Thorlabs offers both retroreflectors and partial retroreflectors. Our fiber optic reflective-coated patch cables are designed to reflect light input through the connector backward through the fiber. They can be used to create a fiber interferometer or to build a low-power fiber laser. Fiber Partial Reflectors are designed to reflect a fraction of the input light backwards towards the input end while transmitting the remainder to the fiber output. Beamsplitter-coated patch cables use a beamsplitter coating on one connector end facet and are ideal for fiber to free space applications, while our in-line partial reflectors use an internal reflective coating that enables them to be used in all-fiber applications.