Pilot Locking Apparatus for Optical Modulator Depth Control
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Solution Overview
Problem
Current methods for controlling pilot signal modulation depth in optical channel status detection are ineffective due to the non-linear nature of Mach-Zehnder modulators, leading to instability and unpredictability in pilot signal amplitude, which hinders accurate optical channel status detection.
Innovation Solution
A method involving a transmitter with a pilot loading apparatus and a pilot locking apparatus that adjusts the initial amplitude of the pilot signal based on the pilot operating point, using correspondences between harmonic frequency components and the initial amplitude to achieve a target modulation depth, ensuring accurate detection of optical channel status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pilot signal is loaded into the service flow signal in a scrambling manner and then modulated by using an MZ modulator, then the pilot signal can be transmitted on the optical network, but the pilot signal loses its linear relationship with the initially applied pilot feature due to the non-linear feature of the MZ modulator
Solution Approach 1:
The patent implements a feedback mechanism where the actual pilot signal is detected at the receiver, and the detected pilot feature is fed back to the transmitter. The transmitter compares the detected pilot feature with the initially applied pilot feature and adjusts the pilot signal parameters accordingly to compensate for the non-linear distortion introduced by the MZ modulator, thereby restoring the linear relationship.
Solution Approach 2:
The patent changes the parameters of the pilot signal (such as amplitude, frequency, or phase) based on the detected non-linear distortion characteristics. By dynamically adjusting these parameters through the feedback loop, the system compensates for the MZ modulator's non-linear effect and maintains the desired linear relationship between the transmitted and detected pilot features.
2Measurement precision
If existing feedback loop mechanisms are used to adjust pilot signal amplitude, then power of service flow signal and pilot can be learned, but the adjustment cannot be quick and effective due to the non-linear feature of the MZ modulator
Solution Approach 1:
The patent performs preliminary characterization of the MZ modulator's non-linear transfer function during system initialization or calibration phase. This pre-acquired information about the non-linear distortion is stored and used to pre-calculate compensation parameters, enabling faster real-time adjustment without requiring iterative optimization during operation.
Solution Approach 2:
The patent implements a feedback mechanism where the actual pilot signal is detected at the receiver, and the detected pilot feature is fed back to the transmitter. The transmitter compares the detected pilot feature with the initially applied pilot feature and adjusts the pilot signal parameters accordingly to compensate for the non-linear distortion introduced by the MZ modulator, thereby restoring the linear relationship.
3Reliability
If the initial amplitude of the electrical pilot signal is adjusted to compensate for MZ modulator non-linearity, then the linear relationship can be restored, but additional control mechanisms and complexity are required
Solution Approach 1:
The patent integrates the pilot signal adjustment function into the existing feedback control architecture already present in the optical transmission system. The same feedback loop that controls other transmission parameters is extended to also control the pilot signal amplitude, allowing one control mechanism to serve multiple functions (both data signal optimization and pilot signal stabilization) without requiring entirely separate control hardware.
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
This approach allows for quick and effective adjustment of pilot modulation depth, ensuring accurate detection of optical channel status by stabilizing the relationship between pilot signal amplitude and power, thereby enhancing the reliability of optical channel monitoring.
Implementation Method 1
an optical modulator, configured to modulate, the electrical service flow signal into which the electrical pilot signal is loaded, onto an optical signal
Data Source
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AI summary
The present invention discloses a method for controlling a modulation depth of a pilot signal, a transmitter, and a pilot locking apparatus. The transmitter includes: a pilot loading apparatus, an optical modulator, and a pilot locking apparatus. The pilot locking apparatus is configured to determine a pilot operating point that is currently on a response curve and that is of the optical modulator, and a target initial amplitude of an electrical pilot signal, and control the pilot loading apparatus to adjust an initial amplitude of the electrical pilot signal to the target initial amplitude, where if a value of the pilot operating point is less than a first threshold, the target initial amplitude of the electrical pilot signal is determined based on a correspondence between a modulation depth of a one-frequency-multiplication component of an optical pilot signal that is output after the electrical pilot signal is modulated by the optical modulator and the initial amplitude of the electrical pilot signal, and a target modulation depth of the optical pilot signal. In embodiments of the present invention, a pilot modulation depth can be quickly and effectively adjusted, and then a pilot can be locked at an expected modulation depth.