Frequency domain reflectometry (FDR) has significant application prospects in the diagnostic localization of long-distance submarine cables. The FDR method primarily involves two technical approaches

namely

the broadband impedance spectrum (BIS) and the reflection coefficient spectrum (RCS). This paper systematically reviews and compares the differences between the two techniques for cable defect diagnosis from the perspectives of principle

diagnosis effect and adaptability to submarine cables. Firstly

in terms of principle

BIS relies on comparison with intact cables data to identify defects

while RCS directly reflects the signal's reflection intensity. The core variables and mathematical transformations between the two are different. Additionally

in the diagnosis effect

this paper summarizes and analyzes the current research progress

and simulates cable defects of different positions

ranges and types; meanwhile

this paper compares the diagnostic effects of the two techniques

and it is found that RCS performs better in locating inductive defects while BIS provides more accurate diagnosis for defects in the later segments of the cable. Finally

considering the specific characteristics of submarine cable diagnostics

the paper analyzes the adaptability of both techniques. Due to its stronger noise resistance

BIS method achieves higher positioning accuracy in long-distance transmission and high-noise environments. Through comparative analysis

this paper provides theoretical guidance for selecting the appropriate FDR technique in different application scenarios and offers a novel perspective for the maintenance and submarine cables fault diagnosis.