Proceedings of SPIE - the International Society for Optical Engineering
Spatial Domain Multiplexing (SDM) is a novel optical fiber multiplexing technique where multiple channels of the same wavelength are launched at specific angles inside a standard step index multimode carrier fiber. These channels are confined to specific locations inside the fiber and they do not interfere with each other while traversing the length of the fiber. Spatial filtering techniques are employed at the output end to separate, route and process the individual channels. These skew ray channels inside the SDM system follow a helical trajectory along the fiber. The screen projection of the skew rays resembles a circular polygon. A ray theory based mathematical model of the SDM system is presented and simulated as well as experimental data is compared to the model predictions. This ray theory model utilizes launch point, input incidence angle, and point of incidence on fiber to explain the behavior of the individual channels. Thus the vector approach to propagation allows us to predict the effects of pulse spreading in the SDM system. The results showed that the skew ray trajectory is sensitive to input incidence angle. Similarly changing the launch point, while maintaining the angle of incidence constant with the z axis, can drastically affect the skew ray trajectory.
Murshid, S. H., Zahir, E., & Chakravarty, A. (2010). SDM propagation model for multiple channels using ray theory. Paper presented at the Proceedings of SPIE - the International Society for Optical Engineering, 7682 doi:10.1117/12.850577