R. Avó

Regenerative memory in time-delayed neuromorphic photonic resonators

We investigate a photonic regenerative memory based upon a neuromorphic oscillator with a delayed self-feedback (autaptic) connection. We disclose the existence of a unique temporal response characteristic of localized structures enabling an ideal support for bits in an optical buffer memory for storage and reshaping of data information. We link our experimental implementation, based upon a nanoscale nonlinear resonant tunneling diode driving a laser, to the paradigm of neuronal activity, the FitzHugh-Nagumo model with delayed feedback. This proof-of-concept photonic regenerative memory might constitute a building block for a new class of neuron-inspired photonic memories that can handle high bit-rate optical signals.

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.

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.

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.

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

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 up-conversion 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.

Simulation of mm-wave over fiber employing optical single sideband modulation combined with subcarrier multiplexing

Access infrastructures combining fiber optic and wireless technologies can provide the necessary broadband access required by the convergence of wireless and wired networks. In this paper we discuss a mm-wave radio over fiber (RoF) optical access network architecture, which combines radio subcarrier multiplexing techniques to improve system efficiency with fiber dispersion mitigation provided by optical single sideband modulation techniques. The RoF access network is discussed and analyzed through simulation.

A Signaling Architecture for Consumer Oriented Grids Based on Optical Burst Switching

This paper presents a signaling architecture for consumer oriented photonic grids. We propose to decrease the end-to-end transmission job delay, by exploring the potential of advanced grid network architectures based on active optical burst switching and active routers. The proposed scheme is discussed in detail and it is shown that conceptually it performs always better than the conventional just enough time (JET) signaling protocol.

Comparative study of optical up-conversion schemes

Optical mm-wave signal generation and up-conversion using external modulation of an optical carrier by means of LiNbO3 Mach-Zehnder (MZ) modulators have proven to be reliable approaches due to the frequency range, excellent system stability, and high spectral purity of the generated signal. The objective of this paper is to compare the performance of different up-conversion strategies in terms of complexity, stability and robustness against dispersion. The comparative study presented here considers practical impairments such as the finite extinction ratio of Mach-Zehnder modulators and the noise added by optical amplifiers.