Long-Range Optical Fiber Sensing With Low-Loss Transport
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical fiber DAS and DTS systems are limited to a range of around 35 km due to attenuation and backscatter, which is insufficient for applications requiring longer ranges, especially in security and monitoring scenarios, and extending the sensing fiber length reduces sensing bandwidth.
Innovation Solution
A long range optical fiber sensor system with a sensing fiber located remotely from the interrogator, using a combination of high power and ultra-low loss transport fibers, optical amplifiers, and Raman pump sources to maintain pulse energy and increase bandwidth, allowing multiple pulses to travel along the transport fiber simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the sensing fiber length is extended beyond 35 km, then the monitoring range is improved, but the sensing bandwidth is reduced due to lower pulse repetition rates
Solution Approach 1:
The optical fiber system is segmented into two distinct functional parts: transport fiber for pulse transmission and sensing fiber for measurement. This segmentation allows the transport fiber to be optimized for low loss transmission over long distances while the sensing fiber length determines the pulse repetition rate and bandwidth, resolving the contradiction between range and bandwidth
Solution Approach 2:
The transport fiber acts as an intermediary between the interrogator and the sensing fiber, enabling pulses to travel long distances with minimal attenuation before reaching the sensing section. This intermediary allows extended range without compromising the sensing bandwidth that would be limited by total fiber length in conventional systems
2Length of stationary object
If multiple independent DAS systems are deployed to extend monitoring range, then the coverage is improved, but the system deployment cost and synchronization complexity increase
Solution Approach 1:
Multiple sensing sections are merged into a single continuous sensing fiber that is remotely coupled to one interrogator. This combining approach provides extended monitoring coverage while maintaining centralized control and synchronization, avoiding the complexity of coordinating multiple independent systems
3Device complexity
If standard optical fiber is used for long distance pulse transport, then the system simplicity is maintained, but the pulse attenuation increases significantly
Solution Approach 1:
The patent changes the key parameter of fiber attenuation by using ultra-low loss transport fiber with attenuation coefficients significantly lower than standard fiber. This parameter change enables long-distance pulse transport with minimal energy loss, solving the contradiction between simplicity and attenuation
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 system achieves high pulse repetition rates and sensing bandwidth over extended distances without reducing bandwidth, enabling effective monitoring beyond 35 km with improved signal-to-noise ratio and reduced system deployment costs.
Implementation Method 1
with a length of transport fiber connecting the two
Implementation Method 2
sensing apparatus arranged in use to detect light from the optical sensing pulses reflected and/or backscattered back along the sensing optical fiber
Implementation Method 3
sensing apparatus arranged in use to detect light from the optical sensing pulses reflected and/or backscattered back along the sensing optical fiber
Implementation Method 4
Raman pump sources providing Raman pump light into the transport fiber, the Raman pump light being arranged to interact with the optical sensing pulses to increase the power of the optical sensing pulses
Implementation Method 5
optical amplifiers, and Raman pump sources to maintain pulse energy
Data Source
AI summary
A long range optical fiber sensor such as a distributed acoustic sensor has a sensing fiber located remotely from the interrogator, with a length of transport fiber path connecting the two. Because no sensing is performed on the transport fiber then the pulse repetition rate from the interrogator can be high enough such that the pulse repetition rate and pulse power are optimised according to the sensing fiber length and hence sensing frequency response and sensitivity are also optimised according to the sensing fiber length.