A unit includes: a module configured to convert an electric signal into an optical signal and transmit the optical signal, or receive an optical signal and convert the received optical signal into an electric signal； and a connector connected to the module and configured to hold an end portion of an optical fiber transmitting the optical signal. The connector includes a ferrule configured to hold the optical fiber, and a flange portion provided at one end of the ferrule. The module includes an element configured to convert the electric signal into an optical signal or the optical signal into an electric signal, and a metal case configured to store the element. A connector side screw portion is provided on the ferrule, and a module side screw portion screwed with the connector side screw portion is provided in a sleeve of the metal case into which the ferrule is inserted.
