Radio frequency drive level control system and method for an electro-optic phase modulator
AssigneeCiena Corporation
InventorsDouglas L. McGhan, Ian B. Betty
Life of this patent
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Abstract
The present disclosure provides Radio Frequency (RF) drive level control systems and methods for an Electro-Optic (EO) M-ary Phase-Shift Keying (M-PSK) phase modulator. Specifically, an M-PSK drive waveform is tightly controlled for maximum symmetry in the associated constellation. In an exemplary embodiment, the present disclosure includes an M-PSK transmitter, an M-PSK electro-optic phase modulator, and phase modulation method that each control RF drive level based upon a carrier suppression ratio defined as a measure of ratio of a modulated time-averaged E-field to the magnitude of the E-field. In an exemplary embodiment, the carrier suppression ratio is measured based on a modulation depth measurement.
Claims12
A phase modulation method, comprising:
- phase modulating a laser source with a drive signal;
- measuring a carrier suppression ratio of an output of the phase modulated laser source;
- controlling the drive signal based upon the carrier suppression ratio;
- providing the laser source to a modulator;
- splitting a portion of the laser source prior to the modulator and providing the portion to a low frequency probe phase modulator;
- combining an output of the low frequency probe phase modulator with a portion of an output of the modulator;
- converting the combined output to an electrical signal;
- and
- determining modulation depth from the electrical signal, wherein the modulation depth is utilized to determine the carrier suppression ratio.
An electro-optic phase modulation system, comprising:
- a modulator;
- a modulator driver configured to drive the modulator with a Radio Frequency drive signal;
- and
- a drive level control circuit configured to monitor a portion of an output of the modulator and to control the Radio Frequency drive signal based thereon;
- wherein the Radio Frequency drive signal comprises a M-ary Phase Shift Keying signal;
- wherein the modulator is configured to measure a carrier suppression ratio;
- and
- wherein the carrier suppression ratio comprises a modulated time-averaged E-field divided by a magnitude of the E-field.
An M-ary Phase-Shift Keying transmitter, comprising:
- a laser source;
- a phase modulator configured to modulate the laser source based on a Radio Frequency drive signal;
- a feedback control circuit configured to control the Radio Frequency drive signal based upon carrier leakage at an output of the phase modulator;
- a first splitter configured to split the laser source to the phase modulator and a low frequency probe;
- a second splitter configured to split an output of the phase modulator to a transmitter output and a combiner;
- the combiner configured to combine an output of the low frequency probe and the split output of the phase modulator;
- and
- a photodiode connected to the combiner providing an electrical signal to the feedback control circuit.
Dependencies are inferred from the claim text.