The Single Mode Standard Coupler from Opneti is a Fiber Optic Coupler with Excess Loss 0. 2 to 22 dB, Bandwidth ±15 nm, Wavelength 1310 nm, 1550 nm, Polarization Dependent Loss <0. Several center wavelength options are available (see Table 1. Narrowband couplers have a ±15 nm bandwidth, dual-window couplers have a ±40 nm bandwidth around. Canstar 1x2 singlemode Couplers are designed for use in test equipment and optical networks. It features good uniformity, low excess loss and very low polarization sensitivity. Single. Exact Loss Max.