The optical fiber itself can function as a partially reflecting concentric cavity interferometer when transversely probed by a focused laser beam. In this study, the thermal response of the fiber heated by a CO2-laser beam was characterized by monitoring the back-scattered interference pattern. Simultaneous measurement of the Bragg wavelength shift of an inscribed, high-temperature stable fiber Bragg grating allowed for calibration of the temperature-dependent phase response of the interferometer. The presented technique allows for in-situ non-contact temperature measurements up to the glass softening point.

A quadrature phase-shift detection system for interferometry has been conceptualized and evaluated. The main components, a microcontroller and two photodetectors, make a versatile low-cost detection system for displacement measurements or more generally phase-change measurements. The system is capable of sampling at 5 kHz with a spatial resolution of 1 nm.& nbsp;

An experimental, laboratory-scale optical fiber drawing tower based on CO laser heating has been developed and used to fabricate speciality optical fiber. The CO laser was utilized in a symmetric four beam heating system. The localized and responsive heating time of the laser-based furnace was beneficial for manufacturing crystalline core fibers, specifically, silicon core optical fibers. Moreover, the specific absorption properties of the CO laser radiation in silica have been evaluated with the aid of finite element modeling. In comparison to the more traditional CO2 laser, CO lasers were found to improve temperature uniformity and heating times while minimizing surface evaporation.

A Mach-Zehnder interferometer is formed in the transverse plane of an optical fibre. This is exploited to monitor the temperature of any given optical fibre in real time, without any predesigned temperature sensing elements engineered into the fibre and without a need to access the fibre ends. The interferometer is formed by the refraction at the air-glass interface and the subsequent internal reflections within the fibre. The temperature response of the fibre is then measured by quadrature phase shift detection of the interference pattern. For context, this is compared to finite element modelling and a previously studied Fabry-Perot interferometer configuration. The temperature of an optical fibre was measured from room temperature up to 1174 degrees C with an error of +/- 2.6% for the Mach-Zehnder type interferometer. The measurement techniques presented offer a useful tool for precise temperature measurement for applications such as fibre post-processing.

Silicon core fibers are a promising candidate for optoelectronic and photonic applications. Fabrication and post-processing of those fibers is thus far done without precise knowledge of the processing temperatures. Here, a simple technique is presented that allows for in-situ temperature monitoring during thermal processing of silicon core fibers. The temperature was probed across the silicon melting point and cooling rates above 3500 degrees C s(-1) were measured. The silicon core was found to be molten at a temperature of 1281 degrees C, more than 100 degrees C below the bulk silicon melting point. This is attributed to stress inbuilt to silicon core fibers during the fabrication process.