Upload
others
View
8
Download
0
Embed Size (px)
Citation preview
International Journal of Research in Engineering, Technology and Science, Volume VII,
Special Issue, Feb 2017
www.ijrets.com, [email protected], ISSN 2454-1915
Tushar Kant Panda, Krishna Chandra Patra, Nalinikant Barapanda and Padmini Mishra 1
PERFORMANCE COMPARISON OF DISPERSION COMPENSATING
FIBER IN 40 GBPS WDM NETWORK USING PRE, POST AND
SYMMETRICAL COMPENSATION SCHEMES Mr.TusharKantPanda1 , Dr. Krishna Chandra Patra2,Dr.Nalinikant Barapanda3 and Mrs.
Padmini Mishra4
1Research scholar, Sambalpur University Institute of Information Technology, Sambalpur 2Asst. Professor, Sambalpur University Institute of Information Technology, Sambalpur
2Reader, Sambalpur University, Sambalpur 3Asst. Professor, Gandhi Institute of Engineering and Technology, Gunupur
Abstract-Fiber optics communication has become a widespread adopted method for data transmission. The miraculous idea of using light as carrier to carry the message across the distance allured a lot of researchers towards itself. The major advantage offered by the fiber optic communication is its high bandwidth. In order to make the optimum use of this bandwidth we must transmit many signals through single fiber. WDM Network permits multiple channels to be routed through single fiber at different wavelength. However it does face some challenges and Dispersion being the major limiting factor among all. Dispersion causes pulse distortion and spreading of pulses in time domain. In this paper, we have used the very basic technique of using dispersion compensating fibers (DCF) to compensate the positive dispersion in a WDM network. Three schemes of dispersion compensation (pre, post and symmetrical) with DCF are proposed in this paper by using Optisystem 7.0 simulator. The results obtained from the respective schemes are compared in terms of Q-factor, BER, Eye height and Threshold value and it is found that the symmetrical compensation method is superior to pre- and post-compensation methods. Thus by using these comparisons one can achieve a cost effective, propitious system with high spectral efficiency and good flexibility. Keywords –Dispersion compensating Fiber, Bit error rate (BER), Q-factor, Eye height, MZM (Mach Zender Modulator), Optisystem Software version 7.0. 1. INTRODUCTION
From past few years, the number of internet users is
increasing day by day, hence, the internet business is
increasing too. Therefore, primary requirement of
people are more capacity and better network system
[1]. In order to get better and effective performance
while transmitting the data from transmitter side to
receiver side, WDM network is being used [2]. The key
parameters which is responsible for effective
performance in Wavelength Division Multiplexing
(WDM) optical network is high data rate, high capacity
and high bandwidth. Different signals are being used
as input signal at transmitter side and are multiplexed
using WDM network [3]. After multiplexing, signals
are sent through a single fiber. While transmissionof
signal, there is degradation in light intensity while
travelling through fiber. Though WDM network is one
of the effective techniques for data transmission, still it
suffers from performance limiting factors like
dispersion and nonlinear effects. Here dispersion is the
main performance limiting factor which responsible for
limiting the information capacity at high data rate [4].
In order to compensate dispersion, different dispersion
compensation techniques are being used. Dispersion
compensating fiber, fiber Bragg grating, electrical
compensation method and optical phase conjugation
are the effective dispersion compensation techniques
which limit the performance limiting factor
(dispersion).
2. DISPERSION
The main performance limiting factor in the world
of optical communication is dispersion [5]. When
light pulses of different wavelength are
transmitted through optical fiber, due to the
variation in refractive index with wavelength,
pulses travels with different speed. After travelling
PERFORMANCE COMPARISON OF DISPERSION COMPENSATING FIBER IN 40 GBPS WDM
NETWORK USING PRE, POST AND SYMMETRICAL COMPENSATION SCHEMES
TusharKantPanda, Krishna Chandra Patra, Nalinikant Barapanda and Padmini Mishra 2
certain distance, these pulses spreads and
broadening of pulses are observed. These pulse
broadening in optical fiber is referred as
dispersion. Dispersion is also responsible for
inter symbol interference (ISI) [6]. In ISI, the
pulses goes on broadening and hence overlap
each other. Due to this overlapping, the
pulses can’t be distinguished at receiver end.
