Personne :
LaRochelle, Sophie

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Adresse électronique
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Université Laval. Département de génie électrique et de génie informatique
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Voici les éléments 1 - 10 sur 61
  • Publication
    Improvement of vertical GPS precision with a GPS-over-fiber architecture and real-time relative delay calibration
    (John Wiley & Sons, 2011-11-09) Santerre, Rock; Macias-Valadez, Daniel; LaRochelle, Sophie; Landry, René Jr.
    A limitation of GPS positioning is that the vertical component is generally two to three times less precise than the horizontal components. In a previous work by R. Santerre of Laval University and G. Beutler of University of Bern, it was shown in simulations that it is possible to improve the GPS vertical positioning precision by using a multi-antenna GPS receiver and a precise calibration technique of the relative hardware delay between the antennas and the receiver. However, no actual implementation of the system was done to prove the concept until now. A new multi-antenna, GPS-over-fiber architecture with real-time delay monitoring, designed and implemented to improve the vertical precision is presented. The improvement in vertical precision arises from the elimination of the relative receiver clock error in single difference, between antennas, and the precision real-time calibration of the relative hardware delay. Experiments were conducted with a zero baseline and a short baseline configuration. The results show, as expected by the theory and the simulations, a two to three times improvement in the precision of the vertical component such that it reached the same level of performance as the horizontal components. These promising results will enable the use of this type of configuration in several applications where the same precision in all 3D components is essential and could not be achieved before with standard GPS positioning techniques.
  • Publication
    Accès libre
    Semiconductor optical amplifier based wavelength conversion of Nyquist-16QAM for flex-grid optical networks
    (Institute of Electrical and Electronics Engineers, 2016-06-01) Lin, Jiachuan; Filion, Benoît; LaRochelle, Sophie; Zhang, Xiaoguang; Rusch, Leslie; Nguyen, An T.
    We experimentally demonstrate semiconductor opti-cal amplifier (SOA) based wavelength conversion of 3×25 Gbaud Nyquist-16QAM signal for a flex-grid network. The conversion efficiency and power penalty of each of three channels during sin-gle pumped SOA wavelength conversion are studied with respect to three different channel spacings (or frequency grids). The BER performance of all converted channels fall below the FEC thresh-old of 3.8e-3, even with a 50 GHz grid. The results show the trade-off between channel spacing, conversion efficiency and BER power penalty. Closely packed channels, which clearly increase spectral efficiency, are also shown to decrease conversion power penalty, potentially counter balancing increased crosstalk levels. These re-sults can be used to optimize routing and spectrum allocation strategy when SOA wavelength converter(s) are present in the optical link.
  • Publication
    Accès libre
    Mode division multiplexing using orbital angular momentum modes over 1.4 km ring core fiber
    (Institute of Electrical and Electronics Engineers, 2016-07-27) Mirzaei Nejad, Reza; Amiralizadeh, Siamak; Brunet, Charles; LaRochelle, Sophie; Messaddeq, Younès; Allahverdyan, Karen; Rusch, Leslie; Vaity, Pravin
    Mode division multiplexing (MDM) systems using orbital angular momentum (OAM) modes can recover the data in D different modes without recourse to full (2D × 2D) multiple input multiple output (MIMO) processing. One of the biggest challenges in OAM-MDM systems is the mode instability following fiber propagation. Previously, MIMO-free OAM-MDM data transmission with two modes over 1.1 km of vortex fiber was demonstrated, where optical polarization demultiplexing was employed in the setup. We demonstrate MDM data transmission using two OAM modes over 1.4 km of a specially designed ring core fiber without using full MIMO processing or optical polarization demultiplexing. We demonstrate reception with electrical polarization demultiplexing, i.e., minimal 2 × 2 MIMO, showing the compatibility of OAM-MDM with current polarization demultiplexing receivers.
