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Elie Awwad

Publications and source records attributed to Elie Awwad.

8 recordsLinked to original sources
arXiv2026

Analog-to-digital conversion in the quantum regime

Digital signal processing has become essential in quantum optics, particularly for continuous-variable (CV) information encoding, enabling coherent detection schemes and mitigation of linear impairments. While linear signal processing in double homodyne detection has been studied under the assumption that all post-measurement processing can be backpropagated in the optical domain, a rigorous treatment of the digitization chain, spanning optical, electronic, and sampling stages, is still lacking. In this work, we consider the continuous mode description of double homodyne detection to fully capture the maximum mode-matching coefficient achievable as a function of electronic noise, signal bandwidth, receiver electronics bandwidth, and sampling rate, that is the entry point of digital signal processing. We establish a dimensioning rule that generalizes the Nyquist-Shannon criterion to account for quantum fluctuations of the measured signal, not merely its bandwidth. Analyzing the case of additive white electronic noise, we find numerically that optimal signal-to-noise ratio is achieved when the electronic bandwidth is large enough to pass the signal yet narrower than the sampling rate in order to mitigate noise amplification, yielding a concrete design criterion for coherent detection.

quant-ph↗
arXiv2026

Comparative Analysis of Spread-Spectrum Codes for Fibre-Optic Distributed Acoustic Sensing

This paper presents a comprehensive performance comparison of several coded sequences for distributed acoustic sensing systems through numerical simulations. Correlation analysis reveals that perfect autocorrelation sequences provide accurate channel estimation. Phase noise sensitivity varies significantly with frequency diversity, with high-diversity sequences maintaining lower estimation errors for phase and intensity despite increased laser linewidths. For a coded distributed acoustic sensing system with \qty{10}{\hertz} laser linewidth, high-diversity sequences achieve $2.7\times10^{-3}$ rad phase error compared to $5.3\times10^{-3}$ rad for low-diversity codes for a \qty{1.5}{\kilo\meter} fibre length. The findings establish performance trade-offs between correlation quality, phase noise resilience, and practical implementation constraints for next-generation fibre-optic distributed acoustic sensing systems.

eess.SP↗
arXiv2026

Numerical Model of a Multiple-Input-Multiple-Output Distributed Acoustic Sensing System with Joint Phase and Birefringence Estimation

In this work, we introduce and experimentally validate a numerical model for a Multiple-Input-Multiple-Output Distributed Acoustic Sensing (MIMO-DAS) system that accounts for dynamic perturbations of fiber birefringence and of the common optical phase of the backscattered signal (or polarization-averaged phase, shared by both polarization tributaries). The MIMO-DAS system probes the fiber using polarization-multiplexed constant-power coded sequences that are suited for coexistence of DAS with WDM data transmission over the same fiber. We study the effect of both axisymmetric and anisotropic events on the two quantities. We demonstrate, through numerical simulations and lab experiments, the estimation of effective birefringence magnitude in static conditions, and the joint estimation of common phase and effective birefringence magnitude in the case of dynamic longitudinal strain and anisotropic transverse strain. This allows for event discrimination and increased sensitivity to disturbances that act transversely on the fiber, since polarization will be responsive to perturbations that break cylindrical symmetry, while the phase will strongly respond to longitudinal strain.

eess.SP↗
arXiv2020

Introducing Coherent MIMO Sensing, a fading-resilient, polarization-independent approach to phase-OTDR

Nowadays, long distance optical fibre transmission systems use polarization diversity multiplexed signals to enhance transmission performance. Distributed acoustic sensors (DAS) use the same propagation medium ie. single mode optical fibre, and aims at comparable targets such as covering the highest distance with the best signal quality. In the case of sensors, a noiseless transmission enables to monitor a large quantity of mechanical events along the fibre. This paper aims at extending the perspectives of DAS systems with regard to technology breakthroughs introduced in long haul transmission systems over the last decade. We recently developed a sensor interrogation method based on coherent phase-sensitive optical time domain reflectometry ($ϕ$-OTDR), with dual polarization multiplexing at the transmitter and polarization diversity at the receiver. We name this technique Coherent-MIMO sensing. A study is performed from a dual-polarization numerical model to compare several sensor interrogation techniques, including Coherent-MIMO. We demonstrate that dual-polarization probing of a fibre sensor makes it insensitive to polarization effects, decreases the risks of false alarms and thus strongly enhances its sensitivity. The simulations results are validated with an experiment, and finally quantitative data are given on the performance increase enabled by Coherent-MIMO sensing.

eess.SP↗
arXiv2019

High Sensitivity ϕ-OTDR over Long Distance with Polarization Multiplexed Codes

Newly introduced polarization diversity probing codes are suggested to enhance the sensitivity and bandwidth performance of differential phase-sensitive distributed OTDR systems. This was recently demonstrated by means of short-length specialized fibers with a backscattering induced by equally spaced Fiber Bragg Gratings inserted in the fiber itself. The work summarized in this letter aims to extend the polarization-diversity probing technique to widely spread standard single mode fibers (SSMF) used for telecommunications, by solely exploiting the Rayleigh backscattering. Conditions to achieve perfect phase estimation along such fibers are first detailed. An experimental validation highlights the ability to detect and localize, over 25km of SSMF, multiple low-energy perturbations within a 475Hz-bandwidth.

eess.SP↗
arXiv2018

Enhancing performance of coherent OTDR systems with polarization diversity complementary codes

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent phase-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

eess.SP↗