Interrogation of a Sensor Array of Identical Weak FBGs using Dispersive Incoherent OFDR

Abstract

[EN] Incoherent Optical Fourier-Domain Reflectometry incorporating a dispersive delay line is used for the interrogation of an array of three identical fiber Bragg gratings with a Bragg wavelength of 1552.81 nm, reflectivity of 19.3 dB and 10-cm separation. The dispersive delay line induces different delays in the wavelengths reflected by each grating, thus being sensitive to Bragg wavelength shifts. Compared with conventional incoherent Optical Fourier-Domain Reflectometry, dispersive effects decrease the spatial resolution, which in our experiments reached a value of 1.2 cm in fiber at a measurement bandwidth of 10 GHz. As a quasi-distributed temperature sensor, the array shows an accuracy of ±0.5ºC for temperatures up to 100ºC, and an estimated total measurement range of 540ºC. Tradeoffs between bandwidth, scan time, dispersion-dependent spatial resolution, and accuracy, are also analyzed.