Multicore Fiber Connector Alignment via Biasing and Polishing
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Solution Overview
Problem
Current connectors for multicore optical fibers face challenges in minimizing insertion losses due to transverse core offsets and rotational misalignment, particularly in twisted fibers, which affect the performance of shape-sensing applications and optical backscatter reflectometers.
Innovation Solution
The solution involves biasing multicore fibers within ferrule capillaries to minimize positional errors and using specialized fixtures and polishing techniques to maintain precise rotational alignment, including adjusting pre-polish angular offsets to compensate for core migration during polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard connector termination procedures are used for multicore fibers, then the connectorization process is simple and follows existing protocols, but transverse core offsets occur resulting in high insertion losses
Solution Approach 1:
The connector termination process is divided into distinct stages: initial connectorization using standard procedures, followed by a separate alignment and adjustment stage. This segmentation allows the manufacturing process to remain simple initially while achieving high precision through subsequent targeted adjustments of individual core positions.
Solution Approach 2:
Standard connector termination procedures are performed as a preliminary action to establish basic connectivity before implementing precision alignment adjustments. This preliminary connectorization provides a foundation that can be refined without requiring complete re-termination, thus maintaining ease of manufacture while improving precision.
2Adaptability or versatility
If clearance variations between fiber outer diameter and ferrule inner diameter are large, then the connector assembly is more tolerant of dimensional variations, but transverse core offsets increase leading to higher insertion losses
Solution Approach 1:
An intermediary adjustment mechanism is introduced between the fiber and ferrule that allows for precise positioning of individual cores. This intermediary element enables the system to maintain dimensional variation tolerance while achieving high core position accuracy through adjustable alignment features.
3Reliability
If angled physical contact polishing is performed on twisted multicore fibers, then return loss performance is improved, but rotational misalignment of cores occurs during the polishing process
Solution Approach 1:
The fiber is pre-positioned with an angular offset that anticipates and counteracts the rotational misalignment that will occur during angled physical contact polishing. This preliminary anti-action ensures that after polishing, the cores achieve proper alignment rather than becoming misaligned.
Solution Approach 2:
The angular position parameter of the fiber within the ferrule is deliberately changed during the polishing process. By controlling and adjusting this angular parameter, the system achieves both the desired angled physical contact for improved return loss and maintains core rotational alignment.
Data Source
AI summary
Structures and techniques are described for aligning multicore optical fibers in a multicore optical fiber cable having a plurality of optical fiber cores, at least one end portion and a protective coating. The protective coating is removed from the end portion of the multicore fiber cable to create an exposed end portion of the multicore fiber. The exposed end portion of the multicore fiber is inserted into a guide hole defined longitudinally through a ferrule subassembly. The cores of the fiber are aligned rotationally, in a predetermined orientation, relative to the ferrule. Each fiber is biased within its respective guide hole in a predetermined orientation relative to the ferrule. The multicore fiber is bonded within the ferrule. The fiber is trimmed at the ferrule tip and the ferrule and fiber end faces are polished, so that a selected alignment of the multicore fiber is achieved.