Distributed Fiber Optic Sensing is a highly sensitive technology for leak detection that can provide rapid detection and precise locating of small leaks. The evidence from field trials and real-world leaks is becoming increasingly available and more and more pipelines are implementing the technology for leak detection. Under controlled testing, it is trivial to identify the effects of a leak. But what about on deployed systems? In this article, we will discuss how these systems can be tuned in the field – where the sensitivity of the fiber can vary with the installation and local environment, and how field-testing can be performed on an ongoing basis to validate performance. We will also briefly consider how Machine Learning and Artificial Intelligence might impact leak detection using fiber in the future.