Multi-core optical fiber polarity insertion loss detector

The invention discloses a multi-core optical fiber polarity insertion return loss detector which comprises an integrating sphere, the integrating sphere is provided with an incident light channel, the incident light channel comprises an incident end, an integrating sphere cavity and a receiving end which are communicated in sequence, and the integrating sphere is further provided with a reflected light channel communicated with the incident light channel. A lens assembly and an imaging device are arranged in the reflected light channel; the semi-transparent and semi-reflective reflecting mirror is fixedly arranged in the incident light channel or a movable reflecting mirror is arranged in the incident light channel, and incident light is reflected by the reflecting mirror or the semi-transparent and semi-reflective reflecting mirror and is converged on the imaging device through the lens assembly for imaging. According to the invention, the return loss test and the insertion loss test of the winding-free mult