Optical Transmission System Gain Variation Control
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Solution Overview
Problem
Existing optical transmission systems experience energy loss due to gain variation and equalization processing in optical amplifiers, particularly when using wavelength division multiplexed signal light and impurity-doped optical fiber amplifiers.
Innovation Solution
The system includes a pair of terminal stations, an optical fiber, and at least one repeater with an optical amplifier that separates wavelength division multiplexed signal light into sub-bands, amplifies them, and then multiplexes them. A monitoring unit and a control unit are used to adjust the output power of specific channels to reduce the gap between sub-bands, thereby minimizing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If equalization processing is performed by cutting off signal light exceeding predetermined level, then output level alignment is achieved, but energy loss increases
Solution Approach 1:
The patent changes the gain parameter of the optical amplification unit based on the total optical power of signal light in the wavelength band. By adjusting the gain dynamically according to the total power level, the system achieves output level alignment across different input conditions without needing to cut off excessive signal light, thereby resolving the contradiction between alignment precision and energy loss.
Solution Approach 2:
The patent implements a feedback mechanism where the total optical power of signal light is measured and used to adjust the gain of the optical amplification unit. This closed-loop control ensures that the output levels remain aligned without requiring aggressive equalization processing that would cause energy loss, thus resolving the technical contradiction.
2Manufacturing precision
If gain of optical amplification unit is increased to exceed predetermined level at short wavelength, then output level alignment is improved, but energy loss increases
Solution Approach 1:
The patent dynamically adjusts the gain parameter of the optical amplification unit based on the total optical power measurement. By changing the gain to match the actual input conditions, the system achieves proper output levels without unnecessarily increasing gain that would lead to energy loss through equalization processing.
Solution Approach 2:
Instead of always using excessive gain to ensure output level alignment under all conditions, the patent applies partial action by adjusting the gain precisely to the needed level based on total optical power measurements, avoiding the energy loss associated with excessive amplification followed by equalization.
3Reliability
If wavelength division multiplexed signal light is divided into multiple wavelength bands, then gain variation is reduced, but device complexity increases
Solution Approach 1:
The patent divides the wavelength division multiplexed signal light into multiple wavelength bands using a demultiplexer, with each band being amplified by a dedicated optical amplification unit. This segmentation approach reduces gain variation within each band while maintaining overall system performance, addressing the reliability aspect of the contradiction.
Solution Approach 2:
The patent combines multiple amplified wavelength bands back together using a multiplexer after amplification. This merging operation integrates the separately amplified bands into a unified output signal, achieving gain variation control without leaving the system overly complex, as the combining function is a standard operation.
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 configuration reduces gain variation and energy loss in the optical transmission system, improving energy utilization efficiency and maintaining system performance even with aging optical amplifiers.
Implementation Method 1
Each of the plurality of repeaters includes an optical amplification unit amplifying signal light that attenuates during propagation through a long-distance optical fiber. An impurity-doped optical fiber amplifier amplifying signal light itself is used as the optical amplification unit.
Data Source
AI summary
The invention presents an optical transmission system and control method aimed at minimizing gain variation across wavelengths. The system has end stations exchanging WDM signals over a fiber optic cable with repeater stations. The repeaters split the WDM signals into multiple subbands which are separately amplified by optical amplifiers dedicated to each subband frequency range. There is a first subband with relatively shorter wavelengths and a second subband with relatively longer wavelengths. A monitoring unit tracks the output power of the longest wavelength channel in the first subband and the shortest wavelength channel in the second subband received at one end station. A control unit sends signals to the transmitting end station to adjust the gains, working to minimize the difference in output power between those two monitored wavelength channels. This aims to reduce gain variation across the full range of wavelengths in the WDM optical transmission system.