Optical sensors are a widely employed method of measuring analyte concentration, typically oxygen, within a package or container.  Briefly, analyte concentration within a package or container can be measured by placing an analyte sensitive fluorophore within the package or container, allowing the fluorophore to equilibrate within the package or container, exciting the fluorophore with radiant energy, and measuring the intensity and/or rate of decay in the intensity of luminescence emitted by the excited fluorophore.  Such optical sensors are available from a number of suppliers, including Presens Precision Sensing, GmbH of Regensburg, Germany. 
Optical sensors typically employ fiber optics to both guide the excitation light generated by the sensor from the sensor to the analyte sensitive fluorophore, and also guide emitted light from the fluorophore to a photo multiplier in the optical sensor for detection and measurement. 
While effective for accurately measuring analyte concentration, such optical sensors are very expensive. 
Accordingly, a substantial need exists for a low cost optical sensor capable of accurately and reliably measuring analyte concentration within a package or container.