1. Background

When testing the GPON module of the MS solution for ZTE customers, during the ONU and OLT connection process, when the first BEN signal is enabled, the "0" level is raised very high; When the first long light emission occurs, the process of establishing the light signal slowly rises. This may cause anomalies such as slow registration. Need confirmation and improvement.

2. Abnormal reproduction

1. To make the results more reliable, the startup process of ZTE ONU registration was simulated as follows:

Connect the first BEN ON luminous waveform of OLT, as shown in Figure 1.

Figure 1

Note: The first BEN ON was not fully established

2. Connect the OLT to the non first BEN ON emitting waveform, as shown in Figure 2.

Figure 2

3. The first long luminous waveform when powered on is shown in Figure 3.

Figure 3

Note: As shown in the figure, the process of establishing a long luminous time is slow.

4. The second long luminous waveform when powered on is shown in Figure 4.

Figure 4

3. Analysis and improvement

Based on the phenomenon reproduced above, it can be seen that the first emission level of OLT is raised very high when connected, mainly because the BIAS value given by the initial power on configuration table is not very accurate, because the loaded bias current is slightly higher, resulting in high optical power and low extinction ratio. After the APC is powered on in the optical module, the bias value is adjusted to decrease. After a period of adjustment, the APC adjusts the optical power to the appropriate value.

So, when the ONU is started, giving a suitable Bias value can adjust the light to the optimal state. However, the Bisa value at room temperature startup is not the same as the Bisa value at high temperature startup, so a suitable Bias LUT needs to be made as the initial Bias value for module startup.

The following test results simulate the startup process of ZTE ONU registration after adding the correct Bias LUT:

1. Connect the first BEN ON luminous waveform of OLT, as shown in Figure 5.

Figure 5

2. Connect the OLT to the non first BEN ON emitting waveform, as shown in Figure 6.

Figure 6

3. The first long luminous waveform when powered on is shown in Figure 7.

Figure 7

4. The second long luminous waveform when powered on is shown in Figure 8.

Figure 8

4. Conclusion

By adding Bias LUT, customer feedback on startup anomalies can be improved. It should be noted that the Bias value of Bias LUT is only used as the first BEN ON after startup, and the subsequent emitted light power is controlled by APC to emit light.