What is the Working Principle and Signal Flow of Huawei STM-4 service board SLD4A?

SLD4A consists of the O/E converting module, CDR module, SDH overhead processing module, logic and control module, and power module. 

SLD4A can apply to Huawei MSTP equipment OSN1500B, OSN2500, OSN3500 and OSN7500.

Figure 1 shows the functional block diagram of the SLD4A.

Figure 1 Functional block diagram of the SLD4A

The functional modules of the STM-4 units are described as follows:

O/E Converting Module

• Converts the received optical signals into electrical signals, in the receive direction.
• Converts the electrical signals into SDH optical signals, and then sends the SDH optical signals to fibers for transmission, in the transmit direction.
• The SPI detects the R_LOS alarm and provides the laser shut down function.

CDR Module

This module restores the clock signal.

SDH Overhead Processing Module

this module includes the RST, MST, MSA, and HPT sub-modules. This module provides the inloop and outloop functions.

• RST sub-module
  • In the receive direction, the RST sub-module terminates the regenerator section overhead (RSOH). That is, the RST sub-module detects the frame alignment bytes (A1 and A2), descrambles all the bytes except the first line of the RSOH, restores and checks the regenerator section trace byte (J0), and checks the B1 byte.
  • In the transmit direction, the RST sub-module generates the RSOH. That is, the RST sub-module writes bytes such as A1, A2, and J0, calculates and writes the B1 byte, and scrambles all the bytes except the first line of the RSOH.
• MST sub-module
  • In the receive direction, the MST sub-module terminates the multiplex section overhead (MSOH). That is, the MST sub-module generates the multiplex section-alarm indication signal (MS_AIS) alarm and detects the multiplex section-remote defect indication (MS_RDI) alarm after detecting the K2 byte, and detects the multiplex section-remote error indication (MS_REI) alarm and generates the B2-excessive errors (B2_EXC) alarm after checking the B2 byte.
  • In the transmit direction, the MST sub-module generates the MSOH. That is, the MST sub-module writes bytes such as E2, D4-D12, K1, K2, S1, and M1, and calculates and writes the B2 byte.
• MSA sub-module
  • In the receive direction, the MSA sub-module de-interleaves the administration unit group (AUG), divides an AUG into N AU-4s, detects the administration unit-loss of pointer (AU_LOP) alarm and the administration unit-alarm indication signal (AU_AIS) alarm, and performs pointer justifications.
  • In the transmit direction, the MSA sub-module assembles the AUG and generates the AU-4. N AU-4s are multiplexed into an AUG through byte interleaving.
• HPT sub-module
  • In the receive direction, the HPT sub-module terminates the path overhead (POH). That is, the HPT sub-module detects the higher order path-remote error indication (HP_REI) alarm after checking the B3 byte, generates the higher order path-trace identifier mismatch (HP_TIM) alarm and the higher order path-signal label mismatch (HP_SLM) alarm and detects the higher order path-remote defect indication (HP_RDI) alarm after detecting the J1 and C2 bytes, and generates the higher order path-unequipped (HP_UNEQ) alarm after detecting the C2 byte.
  • In the transmit direction, the HPT sub-module generates the POH. That is, the HPT sub-module writes bytes such as J1 and C2, and calculates and writes the B3 byte.

Logic and Control Module

• Manages and configures the other modules of the board.
• Performs inter-board communication through the internal Ethernet interface.
• Traces the clock signal from the active and standby cross-connect units.
• Controls the laser.
• Passes the orderwire and ECC bytes through an ADM that consists of two paired slots when the GSCC is not in position.
• Selects the clock signal and frame header signal from the active and standby cross-connect units.
• Controls the indicators on the board.

Power Module

It converts the –48 V/–60 V power supply into the DC voltages that the modules of the board require.