Characteristics of synthesized light sources for white-light interferometric systems

Abstract

Results of a study on the use of synthesized light sources in white-light interferometry are presented. The optimum wavelength combination with a pair of multimode laser diodes used to generate a synthetic wavelength source was simulated theoretically and verified experimentally. Using the best wavelength combination, we found that the lowest signal-to-noise ratio required by the system was 18.1 dB in theory and 22.1 dB from experiment. The relationships between the wavelengths of the two diodes used, their coherence lengths, and the signal-to-noise ratio required by the system are shown and discussed.

A Review of Recent Developments in Fiber Optic Sensor Technology

“…The interferogram detected during this process yields the sensor OPD by measurement of the receiver OPD at the "central" fringe of the interferogram. An example of this is the work by the group at the City University, London, UK, who have developed a number of readout techniques [57][58][59] for identifying the central fringe using electronically scanned interferograms and by using multiple broadband sources to provide additional structure to the interferogram.Another development in this area is the use of multiwavelength interferometric sensing for discrimination between strain and temperature induced OPD changes. Two groups have recently examined this approach.…”

Optical coherence tomography

“…45 Resolution in the range of one wavelength (and below) can be achieved if the so-called central fringe, i.e., the maximum of the intensity I(d) at the photodetector can be identified. Wang et al 56 describe a technique based on the application of two mutually incoherent sources with different central wavelengths. This technique, however, might only be useful in LCI.…”