Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on.

This paper proposes a multi-path multi-sensor architecture for CMOS magnetic sensors, which effectively extends their bandwidth without compromising either their offset or resolution. Two designs utilizing the proposed architecture were fabricated in a 0.18 μm standard CMOS process. In the first, the combination of spinning-current Hall sensors and non-spun Hall sensors achieves an offset of 40 μT, and a resolution of 272 μTrms in a bandwidth of 400 kHz, which is 40x more than previous low-offset CMOS Hall sensors. In the second, the combination of spinning-current Hall sensors and pick-up coils achieves the same offset, with a resolution of 210 μTrms in a further extended bandwidth of 3 MHz, which is the widest bandwidth ever reported for a CMOS magnetic sensor.

We describe a cost effective scheme to automatically separate two polarization channels in a polarization division multiplexing (PDM) system, without having to modify the existing transmitter or receiver electronics or software. We experimentally validate the concept by achieving an extinction ratio of more than 28-dB between two demultiplexed channels. Finally, we successfully demonstrate the PDM scheme in a 1.12-Tb/s (14x2x40-Gb/s) system over 62-km of transmission fiber.

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