Huawei OptiX 155/622H(Metro1000) is interconnected to the CDMA equipment of the B supplier through the E1 cable. A large amount of bit errors occur on the CDMA equipment. There is no bit error or performance event present on the optical line of the OptiX 155/622H(Metro1000). No bit errors are detected in 24 hours in the central office.
A large amount of bit errors are detected on the CDMA equipment of the B supplier. The communication of the station sometimes fails due to too many bit errors.
1. Ground the DDF. The bit errors decrease and sometimes disappear. Therefore, the equipment grounding is suspected as the cause of the problem. When the CDMA equipment, DDF, and OptiX 155/622H(Metro1000) is grounded together, however, the CDMA equipment fails the communication and bit errors grow to the maximum.
2. Then, the OptiX 155/622H(Metro1000) is suspected faulty. Replace the optical interface board, tributary board, and even the integrated equipment. The bit errors persist.
3. During replacing the integrated equipment, bit errors become few when the chassis of the OptiX 155/622H(Metro1000) is insulated from the cabinet. The grounding is again suspected. Test the grounding resistance. It is two ohms, which is normal. Test the voltage of all the equipment. The voltage differential is also normal.
4. Use an oscilloscope to test the waveform of the E1 signal at the DDF. The waveform of the signal sent from the SDH equipment to the CDMA equipment is good, and the waveform of the signal sent from the CDMA equipment to the SDH equipment is also good. When the oscilloscope is used to test the waveform at the two ends, the waveform of the signal sent from the CDMA equipment to the SDH equipment is good whereas severe distortion occurs to the waveform of the signal sent from the SDH equipment to the CDMA equipment. Replace the DDF. The bit errors persist.
5. Test the waveform of the CDMA signal on other stations. There is no waveform distortion.
6. Replace the 120-ohm/75-ohm converter on the CDMA equipment. The fault is cleared.