The use of high-power fiber-coupled lasers is increasing in popularity for a variety of applications such as materials processing, cutting, welding, and/or additive manufacturing. Fiber-coupled lasers include fiber lasers, disk lasers, diode lasers, diode-pumped solid state lasers, and lamp-pumped solid state lasers; fiber lasers are the most prevalent fiber-coupled laser source. In these systems, optical power is delivered from the laser to a work piece via an optical fiber, which typically includes a connector at the end. Intermediate fibers between the fiber-coupled laser and the work piece may also be employed, and these intermediate fibers also typically include connectors at both ends. These connectors are typically designed to precisely align the beam emerging from the fiber to maintain pointing of the output beam through the downstream optics and to facilitate multiple connection/disconnection cycles.
A common problem with coupling fibers is that significant optical power may be reflected back into the fiber from the work piece or from optics between the fiber and the work piece. The back-reflected light that is coupled into the fiber may be coupled into the core or cladding of the fiber, but typically most is coupled into the cladding. The back-reflected power coupled into the fiber core is typically transmitted back through the cable toward the laser, but the fiber connector should be configured to manage the power coupled into the fiber cladding. Existing connectors either strip this power or attempt to retain it in the cladding of the fiber. Stripping the back-reflected cladding light is limited by the capability of the connector to dissipate the resultant heat. Furthermore, this method increases the cost and complexity of the connector, typically requires water cooling, introduces failure modes, and limits the ability to monitor the back-reflected light. Monitoring back-reflected light can be useful for process monitoring, control, and optimization. Retaining the back-reflected power in the cladding can result in coupling of light into the cladding that is only weakly guided (i.e., is near the limit of the NA or acceptance angle of the fiber). Bending of the fiber can strip this light, causing localized heating and cable failure. Thus, there exists a need for a fiber connector that neither strips and dumps the back-reflected light in the cladding nor guides it unperturbed into the fiber.