Multifunction optical filter with a Michelson-Gires-Tournois interferometer for wavelength-division-multiplexed network system applications.

We propose using a novel multifunction optical filter with a Michelson-Gires-Tournois interferometer (MGTI) for future smart wavelength-division-multiplexed network system applications. The MGTI filter is a typical Michelson interferometer in which one of its reflecting mirrors is replaced with a Gires-Tournois resonator. One unique feature of this device is that it can function as a channel-passing (CP), a channel-dropping (CD), or a wide-bandpass (BP) filter, depending on the interferometer arm-length difference. Other interesting features are that (1) the linewidths of both the CP and the CD filter are twice as narrow as that of a typical Fabry-Perot filter with similar parameters, (2) theoretical visibility is always unity regardless of the mirror reflectance value, and (3) the BP filter has an excellent boxlike response function. Numerical results showing these characteristics are presented.