Abstract:
Chromatic dispersion (CD) is a phenomenon caused by wavelength dependent group velocity
of an optical signal which travels at slightly different speeds in an optical fiber and leads to
inter-symbol interference that eventually results in data loss and traffic interruption. As bit
rates of optical fiber communication are increased, CD and dispersion slope also increase and
hence it creates a big problem to transmit the data. The traditional means of decreasing the
CD and dispersion slope by the deployment of dispersion compensating fiber (DCF) bundles
throughout the optical network. Insertion loss and nonlinearity are the main drawbacks of
using DCF for CD and dispersion slope compensation. CD and dispersion slope
compensation using reflective Fiber Bragg Grating (FBG) is technically sound and cost
effective. FBGs are also compact and provide no nonlinearity. In this thesis, an attempt is
made to develop analytical models for CD and dispersion slope compensator using linearly
chirped FBG by suppressing the reflected side lobes. Side lobes of the FBGs limit the CD
compensation performance and introduce noise in the transmission system. Apodization is
usually used to suppress the side lobes. Different apodization functions are compared to find
out the best fit for CD compensation. It is found that the sinc apodization function is the most
appropriate function to achieve significant negative dispersion in terms of strength factor and
FBG length. Results show that a 10 cm FBG provides maximum negative dispersion (-70
ps/nm) and dispersion slope (-9 ps/nm2) at 1558 nm wavelength. Using the developed models
MATLAB simulation is carried out to compensate CD for an optical transmission of various
link length, input power and bit rate. The analysis and findings of this thesis will be helpful
in designing appropriate dispersion compensation mechanism in modern high bit rate optical
transmission system.
