The recent remarkable growth in bandwidth of both wired optical and wireless access
networks supports a burst of new high bandwidth Internet applications such as: peer-topeer
file sharing, cloud storage, on-line gaming, video streaming, etc. Within this
scenario, the convergence of fixed and wireless access networks offers significant
opportunities for network operators to satisfy user demands, and simultaneously reduce
the cost of implementing and running separated wireless and wired networks.
The integration of wired and wireless network can be accomplished within several
scenarios and at several levels. In this thesis we will focus on converged radio over fiber
architectures, particularly on two application scenarios: converged optical 60 GHz
wireless networks and wireless overlay backhauling over bidirectional colorless
wavelength division multiplexing passive optical networks (WDM-PONs).
In the first application scenario, optical 60 GHz signal generation using external
modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder
modulators (MZM) is considered. The performance of different optical modulation
techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies
are identified. The study is extended to 60 GHz carriers digitally modulated with data and
to systems employing subcarrier multiplexed (SCM) mm-wave channels.
In the second application scenario, the performance of WDM-PONs employing
reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal
frequency-division multiplexing (OFDM) wireless signal is assessed analytically and
experimentally, with the relevant system impairments being identified. It is demonstrated
that the intermodulation due to the beating of the baseband signal and wireless signal at
the receiver can seriously impair the wireless channel. Performance degradation of the
wireless channel caused by the RSOA gain modulation owing to the downstream
baseband data is also assessed, and system design guidelines are provided.Universidade do Algarve, Faculdade de Ciências e Tecnologi