Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse...
Transcript of Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse...
Overview of Fiber Optic Sensing for Energy Applications
Anbo Wang
Center for Photonics Technology
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061-0111
Tel: (540)231-4363 E-mail: [email protected]
Core
Optical fiber
Cladding
θ
n1
n2
When θ is greater than θc=sin-1(n2/n1), the light can be guided.
Principle of an optical fiber
Light out
Why fiber sensors attractive?
• High temperature capability
• Chemically inert
• Remote operation
• Immunity to electromagnetic interference
• Non-electrically conducting
• Sensor multiplexing/distributed measurement
Overview of CPT Sensor Research
350µm
Laser welding points
Air gap
Pressure and temperature sensors tested in Chevron oil well
Acoustic sensors (70-250kHz) tested in Northfleet 400kV transformer
PHOTONIC SENSORS Fabrication and instrumentation Applications
Fiber Fabrication
Micro- Fabrication
Epoxy-Free Bonding
Nano-Film Assembly
Signal Processing
Distributed Sensing
Gasifier Temperature Monitoring
Oil Downhole Measurement
Partial Discharge Detection
Dynamic Engine Pressure
Monitoring
Pressure sensors tested on Virginia Tech Engine
Sapphire fiber temperature sensor testing in TECO coal gasifier
MMF
SMF
Splice point
Gallery of the CPT Sensors
Intrinsic Fabry-Perot Sensors
SMF SMF MMF
onL ϕπλ
ϕ +⋅=∆ 22
λ is the light wavelength in vacuum and is a constant.
),,(22 λϕϕπλ
ϕ nLnLo ∆++⋅=∆
“Decoding the spectra of low-finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42 (2011). “Toward eliminating signal demodulation jumps in optical fiber intrinsic Fabry-Perot interferometric sensors,” J. Lightwave Tech. 29 (13), 1913-9(2011) “Phase Term in the Spectrogram of SMS-IFPI Fiber Sensor and Its Influence on White-Light Interferometry Based Sensor Signal Demodulation,” Appl. Opt., 49, 4836 (2010).
oϕ
MMF
SMF
Splice point
Porous Clad Optical Fiber for High Temperature Fast Gas Sensing
100μm
1520 1530 1540 1550 1560 1570-16
-14
-12
-10
-8
-6
-4
-2
0
2
Wavelength (nm)
Volta
ge (m
V)1562 1563 1564 1565 1566 1567 1568 1569 1570-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
Wavelength (nm)
Volta
ge (m
V)
Transmission Spectrum
acetylene
CO
Single-Crystal Sapphire Fiber Sensors Silica Fiber Limitations 1) Thermal diffusion of germanium dopant 2) Glass creep under stress at elevated temperatures 3) Max temperature is usually between 800 and 900C. For higher temperatures, different fibers are needed. Sapphire Properties 1) High melting point (2045C) 2) Excellent optical transparency from near UV to several
microns 3) Commercial availability
Sapphire Fiber Temperature Sensor
Alumina probe
75µm single-crystal sapphire fiber 100/140µm silica fiber
Sapphire wafer Silica-sapphire fiber splice broadband light
to spectrometer
Fiber Wafer
Input light
Output light
IFPI Sensor Test on NETL Engine Rig
Field Test at Tampa Electric Corporation
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90
Days of Operation
Nor
mal
ized
Tem
pera
ture
(A.U
.)
Preheat
Burner Change
Start-Up
Sapphire sensorComm. Failure
Thermocouples
The sapphire temperature sensor probe has now survived more than 110 days in the coal gasifier.
Example Sensors
350µm
Laser welding points
Air gap
390nm tip
Wavelength-Scanning TDM
Important Feature: Use weak IDENTICAL FBGs.
Acknowledgement
Thanks go to CPT faculty, staff and graduate students who were involved in the presented research. We are also grateful to DOE NETL for their support to the presented research.