A sample measurement and analysis system comprises a fiber-optic channel selecting apparatus, a plurality of optical source lines, a plurality of optical return lines, a plurality of sample test sites, and an optical receiving device. The selecting apparatus comprises an optical input selection device, an optical output selection device, and a controller element. The optical input selection device defines a first optical path running between a first input end and a first output end. The first output end is rotatable to a plurality of first index positions defined along a first circular path. The optical output selection device defines a second optical path running between a second input end and a second output end. The second input end is rotatable to a plurality of second index positions defined along a second circular path. The controller element communicates with the optical input selection device and the optical output selection device for selectively aligning the first optical path with the first index positions and the second optical path with the second index positions.