Excitation and detection apparatus for remote sensor connected by optical fiber

Sensing apparatus comprising:

• an optical fiber;
• a phosphorescent material coupled to one end of said optical fiber, said phosphorescent material emitting a long-lived luminescence when exposed to energy in a predetermined wavelength range, said long-lived luminescence including a measuring wavelength having an intensity responsive to a quantity being sensed and a reference wavelength having a substantially constant intensity as a function of the quantity being sensed;
• source means coupled to the other end of said optical fiber for generating an incident pulsed energy signal within said predetermined wavelength range to cause said phosphorescent material to generate said long-lived luminescence;
• detector means coupled to the other end of said optical fiber for selectively detecting the long-lived luminescence from said phosphorescent material when said incident pulsed energy signal has substantially ceased and any short-lived background luminescence generated in the apparatus has substantially ceased, said long-lived luminescence having a longer duration than said incident pulsed energy signal and said short-lived luminescence, said detector means including
• a first detector channel for detecting the measuring wavelength and providing a first signal representative of the intensity of the measuring wavelength,
• a second detector channel for detecting the reference wavelength and providing a second signal representative of the intensity of the reference wavelength, and
• signal processing means responsive to the relative values of said first signal and said second signal for providing an output representative of the quantity being sensed;
• and
• calibration source means for supplying a first calibration signal at the measuring wavelength to said first detector channel and a second calibration signal at the reference wavelength to said second detector channel for calibration of said first and second detector channels.

A sensing method comprising the steps of:

• stimulating a phosphorescent material with an incident pulsed energy signal within a predetermined wavelength range to cause emission of luminescence including a measuring wavelength having an intensity responsive to a quantity being sensed and a reference wavelength having a substantially constant intensity as a function of the quantity being sensed, the phosphorescent material being stimulated by coupling the incident pulsed energy signal to the phosphorescent material through an optical fiber;
• detecting the measuring wavelength and providing a first signal representative of the intensity of the measuring wavelength;
• detecting the reference wavelength and providing a second signal representative of the intensity of the reference wavelength, the steps of detecting the measuring wavelength and detecting the reference wavelength including the steps of coupling the luminescence through the optical fiber for detection and discriminating against the incident pulsed energy signal so as to provide low-noise detection of said luminescence;
• providing an output representative of the quantity being measured based on the relative values of said first signal and said second signal;
• and
• detecting spurious light signals on said optical fiber by comparing a detected light signal when said optical fiber is blocked with a detected light signal when said optical fiber is unblocked, spurious light signals being detected when the detected signals in blocked and unblocked conditions differ by more than a predetermined amount.