Optical Transmission Apparatus Tilt Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wavelength division multiplexing (WDM) optical transmission systems, the use of in-line amplifiers (ILAs) instead of reconfigurable optical add-drop multiplexers (ROADMs) increases optical fiber length and span loss, leading to tilts due to wavelength-dependent loss, which can exceed the pre-emphasis control capabilities of wavelength selective switches (WSSs), making it difficult to maintain favorable transmission characteristics.
Innovation Solution
A transmission apparatus with an amplifier controller to set a target average optical input power and a pre-emphasis controller to adjust optical powers for respective wavelengths based on reception powers, allowing for increased pre-emphasis control and compensation of tilts, enabling the use of ILAs in place of ROADM apparatuses while maintaining low-cost network construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an in-line amplifier (ILA) is installed in place of a ROADM apparatus to reduce cost, then network construction cost is reduced, but optical fiber length increases and span loss increases, leading to increased tilt that exceeds pre-emphasis control capability
Solution Approach 1:
The system performs preliminary measurement of per-wavelength reception optical powers at the receiving side before transmission, and uses these measurements to calculate and set the target average optical input power and pre-emphasis amounts in advance. This preliminary action enables the transmitting side to compensate for the increased tilt caused by longer fiber spans, allowing ILA installation while maintaining transmission quality.
Solution Approach 2:
The system establishes a feedback loop where the receiving side measures per-wavelength reception optical powers and transmits this information to the transmitting side. The transmitting side uses this feedback to dynamically adjust the target average optical input power and pre-emphasis control amounts, enabling adaptive compensation for tilt variations caused by different fiber lengths and span losses.
2Ease of manufacture
If optical fiber length increases to allow ILA installation, then cost is reduced, but span loss increases and tilt increases beyond WSS pre-emphasis control range
Solution Approach 1:
The system changes the parameter of target average optical input power based on measured reception powers and calculated span losses. By dynamically adjusting this parameter along with pre-emphasis control amounts, the system compensates for the effects of increased fiber length, enabling the use of longer spans with ILAs while maintaining transmission characteristics within acceptable ranges.
3Ease of manufacture
If span loss increases due to longer fiber length, then ILA can be used instead of ROADM, but tilt increases beyond the amount of pre-emphasis control that can be performed by WSS
Solution Approach 1:
The system performs preliminary measurement of per-wavelength reception optical powers and calculation of span loss characteristics before implementing transmission. This preliminary action enables the system to determine appropriate target average optical input power and pre-emphasis control amounts that compensate for the increased span loss, allowing ILA installation while keeping tilt within WSS control capability.
Solution Approach 2:
The system uses feedback from measured per-wavelength reception optical powers to dynamically adjust pre-emphasis control amounts. This feedback mechanism enables the system to compensate for variations in span loss caused by different fiber lengths and conditions, maintaining transmission quality even with increased span losses from ILA installation.
Data Source
AI summary
A transmission apparatus includes: an amplifier controller configured to determine a target value for an average optical input power of a transmitting amplifier in a transmitting-side apparatus, based on an index based on a quality of transmission from an output of the transmitting amplifier to an output of a receiving amplifier in a receiving-side apparatus; and a pre-emphasis controller configured to determine amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the output of the receiving amplifier.