a socket housing including a mating portion extending forward and a mounting portion extending rearward; the mating portion having an opening located on the front of the mating portion and a receiving cavity extending rearward from the opening; the mating portion further having a top wall, a bottom wall, a rear wall and two sidewalls, which together define the receiving cavity and the opening; the mating portion including a row of upper support bars located in the receiving cavity and adjacent to the top wall, and a row of lower support bars located in the receiving cavity and adjacent to the bottom wall; the upper and lower support bars being symmetrical to each other, horizontally extending forward from the rear wall and being not exposed outside the mating portion; the mounting portion forming a mounting space; the socket housing further including two rows of upper terminal-receiving grooves and two rows of lower terminal-receiving grooves; one row of upper terminal-receiving grooves being located on an inner side of the top wall and extending to the mounting space, and some of the other row of upper terminal-receiving grooves being formed between these upper support bars and extending to the mounting space; one row of lower terminal-receiving grooves being located on an inner side of the bottom wall and extending to the mounting space, and some of the other row of lower terminal-receiving grooves being formed between these lower support bars and extending to the mounting space;

a shielding case being mounted on the socket housing and having an upper port and a lower port; the upper port being aligned with the two rows of upper terminal-receiving grooves, and the lower port being aligned with the two rows of lower terminal-receiving grooves;

multiple terminal assemblies being mounted in the socket housing and including multiple signal terminal assemblies and multiple ground terminal assemblies, which are arranged side by side in the order of ground-signal-signal; each terminal assembly including a support frame, a pair of upper conductive contact parts extending forward from the front of the support frame, a pair of lower conductive contact parts extending forward from the front of the support frame, and four conductive tails extending downward from the bottom of the support frame; wherein the pair of upper conductive contact parts are inserted into the corresponding upper terminal-receiving grooves and are exposed in the receiving cavity, and the pair of lower conductive contact parts are inserted into the corresponding lower terminal-receiving grooves and are exposed in the receiving cavity; and

a light guide tube assembly being mounted on the socket housing.