Uporaba telekomunikacijskih laserskih diod za določitev merilne vrednosti pri spektralno razločljivih optičnih vlakenskih senzorjih : doktorska disertacija

slovenian

doktorska dela

2013

Univerza v Mariboru, Fakulteta za elektrotehniko računalništvo in informatiko

Interrogation of the spectrally resolved fiber optic sensors is still highly complex and consequently expensive, therefore, usage of the fiber optic sensors is limited to applications where other sensors can not be used. Because of this reason there is demand for simpler and more cost effective interrogation systems that would allow for fiber optic sensors to get in wideruse. Possible solution presented in this thesis use standard telecommunication opto-electronic elements that are widely availible and enable construction of simple interrogation systems for the spectrally resolved fiber optic sensors. In this dissertation, two novel interrogation systems for fiber optic sensors that are based on standard telecommunication opto-electronic components are introduced. A DWDM laser module can be used as a spectrometer wherein an DFB laser diode serves as tunable laser source, and wavelength locker enables measurement of output wavelength. Such usage enablesdetermination of fiber optic sensor spectral characteristic which carries information about measured parameter. It is shown that such laser module can achieve spectral resolution better than 1 pm which is equivalent to0.1 °C for temperature measurements and 1 ? for strain measurements. The interrogation system allows for sampling rate of 45 Hz which is suitable for static measurements. Cost effective solution furthermore offers usage of a standard telecommunication DFB laser diodes which are excited by high current short duration pulses. High density of free carriers causes heat of laser diodes active region which further causes shift of output wavelength that is higher than 10 nm. By time correlation of wavelength change during pulse excitation and reflected optical pulse it is possible to extract information about measured parameter. Such interrogation system allaws for sampling rates higher than 30 kHz and spectral resolution of 2 pm. Because of short duration of excitation pulses such interrogation offers also time domain multiplexing which is suitable for large number of optical sensors among the same optical fiber. Both interrogation systems offer cost effective solution for fiber optic measurement systems.

07.08.2023