
cau
s
e
s
the b
end lo
ss. Th
e scop
e of o
b
se
rvation i
s
to
verify if there is any defe
c
t on opt
ical fiber in the joint clo
s
ure.
Since
ben
d l
o
ss
can
be
solved by
rele
asin
g the
be
nding, thi
s
m
e
thod
will
be
used t
o
verify that the
ben
ding
of
o
p
tical fib
e
r is the
cau
s
e
of
b
end l
o
ss. An
o
t
her te
st u
s
in
g OT
DR
will
be
done to see
this activity and to prov
e that the location d
e
termination ha
s been cond
u
c
ted
cor
r
e
c
t
l
y
.
3. Results a
nd Analy
s
is
Re
sults of th
e experim
ent
wereanaly
z
ed in
order
to determin
e
w
heth
e
r the
method
impleme
n
ted in this study is able to detect
bend lo
ss as well as th
e location of bendi
ng optical
fiber. The results of the experim
ents a
r
e
then veri
fied
by the obse
r
v
a
tion activity and rectificati
on
activity. Since the b
endin
g
of opti
c
al fi
ber
do n
o
t gi
ve any pe
rm
anent effe
ct
on be
nd lo
ss and
attenuation, the re
sult
s of this
study can be p
r
ove
n
as cond
uct
ed with p
r
op
er metho
d
a
n
d
analysi
s
by test con
d
u
c
ted
after the ben
ding of optica
l
fiber is rel
e
a
s
ed.
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 16
93-6
930
TELKOM
NIKA
Vol. 13, No. 3, September 20
15 : 889 – 893
892
3.1. Bend Lo
ss De
tec
t
ion
Losse
s that a
r
e ca
ptured b
y
1310 nm a
nd
155
0 nm wavele
ngth
s
have been a
nalyze
d
whe
r
e th
e e
v
ent table
ca
n be
extra
c
t
ed fro
m
O
T
DR.
The
re
sults of
OT
DR te
st have
been
arrang
ed as
i
n
Ta
ble 2 with
di
stan
ce m
easur
e
d
by
1
310 nm and
1550
nm
wavelength
ha
s b
een
aligne
d acco
rdingly by taki
ng into acco
u
n
t the distan
ce point tolera
nce.
Table 2. Ben
d
and splice loss differenti
a
tion.
Wav
e
len
g
t
h
Loss Diff
erent
Remark
1550 n
m
1310 n
m
Distan
ce
Loss
Distan
ce
Loss
6246.58
0.108
6226.03
0.142
-0.034
Splice
11044.52
-0.256
11136.99
-0.214
-0.042
Splice
14486.30
0.247
14496.58
0.274
-0.027
Splice
20404.11
1.634
1.634
Bend
23229.45
0.677
23183.22
0.047
0.630
Bend
27981.17
0.230
27991.44
0.221
0.009
Splice
30000.00
1.910
30092.47
0.184
1.726
Bend
35953.77
0.216
35902.40
0.193
0.023
Splice
38275.69
-0.147
38121.58
-0.153
0.006
Splice
41928.09
0.103
0.103
Splice
47799.66
0.316
0.316
Bend
54652.40
End
54929.8
End
The
re
sults from OT
DR te
st have
sho
w
n that the
r
e
were fou
r
be
nd lo
sse
s
fou
nd al
ong
the fiber lin
k.
These be
nd
losse
s
indi
cate that
there we
re fou
r
possibl
e loca
tions of b
end
ing
optical fibe
r. To cla
r
ify these re
sult
s, the
observatio
n
on site ha
s been co
ndu
cted to dete
c
t if
there
wa
sb
en
ding o
p
tical
fiber th
at migh
t prob
abily in
trodu
ce th
e b
end lo
sse
s
capture
d
in thi
s
experim
ent.
3.2. Bending
Optical Fibe
r
The ob
se
rvati
ons
of ben
din
g
optical fiber
have be
en d
one o
n
four l
o
catio
n
s
as
d
e
cid
ed
earlie
r. The
r
e
were multipl
e
bendi
ng op
tical fiber
with very small
radiu
s
o
b
serv
ed occu
r in j
o
int
clo
s
ures. T
h
ese
ben
ding
s are
believe
d
as th
e fact
o
r
to the
pre
s
ence of b
end
loss. Figu
re
4,
Figure 5, Figure 6 an
d Figure 7
sho
w
the mu
ltiple bending o
p
tical fibers fo
und in
side jo
int
clo
s
ures.
Figure 4. Three ben
ding fo
und at Lo
cati
on 1
Figure 5. Three ben
ding fo
und at Lo
cati
on 2
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
1693-6
930
Optical Fib
e
r
Bending
Dete
ction on L
ong
Dist
an
ce OP
GW u
s
ing O
T
DR (M. F. M.
Salleh)
893
Figure 6. Three ben
ding fo
und at Lo
cati
on 3
Figure 7. Three ben
ding fo
und at Lo
cati
on 5
All these
ben
ding
s ha
d be
en relea
s
ed
and the
re
sul
t
s obtain
ed from OT
DR T
e
st afte
r
the rectification at th
ese fo
ur lo
catio
n
s showed th
at th
ere
wa
s no
lo
nger be
nd l
o
ss fou
nd. Fi
gu
re
8 sho
w
s the
trace
s
of 1310 nm and
1550 nm wavelength wit
h
no more p
o
int of high loss
detecte
d by 1550 nm wave
length a
s
bef
ore.
Figure 8. Tra
c
e
s
of 1310 a
nd 155
0 nm
wavele
ngth without high lo
ss p
o
ints
4. Conclusio
n
The metho
d
of detectin
g
bend lo
ss on existing
long dista
n
ce OPG
W
h
a
s be
en
impleme
n
ted su
ccessfully. The re
su
lts of
OT
DR test
h
ad b
een
u
s
ed
to tra
c
e
the
l
o
catio
n
of
be
nd
loss a
s
well
as b
endin
g
o
p
tical fibe
r a
nd ob
se
rvatio
n activities fo
und that the
r
e we
re multi
p
le
bendi
ng
s wit
h
small radi
us contri
bute
to the
bend
loss. Th
e finding
s ha
d been ve
rified
as
rectification o
n
that locatio
n
s succe
s
sf
ully c
l
eared the los
s
from OTDR trac
es
.
Referen
ces
[1]
T
enaga Nasi
on
al Berh
ad. T
e
lecommunic
a
tio
n
Gu
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