Relay Lens Coupling in Multi-Core Fiber Amplifiers for MFD Matching
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Solution Overview
Problem
The mismatched mode field diameters (MFDs) between transmission multi-core fibers (MCFs) and multi-core erbium doped fibers (MC-EDFs) lead to connection losses and inefficiencies in optical amplifiers, despite thermal expansion techniques, due to differences in refractive index distributions and core intervals.
Innovation Solution
A multi-core fiber module with a relay lens system that matches the core intervals and MFDs between transmission and connection optical waveguides, using a relay magnification that equals the ratio of core intervals and expanding the core at the leading end surface of the connection waveguide to match the MFDs, thereby reducing connection losses and aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thermal expansion technique is used to match mode field diameters, then connection loss is reduced, but mismatch remains due to differences in refractive index distributions and core intervals
Solution Approach 1:
A relay lens system is introduced as an intermediary component between the transmission MCF and the MC-EDF. The relay lens system with specific magnification ratios matches the core intervals and mode field diameters between the two fibers, enabling precise optical coupling that overcomes the limitations of direct thermal expansion methods
Solution Approach 2:
The patent changes the optical parameters (core interval ratio and mode field diameter ratio) by introducing a relay lens system with controlled magnification. This allows independent adjustment of these parameters to achieve optimal matching between transmission MCF and MC-EDF, rather than relying solely on thermal expansion of the fiber cores
2Productivity
If core diameter is increased to reduce MFD mismatch, then connection efficiency improves, but core interval matching becomes more difficult
Solution Approach 1:
The relay lens system acts as an intermediary that decouples the relationship between core diameter and core interval matching. By using lenses with specific magnification ratios, the system can match both parameters simultaneously without requiring direct physical modification of the fiber cores
Solution Approach 2:
The optical coupling function is segmented into multiple components: the transmission MCF, the relay lens system (with input and output lenses), and the MC-EDF. This segmentation allows each component to be optimized independently, with the relay lens system specifically designed to match both core intervals and mode field diameters
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 configuration effectively reduces light connection losses and suppresses aberrations, enhancing the utilization efficiency of excitation light and minimizing end face reflections in optical amplifiers.
Implementation Method 1
a relay lens system interposed between the transmission optical waveguide assembly and the connection optical waveguide assembly
Implementation Method 2
A core at a leading end surface of the connection optical waveguide assembly is expanded
Data Source
AI summary
A multi-core fiber module includes a transmission MCF configured to be used as a transmission path for an optical signal, a connection MCF having a core arrangement similar to a core arrangement of a core of the transmission MCF, and a relay lens system interposed between the transmission MCF and the connection MCF. A relay magnification of the relay lens system is equal to a ratio of a core interval of the connection MCF to a core interval of the transmission MCF. A core at a leading end surface of the connection MCF is expanded such that a ratio between the core interval and a mode field diameter of the connection MCF is equal to a ratio between the core interval and a mode field diameter of the transmission MCF.