1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
497
COMPARATIVE ANALYSIS FOR HIGHER CHANNEL ISOLATION
USING SINGLE FBG FILTER AND TWO FBG FILTER CONNECTED
ONE AFTER ONE FOR HIGH DENSE WDM SYSTEM
Mr. Manish saxena1, Dr.Anubhuti Khare2
, Mr.Amit R.Mahire3
1
Assist. Prof.(EC Dept.) Bansal Institute of Science and Technology, Bhopal
2
Associate Prof. (EC Dept.) UIT RGPV, Bhopal
3
PG student at Bansal Institute of Science and Technology, Bhopal
ABSTRACT
The high dense WDM system is used with bandwidth utilization using high data rates
and low channel spacing. But the in High dense WDM system because of high data rates the
channel interference occurs and due to which crosstalk occurs and the signal get distorts. To
avoid such problems we can use fiber bragg grating filter. The high data rates range is
minimum 2.5 Gbits/s to maximum 40 Gbits/s for channel spacing 200Ghz, 100Ghz, 50 Ghz,
25 GHz for this paper. We used minimum data rate 2.5 Gbits/s and maximum data rates
10.52 Gbits/s for low channel spacing. We carried two simulation using simulation software
optisystem 10.0 for haigh data rates and low channel spacing to get higher channel isolation
in High dense WDM system. To get high channel isolation we use FBG filter which includes
three different apodization profile like uniform apodization profile, Gaussian apodization
profile and Tanh (hyperbolic Tangent) profile. In first simulation we used single FBG filter
including all these three apodization profile and in second simulation we used two FBG filter
including all these three apodization profile in which Gaussian apodization profile is best for
10.52 Gbits/s data rates for 100 Ghz channel spacing.
Keywords: Fiber Bragg Grating, High Dense WDM System, Apodization profiles, Data
Rates, Channel Isolation, Bandwidth.
I. INTRODUCTION
The high data rates and low channel spacing is used in high dens WDM system for
bandwidth saving [1,2].In WDM system channel interference i.e. crosstalk is occurred due to
which singnal get distort. The high data rates and low channel spacing is used for 5The high
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ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
498
data rates and low channel spacing is used for making consistency in amplitude and phase of
the transmitting signal of WDM system [1,2]. Ihe range of high data rates is 2.5 Gbits/s to 40
Gbits/s and low channel spacing range is 200 Ghz,100 Ghz,50Ghz,25Ghz is used for high
dense WDM system [1,2,3]. The data rates used here are 2.5 Gbits/s and 10.52 Gbits/s.We
used fiber bragg grating filter for higher channel isolation.FBG has characteristics to reflect
desired wavelength of signal and transmit other wavelength of signal. In this paper we have
used three different apodization profile in FBG filter for high channel isolation for different
bandwidth -3 db to -20db level. There is higher suppression of side lobes [1,2,3].
II. SYSTEM SIMULATION SETUP
In this paper we have used two different simulation programs where different
apodization and low channel spacing is used for hifher channel isolation.In first simulation
we simulate high dense WDM system. The whole system consists of transmitter,WDM mux
and WDM demux,optical fiber of 40 km length,the single mode fiber has a large core
effective area 80 µm2
, attenuation α = 0.2 dB/km, and dispersion 16 ps/nm/km at the
reference wavelength λ =1550 nm,FBG filter having three different apodization
profile,optical reciver filter has cut off frequency of 0.75x bit rate in hz The transmitter shown in
figure no.1 is WDM transmitter has 8 no.of output ports,frequency of 1550 nm,frequency spacing is 200
Ghz, 100 Ghz, 50 Ghz, 25 Ghz,power is 4 dbm and modulation type for data stream is NRZ.The
receiver has PIN photodetector then visulizers are used like optical spectrum analyzer,Eye diagram
analyzer,BER analyzer.The output of the WDM transmitter is connected to optical fiber having length
40 km thorough which NRZ modulated signal get passed, the data rate for transmitting the signal is 2.5
Gbits/s or 10.52 Gbits/s and it pass through FBG filter,the FBG filter having three different apodization
profiles like uniform apodization ptofile,Gaussian apodization profile,Tanh (hyperbolic tangent)
profile,the output of the FBG filter is fed to the PIN photodetector which convert light signal into
electrical signal,the visulizers are used to check or show the result shown in following figure
no.1.[1,2,6,7]
Figure 1- Simulation scheme with WDM transmitter, NRZ pulse generator with different transmission
speed 2.5 Gbits/s and 10.52 Gbits/s

