Abstract: A wavelength division multiplexer (WDM) includes one or more lenses, a WDM filter, and multiple common, multiple reflected and multiple transmit optical fibers optically coupled to the one or more lenses. Light at a first wavelength propagates in either direction between one common optical fiber and one reflected optical fiber via the one or more lenses and the WDM filter, wherein the WDM filter reflects the light at a first wavelength during propagation in either direction between the common optical fiber and the reflected optical fiber. Light at a second wavelength propagates in either direction between the common optical fiber and one transmit optical fiber via the one or more lenses and the WDM filter, wherein the WDM filter passes the light at a second wavelength during propagation in either direction between the common optical fiber and the transmit optical fiber.