Analysis of the measurement error in wavelength shift measurement systems for optical sensor applicaiton

摘要

The measurement error in an interferometric scheme for wavelength measurement in optical sensing applications such as those using in-fibre Bragg gratings has been analyzed and simulated. It has been shown that when a lock-in amplifier is employed to detect the phase change generated by the Bragg wavelength shift, a pseudo-periodical measurement error can be introduced due to the difference between th4e amplitude of the associated optical path difference ramp and the value of the Bragg wavelength. If the initial ramp deviation equals 20nm, the measurement error may be as large as 5percent of the total measurement range. By using the double-phase lock-in amplifier to measure the AC strain in the instrumental system, the measurement error can be decreased to 0.4percent of the total measurement range.