3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
499
In second simulation we simulates same high dense WDM system with two FBG filter
connected back to back to each other in which first FBG filter has uniform apodization profile and
second FBG has all three apodization profile like uniform apodization profile,Gaussian
apodization profile and Tanh (hyperbolic Tangent) profile.The system transmitter shown in
figure no.2 is having 4 channels with some non linear effects such as self phase modulation,
cross phase modulation, Four wave mixing. The transmitter includes user define data stream
connect to NRZ pulse generator which provides NRZ modulation of data stream and NRZ
modulated data is passed through Mach-Zehnder modulator and continuous wavelength laser
source with 4 dbm power connected to another terminal of external Mach-Zehnder
modulator. The data source produces data with data rate of 2.5 Gbit/s or 10.52 Gbit/s bit
stream, which is to be transfer through multiplexer then optical fiber of 40The single mode
fiber has a large core effective area 80 µm2
, attenuation α = 0.2 dB/km, and dispersion 16
ps/nm/km at the reference wavelength λ =1550 nm and thensignal is passed through
demultiplxer,and output of demultiplxer is fed to two FBG filter which are connected back to
back each other then signal is given to receiver which consists of PIN photodetecor,low pass
Bessel filter and visulizers like optical spectrum analyzer,Eye diagram analyzer,BER
analyzer. In this way we get optical pulse of all four channels. Which are then combine with
power combiner and send via single mode fiber. [1,2,6,7].
Figure 2- Four channel simulation scheme with N RZ pulse generator and different
transmission speed 2.5 Gbit/s and 10.52Gbit
III. RESULTS
In our simulator we have used FBG filter having three different apodization profiles
for channel spacing 200 Ghz, 100 Ghz, 50 Ghz, 25 Ghz for data rates 2.5 Gbits/s and 10.52
Gbits/s.we study comparatively by using single FBG filter having three different apodization profiles for
all four channel spacing and two FBG filter connected back to back to each other in which first FBG
filter has common uniform apodization profile and in second FBG filter has all three apodization
profiles afor all four channel spacing.The FBG filter reflect desired signal and transmit all other.we have

4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
500
used c visualizers like optical spectrum analyzer, Bit Error Rate analyzer for checking the
results.we have got eye diagram,power vs wavelength graph,BER graph in both simulation
for data rates of 2.5 Gbit/s or 10.52 Gbit/s and channel spacing.We compared the results of
channel spacing of 200 Ghz and 100 Ghz for data rates 2.5 Gbits and 10.52 Gbits/s by using
single FBG filter and two FBG filters connected back to back to each other.In case of first
simulation for 2.5 Gbits/s the speed performance is better for uniform apodization
profile,tanh apodization profile than Gaussian apodization profile because bit error rate are
zero and higher quality factor for 200 Ghz and 100 Ghz channel spacing but the data rate of
transmitting of data is very low it is 2.5 Gbits/s and BER is less for both channel spacing i.e
200 Ghz and 100 Ghz.From simulation results of of 10.52 Gbits /s data rates we observed that
the speed performance is better in uniform apodization profile because of lower BER values
than other two apodization profile i.e. Gaussian apodization profile and Tanh ( hyperbolic
tangent) apodization profile.But in uniform apodization profile the bit error rate values are
less for 200 Ghz channel spacing than 100 Ghz channel spacing which shows that there is no
higher channel isolation in uniform apodization profile due to 200 Ghz which is higher
frequency channel spacing than 100 Ghz it is same for Tanh (hyperbolic tangent) apodization
profile i.e BER values are less in 200 Ghz channel spacing than 100 Ghz channel spacing and
for Gaussian apodization profile the BER values are less in 100 Ghz channel spacing than
200 Ghz which is shown in table no.1 and figure no.3 channel but Gaussian apodization
profiles BER values are higher in first simulation when single FBG filter is used and
Gaussian apodization profile BER values are less in second simulation when two FBG filters
are connected back to back each other [1].
Table-1-Bit Error Rate for 10.52 Gbits/s of channel spacing 100 GHZ & 200 GHZ
Figure 3- Bit Error Rate for 10.52 Gbits/s for 100 GHZ and 200Ghz channel spacing for
Uniform apodization
Channel
Spacing
Uniform Gaussian Tanh
100 GHZ 3.40822e-010 7.90849e-005 4.49800e-010
200 GHZ 3.10658e-10 8.10317e-005 4.11891e-010