Dispersion can be classified into following
categories.
Fig 1: CLASSIFICATION OF DISPERSION
Material Dispersion: This type of dispersion arises
due to the variation in refractive index of material
used during transmission of data from transmitter
side to receiver side. Because of the change in
refractive index in the material of the fiber, the
rays travels with different speed and also get
refracted differently and hence dispersion arises.
Waveguide Dispersion: This type of dispersion
arises due to the refractive index profile of core
and cladding of optical fiber used. Since core
refractive index is different as compared to
cladding refractive index, the ray of light will travel
with different speed which results to cause
dispersion.
Modal Dispersion: This type of dispersion arises
because of the use of multimode fiber in optical
communication. When a beam of light travels
through multimode fiber then at the receiver end,
the rays which comprises the beam of light reaches
at different time. This results in pulse broadening
and hence, dispersion is observed.
Polarization Mode Dispersion: This type of
dispersion arises because the light pulses of
different polarization state travels with different
group velocities which results in pulse width
spreading and hence, dispersion is observed.
As dispersion increases, ISI also increases due to
which there is reduction in effective bandwidth
which leads to an incresing BER. So to eliminate
dispersion, different dispersion compensation
techniques are used. Some of the dispersion
compensation techniques which are commonly
used are dispersion compensating fiber, Fiber
Bragg grating, electrical compensation method
and optical phase conjugation [7]. Among these
compensation technique, dispersion compensating
fiber is the most suited one.
3. DISPERSION COMPENSATING FIBER
In order to tackle the performance limiting factor
(dispersion) in optical communication and
maximizing the overall system performance,
dispersion compensating fiber commonly known as
DCF is used.
DCF was introduced to the world in the year 1980.
The idea of DCF became viral and started to spread
with a higher rate, in this way DCF gained the
attention and became a field to study about. Due
to the higher stability of DCF and resistance to
temperature, it is being used to compensate
dispersion and has been studied in large scale all
over the world.
The range of dispersion in DCF ranges from -70 to -
90 ps/nm km [8]. Due to the negative value of
dispersion, DCF can be used to compensate
dispersion efficiently. WDM system is mostly
affected by dispersion and nonlinearity. The system
performance depends upon the following:
(a) Power at the input of different fiber.
(b) Position of DCF.
(c) The Value of dispersion used.
When the DCF is placed before or after the SMF
then the average dispersion values comes down to
zero [9].
D= Dispersion of fiber
L= Length of fiber
According to the positioning of DCF, dispersion
compensation can be done in following three
ways:
Pre-Compensation: In this type of
compensation method, DCF is placed just
before SMF in order to compensate
dispersion.
Post-Compensation: In this type of
compensation method, DCF is placed just
after the SMF to compensate dispersion.
Symmetric-compensation: In this type of
compensation method, two DCF are used.
One is placed just before and another just
after optical fiber [10].
4. SIMULATION SETUP:
International Journal of Research in Engineering, Technology and Science, Volume VII,
Special Issue, Feb 2017
www.ijrets.com, [email protected], ISSN 2454-1915
Tushar Kant Panda, Krishna Chandra Patra, Nalinikant Barapanda and Padmini Mishra 3
A SMF is standardized by using a dispersion
compensating scheme In a Wavelength Division
Multiplexing (WDM) network in order to achieve
high data rate and high capacity .There exists some
of the most effective compensating schemes such
as FBG, DCF, electrical dispersion compensation
and optical phase conjugation method etc. In this
experimental setup, simulation is carried out by
using WDM technique in which the data rate used
is 4×10=40Gbps . Here DCF is used to compensate
dispersion. There exist three compensation
schemes if DCF technique is considered. The
schemes are Pre-Compensation, Post-
Compensation and Symmetric-Compensation.
Symmetric compensation technique which is also
known as mix compensation technique is
considered to be the best among all three and in
our experiment we got the results which prove the
same.
FIG (2) is a block diagram representation of our
experimental setup of optical communication
network using WDM for multiple transmission and
DCF to compensate the dispersion caused in SMF
during transmission. The setup comprises of
transmitter, fibers and receiver. In the transmitter
side we have Pseudo random bit generator which
generates random sequences of pulse which is
given to NRZ pulse generator for line coding, CW
Laser is used to convert the electrical signal into
optical signal that is fed to an optical modulator
i.e. Mach Zehnder Modulator. The transmitted
signal is then sent to WDM network which
multiplexes these signals. Once the signal is
multiplexed it is sent through SMF. EDFA present
after the SMF amplifies the signal that it receives
from SMF and thus helps to overcome attenuation.
