International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
Detection of Step ,V-Groove and Macro
Bending losses in Optical fibers
M.S.V.Vara Prasad#1, K.Krishna Murthy*2
1,2
Department of electronics, P.G. Center, P. B. Siddhartha College of Arts & Science,
Vijayawada,A.P.India.520010.
ABSTRACT - A systematic study of power loss through
optical fiber undergoes
In the present work an attempt is made to
micro and macro bends .This
detect the loss of power in the optical fibers . This
important loss mechanism when the fiber is pulled along
has been done by the optical fibers practically the
the road from one place to another place, along the side of
the road is some bends will produced small systematic
known length of fiber is bending 900 ( step bending)
perturbations to the fiber causing a loss of power. The
and 600, 450 ( V-groove bending )
fiber is to be bend in a groove along the edges of the wall
bending and macro bending. In this method the out
or a door or a window the cable has bend necessarily by 90
power is noted. A graph is drawn between the no. of
degrees or 60,45 degrees or less than 45 degrees
bends and the out power and also be drawn for
depending upon the requirement. Such bending in tight
diameter bends will rise the attenuation thus in the present
work. The power loss in the case of micro bending is large
as compared to macro bending. Within the micro bending,
i.e micro
macro bending, Bending radius and the output
power.
II. EXPERIMENTAL ARRANGEMENT
it is observed that as the number of bends increase the
output power also increases i.e. the loss of power
The experimental setup for study of various
increases. It is also observed that the power loss is more in
losses is shown in Fig1 (a),(b), with two step
the case of (45degrees bending) V groove bending than in
bending and v groove bending with loads varying
the case of (90degrees bending)- step groove bending.
Key words- Bending,, optical fiber, loss, Step and VGroove bends, Macro bend.
from 20gm to 100gm and Fig.1 (c) macro bending.
The bends are made from good quality wood cut at
45 degrees and 90 degrees as shown in figure. The
sufficient care is taken that the edges of the v groove
I . INTRODUCTION
or step groove are not very sharp because its’ sharp
The basic principle is to detect the
variation in the wavelength, intensity or
edges may breaks the fiber material(glass).
Fig 1 (a) Micro bending step groove
phase or polarization of an optical wave
traversing through an optical fiber, due to the
effect of measured and related to it
quantitatively. Due to the absence of electro
magnetic interference, greater sensitivity[18], easy to realize, and smaller in size and
low cost optical fiber sensors are becoming
very popular.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
energy of the guided mode is cross coupled into
leaky modes, This cross coupling leaks to the loss
through the cladding in some cases becomes
inevitable to allow the bend to negotiate corners
during the installation of fibers in cable ducts or
poles for transmission line. In some other case, the
bending may be short and introduce certain loss in
Fig 1 (b) Micro bending V groove bending
the fiber.
Fiber cable
m ic r o b e n d in g ( v - g r o o v e )
f ib e r d ia 9 /1 2 5  m ,s o u r c e :1 3 1 0 n m
p o w e r la n c h in g in to th e fib e r :- 3 .3 5 d b m
-5
-1 0
Source of lightlaser Diode
(OTDR)
Power meter
out put power(dbm)
Connector
-1 5
-2 0
-2 5
2 V groov e be nds
4 V groov e be nds
6 V groov e be nds
-3 0
0 g m 1 0 g m 2 0 g m 3 0 g m 4 0 g m 5 0 g m 6 0 g m 7 0 g m 8 0 g m 9 0 g m1 0 0 g m
w e ig h t in g m
Graph (a)
- 10
- 12
- 14
m icr o b e n d in g ;V g ro o v e b e n d in g
so u r ce o f lig h t= 1 3 1 0 n m
fib e r d ia 8 /1 2 0  m
p o w e r la n c h in g in to fib e r= -6 .4 8 d b m
- 16
- 18
out put power(dbm)
- 20
- 22
- 24
1
2
4
6
- 26
- 28
- 30
V
V
V
V
gr o ov e
gr o ov e
gr o ov e
gr o ov e
b e nd
b e nd
b e nd
b e nd
- 32
- 34
- 36
- 38
- 40
Fig.1(c)Experimental arrangement forMacro bending
20
40
60
80
1 00
12 0
14 0
w e ig h t in g m
Fig.1 (a),(b,(c) Micro bending , Macro bending
Graph (b)
arrangements.
