Distributed electrical cross device, and system and method thereof for implementing sub-network connection (SNC) cascade protection

In a system for a distributed electrical cross apparatus implementing a sub-network connection (SNC) cascade protection, the system comprising a distributed electrical cross apparatus wherein the distributed electrical cross apparatus comprises a backboard and four single-boards, the four single-boards are inserted in fixed slots on the backboard, the four single-boards are set as two pairs of single-boards whose functions and service access conditions are completely symmetrical, and the two pairs of single-boards further connect with line-side service sub-networks in four directions respectively while supporting add/drop paths of client-side services, each single-board comprises an electrical cross unit, a line-side service access unit, a client-side service access unit and a backboard access unit, wherein the electrical cross unit achieves cross connections of line-side services, client-side services and backboard-side services, the backboard access unit comprises three backboard electrical signal interaction modules and three backboard electrical signal multiplexing and de-multiplexing modules corresponding to the three backboard electrical signal interaction modules, each backboard electrical signal interaction module connects with the electrical cross unit of the single-board which the corresponding backboard access unit located through the corresponding backboard electrical signal multiplexing and de-multiplexing module, the three backboard electrical signal interaction modules in each single-board are configured to connect the single-board where the three backboard electrical signal interaction modules locates with the backboard electrical signal interaction modules of the other three single-boards, the backboard electrical signal multiplexing and de-multiplexing module is configured to decompose a backboard electrical signal into multi-path sub-wavelength electrical signals, and converge the multi-path sub-wavelength electrical signals into one path backboard electrical signal, a method for a distributed electrical cross apparatus implementing a sub-network connection (SNC) cascade protection, the method comprising:

• setting the four single-boards of the distributed electrical cross apparatus as two pairs of single-boards in which functions and service access conditions are completely symmetrical in the distributed electrical cross apparatus, and the two pairs of single-boards further connecting with line-side service sub-networks in four directions respectively while supporting add/drop paths of client-side services;
• each single-board monitoring work conditions of other single-board devices connected with this single-board and work conditions of access services of this single-board;
• when the single-board device and/or the access service has a fault, the single-board reporting a fault alarm signal to a protection switching controller;
• the protection switching controller notifying a related board to change a service electrical cross connection configuration of an electrical cross unit according to the fault alarm signal reported by the single-board;
• the related single-board executing changing the service electrical cross connection configuration of the electrical cross unit.