We have observed periodic oscillations and optical turbulence in hybrid optical bistable systems having a delay in the feedback, as predicted by Ikeda et al. The period-two output is essentially a square wave of period equal to twice the feedback delay time. Most of the measurements in our hybrid system have been made with a detector-amplifier-modulator response time T of 0.8 ms, much less than the 36 ms computer-generated delay time tR, as required for Ikeda instabilities. Period-two oscillations have also been seen with an optical fiber providing a tR of 6 ps. These hybrid systems have enabled us to study the path to chaos as the input intensity or feedback gain is increased. In all-optical bi-stable devices, such as semiconductor etalons, the feedback time is the cavity round-trio time, which can be made very short (approximately picoseconds), so that many-gigahertz all-optical oscillators can be contemplated. However, such oscillations also require that the medium response time be shorter than the delay time, so realization of high-frequency optical oscillators must await the discovery of high-speed bistable optical devices. In the meantime, use of fast nonresonant nonlinearities in guided-wave configurations could lead to gigahertz optical oscillators.