Mode Field Diameter Measurement Using Optical Integration

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Solution Overview

Problem

Existing methods for measuring the mode field diameter (MFD) of single-mode fibers face a contradiction between measurement accuracy and speed, as they require segmentation of integrals leading to increased time consumption and deviation, while methods like the mask method sacrifice theoretical precision for rapid measurement.

Innovation Solution

The proposed optical integration technique employs a gradually variable aperture method, transforming integrals into a mean square value of the numerical aperture (NA) using an optical integrator with a series of apertures that vary continuously from 0 to 25 degrees, allowing for accurate and rapid MFD measurement without approximation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the standard test methods (far field scan, variable aperture, near field scan) are used to measure MFD, then measurement accuracy can be maintained through integral segmentation, but measurement time increases significantly (tens of seconds to minutes)

Engineering Contradiction:

ImproveMFD measurement accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical segmentation and summation process with an optical integration system. The integrator uses optical components (lenses, apertures, detectors) to perform the integral calculation of the Petermann II definition in real-time, eliminating the need for multiple discrete measurements and computational summation. This optical substitution directly resolves the contradiction by maintaining integral accuracy while reducing measurement time to seconds.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an integrator as an intermediary device between the fiber under test and the measurement system. This integrator performs the complex integral operation of the Petermann II definition automatically, serving as a mediator that transforms the lengthy segmentation process into a single rapid measurement while preserving measurement accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the mask method is used to improve measurement speed, then measurement time is reduced, but theoretical precision is influenced due to paraxial approximation

Engineering Contradiction:

Improvemeasurement speedVSAvoidtheoretical precision

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent replaces the mask method's geometric optics approach with an optical integration system that directly implements the Petermann II integral definition. This substitution eliminates the paraxial approximation inherent in the mask method, maintaining theoretical precision while achieving rapid measurement through optical integration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If the variable aperture method uses limited number of apertures (less than 20), then device complexity is reduced, but measurement accuracy decreases due to inability to capture small angle regions (0-5 degrees)

Engineering Contradiction:

Improveaperture configurationVSAvoidMFD measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces the discrete aperture array with a continuous optical integration system. The integrator uses optical components to continuously sample the angular distribution from 0 to 25 degrees without the limitations of discrete aperture positions, maintaining measurement precision while simplifying the physical device structure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method significantly increases measurement accuracy and speed, achieving results more than ten times faster than traditional methods while maintaining high precision, enabling efficient automatic testing and reducing labor time in industrial production.

Implementation Method 1

uses an integrator with ingenious design to complete the integrals by virtue of an optical method

Methodology Applied

Scientific EffectOptical integration:

Implementation Method 2

outgoing light of the test fibre passes through and does not pass through a gradually variable aperture optical integrator

Methodology Applied

Scientific EffectLight propagation: Light

Data Source

PatentUS10132716B2Method for measuring mode field diameter of single-mode fibre using optical integration technique employing gradually variable aperture

Publication Date: 2018.11.20 ZHOU JIN

AI summary

The present invention discloses a method for measuring a mode field diameter (MFD) of a single-mode fiber using an optical integration technique employing a gradually variable aperture. The method transforms, according to Petermann II definition, an integral operation in a formula of an MFD of a single-mode fiber into elementary arithmetic operations to be performed on a mean square value of the numerical aperture of the fiber. By using an optical integrator having a gradually variable aperture, the mean square value of the numerical aperture of the single-mode fiber can be precisely measured by one of the following three methods: translation, rotation and beam splitting, thus accordingly solving the MFD of the test fiber. The aforementioned measurement an MFD of a single-mode fiber is characterized by precision, high speed and convenience, and can be widely applied in various applications, such as measurement standards, automated test equipment, and engineering instruments.