U-Shaped Holder for Single-Mode Optical Device Alignment

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Solution Overview

Problem

The assembly of single-mode optical devices with high coupling efficiency is challenging due to the limitations of positioning tolerance (1 μm) and glue shrinkage, which causes misalignment, especially in telecom applications where precise alignment is critical for low noise and high performance, and existing technologies like YAG welding are not suitable for mass production of low-cost devices.

Innovation Solution

A U-shaped holder with locating and binding preventing portions is used to secure optical devices, allowing controlled flow and solidification of bonding elements, ensuring vertical symmetry and preventing glue from filling gaps that could cause misalignment, thus maintaining precise optical axis alignment during the assembly process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If glue is used for assembling single-mode optical devices, then mass production and low cost are achieved, but glue shrinkage during liquid/solid transition causes misalignment and coupling loss

Engineering Contradiction:
Improvemass production capabilityVSAvoidalignment precision
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-positioning the optical device on the holder using a positioning element before applying the bonding element. The positioning element maintains precise alignment (within 1 μm tolerance) during the bonding process, preventing misalignment caused by glue shrinkage. This allows the bonding element to be applied without compromising alignment precision, enabling mass production while maintaining coupling efficiency.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent introduces a positioning element as an intermediary between the optical device and the holder. This positioning element serves as a mediator that maintains precise alignment during the bonding process, allowing the bonding element to be applied without causing misalignment. The positioning element is subsequently removed after bonding, having fulfilled its intermediary function of preserving alignment precision during mass production assembly.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Manufacturing precision

If YAG welding is used for packaging single-mode devices, then precise alignment with +/- 2.5 μm tolerance is achieved, but the technology is not suitable for mass production of low-cost devices

Engineering Contradiction:
Improvealignment precisionVSAvoidmass production suitability
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent employs a disposable positioning element that is inexpensive and used only temporarily during the assembly process. This positioning element provides precise alignment (comparable to YAG welding tolerance) during bonding, then is removed and discarded. This approach enables mass production of low-cost devices with high precision without requiring expensive YAG welding equipment or processes.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces the complex thermal-mechanical YAG welding system with a simpler mechanical positioning and bonding system. Instead of using laser welding with simultaneous shots to balance shrinkage movements, the patent uses a mechanical positioning element combined with a bonding element, achieving similar precision through mechanical means that are more suitable for mass production.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If optical lenses are used to adapt mode size, then positioning tolerance is relaxed by a factor of 2.5, but the requirement for butt-coupling with no lens in-between cannot be met

Engineering Contradiction:
Improvepositioning toleranceVSAvoidoptical component complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating a localized precise positioning interface between the optical device and holder, while leaving the rest of the system simple. The positioning element provides localized alignment precision (1 μm tolerance) at the critical coupling interface without requiring complex optical lenses throughout the system. This allows butt-coupling to be maintained while achieving relaxed tolerance in the critical zone.

Inventive Principle:
Principle #3Local quality

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 achieves precise alignment and minimizes coupling loss, ensuring high coupling efficiency and reliability in optical device assembly, suitable for mass production of high-performance optical devices with reduced costs.

Implementation Method 1

a bonding element is flowed along the locating portions of the walls and is solidified so as to secure the optical device on the holder

Methodology Applied
Scientific EffectAdhesion: Adhesive

Data Source

PatentEP3553577B1Optical device assembly comprising a single-mode optical device secured on a holder and method of securing the same
Publication Date: 2021.07.28 NOKIA SOLUTIONS & NETWORKS OY
  • EP3553577B1 patent drawingFigure 1~2d
  • EP3553577B1 patent drawingFigure 3~4b
  • EP3553577B1 patent drawingFigure 5a~5b

AI summary

The present application concerns an optical device assembly comprising a single-mode optical device secured on a holder, the active devices being optoelectronic devices mainly based on Group III-V materials used for telecom/datacom applications The present application also concerns a method of securing the same.