An apparatus for performing a measurement of a downhole property, the apparatus comprising: an optical fiber having a first section that has a first set of fiber Bragg gratings with a first resonant wavelength inscribed therein and a second section that has a second set of fiber Bragg gratings with a second resonant wavelength different from the first resonant wavelength inscribed therein, the second section being in series with the first section, a difference between the second resonant wavelength and the first resonant wavelength being greater than a dynamic wavelength range of each of the fiber Bragg gratings in the first set of fiber Bragg gratings; the apparatus characterised by: an optical interrogator in optical communication with the optical fiber and configured to: emit a frequency domain light signal into the optical fiber, the frequency domain light signal comprising a wavelength swept in a continuous manner for a first time duration and a chirp comprising a modulation of amplitude with a varying of wavelength of the modulation for a second time duration that is less than the first time duration; receive a frequency domain return light signal from the optical fiber due to the emitted frequency domain light signal, the frequency domain return light signal comprising a resonant wavelength shift of each fiber Bragg grating due to the downhole property and a corresponding location of each fiber Bragg grating; and transform the frequency domain return signal into a time domain in order to determine the resonant wavelength shift of each fiber Bragg grating and the corresponding location of each interrogated fiber Bragg grating; and a processor configured to convert the resonant wavelength shift of each interrogated fiber Bragg grating into the downhole property measurement. an optical fiber having a first section that has a first set of fiber Bragg gratings with a first resonant wavelength inscribed therein and a second section that has a second set of fiber Bragg gratings with a second resonant wavelength different from the first resonant wavelength inscribed therein, the second section being in series with the first section, a difference between the second resonant wavelength and the first resonant wavelength being greater than a dynamic wavelength range of each of the fiber Bragg gratings in the first set of fiber Bragg gratings; the apparatus characterised by: an optical interrogator in optical communication with the optical fiber and configured to: emit a frequency domain light signal into the optical fiber, the frequency domain light signal comprising a wavelength swept in a continuous manner for a first time duration and a chirp comprising a modulation of amplitude with a varying of wavelength of the modulation for a second time duration that is less than the first time duration; receive a frequency domain return light signal from the optical fiber due to the emitted frequency domain light signal, the frequency domain return light signal comprising a resonant wavelength shift of each fiber Bragg grating due to the downhole property and a corresponding location of each fiber Bragg grating; and transform the frequency domain return signal into a time domain in order to determine the resonant wavelength shift of each fiber Bragg grating and the corresponding location of each interrogated fiber Bragg grating; and a processor configured to convert the resonant wavelength shift of each interrogated fiber Bragg grating into the downhole property measurement. an optical interrogator in optical communication with the optical fiber and configured to: emit a frequency domain light signal into the optical fiber, the frequency domain light signal comprising a wavelength swept in a continuous manner for a first time duration and a chirp comprising a modulation of amplitude with a varying of wavelength of the modulation for a second time duration that is less than the first time duration; receive a frequency domain return light signal from the optical fiber due to the emitted frequency domain light signal, the frequency domain return light signal comprising a resonant wavelength shift of each fiber Bragg grating due to the downhole property and a corresponding location of each fiber Bragg grating; and transform the frequency domain return signal into a time domain in order to determine the resonant wavelength shift of each fiber Bragg grating and the corresponding location of each interrogated fiber Bragg grating; and a processor configured to convert the resonant wavelength shift of each interrogated fiber Bragg grating into the downhole property measurement.