Fiber Amplifier Gain Control With ASE Compensation and Fast Lock
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Solution Overview
Problem
Existing optical fiber amplifiers face issues with low ASE compensation accuracy and slow differential control speed, leading to bit errors and non-linearities in DWDM systems due to gain competition and overshoots.
Innovation Solution
Implementing a method and device for gain control using Finite Impulse Response (FIR) filtering, ASE compensation power value tables, and differential and integral control algorithms to smooth input power, set gradual pump activation, and adjust output power based on target gain and ASE compensation values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If analog circuits are used for gain control, then the control unit can be implemented, but the gain is not adjustable and the transfer function is fixed
Solution Approach 1:
The patent replaces the analog mechanical control system with a digital control system using a microcontroller and lookup tables. The transfer function is stored as discrete data points in memory, allowing flexible gain adjustment without changing hardware circuitry. The microcontroller reads input power, queries the lookup table for corresponding gain values, and adjusts pump laser current accordingly, making the system adaptable while keeping hardware simple.
Solution Approach 2:
The patent changes the physical state of the control system from continuous analog parameters to discrete digital parameters. By storing transfer functions as lookup tables with specific power-gain pairs, the system can switch between different operating modes and adjust gain dynamically. The microcontroller modifies digital control parameters (lookup table indices, pump current levels) rather than adjusting analog circuit components, enabling flexible gain control.
2Adaptability or versatility
If a single control mode is used, then the control logic is simple, but different control modes cannot be chosen according to incident optical power changes
Solution Approach 1:
The patent makes the control system dynamic by implementing multiple control modes that can be selected based on incident optical power conditions. The microcontroller monitors input power levels and automatically switches between different control strategies (e.g., linear region control vs. saturation region control) by selecting appropriate lookup tables. This dynamic adaptation allows the system to optimize performance for different operating conditions without complex manual configuration.
Solution Approach 2:
The patent creates a universal control system that handles multiple control modes within a single unified architecture. The microcontroller serves multiple functions: monitoring input power, selecting control modes, querying appropriate lookup tables, and controlling pump lasers. The same hardware platform supports both linear and saturation region operations, making the control unit multi-functional while keeping the overall structure relatively simple.
3Reliability
If analog control is used, then the system responds quickly, but overshoot cannot be avoided causing output optical power jitter
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal gain values in lookup tables before operation. When the microcontroller queries the lookup table based on measured input power, it retrieves pre-determined gain settings that account for system dynamics. This preliminary computation avoids real-time calculation delays while the tabulated data guides the control response to minimize overshoot and stabilize output power quickly.
Solution Approach 2:
The patent implements feedback control where the microcontroller continuously monitors output optical power and compares it with target values from the lookup table. When deviations are detected (indicating overshoot or undershoot), the system adjusts pump laser current in the next control cycle to correct the error. This closed-loop feedback mechanism suppresses oscillations and stabilizes output power while maintaining responsive control.
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
Improves ASE compensation accuracy and differential control speed, reducing overshoots and ensuring stable output power in optical fiber amplifiers, enhancing system performance in DWDM systems.
Implementation Method 1
the Pin photoelectric conversion module is set to convert the input optical power into electrical signals
Implementation Method 2
a driving circuit connected to a pump laser of the optical fiber amplifier
Data Source
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AI summary
A method of controlling gain of a fiber amplifier and a device utilizing same, employing a digital component to replace a conventional closed-loop analog control unit, and computing, according to gain or a configuration of an optical output power in combination with an amplified spontaneous emission (ASE) compensation power, on the basis of a present control mode, a final optical output power. The method comprises: smoothing an optical input power so as to remove a discrete frequency noise, while providing certain compensation to an input signal. The embodiments of the present invention enhances performance of a system by adopting a derivative control algorithm and an integral control algorithm, enabling a closed-loop control system to complete a control cycle in substantially 1 µs, effectively realizing a gain lock and power lock, meeting dynamic and steady state indicators provided by a user, addressing an issue in which a fiber amplifier does not have high-accuracy ASE compensation, and employs a low-speed derivative control, thereby increasing accuracy of ASE compensation and a speed of a derivative control.