A biosensing device for detecting biological analytes, and methods of use and manufacture, are disclosed. The device includes a biosensing element that can remain implanted for extended periods of time. The biosensing element is connected to an optical fiber terminating outside of the body. The optical fiber is also connected to an information analyzer. The information analyzer directs light through the optical fiber into the biosensing element. The light excites fluorophores, created by a chemical reaction between analytes and biosensing material within the biosensing element. Emitted fluorescent light is redirected through the optical fiber to the information analyzer. Optical gratings within the filtering member of the information analyzer selectively deflect fluorescent emissions into a cladding layer. Detectors attached to the cladding layer detect the deflected fluorescent emissions and, according to their determined wavelength, report the presence or quantity of specific analytes to the patient on an external display.