A sensing apparatus includes a light source to transmit a light beam, an input switch, a first sensing element, a second sensing element, and a detector. The input switch receives the light beam and includes a phase change material having a first state and a second state. The first sensing element receives the light beam from the input switch when the phase change material is in the first state and produces a first change in the light beam in response to a presence of a first analyte. The second sensing element receives the light beam from the input switch when the phase change material is in the second state and produces a second change in the light beam in response to a presence of a second analyte. The detector detects the first change and/or the second change in the light beam.

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