Real-time characterisation of the gyroscopic shift in a bidirectional hybrid mode-locked erbium-doped fibre laser

Summary form only given. The prior art of the ultrafast laser gyroscopes goes back to 1981 when R.L. Fork et. al demonstrated colliding-pulse mode-locking [1] and the further discovery of the temporal overlapping of these pulses in 1990 [2]. Direct rotation measurements using laser gyroscopes are known to be more precise compared to the passive fibre optic devices, where the relative phase shift between the beams is retrieved from their interference after propagating in external passive fibre interferometer [3]. The principal limitation of the laser gyroscope sensitivity is the frequency lock-in effect, caused by residual backscattering in the cavity [4]. Ultrafast laser gyroscopes circumvent this effect since the counterpropagating ultrashort pulses interact only in two positions in the cavity and backscattering is reduced by the ultrashort width of the pulse. Here, we present an all-fibre implementation of the ultrafast laser gyroscope, and further propose measuring the gyroscopic shift in the time domain, which results in an order of magnitude improvement in the sensitivity over conventional mode-locked laser gyroscope.