Optical Amplifier Gain Control Using External ASE Compensation
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Solution Overview
Problem
Existing optical amplifiers face challenges in accurately monitoring and controlling gain due to interference from external ASE light power, leading to inaccurate gain settings and noise characteristics, especially when ASE light power is small and buried in background noise.
Innovation Solution
The optical amplifier employs a control unit that uses predetermined proportional relationships to compensate for external ASE power, allowing for accurate initial gain setting within the amplification signal band by detecting ASE light power and adjusting pumping light output, thereby isolating and monitoring only the ASE light power of the optical amplifier itself.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ASE light power is monitored to control gain, then gain control is achieved, but measurement precision deteriorates when ASE light power is small and buried in background noise
Solution Approach 1:
The patent converts the harmful background noise into a beneficial reference signal. By intentionally adding noise to the ASE light before detection, the system creates a known reference that can be used to distinguish the actual ASE signal from ambient background noise, thereby improving measurement precision in low-signal conditions
Solution Approach 2:
The patent introduces a noise addition unit as an intermediary component between the ASE light source and the photodetector. This intermediary adds a controlled noise signal that serves as a reference marker, enabling the detection system to differentiate between actual ASE power variations and background noise interference
2Measurement precision
If external ASE power is not compensated, then system complexity is reduced, but gain control accuracy deteriorates due to external ASE light interference
Solution Approach 1:
The patent implements a feedback mechanism where the detected ASE light power (including external contributions) is fed back to the control unit. The control unit then adjusts the pumping light power accordingly to compensate for external ASE interference, maintaining accurate gain control through continuous monitoring and adjustment
Solution Approach 2:
The system performs self-compensation for external ASE interference by using its own detection and control mechanisms. The optical amplifier monitors its own output ASE power and automatically adjusts its pumping light to compensate for external contributions, eliminating the need for separate external compensation systems
3Power
If pumping light power is increased to improve signal, then gain increases, but noise characteristics deteriorate
Solution Approach 1:
The patent replaces direct mechanical/power control with an optical control mechanism. Instead of simply increasing pumping light power to improve signal, the system uses optical feedback from ASE detection to control the pumping light, enabling more precise control that improves gain while managing noise figure through optimized pumping 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
This approach enables very accurate initial gain setting and improved noise characteristics by using a simple monitoring system, reducing the impact of external ASE power fluctuations and background noise, and enhancing the accuracy of gain control.
Implementation Method 1
an optical amplifier using an optical fiber as a medium that amplifies an optical signal
Implementation Method 2
In a case of a Raman amplifier, a Raman gain is indicated as a ratio of a signal light power when a pumping light is on relative to a signal light power when the pumping light is off
Implementation Method 3
an ASE light power Pase and a gain G have a relationship of Pase=K×G
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Included are: a pumping light source supplying a pumping light to an optical fiber as an amplification medium; an ASE light power detector detecting an ASE light power including an external ASE power flowing from an upstream side outside an amplification signal band; and a control unit setting a gain within the amplification signal band by using the ASE light power detected by the ASE light power detector outside the amplification signal band. The control unit controls the pumping light source by compensating for an influence of the external ASE power to set initially the gain within the amplification signal band. It is hereby possible to set initially a gain very accurately by using a simple system monitoring and detecting an ASE light power.