In an embodiment, a delay line interferometer (DLI) multiplexer (MUX) includes a first stage and a second stage. The first stage includes a first DLI and a second DLI. The first DLI includes a first left input, a first right input, and a first output and has a free spectral range (FSR) that is about four times a nominal channel spacing. The second DLI includes a second left input, a second right input, and a second output and has an FSR that is about four times the nominal channel spacing. The second stage is coupled to the first stage and includes a third DLI. The third DLI includes a third left input optically coupled to the first output, a third right input optically coupled to the second output, and a third output. An FSR of the third DLI is about two times the nominal channel spacing.