ORTE single mode including: Low PDL tap couplers, narrowband couplers, single window broadband couplers, two windows broadband couplers, single mode broadband tree couplers, and so on. They are suitable for use in instrumentation, DWDM systems, trunk/loop branching, and CATV distribution. Their low optical loss and high directivity make them an excellent choice for systems with power constraints. The couplers designed to meet demanding specifications for telecommunications applications.