The digitization of smart catheters will dramatically increase the demand for reliable and high data transmission in the distal tips. Optical fiber is a good candidate to provide high-speed data transmission. However, the extremely small size of the smart catheter tip, with less than a few millimeters in diameter, hampers the integration of optical fiber connections in the catheter tip. Our work presents a stand-alone optical data link module (ODLM) with a dimension of 240 μm × 280 μm × 420 μm for use in a 1 mm diameter intravascular ultrasound (IVUS) smart catheter. The fabrication of the ODLM is based on the Flex-to-Rigid (F2R) integration technology. In the ODLM, the flexible interconnects reroute the electrical contacts of the flip-chipped vertical-cavity sur-face-emitting laser (VCSEL) to the side of the device. This design enables the ODLM to be mounted on a flex-PCB and fit into a 200-300 μm gap in the IVUS catheter tip. An optical fiber that runs parallel to the catheter shaft is self-aligned to a commercially available VCSEL by inserting it into the through-silicon hole (TSH) of the ODLM. Clear eye diagrams prove the stand-alone ODLM can transmit 25.8 Gb/s, 231-1 Pseudo-Random Binary Sequence (PRBS) when driven through a high-speed bias-tee. The BER test indicates that error-free operation can be achieved at an optical output of around -4 dBm.

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Intravascular ultrasound (IVUS) is a well-established diagnostic method that provides images of the vessel wall and atherosclerotic plaques. We investigate the potential for phased-array IVUS utilizing coded excitation (CE) for improving the penetration depth and image signal-to-noise ratio (SNR). It is realized on a new experimental broadband capacitive micromachined ultrasound transducer (CMUT) array, operated in collapse mode, with 96 elements placed at the circumference of a catheter tip with a 1.2- {mm} diameter. We characterized the array performance for CE imaging and showed that the -6-dB device bandwidth at a 30-V dc biasing is 25 MHz with a 20-MHz center frequency, with a transmit sensitivity of 37 kPa/V at that frequency. We designed a linear frequency modulation code to improve penetration depth by compensating for high-frequency attenuation while preserving resolution by a mismatched filter reconstruction. We imaged a wire phantom and a human coronary artery plaque. By assessing the image quality of the reconstructed wire phantom image, we achieved 60- and 70- mu{mathrm {m}} axial resolutions using the short pulse and coded signal, respectively, and gained 8 dB in SNR for CE. Our developed system shows 20-frames/s, pixel-based beam-formed, real-time IVUS images.

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We demonstrate a stand-alone optical data link module (ODLM) that fits in the limited space budget of smart imaging catheters. The module is based on an extension of the Flex-to-Rigid (F2R) technology platform for miniaturized system integration. The ODLM is a silicon-based interposer that comprises a commercially available Vertical Cavity Surface Emitting Laser (VCSEL), which has its electrical contacts and laser emitting spot on the same surface. With the flexible interconnects, the ODLM reroutes the flip-chipped VCSEL electrical contacts to the side that is perpendicular to the surface of the VCSEL. This enables the ODLM to be mounted on a flex-PCB and fit into the limited space in the distal tip of the smart catheter. An optical fiber that runs in parallel to the catheter shaft is inserted into the through-silicon hole (TSH) of the ODLM and self-aligned to the VCSEL for optical data transmission. The design of the ODLM and the F2R technology platform are introduced, and an ODLM demonstrator is fabricated and presented.@en