a wavelength - division multiplexed system includes an optical communications link with one or more optical amplifiers cascaded from an input end to an output end . each amplifier has a predetermined optical gain throughout a pass band , and passes optical signals in the pass band along the link . transmitting optical communications equipment is coupled to the input end of the link and provides a wdm optical communications signal to the link . the wdm optical signal includes a number of spaced - apart optical signals , including data optical signals and at least one management optical signal , that reside in the pass band of the optical amplifiers . receiving optical communications equipment coupled to the output end of the link receives the wdm optical communications signal , separates the management optical signal from the data optical signals , recovers management information from the separated management optical signal , and uses the recovered management information to carry out management functions . in one case , the management optical signal resides at an edge of the pass band of the optical amplifiers , for example at 1529 . 5 nm or 1561 nm in a system having optical amplifiers specified to operate from 1530 to 1560 nm .