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    40120140502002 40120140502002 Document Transcript

    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 INTERNATIONAL JOURNAL OF ELECTRONICS AND – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME: www.iaeme.com/ijecet.asp Journal Impact Factor (2014): 3.7215 (Calculated by GISI) www.jifactor.com IJECET ©IAEME OSNR CHALLENGE IN DWDM LINK T. S. Khatavkar1 and Prof. (Dr). D. S. Bormane2 1 Electronics and Telecommunication Department of PVG’s College of Engineering & Technology, affiliated to University of Pune; Research Scholar at SCOE, Wadgaon (Bk), Pune. M.S. (India) 2 Principal, J.S.P.M’s Rajashree Shahu College of Engineering, Tathawade, Pune, (India) ABSTRACT Transmission rates for telemedicine are driven primarily by the need for full-motion video, desire for extremely-high-quality images for pathology and radiology, and the ability to carry out sophisticated surgery at nodes with desktop computers. Advanced medical systems demand higher data rates of the order of 40 Gb/s to 100 Gb/s. Current fiber optic systems working at 10 Gb/s need to be migrated to 100 Gb/s line rates; this calls for a theoretical increase in optical signal to noise ratio by 10 dB in order to compensate for the ten times wider receiver bandwidth. This paper brings out the challenges at 40 Gb/s and 100 Gb/s and analyses the possible approaches for enhancing the OSNR performance in DWDM links at these rates. Keywords: DWDM, EDFA, Fiber Raman Amplifiers, OSNR, PMD. 1. INTRODUCTION With the tremendous increase in the bandwidth requirements for the development of very high bandwidth and delay sensitive applications such as Video - driven IP traffic, Telemedicine, Internet Games and network storage, there is a need to maximize the capacity that can be transported by optical backbone networks. The Internet and mobile devices continue to grow as key utilities in peoples’ lives, presenting the optical communications industry with new opportunities and challenges in 2013 to ensure that the networks can keep up with the demand. Therefore the priorities for the optical communications industry are to support the need for faster data rates, more powerful switching, and smarter network architectures that can handle unpredictable and fast – changing traffic patterns and improve cost efficiencies. The internet traffic is continuously growing, and around 20152020, it is expected that the current transmission fibers would become inadequate [1]. 10
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME Application areas such as Telemedicine demand long reach and highest data rates from the optical transport network. Transmission rates for telemedicine are driven primarily by the need for full-motion video, desire for extremely-high-quality images for pathology and radiology, and the ability to carry out sophisticated surgery at nodes with desktop computers. Currently, fiber optic systems are being designed to support data rates as high as 40 Gb/s and 100 Gb/s dense wavelength division multiplexing (DWDM) transport networks for advanced medical systems. The major challenges encountered by the National Telemedicine Network include basically the connectivity/ bandwidth, reach, speed provision, & reliability along with the Telemedicine cost consideration. The key challenge seen by the optical industry is the deployment of 40 Gb/s and 100 Gb/s transponders using the existing 10 Gb/s link engineering rules over existing fiber DWDM setup. Therefore the priorities for the optical communications industry are to support the need for long reach/ long haul systems, faster data rates, more powerful switching, and smarter network architectures that can handle unpredictable and fast – changing traffic patterns and improve cost efficiencies. Long reach or long haul optical fiber transmission can be achieved by using regenerators or amplifiers. Two factors that directly limit system reach and capacity are the signal-to-noise ratio and non-linearity. For fibers, improving these parameters translates into reducing the attenuation and enlarging the effective area (Aeff) [2]. The role of OSNR in DWDM systems is discussed in Section II. Section III throws light on the challenges of 40 Gb/s and 100 Gb/s transmission. Section IV reviews the possible approaches of enhancing the OSNR performance in DWDM links. 