The Fiber Loop Carrier for Curb (FLC-C) system architecture is using a Host Digital Terminal (HDT) unlike the FLC-A/B architectures that use the Central Office Terminal (COT) together with the Remote Terminal (RT). The HDT has 16 STM-4c interfaces, making able to connect 16 ONUs or use 1:1 protection and connect eight ONUs. For all these connections the high-speed fiber optical links are used. In this architecture ONUs can be connected in ring, star, double star (Figure 1.) or a mixture of those.
In scenario when broadband services should be applied in the network, the conventional subscriber copper pairs can be used applying Very High-Speed Digital Subscribe Line(VDSL) technology. Central office systems like PSTN and ATM switches are connected to HDT using DS1E and STM-1 interfaces, respectively. Connection between HDT and ONUs is made using STM-4c signals with Asynchronous Transfer Mode (ATM) cells.

Figure 1. FTTC access network system configuration.

The ONU cabinet:

• installed outdoors in near location from apartment complexes;
• equipped with power supply for normal AC commercial power;
• equipped with backup batteries for failure of AC power;
• equipped with heat exchanger that controls temperature inside the cabinet.

Two biggest issues for equipment allocated outdoors are humidity and temperature. These problems apply for the ONU equipment as well. Thermal management issue must be solved in the early stages of the development of the project. Equipment should be designed so that the internal heat and the external heat (usually heat from the sun) will be effectively removed.