Increasing the Measurement Dynamic Range of Rayleigh-Based OFDR Interrogator Using an Amplifying Add-On Module

• Published in: IEEE photonics technology letters Vol. 28; no. 22; pp. 2621 - 2624
• Main Authors: Bergman, Arik, Davidi, Roy, Shalev, Avraham Itzhak, Ovadia, Lior, Langer, Tomi, Tur, Moshe
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.11.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: coherent optical frequency-domain reflectometry; fiber devices and optical amplifiers; Fiber-optic sensors; Optical attenuators; Optical fiber sensors; Optical fibers; Optical interferometry; Optical reflection; Optical variables measurement; Rayleigh scattering; Signal to noise ratio
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2016.2608924

An add-on amplifying module is presented, capable of significantly extending the measurement dynamic range of fiber-optic distributed strain/temperature interrogators, which are based on Rayleigh backscattering and optical frequency-domain reflectometry. Since Rayleigh backscattering in single-mode optical fibers is very weak, any optical loss along the sensing fiber, originating from bad connectors and/or micro-and macro-bending, especially under embedding, may jeopardize accurate strain measurements due to a deteriorated signal-to-noise ratio. It is shown that adding an optical amplifier between the interrogator output and the sensing fiber, together with an appropriate return path, has improved the one-way tolerable loss by 5 dB. In principle, better results can be obtained with higher optical gains until either optical reflections and backscattering into the interrogator increase its noise floor or other noise sources saturate the available signal-to-noise ratio.