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Québec, Canada

Simard A.D.,Laval University | Ayotte N.,Laval University | Painchaud Y.,TeraXion | Bedard S.,Laval University | LaRochelle S.,Laval University
Journal of Lightwave Technology | Year: 2011

A major issue in the fabrication of integrated Bragg grating (IBG) filters in highly confined waveguides is the average effective index fluctuations caused by sidewall roughness. In this work, we model the impact of this effect on IBG spectral responses and we identify key parameters that need to be controlled in order to minimize distortions. We show that only low spatial frequency components of the noise are relevant to the calculation of the IBG spectral response, which decreases considerably the computation time. Furthermore, we present an IBG emulator that allows estimation of expected fabrication yield of specific gratings given that the fabrication process is well characterized. The analysis of apodized gratings is used as an example to illustrate how this modeling can help to reduce development cost by first studying robustness of IBG designs to fabrication limitations. Finally, we study analytically the impact of sidewall roughness having short correlation lengths and small roughness variances on the spectral response of weak gratings. © 2006 IEEE.

Morsy-Osman M.,McGill University | Chagnon M.,McGill University | Poulin M.,TeraXion | Lessard S.,Ericsson AB | Plant D.V.,McGill University
Journal of Lightwave Technology | Year: 2015

A polarization-division-multiplexed (PDM) intensity-modulation/direct-detection (IM/DD) system enabled by a novel multiple-input and multiple-output DSP operating in the Stokes space following a DD receiver is demonstrated. Modulating the intensity of the two orthogonal polarization states of a single laser enables doubling the maximum achievable bit rate per wavelength channel, which halves the number of required laser sources in a transceiver using PDM and WDM to achieve an aggregate bit rate compared to using only WDM. Quantitatively, 224 Gb/s is experimentally transmitted over 10 km using a single 1310-nm laser and a silicon photonic intensity modulator using 56-Gbaud PDM PAM-4 with a BER of 4.1 × 10-3. Also, PDM enables halving the baud rate needed to achieve 112 Gb/s resulting in 20-km transmission at low BERs (10-5-10-6), using either 56-Gbaud PAM-2 or 28-Gbaud PAM-4. These low pre-FEC BERs achieved at 112 Gb/s allow reducing the FEC overhead required compared to a single polarization system that employs twice the baud rate to achieve the same bit rate. Though the transceiver was implemented using discrete components, it can be fully integrated on a SiP chip, enabling its practical realization for short-reach optical interconnects inside datacenters. Finally, in addition to the experimental results, we perform simulations to further investigate the performance of the receiver. In particular, we studied the impact of varying the splitting ratios of the two couplers in the proposed front-end and concluded that using 67/33 couplers instead of 50/50 couplers renders the performance completely independent of the state of polarization of the received signal. © 2015 IEEE.

Simard A.D.,Laval University | Painchaud Y.,TeraXion | La Rochelle S.,Laval University
Optics Express | Year: 2013

Over the last two decades, many filters requiring custom spectral responses were obtained from photo-inscribed fiber Bragg gratings because of the flexibility inherent to this technology. However, Bragg gratings in silicon waveguides have the potential to provide faster and more efficient tuning capabilities when compared to optical fiber devices. One drawback is that Bragg gratings filters with elaborate spectral amplitude and phase responses often require a long interaction length, which is not compatible with current integration trends in CMOS compatible photonic circuits. In this paper, we propose to make Bragg gratings in spiral-shaped waveguides in order to increase their lengths while making them more compact. The approach preserves the flexibility of regular straight grating structures. More specifically, we demonstrate 2-mm long gratings wrapped in an area of 200 μm x 190 μm without any spectral degradation due to waveguide curvature. Furthermore, we interleave three spiral waveguides with integrated gratings thereby tripling the density and demonstrate good phase compensation for each of them. Finally, we show that this approach is compatible with phase-apodization of the grating coupling coefficient. © 2013 Optical Society of America.

Simard A.D.,Laval University | Beaudin G.,Universite de Sherbrooke | Aimez V.,Universite de Sherbrooke | Painchaud Y.,TeraXion | LaRochelle S.,Laval University
Optics Express | Year: 2013

A major issue in the fabrication of integrated Bragg grating filters in highly confined waveguides is the average effective index fluctuations caused by waveguide dimension variations. Lateral variations are caused by the sidewall roughness created during the etching process while vertical variations are coming from the wafer silicon layer thickness non-uniformity. Grating spectral distortions are known to result solely from the low spatial frequency components of these variations. As a result, in this work, we present an experimental method to quantify such relevant spatial components by stitching a hundred high-resolution scanning electron microscope images. Additionally, we propose two techniques to reduce, in the design, the phase noise impact on integrated Bragg gratings without relying on fabrication process improvements. More specifically, we show that the use of hybrid multimode/singlemode waveguides reduce by more than one order of magnitude the effect of sidewall roughness on integrated Bragg gratings while we show that the fabrication of ultra-compact gratings in spiral waveguides mitigate the impact of the silicon layer thickness variations. ©2013 Optical Society of America.

Simard A.D.,Laval University | Belhadj N.,Laval University | Painchaud Y.,TeraXion | Larochelle S.,Laval University
IEEE Photonics Technology Letters | Year: 2012

An accurate control of the apodization profile is still an issue for integrated Bragg grating filters fabricated in silicon-on-insulator because of the high modal confinement of these waveguides. In this letter, we present two fabrication-friendly apodization techniques that are compatible with deep UV lithography and can be used in mass-production of photonic-integrated circuits. These techniques are reliable even for weak effective index modulation amplitude, thus opening the door to the fabrication of long and elaborate grating structures. © 2012 IEEE.

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