The frequent failure of the optical fiber composite overhead ground wire (OPGW) can be attributed to the local stress on the optical cable. Herein, the long-distance Brillouin optical time-domain analysis (BOTDA) and Brillouin optical time-domain reflectometry (BOTDR) sensing systems were established to achieve online monitoring of the strain with respect to the OPGW optical cable. Further, strain detection and analysis were conducted in case of a 95.14-km OPGW installed for more than 15 years in the heavily iced disaster area. The measurement distance, spatial resolution, and measurement accuracy of the BOTDA sensing system are greater than those of the BOTDR sensing system based on the comparative measurement results obtained using the same optical cable. In addition, the down conductor and zero-strain reference point can be accurately identified to achieve accurate separation of temperature and strain information. When the distance between two stations exceeds the BOTDA measurement range, the whole cable can be evaluated from two ends of the fiber cable using the BOTDR sensing system. The BOTDR sensing system exhibits single-ended measurement such that this system can continue performing the line measurement after a fiber break before the break point. In this study, the advantages and disadvantages of the BOTDA and BOTDR sensing systems in OPGW optical cable monitoring are analyzed for the first time by performing a multidimensional comparison using the same OPGW optical cable. Furthermore, this study provides a reference with respect to the application of the distributed optical fiber sensing technology in power systems.