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Interpreting a Strip Chart
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Look at the Strip Chart to see the proportion of bit versus burst errors. This proportion gives an idea of which type of errors may dominate, and which to fix first. |
Before studying a Strip Chart in detail, you must first be assured that you are really looking at the performance of your system and not an artifact of the way you are measuring it. A common failure with respect to bit error rate and Strip Chart Analysis is to set your integration period too small. If your strip chart integration period is too small compared to the expected number of errors you receive, the strip chart will appear jumpy. Some integration periods will have errors and others will not. You must make sure that your integration period is set to 10 (even better, 100) times the expected error free interval in your system. This gives you plenty of errors to average into each bit error rate measurement, giving you a good, smooth response.
This same anomaly can affect the burst or non-burst error rate measurements in the same way, so you will want to check that you can expect to get 10 or 100 of each error type in each integration period before studying burst and non-burst error separations.
Bit errors can be caused by:
- Poor SNR (Q) (fiber optics)
- Chromatic dispersion (fiber optics)
- Phase Modulation Distortion (fiber optics)
- Carrier-to-noise (digital video, satellite)
- Head/media gap spacing (magnetic recording)
Burst errors can be caused by:
- Scratches (magnetic recording)
- Defects (disk drives)
- Snow, rain (microwave transmission, satellite)
- Interference (power supply breakthrough, etc.)
- Error propagation in correction coding schemes (fiber optics, magnetic recording, digital video, etc.)
