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The Scientific World Journal
Volume 2014, Article ID 408613, 8 pages
Research Article

In-Band Asymmetry Compensation for Accurate Time/Phase Transport over Optical Transport Network

Telecommunication Laboratories, Chunghwa Telecom Co., Ltd., No. 99, Dianyan Road, Taoyuan County, Yangmei City 32601, Taiwan

Received 2 January 2014; Accepted 19 March 2014; Published 10 April 2014

Academic Editors: H. R. Karimi, X. Yang, and Z. Yu

Copyright © 2014 Sammy Siu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The demands of precise time/phase synchronization have been increasing recently due to the next generation of telecommunication synchronization. This paper studies the issues that are relevant to distributing accurate time/phase over optical transport network (OTN). Each node and link can introduce asymmetry, which affects the adequate time/phase accuracy over the networks. In order to achieve better accuracy, protocol level full timing support is used (e.g., Telecom-Boundary clock). Due to chromatic dispersion, the use of different wavelengths consequently causes fiber link delay asymmetry. The analytical result indicates that it introduces significant time error (i.e., phase offset) within 0.3397 ns/km in C-band or 0.3943 ns/km in L-band depending on the wavelength spacing. With the proposed scheme in this paper, the fiber link delay asymmetry can be compensated relying on the estimated mean fiber link delay by the Telecom-Boundary clock, while the OTN control plane is responsible for processing the fiber link delay asymmetry to determine the asymmetry compensation in the timing chain.