the engaging teeth 4a are pressed against the tapered surfaces 34 t 34 of the engageable teeth 11b of the holder bodies 11 the lower ends of the engaging teeth 4a spread outwardly along the tapered surfaces 34 t 34 and then resiliently snap inwardly underneath the engageable teeth 11b thereby securely holding the engageable teeth 11b and hence the holder bodies 11 the optical module is assembled as follows first as shown in fig2 the half bodies 3 are brought into sandwiching relation to the receptacle 1 causing the engage ridges 11a of the holder bodies 11 to engage in the engageable slots 8a of the outer sleeve 8 thereafter the housing 4 is placed downwardly over the ferrule bushing 9 and the plug engaging tongues 12a until the engaging teeth 4a snap resiliently over the engageable teeth 11b now the receptacle 1 the holder 2 composed of the combined half bodies 3 and the housing 4 are put together into an integral assembly the parts of the optical module can easily be assembled simply by putting them together without tightening screws applying an adhesive or involving any other additional fastening process as described above the optical module according to the present invention has a holder composed of half bodies separable from each other and combinable with each other the half bodies having respective engaging ridges engageable in respective slots in.