Abstract: The modular optical fiber connector includes a ferrule body with a ferrule attached to the front end and a buffer back post extending from the rear end. The ferrule body is permitted to move longitudinally relative to an insert which receives the ferrule and engages the front end of the ferrule body but is restrained against rotation. A coil spring is installed onto the buffer back post of the ferrule body, and engages a connector body that is utilized to internally hold the ferrule body, the insert and the coil spring. A connector nut is a hollow component that has a limiter on the interior wall. The ferrule body and insert in the connector body are inserted into one end of the connector nut and a fastening ring is inserted into the other end of the connector nut, and onto the connector body which is permitted to have longitudinal movement relative to the connector nut within a limited range.