Optical loss increase of SP-optical fiber cable at low temperature was investigated theoretically and experimentally. Estimation formula was presented for the relation between excess fiber length and optical loss increase. It was clarified that excess fiber ratio normalized by pipe radius of less than 0.005 was required to suppress optical loss increase at 40 to be less than 0.1 dB for 1 km in cable length.

This paper describes designing on required signal to crosstalk power ratio of symmetrical cable for bipolar pulse transmission. Error rate in bipolar pulse transmission is discussed taking into account average signal to far-end crosstalk power ratio, average signal to near-end crosstalk power ratio and their standard deviation. Experiments were conducted with regard to the relation among average signal to crosstalk power ratio, its standard deviation and error rate. Calculated and measured results show good agreements. From these results, designing on required signal to crosstalk power ratio and its standard deviation in dB for required error rate is clarified.