Optical Transmitter Phase Control via Frequency Monitoring
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Solution Overview
Problem
In optical transmitters, the phase variation of modulated signal light does not correspond to the expected phase variation due to the relationship between the transmission data signal and the operating point of the optical modulator, leading to potential inversion of the signal, which complicates phase modulation and affects signal quality.
Innovation Solution
An optical transmitter system comprising a signal generator, an optical modulator, a monitor, and a controller that performs digital signal processing to generate a signal shifted from a carrier frequency, monitors the appearance of specific frequency components in the modulated signal light, and controls the relationship between the drive signal and the operating point of the optical modulator to ensure expected phase variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital signal processing is applied to generate phase variation in the transmission data signal, then the transmission capacity and modulation flexibility are improved, but the signal may be inverted due to the relationship between the signal sign and the optical modulator operating point, causing phase modulation errors
Solution Approach 1:
The patent employs a feedback mechanism where the monitor detects the actual frequency component of the modulated signal light, and the controller adjusts the drive signal sign based on this detection to correct phase modulation errors. This closed-loop feedback ensures that the phase variation accurately reflects the intended digital signal processing operations.
Solution Approach 2:
The system performs self-correction by automatically detecting when signal inversion occurs through frequency monitoring and autonomously adjusting the drive signal sign without external intervention. This self-service capability maintains phase modulation accuracy while preserving the flexibility of digital signal processing.
2Manufacturing precision
If the operating point of the optical modulator is adjusted to achieve desired phase variation, then the phase modulation performance is improved, but the complexity of controlling the relationship between the drive signal and operating point increases
Solution Approach 1:
The monitor and controller automatically manage the operating point adjustments and drive signal sign changes based on frequency detection, eliminating the need for complex manual control mechanisms. The system self-regulates to maintain optimal phase modulation conditions.
Solution Approach 2:
The system dynamically changes the sign parameter of the drive signal based on detected frequency components, allowing flexible adaptation to different operating conditions without requiring complex hardware modifications or multiple fixed operating points.
3Productivity
If frequency shift is applied to the transmission data signal to increase transmission capacity, then the data rate is improved, but the monitoring and control of signal integrity becomes more difficult
Solution Approach 1:
The monitor continuously detects the frequency components of the modulated signal light, providing real-time feedback on signal integrity despite frequency shifting. This enables verification that the frequency-shifted signal maintains its intended characteristics and has not degraded.
Solution Approach 2:
The monitor acts as an intermediary between the frequency-shifted signal and the control system, translating complex frequency domain information into actionable control decisions that maintain signal integrity without requiring direct complex analysis of the high-rate transmitted signal.
Data Source
AI summary
A signal shifted from a carrier frequency in a frequency domain by using digital signal processing is generated, and the optical modulator is driven with a drive signal based on the signal. A monitor monitors whether or not a component of a modulated signal light output from the optical modulator appears in a specific frequency depending on a frequency shift performed by the digital signal processing, and the controller controls a relation between a sign of the drive signal and an operating point of the optical modulator according to a monitored result.