6.3　Installation Requirements for Duct Optical Cables

6.3.1　The duct occupied by duct optical cables may prefer proper locations near both sides of the pipe group.The duct occupied by optical cables in each adjacent pipeline section shall be relatively consistent.When the location of the duct needs to change，the scope of change should not be too large and should avoid transferring from one side of the tube group to the other.

6.3.2　Plastic sub pipes shall be used to protect optical cables per actual situations when laying optical cables in pipes of cement，steel，pottery and ceramics or other similar materials.When optical cables are laid in plastic pipes，large diameter plastic pipes shall be used to contain multiple plastic sub pipes in order to increase the utilization rate of the ducts.

6.3.3　Installation of sub pipes shall be in accordance with the following requirements：

1　Sub pipes should adopt suitable materials such as plastics.

2　The quantity of sub pipes needs to be determined according to the diameter of the ducts and engineering needs，with the total equivalent diameter of the sub pipes not greater than 90% of the pipe diameter.

3　The sub pipes in one duct shall be installed at one time，and there shall be no joints in the pipe section between two man（hand）holes.

4　The sub pipes shall extend from man（hand）holes at appropriate length，usually may be 200mm-400mm.

5　Pipe ends shall adopt waterproof sealing if sub pipes are not used in the current project.

6.3.4　Optical cable closure in man（hand）holes should be installed above the perennial water level and protection trays or other bearing methods should be adopted.

6.3.5　Optical cables in man（hand）holes shall be fixed firmly and should be protected with plastic pipes，shall be marked with clear identification signs or cable labels.

6.3.6　Optical cables laid in special pipelines such as on highways，railways，bridges and construction projects with other large diameter pipelines in the same ditch，shall be properly protected，taking full consideration of various effects on cable lines including road surface subsidence，impacts and shocks，vibrations，structural deformation caused by severe temperature changes etc.