Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse...

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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]

Transcript of Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse...

Page 1: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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]

Page 2: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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

Page 3: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

Why fiber sensors attractive?

• High temperature capability

• Chemically inert

• Remote operation

• Immunity to electromagnetic interference

• Non-electrically conducting

• Sensor multiplexing/distributed measurement

Page 4: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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

Page 5: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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).

MMF

SMF

Splice point

Presenter
Presentation Notes
For EFPI, fringe visibility is a more important issue, but the additional phase term is less important because it shifts very little during measurement. For IFPI, fringe visibility is typically very high due to beam confinement inside the cavity, but the additional phase term can be very large, which is a potential cause of demodulation discontinuities.
Page 6: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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

Page 7: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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

Page 8: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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

Presenter
Presentation Notes
Now let’s look at the system. It’s the widely used white-light intereferometric system. Light from a wideband LED travels through a 3dB coupler to sensor, Gets reflected and detected by the spectrometer. Here we use OceanOptics miniature spectrometer. This is the structure of the sensor head. The sapphire fiber and the wafer are held by a alumina tube by high temperature adhesive. The sapphire fiber is coupled with 100/140um silica fiber by fusion splicing.
Page 9: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

IFPI Sensor Test on NETL Engine Rig

Page 10: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

Field Test at Tampa Electric Corporation

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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.

Page 11: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

Example Sensors

350µm

Laser welding points

Air gap

390nm tip

Page 12: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

Wavelength-Scanning TDM

Important Feature: Use weak IDENTICAL FBGs.

Page 13: Overview of Fiber Optic Sensing for Energy Applications · “Decoding the spectra of low -finesse extrinsic optical fiber Fabry-Perot interferometers,” Opt. Express, 24, 23727-42

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.