Optical Waveguide Folded Back Design for Loss Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In optical modulators, folding optical waveguides to miniaturize the device increases optical loss due to radiation from folded portions, and previous solutions like grooves along the folded waveguide do not adequately address the issue of optical loss while maintaining miniaturization.

Innovation Solution

The optical modulator features a waveguide with linear and arcuate portions arranged at narrower intervals, where arcuate portions have increasing central angles closer to the center, and connecting portions that bend opposite to the arcuate portions, reducing optical loss and miniaturizing the device without hindering its size reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the optical waveguide is folded back to miniaturize the optical modulator, then the device size is reduced, but optical loss increases due to light radiation from the folded portion

Engineering Contradiction:

Improvedevice sizeVSAvoidoptical loss

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

A low refractive index portion is introduced as an intermediary element between the core and cladding layers at the folded portion of the optical waveguide. This intermediary layer with refractive index lower than both the core and cladding reduces light radiation loss by modifying the refractive index distribution, thereby suppressing optical loss while maintaining the compact folded structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The low refractive index portion is selectively positioned only at the folded portion of the optical waveguide rather than throughout the entire structure. This localized modification targets specifically the area where light radiation occurs, reducing optical loss at the critical folded section while maintaining the overall compact design

Inventive Principle:

Principle #3Local quality

2Loss of energy

If the plurality of semi-arcuate portions is concentrically arranged at intervals narrower than intervals between the plurality of linear portions, then the curvature radius of each semi-arcuate portion increases and optical loss is reduced, but the length of each connecting portion increases in the longitudinal direction of the substrate

Engineering Contradiction:

Improveoptical lossVSAvoidlength of connecting portion

Core Design Contradiction:

Loss of energyVSLength of moving object

Solution Approach 1:

Instead of having the connecting portions bend in the same direction as the arcuate portions, the connecting portions are designed to bend in the opposite direction. This inversion of the bending direction allows the arcuate portions to be arranged at narrower intervals with increased curvature radius, reducing optical loss while the connecting portions compensate by bending oppositely to maintain compact overall length

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration effectively reduces optical loss in the folded portion of the waveguide while promoting the miniaturization of the optical modulator by optimizing the curvature radius and length of connecting portions, enhancing the device's compactness without significant loss penalties.

Implementation Method 1

a low refractive index portion formed on the substrate along a folded portion of the optical waveguide and having a refractive index lower than a refractive index of the substrate

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10948800B2Optical modulator with an optical waveguide partially folded back and optical module with the optical modulator

Publication Date: 2021.03.16 FUJITSU OPTICAL COMPONENTS LTD

AI summary

An optical waveguide includes: a plurality of linear portions arranged in parallel to each other; a plurality of arcuate portions, in the folded portion of the optical waveguide, concentrically arranged about a predetermined center position as a center on the substrate at intervals narrower than intervals between the plurality of linear portions, each of the arcuate portions having a central angle that increases as each of the arcuate portions is closer to the center position; and a plurality of connecting portions respectively connecting the plurality of linear portions and the plurality of arcuate portions, at least one group of the connecting portions bending in a direction opposite to a direction where each of the arcuate portions bends.