Ultra Wide Wavelength Division Multiplexing Optical Code Division Multiple Access Communication Systems in Wide Area Optical Communication Networks

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1 Ultra Wide Wavelength Division Multiplexing Optical Code Division Multiple Access Communication Systems in Wide Area Optical Communication Networks Ahmed Nabih Zaki Rashed Electronics and Electrical Communications Engineering Department Faculty of Electronic Engineering, Menouf 3951, Menoufia University, EGYPT Abstract The effect of dispersion of fiber on the performance of OCDMA system and to find the limitations imposed by dispersion on number of user and length of transmission. t has been observed that in the bit error rate performance curve the error is decreased when the number of subscriber is increased side by side the optical power is reduced when the users is added. This paper has presented the ultra wide wavelength division multiplexing optical code division multiple access (OCDMA) communication systems in wide area optical communication networks and the transmission efficiency to be evaluated in order to determine the impact of multi access interference. Key Words Signal to noise ratio; BER; UW-WDM; Optical orthogonal codes; Ultra multi users. 1 ntroduction Earlier optical fibers have been used for point to point communication at a very high speed [1-3]. Often the optical fiber offers much higher speed than the speed of electronic signal processing at both ends of the fiber. So to be able to take the full advantage of the speed in optical fibers one of the basics concepts in fiber optic communication is the idea of allowing several users to transmit data simultaneously over the communication channel. This is called multiple access. There are several techniques to provide multiple access and one of them is fiber optic-code division multiple access (FO-CDMA). n FOCDMA each user is assigned one or more binary signature sequence, so called code words. The data to be send is mapped onto the code words and the different users code words are mixed together and send over the channel. At the receiver end a decoder, which is individual for each user [4], compares the incoming sequence with stored copies of the code words to be able to extract the information bits. Fiber optics is a particularly popular technology for local area networks. n addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. n the future, almost all communications will employ fiber optics. Multi- access techniques are required to meet the demand for high speed, large capacity communications in optical networks [5-7], which allow multiple users to share the fiber bandwidth. Multiple access schemes available for optical LAN S include [8, 9] Time division multiple access (TDMA); Wavelength-division multiple access (WDMA); and Code division multiple access (CDMA). n the present work, OCDMA scheme has been an increasing interest for fiber optic systems in wide area optical communication networks because it allows multiple users to access the system asynchronously and simultaneously. OCDMA is expected for further ultra high speed and real time 650

2 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp computer communications where there is strong demand for the systems to support several kinds of data with different traffic requirements. have analyzed the performance in terms of SNR and BER. We have taken into account several kinds of data (such as code length parameter, number of active users) with different bit rates. System Analysis Assume that each receiver receives equal power Preceived from each transmitter. n the best case, all the codes are orthogonal to each other and we assume this is the case. deally, when the transmitter code and the receiver code are matched to each other, all the received power goes to either the upper or the lower photodetector of the receiver depending on whether a 0 or a 1 bit is sent by the transmitter. Otherwise, the balanced receiver will receive equal power Preceived/ by both of its photodetectors. As in all other communication systems, the receiver is subject to thermal noise given by [10]: th 4kT Bd 8 kt Bd C RL (1) Where k is the Boltzman constant (1.38X10-3 J/K), T is the ambient temperature, R L the receiver load resistance, and B d is the receiver bit rate and can be expressed as follows: Bd 1 1 Tb RL C () Where T b is the bit period, and C is the load capacitance. Suppose M users are active, M-1 of which are unmatched interfering users. Assume the codes are ideal. Since unmatched channel power splits equally at the photodetectors of the balanced receiver, if a 0 is detected, the upper and lower detectors will detect power can be expressed as the following expressions: 0 P U PU Preceived 0.5( M 1) Preceived (3) 0 P L PL 0.5( M 1) Preceived (4) Similarly, if a 1 is transmitted, the upper and lower detectors will detect power can be expressed as follows: 1 P U PU 0.5( M 1) Preceived (5) 1 P L PL Preceived 0.5( M 1) Preceived (6) The output photocurrent for a transmitted 0 and 1 bits are given by [10]: Sig U L PU PL Preceived. for a 0 bit (7) Sig U L PU PL Preceived. for a 1 bit (8) 651

