Integrated optical waveform modulator
View Patent ↗A method of modulating an optical carrier. A target carrier modulation is computed based on an input data signal. An effective length of an optical modulator is then controlled based on the target carrier modulation.
1. An integrated optical synthesizer comprising:
a driver integrated circuit (IC) comprising a digital signal processor (DSP) for computing a multi-bit digital sample stream indicative of a target carrier modulation based on an input data signal, the DSP having a digital filter for computing respective multi-bit digital values of In-phase and Quadrature components of a target optical E-field modulation;
an optical modulator integrated with the driver IC on a substrate or a plurality of substrates that are secured in a tile or stacked arrangement;
a plurality of electrodes in operative relation to a waveguide of the optical modulator, each electrode being adapted to impose a respective predetermined modulation to light propagating within the waveguide;
means, for each set of electrodes, for delaying a time of arrival of the respective bit of the sample stream to each electrode of the set, such that a time of arrival of the bit at each electrode substantially corresponds with an expected time of arrival of an optical wavefront propagating through the waveguide; and
means for selectively activating one or more of the plurality of electrodes in accordance with the target carrier modulation.
2. An optical synthesizer as claimed in claim 1 , wherein the driver IC and the optical modulator are formed on respective different wafers, and electrically connected together.
3. An optical synthesizer as claimed in claim 1 , wherein the digital filter is adapted to apply a compensation function adapted to compensate impairments of an optical link.
4. An optical synthesizer as claimed in claim 1 , wherein each electrode is substantially identical.
5. An optical synthesizer as claimed in claim 1 , wherein the plurality of electrodes comprises a respective set of one or more electrodes for each bit of the multi-bit digital sample stream, the number of electrodes of each set corresponding to a binary weight of its respective bit of the digital sample stream.
6. An optical synthesizer as claimed in claim 5 , wherein the means for selectively activating one or more of the plurality of electrodes comprises a parallel bus for supplying each bit of the multi-bit digital sample stream to its respective set of electrodes.
7. An optical synthesizer as claimed in claim 6 , wherein the parallel bus comprises means for differentially delaying each bit of the multi-bit digital sample stream in accordance with a propagations speed of an optical signal through the waveguide.
8. An optical synthesizer as claimed in claim 1 , wherein the means for selectively activating one of more of the plurality of electrodes comprises: a logic circuit for determining which electrodes in the plurality of electrodes correspond to a binary value of the multi-bit digital sample stream; and a parallel bus for supplying a control signal to the electrodes determined to correspond to the binary value.
9. A system for transmitting a data signal through an optical communications network, the system having an integrated optical synthesizer comprising:
a driver integrated circuit (IC) comprising a digital signal processor (DSP) for computing a multi-bit digital sample stream indicative of a target carrier modulation based on the data signal, the DSP having a digital filter for computing respective multi-bit digital values of In-phase and Quadrature components of a target optical E-field modulation;
an optical modulator integrated with the driver IC on a substrate or a plurality of substrates that are secured in a tile or stacked arrangement;
a plurality of electrodes in operative relation to a waveguide of the optical modulator, each electrode being adapted to impose a respective predetermined modulation to light propagating within the waveguide;
means, for each set of electrodes, for delaying a time of arrival of the respective bit of the sample stream to each electrode of the set, such that a time of arrival of the bit at each electrode substantially corresponds with an expected time of arrival of an optical wavefront propagating through the waveguide; and
means for selectively activating one or more of the plurality of electrodes in accordance with the target carrier modulation.