Analysis, Design and Performance Evaluation of Optical Fiber

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Analysis, Design and Performance Evaluation of Optical Fiber Analysis, Design and Performance Evaluation of Optical Fiber Spectrum-Sliced WDM Systems by Vivek Arya Dr. Ira Jacobs, Chairman Electrical Engineering ABSTRACTThis dissertation investigates the design and performance issues of a recently demonstrated technique,termed as spectrum-slicing, for implementing wavelength-division-multiplexing (WDM) in opticalfiber systems. Conventional WDM systems employ laser diodes operating at discrete wavelengths ascarriers for the different data channels that are to be multiplexed. Spectrum-slicing provides anattractive low-cost alternative to the use of multiple coherent lasers for such WDM applications byutilizing spectral slices of a broadband noise source for the different data channels. The principalbroadband noise source considered is the amplified spontaneous emission (ASE) noise from anoptical amplifier. Each slice of the spectrum is actually a burst of noise that is modulated individuallyfor a high capacity WDM system. The stochastic nature of the broadband source gives rise to excessintensity noise which results in a power penalty at the receiver. One way to minimize this penalty, asproposed and analyzed for the first time in this work, is to use an optical preamplifier receiver. It is shown that when an optical preamplifier receiver is used, there exists an optimum filterbandwidth which optimizes the detection sensitivity (minimizes the average number of photons/bit) fora given error probability. Moreover the evaluated detection sensitivity represents an order ofmagnitude ( > 10 dB) improvement over conventional PIN receiver-based detection techniques forsuch spectrum-sliced communication systems. The optimum is a consequence of signal energyfluctuations dominating at low values of the signal time bandwidth product (m), and the preamplifierASE noise dominating at high values of m. Operation at the optimum bandwidth renders the channelerror probability to be a strong function of the optical bandwidth, thus providing motivation for the use__________________Abstract iiof forward error correction coding (FEC). System capacity (for BER = 10 −12 ) is shown to be 23 Gb/swithout coding, and 75 Gb/s with a (255,239) Reed Solomon code. The effect of non-rectangular spectra on receiver sensitivity is investigated for both OOK andFSK transmission, assuming the system (de)multiplexer filters to be N’th order Butterworth bandpass.Although narrower filters are recommended for improving power budget, it is shown that systempenalty due to filter shape may be kept < 1 dB by employing filters with N > 2. Moreover spectrum-sliced FSK systems using optical preamplifier receivers are shown, for the first time, to perform betterin a peak optical power limited environment. Performance-optimized spectrum-sliced WDM systemshave potential use in both local loop and long-distance fiber communication systems which requirelow-cost WDM equipment for high data rate applications.__________________Abstract iii