Simulation of mm-wave over fiber systems employing up-conversion using external modulators

Abstract

Access infrastructure combining fiber optic and wireless technologies can provide the necessary broadband access required by convergence of wireless and wired networks. Optical millimetter-wave generation using upconversion is considered as a cost-effective solution in radio over fiber systems. In this paper we discuss and compare the robustness against dispersion of three millimetter-wave generation techniques based on upconversion. Keywords: multi-gigabit indoor Wireless Personal Area Networking (WPAN), mm-wave networks, radio over fiber, all-optical up-conversion, optical single side-band, optical carrier suppression, optical double side-band. INTRODUCTIONThe 60 GHz (mm-wave) band as been allocated worldwide for short range wireless communications due to its inherent high propagation losses. The abundant unlicensed spectrum around 60 GHz have the potential to support consumer demands for indoor wireless applications that require high bandwidth such as real time streaming content download for high-definition TV, wireless gigabit Ethernet, etc. These applications cannot be supported over existing home networking solutions (IEEE 802.111 a/b/g) because the required data rates far exceed their capabilities. The recent advances reported in low cost production CMOS components and circuits operating at 60 GHz combined with the increasing consumer demands for wireless high speed applications have lead to a boost in research and to standardization, such as in IEEE 802.15.3c working group. However, the 60 GHz wireless systems require a large number of base stations (BSs) to cover a service area. This requirement has led to the development of system architectures where functions such as signal/routing/processing, handover and frequency allocation are carried out at the central office (CO). The best solution for linking the central station (CS) with BSs in such radio network is via an optical fiber network, commonly dominated radio over fiber (RoF) network [1]. By exploiting high-bandwidth wavelength-division multiplexing (WDM) networks, an integrated fiber radio backbone network could be developed to interconnect antenna base station with the CO. The mm-wave carrier is modulated with data and placed on a particular wavelength channel to be delivered to a designed BS. The generation and transmission of optical mm-wave are crucial issues in these systems, which are being widely researched. Several techniques have been proposed to generate mm-wave optical signal. Among them, optical frequency up-conversion has potential to provide a simple and cost efficient solution [2,3]. The principle of optical frequency up-conversion is to generate optically high-order optical harmonics using an external nonlinear modulator, typically a Mach-Zehnder modulator (MZM) driven by a low frequency electrical signal. The efficiency of this technique depends not only on its capacity to maximize the required high-order harmonic but also on its robustness against fiber dispersion. Therefore the objective of this paper is to compare in terms of fib...