There is a growing need to measure respiratory rate (RR) in a variety of applications, including in clinical and occupational settings, as well as during physical exercises. Fiber optic sensors (FOSs) is an attractive solution for wearable RR monitoring because of their small size, multiplexing capability, chemical inertness, and immunity to electromagnetic fields. Here, we review recent advances in FOSs for breath monitoring. We presented the sensing mechanisms of state-of-the-art sensors and analyze their advantages and disadvantages. We classified recently reported FOSs based on sensing principles and then critically analyze the strengths and weaknesses of representative recent works. Finally, we summarized the challenges and future prospects of breath FOSs, with the aim of applying them to real applications.