An improved neural network-based equalization method is proposed and experimentally demonstrated. The up-to-137 Gb/s transmission of four level pulse amplitude modulation (PAM-4) signals with 25 G class 850 nm optical devices is achieved over an in-house fabricated 40 cm optical backplane. An in-depth investigation is conducted regarding the impact of delayed taps and spans on equalization performance. A performance comparison of the proposed method with the traditional maximum likelihood sequence estimation (MLSE) and decision feedback equalization (DFE) is also undertaken. For the bit rate from 80 to 100 Gb/s, the proposed method achieves an adopted hard-decision forward error correction (HD-FEC) requirement at a received optical power (RoP) of −9 and −8 dBm, while DFE and MLSE cannot meet the HD-FEC requirement. When the bit rate increases from 120 to 137 Gb/s, the proposed equalization method still successfully maintains the acceptable system performance at an RoP of −4 and −2.5 dBm. Furthermore, the specific bit error rate (BER) performances for varied maximum achievable bit rate under different RoPs by applying MLSE and the proposed method are also analyzed. This provides an important potential solution to realize the future data centers.

Although pulse compression optical time domain reflectometry (PC-OTDR) exhibits high performance in spatial resolution and dynamic range, it inevitably introduces auto-correlation sidelobes, potentially impacting measurement accuracy. In this letter, an improved CLEAN algorithm is proposed to efficiently suppress sidelobes and enhance the peak-to-sidelobe ratio (PSLR) of signals in PC-OTDR. The proposed method introduces an adaptive step factor instead of the traditional fixed factor to reduce the number of iterations. Compared to the traditional method, the proposed method achieves a 2.87 dB improvement of PSLR from a 10 km sensing fiber. In addition, the computation time cost is significantly reduced, which is 1.92 s less than that of the traditional CLEAN algorithm.

A novel optical fiber sensor that simultaneously measures ultrasound and ultraviolet (UV) radiation was proposed for partial discharge (PD) detection, which is based on Fabry–Pérot interference (FPI) and fluorescence properties. The proposed sensor adopts a Fabry–Pérot structure consisting of a grooved diaphragm and a cerium and terbium co-doped fluorescent (CTDF) fiber. This design employs the grooved diaphragm-based FPI for ultrasound detection, while the lead-in CTDF fiber is specifically utilized for UV radiation detection, minimizing cross-sensitivity between the two due to the distinct detection mechanisms. The parameters of the grooved diaphragm were determined by finite element method (FEM) simulation to precisely tune the resonance frequency of the proposed sensor, ensuring that the proposed sensor meets the sensitivity requirements for effective PD ultrasound detection. Experimental results demonstrate that the proposed sensor is capable of measuring both ultrasound and UV radiation simultaneously, with an ultrasound pressure sensitivity of 23.14 mV/Pa at 34.4 kHz and a UV response sensitivity of 104 mV/( $\mu $ W $\cdot $ cm−2) at 365 nm wavelength. With its compact size, inherent insulation properties, and electromagnetic interference (EMI) resistance, the proposed sensor can be directly installed within high-voltage equipment, demonstrating the significant potential for a wide range of applications in PD detection.

A novel self-adaptive denoising method utilizing optimized empirical wavelet transform (EWT) is proposed to enhance the sensitivity of partial discharge (PD) fluorescence fiber sensors. The optimized EWT enhances the spectrum segmentation capability of conventional EWT via spectral kurtosis (SK). The SK at the optimal window length of noisy PD fluorescence signal is calculated to determine compact support of the Fourier spectrum for subsequent signal decomposition. Frequency components with SK value over the statistic threshold are used to rebuild the PD fluorescence signal. Subsequently, residual noise in the reconstructed signal is removed through adaptive wavelet threshold denoising. To evaluate the performance of the proposed method in denoising numerically simulated and experimentally obtained noisy PD fluorescence signals, outcomes are compared to those of the novel adaptive ensemble empirical mode decomposition (NAEEMD) method, EWT method, EWT joint with kurtogram (KEWT) method, and correlation spectral negentropy (CSNE)-based method. Quantitative metrics and running time are used to assess denoising performance and execution efficiency, respectively. Simulated and experimental results demonstrate that the proposed method possesses a superior noise reduction effect compared to the other four methods while restoring the detail of the PD fluorescence signal flooded by serious noise and consuming reduced computational cost.

We present and demonstrate a compact polarimetric fiber-optic sensor based on Bi₄Ge₃O₁₂ for ultra-high 8/20μs surge current sensing, up to 200kA. Experimental results show that the sensor have a linear sensitivity of 0.385°/kA.

To achieve high-precision demodulation of fiber optic Fabry-Pérot (F-P) ultrasonic sensors over a wide dynamic range, the improved dual-wavelength demodulation technique is proposed. The reference sound signal is introduced to construct the Lissajous figure of the system, and the parameters of the interference signals are obtained using the Ellipse Fitting (EF) algorithm. The Local Outlier Factor (LOF) algorithm is utilized to eliminate outliers from Lissajous figure, obtaining more accurate EF parameters. The proposed dual-wavelength demodulation technique based on prior information overcomes the drawback of the traditional ellipse fitting and differential cross multiplication (EF-DCM) algorithm, which is not not suitable for small signals demodulation. Moreover, it also reduces the influence of system noise and external environment on demodulation results. The experimental results demonstrate that the proposed demodulation technique is suitable for demodulating sensors with arbitrary cavity lengths, and the demodulated phase amplitude and sound pressure exhibit excellent linearity of 0.9989 within the range of 0.20 Pa to 13.36 Pa. The phase sensitivity of the sensor calculated by the improved algorithm is 0.142 rad/Pa.