Different Method of Channels Allocation to Linearity in ...

Different Method of Channels Allocation to Linearity in WDM system Veerpal Kaur

Kamaljit Singh Bhatia

Amrit Kaur

Harsimart Kaur

Deptof ECE Punjabi University Patiala Patiala, Punjab Jalandhar,[email protected]

Dept. of ECE S.G.G.S.W.U, Fatehgarh Sahib Punjab [email protected]

Dept of ECE Punjabi university Patiala Patiala, Punjab [email protected]

Dept of ECE CTIEMT, Jalandhar [email protected]

Abstract-In long-haul WDM communication system, transmission characteristics are degraded by four wave mixing. In this paper we analysis the FWM power equal channel spacing ,unequal spacing and equal spacing with polarisation at different value of chromatics dispersion in wave length division multiplexed system. We obverse that unequal spacing have lower FWM power as compared equal spacing and equal spacing with polarisation. Similarly at maximum value of dispersion having minimum value of FWM power. Keyword-Four wave mixing,Wavelength-Division Multiplexing, BER, Dispersion.

I. INTRODUCTION The latest trend in light wave communication system is towards huge information transmission capacity by explosive growth in data rate communication by using wave length division multiplexing. [1-2] The performance of DWDM limited by dispersion and non linearity, When signal power is high. Non-linearity is two type one is stimulated scattering response for loss and gain due to stimulated process, other non linearity are knowkerr effect due to change in refractive with change in input power, and linear response of optical system is lost.[1].It is mainly three type self phase modulation(SPM),cross phase nodulation(CPM) and four wave mixing(FWM). Non linearFWM process in which three frequencies fi,fj,fk (k ≠ i,j)interact through third order nonlinearity of optical fiber to generate new frequency[1]



 "

(1)

These new frequency components falls on the same transmission window and original signal get degraded and effect the system performance. Thus three wave give rise nine new frequency component. The number of side bands use to FWM increase is given as [2].



.

(2)

Where N is number of channels and M number of newly generated side bands. Performance of WDM system degraded by low chromatic dispersion and non-linear effect of fiber link. [2-3] The cause of FWM analyzed in and different methods for mitigating the impact of fiber

nonlinearities on WDM/DWDM systems including], dispersion management schemes[14]and the use of nonzero dispersion fibers [19]. Different channel allocation techniques like equal-channel spacing and unequal-channel spacing techniques [17-20], Reduction of FWM investigated in [6] optical phase conjugator as wave front reversal, which is used to suppress the FWM in OFDM system. [6] OPC support all the data type format, OPC simultaneously used to cancel the fiber loss, dispersion loss, Kerr effect in long communication. We have already achieved good results within Monitoring and Compensation of Optical Telecommunication MIMO-OFDM system with OADM [11-17]. In this paper, section II presents theoretical analysis of FWM performance degradation in intensity–modulated direct detection (IM-DD) WDM system with equal channel spacing and with varying chromatic dispersion, section III describe the experiment simulation setup for analyse the effect of equal unequal and polarisation with equal spacing, result and discussion summarized in section IV and conclusion presented in section V. II. FUNDAMENTAL OF ANALYSIS FWM is one of major limiting factor in WDM optical communication system due low dispersion, equal channel spacing .As a result, Estimating power of FWM is very important for design and evaluation of WDM system. A well know formula used to estimate the Power of FWM derived by Hill et al[3] and later reformulated by efficiency depends upon phase mismatch factor by Shibata et al.[4].This new formula used for estimating FWM crosstalk is recently used in WDM system.[3].Power of FWM can be written as



"









(3)

Where PiPjPk are signal input power at frequency fi ,fj,fk,(k ≠ i,j) respectively, L is the length of fiber, α is the fiber attenuation coefficient the degeneracy factor D takes value equal to three or six for degenerate and non degenerate FWM, respectively. The nonlinear coefficient is given [1] by

ñ

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Where Aeff effect area of fiber ,λ vacuum wave length andn2 non linear is refractive index. Also η is the FWM efficiency which can be expressed as[4] η  α

α

"





α



" ó   α 

TABLE I. SIMULATION PARAMETER AND THEIR VALUES

 





Values

Pump frequency (THz)

193.025to193.095

Probe frequency(THz)

193.060

Channel spacing (THz)

0.010

Pump power(dBm)

-10

Reference bit rate(Gbit/s)

10

Attenuation (dB/km)

.2

Fiber length(km)