2. OSNR in DWDM Links DWDM is a technology that combines large number of independent information carrying wavelengths onto the same fiber and thereby increases the transmission capacity of fiber. The “spectral bands” where the optical fiber and the transmission equipment can operate more efficiently are specified by ITU-T as O, E, S, C, L and U bands (from 1260 nm to 1675 nm). While setting up the transmission link, there is a need to ensure that the signal can be retrieved intelligibly at the receiving end. This can be done preferably by using optical amplifiers that serve as the key component of a DWDM system. When the signal is amplified by the optical amplifier (OA), like EDFA, its optical signal to noise ratio (OSNR) is reduced, and this is the primary reason to have limited number of OAs in a network. One of the mitigation is to use RAMAN amplifier but it also has some intrinsic noise, though it is less than that of EDFA. The OSNR values that matter the most are at the receiver, because a low OSNR value means that the receiver will probably not detect or recover the signal. The OSNR limit is one of the key parameters that determine how far a wavelength can travel prior to regeneration. OSNR serves as a benchmark indicator for the assessment of performance of optical transmission systems. DWDM networks need to operate above their OSNR limit to ensure error – free operation. There exists a direct relationship between OSNR and bit error rate (BER), where BER is the ultimate value to measure the quality of a transmission. Given the OSNR, the empirical formula to calculate BER for single fiber is: Log10 (BER) = 10.7-1.45 (OSNR) (1) In DWDM links a rule of thumb would be to target an OSNR value greater than 15 dB to 18 dB at the receiver. OSNR requirements depend on: • Location: The required OSNR will be different for different locations in the light path. The OSNR requirement will be higher closer to the transmitter and lower closer to the receiver. This 11
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME • • • is because optical amplifiers and reconfigurable add/drop modules (ROADMs) add noise, which means that the OSNR value degrades after going through each optical amplifier or ROADM. To ensure that the OSNR value is high enough for proper detection at the receiver, the number of optical amplifiers and ROADMs needs to be considered when designing a network. Type of Network: For a metro network, an OSNR value of >40 dB at the transmitter might be perfectly acceptable, because there are not many amps between the transmitter and the receiver. For a submarine network, the OSNR requirements at the transmitter are much higher. Data Rate: With the increase in the data rate for a specific modulation format, the OSNR requirement also increases. Target BER: A lower target BER calls for a higher OSNR value. The exact requirements at the receiver will vary from one manufacturer to another. Table 2 displays a few average OSNR figures to guarantee a BER lower than 10-8 at the receiver [3]: TABLE 2 Typical OSNR values 10 40 40 Data Rate (Gb/s) NRZ NRZ DPSK Modulation Format Approx. OSNR (dB) 11 17 14 100 NRZ 100 DPSK 21 18 A higher OSNR translates into a lower BER, which equals fewer errors in transmission and higher quality of service (QoS). The relation and impact of OSNR on system performance is shown in Fig.1 (a) and (b) [4]. Figure.1 (a) Relation between OSNR, BER and QoS; (b) Impact of poor OSNR 3. CHALLENGES OF 40 GB/S AND 100 GB/S TRANSMISSION This section discusses the challenges of 40 Gb/s and 100 Gb/s transmission and the enabling technologies for DWDM transmission at these line rates. The issues involved in DWDM systems and their probable solution [5] are summarized in Table 1. 12