3 nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Rashed n either case, the shot noise in the output is given by [11]: sh shu shl q Bd U L qmpreceived Bd (9) Where q is the electron charge (1.6x10-19 C), and is the detector responsitivity. Shot noise is due to the particle nature of light. However, in an environment where all the users share the same bandwidth and transmit simultaneously, the incoherent summation of signal powers of the same wavelengths will give rise to excessive fluctuations in the detected power due to the wave nature of light which undergoes constructive and destructive interference [1-18]. The same mechanism also gives rise to the spatial intensity variations in coherent images called speckle. The speckle noise model for a detector detecting a photocurrent is [19, 0]: Belec sp m K opt (10) Where B elec is the electrical bandwidth of the photodetector and v opt is the optical bandwidth used. K is the number of modes in a fiber if multi mode fiber is used and m=1 for polarized light and m= for unpolarized light. The number of modes in a multi-mode optical fiber can be evaluated using the density of states. t can be proven [-5] that the number of guided modes Mg in a graded index fiber is given by: g K w g nk a n (11) Where g is the index exponent and equal to for a parabolic refractive index profile, n is the core refractive index, k w is the wave number and is equal to π/λ, λ is the optical signal wavelength, a is the fiber core radius, and Δn is the relative refractive index difference. For a commercial graded index multi-mode fiber with a = 6.5 μm, n=1.49, and g =. n addition, if B opt is the total optical bandwidth encoded, only one half of the total spectrum will fall on each photodetector, v opt = 0.5 B opt, because of spectral filtering. P U and P L give the photocurrent. Therefore, the output speckle noise is given by [6]: sp P received M Bd 1 mk B opt (1) Since single mode fiber components are used, and the waveguide devices are polarization dependent, K=m= 1. Assuming a large number of active users so that the distribution of shot noise and speckle noise can be approximated as Gaussian, the three noise components arising from different mechanisms are independent and the total noise is their sum: n th sh sp (13) To estimate the throughput, assume for simplicity, that transmission is lossless except for the splitting loss at the star coupler. Signal propagation loss and connector loss can be easily accounted for by scaling up the transmitter power proportionally. For a network with M subscribers, the received power per user will be P t /M. n the worst case, all M subscribers are transmitting at the same time. f the 65 nsan Akademika Publications

4 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp system is shot noise limited (e.g. when a large optical bandwidth and multi-mode fiber with many modes are used), the throughput is given by [7, 8]: S sh M B d sh 0.5 P q SNR T bit/sec (14) Where P t is the transmitting power in mwatt, and SNR is the signal to noise ratio. For a large number of supported users transmitting at moderate power, the system will be speckle noise limited and the throughput is given by [9, 30]: Ssp K Bopt M Bd sp M SNR bit/sec (15) Therefore the total throughput is given by: ST 0.5 P t q SNR K B opt M SNR bit/sec (16) t is theoretically found that the SNR is shot noise limited when the total received optical power M P rec is large and is approximately given by [31]: P SNR q 1 R M Bd (17) Where α=0.5 for amplitude shift keying (ASK) and 1 for phase shift keying (PSK). Where the repeater spacing can be estimated based on the transmitted signal and received signal power by the following formula [3]: 1 RS log10 PT PR (18) Where σ is the signal loss which can be expressed as the following expression [33]: S UV R, db/km (19) Where: the int rinsic loss 0.03, db/km, and (0) n T 4 S Rayleighscattering T0, db/km (1) Where T is ambient temperature, and T 0 is a room temperature (300 ), Δ and λ are the relative refractive index difference and optical wavelength respectively. The absorption losses α UV and α R are given as [13]: UV ge 0 e, db/km () 653

