A Single Laser and Fiber Based Duplex Data Transmission to Multiple Users in a Passive Optical Link

Abstract

A passive optical link for duplex data transmission operating at 20 Gb/s is designed using a single laser and fiber. A transmission distance of 55km is achieved by providing a cost efficient design with a low complexity by utilizing wavelength conversion technique which allows us to reuse the downlink signal for the uplink transmission over the same transmission fiber using different wavelengths as well as eliminating the need for a separate laser at the user end. The wavelength converter used is designed by utilizing the Self Phase Modulation properties of a Hightly Nonlinear Fiber of length of 1 km. The simulation setup consists of a downlink signal from two users modulated with DP-QPSK format operating at 1552 nm having a total bitrate of 20 Gb/s. Two different wavelengths 1550.2 nm and 1553.8 nm are generated from the downlink signal by using HNLF based Wavelength Converter. The uplink data from two users each having a bit rate of 10 Gbps is modulated on these two wavelength converted signals using OOK modulation and added together to send back over the same 55km fiber. The simulation setup and results are provided. BER curves and eye diagrams of the received uplink and downlink signal over a duplex transmission single fiber link are provided.