Optical signal transmission system, a method for transmitting a plurality of optical signals, and a method for making a photonic device

A method for transmitting a plurality of optical signals, the method comprising:

• using a spatial mode add drop multiplexer coupled to a multimode optical fiber link that supports a plurality of spatial modes to either couple into the multimode optical fiber link an optical signal of the plurality of optical signals into a spatial mode of the plurality of spatial mode groups or coupling out of the multimode optical fiber link the optical signal of the spatial mode, wherein the spatial mode add drop multiplexer comprises a multimode optical fiber input optically coupled to the multimode optical fiber link, a multimode optical fiber output optically coupled to the multimode optical fiber link, and a glass photonic chip comprising a waveguide network comprising a multimode waveguide input at which the multimode optical fiber input in optically coupled and a multimode waveguide output at which the multimode fiber output is optically coupled, wherein the spatial mode add drop multiplexer is configured for at least one of coupling into the multimode optical fiber link an optical signal of the plurality of optical signals into a spatial mode of the plurality of spatial modes and selectively coupling out of the multimode optical fiber link the optical signal of the spatial mode.