Few-Mode Fiber Link With Differential Mode Delay Compensation
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Solution Overview
Problem
Current optical fiber designs with large effective-area single-mode fibers face limitations in spectral efficiency due to fiber nonlinearity, and few-mode fibers with step or parabolic cores struggle with demultiplexing optical signals in the time domain due to large delay differences between modes, making it difficult to achieve high spectral efficiency and system capacity.
Innovation Solution
The development of a few-mode optical fiber link with differential mode group delay compensation, achieved by designing fibers with opposite differential mode group delays and slopes, allowing for the combination of fibers with specific refractive index profiles and core designs to minimize net differential mode group delay and slope, enabling efficient signal transmission across a broad wavelength band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large effective-area single-mode fibers are used to reduce fiber nonlinearity, then nonlinearity penalties are reduced, but spectral efficiency increases only slowly
Solution Approach 1:
The fiber link is segmented into multiple spans, each containing a few-mode fiber with specific differential mode group delay characteristics. By dividing the total link into manageable segments with compensating properties, the system achieves both low nonlinearity and high spectral efficiency through distributed mode multiplexing across multiple fiber spans.
Solution Approach 2:
The patent employs composite fiber design by combining few-mode fibers with opposite differential mode group delay slopes to create a composite link structure. This composite approach integrates fibers with complementary characteristics to simultaneously reduce nonlinearity effects and enhance spectral efficiency through mode-division multiplexing.
2Productivity
If few-mode fibers with step or parabolic cores are used to increase system capacity, then mode multiplexing is enabled, but large delay differences between modes cause demultiplexing difficulties in the time domain
Solution Approach 1:
The patent applies counterbalancing by combining few-mode fibers that have opposite differential mode group delay slopes. The positive slope of one fiber compensates for the negative slope of another, effectively canceling out the cumulative differential mode delay and enabling straightforward time-domain demultiplexing while maintaining high system capacity through mode multiplexing.
Solution Approach 2:
The invention changes the differential mode group delay slope parameter by selecting fibers with opposite slope characteristics. This parameter change strategy allows the system to maintain mode multiplexing capabilities for high capacity while transforming the delay characteristics to enable easy demultiplexing through appropriate fiber combination.
3Ease of operation
If fibers with opposite differential mode group delays are combined to compensate for delay differences, then signal demultiplexing is improved, but fiber link design complexity increases
Solution Approach 1:
The patent manages design complexity by systematically changing and matching differential mode group delay slope parameters. By establishing clear parameter selection criteria (opposite slopes with specific magnitude relationships), the invention provides a structured approach that simplifies the design process while achieving effective delay compensation and easy signal demultiplexing.
Data Source
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AI summary
An optical fiber link suitable for use in a mode division multiplexing (MDM) optical transmission system is disclosed. The link has a first optical fiber having a core which supports the propagation and transmission of an optical signal with X LP modes at a wavelength of 1550 nm, wherein X is an integer greater than 1 and less than or equal to 20, the first fiber having a positive differential mode group delay between the LP01 and LP11 modes at a wavelength between 1530-1570. The link also has a second optical fiber having a core which supports the propagation and transmission of an optical signal with Y LP modes at a wavelength of 1550 nm, wherein Y is an integer greater than 1 and less than or equal to 20, said optical fiber having a negative differential mode group delay between the LP01 and LP11 modes at a wavelength between 1530-1570.