Over the last decade, optical fibers have been increasingly considered for point-of-care medical diagnostics by ways of so-called lab-on-fiber probes owing to their compact size, flexibility, chemical stability, and remote operation. To ensure the reliability of a medical diagnosis, different biomarkers are usually targeted, whilst a reference is always taken, and this has not been shown with optical fiber sensors yet. Thus, presence of a reference measurement together with the simultaneous detection of more than one analyte with a single fiber probe still represents a challenge.