A corrugated silver diaphragm-based optical fiber microphone (OFM), formed by extrinsic Fabry-Perot interferometric structure, was proposed. The sensor's sensitivity was improved by releasing diaphragm's initial stress with the help of corrugations. A simple ``gray-scale exposure'' method was proposed to fabricate the corrugation. Experimental results indicated that the mechanical sensitivity of the fabricated corrugated diaphragm (CD) was 52 nm/Pa, which was twice that of the planar diaphragm under the same parameters. Other characteristics of the fabricated microphone were also tested in detail. The proposed CD-based OFM showed the advantages of high sensitivity, simplicity and low cost, which was expected to be applied in the field of weak acoustic sensing.

In this paper, an all-sapphire fiber-optic Fabry-Perot (F-P) pressure sensor is proposed. The sapphire pressure-sensitive diaphragm with low surface roughness is fabricated by MEMS wet etching. The direct bonding process is adopted to bond the sapphire-sensitive diaphragm and substrate together. And the sapphire fiber is adopted to be the lead-in fiber to ensure the sensor’s resistance to high temperature. The performance of the sensor is tested within a pressure range of 0.1 ∼ 5 MPa and within the temperature range from room temperature to 1200°C. Experimental results show that the sensor could work stably at the temperature of 1200°C. The pressure sensitivity reaches up to 15nm/MPa. The nonlinearity of the sensor is 0.96% FS (full scale), and the relative resolution reaches 0.12%FS. The all-sapphire F-P sensor could be used for high-pressure testing in a high-temperature environment.

We present a dual-wavelength off-axis quasi-common-path digital holography for quantitative phase imaging using polarization-multiplexing in a single shot. Employing an off-axis nearly common-path configuration, our approach separates the two-wavelength information using a polarizing beam splitter, while modulates the orthogonal fringe directions for each wavelength using two retro-reflector mirrors, and thus generates a single multiplexed off-axis interferogram on a monochrome CCD camera. The information of a specimen, including phase and height, is reconstructed through a division algorithm for dual wavelengths with the help of a specimen-free multiplexed interferogram. The experimental results obtained on a square step target and a circular step target illustrate the validity and stability of our setup.

A high-sensitivity cross-axial extrinsic fiber Fabry-Perot interferometric acoustic sensor with a 45° angled fiber is proposed. The thickness of pressure-sensing silver diaphragm is 95 nm. The diameter is 1.6 mm yet the flatness of the diaphragm is <;30 μm. The measured dynamic sensitivity of the diaphragm is 67.01 nm/Pa. The sensor exhibits a flat frequency response in the range of 1-6 kHz and a dynamic range of 66.43 dB. The minimal detectable pressure is ~107 μPa/Hz1/2 at 3 kHz. The fabricated sensor is expected to be useful for highly sensitive acoustic measurement.