Methods and sensors for monitoring internal tissue conditions

The present invention relates to fiberoptic sensors embedded within a surgical drain to monitor the condition of tissue proximate to the surgical drain and methods of processing data from the sensors. The light transmitting and collecting tips of the optical fibers are adapted to enable sideways interrogation of the adjacent tissues using optical techniques to measure the tissue condition. The light transmitting and collecting tips of the optical fibers may be bent at angle, disposed between a light absorbing and transmitting sheets, or uncladded to enable sideways emission and collection of light. Processing methods for reducing the site dependency of the measured data, maximizing the signal to noise ratio, and increasing the measurement sensitivity to changes in the tissue condition are described.