Abstract
We develop a high-speed interrogation system with a wavelength-swept laser for sensing multiplexed fiber Bragg gratings (FBGs). High-speed and multipoint sensing is achieved by means of a buffered Fourier domain mode-locked (FDML) laser, a recently proposed high-speed wavelength-swept laser. This laser increases the measurement rate several times by tailoring the laser output with a buffer stage. The developed buffered FDML laser successfully achieves a measurement rate of 202.8 kHz using a general FDML laser driven at a sweep rate of 50.7 kHz. In order to detect reflection signals of FBGs at the high measurement rate, the measurement system introduces digital signal processing using a field programmable gate array (FPGA). However, FBG measurements with wavelength-swept lasers are affected by the propagation time (delay) in the optical fiber connecting from the laser to the FBG sensor, which reduces measurement accuracy. To overcome this limitation, the developed system uses a delay correction method with bidirectional sweep of the buffered FDML laser. The interrogation system with the buffered FDML laser achieves a time resolution of 4.9 μs without being affected by the delay.
Highlights
H IGH-SPEED wavelength-swept lasers are key optical sources in many fields of science and engineering
The buffered Fourier domain mode-locked (FDML) laser was driven at a sweep rate of 50.7 kHz with a bandwidth of ∼39 nm
The interrogation system was equipped with ADC and field programmable gate array (FPGA) with a sampling frequency of 250 MHz and performed real-time calculation of reflection wavelengths of fiber Bragg gratings (FBGs)
Summary
H IGH-SPEED wavelength-swept lasers are key optical sources in many fields of science and engineering. High-speed wavelength-swept lasers have dramatically improved optical coherence tomography (OCT) imaging speeds and detection sensitivities for biological tissues [1]. The Fourier domain mode-locked (FDML) laser has recently been studied as a novel type of high-speed wavelength-swept laser [2]. The FDML provides high sweep rates exceeding several tens of kHz, which enables it to be used as an optical source for the fastest OCT systems. Date of publication May 11, 2021; date of current version July 30, 2021. The associate editor coordinating the review of this article and approving it for publication was Dr Anuj K.
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