5 nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Rashed 5 7 R 10 4 e, db/km (3) Where ω ge % is the weight percentage of Ge, the correlated ω ge % and the mole fraction x under the form: x 594x 400x 4695 x ge (4) The bit error rate of OCDMA communication system can be estimated as the following [33]: SNR BER.exp. SNR 8, (5) The total aggregate bit rate throughput S T, the dispersion limited transmission distance for OCDMA communication systems are given by the following formula: M L f 0 S T (6) Where f 0 is the center frequency, and η is the fiber dispersion coefficient in ps/nm.km can be expressed as follows [34]: source receiver mat., (7) The three components of the system that can contribute to the system rise time are as the following: i) The rise time of the transmitting source source (typically equal to value of 16 psec). ii) The rise time of the receiver η receiver (typically equal to value of 5 psec). iii) The material dispersion time of the fiber η mat which is given by the following equation:... d n mat c d, (8) Where Δλ is the spectral line width of the optical source, and c is the velocity of light (3x10 8 m/sec). Where n is the refractive index of pure Silica material and can be expressed within empirical Sellemier equation as [35]: n A1 A A3 A4 A5 A6, (9) While the first and second diffraction of refractive index n, with respect to optical signal wavelength λ, is given by [36]: dn 1 d n A1 A A3 A4 A5 A6, 6 A A A 4 (30) 654 nsan Akademika Publications

6 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp d n d 1 A1 A 3 A A n 3 A 3A4 4 3 A4 3 A A 5A6 6 3 A6 3 A dn, d (31) The set of parameters of empirical equation coefficients of silica material are recast as the following [36]: A 1= , A = (T/T 0), A 3= , A 4= (T/T 0), A 5=0.899, and A 6= (T/T 0). Where T is the ambient temperature, and T 0 is the room temperature. Based on Eqs. (18, 6), the number of repeater stations can be given by [37]: L NS RS (3) 3 Simulation Results and Performance Analysis The model has been presented the ultra wavelength multiplexing in OCDMA communication systems for wide area network applications under the set of the wide range of the operating parameters as shown in Table 1 is listed below. Table 1: Proposed operating parameters for our suggested OCDMA transmission system [, 5, 8, 13]. Operating parameter Definition Value and unit T Ambient temperature 300 K T 375 K R L Load resistance 50 KΩ C Load capacitance 0.0 pf th Thermal noise 0x10-16 A Detector responsitivity 0.8 A/Watt th 100x10-16 A sh Shot noise 5x10-16 A sh 150x10-16 A B elec Electrical bandwidth 1 MHz sp Speckle noise 0x10-14 A sp 100x10-14 A M Number of active users 1000 M B opt Optical bandwidth 1.8 THz P T Transmitting power 100 mwatt P t 1 Watt x Germanium doping 0 % P R Received desired signal power 100 μwatt λ Optical signal wavelength 1.3 μm λ 1.55 μm Δn Relative refractive index difference f 0 Center frequency 00 THz 655

7 nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Rashed Based on the model equations analysis, assumed set of the operating parameters as listed in the Table 1 above, and based on the series of the figs. (1-9), the following facts are assured: i) Fig. 1 has assured that total throughput decreases with increasing number of active users or subscribers and with decreasing transmitted signal power. ii) Figs. (, 3) has indicated that signal to noise ratio increases and bit error rates decrease with increasing transmitted signal power and decreasing number of active users. iii) Figs. (4, 5) have proved that transmission distance increasing with increasing both number of iv) active users and operating optical signal wavelength and operating at room temperature. Figs. (6, 7) have assured that repeater spacing increases with decreasing both relative refractive index difference and ambient temperatures over room temperatures and increasing operating signal wavelength. v) Figs. (8, 9) have indicated that number of repeater stations increases with increasing total number of subscribers. While operating in room temperature, that results in decreasing number of repeater stations and thus to decrease overall systems costs. Fig.1: Total throughput in relation to number of active users at the assumed set of the operating parameters. 656 nsan Akademika Publications

