AN ULTRA-COMPACT AND REPRODUCIBLE FIBER TIP MICHELSON INTERFEROMETER FOR HIGH-TEMPERATURE SENSING (invited)

An ultra-compact fiber tip Michelson interferometer (MI), primarily aimed for a reproducible and stable high-temperature sensing probe is developed and demonstrated. Both singlemode fiber (SMF) and polarization maintaining fiber (PMF) are considered and compared. The tip MI is fabricated by only using a one-step partial-polishing technique, which forms a half oblique and half vertical end face and functions as a beam splitter. A wide spectra analysis proved that the interferometer has an optical path difference (OPD) that is consistent across samples. When the lead-in fiber suffers from bending or twisting, the interference spectrum for the PMF case is more stable than that for the SMF case. Experimental results show a linear average temperature sensitivity of 15.15 pm/◦C in the range of 100◦C to 1000◦C for three tested PMF samples, and the difference between the sensitivities of the samples is less than 4.0%. The ease of fabrication, highly compact structure, reproducibility, and excellent resistance to mechanical disturbance performance suggest that the proposed PMF tip MI is highly promising as a high temperature sensing probe with high spatial resolution.