Optical coherent tomography system based on a self-calibrated swept source for applications requiring distances measurements over the centimeter

ENEAS N. MOREL; NELIDA ARACELI RUSSO; JORGE TORGA; RICARDO DUCHOWICZ

Praga

Conferencia; Conference on Non Destructive Testing (OCTNTD 2014); 2014

Industrial applications requiring the measurement of distances of the order of a centimeter or more with optical coherent tomography techniques are currently little explored but offer a great potential with the development of long range OCT-systems [1,2]. Most employed configurations present some drawbacks to extend the axial range to these values. In Fourier domain (FD)-OCT this limitation is due to the finite spectral resolution of the detection system and in swept source (SS)-OCT the limitation is given by the instantaneous line-width of the source. In this work we present a new set-up based on an all-fiber tunable erbium ring laser operating in the range of 1520-1570 nm. The configuration employs a tunable Fabry-Perot filter with a free spectral range of 60 nm and a bandwidth of 60 pm. A set of Bragg gratings were included in the interferometer to perform real time calibration of the interference signal. With this configuration an axial range up to 7 cm. were demonstrated. The measurements were made by moving a glass window (BK7) with a linear stage. A detailed analysis of the experimental scheme is shown and results of the spatial resolution and signal to noise ratio are presented