LONG HAUL OPTICAL FIBER TRANSMISSION THROUGH DQPSK MODULAITON

Abstract

In this report, a SIMULINK model has been proposed for the optically amplified DWDM optical transmission system. Given that the demands of ultra-wideband transmission over the Internet, transmission techniques are now considered to be very important. The choice of modulation format used is very important to minimize the fiber dispersion and impairments due to nonlinear effects. Either by deployment of new advanced fibers with ultra-high bit rate or upgrading RZ- 10 Gb/s DWDM optical systems to 40 Gb/s channels, the transmission capacity can be extended to Terabit/s. Modulation formats are considered to be the most efficient technique to respond to current demands and moderately simple to implement in the photonic domain and offer 3-6 dB power gain as well as much more tolerable to linear and nonlinear dispersion impairments. This research work presents DQPSK transmission technique of single light wave channel over optical fiber communication systems. It is capable of doubling the bit-rate compared to conventional OOK (On-Off Keying) signaling techniques. Corning SMF (Single Mode Fiber)-28 has been modeled along with its impairments and dispersions. The versatile nature of this SIMULINK model demonstrates the effects of mismatched dispersion management; hence dispersion penalty in fiber transmission links. DCF (Dispersion Compensating Fiber) model has been proposed to compensate all the impairments and to retrieve the data as it was originally sent. Photonic components integrated in the model can be userdefined, enhanced or removed as desired. Essential theoretical background of the design of the optical DQPSK system is given. Detailed operation and purpose of each component model and its representation in SIMULINK block sets are described. Stages required for future extension of this simulator to support DWDM operations to allow Tb/s transmission are also outlined.