  • Publication
    Accès libre
    Orbital-angular-momentum polarization mode dispersion in optical fibers
    (Institute of Electrical and Electronics Engineers, 2016-04-15) LaRochelle, Sophie; Messaddeq, Younès; Chatigny, Stephane; Wang, Lixian; Rusch, Leslie; Vaity, Pravin
    The orbital-angular-momentum (OAM) modes in optical fibers have polarization mode dispersion (PMD) properties similar to those of single-mode fibers (SMFs). The +l and -l order OAM modes supported by the same fiber vector modes undergo random cross coupling and exhibit a frequency-dependent time delay. We name this effect “OAM-PMD” and extend the formalism developed for PMD in SMFs to describe OAM-PMD. The characteristics of the modal beat lengths, birefringence correlation lengths, and the mean value of OAM-PMD are investigated. A fixed-analyzer technique is proposed and demonstrated to characterize this phenomenon in OAM fibers. Two different types of OAM fiber are examined. The measured results are compared with the theoretical calculations.
  • Publication
    Accès libre
    Post-compensation of nonlinear distortions of 64-QAM signals in a semiconductor based wavelength converter
    (Institute of Electrical and Electronics Engineers., 2016-08-01) Filion, Benoît; LaRochelle, Sophie; Rusch, Leslie; Nguyen, An T.
    We experimentally investigate post-compensation of nonlinear distortions induced by a wavelength converter (WC) based on four-wave mixing in a semiconductor optical amplifier. The technique exploits a low-complexity digital filter-based back-propagation (DFBP) method. We perform post-compensation of nonlinear distortions following single stage wavelength conversion of 5 Gbaud 64- quadrature amplitude modulation (QAM). We examine the DFBP performances in the presence of a degraded optical signal-to-noise ratio at the WC input and we explore the WC optimal operating conditions. Also, we experimentally demonstrate for the first time in the literature dual stage wavelength conversion of QAM signals, in particular, 5 Gbaud 64-QAM, and show that bit error rate below hard-decision forward error correction threshold is only possible with post-compensation of nonlinear distortions. These results are of importance for the development of wavelength routed networks requiring successive wavelength conversion stages to enhance routing capabilities.
  • Publication
    Accès libre
    Dual phase-shift Bragg grating silicon photonic modulator operating up to 60 Gb/s
    (Optical Society of America, 2016-01-29) Simard, Alexandre D.; Bédard, Keven; Filion, Benoît; Painchaud, Yves; LaRochelle, Sophie; Rusch, Leslie
    We demonstrate PAM-4 and OOK operation of a novel silicon photonic modulator. The modulator design is based on two phase-shifts in a Bragg Grating structure driven in a push pull configuration. Back-to-back PAM-4 modulation is demonstrated below the FEC threshold at up to 60 Gb/s. OOK modulation is also shown up to 55 Gb/s with MMSE equalization and up to 50 Gb/s without equalization. Eye diagrams and BER curves at different bit rates are provided for both PAM-4 and OOK modulations. To our knowledge, this structure is the fastest silicon photonic modulator based on Bragg gratings, reaching modulation speed comparable to the fastest Mach-Zehnder modulators and micro-ring modulators.
  • Publication
    Accès libre
    Silicon photonic modulator using mode conversion with asymmetric sidewall bragg gratings
    (IEEE, 2018-10-04) Jafari, Omid; LaRochelle, Sophie; Shi, Wei
    An asymmetric sidewall grating allows to operate a Bragg modulator in reflection without circulator and with less than 1.5 dB on-chip loss. An asymmetric Y-branch directs the incident TE0 mode to the grating, while the reflected TE1 mode is guided to the drop port.
  • Publication
    Accès libre
    Demonstration of an erbium-doped fiber with annular doping for low gain compression in cladding-pumped amplifiers
    (The Optical Society, 2018-10-01) Essiambre, René-Jean.; Chen, Haoshuo; Matte-Breton, Charles; Fontaine, Nicolas K.; Jin, Cang; Ryf, Roland; LaRochelle, Sophie; Messaddeq, Younès; Kelly, C.