The amplified signal is then passed to DCF where
the compensation of dispersion takes place. Once
the dispersion has been compensated, the
compensated signal is again amplified by using
another EDFA having different optical
amplification gain as compared to the EDFA used
before. After the amplification of the signal, the
amplified signal is sent to WDM DEMUX where de-
multiplexing takes place. It converts the serial data
in parallel data. As soon as the signal is de-
multiplexed, the receiver that consist of
photodetector decodes the information and
converts the signal back to its electrical form and
the filter used at end filters any noises that may
have been left and at last we receive the signal
without any kind of loss.
Fig 2: POST COMPENSATION SCHEME
Fig3.1: OPTISYSTEM 7.0 SIMULATION SETUP(POST)
PERFORMANCE COMPARISON OF DISPERSION COMPENSATING FIBER IN 40 GBPS WDM
NETWORK USING PRE, POST AND SYMMETRICAL COMPENSATION SCHEMES
TusharKantPanda, Krishna Chandra Patra, Nalinikant Barapanda and Padmini Mishra 4
Fig3.2: OPTISYSTEM 7.0 SIMULATION SETUP(MIX)
Fig3.3: OPTISYSTEM 7.0 SIMULATION SETUP(PRE)
Simulation parameters used in this piece of work to get
an effective result is given in the Table no.1.
TABLE NO 1. : Simulation parameters
Parameters Values
LENGTH of SMF 150Km(pre,post), 80km(symmetric)
REFERENCE WAVELENGTH in SMF
1550 nm
ATTENUATION in SMF 0.2dB/Km
DISPERSION coefficient in SMF
17 ps/nm/Km
DISPERSION SLOPE in SMF 0.08 ps/nm^2/Km
DIFFERENTIATION GROUP DELAY in SMF
3 ps/Km
Dispersion coefficient in DCF -85ps/nm/Km(pre, post), -68ps/nm/Km (symmetric)
Length of DCF 30Km(pre, post) , 20km(symmetric)
Gain of EDFA 20 dB
Gain of EDFA 4 dB
In this simulation, transmitter consist of 4 pseudo random bit
sequence generator each operating at a bit rate of 10
GBits/s. Pseudo random bit sequence generator generates a
random code consisting of 0’s and 1’s. This sequence of 0’s
and 1’s are then converted into electrical pulses which are
fed in the Mach Zehnder Modulator. There exist 4 pairs of
CW Laser and Mach Zehnder Modulator. The work of Mach
Zehnder modulator is to modulate the signal from the CW
Laser. The frequency range of CW Laser
used is 193.1THz to 193.4THz. The band width of WDM MUX
used at the transmitter side is 80 GHz. The SMF used for the
transmission of data is 150 Km long for pre and post
compensation and 160 km long for symmetrical
compensation and the reference wavelength at which it
operate is considered to be 1550 nm with 0.2 dB/km of
attenuation. Dispersion value taken for SMF is 17 ps/nm/Km
and its dispersion slope is taken to be 0.08 ps/nm2/Km. The
value Differential group delay of SMF is 3ps/Km. The EDFA
used just prior to the DCF is having an optical amplifier gain
of 20 dB and the one used just after the DCF is having an
optical amplifier gain of 4dB. DCF used to compensate
dispersion is 30 Km long for pre and post compensation and
20 km long for symmetrical compensation. The dispersion
value of DCF used to compensate dispersion is taken to be -
85 ps/nm/Km. at receiver side there is a WDM DEMUX
whose channel band width is same as the channel band
width of WDM MUX used in the transmitter side. PIN
Photodiode is used here to retrieve the optical signal and
convert it into electrical signal. The electrical signal is passed
through low pass filter. LPF filters the high frequency noises
and transfer the filtered signal to BER analyzer to determine
the parameters like eye height, BER and Q-Factor.
