Paula Laurêncio

Dynamic range of optical links employing optical single side-band modulation

The dynamic range of optical single side-band modulated systems is analyzed for both small-signal and large-signal regimes. Under small-signal conditions the achievable link bandwidth is mainly limited by the combined effect of fiber nonlinearities and fiber dispersion. Whereas, under large-signal regime, the sidebands of the optical field at harmonics of the modulation frequency become significant, and the link bandwidth is limited by the interaction between the different optical field harmonics affected by different phase changes due to the fiber dispersion.

Impact of the Combined Effect of RIN and Intermodulation Distortion on OSSB/SCM Systems

This paper investigates both theoretically and numerically the performance limitations due to the combined effect of relative intensity noise (RIN) and intermodulation distortion of broadband optical single sideband/subcarrier multiplexing (OSSB/SCM) systems. The analysis includes intermodulation distortion combined with RIN introduced by the laser source and by optical preamplification. System performance is evaluated in terms of bit error rate for SCM systems using optically preamplified receivers, and a comparison is made between different modulation schemes applied to the individual channels. The authors demonstrate that depending on optical carrier suppression factor, modulation index, modulation format, fiber length, channel spacing, optical input power, and carrier frequency, the system performance may be predominantly affect by the RIN or by the intermodulation distortion

Radio over fiber access network architecture employing reflective semiconductor optical amplifiers

This paper introduces the RoFnet-Reconfigurable Radio over Fiber network, which is a project supported by the Portuguese Foundation for Science and Technology. This project proposes an innovative radio over fiber optical access network architecture, which combines a low cost Base Station (BS) design, incorporating reflective semiconductor optical amplifiers, with fiber dispersion mitigation provided by optical single sideband modulation techniques. Optical wavelength division multiplexing (WDM) techniques are used to simplify the access network architecture allowing for different Base Stations to be fed by a common fiber. Different wavelength channels can be allocated to different BSs depending on user requirements. Additionally, in order to improve radio coverage within a cell, it is considered a sectorized antenna interface. The combination of subcarrier multiplexing (SCM) with WDM, further simplifies the network architecture, by using a specific wavelength channel to feed an individual BS and different subcarriers to drive the individual antenna sectors within the BS.

Optical frequency tripling with improved suppression and sideband selection

A novel, optical dispersion tolerant millimetre-wave radio-over-fibre system using optical frequency tripling technique with enhanced and selectable sideband suppression is demonstrated. 3 dB RCE penalties for multichannel WiMax transport was recorded after 40 km of fibre.

Generation and transmission of millimeter wave signals employing optical frequency quadrupling

Access infrastructure combining fiber optic and millimeter-wave wireless technologies can provide the necessary broadband access required by convergence of wireless and wired networks. Optical millimetre-wave generation using upconversion is considered a cost-effective solution in radio over fiber systems. In this paper we propose a frequency multiplication technique using two Mach-Zehnder in parallel. The generated optical signal is single sideband which minimizes fiber dispersion impairments. The attainable transmission distance is assessed for 2.5 Gbit/s data rate.

Relative Intensity Noise in Optical Single Side Band Systems with Multiple In-Line Amplifiers : Analysis and Validation

Abstract This article analyzes and validates through simulation the influence of fiber nonlinearity, dispersion, and loss on the Relative Noise Intensity (RIN) spectrum at fiber output in externally modulated optical single side band (OSSB) systems. The analysis includes the RIN generated by the laser source, the effect of the OSSB modulator, and noise generated by the in-line optical amplifiers. The analysis takes into account conversion between phase noise and intensity noise introduced by fiber transmission. It is shown that, depending on the operating conditions, the system performance may be predominantly affected either by the laser RIN or by the noise generated by the in-line optical amplifiers. The impact of the OSSB modulator can be relevant when the RIN of the system is dominated by the laser noise and should therefore be considered.

Transmission limitations of WiMax over fibre transmission employing optical up-conversion schemes

WiMax is a promising technology for the delivery of last mile wireless broadband access which when combined with fibre access networks can provide cost effective solution for next generation integrated networks. WiMax fibre transmission employing up-conversion techniques by means of external modulation of an optical carrier by LiNbO3 Mach-Zehnder (MZ) modulators has proven to be a reliable approach. However, robustness of such techniques against dispersion is impaired by the finite extinction ratio (ER) encountered in commercially available MZMs which is typically 20-35 dB. This paper analyses through simulation the effect of the ER on the transmission over optical fibre of up-converted WiMax signals emphasizing the importance of configurations able to compensate the finite extinction ratio of commercially available MZ modulators.

Dispersion Robustness of Millimeter Waves Generated by Up-Conversion Strategies

Abstract The performance degradation caused by transmission along dispersive single-mode fibers of optically generated millimeter-wave signals using up-conversion is theoretically assessed and validated by numerical simulation. Up-conversion techniques based on optical double sideband, optical single sideband, and optical carrier suppression are considered. The generation of 60 GHz by frequency tripling using the optical single sideband is shown to be particularly tolerant to the fiber dispersion. The practical imbalance of Mach-Zehnder modulators is taken into account for optical carrier suppression modulation, where the finite extinction ratio is found to increase tolerance to fiber dispersion.

60 GHz radio-over-fiber transmission impairments for broadband wireless signals

The recent advances reported in low cost production 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 of millimeter-wave (mm-wave) systems and networks operating in the 60 GHz region. The abundant unlicensed spectrum around 60 GHz have the potential to support consumer demands that require high bandwidth such as real time streaming content download for high-definition TV, wireless gigabit Ethernet, etc. In this paper we will considerer the optical transmission limitations of digitally modulated 60 GHz carriers, considering different optical modulation techniques. The attainable transmission distance will be discussed in terms of system operating conditions.

Convergence of optical and millimeter-wave broadband wireless access networks

This paper discusses hybrid fiber optic access network architectures combining baseband wireline and mm-wave channels. We focus on mm-wave radio over fiber (RoF) optical access network architectures which combine radio subcarrier multiplexing techniques to improve system efficiency with fiber dispersion mitigation provided by optical single sideband modulation techniques. Besides discussing the network architecture we focus on the intermodulation effects arising from the nonlinear characteristics of the optical modulator and the reflective semiconductor optical amplifier.