This part of IEC 60794 specifies the requirements for optical fibre cables and cable elements which are intended to be used externally in communications networks. Other types of applications requiring similar types of cables can be considered. Requirements for cables to be used in ducts, for directly buried applications, aerial cables and cables for lake and river crossings are included in this standard. Also included are cables for specialized use in sewers and in water and gas pipes. For aerial application, this standard does not cover all functional aspects of cables installed in the vicinity of overhead power lines. For such applications, additional requirements and test methods may be necessary. Moreover, this standard excludes optical ground wires and cables attached to the phase or earth conductors of overhead power lines. For cables for lake and river crossings, this standard does not cover methods of cable repair, nor repair capability, nor does it cover cables for use with underwater line amplifiers. NOTE – IEC TR 62839-11 gives rules to built an environmental declaration if needed.