Multi-port coupler with emitted light confining waveguide
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Solution Overview
Problem
Conventional multi-port couplers in high power optical amplifiers and fiber lasers suffer from LD damage due to reflected light, which is exacerbated by splice loss at the splicing point between the cladding pump fiber and the coupler, leading to reduced reliability and shortened device lifetime.
Innovation Solution
A multi-port coupler design featuring an emitted light confining waveguide with a higher refractive index than the cladding but lower than the core, surrounding the central signal fiber, effectively confines reflected light, preventing it from reaching the pump LD and reducing splice loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional multi-port coupler is used to couple multiple LDs to the cladding pump fiber, then high power output is achieved, but the pump LD is damaged by reflected light returning through the splicing point
Solution Approach 1:
An emitted light confining waveguide part is introduced as an intermediary structure between the core and cladding. This waveguide part with intermediate refractive index acts as a mediator that confines reflected light within the core region, preventing it from reaching the pump LD through the splicing point, thereby resolving the contradiction between high power output and LD reliability
Solution Approach 2:
The refractive index parameter is changed by introducing a waveguide part with intermediate refractive index between the core and cladding. This parameter change creates a refractive index gradient that confines reflected light within the core, preventing it from escaping to the pump LD while maintaining high power output capability
2Power
If the gain of the optical amplifier is increased to 20 dB or more to achieve high power amplification, then the output power reaches 1 W-1 kW, but the reflected light power becomes ten times higher than the pump LD power, causing LD damage
Solution Approach 1:
The harmful reflected light is converted into a confined optical mode within the core by the emitted light confining waveguide part. Instead of allowing the reflected light to damage the pump LD, the waveguide structure transforms it into a beneficial confined mode that can be managed and absorbed, converting the harmful effect into a controllable optical configuration
Solution Approach 2:
The emitted light confining waveguide part serves as an intermediary that intercepts and confines the reflected light before it can reach the pump LD. This intermediate structure prevents the harmful interaction between high power reflected light and the sensitive pump LD, enabling high gain amplification without damage
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
The solution significantly prolongs the lifetime of LDs by reducing damage from reflected light, maintaining high reliability in optical amplifiers and fiber lasers, with the waveguide structure efficiently confining and absorbing the reflected light, thereby protecting the pump LD.
Implementation Method 1
an emitted light confining waveguide part is provided around a core of a signal fiber located at the center, and the emitted light confining waveguide part whose outer diameter is larger than that of the core has a higher refractive index than a cladding and a lower refractive index than the core
Data Source
AI summary
A multi-port coupler for coupling an pumping light source to a cladding pump fiber for optical amplification, includes a central signal fiber and a plurality of pumping fibers arranged around the central signal fiber, the central signal fiber and the plurality of pumping fibers being unified and a front side is reduced in diameter, wherein an emitted light confining waveguide part is provided around a core of the signal fiber located at the center, and the emitted light confining waveguide part whose outer diameter is larger than that of the core has a higher refractive index than a cladding and a lower refractive index than the core and the emitted light confining waveguide part is formed continuously from a splicing point of the cladding pump fiber to a coupler front end branched into multiple fibers.