the present invention relates to a sensor interrogation system which comprises an optical fiber , at least one sensor containing first and second fiber lasers attached to the optical fiber with the first fiber laser being located spectrally at a first wavelength and the second fiber laser being located spectrally at a second wavelength different from the first wavelength , a pump laser for causing light to travel down the optical fiber so as to cause each of the fiber lasers to lase at its distinct wavelength and generate a distinct laser signal representative of the distinct wavelength , at least one filter for receiving the laser signals generated by the first and second lasers and for transmitting the laser signals from the first and second lasers within a wavelength band , and first and second scanning fabry - perot spectrum analyzers for receiving the laser signals for determining the wavelength difference between said fiber lasers .