Patent ID: 6882758

Claim:
An optical device, comprising: an input waveguide for receiving an input signal; an optical attenuator for attenuating an optical signal, said optical attenuator including a Mach-Zehnder interferometer having: an optical signal splitter providing first and second outputs; a first waveguide leg in optical communication with said first output, having in cross section for at least a portion of its length, a semiconductor junction; a second waveguide leg in optical communication with said second output; a power source interconnected to forward bias said semiconductor junction to produce excess carriers in said first leg affecting the index of refraction of said first leg, and thereby the phase difference of a wave at outputs of said first and second waveguide legs; and a combiner in optical communications with said first and second outputs, to produce a composite optical signal having an amplitude that varies in dependence on said phase difference, and a Mach-Zehnder modulator to modulate an information signal onto said optical signal, wherein said Mach-Zehnder modulator includes: two modulator waveguide legs each guiding a portion of said input signal, each of said modulator waveguide leas having in cross section for at least a portion of its length, a semiconductor junction; and a power source reverse biasing a semi-conductor function of at least one of said two modulator waveguide leas to alter the index of refraction thereof, and thereby the phase difference of waves at outputs of said two modulator waveguide legs.