Tunable dual-frequency erbium-doped fiber laser using two PS-FBGs and 100 MHz beating frequency

A tunable dual-frequency fiber laser is a crucial in a precision measurement system, significantly influencing measurement accuracy and cost. Consequently, a low beating frequency is preferred in many applications, such as coherence measurement. This paper demonstrates a novel, to our knowledge, dual-frequency, erbium-doped fiber laser, utilizing the Vernier effect and dual phase-shifted fiber Bragg gratings (PS-FBGs), with a beating frequency of 300 MHz. By adjusting the axial strain applied to the PS-FBG, the beating frequency can be tuned up to 1200 MHz. Additionally, altering the cavity length can reduce the beating frequency to 144 MHz.