Simulative analysis of pre- and post-compensation using CRZ format in WDM optical transmission link Bindiya Jain, Manoj Kumar Department of Electronics and Communication Engineering, DAV Institute of Engineering and Technology, Jalandhar, Punjab, India article info Article history: Received 28 January 2009 Accepted 18 May 2009 Keywords: Dispersion map Pre- and post-compensation WDM EDC abstract This paper reports the effects of pre- and post-compensation using CRZ modulation format in long-haul WDM optical transmission link using wavelengths in three bandwidths viz. 1537.4; 1550; 1562.6nm at per channel bit rates of 10 Gbit/s. It has been investigated here that optimization of dispersion map results in improved management of nonlinear effects in long-haul light wave systems operating in the quasi-linear regime. In addition, pre- and post-dispersion compensation was applied at the transmitter and receiver depending on the signal wavelength, which resulted in improvement of performance metrics viz. Q 2 (dB), BER and OSNR over longer transmission distances. It is reported here that optimum values of Q 2 dB of 17.1dB, BER of 8.4933e 015 and OSNR of 30.1dB are obtained at 1550 nm at a transmission distance of 7360 km with pre- and post-compensation using CRZ modulation format. & 2009 Elsevier GmbH. All rights reserved. 1. Introduction In the case of single-channel transmission, the interaction between self-phase modulation (SPM) and group velocity disper- sion (GVD) causes severe waveform distortion involving compara- tively higher levels of input power required for long-haul transmission. Fortunately, there are several techniques available that can be used to overcome this nonlinear impairment. Dispersion management, which uses distributed in-line disper- sion compensation using dispersion compensated fibers (DCFs) and fiber Bragg grating (FBG) instead of lumped compensation at the receiver or the transmitter, is quite effective in suppressing the SPM–GVD interaction [1]. Torger Tokle [2] reported that disper- sion management using recently developed fibres in combination with advanced modulation formats significantly improves the transmission performance compared to traditional systems. Zhang and Hui [3] investigated the SPM limitation on system perfor- mance for dispersion-managed optical systems and reported comparison on several optical modulation formats. A first-order linear relationship between SPM-limited maximum transmission distance and signal optical power is found to be applicable to all the modulation formats investigated. Moreover, advanced mod- ulation formats such as RZ, CS-RZ and RZ-DPSK have shown improved tolerance to SPM-induced nonlinear distortion com- pared to the NRZ counterpart. Different technologies are available for the compensation of chromatic dispersion. Electronic dispersion compensation (EDC) could be used together with an advanced modulation format for maximum dispersion tolerance. Also, strategies for increasing the dispersion tolerance could be used in combination with fixed optical dispersion compensation in order to achieve long-haul transmission distance. A 20 Gbit/s-based soliton wavelength division multiplexed (WDM) transmission experiment using periodic dispersion compensation and dispersion slope compen- sation were demonstrated. Accumulated dispersion slope was compensated with two methods. The first method was periodical individual dispersion compensation. By using this technique, 60 Gbit/s WDM transmission over 8000 km was demonstrated. The second method was the use of a dispersion-flattened transmission fiber. 160 Gbit/s (20 Gbit/s  8 WDM) transmission over 4000 km using periodically dispersion compensated disper- sion-flattened fiber was also demonstrated [4]. In the past, NRZ has been used advantageously as it provided minimum optical bandwidth and minimum optical peak power per bit interval for a given average power, thus enabling higher spectral efficiency in the linear regime. However, with increased bit rates, it has been shown that return-to-zero (RZ) modulation formats offer certain advantages over NRZ, as they tend to be more robust against waveform distortion induced by the SPM– GVD interaction. For instance, RZ modulation is more tolerant to non-optimized dispersion maps than NRZ schemes [5]. The use of Fiber Bragg gratings (FBG) had been proposed for compensating the chromatic dispersion several years ago [6]. Such a device reflects light when its wavelength corresponds to the grating period. When the grating is chirped, that is when its period varies Contents lists available at ScienceDirect journal homepage: www.elsevier.de/ijleo Optik 0030-4026/$ - see front matter & 2009 Elsevier GmbH. All rights reserved. doi:10.1016/j.ijleo.2009.05.029 E-mail addresses: bindiyajain29@yahoo.com (B. Jain), mk_daviet@rediffmail.com (M. Kumar). Optik 121 (2010) 1948–1954