Dr. John A. O'Dowd Profile

Dr. John A. O'Dowd

Research Postgraduate Student at FAZ Technology Ltd

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Publications (6)

Proceedings Article | 12 July 2019 Open Access

Demonstration of strain independent temperature measurements using optical PM-FBG sensors for ground testing of satellite panels

Selwan Ibrahim, Raymond McCue, John O'Dowd, Martin Farnan, Devrez Karabacak

Proceedings Volume 11180, 111807B (2019) https://doi.org/10.1117/12.2536182

KEYWORDS: Sensors, Temperature metrology, Calibration, Environmental sensing, Atmospheric sensing, Fiber Bragg gratings, Atmospheric optics, Satellites, Optical testing, Optical sensors

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Proceedings Article | 11 April 2019 Presentation + Paper

Design challenges of a birefringent FBG optical sensing system

Selwan Ibrahim, Raymond McCue, John O'Dowd, Martin Farnan

Proceedings Volume 11028, 1102806 (2019) https://doi.org/10.1117/12.2520604

KEYWORDS: Sensors, Temperature metrology, Calibration, Fiber Bragg gratings, Coating, Polarization, Gold, Atmospheric sensing, Sensor calibration, Optical testing, Fiber Bragg grating interrogators, Fiber optics sensors, Polarization maintaining fibers, Birefringence, Environmental sensing

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Proceedings Article | 25 September 2017 Open Access

Demonstration of a high speed hybrid electrical and optical sensing system for next generation launcher applications

Selwan Ibrahim, John O’Dowd, Arthur Honniball, Vivian Bessler, Martin Farnan, Peter O’Connor, Milos Melicher, Danny Gleeson

Proceedings Volume 10562, 105625E (2017) https://doi.org/10.1117/12.2296153

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The Future Launchers Preparatory Programme (FLPP) supported by the European Space Agency (ESA) has a goal of developing various launch vehicle system concepts and identifying the technologies required for the design of Europe's Next-Generation Launcher (NGL) while maintaining competitiveness on the commercial market. Avionics fiber optic sensing technology was investigated as part of the FLPP programme.

Here we demonstrate and evaluate a high speed hybrid electrical/optical data acquisition system based on commercial off the shelf (COTS) technology capable of acquiring data from traditional electrical sensors and optical Fibre Bragg Grating (FBG) sensors. The proposed system consists of the KAM-500 data acquisition system developed by Curtis-Wright and the I4 tunable laser based fiber optic sensor interrogator developed by FAZ Technology. The key objective was to demonstrate the capability of the hybrid system to acquire data from traditional electrical sensors used in launcher applications e.g. strain, temperature and pressure in combination with optical FBG sensors, as well as data delivery to spacecraft avionics systems. The KAM-500 was configured as the main acquisition unit (MAU) and provided a 1 kHz sampling clock to the I4 interrogator that was configured as the secondary acquisition unit (SAU) to synchronize the data acquisition sample rate between both systems. The SAU acquired data from an array of optical FBG sensors, while the MAU data acquisition system acquired data from the electrical sensors.

Data acquired from the optical sensors was processed by the FAZ I4 interrogation system and then encapsulated into UDP/IP packets and transferred to the KAM-500. The KAM-500 encapsulated the optical sensor data together with the data acquired from electrical sensors and transmitted the data over MIL-STD-1553 and Ethernet data interface. The temperature measurements resulted in the optical and electrical sensors performing on a par with each other, with all sensors recording an accuracy within 0.35% FS over the full temperature range of -70°C to +180°C. The pressure measurements were performed over a 0 to 5 bar absolute pressure range and over different temperatures across a -40°C to +80°C range. The tests concluded that the optical pressure sensors performed on par with the electrical pressure sensor for each temperature set, where both sensor technologies measured a pressure accuracy of 1.2% FS. As for the strain measurements, the results show the optical and electrical sensors can measure to within 1% FS (Full Scale) of measurement range ±1,200 μstrain.

The proposed hybrid system can be potentially used for next generation launcher applications delivering weight reduction, improvement in measurement coverage and reduction in Assembly, Integration and Testing (AIT) over traditional electrical systems.

