Qiheng He

Polarization-modulated random fiber laser

In this letter, we propose and experimentally demonstrate a polarization-modulated random fiber laser (RFL) for the first time. It is found that the output power of the half-opened RFL with polarized pumping is sensitive to the state of polarization (SOP) of the Stokes light in a fiber loop acting as a mirror. By inserting a polarization switch (PSW) in the loop mirror, the state of the random lasing can be switched between on/off states, thus such a polarization-modulated RFL can generate pulsed output with high extinction ratio.

Long-distance random fiber laser point sensing system incorporating active fiber

In this paper, we investigate the benefits of introducing the active fiber into long-distance point-sensing system based on random fiber laser (RFL). In this scheme the active fiber is placed between two segments of single mode fiber (SMF) and backward RFL pumping scheme is used. Through the numerical analysis, the influence of active fiber location on the spectral and power performance for the RFL is carefully discussed. Compared with the scheme without active fiber, the lasing threshold is much lower and the optical signal to noise ratio (OSNR) of the lasing line can be much higher, and the location of the active fiber has significant flexibility. The RFL experimental results are well coincident with the theoretical analysis; also, the sensing performance of such a system is demonstrated.

Long-range BOTDA denoising with multi-threshold 2D discrete wavelet

Multi-threshold 2D discrete wavelet based on BayesShrink method is utilized to enhance the SNR of BOTDA. Then a 154.42 BOTDA is experimentally demonstrated with 40ns pump pulses, and the measurement uncertainty is reduced from ±1.52MHz down to ±1.03MHz.

1.5 μm low threshold, high efficiency Erbium-Raman random fiber laser

We report a low threshold, high efficiency random fiber laser with hybrid Erbium-Raman gain. The numerical analysis is made to describe the power performance of the proposed Erbium-Raman random fiber laser and reveal the high efficiency generation in this simple configuration. Thanks to the hybrid gain, the experimentally achieved laser threshold has been reduced to 60 mW. The optical conversion efficiency is of record high in the 1.5 μm regime, reaching 61.5% when pump power is 2 W. This work provides an effective way to generate high efficiency stable 1.5 μm random lasing, which could have important applications in optical fiber sensing and communication.

Non-local means denoising based on noise level estimation for BOTDA

A noise level estimation algorithm based on selected weak patches is utilized to ensure the non-local means denoising performance for Brillouin optical time domain analyzer (BOTDA). We firstly study the accuracy of proposed method by simulation. Then, we use non-local means to process the experimental data with different estimation method, proving the reliability of proposed approach.