A sensing system including a sensor having an enclosure that defines a chamber, a fiber optic segment extending from outside the enclosure into the chamber, and a sequence of optical processing elements within the chamber. The elements include a fiber Bragg grating, a polarizer, a side hole fiber, and a mirror. A light source is arranged to direct light to the sensor(s). A spectral analyzer is arranged to detect light reflected back from the sensor(s). The fiber Bragg grating substantially reflects a first spectral envelope while transmitting the remainder of the optical spectrum to the polarizer and side hole fiber. The polarizer, side hole fiber, and mirror cooperate to return an optical signal within a second spectral envelope. The characteristic wavelength of a peak in the first spectral envelope is highly sensitive to temperature and relatively weakly sensitive to pressure. The period of the optical signal within the second spectral envelope is highly sensitive to pressure and relatively weakly sensitive to temperature. The spectral analyzer measures these spectral components to simultaneously derive a measure of temperature and pressure that effectively compensates for temperature-pressure cross-sensitivity of the sensor(s).