Numerical simulation of four-wave mixing efficiency and its induced relative intensity noise

Four-wave mixing, as well as its induced intensity noise, is harmful to wavelength division multiplexing systems. The efficiency and the relative intensity noise of four-wave mixing are numerically simulated for the two-wave and the three-wave fiber transmissions. It is found that the efficiency decreases with the increase of both the frequency spacing and the fiber length, which can be explained using the quasi-phase-matching condition. Furthermore, the relative intensity noise decreases with the increase of frequency spacing, while it increases with the increase of fiber length, which is due to the considerable power loss of the pump light. This investigation presents a good reference for the practical application of wavelength division multiplexing systems.

Investigation on the intensity noise characteristics of the semiconductor ring laser

Based on the frequency-domain multimode theoretical model, detailed investigations on the noise characteristic of the semiconductor ring laser （SRL） are first performed in this paper. The comprehensive nonlinear terms related to the third order nonlinear susceptibility Z3 are included in this model; the Langevin noise sources for electric field and carrier density fluctuations are also taken into account. As the injection current increases, the SRL may present several operation regimes. Remarkable and unusual low frequency noise enhancement in the form of a broad low frequency tail extending all the way to the relaxation oscillation peak is observed in any of the operation regimes of SRLs. The influences of the backscattering coefficient on the relative intensity noise （RIN） spectrum in typical operation regimes are investigated in detail.

Using Ambient Noise to Study the Seismic Velocity Changes Caused by the Rise and Fall of the Water Level in the Zipingpu Reservoir Region

We study the feature of media changes beneath the Zipingpu reservoir and discuss the process of permeation with the water level rise and fall of the reservoir from January 2005 to January 2008 from ambient noise cross correlation by using continuous seismic data recorded by the stations of Zipingpu seismic network and YZP station. A moving-window cross-spectrum technique has been used to calculate the relative seismic velocity changes between station pairs. Results revealed an obvious relationship between relative seismic velocity, and the water level changes with a time delay that may be caused by permeation during three main impoundments and two large scale disemboguements. Impoundment generates a fast and large impact on the superficial layer, and the changes of seismic velocity is the result of increased pressure and permeation during the impoundment. At the first impoundment, the main effect factor is pressure. During the next two process of impoundment, permeation becomes the main effect factor, affecting the fault at a depth of about 8kin.

Quality analysis of crustal tilt and strain observations in China's earthquakes in 2014

This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmeters presented the highest rate of excellent quality,approximately 91%, and the pendulum tiltmeters and ground strainmeters yielded rates of81% and 78%, respectively. This means that a total of 380 sets of instruments produced high-quality observational data suitable for scientific investigations and analyses.

Relative intensity noise in high-speed hybrid square-rectangular lasers

Relative intensity noise(RIN) and high-speed modulation characteristics are investigated for an Al Ga In As/In P hybrid square-rectangular laser(HSRL) with square side length, rectangular length, and width of 15,300, and 2 μm, respectively. Single-mode operation with side-mode suppression larger than 40 dB has been realized for the HSRL over wide variation of the injection currents. In addition, the HSRL exhibits a 3 dB modulation bandwidth of 15.5 GHz, and an RIN nearly approaches standard quantum shot-noise limit 2 hv∕P=-164 dB∕Hz at high bias currents due to the strong mode selection of the square microcavity. With the increase of the DC bias current of the Fabry–Perot section, significantly enhanced modulation bandwidth and decreased RIN are observed.Furthermore, intrinsic parameters such as resonance frequency, damping factor, and modified Schawlow–Townes linewidth are extracted from the noise spectra.

Two-Mode Biomedical Sensor Build-up:Characterization of Optical Amplifier

Intracavity absorption spectroscopy is a strikingly sensitive technique that has been integrated with a two-wavelength setup to develop a sensor for human breath.Various factors are considered in such a scenario,out of which Relative Intensity Noise(RIN)has been exploited as an important parameter to characterize and calibrate the said setup.During the performance of an electrical based assessment arrangement which has been developed in the laboratory as an alternative to the expensive Agilent setup,the optical amplifier plays a pivotal role in its development and operation,along with other components and their significance.Therefore,the investigation and technical analysis of the amplifier in the system has been explored in detail.The algorithm developed for the automatic measurements of the system has been effectively deployed in terms of the laser’s performance.With this in perspective,a frequency dependent calibration has been pursued in depth with this scheme which enhances the sensor’s efficiency in terms of its sensitivity.In this way,our investigation helps us in a better understanding and implementation perspective of the proposed system,as the outcomes of our analysis adds to the precision and accuracy of the entire system.

Relations between pulsed jet noise and steady jet noise

On the hypothesis that the turbulent flow is practically not affected in character by pulsation of the flow, the formula for sound pressure level of pulsed jet noise is obtained in 90 °direction and 1 meter away from the nozzle. The steady jet noise is , then, a special case when the pulsating frequency is zero. The results agree well with experiments.

Cascaded Random Raman Fiber Laser With Low RIN and Wide Wavelength Tunability

Cascaded random Raman fiber lasers(CRRFLs)have been used as a new platform for designing high power and wavelength-agile laser sources.Recently,CRRFL pumped by ytterbium-doped random fiber laser(YRFL)has shown both high power output and low relative intensity noise(RIN).Here,by using a wavelength-and bandwidth-tunable point reflector in YRFL,we experimentally investigate the impacts of YRFL on the spectral and RIN properties of the CRRFL.We verify that the bandwidth of the point reflector in YRFL determines the bandwidth and temporal stability of YRFL.It is found that with an increase in the bandwidth of the point reflector in YRFL from 0.2 nm to 1.4 nm,CRRFL with higher spectral purity and lower RIN can be achieved due to better temporal stability of YRFL pump.By broadening the point reflector’s bandwidth to 1.4 nm,the lasing power,spectral purity,and RIN of the 4th-order random lasing at 1349 nm can reach 3.03 W,96.34%,and–115.19 dB/Hz,respectively.For comparison,the spectral purity and RIN of the 4th-order random lasing with the point reflector’s bandwidth of 0.2 nm are only 91.20%and–107.99 dB/Hz,respectively.Also,we realize a wavelength widely tunable CRRFL pumped by a wavelength-tunable YRFL.This work provides a new platform for the development of ideal distributed Raman amplification pump sources based on CRRFLs with both good temporal stability and wide wavelength tunability,which is of great importance in applications of optical fiber communication and distributed sensing.