Cascaded multicore fiber interferometers for enhanced bending sensing based on the Vernier effect.

In this paper, cascaded modal interferometers constructed by strongly-coupled seven-core fiber (SC-SCF) with different lengths are demonstrated for enhanced bending sensing based on Vernier effect. The free spectral range (FSR) of a single SC-SCF interferometer is determined by the length of SC-SCF. Two SC-SCF interferometers with different FSRs are cascaded, in which, one functions as the sensor while the other functions as the reference. The wavelength shift of the envelope of the output spectrum is much larger than that of a single SC-SCF interferometer due to the Vernier effect. Therefore, enhanced sensing can be achieved. Experimental results show that the bending sensitivity of the proposed sensor is improved from -2.20 nm/m-1 (single SC-SCF interferometer) to 42.32 nm/m-1 (cascaded SC-SCF interferometers). The temperature response of the sensor is also investigated. Our proposed cascaded SC-SCF sensor has advantages of high sensitivity, ease of fabrication, and low cost. It is attractive for high precision bending sensing applications.

Supermode Bragg grating inscribed in a strongly coupled seven-core fiber and its responses to temperature and curvature.

A Bragg grating is successfully inscribed in a piece of strongly coupled seven-core fiber (SCF). There are two separate Bragg resonance notches observed in the transmission spectrum, corresponding to backward coupling of HE11-like and HE12-like supermodes of the SCF. The mode coupling mechanism of the Bragg grating is theoretically investigated via modeling and analyzing modal properties of the SCF. The theoretical results agree well with the experimental results. Since the SCF is spliced between two standard single mode fibers with central alignments at both ends, the transmission spectrum of the device also contains a set of interference fringe due to modal interference between the supermodes. The device's responses to temperature and curvature are experimentally measured, respectively. The obtained temperature sensitivities and curvature sensitivities of the supermode Bragg grating notches are 9.55 pm/°C and 9.55 pm/°C, -1.8 pm/m-1 and -112.3 pm/m-1, respectively. The obtained temperature sensitivity and curvature sensitivity of one of the interference spectrum dips are 11.8 pm/°C and -3909.8 pm/m-1, respectively. This device is potentially useful for simultaneous measurement of temperature and curvature.

Splenic Artery Pseudoaneurysm in Chronic Pancreatitis Causing Obstructive Jaundice: Endovascular Management.

BACKGROUND: Splenic artery pseudoaneurysm (SAP) around the pancreatic head causing obstructive jaundice is an extremely rare complication but can be life threatening once occurs. This case report is to raise awareness of this catastrophic complication and share our experience of successful endovascular management. METHODS: A 47-year-old male with a history of chronic pancreatitis clinically presented with epigastric pain and jaundice. Proximal SAP complicated with obstructive jaundice was confirmed by laboratory and imaging investigations. The SAP was successfully treated by transarterial coil embolization, and the jaundice subsequently improved. RESULTS: Abdominal contrast-enhanced computed tomography 11 months after embolization showed complete occlusion and reduction in the volume of the SAP as well as normal biliary tract. CONCLUSIONS: SAP complicated with obstructive jaundice should be managed timeously and aggressively once diagnosed, given its potential adverse consequences. Transarterial embolization using the isolation technique may be a safe and effective strategy for treating this disease.

Endovascular Management of Isolated Superior Mesenteric Artery Dissecting Aneurysm by Retrograde Catheterization Via Collaterals from the Celiac Artery.

Isolated superior mesenteric artery (SMA) dissecting aneurysm is frequently symptomatic and potentially catastrophic; thus, it usually requires endovascular treatment. The endovascular management can be challenging in certain cases as catheterization of the collapsed true lumen is often very difficult. This case report is to describe a new approach for catheterization of the true lumen of the SMA in a case of isolated SMA dissecting aneurysm. A 63-year-old male with an SMA dissecting aneurysm underwent stent-graft placement for treatment. Catheterization of the true lumen via the anterograde approach was unsuccessful because of angulation and collapse of the SMA true lumen as a result of the dissecting aneurysm. A guidewire was passed through the collaterals from the celiac artery and retrogradely passed across the collapsed SMA true lumen into the aorta. We then used a snare that had been delivered through the contralateral femoral access to capture and retrieve the guidewire. A delivery system was advanced into the SMA, and a stent graft was successfully deployed to occlude the dissecting aneurysm. This report introduces a new feasible retrograde approach that provides access to the SMA true lumen via celiac collaterals in cases of difficult antegrade catheterization of an SMA dissecting aneurysm.