Experimental analysis of all-optical 4-ASK signal generation through parametric amplification

We present experimental results concerning a new alloptical technique that multiplexes two binary signals into a quaternary one (4-ASK). The technique is based on parametric amplification. Values of the quaternary levels obtained experimentally, as a function of the extinction ratios of the binary input signals, show a rather good agreement with the simulated and the analytical results. The generated 4-ASK signals were propagated through 75 km of standard single-mode fiber and experienced eye penalties of only 0.5 dB. This indicates the robustness of the technique for practical applications in metropolitan area networks.174191Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Applicability of low macrobending loss hollow-core PCF to FTTH applications

Fiber-To-The-Home (FTTH) technology has been significantly implemented in access networks, providing very high data rates transmission and a variety of digital content to subscribers. It involves an optical cable link being installed between the building entry point and each subscriber with the Multiple Dwelling Units (MDUs), i.e. flats and apartments. In other words, optical cable has to lie fairly straight to carry a strong signal, since typically is necessary to bend, twist and turn the lines in and out of tight corners without degrading the link connection. In this paper we propose the use of Hollow-Core Photonic Crystal Fiber (HC-PCF) for FTTH applications. It is presented an experimental analysis of the macrobending effects in a HC-PCF based on a comparison with traditional fibers and by following the ITU-T G.657B standard recommendations. We observe this fiber, with only 6.5 µm core, is bending loss insensitive, even at extremely small bending radius of 2 mm, in which it presents a loss of only 0.58 dB.251258Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

High-order dispersion mapping of an optical fiber

We report on measurements of high-order dispersion maps of an optical fiber, showing how the ratio between the third and fourth-order dispersion (β3/β4) and the zero-dispersion wavelength (λ0) vary along the length of the fiber. Our method is based on Four-Wave Mixing between short pulses derived from an incoherent pump and a weak laser. We find that the variations in the ratio β3/β4 are correlated to those in λ0. We present also numerical calculations to illustrate the limits on the spatial resolution of the method. Due to the good accuracy in measuring λ0 and β3/β4 (10 -3% and 5% relative error, respectively), and its simplicity, the method can be used to identify fiber segments of good uniformity, suitable to build nonlinear optical devices such as parametric amplifiers and frequency comb generators28342584273FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2012/50259-8; 2015/11779-4; 2017/16151-9; 2018/08988-9; 2019/16793-6Fundação de Amparo à Pesquisa do Estado de São Paulo (2012/50259-8, 2015/11779-4, 2017/16151-9, 2018/08988-9, 2019/16793-6); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) (COL-10-2-05

Coherent Control of Ultra-High Frequency Acoustic Resonances in Photonic Crystal Fibers

Ultra-high frequency acoustic resonances ($\backsim$2 GHz) trapped within the glass core ($\backsim$1 $\mu$m diameter) of a photonic crystal fiber are selectively excited through electrostriction using laser pulses of duration 100 ps and energy 500 pJ. Using precisely timed sequences of such driving pulses, we achieve coherent control of the acoustic resonances by constructive or destructive interference, demonstrating both enhancement and suppression of the vibrations. A sequence of 27 resonantly-timed pulses provides a 100-fold increase in the amplitude of the vibrational mode. The results are explained and interpreted using a semi-analytical theory, and supported by precise numerical simulations of the complex light-matter interaction.Comment: 4 pages, 3 figures, 3 avi movies (external link) - accepted in PR

Controlled stacking of graphene monolayer saturable absorbers for ultrashort pulse generation in erbium-doped fiber lasers

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPStacked chemical-vapour deposited (CVD) graphene monolayer samples were fabricated and applied as saturable absorbers in erbium-doped fiber laser (EDFL). Transient absorption experiments show that at the saturation absorption regime, and regardless the number of stacked layers (from 1 to 5 layers), samples present 1 ps recovery time. Pulses with duration from 0.60 to 1.17 ps were generated in an EDFL, depending on the number of graphene layers (i.e., the linear optical absorption) used. The results show that it is possible to increase the linear optical absorption of a graphene stacking without affecting its nonlinear optical behavior and ultrafast response time. Therefore, by stacking individual CVDmonolayer graphene samples it is possible to control the optical properties in graphene-based EDFLs and simultaneously tune their ultra-short pulse generation.7725282537FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2010/19085-82012/07678-02012/50259-82013/16911-

An all-optical OCDMA encoder with simultaneous signal regeneration based on fiber four-wave mixing

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPA new all-optical optical code division multiple access encoder that simultaneously regenerates input signals is proposed and experimentally investigated. The device is based on a fiber four-wave mixing and experimental results show that eye penalties may be decreased up to 5.1 dB. (c) 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1024-1028, 2014A new all-optical optical code division multiple access encoder that simultaneously regenerates input signals is proposed and experimentally investigated. The device is based on a fiber four-wave mixing and experimental results show that eye penalties may be decreased up to 5.1 dB.56510241028CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFAPESP [574017/2008-9, 08/57857-2, 310644/2011-9]08/57857-2574017/2008-9310644/2011-

Nonlinear carrier dynamics in silicon nano-waveguides

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESThe understanding of free-carrier dynamics in silicon photonic nano-waveguides and micro-cavities is fundamental to several nonlinear optical phenomena. Through time-resolved pump and probe experiments, a complex and nonlinear carrier recombination dynamics is revealed. Our results show that the carrier lifetime varies as the recombination evolves, with faster decay rates at the initial stages (with lifetime of similar to 800 ps) and much slower lifetimes at later stages (up to similar to 300 ns). The large surface-to-volume ratio in nano-waveguides enables clear observation of the effect of carrier trapping, manifesting as a decay curve that is highly dependent on the initial carrier density. Further, we demonstrate faster recombination rates by operating at high carrier density. Our results, along with a theoretical framework based on trap-assisted recombination statistics applied to nano-waveguides, can impact the dynamics of several nonlinear nanophotonic devices in which free carriers play a critical role, and open further opportunities to enhance the performance of all-optical silicon-based devices.41012191227FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES2008/578572012/50259-82013/20180-32015/04113-02015/11779-4574017/2008-9Sem informaçã

Efficient Calculation Of Higher-order Optical Waveguide Dispersion.

An efficient numerical strategy to compute the higher-order dispersion parameters of optical waveguides is presented. For the first time to our knowledge, a systematic study of the errors involved in the higher-order dispersions' numerical calculation process is made, showing that the present strategy can accurately model those parameters. Such strategy combines a full-vectorial finite element modal solver and a proper finite difference differentiation algorithm. Its performance has been carefully assessed through the analysis of several key geometries. In addition, the optimization of those higher-order dispersion parameters can also be carried out by coupling to the present scheme a genetic algorithm, as shown here through the design of a photonic crystal fiber suitable for parametric amplification applications.1819522-3