Google Inc.

Lorenzo Bolla

Marco Romagnoli

Luciano Socci

Silvia Ghidini

Paola Galli

Giorgio Grasso

Marco Piazza

Stefano Lorenzotti

Gaia Cevini

Federico Boffi

The method for filtering an optical signal comprising a plurality of channels lying on a grid of optical frequencies equally spaced by a frequency spacing and occupying an optical bandwidth, comprises: a) operating an optical filter comprising a plurality of resonators, wherein a first resonator of the plurality is optically coupled to the optical signal and the remaining resonators are optically coupled in series to the first resonator, so that a respective resonance of each one of the plurality of resonators falls within a first frequency band having bandwidth less than or equal to 15 GHz; b) operating the optical filter so as to obtain a separation between said respective resonance of at least one resonator with respect to said respective resonance of at least another different resonator, the separation being greater than or equal to 25 GHz; c) operating the optical filter so that said respective resonance of each one of the plurality of resonators falls within a second frequency band, different from the first frequency band, having bandwidth less than or equal to 15 GHz, wherein during the procedure from step a) to step c), at least one among said respective resonance of the at least one resonator and said respective resonance of the at least another different resonator is moved also outside a frequency region spanning between, and including, the first and the second frequency band. A corresponding device for filtering an optical signal is disclosed.

Method and device for hitless tunable optical filtering

A method of filtering an optical signal includes operating an optical filter having resonators, each having a respective free spectral range and a respective resonance falling within a first frequency band, first tuning at least one resonator with respect to at least another resonator to obtain a separation between any resonance of at least one resonator falling within an optical bandwidth with respect to a resonance of at least another resonator nearest to the any resonance, second tuning all the resonators of the optical filter so as to move all respective resonances by a respective frequency interval greater than a frequency spacing, and third tuning the at least one resonator and the at least another resonator such that a further respective resonance of each one of the resonators falls within a second frequency band, different from the first frequency band.

An optical mode transformer comprises a first waveguide including a first core, a first cladding and an end facet configured to be coupled to an optical fiber. A second waveguide comprises a second core and a second cladding, and is arranged with respect to the first waveguide so as to realize an evanescent optical coupling with the first waveguide. The second core comprises a tapered region, in at least a portion of which the evanescent coupling takes place. The first core and the second core are separated by a gap. A first refractive index contrast of the first waveguide is less than a second refractive index contrast of the second waveguide.

Optical mode transformer, in particular for coupling an optical fiber and a high-index contrast waveguide

An optical mode transformer comprises a first waveguide including a first core, a first cladding and an end facet configured to be coupled to an optical fiber. The transformer further includes a second waveguide comprising a second core, a second cladding and an end directly coupled to an end of the first waveguide. A third waveguide comprises a third core and a third cladding, and is arranged with respect to the second waveguide so as to realize an evanescent optical coupling with the second waveguide. The third core includes a tapered region wherein evanescent coupling takes place, and wherein a refractive index contrast of the first waveguide is less than a refractive index contrast of the second waveguide, the refractive index contrast of the second waveguide is less than a refractive index contrast of the third waveguide, and the refractive index contrast of the third waveguide is not less than 18%.

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Verona, Italy

Lorenzo Bolla