We demonstrate a highly sensitive temperature sensor based on a stress-induced high-birefringence-fiber Sagnac loop that uses a Nd-doped-fiber amplified spontaneous emission source. Relative temperature sensing is done in the spectral domain by shifts of a resonant wavelength λr and absolute temperature sensing by changes in separation between resonances Δλ . The measured relative change of these parameters with temperature in the range 15–110°C, is (1/λr)(δλr/δT) = -(1/Δλ)(δΔλ/δ T) ≈ (1/Δn)(δ Δn/δT)(-0.94 ± 0.02) × 10-3/K, with measured fiber birefringence Δn = 8 × 10-4 . This gives a wavelength-shift sensitivity of -1.00 nm/K at 1.065 µm and a resonance separation sensitivity of 0.006 nm/K for Δλ = 6.8 nm . This telemetric point sensor has a loop length of 80 m, an operational bandwidth of more than 50 nm, and a temperature accuracy of better than 1 °C.
© 1997 Optical Society of America
E. De la Rosa, L. A. Zenteno, A. N. Starodumov, and D. Monzon, "All-fiber absolute temperature sensor using an unbalanced high-birefringence Sagnac loop," Opt. Lett. 22, 481-483 (1997)