Opto-sensor based on active resonant cavity and passive resonant cavity cascaded with same

The invention discloses an opto-sensor based on an active resonant cavity and a passive resonant cavity cascaded with the same, which at least comprises the active resonant cavity, the passive resonant cavity and an optical receiver, wherein the active resonant cavity is internally provided with gain and can transmit a uniformly-spaced pectinate spontaneous radiation spectrum or a laser spectrum,and the passive resonant cavity is provided with a uniformly-spaced pectinate filtering spectrum. The spectrum transmitted by the active resonant cavity is input to the passive resonant cavity and then is filtered by the passive resonant cavity, thus the emergent light is received by the optical receiver. The passive resonant cavity is internally provided with a section of sensing unit the optical length of which can be changed with the changes of external environment. The invention takes a multimode active resonant cavity with low cost as an input light source. When the optical length in theactive resonant cavity equals to that in the passive resonant cavity, an optical power detector is simply used to measure the changes of the output light intensity, thus the changes of measured physical quantity can be obtained, with simple detection and low cost; and when the optical length in the active resonant cavity does not equal to that in the passive resonant cavity, a circumscribed spectrograph can be used to expand the measuring range and improve testing accuracy.