Showing papers by "Antonio Mecozzi published in 2023"

A Field Trial of Multi-Homodyne Coherent Detection Over Multi-Core Fiber for Encryption and Steganography

Abstract: The concept of multi-homodyne coherent detection is used for stealth and secured optical communications, demonstrating a transmission rate of 20 Gbps under negative (in dB) optical signal-to-noise ratio (OSNR), in a deployed multi-core fiber (MCF) network. A 10 GBd QPSK signal is assigned with a bandwidth of multi-hundreds GHz, optically encoded with spectral phase mask, and transmitted below ASE noise in the MCF channel. To enable such transmission scheme, a semiconductor based gain-switched laser (GSL) frequency comb, used as both the signal carrier and local oscillator (LO), are then mixed in intradyne coherent receiver. The ultra-short time-domain overlapping between the pulsed signal and the pulsed LO allows the authorized user to collect the information, while discriminating most of the noise. Consequently, the electrical SNR is dramatically improved compared to the optical SNR, resulting in optical processing gain. Nevertheless, ultra-short pulses mixing is rather susceptible to a chromatic dispersion (CD), which imposes a major challenge in this spread-spectrum transmission technique. In this contribution, the effect of CD in multi-homodyne coherent detection is analyzed in an analytic model and in experiments. The model suggests a modified CD transfer function, comprised of the optical sampling of a conventional CD transfer function. In addition, the SNR penalty associated with the CD effect is quantified, as well as its dependency in propagation length and overall GSL's bandwidth. To circumvent the devastating effect of the CD, multi-core fibers are proposed. Two different weakly-coupled cores of a homogeneous MCF allow the signal and the LO to co-propagate through a very similar dispersive channel. A field trial in a deployed 6.29 km MCF network has validated an encrypted and stealthy 20 Gbps coherent transmission, at −2 dB OSNR.

Coherent combination method applied to distributed acoustic sensing over deployed multicore fiber

Abstract: From Distributed Acoustic Sensing (DAS) measurements over deployed Multi-Core Fiber (MCF), we discuss several signal processing options to enhance the sensing sensitivity, namely core combination and longitudinal averaging.

Dependence of nonlinear interference on mode dispersion and modulation format in strongly-coupled SDM transmissions.

Abstract: We study the role of the modulation format in the interaction between mode dispersion and the fiber nonlinear interference (NLI) in space-division multiplexed (SDM) systems with strongly-coupled spatial modes. We show that the interplay between mode dispersion and the modulation format has a significant impact on the magnitude of cross-phase modulation (XPM). We propose a simple formula that accounts for the modulation-format dependence of the XPM variance in the presence of arbitrary levels of mode dispersion, thus extending the ergodic Gaussian noise model.

Deep Learning-Based Phase Retrieval Scheme for Minimum-Phase Signal Recovery

Abstract: We propose a deep learning-based phase retrieval method to accurately reconstruct the optical field of a single-sideband minimum-phase signal from the directly detected intensity waveform. Our method relies on a fully convolutional Neural Network (NN) model to realize non-iterative and robust phase retrieval. The NN is trained so that it performs full-field reconstruction and jointly compensates for transmission impairments. Compared to the recently proposed Kramers-Kronig (KK) receiver, our method avoids the distortions introduced by the nonlinear operations involved in the KK phase-retrieval algorithm and hence does not require digital upsampling. We validate the proposed phase-retrieval method by means of extensive numerical simulations in relevant system settings, and we compare the performance of the proposed scheme with the conventional KK receiver operated with a 4-fold digital upsampling. The results show that the 7% hard-decision forward error correction (HD-FEC) threshold at BER 3.8e-3 can be achieved with up to 2.8 dB lower carrier-to-signal power ratio (CSPR) value and 1.8 dB better receiver sensitivity compared to the conventional 4-fold upsampled KK receiver. We also present a comparative analysis of the complexity of the proposed scheme with that of the KK receiver, showing that the proposed scheme can achieve the 7% HD-FEC threshold with 1.6 dB lower CSPR, 0.4 dB better receiver sensitivity, and 36% lower complexity.

Field Trial of High-Resolution Distributed Fiber Sensing over Multicore Fiber in Metropolitan Area with Construction Work Detection using Advanced MIMO-DAS

Abstract: We demonstrate a successful field trial of MIMO-DAS over multicore fiber (MCF) allowing for accurate localization of acoustic events in the city of L’Aquila, Italy. We show a 2m spatial resolution and 1mHz-380Hz acoustic bandwidth.

Fiber signature-domain multiplexing for high-speed shape sensing

Abstract: This paper introduces a novel method to simultaneously measure the cores of a multi-core fiber, enabling higher acquisition rates in shape sensing. The two-dimensional shape of the optical fiber is determined from the distributed strain measurements performed with the optical frequency domain reflectometry technique.

Partial MIMO-based Mode Division Multiplexing Transmission over the First Field-Deployed 15-Mode Fiber in Metro Scenario

Abstract: We assess mode division multiplexing transmission based on partial MIMO equalization over 6.1 km of the first deployed 15-mode fiber in L’Aquila, Italy. We demonstrate more than 13Tb/s throughput with reduced receiver DSP resources.

Colorless and Directionless ROADM for Meshed Coupled-Core Multicore Fiber Networks

Abstract: We demonstrate the first meshed spatial-super-channel switching SDM network using field-deployed coupled-core multicore fibers with a 3 line-side, colorless, directionless ROADM. We evaluate 19 network scenarios including add&drop, bypass and grooming with 2 Tb/s granularity.

Demonstration of Multi-Hop Mode-Group Routing in a Field-Deployed Multi-Mode Fiber Network

Abstract: Space-division multiplexing can enhance node flexibility in urban networks by exploiting routing of weakly coupled mode groups. We demonstrate multi-hop Tb/s group routing in different switching scenarios in the deployed 15-mode fiber-ring in L’Aquila, Italy.

Use of Optical Coherent Detection for Environmental Sensing

Abstract: We discuss the use of the fiber channel transfer matrix extracted from a digital coherent receiver for environmental sensing. We show that the polarization rotation vector describing the unitary part of the matrix is highly sensitive to perturbations affecting the optical fiber link. This vector can be readily extracted from the time-dependent transfer matrix reconstructed by the coherent receiver during system operation and may serve as an effective observable to monitor environmental changes.

Mode-Group-Division Multiplexing over a Deployed 15-Mode-Fiber Cable

Abstract: We experimentally demonstrate transmission over a subset of up to 4 spatial modes of a deployed 15-mode Graded-index Fiber Cable.