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This paper presents a fabrication method and results from optical and acoustic characterization of a miniature fiber Fabry-Perot ultrasound detector. A high Q-factor was achieved by creating a self-aligned polymer waveguide within the resonator cavity to restrict diffraction losses. As a result of the improved optical Q-factor upon introduction of the waveguide, a high acoustic sensitivity was achieved. The device presented in this paper demonstrates an optical resonator Q-factor of >2000, and a Noise Equivalent Pressure of 350 Pa over a 25MHz bandwidth on a $125~\mu \text{m}$ fiber with a $9~\mu \text{m}$ waveguide. Sensitivity can be further improved significantly with the use of dielectric mirrors. The high sensitivity of these waveguided fiber Fabry-Perot ultrasound detectors makes them suitable for detection of both ultrasound and photoacoustic signals, while their small size makes this technology suitable for adoption in applications requiring small form factor, such as in interventional cardiology.

UNLABELLED This article investigates a new acoustic device to assess the behaviour of the upper airway in patients with OSA. Currently there is no simple non-invasive method to perform such measurements. As such this paper describes the device in probing the patency of the airway during sleep and increasing the efficiency of diagnosing OSA. BACKGROUND AND OBJECTIVE OSA is a common disorder resulting in health and economic burdens. Currently identifying OSA in patients involves expensive techniques that require overnight studies in a laboratory setting with qualified staff. This paper tests a new acoustic device (AirwayClear (AC)) for assessing upper airway patency in human subjects with OSA. We hypothesize that obstructive apnoeas would be detected equally well with AC and polysomnography (PSG). METHODS Twenty-three patients with severe OSA underwent an overnight CPAP titration study. We introduced pseudorandom noise (600-1200 Hz) using AC to the patient's nasal mask during 1 h of subtherapeutic CPAP. AC determined a measure of airway patency based on the level of pseudorandom noise reaching a sternal notch sensor. The ability of AC to detect obstructive respiratory events was compared with standard PSG. RESULTS Three hundred and twenty-two obstructive events (obstructive and mixed apnoeas) were identified by PSG. AC scored 80% as complete obstructions and 16% as partial obstructions. Conversely, AC detected 281 complete obstructions. PSG recognized 84% as apnoeas and scored 11% as hypopnoeas. Of the 204 hypopnoeas identified with PSG, AC indicated the airway was partially or completely obstructed in 69% of patients. A Bland-Altman analysis for the apnoeas from the two measures showed a mean difference of 2.3 events/h and 95% confidence intervals of +/-15.5 events/h. CONCLUSIONS We conclude that AC is able to track airway patency and to identify airway closure in patients with OSA.