We realize a fiber Bragg grating InGaN-based laser diode emitting at 400 nm and demonstrate its high coherency. Thanks to the fabrication of a narrowband fiber Bragg grating in the near-UV, we can reach single-mode and single-frequency regimes for the self-injection locked diode. The device exhibits 44 dB side-mode suppression ratio and mW output power.
View Article and Find Full Text PDFSpectral measurements are employed in many precision agriculture applications, due to their ability to monitor the vegetation's health state. Spectral vegetation indices are one of the main techniques currently used in remote sensing activities, since they are related to biophysical and biochemical crop variables. Moreover, they have been evaluated in some studies as potentially beneficial for detecting or differentiating crop diseases.
View Article and Find Full Text PDFThis paper describes the design of a 3D image acquisition system dedicated to natural complex scenes composed of randomly distributed objects with spatial discontinuities. In agronomic sciences, the 3D acquisition of natural scene is difficult due to the complex nature of the scenes. Our system is based on the Shape from Focus technique initially used in the microscopic domain.
View Article and Find Full Text PDFWe report on all-optical wavelength conversion of a 56 Gb/s differential quadrature phase shift keying signal and a 42.7 Gb/s on-off keying signal. Wavelength conversion is based on four-wave mixing effect in a 1 m long highly nonlinear GeAsSe chalcogenide fiber.
View Article and Find Full Text PDFBackground And Aims: The productivity and stability of grazed grassland rely on dynamic interactions between the sward and the animal. The descriptions of the sward canopies by standard 2-D representations in studies of animal-sward interactions at the bite scale need to be improved to account for the effect of local canopy heterogeneity on bite size and regrowth ability. The aim of this study was to assess a methodology of 3-D digitized canopies in order to understand the balance between bite mass and light interception by the residual sward.
View Article and Find Full Text PDFSignal transmission experiments were performed at 170 Gbit/s in an integrated Al(2)O(3):Er(3+) waveguide amplifier to investigate its potential application in high-speed photonic integrated circuits. Net internal gain of up to 11 dB was measured for a continuous-wave 1532 nm signal under 1480 nm pumping, with a threshold pump power of 4 mW. A differential group delay of 2 ps between the TE and TM fundamental modes of the 5.
View Article and Find Full Text PDFWe report on the experimental and theoretical study of a self-phase-modulation-based regenerator at 42.6 Gbit/s with a return-to-zero 33% format. We point out some detrimental effects such as intrachannel interactions and Brillouin scattering.
View Article and Find Full Text PDFWe report on a passive all-optical clock recovery technique based on data signal filtering with a Fabry-Perot filter, tested in a 40 Gb/s transmission system. We have simulated the clock recovery principle to choose the filter finesse and then investigate with experiment the method for 43 Gbit/s RZ signal clock recovery ahead of a receiver. We use Bit Error Rate assessment to demonstrate its system compatibility and to evaluate both its pattern sequence length tolerance and, for the first time, its clock locking range.
View Article and Find Full Text PDFWe observe the effects of a temperature increase on the characteristics of an InGaAs/InP multiple-quantum-well (MQW) saturable absorber (SA) in a microcavity provided by an optical input signal under normal incidence. The temperature increase on the nonlinear mirror (NLM) due to an optical signal depends on the energy time filling factor (FF) of this input signal (analogous to the signal's duty cycle, which is the ratio between the repetition period and the pulse duration) and hence depends on the repetition rate of the signal for a given pulse time width. This increase in temperature is mostly responsible for a shift in the reflectivity spectrum of the device toward higher wavelengths.
View Article and Find Full Text PDFWe numerically investigate the 2R-regeneration technique utilizing self-phase modulation and off-center filtering. Our numerical simulations take into account the incoherent nature of noise through its spectral representation. This approach allows to evaluate a Q-factor improvement of 2 dB for this regenerator.
View Article and Find Full Text PDFWe studied the effects of stubble carbon / nitrogen (C / N) reserves or residual leaf area (RLA) on the contribution of taproot C / N reserves to shoot regrowth of Medicago sativa L. after cutting. The study assessed the effects of two cutting heights (6 and 15 cm), two RLAs (0 or 100%), and two initial C / N reserve levels (high N or low N) on forage production, nitrogen (N) distribution, and C / N reserve dynamics within stubble and taproot.
View Article and Find Full Text PDFThe contribution of nitrogen reserves to regrowth following defoliation was studied in white clover plants (Trifolium repens cv. Huia). This was found to be closely linked to the morphological pattern of development of the aerial parts during the same period.
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