US 6,888,856 B2 · Method and apparatus for filtering an optical beam

Abstract

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.

Claims32

Dependent claims

A tunable filter for use in optical communication apparatus, said tunable filter being tunable to each selected center wavelength of a number of channels, and each of the channels centered on a corresponding gridline of a selected wavelength grid;

said tunable filter comprising:
a grid generator having reflective surfaces, mounted for optical alignment in an optical path of a beam, and the grid generator of a first selected optical path length determinative of a first free spectral range having a first plurality of transmission peaks corresponding to gridlines of the selected wavelength grid;
a channel selector having reflected surfaces, mounted for optical alignment in the optical path of the beam, and the channel selector with a tunable second optical path length determinative of a second free spectral range having a second plurality of transmission peaks within the selected wavelength grid, wherein the second free spectral range (FSR2) is related to the first free spectral range (FSR1) by the equation:
FSR2≈(M/M±1)(FSR1)
wherein M is the total number of channels within the selected wavelength grid;
means for maintaining the first optical path length of the grid generator;
and
means for varying the tunable second optical path length of the channel selector to tune the optical beam to a selected channel of the wavelength grid and substantially attenuate the other channels of the wavelength grid.

5 more elements

Dependencies are inferred from the claim text.

Method and apparatus for filtering an optical beam

Life of this patent

Method and apparatus for filtering an optical beam

Life of this patent

Abstract

Claims32