Fiber optic sensors are designed to measure various parameters. The distributed fiber optics sensor has been a very promising candidate for the structural health monitoring. In this thesis, we characterized LEAF (Large Effective Area Fiber) fiber’s Brillouin scattering spectrum and investigated its potentiality for the distributed Brillouin temperature and strain sensor. Optical fibers with complex refractive index profiles are applied to improve the Brillouin threshold by varying the Brillouin linewidth. As LEAF fiber has a modified refractive index profile, we investigated its Brillouin linewidth’s dependence on the square of the pump light’s frequency. We verified the Brillouin frequency’s variation with input SOP experimentally for LEAF fiber in the spontaneous regime. This sets a limitation for the frequency resolution of distributed Brillouin sensors. We also realized a simultaneous temperature and strain sensor with LEAF fiber applying the Brillouin optical time domain analysis. Based on the direct detection of LEAF beat frequencies, a simultaneous strain and temperature sensor was demonstrated.

Thesis (Ph. D.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 112-121.

Techn. Hochsch., Diss., 2000--Aachen.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 129-133).

Techn. Universiẗat, Diss., 2005--Darmstadt.

Techn. Universiẗat, Diss., 2005--Berlin.

Fiber optic sensors are designed to measure various parameters. The distributed fiber optics sensor has been a very promising candidate for the structural health monitoring. In this thesis, we characterized LEAF (Large Effective Area Fiber) fiber’s Brillouin scattering spectrum and investigated its potentiality for the distributed Brillouin temperature and strain sensor. Optical fibers with complex refractive index profiles are applied to improve the Brillouin threshold by varying the Brillouin linewidth. As LEAF fiber has a modified refractive index profile, we investigated its Brillouin linewidth’s dependence on the square of the pump light’s frequency. We verified the Brillouin frequency’s variation with input SOP experimentally for LEAF fiber in the spontaneous regime. This sets a limitation for the frequency resolution of distributed Brillouin sensors. We also realized a simultaneous temperature and strain sensor with LEAF fiber applying the Brillouin optical time domain analysis. Based on the direct detection of LEAF beat frequencies, a simultaneous strain and temperature sensor was demonstrated.

<p> Brillouin scattering technique is used to investigate the transverse acoustic phonon in (KBr)1-x(KCN)x alloy as a function of temperature for CN- concentration ranging from 0.20 to 0.50. Anomalies in phonon frequency and linewidth are observed and discussed in terms of coupling of the acoustic phonons with orientational motion of CN- ions based on a dynamic microscopic model suggested by Michel et al. The frequency and concentration dependence of the freezing temperature, which marks the formation of an orientational glass state, is examined.</p> <p> A high resolution tandem Fabry-Perot interferometer yields the first evidence of a complex spectrum which consists of the phonon peak and new equal-spaced modes. The Bayesian deconvolution technique is used to extract the spectra. The concentration, time and temperature dependence of these new modes are presented. It is proposed that they arise from the modification of the tunneling levels of the CN, and appear to have the uniform density of states which is the characteristic property of the glass.</p> / Thesis / Master of Science (MSc)

No description available.

In the past two decades, integrated photonics and nonlinear optics have flourished alongside one another. New developments in materials science and fabrication technologies have delivered lower loss photonic platforms and commercial foundries can produce high quality photonic devices in large quantites. These advances in photonics have allowed for new applications of nonlinear optics for quantum technologies, optical sensing and spectroscopy, and optical frequency combs. The challenge remains to integrate the lasers needed for these nonlinear photonic devices onto the same photonic platform and fully realize the size, cost, and power savings promised by photonic integration. In this dissertation we explore new applications of nonlinear optics that can enhance the functionality of integrated lasers. In the first part of this dissertation, we explore the use of additive pulse modelocking (APM) on an integrated platform for generating a high power, low repetition rate modelocked laser to achieve a fully integrated self-referenced frequency comb. We report on simulations that identify key criteria for APM lasers and compare design alternatives for the gain medium and modelocking element. We also report on the progress of experiments towards buliding an APM using semiconductor gain and the challenges associated with this goal. In the second part, we present a new theory for laser linewidth reduction called nonlinear self-injection locking and demonstrate it experimentally using a fiber Brillouin oscillator. This technique combines the gain-narrowing effects from asymmetric nonlinear oscillators like a Brillouin oscillator with the frequency stabilization techniques of self-injection locking to reduce a laser’s linewidth below its Schawlow-Townes limit. We also present future applications of this theory that could be realized on a fully integrated photonic platform.