Nonincremental coherent optical fiber sensor

A novel coherent optical fiber sensor for nonincremental measurements of phase-conveyed information is reported. When the frequency of a laser source is sinusoidally modulated, a nonincremental measurement can be processed with the same frequency-demodulation treatment as used for an incremental one. This method is applied to a polarimetric fiber-optic sensor to obtain the absolute temperature measurement in the range of 20–100°C. A rotating half-wave plate gives the polarimetric setup the frequency carrier essential for the demodulation process. Experimental data confirming the theoretical predictions are reported together with the measured sensitivity values