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.

MUX/DEMUX Module

• In the receive direction, the DEMUX part demultiplexes the high rate electrical signals into multiple parallel electrical signals, and recovers the clock signal at the same time.
• In the transmit direction, the MUX part multiplexes the parallel electrical signals received from the SDH overhead processing module into high rate electrical signals.

SDH Overhead Processing Module

• RST sub-module
  • In the receive direction, the RST sub-module terminates the RSOH. Det är, 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 J0 byte, and checks the B1 byte.
  • In the transmit direction, the RST sub-module generates the RSOH. Det är, 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). Det är, the MST sub-module detects K2 bytes, and upon errors, generates MS_AIS or MS_RDI alarms; it also verifies B2 bytes, and upon errors, generates B2_SD or B2_EXC alarms and sends MS_REI signals to its opposite end.
  • In the transmit direction, the MST sub-module generates the MSOH. Det är, 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 AUG, divides an AUG into N AU-4s, detects the AU_LOP alarm and the 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). Det är, the HPT sub-module verifies B3 bytes, and upon errors, sends HP_REI signals to its opposite end; it also detects J1 and C2 bytes, and upon errors, generates HP_TIM, HP_SLM, or HP_UNEQ (if VC-4 paths are unloaded) alarms.
  • In the transmit direction, the HPT sub-module generates the POH. Det är, 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.

Strömmodul