《12 Allowable received OTDR light power for in-service measurement in lightwave SCM systems》.pdf

286 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 18, NO. 3, MARCH 2000 Allowable Received OTDR Light Power for In-Service Measurement in Lightwave SCM Systems Fumihiko Yamamoto and Tsuneo Horiguchi, Senior Member, IEEE, Member, OSA Abstract— To measure in-service optical transmission lines in of the in-service measurement system proposed in [9]. A syn- optical video distribution systems using subcarrier multiplexing chronous transfer mode (STM) signal with a wavelength in the (SCM) techniques, we clarify how measurement light from an op- 1.3- m region and an SCM signal in the 1.5- m region are tical time domain reflectometer (OTDR) affects the signal trans- mission performance when the light enters an optical network unit multiplexed by wavelength division multiplexing (WDM) tech- (ONU). We describe the additional noises induced when OTDR niques, and these signals are sent to ONU’s via optical transmis- light is injected into the ONU and analyze the relationship between sion lines. In these WDM systems, the splice losses and reflec- received OTDR light power and carrier-to-noise ratio. Moreover, tivities of optical connectors are measured with only one optical we use the analysis to provide a technique for estimating the al- time domain reflectometer (OTDR) which is installed in a cen- lowable received light power in lightwave SCM systems and show the dominant factors determining this allowable power. Finally, by tral office. A measurement light from the OTDR is launched into using the estimation technique, we clarify the required rejection a tested line via an optical switch and an optical coupler. Since ratio for a filter designed to prevent OTDR light from entering the service quality is de