Han Qun

A Powerful Simple Shooting Method for Designing Multi-Pumped Fibre Raman Amplifiers

A simple shooting method dedicated to the design of multipump discrete Raman fibre amplifiers (RFAs) is proposed and discussed in detail. A novel scheme to provide a good initial guess for backward lightwaves is also proposed to improve the efficiency and robustness of the method. Using the proposed method, a discrete RFA with four backward pumps and 93 signal channels is simulated for the maximum number of interaction waves considered simultaneously in the RFA design reported previously, to our best knowledge. The numerical simulation results show that the proposed method is fast and robust. It can be used in the design of RFAs with various configurations including co-, counter- and bi-directional-pump schemes to provide an actual modelling.

All-fiber optical modulator based on no-core fiber and magnetic fluid as cladding

An all-fiber optical modulator, which is composed of a piece of no-core fiber spliced between two sections of single-mode fibers and uses magnetic fluid (MF) as the cladding of the no-core fiber section, is proposed and investigated experimentally. Due to the tunable refractive index and absorption coefficient of MF, the output intensity can be modulated by controlling an applied magnetic field. The dependences of the modulator’s temporal response on the working wavelength, the magnetic field strength (H), and the MF’s concentration are investigated experimentally. The results are explained qualitatively by the dynamic response process of MF under the action of a magnetic field. The findings are helpful for optimizing this kind of modulator.

Response of a Duffing—Rayleigh system with a fractional derivative under Gaussian white noise excitation

In this paper, we consider the response analysis of a Duffing–Rayleigh system with fractional derivative under Gaussian white noise excitation. A stochastic averaging procedure for this system is developed by using the generalized harmonic functions. First, the system state is approximated by a diffusive Markov process. Then, the stationary probability densities are derived from the averaged Ito stochastic differential equation of the system. The accuracy of the analytical results is validated by the results from the Monte Carlo simulation of the original system. Moreover, the effects of different system parameters and noise intensity on the response of the system are also discussed.

A Novel Method for Multi-Pumped Fibre Raman Amplifier Gain Adjustment

A novel method for gain adjustment of multi-pumped fibre Raman amplifiers is proposed and numerically demonstrated. The method uses the areas under the curves of the pump power evolution along the gain fibre and the Newton–Raphson method to find an appropriate power combination of the pumps to realize the desired gain profile. Compared with the previously proposed methods, our method has two advantages: first, it can maintain the gain profile while changing the gain magnitude to the desired value; second, it is independent of the actual pumping scheme of the amplifier, i.e. it can be used for fibre Raman amplifiers with all kinds of pumping schemes including co-, counter-, or bi-directional pumping. Numerical simulations are provided to verify the proposed method and to demonstrate its effectiveness.

Near-Infrared Spectroscopic Properties and Judd-Ofelt Theory Analysis of Er3+/Yb3+Co-Doped Fluoride Particles

制备了Er^3＋/Yb^3＋共掺氟化物基质颗粒并对其吸收光谱进行测试。研究了不同基质、煅烧温度以及不同的Er^3＋/Yb^3＋共掺比例对颗粒在980nm及1550nm波段附近吸收特性的影响。应用Judd-Ofelt（J-O）理论对样品光谱进行了分析,拟合得到强度参数为Ω2=9.9887,Ω4=2.7333,Ω6=0.4868。结果表明,样品通过高温热处理提高了声子辅助跃迁几率,提高了能量转化效率。Er^3＋/Yb^3＋以1：6比例混合共掺时吸收性能最好。J-O理论分析表明,氟化物颗粒有较低的声子能量,Er^3＋/Yb^3＋共掺氟化物材料具有较好的红外吸波特性,是一种很好的红外上转换材料。

High Power Er/Yb Codoped Double Clad Fiber Pulsed Amplifier Based on an All-Fiber Configuration

We report an all-fiber two-stage high power pulsed amplifier, seeded with a 1550 nm, 1 kHz repetition rate rectangular pulse, and based on Er/Yb co-doped double clad fiber. All the characteristics are measured in the experiment. The maximal slope efficiency is 22.56%, which is the highest we know of at such a low repetition rate, and the maximal output signal power is 1W. The various factors that affect the pulsed amplifier performance are analyzed. A high output power while keeping high power conversion efficiency can be obtained with careful selection of the input power, pump power and repetition rate. The experimental results show that the crucial parameters should be optimized when designing all-fiber pulsed amplifiers.

A New Method to Analyse Two-Side Tapered Waveguides

We discuss the characters of two-side tapered waveguides. Then, based on some approximations, a simple but practical and efficient method is developed to design the taper waveguide. The results are compared with other methods in a good agreement.