DPSK Receiver Phase Bias Control via Peak Intensity Feedback
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Solution Overview
Problem
DPSK and DQPSK optical communication systems face challenges in maintaining stable operation due to variations in system parameters such as temperature and aging, which affect the phase bias and timing alignment of transmitters and receivers, leading to suboptimal performance and increased error rates.
Innovation Solution
A method that utilizes peak intensity feedback from output signals to optimize phase bias settings in optical modulators and demodulators, employing dither tones and voltage peak detectors to stabilize phase differences and minimize signal peak intensities, thereby maintaining optimal system performance across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peak intensity feedback control is implemented to stabilize phase bias, then system reliability improves, but device complexity increases
Solution Approach 1:
The patent implements feedback control by monitoring the peak intensity of the optical output signal and using this information to adjust the phase bias of the modulator/demodulator. The feedback signal is generated by detecting the peak intensity and feeding it back to the control circuit, which then adjusts the phase bias to maintain optimal system performance and stabilize operation against temperature and aging variations.
Solution Approach 2:
The system performs self-adjustment by automatically detecting its own performance through peak intensity monitoring and correcting its own phase bias without external intervention. The control circuit uses the peak intensity feedback to self-regulate the phase bias settings, enabling the system to maintain optimal operation autonomously in response to environmental changes.
2Measurement precision
If dither tones are used to optimize phase difference, then measurement precision improves, but use of energy increases
Solution Approach 1:
The patent employs dither tones with specific frequencies (such as 10 kHz or higher) that are periodic in nature. These periodic signals are applied to the modulator/demodulator to create measurable variations in the optical output, enabling precise measurement and control of phase bias. The periodic action allows the system to distinguish between different phase states and maintain accurate synchronization.
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
The solution provides improved stability and performance by optimizing phase bias settings based on peak intensity feedback, reducing data error rates and maintaining consistent operation despite temperature and aging-induced changes, thus enhancing the reliability of DPSK and DQPSK systems.
Implementation Method 1
Optical receivers include asymmetric Mach-Zehnder interferometers, also commonly referred to as delay interferometers (DIs), which act as optical DPSK/DQPSK demodulators
Implementation Method 2
These signals are detected with a balanced detector that consists of two high-speed detectors such as PIN diodes
Data Source
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AI summary
An optical communication device such as a transmitter or receiver has a control loop for controlling relative phase of two related optical signals based on signal peak intensity. An optical transmitter measures the signal peak intensity of a combined optical signal representing two data channels to adjust relative phase as desired. An optical receiver measures the signal peak intensity of combined electrical signals, single electrical signals or single optical signals to adjust relative phase as desired. Signal peak intensity is minimized or maximized by adjusting the relative phase, depending upon the modulation configuration used. The feedback control provides a consistent and robust control to stabilize the optical communication device in the presence of variables such as temperature changes, aging and manufacturing tolerances .