Multi-mode combiners are passive devices that allow coupling light from a few multimode laser sources into one fiber and are commonly used in high power optical lasers and amplifiers. Fibrain combiners are characterized by high pump efficiency (min. 90%) and low insertion loss (max. 0.5 dB).

Fibrain combiners are available in 1x5, 1x6, and 1x7 versions with multimode, single-mode, or polarization-maintaining output. Highly fused versions without air holes are also possible.