Optimized design of a Figure-9 fiber laser for high-precision time-of-flight ranging

This study targets the need for environmentally robust femtosecond lasers in high-precision time-of-flight (ToF) ranging. A self-starting mode-locked Figure-9 fiber laser with a non-reciprocal phase shifter was designed; the shifter boosts nonlinear interference, enabling self-initiated mode locking and noise suppression. Stable mode locking was achieved at a pump power of 420 mW over a 30° waveplate angle range, yielding a pulse signal-to-noise ratio of 67.347 dB and a phase noise of -120<i>d</i><i>B</i><i>c</i>/<i>H</i><i>z</i>. ToF experiments revealed that compressing the pulse width from 4.18 ps to 798 fs reduced the ranging standard deviation by approximately 75%, underscoring the laser's potential for high-precision ranging and compact, low-noise light source design.