Optical time domain reflectometry on live bidirectionally used fibres deploying DWDM transmissions

Fibre based transmission of ultra-precise time and ultra-stable optical frequency is quickly becoming common reality, not only in the fibres used for research but also in other operational fibre networks. At the moment, a fibre represents the best precision of such transmissions. In order to achieve highest possible transmission stability up to 10-18for 1000 s averaging, the bidirectional transmission within single fibre is required including exclusive optical amplification. We present here the use and results of Optical Time Domain Reflectometry (OTDR) technique for detection of disturbances as connector losses, reflections, bending etc. on live fibres with present Amplified Spontaneous Emission (ASE) from bidirectional Erbium Doped Fibre Amplifiers (EDFAs).