Distributed Optical Fibre Sensors Using Fast Optical Switches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Distributed optical fibre sensors using OTDR principles face limitations in sensing coverage and bandwidth due to propagation delay and power budget constraints, which restrict the maximum length and acoustic frequency that can be monitored, often requiring multiple interrogator units and increasing vulnerability to fibre damage.
Innovation Solution
Implementing a fast, non-mechanical optical switch to direct sequential interrogation pulses to multiple sensing optical fibres, allowing concurrent detection of acoustic vibrations along each fibre while optimizing pulse repetition rates to meet Nyquist criteria and extend sensing coverage without exceeding system range limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensing optical fibre is used to monitor all required locations, then the number of interrogator units is minimized, but the sensing coverage is limited by the maximum fibre length that can be interrogated with adequate signal to noise ratio
Solution Approach 1:
The system segments the sensing function across multiple optical fibres instead of using a single long fibre. Each fibre is interrogated separately, allowing the total sensing coverage to exceed the range limit of a single interrogator while maintaining adequate signal-to-noise ratio on each individual fibre.
Solution Approach 2:
The system transitions from monitoring a single fibre in one dimension to monitoring multiple fibres simultaneously, effectively expanding the sensing coverage in spatial dimensions while keeping the interrogator count manageable through time-multiplexed operation.
2Productivity
If the pulse repetition rate is increased to meet Nyquist criterion for high acoustic bandwidth, then the maximum acoustic frequency that can be correctly represented increases, but the propagation delay limits the maximum repetition rate
Solution Approach 1:
The system dynamically adjusts the pulse repetition rate for each optical fibre based on its length and the required acoustic bandwidth. Shorter fibres can be interrogated at higher repetition rates to capture high-frequency acoustic signals, while longer fibres use lower repetition rates, optimizing the trade-off between bandwidth and propagation delay constraints.
Solution Approach 2:
Different pulse repetition rates are applied to different optical fibres depending on their specific characteristics and the acoustic monitoring requirements at their locations, rather than using a uniform repetition rate for all fibres.
3Length of stationary object
If multiple interrogator units are deployed to extend sensing coverage beyond the range limit, then the sensing coverage distance increases, but the system complexity and cost increase
Solution Approach 1:
The sensing network is segmented into multiple optical fibres, each within the interrogator's range limit. A single interrogator cycles through these segmented fibres sequentially, achieving extended total coverage without requiring multiple interrogator units, thus avoiding the complexity and cost of deploying additional interrogators.
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 approach enables extended sensing coverage and increased acoustic bandwidth while minimizing the number of interrogator units, reducing costs and vulnerability by allowing multiple fibres to be used concurrently, with optimized pulse repetition rates for effective detection of acoustic signals.
Implementation Method 1
Implementing a fast, non-mechanical optical switch to direct sequential interrogation pulses to multiple sensing optical fibres
Implementation Method 2
distributed optical fibre sensors in which one or more physical parameters are sensed as a function of position along a plurality of sensing optical fibres from properties of probe light backscattered within the sensing fibres
Implementation Method 3
properties of probe light backscattered within the sensing fibres
Implementation Method 4
the propagation delay for backscattered light to return from the far end of a sensing optical fibre after an interrogation probe light pulse is launched at the proximal end of the fibre
Data Source
AI summary
Distributed optical fibre sensor measures vibration, as a concurrent function of position along each of a plurality of sensing optical fibres, from properties of probe light backscattered within the sensing optical fibres. The sensor includes a light-pulse-generating probe light source, a detector, an optical switch. The sensor is arranged to control the optical switch such that all of the sensing optical fibres can be used concurrently to detect acoustic vibration, and an analyser is arranged to determine vibration, as a concurrent function of position along each of the sensing optical fibres, from the detected backscattered probe light.