An evidential approach for detection of abnormal behaviour in the presence of unreliable sensors

We address the problem of abnormal behaviour recognition of the inhabitant of a smart home in the presence of unreliable sensors. The corner stone of this work is a two-level architecture sensor fusion based on the Transferable Belief Model (TBM). The novelty of our work lies in the way we detect both unreliable sensors and abnormal behaviour within our architecture by using a temporal analysis of conflict resulting from the fusion of sensors. Detection of abnormal behaviour is based on a prediction/observation process and the influence of the faulty sources is discarded by discounting coefficients. Our architecture is tested in a real-life setting using three heterogeneous sensors enabling the detection of impossible transitions between three possible postures: Sitting, Standing and Lying. The impact of having a faulty sensor management is also tested in the real-life experiment for posture detection.     

Modeling gain dynamics of thulium-doped fiber amplifiers

The transient response of single-(14xx nm) and dual-(14xx + 1550 nm) wavelength-pumped thulium-doped fiber amplifiers is modeled. With an optimally chosen method for numerical integration of rate equations involving several energy levels, we can estimate the transient response and frequency dependent characteristics during add-drop transitions. Results correspond to the experimental data with good accuracy.     

Raman fiber oscillator as optical amplifier

A Raman fiber oscillator used for optical amplification is demonstrated to have lower double Rayleigh scattering, transient spikes, cross-phase modulation, and higher saturation input threshold compared with a conventional discrete Raman amplifier at similar operating conditions. This could be a promising technology for deployment in practical systems.     

High-nonlinearity fiber optical parametric amplifier with periodicdispersion compensation

Theory shows that the maximum gain and bandwidth of one-pump fiber optical parametric amplifiers made from high-nonlinearity fiber, operated with a pump wavelength λ_p far from the fiber zero-dispersion wavelength λ₀ can greatly be improved by periodic dispersion compensation. We have performed experiments and obtained good agreement with theory: for λ_p=1542 and λ₀=1591 nm, we have increased the bandwidth from 7 to 28 nm, and the maximum gain from 15 to 20 dB, by splicing three pieces of standard fiber at regular intervals in a 40-m long nonlinear fiber     

200-nm-bandwidth fiber optical amplifier combining parametric andRaman gain

Theory shows that the gain bandwidth of a one-pump fiber optical parametric amplifier (OPA) using highly nonlinear fiber (HNLF) could be more than 200 nm. Under these circumstances, the OPA gain would overlap the pump-induced Raman gain. We have studied the combined effects of OPA and Raman gain theoretically and experimentally. The experimental results demonstrate a 200-nm bandwidth from a single fiber-optical amplifier and also verify that the influence of the Raman effect is relatively small, as predicted by the theory     

All-optical 3R regeneration technique using injection-locking ingain-switched DFB-LD

A new all-optical 3R regeneration technique using injection-locking in a gain-switched DFB-LD is proposed. The operation of the technique is confirmed numerically and experimentally. Both simulation and experimental results show that the degraded RZ pulses are reshaped, retimed, and regenerated by injection-locking, into short pulses generated by gain-switching. Moreover, error-free all-optical 3R regeneration at 2.5 Gbit/s has been successfully achieved, with 1.5 dB negative penalty     

Calculation of dispersion in arrayed waveguide grating demultiplexers by a shifting-image method

It is shown that, as a first approximation, chromatic dispersion in demultiplexers based on arrayed waveguide gratings (AWGs) is proportional to the local spatial curvature of the wavefronts of the field at the output of the input guide, whose image shifts across the output guide as frequency changes. More accurate results can be obtained by convolving the input field with the AWG impulse response and the output guide mode. This approach to the calculation of dispersion provides physical insights from the field of imaging, not available with the commonly used method which relies on a Fourier series approach. Spherical wavefronts lead to constant dispersion. The use of a parabolic taper at the end of the input guide can lead to large amounts of dispersion, varying across the filter passband; this case is treated in detail. The method can also be adapted for use with demultiplexers based on reflective echelle gratings.     

Fibre optical parametric amplifiers with circularly-polarised pumps

A fibre optical parametric amplifier with orthogonal circularly-polarised pumps requires only half the pump power of an amplifier with linearly-polarised pumps to achieve a given gain. The gain is also independent of the polarisation of the input signal.     

Gain reciprocity in fibre optical parametric amplifiers

A fibre optical parametric ampifier operating in the small-signal gain regime can exhibit the same gain when amplifying in either direction. This is true even in the presence of random dispersion and birefringence variations along the fibre.     

Gain-clamped thulium-doped fibre amplifier with single pump at 1050 nm

The large homogeneous bandwidth of a thulium-doped fibre amplifier makes it suitable for optical gain clamping. This has been demonstrated experimentally. Gain variation of 1.2 dB for 15 dB input dynamic range has been achieved, with less than 1 dB gain ripple over 20 nm, and no noise figure degradation, while pumped at 1050 nm.