In order to overcome the Erbium Doped Fiber Amplifier（EDFA） gain fluctuations when monitoring long-distance multi-span fiber links with EDFA for existing Optical Time Domain Reflectometry（OTDR）

an additional fill light is needed to maintain power stability. In this paper

based on linear frequency modulated optical time domain reflectometry

a long-distance multi-span fiber monitoring technology that does not require supplemental light to pass through EDFA is proposed. This technique utilizes chirped quasi-continuous light as the probe light to avoid fluctuations in the EDFA gain. At the same time

the fractional-domain Fourier filtering is used to remove the spontaneous emission white noise accumulated in the cascaded EDFA

thereby improving the signal-to-noise ratio of the received signal. The experimental results show that the technology can accurately detect the reflection events at the EDFA and the connection points in the long-distance multi-span fiber link.