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An OSN1500 clock source is a signal source that carries timing reference information. The network element synchronizes the clock by phase-locking the phase of the local clock to the timing information of this signal through a phase-locked loop. According to its source, the clock signals can be categorized as follows: External clock source: the clock source extracted through the 2.048MHz or 2.048Mbit/s signal received from the external clock interface. Line clock source: the clock source extracted from the optical signal received from the line board. Internal clock source: the clock generated by the free oscillation of the internal crystal of the network element. The network elements are equipped with an internal clock source so that they can use their own internal clock source if the external source is lost. the OSN1500 device supports external clock source, line clock source, synchronous Ethernet clock source and internal clock source. External clock source: In the device, it supports accessing an external clock source of 2.048MHz or 2.048Mbit/s from a BITS device, and you can use the clock interface board to access the external clock source. Line clock source: Inside the network, the single board that supports the physical layer clock function extracts the clock source through the service signal. Internal clock source: Inside the network, the clock source generated by the free oscillation of the crystal inside the network element.
OSN1500 uses the 2.048MHz or 2.048Mbit/s signal that meets the ITU-T G.703 standard as the external clock interface input or output in the synchronous network system. The external clock source is mainly used in scenarios where the BITS device is interfaced to the OptiX OSN device. 2.048MHz or 2.048Mbit/s clocks are used to realize the input and output of the external clock through the clock interface. The external clock output phase-locked source is a way of external clock access, and the purpose is to prevent the clock signal from drifting after multi-site transmission, and it is necessary to compensate the clock signal in the long chain of clocks.ITU-T G.781 stipulates that the number of network elements in the long chain that need to be clocked compensated is 20 network elements, and considering the factor of transmission distance of the optical fiber, it is generally necessary to compensate the clock when more than 10 network elements are involved. Within the network, OptiX OSN equipment uses SDH single boards or hybrid line single boards to access and transmit line clock sources.
OSN1500B External Clock Source Management Configuration
When you enable the external clock as the clock source, the relevant parameters to be set include external source output mode, external source output time slot, external source output threshold, and so on. The description of the relevant parameters for configuring the external clock output phase-locked source list is shown in Table 1.
|
Domain |
Value field |
Description |
|---|---|---|
|
Network element name |
Example: NE1 |
Displays the name of the network element. |
|
Network Element Synchronized Clock Output <2M Phase Locked Source> |
Default value: internal clock source |
Sets the 2M phase-locked source output of the clock. The internal clock source or line clock source can be selected. Generally, "internal clock source" is selected. Using the 2M phase-locked source to relay the amplified clock source can optimize the clock signal which has already generated certain frequency deviation and drift with the help of other local synchronous sources, at this time, you should cooperate with the clock level setting and select other clock sources (such as "line clock source") as the 2M phase-locked source. |
|
Output impedance of external clock source 1 |
75ohm, 120ohm Default value: 75ohm |
The network element can provide two external output clocks, set the output matching impedance of external clock 1 here. |
|
Output impedance of external clock source 2 |
75ohm, 120ohm Default value: 75ohm |
The network element can provide two external output clocks, set the output matching impedance of external output clock 2 here. |
|
Output mode of external clock source 1 |
2Mbit/s, 2MHz Default value: 2Mbit/s |
The network element can provide two external output clocks, set the output mode of external output clock 1 here. |
|
Output mode of external clock source 2 |
2Mbit/s, 2MHz Default value: 2Mbit/s |
The network element can provide two external output clocks, set the output mode of external output clock 2 here. |
|
Clock source threshold |
No threshold, synchronization equipment timing source (SETS) signal, G.812 local bureau clock signal, G.812 relay bureau clock signal, G.811 clock signal |
Sets the synchronization source threshold for the 2M synchronization output source. The Synchronization Source Threshold is applied to the clock protection function of the S1 byte. The network element clock system will use this value as the quality basis for the clock output, and will only output to the external clock when the quality of the clock exceeds the threshold. You can click Clock Source Threshold for more information. |
The parameters related to configuring the external source attribute of the 2M phase-locked source are described in Table 2.
|
Field |
Value field |
Description |
|---|---|---|
|
2M phase-locked source number |
Example: NE350-2M phase-locked source 1 |
Displays the number of the external clock source output of the network element. |
|
External source output switch |
Enable, disable |
Sets the external source output switch. |
|
External source output mode |
2MHz, 2Mbit/s Default: 2Mbit/s |
Sets the mode of 2M clock signal output from the external source. Click "External Source Output Mode" for details. |
|
External source output time slot |
SA4, SA5, SA6, SA7, SA8, ALL Default: ALL |
Sets the time slot occupied by the SSM in the output 2M clock signal. For example, a setting of SA4 means that the fourth of the eight bits of the first time slot (TS0) of four consecutive even frames is utilized to transmit the SSM.A setting of SA5 means that the fifth of the eight bits of TS0 of four consecutive even frames is utilized to transmit the SSM. This value can only be set in 2 Mbit/s output mode. Click External Source Output Time Slot for more information. |
|
External Source Output Threshold |
Threshold is not activated, not inferior to the G.813 SETS clock, not inferior to the G.812 local office clock, not inferior to the G.812 relay office clock, not inferior to the G.811 clock. Default: threshold not activated |
Sets the quality standard for external source output, below the set threshold the clock output to the outside is stopped. You can click "External source output threshold" for details. |
|
2M Phase-locked Source Failure Conditions |
AIS, LOF, AIS OR LOF, No Failure Condition Default: No failure condition |
Set the judgment condition for 2M phase-locked source failure. If "AIS OR LOF" is selected, either "AIS" or "LOF" alarm will cause the 2M phase-locked source to fail. Click "2M Phase-Locked Source Failure Condition" for details. |
|
2M Phase Locked Source Failure Action |
2M output S1 byte unavailable, send AIS, turn off output. Default value: Shutdown output |
Set the action when the 2M phase-locked source fails. When the 2M phase-locked source fails, the external clock output operates as set in this parameter. Click "2M Phase-locked Source Failure Action" for details. |
The technical information and SDH equipment troubleshooting procedures in this chapter are provided by Shenzhen Optical Transmission Network Technology Company Limited ( www.opticaltrans.com), please retain! Huawei SDH Optical Transmission Equipment,SDH Transmission Equipment Sales
