Variable Gain Erbium Doped Fiber Amplifier Flat Spectral Control
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Solution Overview
Problem
Conventional erbium doped fiber amplifiers (EDFA) provide non-uniform gain across wavelengths and cannot maintain flat spectral gain when average gain values change, requiring adjustments in pump power and the use of variable optical attenuators (VOA) to compensate.
Innovation Solution
A variable gain optical amplifier system using two erbium doped fibers, a gain flattening filter, a pump laser, and a thermo electric cooler, controlled by a controller to adjust pump power and temperature, providing a variable flat spectral gain output without the need for a VOA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional EDFA uses a GFF to provide flat gain at a specific average gain value, then the spectral gain is flat for that specific gain value, but the spectral gain becomes non-flat when the average gain value changes
Solution Approach 1:
The patent applies dynamics by making the GFF characteristics variable through temperature control. The GFF's attenuation profile changes dynamically with temperature, allowing it to compensate for different wavelength-dependent gain shapes at different average gain values. This enables the system to maintain flat spectral gain across a range of average gain values without requiring multiple fixed GFFs or additional VOAs.
Solution Approach 2:
The patent changes physical parameters (temperature) of the GFF to alter its attenuation characteristics. By controlling the temperature of the GFF, the system adjusts the filter's spectral properties to match the required compensation for different average gain values, thereby maintaining flat spectral gain across variable operating conditions.
2Adaptability or versatility
If a VOA is added to compensate for wavelength dependent gain at different average gain values, then variable flat spectral gain is achieved, but the device complexity and cost increase
Solution Approach 1:
The patent makes the GFF serve multiple functions: it provides both gain flattening and variable gain control through temperature adjustment. This eliminates the need for a separate VOA component, reducing device complexity while achieving variable flat spectral gain. The single GFF performs what would traditionally require multiple components.
Solution Approach 2:
The patent merges the functions of the GFF and VOA into a single temperature-controlled GFF. By combining these functions, the system reduces the number of components needed while achieving the same overall effect of variable flat spectral gain, thereby simplifying the amplifier structure.
3Power
If pump power is increased to provide higher average gain, then the average gain increases, but the wavelength dependent gain shape changes causing spectral non-flatness
Solution Approach 1:
The patent uses feedback control where the system monitors the average gain value and adjusts the GFF temperature accordingly. This feedback mechanism ensures that as pump power changes to provide different average gain levels, the GFF temperature is simultaneously adjusted to maintain the appropriate attenuation profile, thereby preserving spectral flatness across all gain settings.
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 achieves low pump power requirements, compact design, low noise, reduced cost, and high reliability, with the ability to maintain flat spectral gain across different average gain values.
Implementation Method 1
When stimulated by light streams, for example an input optical signal having wavelengths in a C-band (1528-1570 nm) or an L-band (1570-1620 nm), the excited atoms return to a ground or lower state by stimulated emission. The stimulated emission has the same wavelength as that of the stimulating light.
Implementation Method 2
when pump light at 980 nm or 1480 nm is launched into an EDF, erbium atoms absorb the pump light, pushing the erbium atoms into excited states
Implementation Method 3
A wavelength dependent attenuating filter can be designed to compensate for the wavelength dependent gain of an EDFA at a specific average gain value such that the combined effect provides an ideally flat gain for all operating wavelengths.
Implementation Method 4
a thermo electric cooler configured to control a temperature of one or more of the first erbium doped fiber and the second erbium doped fiber
Data Source
AI summary
Systems, methods, and apparatuses are provided for variable gain optical fiber amplifiers. In one implementation, a variable gain optical amplifier is provided. The amplifier includes a first erbium doped fiber configured to receive an input optical signal, a second erbium doped fiber configured to output an output optical signal, a gain flattening filter positioned between the first erbium doped fiber and the second erbium doped fiber, a pump laser configured to provide energy to the first erbium doped fiber and the second erbium doped fiber, a thermo electric cooler configured to control a temperature of one or more of the first erbium doped fiber and the second erbium doped fiber, and a controller configured to adjust an output from the pump laser and a temperature of at least one of the first erbium doped fiber and the second erbium doped fiber to provide a variable flat spectral gain output.