An optical fiber enclosure system includes a plurality of optical fiber cassettes and a splice module. The enclosure provides improved access and control of optical fiber management. The optical fiber cassette includes adapters, fiber optic connectors, front face, side wall, rear face, fanout devices and ribbon pigtails. The adapters are mounted to the front face of the cassette. The side wall is attached between the front face and the rear face to provide space for optical fiber management. The fanout devices are mounted to the rear face of the cassette and provide fanout of the ribbon pigtails to individual optical fibers that terminate at the fiber optic connectors. The fiber optic connectors are coupled to the adapters at the front face of the cassette. The splice module includes a management plate and a hingedly joined splice door. The splice door can include a removable splice tray for mounting optical fiber splices and for managing associated slack fiber loops around the splices.