    We present the design and characterization of a cladding-pumped amplifier with erbium doping located in an annular region near the core. This erbium-doped fiber is proposed to reduce gain saturation, leading to smaller gain compression when compared to uniform core doping. Through numerical simulations, we first compare the performance of three fibers with different erbium doping profiles in the core or the cladding. When the doped fibers are operated at the optimum length, results show that the smaller overlap of the signal mode field with the annular erbium doping region leads to higher gain and lower saturation of the amplifier. A single-core erbium-doped fiber with an annular doping and a D-shaped cladding was fabricated. Measurements demonstrate less than 4 dB of gain compression over the C-band for input power ranging from −40 dBm to 3 dBm. Small gain compression EDFAs are of interest for applications that require input channel reconfiguration. Higher gain and saturation output power are also key issues in cladding-pumped multi-core amplifiers.
  • Publication
    Accès libre
    Demonstration and evaluation of an optimized RFS comb for terabit flexible optical networks
    (Optical Society of America, 2017-09-20) Lin, Jiachuan; LaRochelle, Sophie; Lyu, Mingyang; Wang, Lixian; Pai, Amruta; Rusch, Leslie; Zhang, Xiaoguang
    We experimentally demonstrate and evaluate an optimization strategy of a recirculating frequency shifting (RFS) optical comb for terabit flexible optical networks. We achieve an increased optical signal-to-noise ratio (OSNR) with good stability (no system outage) by reducing erbium-doped-fiber amplifier gain in the shifting loop and deploying an in-loop noise suppression filter. We demonstrate that this source can support 20×200  Gb/s dual polarization Nyquist-16QAM transmission. With optimization, the RFS comb has greater and more uniform OSNR per channel. Flexible optical networks with software-defined networking are particularly suited to this enhanced RFS due to 1) programmable frequency spacing, 2) dense, stable spacing enabling very high spectral efficiency, 3) uniform performance across channels, and 4) sufficient OSNR for high-order modulation. The RFS can be used in short links when using low overhead forward error correction (FEC). Distances as great as 1150 km are achieved when using a 20% FEC overhead. Long-distance tests at 4 Tb/s result in a post-FEC net rate of 3.3 Tb/s and 6.3 bit/s/Hz of spectral efficiency.
  • Publication
    Accès libre
    Radially anisotropic ring-core optical fiber : towards vector-vortex guided transmission using the full modal space
    (Optical Society of America, 2021-04-06) Sharma, Manish; LaRochelle, Sophie; Vigneswaran, Dhasarathan; Ung, Bora; Rusch, Leslie
    The radially anisotropic ring-core fiber with cylindrical birefringence is theoretically and numerically investigated as a novel platform for the transmission of vector-vortex beams with unique modal properties. First, we elucidate the parametric conditions where such fiber enables modal substitution in which either the donut-shaped azimuthal TE01 or radial TM01 mode replaces the normal Gaussian-like HE11 mode as the fundamental mode of the waveguide. We also demonstrate that it is possible to significantly engineer the waveguiding properties of the fiber via the addition of small radial birefringence (~10−4 ) so as to make the (hitherto non-degenerate) TE0m and TM0m modes fully degenerate. The latter property is used to create stable vortex modes of high purity (>99%) with the newly degenerate modal pair – a feat not possible with standard few-mode fibers – all without affecting the co-propagating hybrid HE/EH modes that remain available as an independent basis set to produce vortex beams of similarly high purity. These new insights are relevant to the topical fields of mode-division multiplexing (MDM), structured light, fiber modelling and fabrication. With respect to MDM applications, the newly available vortex modes created with the degenerate TE/TM basis set can now be concurrently used with the more common vortex modes created via the HE/EH modal basis set.