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Performance enhancement of wdm optical fiber Communication systems and networks using Error control coding techniques

Mruthyunjaya, H.S (2006) Performance enhancement of wdm optical fiber Communication systems and networks using Error control coding techniques. Phd. Thesis thesis, Manipal Institute of Technology, Manipal.

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In standard point-to-point links a single fiber line has one optical source at its transmitting end and one photo detector at the receiving end. Signals from different light sources use separate and unique optical fibers and uses only very narrow portion of transmission bandwidth capability of a fib er. Wavelength Division Multiplexing (WDM) employed in Optical Fiber communication is similar to frequency division multiplexing principle used in electrical communication systems. Several light beams at different wavelengths can simultaneously propagate over the same optical path. Allthese signals are combined by a multiplexer and are transmitted simultaneously over the same optical fiber. The demultiplexer divides the different wavelengths and directs them to appropriate receivers. When pulses of short duration and high peak power are incident on a scattering medium such as a silica fiber, nonlinear phenomena are observed such as Stimulated Raman Scattering (SRS). This nonlinear phenomenon causes power depletion in the shorter wavelength channels increasing the Bit Error Rate (BER) and degrades the system performance. Investigations have been carried out in this thesis on the reduction of the effect of this nonlinear phenomenon along with thermal and shot noise currents on Binary Asymmetric Channel (BAC) with Intensity Modulation and Direct Detection (IMDD) system by employing error control coding techniques. Investigations on the improvement in BER, number of channels or increase in link length have been conducted by applying Hamming, Golay, Bose Chaudhuri Hocquenghem (BCH) block codes, Reed Soloman (RS) and rate ~ Convolution codes The components in WDM system introduce crosstalk of some form or another. This arises when a signal at a wavelength that is the same (or very close) as the desired wavelength leaks into the desired signal's receiver. The impact of crosstalk on N x N wavelength multiplexer is investigated and studies conducted on reducing all such nonlinear effects by applying error control codes. Erbium Doped Fiber Amplifiers (EDFAs) are used to counter attenuation of optical signal as it travels down the fiber. The dominant noise generated in an optical amplifier is Amplified Spontaneous Emission (ASE). In addition two noises arise from the mixing of different optical wavelengths contained in the light signal and the ASE, which generates two sets of beat wavelengths. Also, since the ASE spans a wide optical range, it can beat against itself giving rise to the noise current. Investigation on these noises along with shot, thermal, SRS, and channel beat have been carried and possible methods on improving systems performance by applying above said error control coding techniques investigated. Investigations have also been carried on performance enhancement of amplified WDM optical systems by employing single and concatenated error control coding with Binary Pulse Position Modulation (BPPM) instead of OOK! ASK modulation in presence of detector shot noise, thermal noise, SRS, intrachannel crosstalk, ASEsignal beat and ASE-ASE beat noises. Comparison has been made between the optical systems with chain of EDF As without coding and systems without EDFA with coding techniques. Conclusions from the obtained results have been derived and possible extension for future work given.

Item Type: Thesis (Phd. Thesis)
Uncontrolled Keywords: Amplified Spontaneous Emission, Binary Pulse Position Modulation, Bit Error Rate, Channel beat noise, Erbium Doped Fiber Amplifier, Error control coding, Error Probability performance, Intensity Modulation andDirect Detection, Relative Intensity Noise, Shot Noise, Stimulated Raman Scattering, Thermal Noise, Wavelength Division Multiplexing.
Subjects: Engineering > MIT Manipal > Electronics and Communication
Depositing User: MIT Library
Date Deposited: 02 Jun 2014 05:58
Last Modified: 07 Nov 2014 09:36

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