We describe a single-mode fiber-optic switch for use in an AM CATV describe a single-mode fiber-optic switch for use in an AM CATV transmission system. This paper will discuss several applications, including the incorporation of a standby laser to fulfill the need for redundancy. This switch allows for system testing, such as OTDR traces and optical power testing, without breaking splices or losing fiber transmission. In all of its applications it introduces no measurable system degradation. A detailed description with diagrams as well as performance characteristics are given. ·transmission system. This paper will discuss several applications, including the incorporation of a standby laser to fulfill the need for redundancy. This switch allows for system testing, such as OTDR traces and optical power testing, without breaking splices or losing fiber transmission. In all of its applications it introduces no measurable system degradation. A detailed description with diagrams as well as performance characteristics are given.