Transport research opportunities and needs: What can fibre optics do for us? Stephen James Engineering Photonics

Transport research opportunities and needs: What can fibre optics do for us? Stephen James Engineering Photonics

My research interests Development and practical application of optical fibre sensors Multiplexed arrays of sensors in a single optical fibre. Physical Measurands (temperature, strain pressure..) Chemical Sensors Applications in Aerospace, Manufacturing, Transport, Environment, Energy, Civil Engineering and Medicine Highly collaborative and interdisciplinary

Optical fibres Low loss optical transmission lines High data capacity, low attenuation Properties of the light in the optical fibre are influenced by the surrounding environment Finding wide-spread use in instrumentation and sensing

Optical fibres Advantages Small dimensions (diameter of 125 μm) Light weight Dielectric material - insulator Immune to electromagnetic interference Flexible, strong Chemically inert Safe for use in hazardous environments Downlead insensitivity Compatible with composite materials

The market for fibre optic sensors Established markets Oil & gas seismic - in-well, pipelines Wind energy - turbines Geothermal Utility power lines Military hydrophone, security, shipboard Homeland security intrusion / chemical Infrastructure Industrial process control

Intrinsic optical fibre sensors Point sensor Multiplexed sensors Distributed sensor

Optical Fibre Sensors: Measurands and Applications Measurands Strain Temperature Pressure Displacement Vibration Liquid level Humidity Chemical species Chemical concentration ph Acceleration Particle size Refractive index Magnetic field Current Voltage Shape Curvature Velocity Thickness Torsion Acoustic Emission

Optical Fibre Sensors For Transport Systems Smart transport systems need sensors Traffic flow, infrastructure condition, efficient use of assets, safety, legal compliance Current installed road traffic monitoring relies upon inductive loops and cameras. Condition monitoring often relies on visual inspection New developments exploit GPS on smart phones and car navigation systems to provide real time traffic flow and smart phone accelerometers to monitor road conditions. Can optical fibres offer anything?

Optical Fibre Sensors For Transport Systems Examples of two optical fibre sensing technologies Distributed Acoustic Sensing Fibre Bragg Gratings Applications in Road Rail Infrastructure monitoring Aim to provide a flavour of what the technologies offer for use in transport systems

Distributed Sensing The sensor is continuous along the length of the fibre Capable of monitoring an environmental disturbance as a continuous function of distance Can measure the magnitude of a disturbance Can identify its location Based upon radar/time of flight techniques Short laser pulse coupled into the fibre Monitor the backscattered signal Measurement based upon perturbation of temporal or spectral properties of the return.

http://www.optasense.com/ Distributed Acoustic Sensing Borehole and pipeline monitoring. http://silixa.com/ Security LaserFocusWorld June 2015

Transport application 40 km 40 km Single mode, telecoms optical fibre Interrogation unit R. Pinchen et al., "Congestion and incident management application for distributed acoustic sensing technology NZTA case study," ITS Asia Pacific Forum, Auckland, New Zealand (Apr. 2014).

What can be monitored? Analysis of the acoustic signals allows: Measurement of traffic flow rate Measurement of journey times Identify congestion and location of incidents Identify when and where a vehicle stopped on hard shoulder Identify when pedestrians on highway Weigh in motion Road condition and pothole detection Possible to use dark fibres in existing telecommunications networks

Optical Fibre Bragg Grating Sensors Optical fibres allow the development of small, light weight, high strength, flexible and EMI immune sensors. The Cranfield team has facilities for fabrication of custom optical fibre sensor arrays, and has extensive experience of design, build and field deployment of sensor systems Label a short (5mm) section of optical fibre which can be interrogated to determine local environmental parameters e,g. strain, temperature. There can be 100s of sensors on a single fibre.

Practical Applications of Optical Fibre Sensors: Monitoring rail components

Practical applications: Monitoring rail components FBG sensor arrays bonded to fishplates, switchblades and stretcher bars for condition monitoring Fishplate bolted joint between rails Failure modes: Loosening of the bolt Cracking Switches allow train to change tracks Failure modes: Wear of the end of switch blade Cracking Stretcher bars maintain gap between rails Failure modes: Cracking

Optical fibre based monitoring system

Installation of sensors Simple process, no complex power cables or signal lines Surface preparation Attaching sensors to switchblade cyanoacrylate, 2 part adhesive Array protection

Results: Switchblades

Monitoring a switchblade Immediately after installation of the switchblade (2011-04) it is possible to: distinguish individual wheel crossings, separate bogies 2 and 3 From November onwards: Response to bogies 2 and 3 merge Wheel crossing becomes less distinct

Results:Fishplates

Monitoring a fishplate 320 Nm 270 Nm 320 Nm 150 Nm 150 Nm 0 Nm 270 Nm 0 Nm

Other rail applications Analysis of special content of data could allow: Axle counting and train type identification Speed/acceleration Weigh in motion Detection of wheel flats Other areas of interest Pantograph-Catenary loading Filograno, IEEE Sensors J 12, 85 (2012) Comolli, Proc. SPIE 7726, 772605 (2014)

strain (/microstrain) Infrastructure monitoring Tunnels Structural monitoring Temperature measurement/fire detection Intrusion Air quality Gue, Sensors 16, 748 (2016) Bridges Structural monitoring Crack detection 350 300 250 200 150 Acton Town Bridge FBG Strain Monitoring FBG9 FBG8 FBG7 FBG6 FBG5 100 FBG4 Embankments Slope stability 50 40 45 50 55 60 65 70 75 80 85 time(/s) Shi, IAEG2016 (2016)

Practical Applications of Optical Fibre Sensors: Monitoring Foundation Piles

Monitoring Foundation Piles using FBGS: Installation

Monitoring Foundation Piles using FBGS:Installation

Monitoring Foundation Piles using FBGS: Statnamic Testing

Monitoring Foundation Piles using FBGS: Statnamic Testing

Monitoring Foundation Piles using FBGS: Static Testing of hollow pile 30 m deep pile, 1.2 m diameter, 0.8m void in centre 50% concrete saving (manufacture and transport) Same performance as standard, solid pile

Microstrain (µs) Monitoring Foundation Piles using FBGS: Static Testing 100 0 2m -100-200 -300-400 6m 11m 2 8 m -500-600 16/08/2008 00:00 16/08/2008 12:00 17/08/2008 00:00 17/08/2008 12:00 18/08/2008 00:00 Time 18/08/2008 12:00 19/08/2008 00:00 19/08/2008 12:00 20/08/2008 00:00 16m 2 1 m 26m

Summary Outlined the means for using optical fibres as sensors Examples of distributed and multiplexed sensors applied to Monitoring road traffic Condition monitoring on a tram network The unique properties of optical fibre sensors offer great potential for applications in transport systems. Traffic monitoring Security Condition monitoring