Effect of probing signal on the output signals spectrum of nonlinear spin waves in a cross based on waveguides of iron-yttrium garnet film

Subject. A change in the spectrum of spin waves (SW) in a magnetic cross is investigated when two signals pass through it: a pump signal and a probe signal. Objective. Detection of specific features in formation of the spectra of the output signals of SW in the multiport structure based on a yttrium iron garnet (YIG) film in the case of excitation of two magnetostatic surface waves (MSSW) simultaneously by the input antenna, where the first, with power higher than the first-order parametric instability threshold is the pump, and the second one is a probe. Methods. The experiments were performed for a cross structure from YIG film in the form of two orthogonal waveguides with the SW wire antennas placed at the ends of the waveguides, where one of the antennas on the transversely magnetized waveguide was considered as the input. Result. It was found that by choosing the probing signal frequency, one can significantly (by 10 dB) change the relative signal levels for the satellite waves at the output antennas, which are secondary MSSWs with some new frequencies and appear in the output signals spectrum as a result of the thresholdless processes of merging of parametric spin waves generated by MSSW pumping. In this case the secondary MSSWs frequencies can differ at the output antennas located on orthogonal waveguides. Discussion. The discovered effect is associated with the nonreciprocal nature of propagation of both the pumping wave and the waves generated at parametric instability condition in the structure.

Real-time hydraulic fracture monitoring and wellbore characterization with distributed acoustic sensing of pumping noise

The strong and regular acoustic signal provided by working pumps spreads along a well based on wellbore geometrical and physical attributes. This signal can be used to devise well properties through the interpretation of distributed acoustic data collected along a zone of interest. Any well feature that is an irregularity of the well scheme, such as tubing expansion, fluid-to-fluid interface, or an adjacent hydraulic fracture, porous reservoir, or annular compartment, can be characterized this way. Every pump generates a plurality of harmonic frequencies; thus, there are plenty of data for inversion for feature parameters. We describe a quantitative inversion workflow and give synthetic examples of hydraulic fracture monitoring and hydraulic port open/closure condition monitoring. We also stress that interference of the pump signal by the flow noise signal should be accounted for in distributed acoustic sensing interpretation.

Numerical analysis of pump-signal-direction effect on the performance of EDFA systems

Purpose The purpose of this study is to develop new tandem configurations of erbium-doped fiber amplifier (EDFA) using all possible pump-signal-direction schemes in simulation to identify a system configuration with the best performance in the means of the highest gain with the lowest noise figure (NF) output. Design/methodology/approach The spatial evolution of the physical properties such as gain, NF, population density and amplified spontaneous emission along the total length of the double-stage single-pass EDFA and single-stage double-pass EDFA configurations under all possible pumping direction schemes was investigated. Giles and Desurvire method was used for the mathematical modeling of these configurations where the two level coupled system model equations was solved in MATLAB. In the simulation of the all proposed configurations, an input signal of −35 dBm at the wavelength of 1550 nm and a total of 14 mW pump power at the wavelength of 1480 nm was used for a consistent analysis. Findings The numerical value of the results obtained is specific to the input parameter values used in the simulations; however, configuration-wise, the EDFA systems found with the best performance are not parameter specific. Originality/value The results of this numerical work will help future experimental research of designing and developing ultra-efficient EDFA systems.