Problems with jitter measurement in PDH/SDH-based digital telecommunication systems

This paper arises from criticisms, originated by telecommunication manufacturers, concerning some problems experienced during production tests of digital telecommunication apparatus. The faultfinding mainly concerns test equipment as well as recommendations currently in force for generating and measuring timing jitter in telecommunication systems based on both (PDH) plesiochronous and (SDH) synchronous digital hierarchies. In this paper, the aforementioned problems are first discussed in detail and then confirmed by some experiments carried out at the laboratories of a major Italian manufacturer. To meet the request of production managers, a novel, more accurate method for measuring jitter in PDH/SDH-based systems is proposed. Thanks to a suitable digital signal-processing solution, the method no longer needs timing recovery circuitry and shows itself insensitive to nonrectangular pulse shapes. The results obtained from the application of the method to the same data signals analyzed at the aforementioned manufacturer finally assess its reliability and capability.