PERFORMANCE ANALYSES OF AN INFRARED SINGLE-MODE ALL-FIBER-OPTIC FOURIER-TRANSFORM SPECTROMETER

Stretching one of a pair of fiber arms can be done to realize optical phase modulation for an IR single-mode all-fiber-optic Fourier-transfo rm spectrometer (FTS), But this operation will inevitably limit the ph ysical performance of a FTS. We study these limits theoretically and e xperimentally. The optical path difference (OPD) will be dispersive. A t the first-order approximation, this OPD dispersion will result in a shift in the recovered spectra. The spectral resolution and the sampli ng distance will also be dispersive. Linear birefringence introduced w hen a curved fiber is stretched will affect the final spectra. This ef fect can be eliminated by real-time compensation and (or) by system de sign. Errors encountered uniquely in the all-fiber-optic FTS in the op tical phase domain, such as the fiber-parameter errors, nonlinearity o f the piezoelectric cylinder, and their effects on the spectra are ana lyzed, from which we deduce the requirements for calibration. Finally, calibration methods for optical phase modulation are discussed.