Technical Papers
» INDEX
Fiber Optic Displacement Sensor
Fiber Optic Calorimeter
Non-contact fiber optic vibrometer
Buried Fiber Intrusion Detection Sensor with Minimal False Alarm Rates
All-Fiber Optic Coherence Domain Interferometric Techniques
Multi-Channel Interferometric Demodulator
Open Loop Digital Demodulator for Interferometric Sensors
Low Cost Fiber Optic Interferometric Sensor
Commercialization of Interferometric Interrogation Techniques for Fiber
Low-cost Interferometric TDM technology for dynamic sensing applications
» Fiber Optic Displacement Sensor,
P. G. Davis and I. J. Bush, Optiphase Inc.
G. S. Maurer; Raychem Corporation;
Fourth Pacific Northwest Fiber Optic Sensor Workshop, May 6, 1998
ABSTRACT
A novel low cost interferometric displacement sensor has been developed which tracks distance from the tip of a fiber optic probe. A unique interrogation technique is used which produces a 32-bit phase word, giving the system a dynamic range > 109. Therefore, a displacement resolution of < 0.01 nm can be achieved with a full range of 6 mm. The measurement range can be extended beyond 10 m by simply adjusting the digital fringe counter and sacrificing resolution yet maintaining the > 109 dynamic range. Demodulation rates of 40 kHz have been achieved which facilitates dynamic measurements. Results from an application to hard disk (HD) profilometry are presented.
Download Fiber Optic Displacement Sensor in PDF format (size 303K)
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P. G. Davis and I. J. Bush, Optiphase Inc.
S. Bayliss and C. Rudy, NIS-5 Safeguards Science and Technology, Los Alamos National Laboratory
Fourth Pacific Northwest Fiber Optic Sensor Workshop, May 6, 1998
ABSTRACT
A twin-bridge fiber optic calorimeter has been built and is currently being tested at Los Alamos National laboratory (LANL). The intrinsic optical phase shift induced by changes in temperature is measured in both a reference canister and a sample canister. This system incorporates two Michelson interferometers each with an optical path mismatch of 1.6km. A digital demodulation scheme is used which produces a 32 bit phase word which tracks up to 500,000 fringes with a resolution of 10-4 fringe, giving the system a dynamic range > 109. Both interferometers are demodulated simultaneously at a rate of 83 kHz. The phase difference between the reference and sample interferometers is proportional to the temperature difference between the canisters and therefore correlates to the power produced by the sample in question. The optical system performance will be described along with preliminary calorimetric measurement results.
Download Fiber Optic Calorimeter in PDF format (size 404K)
» Non-contact fiber optic vibrometer
Pepe Davis and Jeff Bush
ABSTRACT
A novel fiber optic vibrometer has been built and characterized. The vibrometer’s optical design is based on the Sagnac interferometer. Due to the nature of the Sagnac’s optical configuration, the optical phase shift induced by the surface being probed is differentiated, and therefore results in a measured optical phase shift that is directly proportional to the velocity of surface. The path matched Sagnac design eliminates the need for a coherent light source used in laser doppler vibrometers and offers great design flexibility for tuning the vibrometer’s frequency response and dynamic range to specific applications. The vibrometer’s dynamic measurement capabilities span as much as 8 decades (1 Hz noise band), where the maximum range may extend as high as 100m/s. A fiber optic Sagnac vibrometer was built and evaluated. Experimental results demonstrating the vibrometers performance are presented.
Download Non-contact fiber optic vibrometer in PDF format (size 789K)
» Buried Fiber Intrusion Detection Sensor with Minimal False Alarm Rates,
Jeff Bush, Carol Davis, Pepe Davis, Allen Cekorich, Fred McNair, Optiphase Inc.
Fourth Pacific Northwest Fiber Optic Sensor Workshop, May 6, 1998
ABSTRACT
A novel design approach for a highly reliable buried intrusion detection sensor is described. The design involves the use of a low cost depolarized Sagnac fiber interferometer with a "sensing loop" consisting of a delay line and buried fiber segment. The intrusion sensor is configured for an "all fiber" remote deployment where active components (source, receiver, demodulator) are located separately and connected to the sensor through an insensitive fiber tether. A robust and cost effective buried sensor "mat" design was developed. This design enabled high sensitivity as well as ease of deployment. Sensors were built and evaluated. Test results indicate an effective design.
» All-Fiber Optic Coherence Domain Interferometric Techniques
Jeff Bush, Pepe Davis - Optiphase, Inc.
Michael A. Marcus - Eastman Kodak Company
ABSTRACT
Traditional white-light scanning interferometers utilize bulk optic components mounted on a
mechanical scanning mechanism. Many emerging applications for these interferometers require
fiber optic probes. By design, such fiber compatible instruments are expensive and are limited to
slow scan rates. A new "all-fiber" design approach is presented, which reduces the cost
of the design and enables higher scan rates.
Download All-Fiber Optic Coherence Domain Interferometric Techniques in PDF format (size 493K)
» Multi-Channel Interferometric Demodulator(Patented process),
Jeff Bush and Allen Cekorich, Optiphase, Inc.
Clay Kirkendall, Naval Research Laboratory
ABSTRACT
This paper outlines recent progress made by Optiphase Inc. in the development of low-cost, high performance interferometric demodulators applied to multi-channel interrogation. The paper’s focus is on the Optiphase digital demodulation concept applied first for single channel operation and then to multi-channel operation. This paper also presents single and multi-channel demodulation test data taken from hardware developed for these applications.
Download Multi-Channel Interferometric Demodulator in PDF format (size 176K)
» Open Loop Digital Demodulator for Interferometric Sensors (Patented process),
Allen Cekorich and Jeff Bush
ABSTRACT
A highly efficient and accurate digital demodulation approach based on time domain sampling techniques is presented. Test results from constructed units demonstrate operational simplicity, low self noise and a very large linear dynamic range.
Download Open Loop Demodulator for Interferometric Sensors in PDF format (size 184K)
» Low Cost Fiber Optic Interferometric Sensor
Jeff Bush, Carol A. Davis, Fred McNair, Allen Cekorich, John Bostick
ABSTRACT
This paper outlines recent progress made by Optiphase Inc. in the development of low cost fiber optic interferometric sensors. The paper’s focus is on components under development, specific to Interferometric Fiber Sensors (IFS), which aren’t commercially available through normal telecommunications distribution channels.
Download Low Cost Fiber Optic Interferometric Sensor in PDF format (size 401K)
» Commercialization of Interferometric Interrogation Techniques for Fiber Sensing Applications
Jeff Bush and Allen Cekorich
ABSTRACT
Optiphase, Inc. develops and manufactures fiber optic interferometric sensing and
measurement systems. Principal activities involve the commercialization of this technology in
two distinct categories: 1) Interferometric Demodulation; and 2)White-Light Coherence Domain Systems.
» Low-cost Interferometric TDM technology for dynamic sensing applications
Jeff Bush, Allen Cekorich
ABSTRACT
A low-cost design approach for Time Division Multiplexed (TDM) fiber-optic interferometric interrogation of multichannel sensor arrays is presented. This paper describes the evolutionary design process of the subject design. First, the requisite elements of interferometric interrogation are defined for a single channel sensor. The concept is then extended to multi-channel sensor interrogation implementing a TDM multiplex scheme where “traditional” design elements are utilized. The cost of the traditional TDM interrogator is investigated and concluded to be too high for entry into many markets. A new design approach is presented which significantly reduces the cost for TDM interrogation. This new approach, in accordance with the cost objectives, shows promise to bring this technology to within the threshold of commercial acceptance for a wide range of distributed fiber sensing applications.
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