An assembly for assembling optical fiber with at least two pairs of MPO contacts. The optical contacts being of the multifiber push-on type. The assembly includes a socket including MPO contacts cooperating with a plug. The plug includes, through axial openings configured to receive the MPO contacts, a first positive-location element positioned in each axial opening of the plug and a second positive-location element positioned on each corresponding MPO contact. A holding element configured to hold the MPO contacts in the plug. The plug shape cooperates with the shape of the socket to ensure coupling thereof. The socket includes locking elements to lock the MPO contacts. Each MPO contact of the plug is locked with the corresponding MPO contact in the socket.