Optical Amplifier Reflected Light Elimination via Raman Scattering

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Solution Overview

Problem

MO-PA type optical amplifiers and fiber lasers are vulnerable to damage from reflected light, which is amplified and can destroy the oscillator, and conventional solutions like optical isolators are costly and increase optical loss.

Innovation Solution

Incorporating a reflected-light wavelength conversion fiber that uses Stimulated Raman Scattering to convert reflected light into a different wavelength, which is then eliminated by a filter, such as a fiber grating or dielectric multi-layer filter, to prevent damage to the oscillator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an optical isolator is used to reduce reflected-light power, then the oscillator is protected from damage, but the device becomes large-sized, high-priced, and increases optical loss

Engineering Contradiction:

Improveoscillator protection from reflected lightVSAvoidoptical loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the wavelength parameter of the reflected light by using Stimulated Raman Scattering in the optical fiber. The reflected light at the original wavelength is converted to a different wavelength (shifted by the Raman scattering effect), and then a filter removes the wavelength-converted light, protecting the oscillator without using a traditional optical isolator

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/optical isolator system with an all-fiber solution using Stimulated Raman Scattering and optical filtering. This substitution eliminates the need for bulky, expensive optical isolators while achieving the same protective function with lower optical loss

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If an optical isolator is used to reduce reflected-light power, then the oscillator is protected from damage, but the device becomes large-sized and high-priced

Engineering Contradiction:

Improveoscillator protection from reflected lightVSAvoiddevice size and cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the wavelength parameter of the reflected light through Stimulated Raman Scattering, converting it to a different wavelength that can then be filtered out. This approach uses standard optical fiber and filter components instead of specialized optical isolators, reducing device size and cost

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses inexpensive optical fiber and standard optical filters instead of expensive, specialized optical isolators. The solution employs readily available, low-cost components to achieve the protective function

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If Stimulated Raman Scattering is used to convert reflected light wavelength, then the oscillator is protected without increasing device size or cost, but the oscillation wavelength or pulse width may be affected

Engineering Contradiction:

Improveoscillator protection from reflected lightVSAvoidoscillation wavelength and pulse width stability

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies Stimulated Raman Scattering only to the reflected light traveling in the reverse direction through the optical fiber, while the forward-propagating oscillation light maintains its original properties. The wavelength conversion is localized to the reflected light path, leaving the main oscillation characteristics unchanged

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces an optical filter as an intermediary component that selectively removes the wavelength-converted reflected light while allowing the original oscillation light to pass through unchanged. This mediator ensures that only the harmful reflected light is affected

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Effectively prevents oscillator damage from reflected light without affecting the oscillation wavelength or pulse width, reduces optical loss, and is more cost-effective than traditional solutions, with minimal increase in parts and no need for complex control circuits.

Implementation Method 1

a reflected-light wavelength conversion fiber which is provided on an optical path between the oscillator and the amplifier and which converts a wavelength of reflected-light traveling toward the oscillator due to Stimulated Raman Scattering

Methodology Applied

Scientific EffectStimulated Raman Scattering:

Data Source

PatentUS8004753B2Optical amplifier, fiber laser, and method of eliminating reflected light

Publication Date: 2011.08.23 FUJIKURA LTD

AI summary

A MO-PA type optical amplifier is provided which includes an oscillator and an amplifier including a fiber for optical amplification, including: a reflected-light wavelength conversion fiber which is provided on an optical path between the oscillator and the amplifier and which converts a wavelength of reflected-light traveling toward the oscillator due to Stimulated Raman Scattering; and a filter which is provided on the optical path between the oscillator and the amplifier and which eliminates the wavelength-converted light.