Our single-mode couplers are used to achieve accurate monitoring and splitting of optical signals from 1% to 50%. Thorlabs offers a varied selection of single mode (SM), polarization-maintaining (PM), multimode (MM), and double-clad fiber couplers, as well as 1x8 and 1x16 SM PLC splitters; 1x4, 1x8, and 1x16 PM PLC splitters; wideband multimode circulators; RGB combiners; and WDMs. 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. This article demonstrates the use of several fiber coupling efficiency analyses in OpticStudio. In this model, we use the beam envelopes method to compute a small free-space fiber–fiber.