distributed sensor technology optical fibre in a new …...the fibre is the sensor • optical...
TRANSCRIPT
Distributed sensor technologyOptical fibre in a new light?
Question 1
• Which of these can be used to measure temperature to 0.007°c?
Digital thermometer Mercury in glassthermometer
50/125 Fibre
A B C
Question 2
• Which of these can be used to record sound?
Microphone 50/125 Fibre
A B C
Loudspeaker
Question 3
• Which of these can be used to measure strain?
Piezo film sensor Pressure gauge 50/125 Fibre
A B C
Agenda
• How it works the physics
• Case Study : Strain sensing
• Case Study : Audio sensing
• Case Study : Temperature sensing
• Questions & Answers
Distributed Sensor Technology
The fibre is the sensor
• Optical losses determine the maximum distance we can transmit data over a standardised fibre link
• Material attenuationAbsorption by atoms, at specific wavelengths
• Waveguide attenuation Bends in the fibre macrobends, microbends
• Fibre coupling lossesSplices, connectors etc…
• Scattering processes : Collectively called ‘noise’ in a comms link. Rayleigh, Brillouin, Raman
LordRayleigh1842-1919
SirRaman1888-1970
MrBrillouin1889-1969
Rayleigh Scattering
• Technique used by traditional OTDR’s
• The elastic scattering of light by particles much smaller than the wavelength of the light. The wavelength of the backscattered photon is unchanged.
• Rayleigh scattering of sunlight in the atmosphere is the reason for the blue colour of the sky and the yellow tone of the sun itself.
• The sun appears redder near the horizon as the light passes through more air which scatters almost all of the blue light.
• Blue light is scattered more than red.
• Rayleigh scattering is an important limitation in a fibre optic comms links.
�Brillouin
RamanRayleigh
Stokes Anti-stokes
Brillouin Scattering
• Occurs when light interacts with optical density
variations and changes its energy (frequency) and
path
• Any compression of the glass will change the index
of refraction
• Even tiny vibration transmitted to the fibre affects
the density and can be detected
• Used for strain and audio measuring
�Brillouin
Raman
Rayleigh
Stokes Anti-stokes
Raman Scattering
• A small fraction of scattered light (approximately 1
in 10 million photons) is scattered by an excitation.
The backscattered photons have a different
frequency from the source photon.
• There are two Raman signal elements the stokesand anti-stokes reflections.
• The stokes reflection is weakly temperature
sensitive and is not very useful for temperature
sensing.
• The intensity of backscattered light at antistokes
wavelengths increases with temperature.
• Antistokes Raman Scattering is therefore used for
temperature sensing.
�Brillouin
Raman
Rayleigh
Stokes Anti-stokes
Measuring distance
1/100,000 seconds = 1m2/100,000 seconds = 2m3/100,000 seconds = 3m
1m 2m 3m
Simple principle – How OTDR’s work today
Raman Scattering – AntiStokes for temperature
• Raman scattering is the interaction of a photon with molecular vibrations(Only 1 in 10,000,000 photons)
• Stokes Red Shift• Molecule absorbs some of the
photons energy
• Reflected photon has lower energy (red shift)
• AntiStokes Blue Shift• Molecule loses energy
• Reflected photon has higher energy (blue shift)
• Temperature is determined from the backscattered Stokes / AntiStokes power ratio
Stokes molecule absorbs energy
Antistokes molecule loses energy
• Measures using standard 50/125 zip cord
• 4 x sensing fibres each up to
4 km in length (MM 50/125 fibre)
• 2.0m length resolution
• 8000 points per unit
• 0.1°c to 0.01°c accuracy0.1°c = 15 Seconds
0.01°c = 3000 Seconds
Temperature accuracy & resolution
Length
Tem
per
atu
re
Advantages of fibre as a temperature sensor
• Simultaneously measures temperature and position over
long distances
• Low cost – the sensor is made from standard 50/125
optical fibre zip cord very cost effective
• Immune to shock/vibration and electromagnetic
interference
• No electronics, wireless, batteries or moving parts in
monitoring zone. Totally passive, minimal maintenance.
