A method of calibrating an orthogonally redundant sensor device for determining the concentration of glucose in a body of a user, said sensor device including at least an electrochemical glucose sensor and an optical glucose sensor, the method comprising: receiving a first signal from the electrochemical glucose sensor; receiving a second signal from the optical glucose sensor; performing a respective integrity check on each of said first and second signals (2012, 2022); determining whether the first signal can be calibrated, and whether the second signal can be calibrated, wherein said determination is made based on whether the first signal and the second signal pass or fail their respective integrity checks; wherein the integrity check for one or both of the electrochemical sensor and the optical sensor includes checking for sensitivity loss, noise, and sensor drift, and wherein it is determined: that the respective signal passes its integrity check, and can be calibrated, if the sensitivity loss, noise, and drift of the respective signal fall within respective calculated limits; and that the respective signal fails its integrity check and cannot be calibrated if one or more of the sensitivity loss, noise, and drift fall outside of respective calculated limits; wherein, if it is determined that the respective signal has failed its integrity check, the method further includes determining whether the other signal passes its integrity check and, if the other signal passes its integrity check, using the other signal to correct (2014, 2024) said respective signal; if it is determined that the first signal can be calibrated, calibrating said first signal to generate an electrochemical sensor glucose value; if it is determined that the second signal can be calibrated, calibrating said second signal to generate an optical sensor glucose value; and fusing said electrochemical SG value and said optical SG value to obtain a single, fused sensor glucose value for the orthogonally redundant sensor device; wherein orthogonal redundancy is defined as two devices employing two different technologies to reach the same goal, wherein the failure modes of the two devices are completely unique and do not intersect. receiving a first signal from the electrochemical glucose sensor; receiving a second signal from the optical glucose sensor; performing a respective integrity check on each of said first and second signals (2012, 2022); determining whether the first signal can be calibrated, and whether the second signal can be calibrated, wherein said determination is made based on whether the first signal and the second signal pass or fail their respective integrity checks; wherein the integrity check for one or both of the electrochemical sensor and the optical sensor includes checking for sensitivity loss, noise, and sensor drift, and wherein it is determined: that the respective signal passes its integrity check, and can be calibrated, if the sensitivity loss, noise, and drift of the respective signal fall within respective calculated limits; and that the respective signal fails its integrity check and cannot be calibrated if one or more of the sensitivity loss, noise, and drift fall outside of respective calculated limits; that the respective signal passes its integrity check, and can be calibrated, if the sensitivity loss, noise, and drift of the respective signal fall within respective calculated limits; and that the respective signal fails its integrity check and cannot be calibrated if one or more of the sensitivity loss, noise, and drift fall outside of respective calculated limits; wherein, if it is determined that the respective signal has failed its integrity check, the method further includes determining whether the other signal passes its integrity check and, if the other signal passes its integrity check, using the other signal to correct (2014, 2024) said respective signal; if it is determined that the first signal can be calibrated, calibrating said first signal to generate an electrochemical sensor glucose value; if it is determined that the second signal can be calibrated, calibrating said second signal to generate an optical sensor glucose value; and fusing said electrochemical SG value and said optical SG value to obtain a single, fused sensor glucose value for the orthogonally redundant sensor device; wherein orthogonal redundancy is defined as two devices employing two different technologies to reach the same goal, wherein the failure modes of the two devices are completely unique and do not intersect.