High Resolution Position Measurement of "Flying Particles" Inside Hollow-Core Photonic Crystal Fiber

Optically trapped "flying particles" inside hollow core photonic crystal fiber (HC-PCF) can be used as multi-parameter sensors of, for example, temperature, radiation levels or external electric fields. They represent a new type of optical fiber sensor, offering a spatial resolution that is only limited by the particle size, while being functionally reconfigurable. Here we demonstrate accurate measurement of the axial position of flying particles using incoherent optical frequency domain reflectometry in combination with model-based estimation processing. The approach allows to measure the particle position inside the HC-PCF with a precision of similar to 140 μm

Combined distributed Raman and Bragg fiber temperature sensing using incoherent optical frequency domain reflectometry

Optical temperature sensors offer unique features which make them indispensable for key industries such as the energy sector. However, commercially available systems are usually designed to perform either distributed or distinct hot spot temperature measurements since they are restricted to one measurement principle. We have combined two concepts, fiber Bragg grating (FBG) temperature sensors and Raman-based distributed temperature sensing (DTS), to overcome these limitations. Using a technique called incoherent optical frequency domain reflectometry (IOFDR), it is possible to cascade several FBGs with the same Bragg wavelength in one fiber and simultaneously perform truly distributed Raman temperature measurements. In our lab we have achieved a standard deviation of 2.5 K or better at a spatial resolution in the order of 1 m with the Raman DTS. We have also carried out a field test in a high-voltage environment with strong magnetic fields where we performed simultaneous Raman and FBG temperature measurements using a single sensor fiber only