8 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Fig.: Signal to noise ratio in relation to transmitted signal power and total number of active users at the assumed set of the operating parameters. Fig.3: Bit error rate in relation to transmitted signal power and total number of active users at the assumed set of the operating parameters

9 nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Rashed Fig.4: Transmission distance in relation to ambient temperature and number of active subscribers at the assumed set of the operating parameters. Fig.5 : Transmission distance in relation to ambient temperature and number of active subscribers at the assumed set of the operating parameters. 658 nsan Akademika Publications

10 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Fig.6: Repeater spacing in relation to ambient temperature and relative refractive index difference at the assumed set of the operating parameters. Fig.7: Repeater spacing in relation to ambient temperature and relative refractive index difference at the assumed set of the operating parameters

11 nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Rashed Fig.8: Number of repeater stations against number of active users at the assumed set of the operating parameters. Fig.9: Number of repeater stations against number of active users at the assumed set of the operating parameters. 4 Conclusions The model ultra wide wavelength division multiplexing (UW-WDM) optical code division multiple access (OCDMA) communication systems in wide area optical communication networks (WAOCNs). t is theoretically found that the total throughput decreases with increasing number of active users over the system, while increasing with increasing transmitted signal power. SNR increases and BER decreases with increasing transmitted signal power and with minimum number of subscribers. Relative refractive index difference and high ambient temperatures are the main dramatic factors that reduces transmission distance and repeater spacing and increasing number of repeater stations overall the 660 nsan Akademika Publications

12 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp OCDMA communication systems. t is recommended to operate at third transmission window in order to decrease number of repeater stations over all OCDMA communication networks. References [1] C. Ji, R. G. Broeke, Y. Du, C. Jing, N. Chubun, P. Bjeletich, F. Olsson, S. Lourdudoss, R. Welty, C. Reinhardt, P. L. Stephan, and S. J. B. Yoo, Monolithically ntegrated np Based Photonic Chip Development for OCDMA Systems, EEE J. Sel. Top. Quantum Electron., Vol. 11, No., pp , 005. [] L. Tancevski,. Andonovic, M. Tur and J. Budin, Massive Optical LAN s Using Wavelength Hopping/Time Spreading with ncreased Security, EEE Photonics Tech. Lett., Vol. 8, No. 7, pp , July [3] Ahmed Nabih Zaki Rashed, Current Trends of High Capacity Optical nterconnections, nternational Journal of Advanced Research in Computer Science and Electronics Engineering (JARCSEE), Vol. 1, No. 9, pp. 1-15, November 01. [4] J.Y. Hui, Pattern Code Modulation and Optical Decoding A Novel Code Division Multiplexing Technique for Multifiber Networks, EEE Journal on Selected Areas in Communications, Vol. SAC-3, No. 6, pp , Nov [5] P.R. Prucnal, M.A. Santoro and T. R. Fan, Spread Spectrum Fiber Optic Local Area Network Using Optical Processing, Journal of Lightwave Technology, Vol. LT-4, No. 5, pp , May [6] Ahmed Nabih Zaki Rashed, Transmission Capacity mprovement of Ultra Wide Wavelength Division Multiplexing (UV-WDM) Submarine Fiber Cable Systems for Long Haul Depths, nternational Journal of Advanced Research in Computer Science and Electronics Engineering (JARCSEE), Vol. 1, No. 10, pp. 9-17, December 01. [7] W.C. Kwong, P.A. Perrier, P.R. Prucnal, Performance Comparison of Asynchronous and Synchronous Code-Division Multiple Access Techniques for Fiber Optic Local Area Networks, EEE Trans. on Communications, Vol. 39, No. 11, pp , Nov [8] D.D. Sampson, R.A. Griffin, and D.A. Jackson, Photonic CDMA by Coherent Matched Filtering Using Time-Addressed Coding in Optical Ladder Networks, J. Lightwave Tech., Vol. 1, no. 11, pp , Nov [9] J. Cao, R. G. Broeke, N. Fontaine, W. Cong, C. Ji, Y. Du, N. Chubun, K. Aihara, A.-V. Pham, J. P. Heritage, B. H. Kolner, S. J. B. Yoo, F. Olsson, S. Lourdudoss, and P. L. Stephan, Error Free Spectral Encoding and Decoding Operation of np OCDMA Encoder, presented at the Optical Fiber Communications Conference, Anaheim, California, USA, 5 10 Mar [10] Abd El-Naser A. Mohammed, Mohamed A. metawe e, Ahmed Nabih Zaki Rashed, and Amina E. M. El-Nabawy Unguided Nonlinear Optical Laser Pulses Propagate in Waters With Soliton Transmission Technique, nternational Journal of Multidisciplinary Sciences and Engineering (JMSE), Vol., No. 1, pp. 1-10, March 011. [11] W. Cong, C. Yang, R. P. Scott, V. J. Hernandez, N. K. Fontaine, B. H. Kolner, J. P. Heritage, and S. J. B. Yoo, Demonstration of 160 and 30 Gbit/sec SPECTS OCDMA Network Test beds, EEE Photon. Technol. Lett. 18, Vol. 1, No. 3, pp , 006. [1] X. Wang and K. Kitayama, Analysis of Beat Noise in Coherent and ncoherent Time Spreading OCDMA, J. Lightwave Technol., Vol., No. 3, pp. 6 35, 004. [13] Ahmed Nabih Zaki Rashed, Different Electro-optic Modulators (EOMs) Characteristics for High Data Rate Capability Systems Operations, Accepted in Arabian journal of Science and Engineering (AJSE), Springer site

