Huawei OptiX PTN Series Quick Installation Manual page 37

3
Checking Optical Power
The following table describes comparison between the transmit optical power of 50 Gbps optical modules and
damaged optical power threshold at the receive end：
Optical Maximum
Module Type Average Transmit
Optical Power
50GBASE-LR
4.2
(10km)
50GBASE-ER
(40km) 6.6
For applications of the 50 Gbps optical module supporting a distance of 40 km:
•
1. To ensure that the optical module runs stably for a long time, adjust the receive optical power of the optical module to
a value lower than -4 dB. According to the IEEE 802.3 standard, if the receive optical power of the optical module
exceeds -2.3 dB, the optical module may be permanently damaged.
•
2. Before connecting to the optical module, use an optical power meter to measure the receive optical power (P). If P is
less than -4 dB, the optical module can be directly connected. If P is greater than -4 dB, add an optical attenuator at the
receive end to ensure that the receive optical power is less than -4 dB. Alternatively, add an optical attenuator (no less
than 10 dB is recommended) before the interconnection, and then adjust the optical attenuator based on the site
requirements to prevent the optical module from being damaged.
•
3. If a loopback occurs on the pigtail of the optical module or the optical module is connected for a short distance, an
optical attenuator must be added. It is recommended that the optical attenuator be no less than 10 dB.
4
Checking Optical Link
Since the 50G/200G optical module link uses the PAM4 encoding technology, the link is more sensitive to multipath
reflection interference of signals. If the fiber link connector, fiber section, or fiber splicing surface is dirty, optical signals are
reflected back and forth on the fiber link, causing interference due to co-channel noise on the receive side. As a result, the
optical link is unstable or intermittently disconnected.
Before installing the 50G/200G optical module, you are advised to use an OTDR meter to check the optical link. The check
method is as follows:
Remove optical
modules from
both sides and
remove optical
fibers.
Because the transmit optical power of the OTDR meter is much higher than the damaged optical power threshold at the
receive end, the optical fiber must be removed from the optical module when the OTDR meter is used to test the optical
path quality.
Minimum Average
Transmit Optical
Power
-4.5
0.4
Check the receive and
transmit end faces of
the optical module
using the fiberscope.
If dirty substances
exist, use the
cleaning tool.
Damaged Optical
Power Threshold
at the Receive End
5.2
-2.4
Check the pugtail
end face using the
fiberscope.
If dirty substances
exist, use the
cleaning tool.
34
Description
The damaged optical power
threshold is greater than the
maximum average transmit optical
power, posting low self-loop risks.
The damaged optical power
threshold is 9dBm lower than the
maximum average transmit optical
power and 2.8dBm lower than the
minimum average transmit optical
power, posing high self-loop risks.
In this case, an optical attenuator
must be configured for self-loop.
Check the optical path
insertion loss and
reflection using the
OTDR tester.
Process the segment
based on the check
result.