Encoding optical FBG sensors to enhance the capacity of optical sensing systems

This thesis investigates the application of encoding concepts to the design of optical sensors based on fiber Bragg grating (FBG) devices. Specially, we present the design, charaterization and experimental validation of custom encoded sensing devices that can be designed and manufactured as super-st...

Full description

Autores:
Triana Infante, Cristian Andrés
Tipo de recurso:
Doctoral thesis
Fecha de publicación:
2018
Institución:
Universidad Nacional de Colombia
Repositorio:
Universidad Nacional de Colombia
Idioma:
spa
OAI Identifier:
oai:repositorio.unal.edu.co:unal/68808
Acceso en línea:
https://repositorio.unal.edu.co/handle/unal/68808
http://bdigital.unal.edu.co/70049/
Palabra clave:
6 Tecnología (ciencias aplicadas) / Technology
62 Ingeniería y operaciones afines / Engineering
68 Manufactura para usos específicos / Manufacture for specific uses
Fiber Bragg gratings
FBG
Redes de difracción de Bragg
Codificación
OCDMA
Optical fiber sensors
Sensores ópticos
Sensores de fibra óptica
Multiplexación de sensores ópticos
Optical sensors multiplexing
Rights
openAccess
License
Atribución-NoComercial 4.0 Internacional
Description
Summary:This thesis investigates the application of encoding concepts to the design of optical sensors based on fiber Bragg grating (FBG) devices. Specially, we present the design, charaterization and experimental validation of custom encoded sensing devices that can be designed and manufactured as super-structured FBG (SSFBG) devices. The aim of this thesis is to enhance the capacity and the overall performance of the optical sensing systems based on conventional FBG sensors. To do so, three encoding methodologies of SSFBG sensing devices have been proposed, aiming to endow each sensor with additional information useful to identify each sensor even under overlapping conditions. An encoded FBG-based sensor is a FBG structure whose shape has been tailored after an orthogonal codeword in such a way that their central wavelength can be distinguished unequivocally from other signals in the spectrum. The design of encoded SSFBG sensors is performed by modifying the reflection spectrum of multi-band FBG devices, this is achieved by translating orthogonal codewords into the amplitude and phase terms of the FBG sensors. Amplitude encoding of SSFBG sensors consists in translating the binary optical orthogonal codewords (OOCs), developed for optical-code division multiple-a ess (OCDMA) communications systems, into the reflection pattern of the devices. Amplitude and phase encoding has been proposed in two diferent approaches: in the first one, custom amplitude and phase codewords (ak, fk) were specifically devised to exhibit orthogonal behavior by combining the two codewords. The dual-wavelength tunable interrogation technique was also specifically designed to retrieve the differential measurement of the sensors and effectively decode their information. The second approach uses the discrete prolate spheroidal sequences (DPSS), which are mutually orthogonal sequences developed for communications systems. We demonstrated the use of this structures as orthogonal sensing elements with deffinite phase and amplitude patterns. The manufacturing and experimental validation of the proposed SSFBG devices were carried out to prove the overlap-proof performance of the devices. The central wavelength of the sensors is successfully retrieved in the three methodologies, additionally, the error of the sensing system was characterized in terms of the design parameters.