5. RESULT:
5.1 Post compensation method:
Fig1: First channelFig2: Second channel
Fig3: Third channel Fig4: Fourth channel
5.2 Pre compensation method:
Fig1: First channelFig2: Second channel
International Journal of Research in Engineering, Technology and Science, Volume VII,
Special Issue, Feb 2017
www.ijrets.com, [email protected], ISSN 2454-1915
Tushar Kant Panda, Krishna Chandra Patra, Nalinikant Barapanda and Padmini Mishra 5
Fig3: Third channelFig4: Fourth channel
5.3 Symmetric compensation method:
Fig1: First channelFig2:Second channel
Fig3: Third channel Fig4: Fourth channel
Table 2.3: Comparison of three dispersion compensation schemes:
Pre-compensati
on
Post-compensati
on
Symmetrical-
compensation
Average Q-factor
(dB) 11.521925 9.0804325 7.959815
Average BER
10488831572e-026
1.837630753e-016
9.49928761e-014
Average Eye
2.913e-005 2.723995e-
005 0.00550149
height
Average Threshold value
1.7346e-005 1.563695e-
005 0.005724132
5
6. CONCLUSION
For any system to work effectively it must have the
Q factor that determines the quality of service of that system
about 7dB and the next factor which is very crucial for the
system is it’s eye height value, the wider the eye opening the
better the system gets.
Comparing above obtained results we can very
well observe that symmetric compensation has the best eye
height and it also has satisfactory value for the Q factor and
hence it is the best technique compared to post and pre.
7. REFERECES:
[1] Mochida Y, Yamaguchi N, Ishikawa G, "Technology-
oriented review and vision of 40Gb/s-based optical transport
Networks", Journal of light-wave technology.PP. 2272-228,
12002, 20(12).
[2] Dispersion compensation in 40 gb/s wdm network using dispersion compensating fiber 1 mr. Gaurang.h.patel, 2prof. Rohit.b. Patel, 3 prof. Sweta.j.patel, journal of information, knowledge and research in electronics and communication engineering, issn: 0975 – 6779| nov 12 to oct 13 | volume – 02, issue - 02
[3] WDM-OTDM based spectral efficient hybridmultiplexing technique inherent with properties of bandwidth elasticity and scalability Gousiaa, G.M.Rathera, AjayK.Sharmab.ELSEVIERwww.elsevier.de/ijleo ,Received 5 August 2008; accepted 16 December 2008
[4] Zou X Y, Hayee M I, H wang S M, et al. Limitations in 10Gb/s WDM optical-fiber transmission when using a variety of fiber types to manage dispersion and nonlinearities[J]. Light wave Technol., PP: 1144-1152,June,1996
[5] WuQiang,Yu Chong Xiu, "Analysis on dispersion compensation with DCF", semiconductor optoelectronics,Vol.24 No.3 pp.186-196.June 2003
[6] Bo-Ning HU, Wang Jing, Wang Wei, Rui-Mei Zhao, Analysis on Dispersion Compensation with DCF based on Optisystem, 2ndInternational Conference on Industrial and Information Systems 2010, 40-43
[7] Jianjun Yu, Bojun Yang,"Dispersion-allacated soliton technology with long amplifier spacing and long distance," IEEEphotontechnollett, vol 9, pp. 952-954,No.7, 1997:
PERFORMANCE COMPARISON OF DISPERSION COMPENSATING FIBER IN 40 GBPS WDM
NETWORK USING PRE, POST AND SYMMETRICAL COMPENSATION SCHEMES
TusharKantPanda, Krishna Chandra Patra, Nalinikant Barapanda and Padmini Mishra 6
[8] Bo-ningHU, Wang Jing, Wang Wei and Rui-mei Zhao1, “Analysis on Dispersion Compensation with DCF based on Optisystem”, IEEE 2nd International Conference on Industrial and Information Systems, 2010
[9] ZhouZhiQiang, TangYuLiang, "Optimmum schemes of dispersion compensation transmission systems using
dispersion compensation fibers",laser technology, VoI.24,No.5,pp.265-269 Oct.2000.
[10] R.S.Kaler, Ajay K Sharma, and T.S.Kamal, Comparison of pre-,post- and symmetrical- dispersion compensation schemes for 10Gb/s NRZ links using standard and dispersion compensated fibers, Elsevier Optics Communication 209 2002, 107-123