Use of super luminescence diodes in absolute temperature measurement

Summary form only given. A fiber pigtailed super luminescence diode (SLD) with FWHM of 63.3 nm and central wavelength of 1539.3 nm illuminated a tantalum pentoxide thin film on the end-face of a single mode optical fiber through a 2/spl times/2 biconical directional coupler. The optical signal coming from the thin film was monitored on reflection using a spectrum analyser. The reason that a SLD source was used in this experiment is because of the fact that the optical bandwidth of the source is quite wide enough (i.e., 63.3 nm) and thus allows one to obtain the interference fringes of the thin film within this optical bandwidth. If the tantalum pentoxide film at the fiber tip is exposed to any temperature fluctuations, positions of the interference hinges, inside 63.3 nm "gaussian-like" optical window of the SLD, will experience a shift towards longer or shorter wavelengths, depending on the positive or negative thermal effects of the film\´s optical thickness.