BU Overview

Primary Functions

See Figure 1, the basic function of BU is to provide branch routes for fiber transmission and power supply for underwater devices.

Figure 1 Network diagram of BUs

BUs have the following primary functions:

• Provide branch routes for fiber transmission by using FP BUs and for wavelength and fiber transmission by using OADM BUs. FP BU is short for fiber pair BU and OADM BU is short for optical add/drop multiplexer BU.
• Supply power for underwater devices.
• Reconfigure system power supply loops by using the power supply switching unit when faults occur in branches.
  NOTE:

  The BU 1650 V100R002 supports power supply switching. Specifically, the power supply status of the BU will be changed when submarine cables are cut in the submarine cable system so that other services are not interrupted in the submarine cable systems. Meanwhile, the faulty submarine cables are grounded by the power supply switching unit for maintenance.

Electricity Connection Status

Figure 2 shows a commonly used electricity connection status. Specifically, ports A and B are connected to the power sources and port C is connected to the sea earth to ensure the power supply for the BU.

Figure 2 BU's electricity connection status

Power Supply Switching

If cables are cut in a submarine cable system, use the power supply switching function of BUs to ensure the power supply for the underwater devices that function properly so that services will not be interrupted. In addition, use this function to ground the faulty cables for maintenance.