Ultrafast all-optical switch has been demonstrated by inserting Fe-doped multiple quantum wells (MQWs) in asymmetric Fabry-Perot microcavities. Heavy Fe doping during the InGaAs∕InP MQW epitaxial growth is a well-controlled technique to reach subpicosecond optical time constants. An asymmetric Fabry-Perot microcavity using gold metal as a back mirror and air/InP interface as a front mirror is realized. Pump-probe experiments using a conventional scheme on such switching devices are investigated. The device reveals an ultrafast response time, as low as 290fs, for an iron concentration of 2×1019cm−3, a contrast ratio of 8dB, a threshold switching fluence of 3.5μJ∕cm−2, and a 37-nm 3-dB bandwidth in the 1.55-μm telecommunication spectral range.