交叉相位调制提高半导体激光器混沌载波发射机带宽方法

Bandwidth enhancement of a chaotic semiconductor laser transmitter by cross-phase modulation

提出半导体激光器混沌交叉相位调制(XPM)光反馈提高混沌载波发射机带宽方法,建立了有外腔光纤传输反馈XPM控制下的激光动力学物理模型.理论导出XPM作用下激光双反馈频率失谐公式,指出XPM产生的非线性相移影响了激光器增益和线宽增强因子,其光纤二阶非线性效应使激光振幅和相位变化更加丰富,而非线性相移的出现进一步增加了新的频率分量并使频谱展宽.数值结果表明,XPM使激光器混沌带宽增加到4倍以上,使激光混沌张弛振荡频率增加到2.85倍,其光纤长度、入纤光功率、面镜反射系数、光纤二阶非线性系数等都能影响激光混沌带宽.

A novel method of bandwidth enhancement of a chaotic carrier from a semiconductor laser transmitter is studied by cross-phase modulation （XPM）. And a physical model of laser dynamics is presented under the condition of XPM effect of optical fiber path. A frequency detuning formula with optical dual-feedback and XPM effect is deduced. The nonlinear phase shift arisen from XPM effect impacts on the gain and bandwidth enhancement factor of the laser. The second order nonlinear effect of the fiber enriches the varieties in the amplitude and the phase of the laser while the nonlinear phase shift produces a lot of new frequencies,which spread the bandwidth. Numerical results reveal that,with XPM effect,the new bandwidth is the quadruple of the bandwidth without XPM effect,and the relaxation oscillation frequency of the chaotic laser is increased to 2. 85 times that of the laser without XPM effect. It is found that the enhancement of the chaotic bandwidth depends evidently on the optical fiber length,the power input into the optical fiber,the mirror reflectance and the second order nonlinear coefficient.