Multi-Facet Fiber Endcap for Back-Reflected Light Rejection

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Solution Overview

Problem

Existing fiber optic endcap designs fail to effectively manage back-reflected light in high-power fiber laser applications, leading to potential damage and performance degradation due to limited total internal reflection (TIR) acceptance angles, which allow back-reflected light to escape and cause damage to upstream components.

Innovation Solution

The implementation of a fiber optic endcap device with multiple angled facets, arranged at angles between 30° to 40° relative to the axis, distributed symmetrically to reflect counterpropagating light back through the output end via total internal reflection, thereby increasing the TIR acceptance range and rejecting back-reflected light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional fiber optic endcap designs are used, then the structure is simple, but the TIR acceptance angle is limited allowing back-reflected light to escape and damage upstream components

Engineering Contradiction:

Improveprotection against back-reflected light damageVSAvoidendcap structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The endcap is segmented into multiple discrete facets (e.g., three facets at 120° intervals) instead of a single continuous reflective surface. Each facet is independently angled to provide total internal reflection for back-reflected light, thereby increasing the overall TIR acceptance angle while maintaining structural feasibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution transitions from a simple planar or single-angle reflective surface to a three-dimensional multi-facet geometry. By arranging facets at specific angles (e.g., 30°-40° relative to the axis) in rotational symmetry, the design captures back-reflected light from a wider range of incidence angles through spatial distribution

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If the endcap uses a simple reflective surface, then the manufacturing is easier, but it cannot effectively reflect back-reflected light over a wide range of incidence angles

Engineering Contradiction:

Improveacceptance angle range for TIRVSAvoidfacets arrangement precision

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Each facet is asymmetrically angled relative to the endcap axis (e.g., 30°-40°) rather than being symmetrically perpendicular. This asymmetric angling creates the necessary condition for total internal reflection of back-propagating light while maintaining rotational symmetry among multiple facets, thereby expanding the acceptance angle range

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

Different regions of the endcap (individual facets) have locally optimized orientations tailored to reflect light from specific angular ranges. Each facet's unique angle is precisely engineered to maximize TIR for its designated sector, collectively covering a broad range of incidence angles

Inventive Principle:

Principle #3Local quality

3Power

If high-power fiber laser applications are used, then the processing capability is enhanced, but back-reflected light causes significant damage to upstream components

Engineering Contradiction:

Improvefiber laser output powerVSAvoidback-reflected light damage

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The endcap design converts the harmful back-reflected light into a beneficial retroreflected beam. By using multiple angled facets to provide total internal reflection, the system redirects harmful counterpropagating light back through the output end, transforming a damage-causing factor into a controlled optical pathway that protects upstream components

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design significantly enhances the rejection of back-reflected light over a wide range of incidence angles, reducing the risk of damage to upstream components and improving performance by ensuring that counterpropagating light is retroreflected back through the output end, even when the alignment is off-axis, thus providing a more robust solution compared to traditional designs.

Implementation Method 1

a plurality of angled facets arranged at respective angles relative to an axis of the endcap device to reflect at least a portion of the counterpropagating light back through the output end

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS11209595B2Retroreflective fiber endcap

Publication Date: 2021.12.28 WELLS FARGO BANK NA

AI summary

An optical fiber endcap device may include an input facet spliced onto an input fiber and an output end through which counterpropagating light enters the optical fiber endcap device. The optical fiber endcap device further includes a plurality of angled facets that are arranged at respective angles relative to an axis of the optical fiber endcap device to reflect at least a portion of the counterpropagating light back through the output end of the optical fiber endcap device.