OSN3500 DeviceEGS2Single Board Principle

The OSN3500 deviceEGS2single board consists of an Ethernet access module, a network processing module, a mapping module, an interface conversion module, a logic control module, a clock module and a power supply module.

OSN3500 DeviceEGS2Single Board Ethernet Access Module:

In the receive direction, the Ethernet access module converts the optical signals from Ethernet devices such as switches or routers into electrical signals. If the signal is accessed from an electrical interface, no optical conversion is required. At the PHY layer, the Ethernet access module performs decoding operations on the electrical signal and detectsthe ETH_LOSalarm signal. The Ethernet access module then performs serial-to-parallel conversion of the electrical signal and sends the converted signal to the network processing module. In the transmit direction, the Ethernet access module performs the parallel-to-serial conversion operation andencodes the signal and performs the electro-optical conversion operation at thePHYlayer.

OSN3500 deviceEGS2single board network processing module:

The network processing module consists of the network processor and the switching network. The network processor first accomplishes MAC functions, including code conversion, Ethernet packet framing,CRCchecksum and Ethernet performance statistics. Once the Ethernet frames that have undergone the stripping operation have entered the core of the network processor, the data stream is categorized according to the service type and configuration requirements. The frames are then encapsulated or decapsulated. The network processing module supports the following encapsulation formats:MPLS,L2 MPLS VPN, and Ethernet/VLAN.

In the receive direction, the Network Processing Moduleperforms mapping and forwarding operations forservices with Tunnel andVCidentifiers based on the service configuration.In the sending direction, the network processing moduleextractsthe TunnelorVCidentifiers according to the level (PorPE)of the device.Then, the service is distributed or forwarded.

The EGS2 single-board network processing module supports the following functions: flow detection and flow classification, unicasting, multicasting and broadcasting of flows, data priority setting, weighted fair queuing and four levels of service hierarchy.

The OSN3500 deviceEGS2single-board mapping module completes the encapsulation and mapping functions.

In the uplink direction, the mapping module first encapsulates Ethernet signals into LAPS orGFPformat and cascades them. Then, the mapping module converts the Ethernet signals intoSDHsignals. In the downlink direction, the mapping module demapsthe SDHsignals and compensates for the virtual cascade delay. Through the alignment operation, the mapping module decapsulates the packets according to the encapsulation format. The decapsulated data is finally sent to the network processing module.

The interface converter moduleconverts the622M LVDSbus of the SDH systemto a parallel bus. The high-speed backplane interface is connected to the system's low-speed interface chip through the interface conversion module.

The OSN3500 deviceEGS2single-board logic control module consists of aCPU, registers, oscillators, Ethernet ports, and anHDLCcontroller. The Logic Control Module is connected to external circuitry via a bus and accomplishes the following functions: management and configuration of other modules on this board, and inter-board communication via the internal Ethernet interface.

The control module also contains the basic logic units. The control module performs the following functions: reads and writes registers, providesan interface to the CPU, detects and selects the clock, performs phase identification and frequency division operations on the clock, checks the presence status of the crossover boards, master boards, and circuit boards, controls the shutdown operations of the optical modules, performs the communication functions, and controls the indicator lights.

The OSN3500 deviceEGS2single-board clock module tracks the system reference clock and generates the working clock required by each chip. The clock frequency can be50MHz,77MHz,125MHzor155MHz.The power supply module is responsible for converting the-48V/-60Vpower supply from the input transmission deviceto the DC voltage required by all modules of the single board.