A four channel lightwave transmission subsystem using wavelength division multiplexing.

A four channel, multi-mode transmission subsystem employing wavelength division multiplexing was assembled and optically evaluated. Diffraction grating devices with identical fibers for inputs and outputs were used for both multiplexing and demultiplexing. The 1dB full width of the passbands was ~ 4nm, thus, there was a requirement for wavelength selection and temperature tuning of the corresponding laser sources. A temperature excursion of 7C from the optimum resulted in 1dB of additional attenuation. Insertion losses for the Mux/Demux pair were 3.7, 3.6, 4.7, and 7.3dB at 812, 830, 867, and 885nm, respectively. The higher losses at 867 and 885nm were due to chromatic aberration. The channel spacing of 18nm is smaller than could be achieved with state of the art filter devices.