Experimental setup. FFP, fixed Fabry-Pérot etalon; TFP, tunable
Fabry-Pérot etalon; Iso, isolator; SOA, semiconductor optical amplifier;
PC, polarization controller; FRM, Faraday rotating mirror; VOA, variable optical
attenuator; OSA, optical spectrum analyser; FBG, fiber Bragg grating; PD, photo
diode; BPD, balanced photo diode; C, circulator; FC, fiber collimator; G, 2D
Galvanometer mirror set; L, objective lens; S, sample; AOM, acousto-optic
modulator; LO, local oscillator; FG, frequency generator.