Optical Wavelength Conversion Unit. STM-64 Transmitting Optical Wavelength Conversion Unit with FEC Function, страница 7

RWC board adopts O/E/O mode. Its output signals comply with ITU-T G.957 recommendation. Its function block diagram is shown in Figure 3-5.

Figure 3-5 Principle block diagram of RWC board

In the diagram, O/E conversion part converts the optical signals from the optical demultiplexing board into electrical signals through the photoelectric detector, recovers the signal codes and extracts the clock after amplitude-limited amplification. The jitter suppression part, after processing the recovered digital signals, filters out the jitters generated during regeneration process by the phase-locked clock, then multiplexes into serial digital signals, thus enabling the system to possess very good jitter suppression ability. B1 detection circuit performs B1 error code counting of RWC board input signals, thus monitoring the error code performance of OptiX BWS 320G system. The function of E/O part is to convert the digital signals into optical signals. It is composed of driver, modulator and laser. The driver accomplishes amplification and shaping of the digital signals, the laser transmits the laser carrier, while the modulator modulates the digital signals to the optical carrier.

The principle of RWC board is basically the same as that of TWC board, only with the difference that the optical transmitting module used by the two boards is different: the optical transmitting module used by TWC complies with ITU-T G.692 recommendation while the optical transmitting module used by RWC board complies with ITU-T G. 957 recommendation.

2. Functions

n  Line code pattern: in compliance with ITU-T G.707 recommendation, being scrambling NRZ code.

n  Min. extinction ratio: >8.2dB.

n  Eye pattern：in compliance with ITU-T G.957 recommendation

n  The min. receiving sensitivity of the optical receiver : -25 dBm ( APD receiving module) or -18 dBm ( PIN receiving module) ( under the condition of bit error rate BER=1.0E-12)

n  Overload optical power of the optical receiver: -9dBm (APD receiving module) or 0dBm (PIN receiving module)

n  RWC board provides the monitoring on regeneration section B1 byte, ( B1 error code report, B1 cross threshold, B1 deterioration), facilitating the locating of faults on the line.

n  RWC board can provide the following monitoring functions: laser bias current monitoring, laser cooling current monitoring, laser transmitting optical power monitoring, and incident optical power monitoring.

n  RWC board provides the automatic laser shutdown (ALS) function.

3. Application

n  RWC optical input port receives STM -16 signals from the optical demultiplexing board in compliance with ITU-T G.692 recommendation and its optical output port transmits STM-16 signals in compliance with ITU-T G.957 recommendation to the SDH equipment.

n  RWC can be inserted in 1~13 board position of OptiX BWS 320G subrack.

n  The optical connector on RWC board handle bar is of SC type.

4. Common alarm performance

RWC board is composed of the optical transmitting module and optical receiving module, so its alarms mainly reflect the working status of these two modules. Alarms of RWC board are shown in Table 3-4.

Table 3-4 List of RWC board alarms