Multimode Beam Combiner Mode Expansion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional tapered fiber combiners experience a decrease in beam quality due to a decrease in mode areas along the taper, leading to high beam divergence and increased Beam Parameter Product (BPP), which complicates the combination of multiple optical beams into a single output fiber, especially at higher power levels.

Innovation Solution

A mode expander is applied as a mode adapter to increase the signal mode area prior to tapering and combining, using up-tapered regions or graded index lenses to maintain beam quality by increasing the mode field diameter and reducing cladding area, thereby minimizing the need for special taper designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional tapered fiber combiners are used to combine multiple optical beams, then the device structure is simple, but the beam quality deteriorates due to decrease in mode areas along the taper

Engineering Contradiction:

Improvecombiner structureVSAvoidbeam quality

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary action by expanding the mode area of optical beams before they enter the taper region. Mode expanders or mode adapters are positioned upstream to increase the mode field diameter and reduce the signal-to-cladding area ratio, so that when beams propagate through the taper, the mode areas remain sufficiently large to maintain beam quality and avoid excessive divergence.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the cross-sectional area decreases along the taper, then the combiner can combine multiple beams into a single output fiber, but the mode areas decrease leading to high beam divergence

Engineering Contradiction:

Improvebeam combination capabilityVSAvoidbeam divergence

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by counteracting the harmful effect of mode area decrease before it occurs. Mode expanders or mode adapters are introduced to increase the mode field diameter and reduce the signal-to-cladding area ratio in advance, compensating for the area reduction that will occur during taper propagation. This preliminary counter-action prevents excessive beam divergence and maintains beam quality throughout the combining process.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If mode areas are increased prior to tapering, then beam quality is maintained, but the device complexity increases due to additional mode expanders or mode adapters

Engineering Contradiction:

Improvebeam qualityVSAvoidcombiner structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies merging by integrating the mode expansion function directly into the combiner structure itself. Rather than adding separate, discrete mode expander components, the design incorporates mode-expanding tapers or integrated mode adapters as inherent parts of the combiner assembly. This merging approach maintains beam quality while reducing overall device complexity and improving manufacturability.

Inventive Principle:

Principle #5Merging (Combining)

4Ease of manufacture

If conventional taper designs are used, then manufacturing is simple, but special taper designs are required to maintain beam quality at high power levels

Engineering Contradiction:

Improvetaper fabricationVSAvoidbeam quality at high power

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies parameter changes by modifying the geometric parameters of the taper structure itself to achieve mode expansion. By adjusting the taper angle, length, and profile to create an expanding mode field diameter along the propagation direction, the design maintains beam quality at high power levels without requiring complex additional components. This parameter optimization allows conventional manufacturing techniques to produce tapers with built-in mode-expanding characteristics.

Inventive Principle:

Principle #35Parameter changes

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 approach maintains high beam quality by reducing beam divergence and keeping the Beam Parameter Product low, even at high power levels, avoiding the leakage and quality degradation issues associated with conventional combiners.

Implementation Method 1

Each mode expander comprises a core with a mode expander between an input and an output of the core. The mode expander increases a mode area of an optical beam as the optical beam propagates through the mode expander.

Methodology Applied

Scientific EffectMode expansion: Waveguide (optics)

Implementation Method 2

The combiner exhibits a down-tapering between an input end and an output end. The down-tapered region decreases a mode area of an optical beam as the optical beam propagates through the down-tapered region.

Methodology Applied

Scientific EffectTapering: Waveguide (optics)

Data Source

PatentUS10114172B2Multimode beam combiner

Publication Date: 2018.10.30 OFS FITEL LLC

AI summary

An up-taper is applied by a mode adapter to increase a signal mode area prior to tapering and combining.