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Proceedings Article | 25 September 2017 Open Access

Design challenges of a tunable laser interrogator for geo-stationary communication satellites

Selwan Ibrahim, Arthur Honniball, Raymond McCue, Michael Todd, John O’Dowd, David Sheils, Liberis Voudouris, Martin Farnan, Andreas Hurni, Philipp Putzer, Norbert Lemke, Markus Roner

Proceedings Volume 10562, 105620Y (2017) https://doi.org/10.1117/12.2296150

KEYWORDS: Sensors, Fiber Bragg gratings, Fabry–Perot interferometers, Temperature metrology, Tunable lasers, Polarization, Absorption, Fiber optics sensors, Satellites, Radiation effects

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Recently optical sensing solutions based on fiber Bragg grating (FBG) technology have been proposed for temperature monitoring in telecommunication satellite platforms with an operational life time beyond 15 years in geo-stationary orbit. Developing radiation hardened optical interrogators designed to be used with FBG sensors inscribed in radiation tolerant fibers offer the capabilities of multiplexing multiple sensors on the same fiber and reducing the overall weight by removing the copper wiring harnesses associated with electrical sensors.

Here we propose the use of a tunable laser based optical interrogator that uses a semiconductor MG-Y type laser that has no moving parts and sweeps across the C-band wavelength range providing optical power to FBG sensors and optical wavelength references such as athermal Etalons and Gas Cells to guarantee stable operation of the interrogator over its targeted life time in radiation exposed environments. The MG-Y laser was calibrated so it remains in a stable operation mode which ensures that no mode hops occur due to aging of the laser, and/or thermal or radiation effects.

The key optical components including tunable laser, references and FBGs were tested for radiation tolerances by emulating the conditions on a geo-stationary satellite including a Total Ionizing Dose (TID) radiation level of up to 100 krad for interrogator components and 25 Mrad for FBGs.

Different tunable laser control, and signal processing algorithms have been designed and developed to fit within specific available radiation hardened FPGAs to guarantee operation of a single interrogator module providing at least 1 sample per second measurement capability across <20 sensors connected to two separate optical channels.

In order to achieve the required temperature specifications of ±0.5°C across a temperature range of -20°C to +65°C using femtosecond inscribed FBGs (fs-FBG), a polarization switch is used to mitigate for the polarization dependent frequency shift (PDFS) induced from fs-FBG which could be in the order of < 20 pm causing < 2°C error in the measurement. Also special transducers were designed to isolate the strain from the FBGs to reduce any strain influence on the FBG temperature measurements while ensuring high thermal conductivity.

In this paper we demonstrate the operation of an optical FBG interrogator as part of a hybrid sensor bus (HSB) engineering model system developed in the frame of an ESA-ARTES program and is planned to be deployed as a flight demonstrator on-board the German Heinrich Hertz geo-stationary satellite.

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Proceedings Article | 27 April 2017 Presentation + Paper

Optimization of fiber Bragg grating parameters for sensing applications

Selwan Ibrahim, John O'Dowd, Vivian Bessler, Devrez Karabacak, Johannes Singer

Proceedings Volume 10208, 102080P (2017) https://doi.org/10.1117/12.2262103

KEYWORDS: Coating, Reflectivity, Reflection, Fiber Bragg gratings, Fiber optics sensors, Sensing systems, Sensors, Fiber optics, Polarization, Manufacturing, Birefringence, Environmental sensing, Tunable lasers

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Proceedings Article | 12 May 2016 Paper

Interrogation and mitigation of polarization effects for standard and birefringent FBGs

Selwan Ibrahim, Jan Van Roosbroeck, John O'Dowd, Bram Van Hoe, Eric Lindner, Johan Vlekken, Martin Farnan, Devrez Karabacak, Johannes Singer

Proceedings Volume 9852, 98520H (2016) https://doi.org/10.1117/12.2223002

KEYWORDS: Fiber Bragg gratings, Polarization, Sensors, Fiber optics sensors, Birefringence, Temperature metrology, Switches, Tunable lasers, Modulation, Receivers

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