Analysing and Improving T.O.D Effect on Ultra Long Haul High Bit Rate Optical Communication System

Abstract

This project presents a comprehensive investigation on pulse distortions due to
the third-order dispersion (TOD) on ultra-high speed long-haul single channel optical fiber
communication system using Optical fiber System. The optical communication system
consists of dispersion-managed line with periodic amplification by Er-doped fiber
amplifiers. The presence of the TOD introduces broadening and an additional temporal
shift on the propagating pulse. The impact of TOD is observed at the receiving end of
transmission line considering the variation of different factors such as transmission reach,
bit rate, duty cycle, pulse shape and fiber type. Only self-phase modulation, second and
third order dispersion, fiber loss, and amplified spontaneous emission (ASE) noise are
considered here. BER performance is also observed considering receiver noise. The
numerical result shows that temporal effect on pulse center decreases in the case of NRZ
Gaussian pulse while using SSMF-DCF system and when both group velocity dispersion and
TOD effects are considered. At first, pulse broadening due to GVD and TOD has been
observed by varying bit rates from 40 Gb/s to 160 Gb/s. Then temporal shift of pulse
center position is investigated by varying transmission distance, bit rate, duty cycle, input
pulse shape and different transmission models for DM systems. Finally, performance of
input pulses such as Gaussian and super-Gaussian pulses is evaluated by varying bit rates
from 40 Gb/s to 160 Gb/s. Fiber chromatic dispersion, SPM and receiver noises are taken
into account for the numerical calculation. DM transmission line is considered for each
scheme. A PRBS of length 27−1 is used to propagate through the optical fiber. The presence
of the TOD causes pulse broadening, long oscillatory tail as well as introduces a temporal
shift to pulse irrespective of shape. With the increase of bit rate, temporal shift of pulse
center increases. Pulse center position also changes with the variation of duty cycles and it
is found that temporal shift decreases with duty cycle. Time shift of pulse also occurs
depending on pulse shape and fiber type.