Optical steganography for data-hiding is experimentally demonstrated using group velocity dispersion in an optical network. A stealth channel is temporally and spectrally hidden underneath a public channel. Our technique applies to several different types of optical systems including optical code division and wavelength division multiplexing. The hidden signal is retrieved at the receiver through dispersion management. The effect of the stealth channel on the performance of the public channel is shown to be small; this is demonstrated through eye diagrams and bit-error rate measurements. To miniaturize the proposed scheme, compact chirped fiber Bragg gratings are used, reducing the length of the fiber providing group velocity dispersion is by a factor of 2000 compared to previous demonstrations.