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME TABLE 1: Issues and relevant solution in WDM system Sr. No. 1. 2. 3. 4. 5. 6. Issues Capacity bottleneck Bandwidth Channel interactions Data rates Error performance Spectral efficiency Solution Optical amplifier repeaters Wavelength division multiplexing Dispersion management & modern fibers New transmission formats Forward error correcting codes Coherent Receivers The major challenges include Optical Signal to Noise Ratio (OSNR), Chromatic Dispersion (CD) and Polarization Mode Dispersion (PMD). One of the fundamental limitations in an optically amplified transmission system is the signal-spontaneous beat noise at the receiver caused by accumulated amplified spontaneous emission (ASE). This noise impairment can be characterized in terms of the OSNR. It is a quantitative measurement of how much the signal has been corrupted by noise, during the propagation in a fiber. OSNR is defined as the ratio of the optical signal power to the power of the ASE in a specified bandwidth. This bandwidth is referred to as resolution bandwidth (RBW) and is usually considered as 0.1 nm. OSNR is given by: OSNR = 10 Log10 (Ps/Pn) = dB (signal) – dB (noise) (2) Figure2. Definition of OSNR OSNR is important because it suggests the degree of impairment when the optical signal is carried by an optical transmission system that includes optical amplifiers. Usually values higher than 20dB are needed at the receiver to provide error free 10Gbps non FEC detection. The required OSNR should have sufficient margin to include any impairments arising from CD, PMD, fiber nonlinearities and transmitter and receiver induced distortions. When migrating from 10 Gb/s to 100 Gb/s line rate, the required OSNR must theoretically increase by 10 dB in order to compensate for the ten times wider receiver bandwidth [6]. 13
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME In optically amplified transmission system, performance degrades by the presence of noise from two fundamental sources; viz. ASE and Rayleigh scattering. Of these, ASE is more serious type of noise. Every amplifier contributes ASE, and these contributions get added cumulatively along a chain of amplifiers. Maintaining high OSNR is a challenge for 40 Gb/s and 100 Gb/s longhaul WDM transmission. Chromatic Dispersion and Polarization Mode Dispersion are important sources of distortion in long haul 40 Gb/s and 100 Gb/s systems. Transmission fibers with lower dispersion require shorter dispersion compensation fiber (DCF) and thus tend to have lower PMD. The key requirements to use the existing 10 Gb/s DWDM systems at 40 Gb/s and 100 Gb/s, the spectral efficiency ηs and dispersion tolerance (both CD and PMD) must be increased [7]. Deployment of higher link rates can improve ηs and thus maximize the capacity on existing DWDM systems and fiber pairs. The result of increase in CD and PMD tolerance would eliminate the dispersion compensation units (DCUs) in the DWDM links. This in turn would improve the performance of delay sensitive telecommunication applications such as internet gaming, network storage and telemedicine. Literature review suggests that Coherent Polarization – Multiplexed Quadrature Phase Shift Keying (PM – QPSK) modulation format is a critical enabler that meets the 100 Gb/s requirements [7]. Theoretically speaking, 100 Gb/s means 10 x higher capacity than 10 Gb/s, which indicates a 10 dB performance improvement. Practically 10 dB performance improvement at 100 Gb/s can be achieved by: a. Use of Coherent PM – QPSK (6 dB) [7] b. Use of high coding gain Soft Decision Forward error correction (SD-FEC) scheme (2 – 3 dB) [8]. c. Reduction in penalty allocations (1- 2 dB). This would result in a total performance improvement of 9 – 11 dB, approaching the OSNR sensitivity of 10 Gb/s direct detection OOK systems. From this analysis it can be concluded that for transport of high quality full motion video in telemedicine application the aspects mentioned earlier play a crucial role. The enhancement of channel bit-rate demands a higher OSNR for optical transmission systems. Higher bit rates need higher optical signal-to-noise ratio (OSNR). As discussed earlier, OSNR suggests the degree of impairment caused by optical amplifiers to the signal. 4. TECHNIQUES TO IMPROVE OSNR IN DWDM LINKS The optically amplified DWDM networks form the backbone of the long haul and ultra - long haul commercial terrestrial and submarine systems. This section discusses the various techniques to enhance the OSNR parameter in DWDM links. • Use of advanced fiber technology The OSNR serves as the main constraint in impairment-aware optical routing and is expressed in general by (3) and (4). OSNR= P ch P ch = P ASE S SP BOP (3) Where Pch is the signal power, SSP is the spectral density of ASE noise and BOP bandwidth of optical filter [9]. 14
