Design of feedback wavelength demodulation and compensation system for FBG-tuned CW fiber laser

Abstract

The cross-sensitivity of fiber Bragg grating (FBG) always leads to the complexity and instability in its engineering applications, and there are more uncertain factors that affect the center wavelength when FBG is used in fiber lasers as the tunable frequency selector. In order to obtain the stable wavelength of FBG-tuned continuous wave (CW) Er3+-doped fiber laser, we propose and demonstrate a feedback wavelength demodulation and compensation system, which consists of three interrelated parts: a wavelength tuning module controlled by a stepper motor, an all-fiber wavelength demodulation module and a single-chip-based control module. They work cooperatively in a feedback mode and achieve the stabilization of any output laser wavelength in its continuous tunable wavelength range. In the experiment, the output laser wavelength can be locked at the wanted wavelength and be compensated automatically under arbitrary manual tuning in a wide range. When the temperature varies from 10 °C to 40 °C, the laser wavelength shift is less than 0.01 nm for 150 min by real-time compensation, and the corresponding total wavelength shift of ∼0.7 nm is eliminated.