III. EXPERIMENTAL RESULTS
- 20
m ic ro b e n d in g (v -g ro o v e )
fib e r d ia 9 /1 2 5  m ,s o u rc e :1 5 5 0 n m
p o w e r la n c h in g in to th e fib e r:-3 .2 5 d b m
- 25
room free from external vibrations since the glass
fiber is selected for experiment is very light and
delicate. Two sources of lights was predominantly
out put power(dbm)
The experiment was carried out in a closed
- 30
- 35
- 40
2 V g ro o v e b e n d s
4 V g ro o v e b e n d s
6 V g ro o v e b e n d s
- 45
- 50
- 55
- 60
0 g m 1 0 g m2 0 g m3 0 g m4 0 g m 5 0 g m6 0 g m 7 0 g m 8 0 g m9 0 g m1 0 0 g m
selected to study the loss, if any for the same type of
fiber subjected to same loading and similar bending.
--
w e ig h t in g m
Graph (c)
Micro bends have small random deviations about a
small nominal straight line positions. These are
observed in cable fibers. The micro bend loss occurs
due to the fact, That small bends act as scattering
which causes more coupling to take place. The
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
-1 5
-5
-2 0
m ic r o b e n d i n g ; V g r o o v e b e n d in g
s o u r c e o f li g h t = 1 5 5 0 n m
f ib e r d ia 8 / 1 2 0  m
p o w e r la n c h in g in to f ib e r = - 5 . 9 5 d b m
-15
-3 0
-3 5
-4 0
1
2
4
6
-4 5
V
V
V
V
g ro o v e
g ro o v e
g ro o v e
g ro o v e
bend
bend
bend
bend
out put power(dBm)
out put power(dbm)
-2 5
-10
-20
-25
-30
microbenbing
type of groove :step groove
source of light :1550nm
fiber diameter :9/125 m
power lanching in to the fiber=-3.25dbm
-35
1 step groove bends
2 step groove bends
3 step groove bends
-5 0
0
20
40
60
80
10 0
120
-40
w e ig h t i n g m
-45
Graph (d)
0 gm
20
40
60
80
100
120
weight in gm
This is on the expected lines because in
each bending they will be redistribution power in
Graph (e)
core and cladding and the net power passing through
the core decreases. Another important observation is
-5
that for fixed bends( two bends ) as the load on the
out put power(dBm)
-1 0
fiber increases the output decreases. Similar
observations noted in the case of four and six bends,
i.e. as the load on the fiber increases the power
through the fiber decreases, while the number of
-1 5
-2 0
microbenbing
1 step groove bend
type of groove :step groove
2 step groove bend
source of light :1310nm
3 step groove bend
fiber diameter :8/120 m
power lanching in to the fiber=-6.48dBm
-2 5
-3 0
-3 5
-4 0
bends remaining constant( 6 bends, 4bends,2 bends)
0 gm
20
40
60
80
100
weight in gm
fiber length is constant, the load on the fiber
constant, the earlier fiber is replaced with 8/120µm
Graph (f )
fiber coupled to source of light (1310nm or 1550nm)
-3.5
at one end and the power meter at the other end. The
-4.0
-4.5
results are represented graphically shown in graphs
diameter 8/120µm the loss of power is more as
compared to the fiber diameter 9/125µm.
out put power(dBm)
(a) (b) (c) (d). It is observed that, in the case of fiber
-5.0
-5.5
-6.0
microbenbing
type of groove :step groove
source of light :1310nm
fiber diameter :9/125 m
power lanching in to the fiber=-3.35dbm
1 step groove bends
2 step groove bends
3 step groove bends
-6.5
-7.0
-7.5
-8.0
-8.5
-9.0
-9.5
The
experiment
is
further
0 gm
20
40
remains constant except that the V groove is now
replaced with a
60
80
100
120
weight in gm
repeated with all the above mentioned parameters
Graph(g)
rectangular step groove having
either one, two steps, and three steps. Same fiber is
subjected to external load varying 20gm to 100gm,
then the output power is recorded.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
The effect of macro bend loss, again
9/125µm is taken and bend in the form of circle with
-15
an inner radius of 4, 6 and 12 centimeter subjected to
-20
1310nm of power. It is observed that has the circular
out put power(dBm)
-25
-30
-35
microbenbing
type of groove :step groove
source of light :1550nm
fiber diameter :8/120m
power lanching in to the fiber=-5.95dBm
1 step groove bend
2 step groove bend
3 step groove bend
radius of the fiber increases from 4, 6, and 12 cm.