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME OSNR≈ Pch S (Pp.NF.Nspan) (4) Per-channel power Pch is directly proportional to effective area Aeff of the transmission fiber and the parameter S is directly proportional to the attenuation coefficient of the fiber. Reducing the loss of the transmission fiber and components will increase OSNR. Also increasing the launch power per span is yet another possible approach to enhance OSNR, while maintaining terrestrial span lengths. However, this can increase the non-linear impairments such as self-phase modulation (SPM), cross-phase modulation (XPM), four-wave mixing (FWM) and stimulated Raman scattering (SRS) effects [10]. This suggests the approach of enhancing OSNR using advanced fiber technology wherein fiber with large effective area and ultra-low loss is fabricated. UltraWaveTM fibers with effective area of 107 µm2 and attenuation of 0.187dB/km can be considered to improve OSNR for high data rate systems. Lowest loss in fiber ensures longer distances between amplifiers in DWDM links and increases the OSNR and large effective area suppresses non-linearity. Attenuation less than 0.185 dB/km and Aeff larger than 110 µm2 at 1550 nm, have been reported [2]. Yoshinori Yamamoto et al. demonstrated the enhancement of OSNR by designing pure-silica-core fiber (PSCF) with large effective area, Aeff of 134 µm2 and low loss coefficient of 0.169dB/km [11]. By using depressed cladding profile they suppressed both the micro and macro bending loss of the PSCF. The newly designed PSCF is expected to have the highest OSNR improvement among practical fibers by as much as 3.4 dB in 80 km-span transmission systems compared to standard single mode fiber (SSMF) [11]. In submarine networks, transmission lengths are long so transmission loss is of paramount importance. Large effective area fibers like Corning’s Vascade EX2000 with pure silica core allows ultra low loss and delivers significant OSNR gain up to 4.4 dB relative to a standard G.652 fiber over a 100 km span [12]. Ultra low-loss-fibers with large effective areas and backward-pumped Raman/EDFA amplifiers have demonstrated 112 Gb/s PM-QPSK transmission over 200 km hybrid fiber spans [13]. As mentioned earlier larger effective areas enhance the linearity of fiber by virtue of which the new PSCF would be best suited for the high-speed and long-haul transmission systems. Solid single-core, single-mode fibers, if well designed and fabricated, can have Aeff of 160 µm2 with attenuations of even 0.150 dB/km at 1550 nm have been reported [2]. • Optical Amplifiers Semiconductor optical amplifiers (SOAs) and fiber amplifiers have dominated their use in the existing 10 Gb/s networks. Semiconductor optical amplifiers (SOAs) are attractive as they are compact and can be integrated with other photonic components. However, research reveals that the relatively high insertion loss and optical signal-to-noise ratio (OSNR) degradation hinder commercialization of SOAs [3]. • Cascaded Amplifiers Another parameter that one should consider in optically amplified transmission system is the noise factor (NF) of the amplifiers in cascade. By definition NF (dB) = dB (OSNR)in – dB (OSNR)out (5) 15
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME With NFi and Gi are noise figure and gain in linear units, the total noise factor NFt for a chain of amplifiers can be written as: NFt = NF1 + (NF2 – 1)/G1 + (NF2 – 1)/G1*G2 + ….. Figure 3. (a) Gain after Loss scheme (6) (b) Gain before Loss scheme It means the noise figure of 1st amplifier stages and spans are the main contributors to total NF. The scheme resulting in lower NF i.e. case (b) enhances the OSNR. Moving gain before loss (as in case of a Booster instead of Preamplifier) improves the OSNR in optically amplified DWDM long haul links. This is exactly what Raman amplifier does. Inderpreet Kaur et al have proposed that when TDFA and EDFA are used in series configuration, then gain spectrum is broadened up to 100nm. The gain variation is less than ± 1.5% in the wavelength region of 1460-1580 nm and there is a noticeable reduction in the Noise Figure correspondingly in the hybrid amplifier (not mentioned) [14]. For a system containing N fiber spans, where each span is optically amplified, the simplified OSNR of a 1550 nm signal channel at the end of the system can be expressed