Thorlabs' Wavelength Division Multiplexers (WDMs), also known as wavelength combiners or splitters, are used to combine or separate signals. We offer 2-wavelength fiber WDMs for UV/visible, visible, visible/NIR, or IR wavelengths, 3-wavelength fiber WDMs, 4-wavelength fiber WDMs, and polarization-maintaining fiber WDMs. Infrared wavelength WDMs are an ideal solution for combining pump and signal powers or for combining or separating telecom signals. Visible/NIR wavelength WDMs are commonly used for multi-color displays, sensors, and microscopy.