A method and system for providing fast interrogation of a signal received from a fiber optic sensor array using a low drive voltage, by modulating the array signal with a phase generated carrier optical signal having an odd harmonic modulation frequency, sending it to an interferometric system, and demodulating the array signal using a demodulation algorithm that is independent of the phase offset. A detector using direct detection method can be used to determine the signal's phase information. The odd harmonic modulation method allows the selection of a desirable odd harmonic PGC frequency with low drive voltage while providing similar performance of the usual PGC frequency that requires a higher drive voltage.