Methods and devices for optimizing the operation of a semiconductor optical modulator
A semiconductor-based optical modulator includes a control loop to control and optimize the modulator's operation for relatively high data rates (above 1 GHz) and/or relatively high voltage levels. Both the amplitude of the modulator's driving voltage and the bias of the driving voltage may be adjusted using the control loop. Such adjustments help to optimize the operation of the modulator by reducing the number of errors present in a modulated data stream.
1. A semiconductor optical modulator comprising:
a redundant receiver for receiving a modulated optical signal and converting the received optical signal into an electrically equivalent data signal;
a processor for receiving the equivalent data signal and an original input data signal, comparing the equivalent data signal to the original input data signal to count logical data errors in the equivalent data signal, and transmitting a control signal associated with results of the count to a driver circuit; and
a driver circuit for receiving the control signal and for controlling voltage conditions based on the received control signal.
2. The semiconductor optical modulator as in claim 1 wherein the processor further comprises:
a comparator for comparing logical bits of the electrically equivalent data signal to logical bits of the original input data signal;
a counting module for counting a number of logical “0” errors and a number of logical “1” errors during a period of time based on the results of the comparisons made by the comparator, and calculating a percentage of total errors that are logical “1” errors; and
a threshold detector operable to receive the percentage of total errors from the counting module, and to generate the control signal based on whether or not the calculated percentage is above a threshold.
3. The semiconductor optical modulator as in claim 1 further comprising:
an optical waveguide for supporting propagation of an input optical signal; and
an optical resonator formed on a surface of a semiconductor substrate and disposed in evanescent communication with the optical waveguide and configured to have a resonant wavelength to evanescently couple the input optical signal between the optical waveguide and the optical resonator;
an optical coupler for coupling a portion of the modulated optical signal to a waveguide connected to the redundant receiver; and
wherein the redundant receiver further comprises a photodetector for converting a received, coupled portion of the modulated optical signal into the electrically equivalent signal.
4. The semiconductor optical modulator as in claim 3 wherein the substrate comprises silicon.
5. The semiconductor optical modulator as in claim 3 wherein the optical resonator comprises a ring resonator or a disk resonator.
6. The optical modulator as in claim 1 wherein the control signal comprises a signal to reduce amplification of the modulated signal, or a signal to reduce a bias voltage of the modulated signal or a signal to reduce both the amplification and bias voltage of the modulated signal.
7. The optical modulator as in claim 1 wherein the modulator comprises a structure selected from a group consisting of a monolithic integrated structure, a flip-chip bonded structure, a vertically-stacked structure, a three-dimensionally integrated arrangement, a two-dimensionally integrated arrangement and a standalone circuit.
8. A method for controlling a semiconductor optical modulator comprising:
receiving a modulated optical signal from an optical resonator;
converting the received optical signal into an electrically equivalent data signal;
receiving the equivalent data signal and an original input data signal;
comparing the equivalent data signal to the original input data signal to count logical data errors in the equivalent data signal;
transmitting a control signal to a driver circuit; and
receiving the control signal at the driver circuit to control voltage conditions.
9. The method as in claim 8 further comprising:
comparing logical bits of the electrically equivalent data signal to logical bits of the original input data signal;
counting a number of logical “0” errors and a number of logical “1” errors during a period of time based on the results of the comparisons, and calculating a percentage of total errors that are logical “1” errors;
receiving the percentage of total errors from the counting module; and
generating the control signal based on whether or not the calculated percentage is above a threshold.
10. The method as in claim 8 further comprising:
evanescently coupling an input optical signal between an optical waveguide and the optical resonator.
11. The method as in claim 8 wherein the control signal comprises a signal to reduce amplification of the modulated signal, or a signal to reduce a bias voltage of the modulated signal or a signal to reduce both the amplification and bias voltage of the modulated signal.
12. The method as in claim 8 wherein the optical resonator comprises a ring resonator or a disk resonator.