• Inherent high reliability (fibre has a design life of 30+ years)
• High temperature range 200°c to +500°c
• Extremely small for access in legacy areas with restricted
space
• Easily installed in without any downtime or interruption of
service
Case Study
Acoustic Measurement
Acoustic Measurement Applications
• Any acoustic event along the entire fibre
length creates sound waves in the ground
which cause microchanges in the shape of
the fibre which disturbs the backscatter. An
acoustic signal is then rebuilt from the
change in the backscatter data.
• A powerful processing architecture for
analysing acoustic activity has been built,
drawing upon decades of military sonar
research.
• Protecting borders, pipelines, railways from
unauthorised activity.
• Provides a dependable means of monitoring
traffic flow hard shoulder shared usage
Case Study
Temperature Sensing
Wind Farm Power Cables
Wind Farm Power Line Monitoring
• In UK power distribution must be owned by a different
company to power generation.
• Multimode comms fibre in power cable is used to
measure the temperature of the cable core.
• Cables run 60km from offshore substation to land.
• Using Dynamic Cable Rating software the cable
utilisation can be doubled.
• Occasional peak loads for short periods can be
accommodated based on thermal performance of sub
sea cable.
• Turbines no longer need to be turned off when
generated capacity exceeds cable capacity.
Case Study
Temperature Sensing
Large Data Centre
Data Centres Energy Consumption is Critical
• Carbon Reduction Commitment
Mandatory legislation
Voluntary schemes
• BS EN 16001
• The Green Grid PUE
• EU Code of Conduct on Data
Centre Energy Efficiency
Data Centres Security of Supply
• UK Electricity consumption is increasing
• UK generation capacity is declining
• Nuclear capacity has not been replaced
• Coal replaced by gas powered stations
• Since 2004 UK is a net importer of gas
• Electric vehicles will increase electricity
demand still further
1 Electric Car = 3 Households
Raising Temperature = Saving Money
• Most UK data centres currently run between 1820°c
• In 2008 ASHRAE TC 9.9 second edition recommend :
• These temperatures allow almost 100% use of free
cooling (no chillers are required)
• For every 1°c degree the temperature is increased
savings of around 5% per year can be achieved.
Class Allowable Recommended
Class 1 32°c 27°c
Class 2 35°c 27°c
Large Data Centre
• The client had difficulty monitoring
temperatures in realtime
• Problems with hotspots
• Overcooling in some areas
• Wanted to increase supply air
temperature but feared breaching SLAs
• Required high definition temperature
measurement across the data centre
• Using award winning technology
• Innovative use of fibre optic cable to
measure temperature
Monitoring Alternatives
• Air temperature monitoring
• High Level – Fibre optic zip cord attached to high level
catenary support cables.
• Run down hot and cold isles above racks
• Run around equipment in racks
• Subfloor to detect supply air temperatures
• Leak Detection
• On floor slab to detect water leaks from cooling systems
• Bus bar monitoring
• Along electrical bus bars to measure temperature
particularly around joints. Detect early signs of hot spots.
• High Definition and real time view of data centre energy consumption
• Real time display of critical hotspots
• Monitoring Current and historical analysis of temperature data
• Notification – User defined zones and
alarms (average, min, max)
• Control DCView will trigger alarms and
send SMS / SNMP / Email / ModBus to
the data centre manager
• Verification – automate audit of energy
reduction with high definition
benchmarking
Visualisation Software
Data Centre Floor Plan
Case Study Results
• Our clients need to safely increase temperatures
from 18°c to 27° over the next 5 years
• For every 1°c degree the temperature is increased
cost savings of around 5% per year can be achieved
• You need high definition monitoring tools to
manage the energy being used
• Verify the effectiveness of all improvements
• Full historical record of thermal performance
• Visualise energy consumption in real time for staff,
suppliers and clients
• By monitoring in high definition the client can
minimise the risks as temperatures increase
• The result; Energy reduced and money saved!
Summary
• There are an incredible number of
applications for fibre optics beyond their use
as a simple comms links.
Acoustic Monitoring
PowerMonitoring
Data CentreMonitoring
Fibre OpticChristmas Tree
Contact details