- 2 .0
-40
- 2 .5
m a c ro b e n d in g
fib e r d ia 9 /1 2 5  m ,s o u r c e :1 3 1 0 n m
p o w e r la n c h in g in to th e fib e r: - 3 .3 5 d b m
-45
- 3 .0
0 gm
20
40
60
80
out put power(dbm)
-50
100
weight in gm
Graph (h)
- 3 .5
- 4 .0
4 c m r in g d ia
6 c m r in g d ia
1 2 c m rin g d ia
- 4 .5
- 5 .0
The results are graphically shown in graphs
1
- 2. 0
constant at –-7.75dbm. in spite of the increasing load
- 2. 5
beyond 80gm the comparison can now be made
out put power(dbm)
bends-V
5
6
--
m a c ro b e n d in g
fib e r d ia 9 /1 2 5  m ,s o u rc e :1 5 5 0 n m
p o w e r la n c h in g in to th e fib e r:-3 . 2 5 d b m
- 3. 0
between the two bends-step bending(90 degrees
two
4
Graph (i)
step groove the output power remains almost
and
3
n u m b e r o f rin g s
(e) (f) (g) (h) it is observed that is in the case of two
bending)
2
groove
- 3. 5
- 4. 0
4 c m rin g d ia
6 c m rin g d ia
1 2 c m rin g d ia
- 4. 5
bending(45degrees bending). In case of 90degrees
- 5. 0
bending now the fiber output power saturated at
1
2
3
4
5
6
--
--
n u m b e r o f rin g s
‘-7.75dbm’ while in the case of V groove the power
Graph (j)
saturates at ‘-9.7dbm’ for the same external load and
the same power launched with the fiber diameter
being 9/125µm in both the cases.
-5.0
Similar trend is
-5.5
also observed if the fiber bending is at 90degrees
with three bends with 9/125µm ,8/120µm diameter.
Macro bend losses are observed when a
fiber or a cable bends to the radius of several
centimeters i.e. the bending radius of the fiber is
out put power(dbm)
-6.0
macrobending
fiber dia 8/120 m,source :1310nm
power lanching in to the fiber:-6.48dbm
-6.5
-7.0
4cm ring dia
6cm ring dia
10cm ring dia
-7.5
-8.0
1
2
much large than compared to the core radius of the
fiber. These bends may be introduced during the
installation, during cable pulling along the side of
3
4
5
6
--
number of rings
Graph(k)
the road or a railway track as the bending radius of
the fiber increases, the power loss through the fiber
decreases, therefore it decreases to half a large
bending curvature of the fiber rather than sharp
bending of the fiber.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
micro bending, it is observed that as the number of
-5.0
bends increase the output power also increases i.e.
out put power(dbm)
-5.5
the loss of power increases. It is also observed that
m acrobending
fiber dia 8/120 m ,source :1550nm
pow er lanching in to the fiber:-5.95dbm
the power loss is more in the case of (45degrees
-6.0
bending) V groove bending than in the case of
4cm ring dia
6cm ring dia
10cm ring dia
-6.5
-7.0
1
2
3
4
5
6
--
--
num ber of rings
(90degrees bending)- step groove bending. It is
gently known that the two windows (1310nm and
1550nm) are usually for long haul communications.
1550nm is preferred to 1310nm. This fact is not
taken into account at the stage since the fiber is
Graph (l)
In this case also the circular diameter is increased,
under experimentation is just 8m only. Above fact is
the output power is also increases from 4cm to 6cm
to be demonstrated if we consider fiber length of few
and further 12cm i.e. the power loss is decreased as
hundred kilometers, this part can be taken as a
shown in graphs (i),(j),(k),(l).
extension of the present work.
IV. DISCUSSION OF RESULTS
From the experimentation The load on the
fiber increases the fiber out put power decreases. For
the same length of fiber9/125µm,the out put power
decreases with increasing in wave length. Similar
trend is also observed in the case of 8/120µm fiber.
A comparison can now be paid between 9/125µm
with six V groove bends subjected to 1310nm and
1550 nm. It is observed that in 1550 nm the power
loss is minimum as compared to the 1310 nm as
explained by the theoretical considerations similar
trends are also observed with V groove six bends
and 90degrees (step bending) with one, two and
three bends. In the macro bending, bended ring
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If the ring diameter is fixed, the number of rings
increased the power loss also increased.
V. CONCLUSION
From the experimentation, graphically I
conclude the power loss in the case of micro bending
is large as compared to macro bending. Within the
ISSN: 2231-5381
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
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[8]. N. Lagakos, W. J. Trott, T. R. Hickman, J.
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