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US 5,359,449 AGranted
Optical modulator for an optical transmitter
AssigneeFujitsu Limited
InventorsHiroshi Nishimoto, Hironao Hakogi, Takatoshi Minami
Life of this patent
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Abstract
An optical transmitter having a Mach-Zehnder optical modulator comprising a signal electrode fed with a driving signal for effecting modulation and a bias electrode for operating point control. Because the signal electrode and the bias electrode are independent of each other, a driving circuit and the signal electrode can be connected in a DC setup. This permits stable operating point control and improves waveform characteristics.
Claims23
An optical modulator comprising:
- an optical interferometer type modulating means having an input port which receives light from a light source, a first and a second branching waveguide which transmit the light supplied to said input port after branching the supplied light in two directions, an output port which converges the branched light from said first branching waveguide and said second branching waveguide before outputting the converged light, and a signal electrode and a bias electrode which are insulated form each other and which give a phase change to the light transmitted through said first branching waveguide and said second branching waveguide;
- driving means directly connected to said signal electrode in a DC setup, for supplying said signal electrode with a driving signal based on an input signal;
- and
- operating point control means operatively connected to said bias electrode, for supplying said bias electrode with a bias voltage controlled in accordance with the light output from said output port for control of the operating point of said modulating means.
1 more element
An optical modulator comprising:
- an optical interferometer type modulating means for modulating in intensity light from a light source;
- and
- driving means, connected operatively to said modulating means for supplying said modulating means with a driving signal based on an input signal;
- said modulating means including:
- an input-side optical waveguide;
- a first branching portion for branching in two directions the light transmitted through said input-side optical waveguide;
- a first and a second branching waveguide for transmitting the light branched by said first branching portion;
- a second branching portion for converging the light transmitted through said first branching waveguide and said second branching waveguide;
- an output-side optical waveguide for transmitting the light converged by said second branching portion;
- a first and second electrode cooperating respectively with said first branching waveguide and said second branching waveguide;
- a delay optical waveguide coupled directionally to at least one of said first branching waveguide and said second branching waveguide;
- and
- a control electrode for controlling the coupling ratio of the directional coupling between said at least one branching waveguide and said delay optical waveguide.
10 more elements
Dependencies are inferred from the claim text.