Tesi etd-09062024-113019
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Tipo di tesi
Dottorato
Autore
ELASKAR PLAZAS, JAVIER DARIO
URN
etd-09062024-113019
Titolo
Photonic Circuit Integration for Interferometric FBG Interrogation
Settore scientifico disciplinare
ING-IND/12
Corso di studi
Istituto di Tecnologie della Comunicazione, dell'Informazione e della Percezione - PHD IN EMERGING DIGITAL TECHNOLOGIES
Commissione
relatore Prof. OTON NIETO, CLAUDIO JOSE
Parole chiave
- Fiber Bragg Grating
- Fiber optical sensing
- Integrated photonics
- High-speed vibration sensing
Data inizio appello
04/12/2024;
Disponibilità
completa
Riassunto analitico
Most current commercial FBG interrogators are based on discrete optical
components. This makes them expensive, bulky, and less reliable. Shifting towards interrogators with integrated photonics would overcome these problems.
In addition, commercial and reported state-of-the-art interrogators have limited detection bandwidths of up to a few tens of kHz, for both integrated and
non-integrated technologies. Detection bandwidths in the order of hundreds of
kHz, would enable the usage of the FBG interrogators for new applications that
require high-speed detection, such as vibrations in rotatory equipment.
This thesis reports the results of three FBG interrogators, the first one is
discrete-component-based, with a large bandwidth, the second is integrated
with a limited bandwidth, and the third is integrated and with a large bandwidth. The three of them used interferometry techniques for wavelength shift
detection, as this technique has a high sensitivity. The responsivity of the interferometer can be selected by design with the free-spectral-range of the device.
However, interferometers have responsivity fading problems when the tracked
wavelength moves away from the quadrature points. To overcome this problem
a modulation-demodulation technique known as multi-tone-mixing was used.
It is an improved variant of the known phase-generated-carrier technique. An
FPGA was used in all interrogators to perform the multi-tone-mixing technique
in real-time and stream the data to the PC.
The first interrogator was based on discrete components with a Sagnac interferometer and a fast Lithium-niobate phase modulator. It has a 280 kHz
bandwidth, dynamic wavelength resolution of 4.7 fm/Hz1/2
, and 4 channel detection. It was packaged in a case for out-of-the-lab experiments.
The second interrogator was integrated into a silicon photonic chip, with
grating couplers, active and passive Mach-Zehnder interferometers, heaters for
phase modulation, arrayed waveguide gratings for multi-channel detection, and
Ge photodiodes. The passive interferometer could detect signals of up to 42 kHz,
but with high noise levels. There were two interferometers for active detection
that used the multi-tone-mixing technique. One has a free-spectral-range of 1.5
nm and a 4.9 fm/Hz1/2 dynamic wavelength resolution. The other one has a
free-spectral-range of 6 nm and 17.8 fm/Hz1/2 dynamic wavelength resolution.
A lower free-spectral-range improves the responsivity but sets the limit for
absolute wavelength tracking within the fringe. Both active interrogators had
700 Hz bandwidth and could detect up to 12 simultaneous FBG channels.
The third interrogator was also integrated on a photonic chip, with grating
couplers, an active Mach-Zehnder interferometer, and a silicon-doped modulator for fast phase modulation. It has a 150 kHz bandwidth and 12.3 fm/Hz1/2
dynamic wavelength resolution
components. This makes them expensive, bulky, and less reliable. Shifting towards interrogators with integrated photonics would overcome these problems.
In addition, commercial and reported state-of-the-art interrogators have limited detection bandwidths of up to a few tens of kHz, for both integrated and
non-integrated technologies. Detection bandwidths in the order of hundreds of
kHz, would enable the usage of the FBG interrogators for new applications that
require high-speed detection, such as vibrations in rotatory equipment.
This thesis reports the results of three FBG interrogators, the first one is
discrete-component-based, with a large bandwidth, the second is integrated
with a limited bandwidth, and the third is integrated and with a large bandwidth. The three of them used interferometry techniques for wavelength shift
detection, as this technique has a high sensitivity. The responsivity of the interferometer can be selected by design with the free-spectral-range of the device.
However, interferometers have responsivity fading problems when the tracked
wavelength moves away from the quadrature points. To overcome this problem
a modulation-demodulation technique known as multi-tone-mixing was used.
It is an improved variant of the known phase-generated-carrier technique. An
FPGA was used in all interrogators to perform the multi-tone-mixing technique
in real-time and stream the data to the PC.
The first interrogator was based on discrete components with a Sagnac interferometer and a fast Lithium-niobate phase modulator. It has a 280 kHz
bandwidth, dynamic wavelength resolution of 4.7 fm/Hz1/2
, and 4 channel detection. It was packaged in a case for out-of-the-lab experiments.
The second interrogator was integrated into a silicon photonic chip, with
grating couplers, active and passive Mach-Zehnder interferometers, heaters for
phase modulation, arrayed waveguide gratings for multi-channel detection, and
Ge photodiodes. The passive interferometer could detect signals of up to 42 kHz,
but with high noise levels. There were two interferometers for active detection
that used the multi-tone-mixing technique. One has a free-spectral-range of 1.5
nm and a 4.9 fm/Hz1/2 dynamic wavelength resolution. The other one has a
free-spectral-range of 6 nm and 17.8 fm/Hz1/2 dynamic wavelength resolution.
A lower free-spectral-range improves the responsivity but sets the limit for
absolute wavelength tracking within the fringe. Both active interrogators had
700 Hz bandwidth and could detect up to 12 simultaneous FBG channels.
The third interrogator was also integrated on a photonic chip, with grating
couplers, an active Mach-Zehnder interferometer, and a silicon-doped modulator for fast phase modulation. It has a 150 kHz bandwidth and 12.3 fm/Hz1/2
dynamic wavelength resolution
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