Fiber transmission demonstrations in vector mode space division multiplexing

Much attention has been focused on the use of scalar modes for space division multiplexing (SDM). Alternative vector mode bases offer another solution set for SDM, expanding the available trade-offs in system performance and complexity. We present two types of ring core fiber conceived and designed to explore SDM with fibers exhibiting low interactions between supported modes. We review demonstrations of fiber data transmission for two separate vector mode bases: one for orbital angular momentum (OAM) modes and one for linearly polarized vector (LPV) modes. The OAM mode demonstrations include short transmissions using commercially available transceivers, as well as kilometer length transmission at extended data rates. The LPV demonstrations span kilometer length transmissions at high data rate with coherent detection, as well as a radio over fiber experiment with direct detection of narrowband signals

Silicon photonic modulator using mode conversion with asymmetric sidewall bragg gratings

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

Widely tunable silicon Raman laser

Stimulated Raman scattering is an effective means of wavelength conversion and can largely extend the operating spectral range of an optical source. We demonstrate a highperformance tunable Raman laser on a sub-micrometer-thick silicon on insulator wafer using a standard foundry process. The key feature to this laser is the use of a tunable coupling mechanism to adjust both pump and signal coupling coefficients in the ring cavity, allowing demonstration of laser emission over a large wavelength tuning range of 83 nm. This Raman laser demonstrates efficient (slope of up to 26% and a maximum pump-to-signal power conversion efficiency of 10%) on-chip non-linear wavelength conversion. Our results indicate great promise for substantially increasing the optical spectral resources available on a silicon chip

Efficiency-speed tradeoff in slow-light silicon photonic modulators

he purpose of this paper is twofold. First, we discuss the efficiency-speed tradeoff in slow-light (SL) silicon photonic (SiP) modulators. For this, a comprehensive model for the electro-optic (EO) response of lumped-electrode SL Mach-Zehnder modulators (SL-MZMs) is presented. The model accuracy is verified by comparing it to experiments. Our analysis shows that slowing down the optical wave helps to enhance efficiency by increasing the interaction time between the optical wave and the uniform voltage across lumped electrodes, but at the cost of limiting the EO bandwidth. Then, we investigate SL-MZMs with traveling-wave (TW) electrodes whose dynamic interaction is predicted using a distributed circuit model. Having been solved by the finite-difference time-domain (FDTD) method, the model shows that TW SL-MZMs are capable of improving both efficiency and speed under an optimized SL effect. We also compare SL-MZMs with conventional MZMs (C-MZM) considering a figure of merit (FOM) that combines key parameters such as efficiency, loss, and EO bandwidth. We show that the additional loss of SL waveguides significantly impacts the preferred modulator choice at different baudrates. The second aim of this paper is to examine different design strategies to reduce Vπ of C-MZMs in order to meet the requirement of COMS driver using 1) a longer phase shifter, 2) higher doping densities, and 3) the SL effect. It is shown that the SL effect provides the best overall performance among the three. Indeed, only the SL effect offers simultaneous improvement in Vπ, footprint, and EO bandwidth; the other approaches provide Vπ reduction but at the cost of reduced speed or enlarged footprint (or even both)

Mach-Zehnder silicon photonic modulator assisted by phase-shifted Bragg gratings

We experimentally demonstrate a silicon photonic Mach-Zehnder modulator (MZM) assisted by phase-shifted Bragg gratings. Coupled resonators are inserted in the Bragg grating structure to significantly enhance the phase modulation efficiency, while maintaining a wide optical bandwidth compared to other resonator-based modulators. Fabricated using a CMOS-compatible foundry process, the device achieved a small-signal Vπ× L of 0.18 V.cm, which is seven times lower than a conventional silicon MZM fabricated with the same process. The device has a compact footprint, with a length of only 162 μm , and shows a modulation bandwidth of 28 GHz at a reverse bias of 1 V. Non-return-to-zero modulation is demonstrated at 30 Gb/s with a bit-error-rate (BER) below the 7%-overhead forward error correction (FEC) threshold over a bandwidth of 3.5 nm. This bandwidth should translate into an operating temperature range greater than 40 0 C

Historiographie des matériaux et instruments du dessin à la Renaissance : de Joseph Meder à Annamaria Petrioli Tofani

Le présent mémoire porte sur les matériaux et les instruments utilisés en dessin à la Renaissance. Le papier, qui fait son apparition en Europe au 12e siècle, permet aux artistes de développer un art - l'arte del disegno - jusqu'alors considéré comme une pratique relevant davantage de la technique que de la créativité. Grâce aux différents instruments (pointes de métal, plumes, pinceaux) et matériaux (encre, pierre noire, sanguine), ainsi qu'aux diverses techniques (lavis, hachures, estompe), les artistes renaissants parviennent à concevoir la nature et la figure humaine non plus en tant que forme géométrique, mais plutôt comme expression de l'esprit. L'analyse du processus de fabrication des papiers et instruments, de la préparation des matériaux et des multiples usages de l'ensemble de ces outils permet de mieux comprendre cette nouvelle conception de l'art

Silicon photonic modulator loaded by NPN junctions

We experimentally demonstrate an asymmetric Bragg grating modulator with a phase shifter length of 240 μm, loaded by p-n junctions. The mode conversion by the asymmetric sidewall grating allows us to operate a Bragg modulator in reflection without a circulator. Simulation results show that there is room for improving the modulator efficiency and footprint by exploiting NPN junctions instead of p-n junctions

Silicon photonic modulator using coupled bragg grating resonators in a Mach-Zehnder structure

We demonstrate a silicon modulator enhanced by Bragg-grating resonators. The compact modulator (130- µm phase shifters) with Vπ×L= 0.25 V.cm has a 32-GHz EO bandwidth consuming only 80 fJ/bit at 10 Gbit/

Silicon photonic modulator based on coupled Bragg grating resonators used as phase shifters

Bragg gratings with phase-shifts are inserted in a Mach-Zehnder modulator to enhance phase modulation, reduce device length and improve efficiency (Vπ×L=0.28 Vcm). Simulations show 3 nm optical bandwidth corresponding to 50 K operating temperature range

Quantifying the coupling and degeneracy of OAM modes in high-index-contrast ring core fiber

We study orbital angular momentum (OAM) mode coupling in ring-core fibers (RCFs) due to elliptical shape deformation. We introduce a coupling model based on numerical mode solver outputs of perturbation. We show improved predictions in calculating coupling strength compared to the classical modeling approach. Our model captures and quantifies the disparate behaviors of coupling in lower and higher order degenerate OAM modes. The ideal orthogonality of modes is undermined by fiber imperfections. Our model predicts the OAM order at which the orthogonality within OAM mode pair is maintained despite elliptical deformation. We use our coupling model to simulate propagation effects and compare the performance of two fibers (thin and thick RCF) designed under the same constraints. Our numerical propagation results show different performance for the two fibers under the same level of elliptical deformation. This model uncovers distinct digital signal processing requirements for these two types of fiber, and predicts their signal-to-noise ratio penalty. For each fiber, we examine the large number of supported modes and find the optimal subset of mode groups, i.e., the groups with the lowest penalty. We show that this optimal subset is different from that predicted during the fiber design optimization