Novel multimode fiber return loss measuring device and method

The invention discloses a novel multimode fiber return loss measuring device and method, and belongs to the field of measurement. The multi-mode light source meeting the annular flux standard is selected to enable light injected into the multi-mode optical fiber device to meet the'full injection 'condition, the problem of power instability caused by the fact that the mode is not full injection' in the multi-mode optical fiber device is reduced as much as possible, and it is guaranteed that the value of return loss measurement of the multi-mode optical fiber and the device is stable and reliable; a specially processed optical circulator is selected, so that the influence of different modes of multimode signals on a common circulator is inhibited, and the stability of multimode optical fiber return loss measurement is improved; the transmission mode in the multimode optical fiber is detected by adopting the integrating sphere type high-sensitivity photoelectric detector, so that the measurement of the return lo