Fiber Splice Coating Breakage via Refractive Index Gradient
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Solution Overview
Problem
Fusion splicing of photonic crystal fibers with general fibers in wavelength conversion pulsed light sources often results in coating layer breakage due to high leakage light, which is exacerbated by the mismatch in mode field diameters and the broadening of the pulsed light spectrum, leading to significant power loss and heat generation.
Innovation Solution
A fiber structural body is created with a photonic crystal fiber and a general fiber fusion spliced, where the second fiber is coated with a first and second coating layer, with the first coating layer having a higher refractive index than the clad layer of the second fiber, and specific conditions are met to guide and diverge leakage light away from the fusion splice, reducing heat absorption and preventing coating layer breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fusion splicing is performed between photonic crystal fiber and general fiber, then light transmission is achieved, but coating layer breakage occurs due to high leakage light
Solution Approach 1:
A sleeve structure is introduced as an intermediary component between the photonic crystal fiber and general fiber. The sleeve has a refractive index lower than both fibers, creating a refractive index gradient that guides leakage light away from the coating layer. This mediator structure prevents direct contact between high-intensity leakage light and the coating layer, thereby preventing breakage while maintaining splicing efficiency.
Solution Approach 2:
The refractive index distribution is deliberately changed by introducing a sleeve with a specific refractive index (lower than both the photonic crystal fiber and general fiber). This parameter change creates a refractive index gradient that alters the propagation path of leakage light, directing it away from the coating layer and reducing the intensity of light that would otherwise cause coating layer breakage.
2Ease of manufacture
If mode field diameter mismatch is present between fibers, then fiber selection is simplified, but leakage light increases causing coating layer breakage
Solution Approach 1:
The sleeve acts as a mediator that compensates for the mode field diameter mismatch between different fiber types. By having a refractive index lower than both fibers, the sleeve creates a refractive index gradient that effectively manages the interface between fibers with different mode field diameters, reducing leakage light generation while allowing flexible fiber selection.
Solution Approach 2:
The refractive index parameter of the sleeve is specifically chosen to be lower than both the photonic crystal fiber and general fiber. This parameter change creates a favorable refractive index gradient that reduces the impact of mode field diameter mismatch, thereby decreasing leakage light while maintaining ease of fiber selection and assembly.
3Power
If pulsed light with high peak intensity is used, then optical nonlinear effects are achieved, but heat generation increases causing coating layer breakage
Solution Approach 1:
The sleeve serves as a thermal and optical mediator between the high-power pulsed light source and the coating layer. By having a refractive index lower than the surrounding fibers, the sleeve guides the high-intensity pulsed light and its associated heat away from the coating layer, enabling the use of high peak intensity light for optical nonlinear effects while preventing coating layer breakage from excessive heat generation.
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
The solution effectively reduces the power of leakage light entering the coating layer, preventing breakage and maintaining high splicing efficiency by ensuring the leakage light is diverted and absorbed minimally, thus enhancing the durability and performance of the fiber structural body.
Implementation Method 1
the first coating layer has a refractive index n1 that is larger than a refractive index of a clad layer of the second fiber
Data Source
AI summary
A fiber structural body includes a first fiber, and a second fiber spliced to the first fiber such that light having propagated through the first fiber propagates through the second fiber. At least one of the fibers is a photonic crystal fiber. The second fiber is coated with a first coating layer and a second coating layer in order from a splice surface, and the first coating layer has a refractive index n1 larger than that of a clad layer of the second fiber. In the fiber structural body, L, r, n1, and NA satisfy a particular relationship.