Linear Fibre Ring-Down Cavity Without Circulator Losses
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Solution Overview
Problem
Existing fibre-based cavity ring-down (CRD) configurations for remote sensing are limited by high losses due to the use of optical circulators, requiring an erbium doped fibre amplifier (EDFA) to compensate, and are not practical for remote sensing applications without complex setups.
Innovation Solution
A fibre linear cavity ring down device using a single fibre coupler with highly reflective thin-film mirrors at the ends and an optical time domain reflectometer (OTDR) for input/output, eliminating the need for additional mirrors and circulators, allowing for improved sensitivity and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an optical circulator is used in the cavity ring configuration for remote sensing, then the device can achieve remote sensing capability, but the intrinsic high losses of the optical circulator require an EDFA to compensate, increasing device complexity and power consumption
Solution Approach 1:
The patent removes the optical circulator from the cavity ring configuration, extracting the problematic component that caused high losses and required EDFA compensation. This simplifies the device structure while maintaining remote sensing capability through an alternative configuration using standard fibre couplers and mirrors.
Solution Approach 2:
The patent employs standard fibre couplers and mirrors that can serve multiple functions - forming the cavity structure, enabling remote sensing, and avoiding the need for specialized high-loss components like optical circulators. This universal approach reduces device complexity while achieving the same operational goals.
2Reliability
If an EDFA is added to compensate for optical circulator losses, then signal strength is maintained, but power consumption increases and device complexity increases
Solution Approach 1:
The patent eliminates the EDFA by removing the optical circulator that caused the signal losses in the first place. This extraction approach maintains signal strength through a loss-minimized configuration rather than adding active compensation components that consume power.
Solution Approach 2:
The patent converts the harmful effect of high losses (which required EDFA compensation) into a benefit by redesigning the configuration to inherently minimize losses. The new approach uses low-loss components and geometry to achieve both signal strength and low power consumption simultaneously.
3Adaptability or versatility
If a conventional cavity ring configuration is used, then remote sensing can be achieved, but the setup becomes complex and less practical for field deployment
Solution Approach 1:
The patent removes the optical circulator and EDFA from the conventional cavity ring configuration, extracting the components that made the system complex and difficult to deploy. The simplified configuration using standard fibre couplers and mirrors is much easier to install and operate in field conditions.
Solution Approach 2:
The patent employs standard, commercially available fibre couplers and mirrors that are inexpensive and readily replaceable, rather than specialized, expensive components like optical circulators. This makes the system more practical for field deployment where ease of operation and maintenance are critical.
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 configuration achieves enhanced sensitivity and practicality for remote sensing up to 10 km with improved signal-to-noise ratio and ease of integration into commercial systems, reducing complexity and power consumption.
Implementation Method 1
a linear cavity using a single fibre coupler and two thin-film mirrors located at the end of the fibre arms
Implementation Method 2
The part of light that comes out in each turn is monitored at the output. The result is a decaying exponential behaviour of the signal's intensity with time
Data Source
Figure 1(a)~1(c)
Figure 1(d)~2(a)
Figure 2(b)~2(c)
AI summary
Fibre linear cavity ring down device for decay time-based attenuation sensing, comprising a bi-directional fibre optic coupler having two fibre port coupling sides, a left-hand port side and a right-hand port side, and a port mirror; wherein signal input on one of said sides is coupled to signal output on the other of said sides; wherein the left-hand port side comprises a first fibre port (port 1) for coupling to an optical light source, the left-hand port side comprises a second fibre port (port 2) coupled to said port mirror (mirror 2), and the right-hand port side comprises a third fibre port (port 3) for coupling to a sensor fibre comprising one or more sensors and optically terminated by a sensor fibre mirror (mirror 1). The optical light source may be also an optical light receiver. The optical light source and receiver may preferably be an optical time domain reflectometer.