Abstract: A measurement system for fiber sensors includes a broadband light source 11 providing continuous light which is launched into a fiber 20 having a plurality (or string) of Bragg grating sensors 24, 28, 34. Each sensor has a predetermined central reflection wavelength which shifts as a function of applied strain. Reflected light 40 from the sensors 24, 28, 34 are fed to a plurality of optical bandbass filters 50, 64, 78, each having a monotonic region in a passband corresponding to one of the sensors. Each monotonic region transmits the reflected wavelength from a corresponding sensor. Light 52, 66, 80 is passed from the filters 50, 64, 78 to optical detectors 54, 68, 82 each providing an electrical signal having a magnitude related to transmission of the filter at the reflection wavelength of the sensor. Optional demodulators 58, 72, 86 are connected to each of the detectors 54, 68, 82 if the light source 10 is modulated.

Abstract: An optical sensor diagnostic system includes a tunable narrow wavelength-band source 9 which provides a variable wavelength light 44 into an optical fiber 32,52. Reflective sensors 54,58, such as Bragg gratings, are disposed along the fiber 52 in the path of the variable light 44. The sensors 54,58 transmit light 56,60 having a minimum transmission wavelength which varies due to a perturbation, such as strain, imposed thereon. A tuner control circuit 42 drives the tunable light source 9 to cause the source light 44 to scan across a predetermined wavelength range to illuminate each sensor at its minimum transmission wavelength. The power of the transmitted light is converted to an electrical signal by a detector 64 and monitored by a signal processor 68 which detects drops in transmitted power level and provides output signals on lines 71 indicative of the perturbation for each sensor.