A fiber includes M primary cores and N redundant cores, where M an integer is greater than two and N is an integer greater than one. Interferometric circuitry detects interferometric pattern data associated with the M primary cores and the N redundant cores when the optical fiber is placed into a sensing position. Data processing circuitry calculates a primary core fiber bend value for the M primary cores and a redundant core fiber bend value for the N redundant cores based on a predetermined geometry of the M primary cores and the N redundant cores in the fiber and detected interferometric pattern data associated with the M primary cores and the N redundant cores. The primary core fiber bend value and the redundant core fiber bend value are compared in a comparison. The detected data for the M primary cores is determined reliable or unreliable based on the comparison. A signal is generated in response to an unreliable determination.