Abstract: Echelle gratings with a shared free propagation region. In some embodiments, a system includes: a first echelle grating; and a second echelle grating. The first echelle grating may include: a first input waveguide having an end on a first Rowland circle; a first grating on the first Rowland circle; and a first output waveguide having an end on the first Rowland circle. The second echelle grating may include: a second input waveguide having an end on a second Rowland circle; a second grating on the second Rowland circle; and a second output waveguide having an end on the second Rowland circle. The second input waveguide may be separate from the first input waveguide, the second output waveguide may be separate from the first output waveguide, and the first Rowland circle may overlap the second Rowland circle.

Abstract: A system including wavelength multiplexers. In some embodiments, the system includes: a first multiplexing element, having a first plurality of input waveguides, each configured to receive light at a respective wavelength of a first plurality of wavelengths; and a second multiplexing element, having a second plurality of input waveguides, each configured to receive light at a respective wavelength of a second plurality of wavelengths. A wavelength of the second plurality of wavelengths may fall between a first wavelength of the first plurality of wavelengths and a second wavelength of the first plurality of wavelengths.