Integrated Optical Linewidth Reduction via Feed-Forward Phase Noise Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional linewidth reduction systems for optical signals, such as compact lasers, face issues with small wall-plug efficiency, weak tunability, and mode hoping, while conventional feedback techniques often result in feedback loop instability, necessitating a more effective method for reducing linewidth.
Innovation Solution
An integrated optical linewidth reduction system that includes a phase noise detector and a phase modulator, utilizing a feed-forward technique to split and process optical signals through different paths with varying propagation delays, generating control signals to modulate the phase noise, thereby reducing the linewidth of the incoming optical signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional feedback techniques are used to cancel phase noise over a large frequency bandwidth, then phase noise cancellation is improved, but feedback loop instability occurs
Solution Approach 1:
The patent inverts the conventional feedback approach by using feed-forward technique. Instead of detecting error and correcting it (feedback), the system predicts and compensates for phase noise in advance (feed-forward). This is achieved by using a phase noise detector to measure phase noise, then using a phase modulator to pre-compensate the optical signal before it enters the laser, thereby avoiding feedback loop instability while maintaining phase noise cancellation effectiveness
2Volume of moving object
If compact lasers are used to achieve narrow linewidth, then device compactness is improved, but wall-plug efficiency decreases
Solution Approach 1:
The patent introduces an intermediary system consisting of a phase noise detector and phase modulator that acts as a mediator between the compact laser and the optical signal. This intermediary feed-forward linewidth reduction system allows compact lasers to achieve narrow linewidth without sacrificing wall-plug efficiency, as the phase noise compensation is achieved through the intermediary components rather than requiring larger, more efficient laser designs
3Measurement precision
If conventional laser designs are used to achieve narrow linewidth, then linewidth reduction is improved, but tunability becomes weak
Solution Approach 1:
The patent segments the linewidth reduction function from the laser itself, placing the phase noise compensation function in a separate feed-forward system. This segmentation allows the laser to maintain its tunability characteristics while the dedicated phase noise detector and modulator handle linewidth reduction, thereby preserving adaptability while achieving narrow linewidth
4Measurement precision
If conventional laser designs are used to achieve narrow linewidth, then linewidth reduction is improved, but mode hopping characteristics occur
Solution Approach 1:
The patent applies preliminary action by using the phase noise detector to measure and the phase modulator to compensate for phase noise before it causes mode hopping. This advance compensation prevents mode hopping from occurring in the first place, maintaining mode stability while achieving narrow linewidth reduction
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 system effectively reduces the linewidth of optical signals, enhancing stability and efficiency by subtracting detected phase noise from the optical signal, resulting in a substantially reduced phase noise and improved performance in applications like spectroscopy and communication systems.
Implementation Method 1
a phase modulator adapted to modulate the phase of the incoming optical signal in response to the detected phase noise
Data Source
AI summary
An integrated optical linewidth reduction system detects/estimates the phase noise of an incoming optical signal and subtracts the detected phase noise from the phase noise of the incoming signal. A first coupler/splitter of the linewidth reduction system may split the incoming signal into first and second optical signals travelling through first and second optical paths. A second coupler/splitter may split the second optical signal into third and fourth optical signals travelling through third and fourth optical paths. The third optical path has a longer propagation delay than the fourth optical path. Two different coupling ratios of the third and fourth optical signals are used to generate an electrical signal representative of the phase noise of the incoming signal. A phase detector/estimator estimates the phase noise from the electrical signal. A phase modulator subtracts the detected/estimated phase noise from the phase noise of the incoming signal.