M.Sc Thesis

M.Sc StudentSherman Anatoly
SubjectExperimental Applications of Inverse Scattering Theory in
Fiber Gratings
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Moshe Horowitz


Fiber Bragg gratings (FBGs) and long period gratings (LPGs) are important elements in the fields of optical communications and optical metrology. In spite of the important advantages of these gratings, such as small dimensions, low weight, and low cost, the use of these elements is severely limited owing to grating imperfections. By developing methods to accurately measure the structure of fiber gratings, it may become possible to significantly improve performance of these elements as well as to develop novel fiber sensors. The structure of a FBG can be extracted by measuring its complex reflection spectrum and using an inverse-scattering (IS) algorithm. The main drawback of this measurement technique is that IS algorithms are highly sensitive to noise when the grating reflectivity is high. In this work we demonstrate a new method that enables one to reconstruct highly reflecting FBGs from noisy

measurements. The performance of the new method is significantly better than obtained in previous work and hence it can significantly reduce the measurement duration. LPGs are attractive elements for biochemical sensing since part of the wave propagates through the cladding. We demonstrate, for the first time, a distributed long period grating and discussed its advantages

and its limitations. The extraction of the sensor structure is performed by measuring only its transfer function. We also demonstrate a sensor, based on LPG that can be used for real-time applications.