# INTRODUCTION ight wave systems used in the core transport network of telecommunication systems operate in the second transmission window. The 1550 nm wavelength region exhibits the lowest attenuation coefficient, thus expanding the repeater distance in the network. However, the influence of the large dispersion coefficient associated with the second transmission window limits the operating speed of the network to 2.5 Gbit/s or less. In order for the network to operate at higher bit-rate, a dispersion management scheme is needed. Dispersion compensation in Optical systems operating at 1550 nm can be achieved by employing dispersion mapping techniques. In this technique, fibres of opposing dispersion coefficient are made to alternate along the length of the optical link. In general NDFs have a large dispersion in comparison to standard SMFs, thus a relatively short NDF can compensate for dispersion accumulated over long links of SMFs . NDFs are easy to install and require little modification to an already existing system. About-1 Assistant Prof.,Amrutvahini College of Engineering,Sangamner About 2 -Assistant Prof.,Amrutvahini College of Engineering,Sangamner About 3 -Prof. E&TC Department Dr.Babasaheb Ambedkar Technological University,Lonere E-Mail-rameshpawase@gmail.com, rplabade@gmail.com, sbdeosarkar@yahoo.com The major disadvantage of NDF is that it exhibits a large attenuation in signal power, as a result more optical amplifiers are generally deployed in the system. This in turn enhances the other limitations in the system because the non-linear attributes of this fibre is considerably higher. Results have also been validated through numerical simulations with the optical system simulator OptSim II. # DCF INFORMATION In order to meet the growing demand of bandwidth for internet and other related communication applications, future long-haul systems are required to operate at bit-rate of 10 Gbit/s, 40 Gbit/s or even higher. In high capacity systems, dispersion compensation is critical. The transmission fibers in the existing network are the standard non-zero dispersion fibres (NZDF)5 with nominal value for dispersion equal to +17 ps / nm ? km . Although these fibers were deployed several decades ago, they are still preferred by system designers today because the high dispersion of the fiber is used efficiently to impair the non-linear manifestation of fibre in systems. However, the accumulation of dispersion in these fibres limits the transmission distance to approximately 60 to 300 km for 10 Gbit/s systems and 4 to 18 km for 40 Gbit/s systems if dispersion compensation is not employed. Hence dispersion compensation is required to increase the transmission distance in systems operating at high bit -rates. Furthermore, the DC device is required to have a sufficiently large bandwidth in order to achieve simultaneous compensation across all the channels. This implies that the DC device must be capable of dispersion slope compensation. Several dispersion and dispersion slope compensating devices have been demonstrated, including single-mode and higher-order-mode dispersion compensating fibres, fibre Bragg grating devices, Although many of these devices have great potential, including tuneable dispersion, single mode dispersion compensating fibres (DCF) are still the only one that is widely deployed. depicted as type 1 in the schematic below, and precompensation depicted as type 2. The accumulated dispersion and relative power for both pre-and postconfiguration are depicted in figure. # DISPERSION MANAGEMENT SYSTEM IN OPTSIM The considered system configurations are depicted in Fig. 1 . In all schemes the transmission line consists of equal numbers of 120 kin SMF and 24 kin DCF sections. The fibre parameters for SMF and DCF are listed in Table 1 . We assumed a partial compensation of second-order dispersion by DCF units. We assumed zero path-average dispersion in all schemes. The amplifier gain, 26.4 dB after SMF section and 19.2 dB after DCF section, equalizes the loss. The amplifier noise figure is supposed to be 6dB. or NRZmodulation format the transmitter emits chirp-free modulated pulses with a risetime of 25% f the bitslot. At the receiver the signal was optically filtered, detected and then electrically filtered. As a measure of system performance Q factor and BER are evaluated that in standard fibre transmissions operating at 10Gb/s at high amplifier spacings of I20km the impact of fibre nonlinearity is diminished by symmetrical ordering of dispersion compensating fibres allowing 1200km The experiment showed that the amount of negative dispersion introduced, with respect to the total accumulated dispersion of the transmission fibre, also impacted on the performance of the system. In the single channel optical system experiment, it was found that the system performance gradually improved as the total dispersion of the transmission fibre tended toward that of the DCF and in a similar fashion, the system performance decreased as the total dispersion of fibre exceeded that of the DCF. Results obtained with no compensation, to for the post-compensation Furthermore, analysis of the Q-factor also revealed that system performance had exceeded the minimum requirement of 6 by a large margin. VI. # CONCLUSION From the above summary, one may conclude that for a single channel, single span optical communication system, the dispersion distance limit increased by introducing dispersion management into the network. ![Fig1: Dispersion Management Schemes](image-2.png "Fig1:") 2![Fig 2: Dispersion Management Schemes implemented in OptSim](image-3.png "Fig 2 :") * Combatting Fibre Nonlinearity In Symmetrical Compensation Schemes Using RZ Modulation FormatAt 120 km Amplifier Spacing Over Standard Fibre DBreuer KPeterman AMattheus SKTuritsyn September , 1997 * Senior Member, IEEE "Pre-and Post-Compensation of Dispersion and linearities in 10-Gb/s WDM MIHayee AEWillner IEEE PHOTONICS TECHNOLOGY LETTERS 9 9 SEPTEMBER 1997 * RZ Versus NRZ Modulation Format for Dispersion Compensated SMF-Based 10-Gb/s Transmission with More Than 100-km Amplifier Spacing CCaspar H.-MFoisel AGladisch NHanik FK¨uppers RALudwig WMattheus BPieper HGStrebel Weber IEEE PHOTONICS TECHNOLOGY LETTERS 11 4 APRIL 1999 * Optical Fibre Communications JohnSenior * Optical Fibre Communications GerdKeiser * Understanding Optical Communications JRHarry Dutton