“…In passive detection, any electrical, mechanical, or active optical element is not used in the optical section of the system. Bulk edge filters, Fabry‐Perot filters, matched‐filters, erbium‐doped fiber (EDF) filters, biconical fiber filters, wavelength division couplers, fiber Bragg gratings, multimode fiber‐based filters can be given as examples of passive systems. The advantages of passive linear edge filter systems are low cost, ease of fabrication, and high measurement speeds, compared to active wavelength measurement systems.…”