5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
501
Figure 4- 10.52 Gbit/s data rate WDM system with optical spectrum of second channel at
100 GHZ channel spacing FBG filter with Gaussian apodization profile and the second
channel eye diagram BER = 7.90849e-005
The second simulation method is best than first simulation method because in second
simulation method we used two FBG filter connected back to back each other. In which BER
values are less for uniform apodization profile in first FBG filter as well as second FBG filter
than other two apodization profile i.e.uniform apodization profile in first and Gaussian and
Tanh (hyperbolic tangent) profile in second FBG filter for 2.5 Gbits/s.But the data rate is low
i.e 2.5 Gbits and eye diagram is not open properly.10.52 Gbits/s data rate has better results
than 2.5 Gbits/s which is shown in table no.2,table no.3 and figure no.5& figure no.6.[1,2].
Table-2-Bit Error Rate for 2.5 Gbits/s of channel spacing 100 GHZ & 200 GHZ
Table-3-Bit Error Rate for 10.52 Gbits/s of channel spacing 100 GHZ & 200 GHZ
Channel
Spacing
Uniform Gaussian Tanh
100 GHZ 0.00454676 0.00479342 0.00455023
200 GHZ 0.00460255 0.00496808 0.00460729
Channel
Spacing
Uniform Gaussian Tanh
100 GHZ 2.0395e-005 1.75349e-005 2.03193e-005
200 GHZ 2.19816e-005 2.0468e-005 2.19594e-005

6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
502
Figure 5-10.52 Gbit/s data rate WDM system with optical spectrum of second channel at
100 GHZ channel spacing FBG filter with Uniform apodization profile and the second
channel eye diagram BER = 2.0395e-005
Figure 6-10.52 Gbit/s data rate WDM system with optical spectrum of second channel at
100 GHZ channel spacing FBG filter with Gaussian apodization profile and the second
channel eye diagram BER = 1.75349e-005
We can observed from table no.2 &3 of second simulation in which two FBG filter
connected back to back to each other, the bit error rate values of Gaussian apodization profile
are less for 10.52 Gbits data rate of 100 Ghz channel spacing than bit error rate values of
Uniform apodization profile for 2.5 Gbits/s data rate of 100 Ghz channel spacing and BER
values of second simulation for 10.52 Gbits/s of 100 Ghz channel spacing are also less than
BER values of first simulation in which single FBG filter is used of 10.52 Gbits/s for 100
Ghz and 200 Ghz channel spacing.Figure 5 & figure 6 shows results for power vs wavelength
graph and eye diagram of 10.52 Gbits/s for Uniform apodization profile and Gaussian
apodization profile for 100 Ghz channel spacing respectively.From which we can observed
that there is higher channel isolation for Gaussain apodization profile with bit rate values
1.75349e-005 as compared to uniform apodization profile with bit error rates values
2.0395e-005.The Gaussian apodization profile of second simulation where two filter
connected back to back to each other has higher channel isolation with BER values 1.75349e-
005 as compared to uniform apodization profile and Gaussian apodization profile with BER
values 3.40822e-010,7.90849e-005 respectively for 100 Ghz channel spacing of first
simulation where single FBG filter is used.[1,2].

7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
503
IV. CONCLUSION
We can conclude from simulation results of both simulation method ,the simulation
mehod 2 is best than simulation method 1.The simulation method second has two FBG filter
which are connected back to back to each other and in first FBG has common uniform
apodization profile and in second FBG filter all three apodization profile like uniform
apodization profile,Gaussian apodization profile and Tanh (hyperbolic Tangent) profile are
used one after for channel spacing 200 Ghz, 100 Ghz, 50 Ghz, 25 Ghz for 2.5 Gbis/s and 10.52
Gbits/s data rates and in first simulation method we used WDM transmitter and single FBG filter which
includes all three apodization profile like apodization profile,Gaussian apodization profile and
Tanh (hyperbolic Tangent) profile are used one after for channel spacing 200 Ghz, 100 Ghz, 50
Ghz, 25 Ghz for 2.5 Gbis/s and 10.52 Gbits/s data rates.We got high channel isolation in second
simulation method for Gaussian apodization profile because of lower bit error rate values and higher
side lobe reduction because of using two FBG filter connected back to back to each other for 10.52
Gbits/s data rate of 100 Ghz channel spacing as compared to Uniform apodization profile & Gaussian
apodization profile with higher bit error rates values of first simulation method for 10.52 Gbits/s data
rate of 100 Ghz channel spacing.
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