Tremendous improvement has been made possible in wireless technology due to success of OFDM system which is a multi carrier modulation technique with capability to support high data rates. Despite its many advantages OFDM has failed against inter symbol interference (ISI), high sensitivity to Inter carrier interference (ICI), high peak to average power ratio (PAPR), phase noise and band limited channel. Hence the performance of an OFDM system is highly affected by the aforementioned undesired phenomenon. For this reason bandlimited system often employs pulse shaping techniques. In this paper pulse shaping of multi carrier signal is introduced by using various pulse shapes like Rectangular pulse (REC), Raised cosine pulse (RC), Better than raised cosine pulse (BTRC), Sinc power pulse (SP) and Improved sinc power pulse (ISP). The impulse responses and frequency spectrums have been evaluated and compared with system without using pulse shaping. Results obtained by simulation for OFDM system using pulse shaping and without using pulse shaping indicate that the performance of OFDM system with various pulse shapes is better than without using pulse shaping. Along with it can also be observed that among pulse shaping ISP exhibits better performance. Computer simulation has been done by using MATLAB 7.0 software.

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This paper highlights a proposed optimized gain flatness technique for nonuniform gain spectrum of the erbium-doped fiber amplifier (EDFA) by introduction of long period fiber gratings (LPFG). In this analysis, EDFA gain spectrum has been evaluated between 1525 and 1600 nm with −20 dBm input signal power. Attenuation peaks of LPFG are optimized with a grating period of 240 µm and grating length of 30000 µm in the wavelength range of 1.1–1.8 μm, to compensate the peak gain of EDFA. Results have shown that EDFA peak gain of 35.94 dB is achieved at 1532.89 nm wavelength. This 35.94 dB peak gain is flattened up to 2.65 dB using long period fiber gratings. Also, less than ±0.3 dB gain flatness is achieved between 1528 and 1560 nm wavelength. The proposed less complex technique can be used to modify the grating parameters during fabrication in order to produce the loss peak at desired wavelength, which is efficient to flatten EDFA gain peak.