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Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements
Published on: February 28, 2016
Specklegram in a multiple-mode fiber and its dependence on longitudinal modes of the laser source
Jun Li1, Haiwen Cai, Jianxin Geng
1Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, China. ljsiom@yahoo.com.cn
Abstract:
A specklegram in a multimode fiber (MMF) has successfully been used as a sensor for detecting external disturbance. Our experiments showed that the sensitivity in the sensor with a multiple longitudinal-mode laser as its source was much higher than that with a single longitudinal-mode laser. In addition, the near-field pattern observations indicated that the coupling between different transverse modes in the MMF is quite weak. Based on the experimental results, a theoretical model for the speckle formation is proposed, taking a bend-caused phase factor into consideration. It is shown in the theoretical analysis that the interferences between different longitudinal modes make a larger contribution to the specklegram signals.

