Encontrados 12 documentos, a visualizar página 1 de 2
Evolution of first-order sidebands from multiple FWM processes in HiBi optical ...
Silva, Nuno A.; Muga, Nelson J.; Pinto, Armando N.The generation of two idler waves inside a high birefringent (HiBi) optical fiber through three four-wave mixing (FWM) processes is studied theoretically. The coupled-equations for the field amplitudes are derived and analytically solved, in the co-polarized and orthogonal polarization schemes. The obtained solutions take into account the delayed Raman response of the medium. The polarization sensitivity of the...
Broadband polarization pulling using Raman amplification
Muga, Nelson J.; Ferreira, Mario F. S.; Pinto, Armando N.The Raman gain based polarization pulling process in a copropagating scheme is investigated. We map the degree of polarization, the angle between the signal and pump output Stokes vectors, the mean signal gain and its standard deviation considering the entire Raman gain bandwidth. We show that, in the undepleted regime (signal input power similar to 1 mu W), the degree of polarization is proportional to the pum...
Polarization-entangled photon pairs using spontaneous four-wave mixing in a fib...
Almeida, Álvaro J.; Carneiro, Steven R.; Silva, Nuno A.; Muga, Nelson J.; Pinto, Armando N.We generate polarization-entangled photon pairs in the 1550-nm wavelength telecom band, using spontaneous fourwave mixing in a highly nonlinear fiber loop. With accidental coincidences subtracted, we obtain coincidence fringes with visibilities greater than 86%, and thus observe a violation of Clauser, Horne, Shimony and Holt (CHSH) inequality by 2.7 standard deviations. The experimental setup is built using on...
Correlated photon-pair generation in a highly nonlinear fiber using spontaneous...
Almeida, Álvaro J.; Martins, Luís M.; Silva, Nuno A.; Muga, Nelson J.; Pinto, Armando N.We generate 1550 nm correlated photon pairs through the spontaneous four-wave mixing (SpFWM) process in a highly nonlinear fiber (HNLF). The pair source quality generation is evaluated by the coincidence-to-accidental ratio (CAR) parameter. It is verified that the spontaneous Raman scattering (SpRS) photons generated inside the fiber contribute to the degradation of the source. Nevertheless, a CAR value of 2.77...
QBER Estimation in QKD Systems With Polarization Encoding
Muga, Nelson; Ferreira, Mário; Pinto, ArmandoA model for quantum BER estimation in polarization encoded quantum key distribution systems is presented. Both TDM and WDM based polarization control schemes are analyzed. It is shown that TDM presents some important advantages when compared with the WDM control scheme. In WDM, the polarization decorrelation between the reference and data signals is an intrinsic and very limitative impairment. This effect has a...
Polarization effects in fiber-optic communication systems
Muga, Nelson de Jesus CordeiroIn this thesis we perform a detailed analysis of the state of polarization (SOP) of light scattering process using a concatenation of ber-coil based polarization controllers (PCs). We propose a polarization-mode dispersion (PMD) emulator, built through the concatenation of bercoil based PCs and polarization-maintaining bers (PMFs), capable of generate accurate rst- and second-order PMD statistics. We analyz...
Time coincidence of entangled photon pairs using spontaneous four-wave mixing i...
Almeida, Álvaro J.; Carneiro, Steven R.; Silva, Nuno A.; Muga, Nelson J.; Pinto, Armando N.We obtained a source of entangled photon pairs in the 1550-nm wavelength band using spontaneous four-wave mixing (SpFWM) in a Sagnac fiber loop. Time coincidence of entangled photon pairs was verified for a 300-m dispersion-shifted fiber (DSF), using an avalanche photodiode (APD). ; QuantTel - Quantum Secure Telecommunications ; Quant- PrivTel - Quantum Private Telecommunications - PTDC/EEATEL/ 103402/2008
Fiber-optical communication system using polarization-encoding photons
Almeida, Álvaro J.; Silva, Nuno A.; Muga, Nelson J.; Pinto, Armando N.We present a single-photon source based on the stimulated four-wave mixing process with adjustable linear state of polarization. This source allowed us to generate non-orthogonal states of polarization, that can be used for quantum key distribution experiments. The average number of photon counts as a function of the angle of the analyzer was obtained for two non-orthogonal linear states of polarization. The re...
Single-photon source based on FWM with adjustable linear SOP
Almeida, Álvaro J.; Silva, Nuno A.; Muga, Nelson J.; Pinto, Armando N.We present a setup able to generate and detect single photons in optical fibers using the stimulated four-wave mixing (FWM) process. The results show an accurate generation of single photons at four different linear states of polarization (SOPs), with angles 0, 45, 90 and -45 degrees. The detection was performed in back-to-back configuration and after transmission over an optical fiber with a length up to 10 m.
Polarization scattering property of cascaded polarization controllers
Muga, Nelson J.; Ferreira, Mário F.; Pinto, Armando NolascoThe relation between the allowed range of variation of polarization controller wave-plates angles and the respective polarization scattering properties is investigated It is demonstrated that a nearly uniform polarization scattering over the Poincare sphere is obtained using a concatenation of three polarization controllers with angles randomly changed between -pi/4 and pi/4. It is also shown that an improvemen...
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