Lossless in-line laser power monitoring in high-power fiber lasers

To ensure safe and stable operations of a high-power fiber laser, real-time laser power monitoring is essential. But, current monitoring methods are typically qualitative and can only be used for system fault/failure alarms. In this work, we propose a lossless in-line fiber-tapping approach for quantitative real-time sensing of laser power. This fiber tap is designed to sample a small amount of light remaining in the cladding of the laser output fiber (a double-clad fiber). After the sampled light passes through a long-pass filter in front of the photodetector, the power of the sampled signal part is measured. Experiments show that there is a good proportional correlation between the sampled signal power and the laser output power.