13 nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp Rashed [14] T. Eltaif, H. M. H. Shalaby, and S. Shaari, A novel Successive nterference Cancellation Scheme in OCDMA System, in Proc. EEE Conf. CSE, pp , 006. [15] T. Eltaif, H. M. H. Shalaby, S. Shaari, and M. M. N. Hamarsheh, Proposal of Successive nterference Cancellation Scheme in Optical Code Division Multiplexing Systems, Opt. Eng., Vol. 47, No. 3, pp. 35-4, 008. [16] T. Eltaif, H. M. H. Shalaby, S. Shaari, and M. M. N. Hamarsheh, Performance Analysis of Successive nterference Cancellation Scheme for Optical CDMA Systems Using Modified Prime Sequence Codes, Proc. SPE, Vol. 6, No., pp , 008. [17] Hossam M. H. Shalaby, Performance Analysis of an Optical CDMA Random Access Protocol journal of lightwave technology, Vol., No. 5, pp , May 004. [18]. B. Djordjevic, and B. Vasic, Combinatorial Constructions of Optical Orthogonal Codes for OCDMA Systems, EEE communications letters, Vol. 8, No. 6, pp , June 004. [19] A. Stok, and E. H. Sargent, System Performance Comparison of Optical CDMA and WDMA in A broadcast Local Area Network, EEE Communications Letters, Vol.6, No.9, pp , Sep. 00. [0] C. G. Brugeaud, A. J. Vergonjanne and J. P. Cances, Prime Code Efficiency in DS OCDMA Systems using Parallel nterference Cancellation, journal of communications, Vol., No.3, pp , May 007. [1] B. Huiszoon, ntegrated Parallel Spectral OCDMA En/Decoder, EEE Photonics Technology Letters, Vol. 19, No. 7, pp , April 007. [] C. Malik, and S. Tripathi, Performance Evaluation and Comparison of Optical CDMA Networks, nternational Journal of Electronics & Communication Technology (JECT), Vol., No. 1, pp , March 011. [3] A. Zaccarin and M. Kavehrad, An Optical CDMA System Based on Spectral Encoding of LED, EEE Photonics Technology Letters, Vol. 4, No. 4, pp479-48, April [4] M. Kavehrad and D. Zaccarin, Optical Code-Division-Multiplexed Systems Based on Spectral Encoding of Noncoherent Sources, Journal of Lightwave Technology, Vol. 13, No. 3, pp , March [5]. Hinkov, V. Hinkov, K. versen and O. Ziemann, Feasibility of Optical CDMA Using Spectral Encoding by Acoustically Tunable Optical Filters, Electronics Letters, Vol. 31, No. 5, pp , March [6] L. Boivin, M.C. Nuss, W.H. Knox and J.B. Stark, "06-Channel Chirped Pulse Wavelength Division Multiplexed Transmitter," Elect. Lett., Vol. 33, No. 10, pp , May [7] F. Bilodeau, D.C. Johnson, S. Theriault, B. Malo, J. Albert and K.O. Hill, An All-fiber Dense Wavelength Division Multiplexer/Demultiplexer Using Photoimprinted Bragg Gratings, EEE Photonics Technology Letters, Vol.7, No. 4, pp , Apr [8] M. M. Karbassian and H. G. Shiraz, Fresh Prime Codes Evaluation for Synchronous PPM and OPPM Signaling for Optical CDMA Networks, J. Lightw. Technol., Vol. 5, No. 6, pp , Jun [9] M. M. Karbassian and H. G. Shiraz, Performance Analysis of Heterodyne Detected Coherent Optical CDMA Using A novel Prime Code Family, J. Lightw. Technol., Vol. 5, No. 10, pp , Oct [30] M. M. Karbassian and H. G. Shiraz, Phase Modulations Analyses in Coherent Homodyne Optical CDMA Network Using A novel Prime Code Family, in Proc. AENG WCE 07, Jul. 007, pp [31] M. M. Karbassian and H. G. Shiraz, Study of Phase Modulations With Dual Balanced Detection in Coherent Homodyne Optical CDMA Network, J. Lightw. Technol., Vol. 6, No. 16, pp , Aug nsan Akademika Publications

