Coherent Optical DFT-Spread OFDM

Fanggang Wang,Xiaodong Wang

doi:10.1155/2011/689289

Abstract

We consider application of the discrete Fourier transform-spread orthogonal frequency-division multiplexing (DFT-spread OFDM) technique to high-speed fiber optic communications. The DFT-spread OFDM is a form of single-carrier technique that possesses almost all advantages of the multicarrier OFDM technique (such as high spectral efficiency, flexible bandwidth allocation, low sampling rate, and low-complexity equalization). In particular, we consider the optical DFT-spread OFDM system with polarization division multiplexing (PDM) that employs a tone-by-tone linear minimum mean square error (MMSE) equalizer. We show that such a system offers a much lower peak-to-average power ratio (PAPR) performance as well as better bit error rate (BER) performance compared with the optical OFDM system that employs amplitude clipping.

Highlights

The high-throughput data transmission over long-haul fiber optic systems is of considerable current interest
The orthogonal frequency-division multiplexing (OFDM) technique has been widely adopted to cope with the frequency-selective fading of multipath channels in wireless communications, and it has been recently introduced to fiber optic systems for high-speed data transmission [2]
A long-haul fiber optic system is considered with nE = 12 cascaded spans

Summary

Introduction

The high-throughput data transmission over long-haul fiber optic systems is of considerable current interest. To maximize the spectral efficiency, polarization multiplexing and coherent detection have become the key enabling technologies for high-speed fiber optic communication systems [1]. Physical impairments such as the chromatic dispersion (CD), the polarization mode dispersion (PMD), and the polarization dependent loss (PDL) become more severe as the bandwidth and data rate increase. The orthogonal frequency-division multiplexing (OFDM) technique has been widely adopted to cope with the frequency-selective fading of multipath channels in wireless communications, and it has been recently introduced to fiber optic systems for high-speed data transmission [2].

The Coherent Optical DFT-Spread OFDM System with PDM

The Linear MMSE Coherent Receiver

Simulation Results

Conclusions