as [2]: OSNR [in dB/0.1 nm RBW] = 58 + Pch – Lsp – NF – 10 log10 (N) (7) where Pch is the per- channel power (in dBm) launched into the span; Lsp is the span loss (in dB). The conditions applied to obtain this simplified expression are: • • • NF is same for all OAs All amplifiers compensate for link loss (Gi = Li) All spans have same loss L. From (7), it can be seen that increase in OSNR can be achieved by increasing Pch, decreasing NF and decreasing Lsp. If the OSNR is increased by 3 dB, the length of the system can be doubled, assuming that the amplifiers are at equal distances and operate in linear region. Reduction in NF calls for enhancement of OSNR. From the above discussion it can be inferred that for telemedicine application, enhancement of OSNR becomes the prime focus. • Hybrid Amplifiers In view of improving the quality of the transferred signal, [15] have proposed three typical calculating models of terrestrial DWDM cascaded EDFAs fiber optic communication links using Hybrid amplifier (HFA) at three locations viz. first, mid and last span. The authors have selected a combination of Distributed Raman Amplifier (DRA) and EDFA and proposed general calculating models and suggested algorithm charts to optimize parameters including signal power per channel launched fiber, EDFAs gain and pump power of Raman amplifier for improving optical OSNR at the 16
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME end of link. The methodology used by them involves the use of algorithm-based numerical calculating MathCAD program application in a typical system - WDM Nation-wide links in Vietnam. The optimized results of OSNR are compared with the case of links where parameters are conventionally chosen by experience way. The authors claim an enhancement in OSNR of 1-5 dB over the non-optimized results [14]. The impact of hybrid EDFA/Raman amplification on a coherent WDM multiplexed optical communication system has been studied and modeled. The authors have experimentally demonstrated a 3 dB improvement in the delivered OSNR (as compared to an EDFAonly amplification system) for a 2 Tb/s CoWDM system at 42.84 Gbaud over 124 km of fieldinstalled SMF using DRA. The Q factor improvement was 1.2 dB compared with EDFA amplification only [15]. In this approach, bidirectional pumping cannot be used for performance enhancement, because degradation in OSNR resulted if the launch power was reduced. Also forward Raman amplification, that enhances the gain, degrades the Q factor due to increased nonlinearities at the higher launch power. The feasibility of gain enlargement and equalization on extended reach WDM-ring PON by means of hybrid Raman/EDFA amplification has been investigated by using simulation tools [17]. Another solution to improve OSNR in long haul systems is to employ only distributed Raman amplification (DRA) system. This involves the use of transmission fiber itself as the gain media and high pump power lasers to provide enhanced link performance at 40 Gb/s and 100 Gb/s. Based on the literature survey done so far, hybrid amplifiers enhance the transmission capacity of broadband systems, upgrade the existing systems built with EDFA amplifiers with broader/flatter bandwidth. They provide an ability to carry more wavelength-multiplexed optical channels at given spacing among the channels. If Raman amplifiers are chosen for combination with EDFA, it gives flexibility to the selected band amplification and is less sensitive to nonlinear effects. Hybrid amplifiers are concerned with maximizing the span length and/or minimizing the impairments of fiber nonlinearities, enhancing the EDFAs’ bandwidth and designing “optimal” hybrid amplifiers in order to obtain flat and widest output gain performance. The gain balance between Raman and EDFAs involves complex problem with several degrees of freedom (Optimization technique); OSNR, gain-flatness, bandwidth; number of channels, number of spans and maximum transmission capacity. • Pumping Methods A theoretical investigation about the characterization of RFAs with bidirectional or copropagating Raman pump so as to improve the performance of the amplifier has been proposed [18]. The paper provides a brief theoretical analysis and does not take into account the taxing effect of large pump power requirement and also the issues associated