Design of Ultrafast OTDM using Optical Delay Line Structure Technique

Abstract

ABSTRACT

As high bandwidth applications continue to emerge, investigation in technologies that will increase transmission capacity becomes necessary. Several technologies have been investigated in recent years to satisfy this increased demand in bandwidth. Of these technologies, Optical Time Division Multiplexing (OTDM) has been presented as a possible solution, supporting a next generation high bit rate. OTDM has transmission advantages such as simultaneous dispersion compensation and regeneration of all channels, reduced requirements to erbium-doped fibre amplifier, gain flatness, and zero cross talk from four-wave mixing (FWM) or stimulated Raman scattering (SRS). Because of these factors OTDM is well suited for "backbone" networks with long spans and few nodes but is also being considered for ultrahigh-speed local area networks (LANs). The present work aims at the designing, simulation and analysis of a structure of optical delay line based on packet interleaved OTDM. By varying various parameters such as bit rate (B), power required (P), extinction ratio, modulation formats etc analysis has been done for an optimum delay line and low propagation loss is realized. To demonstrate the capability of simultaneous packet compression and expansion optical packets with a bit rate of 1 Tb/s was taken and the setup was formed .A 1550nm continuous wave laser is used to generate optical pulses of power 0 decibels and line width 10MHz. A five stage fibre optic delay line is used (n = 32) for the expansion and compression of 32 bit data packets. An ODLS subsystem is created which is the packet compression stage. In the packet compression stage we have extensively concentrated our usage on power splitters and combiners. The packet after passing through each of compression stage is analysed separately to evaluate the packet compression and delay and is then amplified by the amplifier and optical band pass filter (BPF) in order to remove ASE (amplified spontaneous emission). We also have investigated advanced intensity modulation formats of carrier suppressed return zero (CSRZ) and duo binary modulation formats. Their performance has been evaluated on the basis of their spectrum, BER curve and eye diagrams for fibre length of 50km. From the simulation results it is concluded that both modulation formats have their own advantages and their usage primarily depends upon the application they are used in.