Optical Amplifier Filter Span Loss Tilt Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical amplification units in fiber optical transmission systems face challenges in compensating for span loss tilt across different channel loading conditions, leading to significant gain errors when the number of channels varies, especially in ultra long haul systems, as conventional methods like using a variable optical attenuator fail to adequately adjust the gain to maintain consistent signal transmission.
Innovation Solution
An optical amplification unit with a filter that provides wavelength-dependent attenuation, placed outside the control loop, compensates for span loss tilt independently of channel loading conditions, allowing the unit to operate in constant gain mode and adjust pump power to maintain a constant overall gain, thereby minimizing gain errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the operating point of the optical amplification unit is set to compensate for average span loss in full load configuration, then the gain is optimized when all channels are present, but significant gain errors accumulate when the number of channels varies
Solution Approach 1:
The patent applies dynamics by making the filter characteristics adjustable rather than fixed. The optical filter's attenuation profile can be dynamically changed to match different channel loading conditions, allowing the system to adapt between full load and partial load configurations. This resolves the contradiction by enabling the operating point to be optimized for each specific channel configuration rather than being fixed for full load only.
Solution Approach 2:
The patent changes the parameter of filter attenuation characteristics to compensate for span loss tilt under different channel loading conditions. By adjusting the filter's wavelength-dependent attenuation parameters, the system can maintain accurate gain compensation whether all channels are present or only a subset is transmitted, thereby resolving the gain accuracy vs. adaptability contradiction.
2Measurement precision
If a variable optical attenuator is used to tilt the gain of the optical amplifier, then the span loss tilt can be compensated, but the overall gain changes and requires reconfiguration
Solution Approach 1:
The patent extracts the span loss tilt compensation function from the optical amplifier's gain control mechanism by placing an optical filter in the signal path. This separate filter component handles the tilt compensation independently, allowing the amplifier to maintain its constant gain mode without requiring complex reconfiguration when tilt compensation is applied.
Solution Approach 2:
The optical filter acts as an intermediary element between the optical amplifier and the fiber span. It mediates the span loss tilt effect by applying wavelength-dependent attenuation that counteracts the tilt, while allowing the amplifier to operate independently in constant gain mode. This intermediary approach simplifies the overall control complexity.
3Stability of the object's composition
If the optical amplification unit operates in constant gain mode with a fixed operating point, then the gain remains stable, but the span loss tilt compensation becomes inadequate when channels are added or dropped
Solution Approach 1:
The patent introduces dynamics into the filter characteristics while maintaining constant gain mode operation. The filter's attenuation profile can be dynamically adjusted in response to channel configuration changes, allowing the system to adapt to different loading conditions without leaving the stable constant gain operating mode. This resolves the contradiction between gain stability and adaptability.
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 reduces span loss tilt to near 0 dB, enabling longer distance optical signal transmission with reduced margins for varying loading conditions, improving system performance and reducing costs by minimizing gain errors across different fiber spans.
Implementation Method 1
the filter precedes or follows the optical amplifier and exhibits a wavelength-dependent attenuation of the optical signal adapted to compensate for a span loss tilt
Implementation Method 2
an optical amplifier for amplifying an optical signal
Implementation Method 3
a first measuring device for measuring a property of an input signal of the optical amplifier, a second measuring device for measuring a property of an output signal
Data Source
AI summary
An optical amplification unit comprises at least one optical amplifier for amplifying an optical signal and a filter preceding or following the optical amplifier. The optical amplifier comprises a first measuring device for measuring a property of an input signal of the optical amplifier, a second measuring device for measuring a property of an output signal of the optical amplifier, and a control circuit for controlling a gain characteristic of the optical amplifier in dependence of said input and output signal properties. The filter exhibits a wavelength-dependent attenuation of the optical signal. The optical amplification unit is connectable to an optical fiber span and the filter is adapted to compensate for a span loss tilt caused by said optical fiber span. An optical transmission system with at least one such optical amplification unit and corresponding methods.