GB/T 15837 specifies the physical/electrical (optical) characteristics requirements, carrying SSM information requirements, and network performance requirements for various synchronous interfaces in digital synchronous networks. The network performance requirements include network limit requirements for synchronous interface output and network tolerance requirements for synchronous interface input. This standard is the most comprehensive standard for the technical specifications of digital synchronous network interfaces in China. Due to the fact that digital synchronous network interfaces, whether they are PRC (and LPR) device output interfaces, SSU output interfaces, SEC output interfaces, etc., only include 2048kbit/s, 2048kHz, and STM-N interface types, the technical requirements given in GB/T 15837 are specified for these three interface types. 1. The physical/electrical (optical) characteristics requirements of various synchronization interfaces in digital synchronous networks include impedance requirements, waveform requirements, etc. Mainly refers to the characteristics of its electrical interface, which are based on and follow the provisions of ITU-T Recommendation G.703, and are specifically specified in China's national standard GB/T 7611. The relevant provisions of GB/T 15837 are consistent with those of GB/T 7611. For more information on the relevant provisions of GB/T 7611, please enter. For optical interfaces such as STM-1, STM-4, STM-16, and STM-64, the eye diagram at the transmitting end should meet the requirements of 8.3.3.4 in the national standard GB/T 15941 "Synchronous Digital Hierarchy (SDH) Optical Cable Line System Access Requirements". For detailed information on the content of GB/T15941, please enter. 2. The requirements for carrying SSM information by the digital synchronous network interface mainly include the quality level information of the clock. The SSM quality level (QL) is represented by 4 bits, and its definition is shown in Table 1-2-1. Among the three types of interfaces, 2048kHz cannot carry SSM information
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