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Title of Thesis

Muhammad Zafrullah
Institute/University/Department Details
University Of Engineering And Technology/Electrical Engineering
Electrical Engineering
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
dissertation, pulse propagation, optical fibers, pmd measurement, soliton amplification, polarization mode dispersion, group velocity dispersion

The primary objective of this thesis focuses on the precise measurement of Polarization Mode Dispersion (PMD) in single mode and polarization maintaining fibers using interferometric method. The numerical simulations are conducted to study the soliton propagation under the combined impact of PMD and higher order effects which conforms to the experimentally observed soliton splitting. Also, numerical simulation is presented to optimize the design parameters of Erbium Doped Fiber Amplifier (EDFA) for soliton amplification.

The measurements of different parameters remained always a prime feature for the practical development of any accurate system. In connection with the optical communication, Phenomenon of PMD in single mode optical fibers takes place due to enormous polarization cross couplings throughout a specific length of the fiber and becomes a deteriorating factor for high speed fiber optic networks. It is imperative to gain insight into the PMD while designing an accurate high-speed optical communication system. Techniques for measuring the distribution of PMD along a fiber cable would thus be very useful in encountering the set backs in the high bit rate communication networks, where we have dealt this problem with practical measurements carried out in the lab set up to a high accuracy level. Although, there do exist PMD measurement techniques in optical fibers like Poincare sphere method, Jones matrix method and fixed analyzer technique, but our focus has been the interferometric method, which provides direct measurement of PMD in time domain. Over last few years there has been significant work carried out using interferometric method to measure PMD in single mode ordinary optical fiber widely used in telecommunication applications. A precise optical test set-up is developed in lab, which provides the exact picture of the state of polarization through a certain fiber length. The designed interferometric set-up is not only useful to measure the PMD of standard telecommunication fibers but equally well capable of measuring the birefringence (or beat-length) and PMD of hi-bi (mostly called as Polarization Maintaining) optical fibers. White light interferometric set-up developed is a multiple- use instrument for variety of research and development activities in the fields of fiber optic communications and sensors. The practicality of the set up is used extensive to characterize the spectral and coherence related properties of light sources, as well as various other fibers and integrated optical devices.

The information flow is going beyond the bottlenecks. The increased bit rate requires the use of short pulses, which have inherited nonlinearities. Eventually, optical solitons will be the ultimate candidate, which use the nonlinear self phase modulation to counteract the group velocity dispersion (GVD). For an accurate system the fiber nonlinearities can be balanced by GVD whereas fiber losses can be compensated by periodic or distributed amplification. All these systems are subjected to PMD and higher order effects, which seriously degrade the system performance. However, coexistence of the higher values of PMD and higher order effects can be used advantageously in generating a dual pulse train. The numerical simulation incorporating these effects results in pulse splitting which conforms to the similar effects which have been experimentally demonstrated in a mode-locked figure-eight fiber laser where optical pulses go through many round trips in the cavity. The relative amplitude, pulse separation and wavelength separation can be tuned through the polarization control.

In addition, simulation of EDFA for the amplification of optical solitons is presented. Various parameters can be varied as a control to optimize soliton amplification. It is possible to design EDFA for different pulse widths depending upon the dispersion, and loss of the fiber including a control over EDFA parameters. The optimized values of the pump range, erbium ion concentration and gain length have been determined to acquire distortion less amplification of soliton.

Download Full Thesis
2052.17 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
77.61 KB
2 1 Introduction 1
107.47 KB
  1.1 Overview of the Dissertation 6
  1.2 References 7
3 2 Pulse Propagation in Optical Fibers 10
296.92 KB
  2.1 Introduction 10
  2.2 Wave Theory 11
  2.3 Dispersion in Single Mode Fibers 12
  2.4 Nonlinear Optical Effects 18
  2.5 Soliton Propagation 23
  2.6 Soliton Based Communication Systems 27
  2.7 Conclusion 33
  2.8 References 33
4 3 PMD Measurement And Device Characterization 37
405.6 KB
  3.1 Introduction 37
  3.2 Standard Techniques for PMD Measurement 38
  3.3 White Light Interferometry 42
  3.4 Experimental Set-up for WLI 47
  3.5 Experimental Results 50
  3.6 PMD Measurement from WLI Data 52
  3.7 Characterization of Devices through WLI 58
  3.8 Conclusion 64
  3.9 References 64
5 4 Combined Impact of Polarization Mode Dispersion and Higher Order Effects on Solitons 68
144.42 KB
  4.1 Introduction 68
  4.2 Mathematical modeling 69
  4.3 Numerical simulation 73
  4.4 Experiment 75
  4.5 Conclusions 76
  4.6 References 77
6 5 Soliton Amplification 79
269.98 KB
  5.1 Introduction 79
  5.2 Erbium Doped Fiber Amplifier 80
  5.3 Characterization of EDFA 83
  5.4 EDFA Configuration Architecture 85
  5.5 Beam Propagation Method 86
  5.6 Optical Solitons 91
  5.7 EDFA Design 93
  5.8 Soliton Amplification 95
  5.9 Conclusion 99
  5.10 References 99
7 6 Conclusion 102
36.91 KB
  6.1 Summary of the accomplishments 102
  6.2 Recommendations for future work 103
8 7 List of Pertinent Publications/Presentations 105
853.71 KB