4.2　Optical Cable Selection

4.2.1　Optical cables should adopt a loose tube，central tube structure，or may adopt a slotted core structure or other better structures.The fibers in one optical cable should be of the same type as opposed to not mixed types.

4.2.2　Optical cable lines should adopt the optical cables without metal pairs.According to project requirements，in a lightning disturbance or high voltage harm serious region，non-metal component optical cables may be chosen in areas where lightning or high voltage risks are frequent.For areas where termites and mouse harm serious problems，anti-termite and anti-mouse optical cables may be considered.

4.2.3　The sheath structure of optical cables shall be determined according to the laying environment，laying methods and protective measures，and shall comply with following regulations：

1　Directly buried optical cables should adopt either the PE inside guard layer+moisture proof armored layer+PE outer sheath structure，or the moisture proof layer+PE inside guard layer+armored layer+PE outer sheath structure.

2　Optical cables protected by duct or silicon pipe should adopt either the moisture proof layer+PE outer sheath structure or the micro tube+micro cable structure.

3　Aerial optical cables should adopt the moisture proof layer+PE outer sheath structure.

4　Underwater optical cables should adopt the moisture proof layer+PE inside guard layer+steel wire armored layer+PE outer sheath structure.

5　The inner-station and indoor optical cables should adopt the non-flammable materials as the outer sheath.

6　Anti-termite optical cables should adopt the directly buried optical cable structure+antitermite outer sheath.

7　Anti-mouse optical cables should adopt the directly buried optical cable structure plus antimouse outer sheath.

8　Aerial optical cables on power towers should adopt the OPGW or ADSS structure etc.

4.2.4　The mechanical properties of optical cables shall be in accordance with those specified in Table 4.2.4.The additional attenuation of optical fibers should be less than 0.2dB when optical cables are under short-term tension force expected.After release of tension force，the residual strains shall be less than 0.08%，no obvious residual additional attenuation should occur，and the sheath shall not crack as discerned by the human eye.Optical cables shall cause no obvious additional attenuation when it is under long-term tension force expected.

Table 4.2.4　Mechanical properties of optical cables under tensile force and flattening force expected

Note：G refers to the weight of optical cables per kilometer.