In order to adapt to the ultra-long distance transmission of optical cable（such as intercontinental sea cable

international long distance land cable trunk and so on） and the fierce cost competition of optical cable

the ultra-long commercial optical fibre length spool（this paper refers to the optical fiber with the delivery fibre length spool of 75 km

100 km） came into application. Compared with the traditional 25 km

50 km commercial fibre length spool

the ultra-long fibre length requires higher production process control and is more difficult to produce. Due to the multiple growth of length

the test of part of the performance of optical fiber cannot be carried out due to the limitation of equipment function. This paper takes 100 km length optical fiber testing as an example to study the testing methods of important characters with challenging testing difficulty

such as attenuation end difference

attenuation uniformity

polarization mode dispersion and other properties of optical fiber

so as to ensure the quality control of ultra-long optical fiber.