The upper and lower optical interfaces of the CFS must be matched in pairs. Each upper optical interface is connected to a BBU and each lower optical interface is connected to a PB. For a pair of interfaces, one is used for input while the other is used for output, and the two interfaces cannot be used interchangeably. In other words, the matching relationship is 1-7/2-8/3-9/4-10/5-11/6-12, and the two interfaces in a pair are connected to the BBU and PB respectively.
For the CFS, the number of input optical fibers must be the same as that of the output optical fibers.
Limited to the remote control distance of the GSM, the distance from the MAU to the last level PB cannot be larger than 5 km.
The distance from the BBU to the last level PB cannot be larger than 10 km.