Fiber Laser Interlock Using Reflection Ratio Break Detection
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Solution Overview
Problem
Existing systems for monitoring the integrity of transmission fibers coupled to laser sources may not react quickly enough to fiber breaks or disconnects, and can trigger false positives due to power drops caused by elements other than the fiber span.
Innovation Solution
A system utilizing a pair of monitoring photodiodes and a beam splitting device to continuously measure the output power and back-reflected light from a transmission fiber, calculating a ratio of reflected to transmitted light, and shutting down the laser source if the ratio exceeds a defined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a system level monitor is used to monitor power at both ends of the fiber span, then the monitoring can detect fiber breaks, but the reaction time is slow and false positives occur
Solution Approach 1:
The patent applies preliminary action by continuously monitoring the back-reflected light from the fiber using a photodiode positioned to receive light reflected from the fiber endface. This continuous monitoring is performed in advance before a actual fiber break occurs, enabling immediate detection when a break happens without the delay of system-level power measurements at both ends.
Solution Approach 2:
The patent uses an intermediary approach by introducing a photodiode as a mediator that directly measures the back-reflected light from the fiber. This intermediary measurement device provides direct feedback about fiber integrity without requiring complex system-level measurements, enabling faster and more reliable detection of fiber breaks or disconnects.
2Reliability
If power monitoring is performed at both ends of the fiber span, then fiber integrity can be monitored, but false positives are triggered by power drops unrelated to fiber breaks
Solution Approach 1:
The patent applies the taking out principle by extracting the essential monitoring function from the complex system-level approach. Instead of monitoring power at both ends and performing calculations, the invention extracts only the critical measurement of back-reflected light using a simple photodiode, eliminating the complexity of dual-end monitoring while maintaining reliable fiber break detection.
Solution Approach 2:
The patent substitutes the mechanical/system-level monitoring approach with an optical measurement approach. Instead of using complex electronic systems to measure power at both ends and calculate loss, the invention uses optical measurement of back-reflected light intensity, which directly indicates fiber integrity without requiring complex processing or multiple measurement points.
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 solution enables immediate and accurate shutdown of the laser source upon detection of a fiber break or disconnect, thereby ensuring eye safety and preventing accidental exposure to high-energy laser beams.
Implementation Method 1
a beam splitting device positioned along an optical signal path at an output from a laser source, and is used for directing a first, small portion of the optical output beam away from the optical signal path and passing a second, large portion of the optical beam along the optical signal path
Implementation Method 2
A first monitoring photodiode of the pair is disposed to receive the first, small portion of the optical beam redirected by the beam splitting device and generate therefrom a reference photocurrent based upon a transmitted power of the optical beam
Implementation Method 3
a second monitoring photodiode of the pair is disposed to receiving any reflected beam incoming from the associated optical transmission fiber, where a back-reflected beam is indicative of a loss of continuity along the associated optical transmission fiber, the second monitoring photodiode generating a photocurrent of a level commensurate with the power level of the back-reflected beam
Data Source
AI summary
A system is proposed for continuously monitoring the integrity of a transmission fiber coupled to a laser source and immediately shutting down the laser source upon recognition of any type of cut, break or disconnect along the transmission fiber. A pair of monitoring photodiodes is included with the laser source and used to look at the ratio of reflected light to transmitted light, shutting down the laser if the ratio exceeds a given threshold. If a break is present, the power of the reflected light will be higher than normal, where a defined threshold is used to determine of the calculated intensity is indicative of a break. By using measurements performed in terms of decibels, the monitoring system needs only to take the difference in intensities to generate the reflection/transmission ratio output.