Path test signal generator and checker for use in a digital transmission system using a higher order virtual container VC-4Xc in STM-N frames

摘要

A path test signal generator and checker which can achieve a path test by effectively generating a path test signal in a system handling synchronous transport modules STM-Ns with an order higher than that of the basic interface. A test pattern generator generates a continuous PN pattern intermittently, inserts a predetermined logical value in locations of the section overhead and path overhead in a transmission frame while suspending the generation of the path test signal in those locations, and inserts the continuous PN pattern in the entire columns of the payload of the transmission frame. A path overhead insertion circuit rewrites the predetermined logical value inserted in the location of the path overhead into the path overhead. The multiplex section terminating circuit rewrites the predetermined logical value inserted in the location of the MSOH (multiplex section overhead) to the MSOH, and the logical value inserted in the location of the RSOH (regenerator section overhead) to the RSOH. This ensures to achieve the effective path test by generating the synchronous transport module STM-N which accommodates in the entire columns of its payload the continuous path test signal in the form of PN pattern.