Active detection of propagation delay variations in single way time transfer utilizing dual wavelengths in an optical fiber network
Paper i proceeding, 2011

Several communication systems of today rely on the real time accessibility of accurate time and frequency measures and there is an increasing demand for the development of new and redundant methods for the distribution of these measures. The classical two-way method is able to compensate for the inevitable variations in the time and frequency propagation delay. The two-way method is used for time transfer in free space, electrical or optical domain, but has the disadvantage of often using two different paths for transmitting back and forward. The paths may be of equal length and have equal propagation delay, but nevertheless there is often a remaining asymmetry in the propagation paths. The inevitable asymmetry between the paths in the time transfer delay must be detected and compensated for, if an accuracy better than s-level is needed for transmission distance exceeding a few km. Furthermore, if the number of users is high, there will be a complex and large network of two-way time signal transmissions. Therefore, a solution using one-way broadcasting would be more desirable, and would be possible if the variations in transmission time could be estimated from the received data at the far (user) end. The one-way method uses only one path of transmission and is possible to implement in existing Wavelength Division Multiplexing-networks. Proof of concept and results of this one-way time transfer technique based on transmission of a repetitive signal, modulated on two lasers at different wavelengths 8 nm apart and transmitted through an optical fiber, has been presented previously. These data showed a strong correlation between a change in transfer time at one wavelength, and the transfer time difference for the signals at the two wavelengths. In this paper, the setup and the measurement results have been improved and new data is collected which shows improvement in the reliability and quality of this technique. The stability is improved through component analysis and minimizing error sources. The distance is improved from 38km to 160km.

Wavelength division

Transmission distances

Propagation delays

Component analysis

Frequency measures

Real time

Error sources

Two wavelength

Measurement results

Transmission time

Strong correlation

Optical domains

Transfer time

Large networks

Optical fiber networks

Free space

Optical communication

Multiplexing equipment

Communication systems

Time transfer techniques

Proof of concept

Time transfer

Dual wavelength

Time signals

Propagation paths

Optical fibers


Real time systems

Active detection

Fiber optic networks


Sven-Christian Ebenhag

Chalmers, Mikroteknologi och nanovetenskap, Fotonik

Per Olof E Hedekvist

Chalmers, Mikroteknologi och nanovetenskap, Fotonik

R. T. Kenneth Jaldehag

SP Sveriges Tekniska Forskningsinstitut AB

Proceedings of the IEEE International Frequency Control Symposium and Exposition

978-1-61284-111-3 (ISBN)


Elektroteknik och elektronik





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