In this paper, we study the average throughput performance of energy beamforming in a multi-antenna wireless-powered communication network (WPCN). The considered consists one hybrid access-point (AP) with multiple antennas and single antenna user. user does not have constant power supply thus needs to harvest from signals broadcast by AP downlink (DL), before sending its data back harvested uplink (UL). We derive closed-form expressions their asymptotic at high SNR for both delay-limited...

Through dynamic calculation and electromagnetic particle-in-cell simulation, high-power microwave dielectric multipactor is discovered to be suppressed by utilizing external dc magnetic field parallel the surface, perpendicular rf satisfying gyrofrequency close frequency Ω∼ω. It found that electrons emitted from surface can resonantly accelerated obtain impact energy εe higher than second crossover energy, leading secondary emission yield lower one. Besides, corresponding flight time gets...

This Letter presents a static strain demodulation technique for FBG-FP sensors using suppressed carrier LiNbO3 (LN) optical single sideband (SSB-SC) modulator. A narrow-linewidth tunable laser source is generated by driving the modulator linear chirp signal. Then this single-frequency used to interrogate with Pound–Drever–Hall (PDH) technique, which beneficial eliminate influence of light intensity fluctuation at different tuning frequencies. The demodulated calculating wavelength difference...

Due to the limit of random optical noise in Rayleigh backscattering and sliding window length, there is a trade-off between sensing spatial resolution accuracy frequency domain reflectometry (OFDR). This paper proposes novel high-spatial-resolution high-accuracy OFDR distributed sensors based on seamless femtosecond weak fiber Bragg grating (WFBG) array. Using laser point-by-point (PbP) inscription technology, 5 cm long array was successfully fabricated polyimide fiber, consisting ten mm...

In optical frequency domain reflectometry (OFDR), the random noise in Rayleigh backscattering and sliding window length algorithm cause a trade-off between sensing spatial resolution accuracy. This paper proposes novel high-spatial-resolution high-accuracy OFDR distributed sensor based on seamless femtosecond weak fiber Bragg grating (WFBG) array. Using laser point-by-point (PbP) inscription technology, 5 cm long array was successfully fabricated polyimide fiber, consisting of ten mm WFBGs....

This paper proposes an approach for acoustic emission (AE) source localization in a large marble stone using distributed feedback (DFB) fiber lasers. The aim of this study is to detect damage structures such as those found civil applications. directional sensitivity DFB laser investigated by calculating location coefficient method digital signal analysis. In this, autocorrelation used extract the from periodic AE and wavelet packet energy calculated get burst source. Normalization processed...

We report on a high-resolution static strain sensor developed with distributed feedback (DFB) fiber laser. A reference FBG resonator is used for temperature compensation. Locking another independent laser to the using Pound-Drever-Hall technique results in power spectral density better than Sε(f) = (4.6 × 10-21) ε2/Hz frequency range from 1 Hz kHz, corresponding minimum dynamic resolution of 67.8 pε/√Hz. This stabilized proposed interrogate sensing DFB by beat principle. As reasonable setup...

This Letter presents an ultrahigh resolution optic fiber strain sensor. A random distributed feedback laser (RDFL) is locked by the proposed frequency-shift Pound-Drever-Hall technique, which tracks resonant frequency change of a π-phase-shifted Bragg grating. The for RDFL gives Lorentzian envelope over original noise, can suppress thermally induced noise. noise reduced from about 100 to 20 Hz/√Hz at 1 kHz. An dynamic 140 fε/√Hz kHz achieved.

Low noise, good consistency, and long-term stability are critical for a multi-channel fiber optic intrusion detection system. This paper proposes low-noise 32-channel interrogator based on phase generation carrier technique, which emphasizes the analysis of key parameters related to system consistency stability. A novel time-division locking technique modulation depth delay is proposed. By simultaneously, interferometric significantly improved. The results show that in system, noise level...

A high resolution fiber-optic acoustic emission (AE) sensor using a random fiber laser (RFL) is proposed. The AE probe undertaken by random-gratings-based erbium-doped RFL. narrow linewidth π-FBG used as wavelength locking and sensing element in the distributed feedback RFL significantly extends effective cavity length of laser, thus reduces thermal frequency noise improves signal. lasing operation with 20 dB ∼10.41 kHz ∼10 Hz/√Hz above 1 realized. 3×3 coupler interrogation technique for...

The train-induced vibration response provides a flexible solution for the real-time monitoring deformation of high-speed railway track slab in actual operation. This paper proposes long-term method based on wavelet packet energy (WPE) using fiber optic accelerometers to record vibration. We found that law could be established by WPE frequency band covering first- and second-order frequencies induced adjacent carriages. A field test was carried out more than one year Beijing–Shanghai...