Serge Melle

A passive wavelength demodulation system for guided-wave Bragg grating sensors

A novel, passive, and self-referencing wavelength detection system (WDS) that measures the wavelength of the narrowband back-reflected spectrum of guided-wave Bragg gratings is described. This letter also reports on the use of such a detection system with fiber-optic Bragg gratings used as absolute strain sensors. The wavelength detection system demonstrated a 1% strain resolution of the total strain measurement range.<<ETX>>

A Bragg grating-tuned fiber laser strain sensor system

The development of a fiber laser sensor system which permits efficient interrogation of Bragg grating sensors is reported. A tunable erbium doped fiber laser which utilizes a broadband mirror and an intracore Bragg grating reflector in side-pump configuration is described. The wavelength of the laser oscillation is determined by the Bragg grating, which is remotely located and used as a strain sensor. This arrangement is used in conjunction with a passive wavelength demodulation system (WDS) to form a self-contained fiber laser strain sensor system, allowing efficient interrogation of the Bragg sensor. This device provides interrupt-immune sensing of static and dynamic strains with a bandwidth of 13.0 kHz.<<ETX>>

Practical fiber-optic Bragg grating strain gauge system

A fiber-optic strain gauge system for use in structural monitoring and smart-structure applications is described. The strain gauge uses a fiber-optic Bragg grating sensor to measure strain and a passive, wavelength demodulation system to determine the wavelength of the narrow-band, backreflected spectrum from the grating sensor. The fiber-optic strain gauge system permits the measurement of both static and dynamic strains with a noise-limited resolution of 0.44 microstrain/√Hz, a measurement dynamic range of 27.8 dB, and a bandwidth of 250 Hz.

Wavelength demodulated Bragg grating fiber optic sensing systems for addressing smart structure critical issues

Smart materials and adaptive structures will require structurally integrated fiber optic sensing systems that can operate in practical situations including harsh environments. The intracore fiber optic Bragg grating has considerable potential to serve as the sensor of choice for this emerging field. However, its role has been impeded by the lack of a simple, passive and fast method of determining the wavelength of its narrow back-reflected optical signal. The authors report on the development of just such a wavelength demodulation system that is inexpensive and easily implemented with a minimum of equipment. Furthermore, they shall show that this approach lends itself to the development of an optoelectronic chip that could process many fiber optic sensors, yet be small enough to be integrated within the structural interface and thereby address the interconnect problem-potentially one of the most critical facing the development of practical smart structures.

Strain sensing using a fiber-optic Bragg grating

This paper reports on the development of a passive, fast demodulation system for use with in-fiber Bragg gratings used for strain or temperature measurements. This compact, potentially inexpensive self-referencing system permits absolute strain/temperature measurements over a wide dynamic range with fast temporal response by tracking the wavelength shifts of the narrow-band back-reflected Bragg spectrum. The wavelength, bandwidth and strain sensitivity of a Bragg sensor are discussed, and examples of both static and dynamic strain measurements are shown.

Fiber Bragg grating laser sensor

An erbium-doped fiber laser utilizing a broadband mirror as the end reflector and an intracore Bragg grating as the output coupler is designed and developed. This arrangement is used as a laser sensor to improve interrogation efficiency of intracore Bragg gratings over broadband sensor interrogation methods. Wavelength tuning of the fiber laser has been achieved by varying the temperature and strain on the Bragg grating, demonstrating an improved SNR with respect to the previous techniques that use broadband interrogation of the Bragg grating sensor.

Structural sensing using a fiber laser strain sensor

The development of a fiber laser sensor which permits efficient interrogation of Bragg grating sensors is reported. The fiber laser is linewidth-narrowed and tuned by a remotely located, sensing Bragg grating that is surface adhered to a structure under test. The Bragg grating- tuned fiber laser is used in conjunction with a passive wavelength demodulation system (WDS) to form a fiber laser strain sensor system (FLS3), which was used to track both static and dynamic strains on an aluminum beam. The FLS3 could measure strains with a resolution of approximately 4 (mu) (epsilon) and a bandwidth of 13.0 kHz. The viability of the laser strain sensor concept lends itself to the development of a compact, potentially embeddable smart sensor that would output demodulated sensing data directly to the user.

Optoelectronic smart structure interface: a key development for practical smart structures

The development of an Optoelectronic Smart Structure Interface (OSSI) will be required for the practical implementation of Smart Structure Technology. Such an interface will permit an extremely user-friendly interconnection to any Smart Structure component permitting the optical signals from an embedded optical fiber sensor array to be transmitted from the structure in a form most acceptable for that specific application. We have developed a simple, passive, fast response wavelength demodulation system for intracore Bragg grating sensors and have demonstrated real time strain measurements. Currently, we are exploring the use of this wavelength demodulation system with Bragg grating tuned fiber laser sensors and intend to show that such a system can form the basis of an OSSI.

Bragg fiber laser sensor

A tunable erbium fiber laser which utilizes a broadband mirror and an intracore Bragg grating reflector in a side-pump configuration is designed and developed. This arrangement is used as a laser sensor which greatly enhances the performance of a recently developed wavelength demodulation system by University of Toronto Institute for Aerospace Studies. Sensor design parameters for optimal performance in terms of the fiber laser geometry, doped fiber length, and the required pump energies are presented. Laser tuning with temperature has been achieved and shows much improvement in the SNR with respect to the previous techniques, i.e., interrogation of the Bragg grating sensor with a broadband source.