Dynamic Gain Control for Optical Amplifier Power Equalization
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Solution Overview
Problem
Current Passive Optical Network (PON) technologies face challenges in extending transmission distance and increasing branching ratio, leading to unequal power levels of uplink signals received by the Optical Line Terminal (OLT), which requires complex Automatic Gain Control (AGC) adjustments and can result in signal distortion when using optical amplifiers.
Innovation Solution
A method and apparatus that utilize a Semiconductor Optical Amplifier (SOA) or rare earth doped fiber amplifier with high-speed gain control circuits to dynamically adjust the gain or attenuation of uplink optical signals, ensuring equal peak powers across different burst slots through feedback control and ASE pre-compensation, thereby reducing the AGC adjustment range and maintaining optimal input power for wavelength converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If optical amplifiers are added to extend transmission distance and increase branching ratio, then the coverage and capacity of PON network are improved, but the power levels of uplink signals from different ONUs become unequal, causing the far-near problem and requiring complex AGC adjustments
Solution Approach 1:
The patent applies preliminary action by performing power equalization before the AGC adjustment at the OLT receiver. The optical amplifier equalizes the power levels of uplink signals from different ONUs before they reach the OLT, so that the AGC only needs to perform minor adjustments within a reduced range (e.g., 3-6 dB instead of 15 dB). This preliminary power equalization simplifies the subsequent AGC operation and reduces the required AGC adjustment range.
Solution Approach 2:
The patent introduces an intermediary component - the optical amplifier with equalization function - between the ONUs and the OLT receiver. This intermediary device actively compensates for the power differences caused by different transmission distances, converting the unequal power levels into equal power levels before the signals reach the OLT, thereby mediating the far-near problem.
2Length of stationary object
If optical amplifiers are used to amplify uplink burst signals, then the signal transmission distance is extended, but signal distortion occurs when the input optical power exceeds the linear working area of the amplifier
Solution Approach 1:
The patent applies dynamics by using a dynamically controllable optical amplifier that can adjust its gain in real-time based on the input signal power levels. The amplifier transitions from a static fixed-gain device to a dynamic variable-gain device that adapts to different input conditions, ensuring that each burst signal is amplified within the linear working area regardless of its initial power level.
Solution Approach 2:
The patent changes the operating parameters of the optical amplifier, specifically the gain parameter, to maintain operation within the linear working area. By dynamically adjusting the gain parameter based on input power measurements, the system ensures that the amplifier operates in its linear region, preventing signal distortion while extending transmission distance.
3Productivity
If the AGC adjustment time is kept short as stipulated by PON standards, then the network efficiency is improved, but the signal dynamic range of different ONUs cannot be properly adjusted, leading to reception errors
Solution Approach 1:
The patent performs preliminary power equalization before the AGC adjustment, so that the majority of power level corrections are completed in advance by the optical amplifier. This leaves only a small residual adjustment range for the AGC to handle within the standard time constraint, enabling both high network efficiency and precise power level adjustment.
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 solution effectively equalizes output power of uplink burst signals, reduces the complexity of OLT and ONU devices, and maintains input power within a linear working area, enhancing the performance and efficiency of PON networks.
Implementation Method 1
an optical amplifier, wherein the optical amplifier is a Semiconductor Optical Amplifier (SOA)... the optical amplifier dynamically adjusting a gain value according to the control signal
Implementation Method 2
a first optical detector... which is converted into an electric signal which varies with uplink burst slots via a first optical detector
Implementation Method 3
the optical amplifier is a rare earth doped fiber amplifier
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A method for amplifying and dynamically adjusting an optical signal is provided in the present invention, which includes: a first optical tap splitting out a small part of the optical signal, which is converted into an electric signal via a first optical detector and is then output to a high speed gain control circuit, in proportion from an uplink burst optical signal, and outputting a remainder of the optical signal to an optical amplifier; the high speed gain control circuit dynamically adjusting the control signal loaded on the optical amplifier according to the input electric signal which varies with uplink burst slots; and the optical amplifier dynamically adjusting a gain value according to the loaded control signal to make peak powers of the output uplink optical signals in different burst slots equal, thus achieving output power equalization. With the present invention, the peak optical powers of the uplink burst optical signals of different optical network units after being amplified are close or equal, thus achieving output power equalization.