Direct and External Intensity Modulation in OFDM RoF Links

Pavlos I Lazaridis,Sinan A Khwandah,John P Cosmas,Ian A Glover,Zaharias D Zaharis,Neeli R Prasad

doi:10.1109/jphot.2015.2456499

Abstract

Radio-over-fiber (RoF) systems comprise light modulation and transmission of millimeter-wave signals over fiber links. The aim of this study is to investigate the performance of external and direct intensity modulation in RoF links and to analyze the drawbacks induced by different components of the optical system. In external modulation, the Mach-Zehnder modulator (MZM) is used, whereas the vertical-cavity surface-emitting laser (VCSEL) is utilized in direct modulation. Both modulation schemes are tested for a vector modulation format, i.e., the quadrature amplitude modulation (QAM), where an orthogonal frequency-division multiplexing (OFDM) scheme is used to generate signal subcarriers. The simulations are carried out with the same values of common global parameters for both schemes of intensity modulation. Although VCSEL is a promising device for future RoF systems, the external modulation shows a more robust performance compared with that of VCSEL when implemented with the OFDM modulation technique.

Highlights

There has been a remarkable growth in the deployment of analog optical links due to their capabilities and advantages for a wide range of applications such as antenna remoting, radio over fiber (RoF), and optical signal processing [1]
The aim of this study is to investigate the performance of external and direct intensity modulation in RoF links and to analyze the drawbacks induced by different components of the optical system
vertical-cavity surface-emitting laser (VCSEL) is a promising device for future RoF systems, the external modulation shows a more robust performance compared with that of VCSEL when implemented with the orthogonal frequency-division multiplexing (OFDM) modulation technique

Summary

Introduction

There has been a remarkable growth in the deployment of analog optical links due to their capabilities and advantages for a wide range of applications such as antenna remoting, radio over fiber (RoF), and optical signal processing [1]. The new wavelength division multiplexing (WDM) technology enables large capacities of tens of terabits per second (Tbps) using a single fiber line [2]. This has made optical networks more flexible and able to meet high data rate demands for broadband services, which require more spectral bandwidth and higher frequencies, in the range of Gigabits per second (Gbps). Recent research has focused on enhancing the performance of opto-electric links, and on finding a solution to overcome existing limitations and impairments, which occur throughout the link and degrade the performance of the main processes.

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