An optical fiber interconnection system with a small number of modular components that can be configured for simple construction in many configurations. The system includes connector housings. Optical fibers are installed into the housings on ferrule carriers. The housings are brought together in adapters. Different styles of adapters are available for different applications, such as panel or backplane configurations. However, the same housing and ferrule carriers can be used in any style of adapter. Also, different ferrule carriers are provided for single fiber ferrules and multi-fiber ferrules. Either style of ferrule carrier can be used in a housing and adapter. A ferrule carrier for single fiber ferrules can be modified to provide fine alignment features with the addition of a cap, allowing the same style ferrule carrier to be used in both halves of a mated connector assembly.