Abstract This paper delves into the applications and prospects of Narrow Linewidth Lasers in optical communication. Their distinct spectral features are vital for modern optical setups. It analyzes applications in coherent optical comms, WDM, fiber - sensing - based comms, and QKD. Challenges like cost, compatibility, and environmental adaptability are discussed, along with future tr... https://www.cq-smart.com/narrow-linewidth-laser