**3. Summary**

This chapter has presented a detailed description of the use of the OFS systems and their advantages as compared to the conventional sensing system for use in the railway sector. In a broad sense, the two categories of applications in any railway sensing system are comprised of operational monitoring and traffic management. Normally, dedicated sensing systems are utilized to implement these two types of applications using conventional methods. Postaccidental investigation can be termed as a third category of applications that is related to acquiring data from spatial locations with a minute gap among these locations, which was otherwise impossible in the case of a conventional sensing system. With OFS all three categories of applications are possible with a single sensing system due to its features such as the best reliability and cost-effectiveness to employ all these solutions in a long-range railway system. Moreover, there are additional benefits of OFS in the railway sector, that outweigh this sensing system as compared to conventional sensing systems. There are many sensing systems in OFS; however, in the railway industry, the popular quasidistributed sensing system is FBG and one of the popular distributed sensing systems is DAS. The two sensing systems have been explained.
