Bidirectional Optical Amplifier Noise Figure Equalization
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Solution Overview
Problem
Bidirectional optical amplifiers face high noise-figure issues due to significant differences in input power levels between opposing signals, leading to unacceptable noise figures for signals with lower input power.
Innovation Solution
A bidirectional optical amplifier design featuring a first optical gain medium doped with rare earth elements, optical pumps, and two optical circulators to direct counter-propagating signals through a short span of actively pumped erbium-doped fiber, followed by multiple series amplifying stages to equalize noise figures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bidirectional optical amplifier is used to amplify signals in both directions, then cost savings of about 50% are achieved, but the noise figure becomes very high for signals with lower input power when input power from one direction is much higher than from the opposite direction
Solution Approach 1:
The bidirectional amplifier is divided into multiple amplifying stages (first stage, second stage, third stage) with different configurations. The first stage uses a single optical gain medium for both directions, while subsequent stages use separate optical gain mediums for each direction, allowing independent optimization of noise figures for each signal path.
Solution Approach 2:
Different parts of the amplifier system are given different properties: the first amplifying stage is designed for high gain with shared resources, while the second and third stages are designed with dedicated resources for each direction to optimize noise performance. Each direction receives appropriate amplification resources based on its specific needs.
2Reliability
If multiple series amplifying stages are used to equalize noise figures, then noise figure differences between signals are reduced, but device complexity increases
Solution Approach 1:
The amplification process is segmented into three distinct stages, each with specific functions. The first stage provides initial amplification for both directions, while the second and third stages provide differential amplification to balance noise figures. This segmentation allows complex noise equalization to be achieved through modular, manageable stages.
Solution Approach 2:
The first amplifying stage serves a dual function by amplifying signals from both directions simultaneously using a single optical gain medium. This universal stage reduces overall complexity compared to having completely separate amplification paths from the beginning, while still enabling noise figure equalization in subsequent specialized stages.
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 solution effectively reduces noise-figure differences between signals with varying power levels, ensuring low noise figures for both signals, thereby enhancing the performance of bidirectional optical amplifiers.
Implementation Method 1
optical pumps for pumping the optical gain mediums with pump light, whereby optical gain at the signal wavelength is created in the optical gain medium when the optical signals counter-propagate therethrough in the presence of pump light
Implementation Method 2
two optical circulators configured to direct two input beams through the first optical gain medium in opposite directions so that they counter-propagate through the first optical gain medium
Data Source
AI summary
A bidirectional optical amplifier amplifies optical signals having signal wavelength and signal power input from two directions. The amplifier is arranged so that two counter-propagating signals pass through a first pumped rare earth doped pre-amplifier before passing through other amplifiers downstream. Optical circulators route the two counter propagating signals so that they both pass through in a counter-propagating manner through subsequent pumped rare earth doped amplifiers downstream.