Transmission performance of adaptively modulated optical OFDM signals in multimode fiber links

A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) is proposed and numerical simulations of the transmission performance of AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback lasers (DMLs). It is shown that 28 Gb/s intensity modulation and direct-detection AMOOFDM signal transmission over 300-m MMFs is feasible in unamplified DML-based links having 3-dB bandwidths of 150MHz/km. In addition, AMOOFDM is less susceptible to modal dispersion and variation in launching conditions when compared with existing schemes.

I. Introduction

Most installed Ethernet backbones based on multimode fibers (MMFs) operate at bit rates of about 1Gb/s, which is inadequate for current and emerging demand. Great effort has been expended on exploring cost-effective solutions for upgrading 1-Gb/s Ethernet backbones to 10Gb/s [1], [2]. Enterprise customers wishing to upgrade their backbones prefer to use installed MMFs rather than pull new fibers, as significant cost savings can be achieved. However, installed MMF links exhibit considerable bandwidth variation, which range from 200–2600 MHz/km with 17% being even less than the minimum 3-dB bandwidth of 500 MHz/km specified by ISO/IEC 11801 [3]. In addition, the 3-dB bandwidth is also very sensitive to different launching conditions including central, small offset, and conventional offset launching [4].