Figure 1

(a) The unbalanced-arm fiber interferometer for FT spectroscopy by fr-sweeping; fr: pulse repetition rate, DFB LD: distributed feedback laser diode, FBG: fiber Bragg grating, C: fiber coupler, DCF: dispersion-compensation fiber, BPDFTS: balanced photo-detector to monitor the interferogram of the femtosecond laser source, BPDDFB: balanced photo-detector to monitor the homodyne interference signal of DFB LD, LPF: low-pass filter. (b) Sampling of an interferogram with fr-sweeping. (c) Frequency resolution vs. unbalance arm length for various fr-sweeping ranges (Δfr).