Overview

Accurate monitoring of optical power parameters is critical for maintaining the health and performance of your Passive Optical Network (PON). This FAQ guide provides network architects and field engineers with definitive command-line procedures to check the RX/TX optical power of an Optical Network Unit (ONU) directly from the Optical Line Terminal (OLT). It covers vendor-specific syntax, command accuracy, and advanced troubleshooting configurations.

Frequently Asked Questions

Q1: What is the standard OLT CLI command to check ONU optical power on Huawei equipment?

The primary command to query both the receiving and transmitting optical power of an ONU on a Huawei OLT is display ont optical-info. This command provides comprehensive optical parameters for the ONU. You can query the OLT's own transmit (Tx) power using the display port state command . It is important to note that while these CLI queries offer a good indication of power levels, they may have a deviation of up to 2 dB from values measured with a physical optical power meter, especially during low data traffic periods .

Q2: How do I check ONU optical power on Cisco OLTs?

On Cisco OLT platforms operating in a GPON environment, you can retrieve detailed optical status by navigating to the status context with the status/rx-power/show command . The full syntax for querying a specific port is /cli/interfaces/gpon/status/rx-power/show --slot=[SLOT] --port=pon.[PORT] . The output displays a table showing the ONU ID, presence status, and the RX Power in dBm, along with the timestamp of the last reading . For downstream status, the status/show --onuID=[ID] --port=pon.[PORT] --slot=[SLOT] command can show detailed Tx and Rx values across different wavelengths (1310nm, 1490nm, 1550nm) .

Q3: Is there a specific command to check ONU optical power on H3C OLTs?

On H3C OLTs, the designated command to display an ONU's optical transceiver power is display transceiver diagnosis interface onu [interface-number] . However, H3C also supports the command display epon optics-parameters interface olt [interface-number] to view the optical parameters of the OLT port itself . It is crucial to ensure the target ONU is in an operational 'UP' state for the query to succeed, as the system cannot report optical metrics for an offline or deregistered unit .

Q4: What are the typical optical power thresholds for a normal ONU connection?

A normal receive (RX) optical power range for most ONUs is typically between -8 dBm and -27 dBm . If the RX power falls outside this range, it often indicates a physical layer issue such as a dirty connector, excessive fiber loss, or a failing optical module. For proactive network management, you can configure optical power alarm thresholds. For instance, thresholds like rx-power-low threshold -58 (or -29 dBm) and rx-power-high threshold -20 (or -10 dBm) can be set on the OLT to generate alerts when signal levels degrade, allowing for preemptive troubleshooting .

Q5: Does the OLT CLI report the correct TX and RX optical power?

The OLT CLI provides a reliable estimate of optical power, but it is not a replacement for a calibrated optical power meter. The accuracy of the CLI values can vary; they are generally stable and accurate under high traffic loads, but may experience a maximum deviation of 2 dBm from the actual value during low data transmission states . For absolute precision in testing and certification, especially during field troubleshooting, it is recommended to use a dedicated optical power meter to measure the power directly at the ONU or OLT port .

Q6: How can I set up proactive optical power monitoring on my ONUs?

Proactive monitoring is achieved by configuring optical power alarm profiles on the OLT. You can create an alarm template using gpon profile onu-optical-alarm [profile-name] in global configuration mode . Within this template, you define thresholds for RX and TX power using commands like gpon-profile optical-alarm rx-power-high threshold [value] . Once the template is complete, you apply it to the specific ONU port with gpon onu optical-alarm-profile [profile-name]. The ONU will then monitor its optical module and, if a threshold is crossed, it will send an alarm to the OLT via OMCI, which is essential for maintaining Service Level Agreements (SLAs) .

Q7: How do I check ONU optical power on ZTE OLTs?

On ZTE OLT platforms, you can query the optical power status of a PON port using the command show optical-power interface gpon [slot/port] . To check the status of all ONUs under a specific PON port, the command show onu unidirectional-state all can be used to identify the state of each unit before drilling down into specific optical diagnostics . These commands provide a quick health check for the PON segment.

Q8: What vendor-agnostic command can I try to check ONU optical power?

While syntax varies, many OLTs support a generic or semi-standard command structure. On some platforms, you can use the command show gpon interface [interface]:[onu-id] onu optical-transceiver-diagnosis . This command returns the temperature, voltage, bias current, and crucially, the RX and TX power in dBm for the specified ONU . Additionally, within an ONU's shell (accessible via Telnet or the OLT), you can sometimes use the simple command display optics-power . Always consult your specific vendor's CLI guide for the exact syntax, as the commands are not standardized across the industry.