200

Amplifier gain (dB)

20

Preamplifier gain (dB)

35

(5)

In this expression ∆ k is phase match factor which depends upon dispersion of fiber and channel spacing and written as [4]

 

Parameters



 

(6)

Where   channel spacing, Dc chromatic dispersion, dDc/dλ dispersion slope, and λ k is the wavelength at frequency f k. Where ∆ k mismatch factor not a function of signal powers, so it call linear phase matching factor. FWM efficiency depends on the fiber dispersion, the channel separation, and the fiber length, but not on the transmitted power [4].So as above expression dispersion increase phase match factor increase and efficiency decreases. Power of FWM directly proportional to the efficiency so power of FWM decrease by increasing dispersion.[10]So similarly power of FWM reduces directly by increasing channel spacing. III. SIMULATION SETUP AND DESCRIPTION Work is carried out using simulation to observe the effect of FWM in WDM system to evaluate the impact of varying channel spacing between the input channels of a DWDM system in the presence of four wave mixing is shown in Fig. It consisting of eight CW lasers externally modulated by 10 Gbps NRZ data for each channel with equal channel spacing and unequal channel spacing varying in the range of 0.01 THz to 0.015THz launched into 200 km having two spans of 100 km of 0.2 dB/km attenuation factor and core effect area is    .The changes in transmitter side to discuss the various FWM suppression methods under channel allocation are given below (a)Equal channel spacing-In the case of equal channel spacing the central frequencies of CW laser are taken as 193.025, 193.035, 193.045, 193.055, 193.065,193.075, 193.085 and 193.095 THz having channel spacing of 0.01 THz. (b) Polarization -In the case of polarization method the polarization for alternate Channel is rotated 180 around the s2 axis of pioncare sphere. (c) Unequal-channel spacing-In the case of unequal-channel spacing the central frequenciesof laser source are taken as 193.025, 193.04, 193.045, 193.055, 193.07,193.08, 193.085 and 193.095 THz. Simulation parameters used were as followed in Table1 to obverse the effect of FWM at centre of channel.

The dispersion is completely compensated by using ideal fiber Bragg grating at each end of fiber span and loss are compensation by fixed amplifier. In order to observe the impact of suppression method the fiber dispersion value is varied from 0 to 16 ps/nm/km during simulation. At receiver end the optical power meter is used to measure of FWM component. Optical transmitter

Optical

PreAmplifier

Combiner (1-8) channel

Power

Fiber &grating

Optical

Meter

Splitter Fig.1.Simulation setup

&lifier

IV. RESULT AND DISCUSSION After simulation, it obverse that FWM signal degrade the system performance, analyse in term of FWM signal power, input output spectrum and eye opening. We make to analyse the performance of WDM system based upon different way to allocated the channel at input side and dispersion of fiber we make comparison between equally spaced, equally spaced with orthogonal polarization and repeated unequal channel spacing at varies value of dispersion shown in fig.2



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Fig.2. FWM power verses dispersion

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We observe that unequal spacing having lower FWM power as compared to other equal spacing and orthogonal polarisation at equal TABLE II. FWM POWER AT RESPECTIVE CHANNEL ALLOCATION Channel allocation

FWM power(dBm) Lower limit(dBm)

Upper limit(dBm)

Equal

3.989

4.175

Equal spacing

3.900

4.050

3.886

3.949

(With polarisation) Unequal spacing

Similarly we obverse that as dispersion increase from (0 to 16) power of FWM reduces as due to phase match factor increase,decreasing efficiency which directly reduces FWMPower. As follow the equations in section II. We make analysis output spectrum as shown in fig.3

Fig.3. (c) Output spetrum (D=8)

(d) Output Spectrum (D=10)

(a) Output Spectrum (D=4)

Fig.3. output spectrum at different value of dispersion.

Above all output spectrum examine that new peaks appeared in spectrum decrease as dispersion increased at equal spacing. V. CONCLUSIONS

(b) Output spetrum (D=6)

The proposed methods for FWM suppression like equal channel spacing, equal channel spacing with orthogonal polarization and unequal-channel spacing has been found best to the existing methods like dispersion management, using non-zero dispersion fiber. Moreover the existing above FWM suppression method like unequal-channel spacing requires a complex system design and the proposed methods are superior to commonly used methods when the dispersion is fully compensated. Similar increase the dispersion of fiber power of FWM signal is decrease, new peaks appeared in output spectrum decreased. REFERENCES [1]

G. P. Agrawal, Fiber-Optic Ed.Wiley, New York, 2002.

[2]

G.P.Agrawal, Nonlinear fiber optics,3 rd Ed,Academic press, an Diego,CA,2001.

