2 μm soliton lasers in a bidirectional nonlinear polarization evolution Tm3+-doped fiber oscillator

Funding Information: This work is financially supported by National Natural Science Foundation of China ( 61905150 ; 61805281 ); Fundamental Research Funds for the Central Universities, China (Grant No. 3072022CFJ2501 ; 3072022CF2506 ); Natural Science Foundation of Guangdong Province, China ( 2019A1515010732 ).Peer reviewedPublisher PD

Ultrathin interferometric hydrophone towed line array based on uwFBG

In order to improve the suitability of the fiber hydrophone towing line array, we propose an interferometric hydrophone towed line array with a diameter of 1.7 mm. The line array is an integration of sensitization and package, embedding grating sensors in the composite materials of Kevlar and polyurethane in an additional pultrusion process. The theory and experiment indicate that polymer cladding of pultrusion is an effective way to improve phase sensitivity, increasing mechanical strength and decreasing cable diameter simultaneously. Then, a hydroacoustic detection system, with a quasi-distributed ultra-weak fiber Bragg grating towed line array, based on unbalanced interference is established and its phase sensitivities are tested experimentally. The result is measured by the vibration liquid column method and compared with a standard piezoelectric underwater acoustic detector. Over the frequency range of 200–2000 Hz, the system has a good amplitude–frequency response. We obtain an average phase sound pressure sensitivity of about −147.96 dB (re 1 rad/μPa) and a relative flatness response of 3 dB. The experimental results show that this system provides the possibility of an integrated hydrophone towed linear array with high adaptability and reliability

Pretreatment of Ultra-Weak Fiber Bragg Grating Hydrophone Array Based on Cubic Spline Interpolation Using Intensity Compensation

The demodulation algorithm based on 3 × 3 coupler in a fiber-optic hydrophone array has gained extensive attention in recent years. The traditional method uses a circulator to construct the normal path-match interferometry; however, the problem of increasing the asymmetry of the three-way signal to be demodulated is easily overlooked. To provide a solution, we report a pretreatment method for hydrophone array based on 3 × 3 coupler demodulation. We use cubic spline interpolation to perform nonlinear fitting to the reflected pulse train and calculate the peak-to-peak values of the single pulse to determine the light intensity compensation coefficient of the interference signal, so as to demodulate the corrected three-way interference signal. For experimental verification, ultra-weak fiber Bragg gratings (uwFBGs) with reflectivity of −50 dB are applied to construct a hydrophone array with 800 sensors, and a vibratory liquid column method is set up to generate a low-frequency hydroacoustic signal. Compared to the traditional demodulation algorithm based on a 3 × 3 coupler, the pretreatment method can improve the consistency of interference signals. The Lissajous figures show that cubic spline interpolation can improve the accuracy of monopulse peak seeking results by about 1 dB, and intensity compensation can further lead to a much lower noise density level for the interference pulse amplitude—specifically, more than 7 dB at 5~50 Hz—and the signal-to-noise ratio is improved by approximately 10 dB at 10 Hz. The distinct advantages of the proposed pretreatment method make it an excellent candidate for a hydrophone array system based on path-match interferometry

Transcriptome and Zymogram Analyses Reveal a Cellobiose-Dose Related Reciprocal Regulatory Effect on Cellulase Synthesis in Cellulosilyticum ruminicola H1

The rumen bacterium Cellulosilyticum ruminicola H1 efficiently hydrolyzes cellulose. To gain insights into the regulatory mechanisms of cellulase synthesis, comparative transcriptome analysis was conducted for cultures grown on 2% filter paper, 0.5 and 0.05% cellobiose, and 0.5% birchwood xylan. It was found that cellulose induced a majority of (hemi)cellulases, including 33 cellulases and a cellulosomal scaffoldin (1.3- to 22.7-fold); seven endoxylanases, two mannanases, and two pectatelyases (2- to 16-fold); and pyruvate formate-lyase (PFL, 1.5- to 7-fold). Noticeably, 3- and 2.5-fold increased transcription of a cellobiohydrolase and the cellulosomal scaffoldin precursor were detected in 0.05% than in 0.5% cellobiose. Consistently, 9- and 4-fold higher specific cellobiohydrolase activities were detected in the filter paper and 0.05% cellobiose culture. SDS- and native-PAGE zymograms of cellulose-enriched proteins from the filter paper culture displayed cellulase activities, and cellulolytic “complexes” were enriched from the filter paper- and 0.05% cellobiose-cultures, but not from the 0.5% cellobiose culture. LC-MS/MS identified the cellulosomal scaffoldin precursor in the “complexes” in addition to cellulase, hemicellulase, and PFL proteins. The addition of 0.5% cellobiose, but not 0.05% cellobiose remarkably inhibited strain H1 to degrade filter paper. Therefore, this work reveals a cellobiose-dose related regulatory mechanism of cellulase synthesis by lower for induction and higher for repression, which has extended our understanding of the regulation of microbial cellulase synthesis