Performance Enhancement of Wavelength Division Passive Optical Networks

Abstract

Wavelength division multiplexed passive optical is promising technique to achieve a high data rate and large no. of user. The notable advantages of WDM PON is the combination of reliability, cheap in cost, accessible bandwidth, high security, large optical reach and it can support large number of ONU. There are multiple approaches to achieve colorless WDM PON using different transmission techniques. In this research work, we accentuated on the design of 4 channels WDM PON system incorporating different modulation formats for both uplink and downlink stages by using 10 Gbps and transmitter diversity. A 40-km-long colorless symmetrical WDM-PON with differential quadrature phase shift keying (DQPSK) in downstream and non return to zero (NRZ) modulation format in upstream to solve crosstalk issues. Also comparison has been made with the system using DPSK for downstream and NRZ for upstream in WDM PON system.

Further, WDM-PON at ultra dense channel spacing is investigated incorporating polarization interleaving. Polarization diversity is included in the system to reduce the polarization interference among WDM channels. This research article investigates the performance of 4 x 20 Gb/s WDM-PON system incorporating polarization interleaving technique at 25 GHz channel spacing and wavelength reuse is also done in the system over 40 km. Moreover, comparison of system with and without polarization diversity has also been done. It is evident that different states of polarizations increase the performance of the system as compared to single SOP.

Finally, a cost effective and easy maintenance based dispersion compensation technique is proposed in ONU of the wavelength reused WDM-PON. Moreover, in order to suppress intra-channel crosstalk DQPSK is employed for downstream and for inter-channel crosstalk suppression, polarization interleaving is used in the system. Furthermore, for the investigation of proposed system in terms of dispersion reduction, three different scenarios are considered such that system with only DCF, linearly chirped FBG and joint module of DCF+FBG. System has total 4 channels and each has bit rate of 20 Gb/s with 25 GHz channel spacings. It is observed that joint module of DCF+FBG has maximum ability to compensate dispersion and linearly chirped FBG has least performance. Proposed joint technique for pulse width reduction in ONU is cost effective, highly efficient to combat with pulse width reduction issues and also needs very less maintenance.