Mach-Zehnder Modulator Bias Control via Phase Extraction
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Solution Overview
Problem
In high-speed optical communications systems, existing automatic bias control circuits for Mach-Zehnder modulators suffer from reduced sensitivity due to nonlinear modulation characteristics, and pilot perturbation is difficult to remove at the receiver end, especially affecting high-order modulation formats.
Innovation Solution
A bias control apparatus and method that extracts phase bias information from output power signals of Mach-Zehnder modulators to efficiently control phase bias, improving sensitivity and applicability to various modulation formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pilot perturbation is applied for automatic bias control, then bias points can be tracked and adjusted, but sensitivity is reduced due to nonlinear modulation characteristics and pilot perturbation is hard to remove at receiver end
Solution Approach 1:
The patent extracts only the necessary phase bias information from the output power signals through mathematical processing, separating the useful bias control information from the interfering pilot perturbation signals. This extraction approach maintains control stability while improving sensitivity by focusing only on the relevant parameters.
Solution Approach 2:
The patent introduces an intermediary processing stage that uses mathematical relationships between output power signals to derive phase bias information without directly using pilot perturbation signals. This intermediary approach allows bias tracking while avoiding the sensitivity reduction and removal difficulties associated with direct pilot perturbation methods.
2Reliability
If automatic bias control circuit is used to control bias P, then modulation performance can be maintained, but performance cost (Q factor) is increased to unacceptable extent
Solution Approach 1:
The patent extracts only the essential phase bias information needed for modulation performance from the output power signals, eliminating unnecessary control actions that would consume additional Q factor. By focusing extraction on critical parameters, the system maintains modulation performance while reducing the performance cost to acceptable levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the sensitivity of bias control by directly using phase bias information from output power signals, effectively removing interference and improving modulation performance across different modulation formats.
Implementation Method 1
a photoelectric detector 105 detects output power signals of the modulator 101 of the optical transmitter
Data Source
AI summary
Embodiments of this disclosure provide a bias control apparatus and method of a modulator of an optical transmitter and an optical transmitter. By obtaining respective output power signals of a first Mach-Zehnder modulator and a second Mach-Zehnder modulator constituting the modulator of the optical transmitter, information on a phase bias may be extracted according to the two output power signals and an overall output power signal of the modulator of the optical transmitter, so as to control the phase bias by using the information, thereby efficiently improving a sensitivity of the control of the bias, and being applicable to various types of modulation formats.