Fig. 1.

Schematic of the dual-modality OCT + fluorescence imaging system with asymmetric double-clad fiber coupler and MI needle (inset). SS, swept source; WDM, wavelength-division multiplexing coupler; SMF-28, single-mode fiber; MMF, multimode fiber; DCF, double-clad fiber; DCFC, double-clad fiber coupler; EF, long-pass emission filter; BF, blocking filter; PMT, photomultiplier tube; SIF, step-index fiber; GRIN, gradient-index fiber; NCF, no-core fiber; VOA, variable optical attenuator; BD, balanced photodetector; DAQ, data acquisition.