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system,

3rd

[3]

R.W. Tkach, A.R. Chraplyvy,F.Forghieri,A.H.Gnack and R.M.Derosier, “Four-photon mixing and high speed WDM system,” J. Lightwave Technol.,vol13,pp.841-8849,May 1995.

[4]

K.O.Hill, D.C.Joshon, B.S.Kawasakiand R.I. MacDonald, “CW three-wave mixing in single mode fiber,”J. Appl. Phys.,vol.49, pp. 5098-5106, Oct. 1978.

[5]

N. Shibata, R. P. Braun, and R. G. Waarts, “Phase-mismatch dependence of efficiency of wave generation through four-wave mixing in a single mode optical fiber,” IEEE J. Quantum Electron.vol. 7, pp. 1205-1210,July 1987.

[6]

Xuefeng Tang andZongyan Wu, “Reduction of Intra channel non linearity using OPC,” Journal of Photonics Technology, volume17, no.9, September 2005.

[7]

Vladimir pechenkin,jvanj.fair, “On FWM suppression in DMOFDM system with an optical phase conjugation (OPC) module,” J. Light wave Tech., Vol. 29, No.11, june1, 2011.

[8]

Mr. T. Sabapathi, A. Selvamani, “Suppression of FWM by OPC conjugation in DWDM fiber link,” International journal on recent advancements in electrical, electronics and control engineering, 2011.

[9]

Sugumaran, Arulmozhivarman, “Effect of chromatic dispersion on FWM in WDM system and it suppression,” Journal of international conference and workshop on emerging Trend in technology 2011

induced distortion in nonzero dispersion fiber WDM systems. ” J. Lightwave Technol. 23 (March) (2005). [20] Vishal Sharma, RamandeepKaur, “Implementation of DWDM system in the presence of four wave mixing (FWM) under the mpact of channel spacing.”Optik 124 (2013), 3112-3114..IET Optoelectronic, ElsevierScience.

[10] B.K Mishra, Loch, An. Jolly , KarishmaMhatre, “Analysis of four wave mixing effect in WDM communication system for different channel spacing,” International journal of computer application., Dec.2013. [11] Kamaljit Singh Bhatia, R.S. Kaler, T.S. Kamal and Rajneesh Kaler, “Monitoring and Compensation of Optical Telecommunication Channels by using Optical Add Drop Multiplexers for Optical OFDM System”, 2012 De Gruyter. [12] E.K. Singh Bhatia, T.S. Kamal, R.S. Kaler, “Peak-to-average power ratio reduction using coded signal in optical-orthogonal frequency division multiplexing systems”, IET Optoelectronic., Elsevier Science. (2012), Vol. 6, Iss. 5, pp. 250–254 [13] Kamaljit Singh Bhatia, R.S. Kaler, T.S. Kamal, “Design and simulation of optical-OFDM systems”, Journal of Russian Laser Research, Springer Science+Business Media (2012), Volume 33, Number 5, pp. 202–208, September, 2012, [14] K.S. Bhatia, T.S. Kamal, R.S. Kaler, “An adaptive compensation scheme-based coded direct detection optical–orthogonal frequency division multiplex (OFDM) system” Computers and Electrical Engineering 38, Elsevier Science (2012) 1573–1578, [15] Kamaljit Singh Bhatia, R.S. Kaler, T.S. Kamal, RajneeshRandhawa, “Simulative analysis of integrated DWDM and MIMO-OFDM system with OADM” Optik 124, Elsevier Science (2013) 117–121 [16] Kamaljit Singh Bhatia, T.S. Kamal, “Modeling and simulative performance analysis of OADM for hybrid multiplexed OpticalOFDM system” In Press Optik, Elsevie Science (2013), [17] Amarpal Singh, Ajay K. Sharma, T.S. Kamal, “ Investigation on ModifiedFWMsuppression methods in DWDM optical communication system, Opt. ” Commun.282 (February) (2008) 392–395. [18] Rajneesh Kaler, R.S. Kaler, “Investigation of four wave mixing effect at differentchannel spacing. ” In press Optik,123Elsevier Science (2012), 352–356. [19] Neokosmidis, T. Kamalakis, A. Chipouras, T. Sphicopoulos, “ New techniques for the suppression of the four-wave mixing

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