4.4　Submerged Equipment

4.4.1　Submerged equipments may include submarine repeater，BU，gain equalizer，etc..

4.4.2　In addition to meeting the dimensional requirements of the cable-laying equipment of the cable installation ship，the water pressure resistance requirements at the maximal depth of the waters where the project is located，and the high dielectric strength requirements，submerged equipment shall also meet the following requirements:

1　The repeater shall have surge protection for the power feeding system；

2　Important components of the repeater and BU shall be configured in redundancy to meet the requirement for system reliability；

3　The repeater shall have a self-monitoring loop or a C-OTDR monitoring loop；

4　Based on system topology，BUs shall have a fiber splitting or OADM function as appropriate；

5　Based on the topology of the power feeding system，BUs shall have the power feeding line switching function when necessary；

6　BUs that have the power feeding line switching function shall have surge protection；and

7　Gain equalizers may provide equalization of the residual gain tilt or slope based on the submerged plant gain profile characteristics.