14 Rashed nternational Journal of Basic and Applied Science Vol. 01, No. 03, Jan 013, pp [3] M. M. Karbassian and H. G. Shiraz, Novel Channel nterference Reduction in Optical Synchronous FSK CDMA Networks Using Aa datafree Reference, J. Lightw. Technol., Vol. 6, No. 8, pp , Apr [33] M. M. Karbassian and H. G. Shiraz, Frequency Shift Keying Optical Code Division Multiple Access System With Novel nterference Cancellation, Microw. Opt. Technol. Lett., Vol. 50, No. 4, pp , Apr [34] Abd El-Naser A. Mohammed, Mohamed M. E. El-Halawany, Ahmed Nabih Zaki Rashed, and Mohamoud M. Eid Optical Add Drop Multiplexers with UW-DWDM Technique in Metro Optical Access Communication Networks, Nonlinear Optics and Quantum Optics, Vol. 44, No. 1, pp. 5 39, 01. [35] Abd El-Naser A. Mohammed, Mohamed M. E. El-Halawany, Ahmed Nabih Zaki Rashed, and Mohammed S. F. Tabour High Transmission Performance of Radio over Fiber Systems over Traditional Optical Fiber Communication Systems Using Different Coding Formats for Long Haul Applications, Nonlinear Optics and Quantum Optics, Vol. 44, No. 1, pp , 01. [36] Ahmed Nabih Zaki Rashed, New Trends of Forward Fiber Raman Amplification for Dense Wavelength Division Multiplexing (DWDM) Photonic Communication Networks, nternational Journal of Soft Computing, Vol. 6, No., pp. 6-3, 011. [37] Abd El-Naser A. Mohammed, Ahmed Nabih Zaki Rashed, and Mohamoud M. Eid, Recent Advances of Distributed Optical Fiber Raman Amplifiers in Ultra Wide Wavelength Division Multiplexing Telecommunication Networks, Journal of Engineering and Technology Research, Vol. 4, No., pp. -3, Feb