High finesse tunable Fabry-Perot filters in Fourier-domain modelocked lasers

We demonstrate that the coherence roll-off and dynamic range of OCT systems using Fourier-domain mode-locked (FDML) lasers can be significantly improved by a high-finesse fiber Fabry-Perot tunable filter (FFP-TF). The newly developed high-finesse FFP-TFs have a finesse of more than 3000, a more than fivefold improvement over previous designs. We show that this results in reduced instantaneous laser linewidth and reduced noise for a 1310 nm FDML laser with 1.6 MHz sweep rate. Since in practice, OCT image range is limited by data acquisition bandwidth, we demonstrate OCT imaging over many centimeters by reducing the sweep range of the laser. In contrast to previous work, standard resampling using a pre-acquired signal (as in SD-OCT) with no k-clocking is sufficient for both small and large sweep range, significantly reducing the system complexity. Live 3D-OCT video rate imaging at 20 cm imaging range is demonstrated.