Performance Comparison of High Speed LAN Optical CDMA Systems at Different Data Rates

Abstract

OCDMA is a highly flexible technique to achieve high-speed connectivity with large bandwidth. Data access security and ability to support asynchronous, bursty data transmission are two of the main driving forces behind a lot of interest in the OCDMA techniques. On the other hand, the poor spectral efficiency of OCDMA systems demand appropriate choice of coding techniques and multi-access interference (MAI) is often a limiting factor. This paper describes a simulated model for an incoherent Gigabit OCDMA system using high performance W/T codes. 60 km fiber amplifier span has been used in this model. Earlier work has been done at 1.25 Gbps for 16 users. In this paper OCDMA system beyond 1.25 Gbps is suggested by redesigning W/T code using 8-wavelength and 8-time slots. By using modified W/T code the MAI reduces. The analysis takes into account the effect of data rates for increasing number of simultaneous users and received power. The system performance is evaluated by eye diagram and BER analysis at different data rates. The system has been designed for 1 Gbps, 1.25 Gbps, 2.5 Gbps and 5 Gbps. BER analysis for asynchronous concurrent communication of multiple users at different data rates has been done. Results show that the Bit-Error-Rate performance for 1.25 Gbps improves in comparison to previous designs. The designed system provides adequate BER (<10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> ) for 2.5 Gbps up to 16 users and for 5 Gbps up to 8 users.