Optical Waveguide Core Sidewall Roughness Measurement by Mode Excitation
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Solution Overview
Problem
Existing methods for measuring the roughness of optical waveguide core sidewalls are limited in length and prone to air pollution, leading to inaccurate and time-consuming assessments that increase scattering losses.
Innovation Solution
A system utilizing a few-mode long-period fiber grating and an optical power meter to measure sidewall roughness by detecting transmission losses through different modes, allowing for accurate calculation of sidewall roughness based on scattering loss differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods (AFM, 3D optical profilometer) are used to measure core sidewall roughness, then measurement precision is improved, but measurement time increases significantly and the measurement area is limited
Solution Approach 1:
The patent replaces mechanical measurement systems (AFM probes, optical profilometer scanning mechanisms) with an optical measurement system that uses light transmission through the waveguide core. By measuring scattering loss of light passing through the core, the system obtains roughness information without mechanical contact or scanning, dramatically reducing measurement time while maintaining precision.
Solution Approach 2:
The measurement system integrates multiple functions into a single optical setup: it simultaneously measures roughness over the entire core length, evaluates the impact on optical transmission, and provides guidance for structural optimization. This multi-functional approach eliminates the need for separate measurement steps and accelerates the overall measurement process.
2Measurement precision
If traditional measurement methods are used after core preparation, then measurement precision is improved, but the core is exposed to air pollution causing increased scattering loss
Solution Approach 1:
The patent performs the roughness measurement immediately after core preparation while the core is still in a protected state (before cladding application or within a controlled environment). By conducting the measurement at this preliminary stage, the system obtains accurate roughness data before air pollution can contaminate the core surface, eliminating the need for re-measurement and reducing scattering loss from dust contamination.
3Reliability
If measurement is performed over a larger area of the core sidewall, then reliability of roughness assessment is improved, but measurement complexity increases
Solution Approach 1:
The patent replaces complex mechanical scanning systems with a simple optical transmission setup. Light is passed through the entire core length, and scattering loss is measured by a detector. This substitution enables full-length measurement without increasing device complexity, as the optical system naturally illuminates and detects along the entire core path in a single operation.
Solution Approach 2:
The patent merges the measurement of entire core length roughness with the assessment of optical transmission characteristics. By using light transmission as the measurement mechanism, the system simultaneously evaluates both geometric roughness and its functional impact on optical performance, reducing the need for separate measurement systems and simplifying the overall measurement process.
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
Accurately measures sidewall roughness over a larger area without air pollution, reducing measurement time and scattering losses, and providing a comprehensive view of the sidewall's condition.
Implementation Method 1
the laser beam is incident on the optical waveguide to be measured after passing through the few-mode long-period fiber grating
Implementation Method 2
the modes of the optical waveguide to be measured are obtained by exciting the optical waveguide to be measured after the laser beam passes through the few-mode long-period fiber grating
Implementation Method 3
the laser beam is incident on the optical power meter after being subjected to a scattering loss caused by the roughness of the core sidewall of the optical waveguide to be measured
Data Source
AI summary
A system for measuring roughness of a core sidewall of an optical waveguide based on mode excitation is provided, in which an optical waveguide to be measured is arranged between a few-mode long-period fiber grating and an optical power meter; the laser beam is incident on the optical waveguide to be measured after passing through the few-mode long-period fiber grating, and then is incident on the optical power meter after being subjected to a scattering loss caused by the roughness of the core sidewall of the optical waveguide to be measured; and the processor is configured to calculate an equivalent value of the roughness of the core sidewall according to the output power detected by the optical power meter, the output modes of the few-mode long-period fiber grating and the mode of the optical waveguide to be measured.