with large pump powers. • Macro Bending Macro bending effect in optical amplifiers is yet another method to improve the doped fiber amplifier Gain and Noise Figure [19]. Macro-bending is defined as a smooth bend of fiber with a bending radius much larger than the fiber radius. Macro-bending modifies the field distribution in optical fibers and thus changes the spectrum of the wavelength dependent loss. The macro bending also reduces the noise figure of EDFA at wavelength shorter than 1550. Since keeping the amount of noise low depends on a high population inversion in the input end of the erbium-doped fiber (EDF), the backward ASE power P –ASE is reduced by the bending loss. Consecutively, the forward ASE power PASE can be reduced when the pump power P is large at this part of the EDF which is especially undesirable. This is attributed and can be described numerically by the following equation: 17
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME NF = 1/G + 2PASE/G*hf (8) where G is the amplifier’s gain, PASE is the ASE power and hf is the photon energy. There exists an inverse relation between the NF and the OSNR. The noise figure decreases appreciably due to bending effect. From the study it can be concluded that the use of advanced fiber technology to enhance OSNR faces a limitation posed by the fabrication of fibers with highest possible effective areas and lowest possible attenuation. For Raman amplification such a system would demand huge pump powers. Also these fibers may pose incompatibility issues while splicing them with conventional standard single mode fibers. Whereas macro-bending technique improves both gain and noise figure by approximately 6 dB and 3 dB, respectively. The method is cost effective which needs 100mW pump power and does not require any additional optical components to flatten the gain, thus enables reduction in the system complexity. Multi-Level Modulation formats • Rapid progress has been achieved in transmission systems including multi-level modulation formats and digital coherent detection techniques to reduce the OSNR requirement. Especially in conjunction with DPSK modulation formats, use of more advanced amplification schemes leads to significant improvement in OSNR performance over conventional EDF only amplification [20].From the literature survey there is further scope to research in achieving enhancement in OSNR by an optimum configuration of hybrid amplifiers with the support of the advanced fiber technology. V. CONCLUSION In conclusion, we state that to improve the OSNR there is a need to enhance the linearity in optical fibers or to increase the input channel power level. An increase in the spectral efficiency using advanced modulation formats, or use of novel fibers can upgrade the performance of the DWDM systems. Next-generation systems and future upgrades of existing systems will benefit from these new concepts emerging from system research. The proposed research is an effort to enhance the optical signal-to-noise ratio by 1-5 dB in DWDM fiber optic transmission link using HFAs and advanced fiber technology in comparison with standard single mode fiber (SSMF) links. REFERENCES [1] [2] [3] [4] [5] [6] [7] Kazunori Mukasa, Katsunori Imamura, Masanori Takahashi, Takeshi Yagi, Development of novel fibers for telecoms application, Optical Fiber Technology, Optical Fiber Technology 16, Elsevier-Science Direct, 2010, 367-377. Pierre Sillard, New fibers for ultra-high capacity transport, Optical Fiber Technology (17), Elsevier-Science Direct, 2011, 495-502. Jean-Sébastien Tassé, What should the OSNR values be in DWDM networks? , Optical/Fiber Testing, Home / Corporate / Blog Home / 2012 / Posted date: 2012-12-06. MRV, Application note on DWDM, Optical Communication Systems, 2002. Neal S. Bergano, Wavelength Division Multiplexing in Long-Haul Transmission Systems, OFC/NFOEC 2011 SC102. Sinclair Vass, Talk on Optical Communications Trends for 2011, JDSU, January 12, 2011. Ted Schmidt,Christian Malouin,Bo Zhang, RossSaunders,et al, “100G Coherent DWDM Transponder Module Enabling Seamless Upgrade of Long Haul Optical Transmission Systems”,NME2.pdf, OSA/OFC/NFOEC 2010. 18
