Microstmctured polymer optical fiber sensors for optoacoustic endoscopy

摘要

Intravascular photoacoustics (IVPA) can complement intravascular ultrasound (IVUS) morphological information adding specificity. A practical IVUS/IVPA catheter is mandatory to have a wideband ultrasonic detector with enough sensitivity despite the necessary miniaturization to be fitted in less than 1 mm to pass through thin vasculature. The optical detection of ultrasound provides the compactness, sensitivity and bandwidth required for this application. In this work we compare the ultrasonic detection performance of two FBG sensors inscribed in singlemode microstructured PMMA and TOP AS polymer optical fibers to be integrated as ultrasonic sensor in an IVUS/IVPA catheter. The outer diameters of the fibers are 140 μm. The NEPs obtained were 1.31 kPa and 1. 98 kPa for the 5 mm long PMMA FBG and the 2 mm long TOP AS FBG respectively at 55 MHz detection bandwidth. The directivity and the spectral response are characterized as well. The intrinsic acoustic sensitivity of the TOP AS optical fiber is comparable to the PMMA optical fiber but without any water swelling effects associated to the last one what cause a slow FBG central wavelength drift over several hours when the sensor is immersed in water. The use of TOP AS mPOF is an improvement in terms of robustness and usability of this kind of ultrasound sensors based on FBGs in polymer optical fibers.