The invention pertains to wavelength-agile optical filters suitable for wavelength-division-multiplexed
(WDM) optical communications networks. More particularly, the invention pertains
to optical filters with a wavelength reference that can be remotely switched to
arbitrarily selectable channels on a standard grid, and to re-configurable optical
communications networks employing same. The present invention provides a communication
apparatus with a tunable filter which may be used in a wide range of applications
including tuning an external cavity laser (ECL), selecting a wavelength for an
add/drop multiplexer and providing channel selection and feedback for a wavelength
locker. The filter may be utilized as a discrete component or in combination with
circulators, wavelength lockers and gain medium. The filter may be implemented
in whole or in part as part of a gain medium. The tunable filter exhibits a compact
form factor and precise tuning to any selected wavelength of a predetermined set
of wavelengths comprising a wavelength grid. The tunable filter may thus be utilized
in telecom applications to generate the center wavelengths for any channel on the
ITU or other optical grid.