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME [8] I. Djordjevic et.al. Journal of Lightwave Technologies, Vol.23, No.5, May 2005. [9] Milorad Cvijetic, Ivan Djordjevic, Advanced optical communication systems and networks. [10] D. Dahdah, D.Govan, and M. Marhic, Fiber Optical Parametric Amplifier performance in a 1 Tb/s DWDM communication system, IEEE Journal of selected topics in quantum electronics, Vol.18, March/April 2012. [11] Yoshinori Yamamoto, Masaaki Hirano, Kazuya Kuwahara and Takashi Sasaki, OSNREnhancing Pure-Silica-Core Fiber with Large Effective Area and Low Attenuation, OTuI2, OSA/OF/NFOEC 2010. [12] Matthew Guinan, Vanesa Diaz, and Merrion Edwards, The super connected world: Optical Fiber Advances and Next Gen Backbone, Mobile Backhaul, and Access Networks, WP 6024, June 2012, Corning. [13] J.Downie et.al., 112 Gb/s PM-QPSK transmission upto 6000 km with 200 km amplifier spacing and a hybrid fiber span configuration, Optics Express/Optical Society of America, 19(26), 2011. [14] Inderpreet Kaur, Dr. Neena Gupta, A Novel Approach For Performance Improvement of DWDM Systems Using TDFA-EDFA Configuration, International Journal of Electronics & Communication Technology, Vol. 1, Issue 1, December 2010. [15] Tuan Nguyen Van, Hong Do Viet, Enhancing Optical Signal-to-Noise Ratio in Terrestrial Cascaded EDFAs Fiber Optic Communication Links using Hybrid Fiber Amplifier, IEEE, 2009. [16] Paola Frascella, Cleitus Antony et al., Impact of Raman Amplification on a 2 – Tb/s Coherent WDM System”, IEEE Photonics Technology Letters, 23(14), pp. 959-961. [17] B.Neto, C.Reis and N.Wada, Gain Equalization Technique for Raman Amplification Systems based on the Hybrid Optimization Algorithm, IEEE 2009. [18] Li Shuhua, Gong Huaping, Tu Yumeng, Theoretical Investigation on Raman Fiber Amplifiers, IEEE 2010. [19] Siamak Emami, Hairul Azhar Abdul Rashid, Seyed Edris Mirnia, Arman Zarei, Sulaiman Wadi Harun and Harith Ahmad, Doped Fiber Amplifier Characteristic Under Internal and External Perturbation, Selected Topics on Optical Amplifiers in Present Scenario Edited by Sisir Kumar Garai, Intech, 2010. [20] A. Lucero, D. G. Foursa, and J.-X. Cai, Long-Haul Raman/ROPA-Assisted EDFA Systems, OThC3, OSA/OFC/NFOEC, 2009. [21] M.S.V.Vara Prasad, K.Kranthi and K.Krishna Murthy, “QPSK UWB Based Modulator for Reusable Simulink Modeled Pon”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 5, 2013, pp. 66 - 72, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. [22] S.K Mohapatra, R. Bhojray and S.K Mandal, “Analog and Digital Modulation Formats of Optical Fiber Communication within and Beyond 100 Gb/S: A Comparative Overview”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp. 198 - 216, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. [23] Asish B. Mathews and Dr. Pavan Kumar Yadav, “Improved Linearization of Laser Source and Erbium Doped Fiber Amplifier in Radio Over Fiber System”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 5, 2013, pp. 46 - 55, ISSN Print: 0976-6480, ISSN Online: 0976-6499, 19
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 10-20 © IAEME AUTHOR’S DETAIL BIBLIOGRAPHY Tanuja Khatavkar received Bachelor and Master’s degree in Electronics Engineering from Shivaji University, in 1991 and University of Pune in 2004 respectively. She has earned Master’s degree in Business Management with Human Resource as her specialization as well. She is currently pursuing Ph.D. in Electronics and Telecommunication Engineering from Sinhgad College of Engineering, affiliated to University of Pune. She has 23 years of teaching experience and is presently working as Assistant Professor in Electronics and Telecommunication department of Pune Vidyarthi Griha’s College of Engineering and Technology, Pune, Maharashtra (INDIA). She authored a book on Network Fundamentals and Analysis published by WILEY and has also published papers in optical communication field. Prof. Dr. D. S. Bormane- Completed B.E. Electronics from Marathwada University, Aurangabad in 1987, M.E. Electronics from Shivaji University, Kolhapur, Ph.D. Computer from Ramanand Tirth University, Nanded, and has a vast teaching experience of 3 decades as a Lecturer, Assistant Professor, Professor, Head of Department, and is currently working as Principal in J.S.P.M’s Rajarshi Shahu College of Engineering, Pune, Affiliated to University of Pune, Maharashtra (INDIA). He has published about 60+ papers at national and international conferences and journals. 20