D.E. Simikin – Engineer, 

Fryazino Branch of Kotelnikov Institute of Radioengineering and Electronics of RAS

E-mail: denis.simikin@gmail.com

B.G. Gorshkov – Dr.Sc. (Eng.), Leading Research Scientist, 

Prokhorov General Physics Institute of RAS (Moscow)

A.E. Alekseev – Ph.D. (Phys.-Math.), Senior Research Scientist, 

Fryazino Branch of Kotelnikov Institute of Radioengineering and Electronics of RAS

V.T. Potapov – Dr.Sc. (Eng.), Head of Laboratory, 

Fryazino Branch of Kotelnikov Institute of Radioengineering and Electronics of RAS

Problem formulating. One of core reasons which leads to C-OTDR dynamic range decrease (and hence sensitivity decrease) is nonlinear effects arising in fiber when probe pulse power is relatively high. While probe pulse power is under 400 mW, the phase self-modulation (PSM) effect has the greatest influence on the signal character.

Goal. To investigate the development of frequency modulation of the probing pulse due to the PSM in the C-OTDR fiber path and to evaluate its influence on the signal. To propose a method for compensating the effect of PSM. 

Result. A method of compensation of the PSM in a C-OTDR is proposed. Compensation is performed by the means of preliminary frequency chipping of the probing pulse according to a certain law. As a result, at some remote point in the fiber path, the reflectogram contrast is restored to the initial level corresponding to the undistorted optical pulse.

Practical meaning. The described method can be used to restore contrast at some point of the optical fiber. By selecting the parameters of the preliminary modulation, it is possible to achieve that the contrast will have a relatively high value for the entire reflectogram, which will improve the characteristics of sensors based on C-OTDR.

1. Juarez J.C., Maier E.W., Choi K.N., Taylor H.F. Distributed fiber-optic intrusion sensor system. J. Lightwave Technol. 2005. № 23. Р. 2081.
2. Fei P., Han V., Xin-Hong J., Yun-Jiang R., Zi-Nan W., Zheng-Pu P. Ultra-long high-sensitivity Φ-OTDR for high spatial resolution intrusion detection of pipelines. Opt. Express. 2014. № 22. Р. 13804.
3. Daley T.M., et al. Field testing of fiber-optic distributed acoustic sensing (DAS) for subsurface seismic monitoring. Leading Edge. 2013. № 32. Р. 1278.
4. Agrawal G. Nonlinear Fiber Optics 5th edn. Oxford: Academic. 2013.
5. Izumita H., Koyamada Y., Furukawa S., Izumi S. The performance limit of coherent OTDR enhanced with optical fiber amplifiers due to optical nonlinear phenomena. J. Lightwave Technol. 1994. № 12. Р. 1230.
6. Martins H.F., Martin-Lopez S., Corredera P., Salgado P., Frazao O., Gonzalez-Herraez M. Modulation instability-induced fading in phase-sensitive optical timedomain reflectometry. Opt. Lett. 2013. № 38. Р. 872.
7. Alekseev A.E., Vdovenko V.S., Gorshkov B.G., Potapov V.T., Simikin D.E. Contrast enhancement in an optical time-domain reflectometer via self-phase modulation compensation by chirped probe pulses. Laser Physics. 2016. № 26. Р. 035101.
8. Alekseev A.E., Vdovenko V.S., Gorshkov B.G., Potapov V.T., Simikin D.E. A phase-sensitive optical timedomain reflectometer with dual-pulse diverse frequency probe signal. Laser Phys. 2015. № 25. Р. 065101.