The most obvious application of single-frequency lenses is in fiber optic communication transceivers (a single-frequency laser, or a series of such lasers in Wa

The most obvious application of single-frequency lenses is in fiber optic communication transceivers (a single-frequency laser, or a series of such lasers in Wavelength Division Multiplexing). From my understanding these are a big source of component cost and failure rates. See e.g. http://www.panduit.com/heiler/InstallInstructions/PN541.pdf http://www.panduit.com/heiler/InstallInstructions/PN541.pdf