Paste Transceiver Output
Supports Cisco NX-OS, IOS/IOS-XE, Arista EOS, Juniper JunOS, Palo Alto PAN-OS, Nokia SR OS, Fortinet FortiOS, Extreme EXOS, and Dell OS9
What is Light?
Light is a free, browser-based tool for analyzing SFP, SFP+, QSFP+, and QSFP28 transceiver diagnostics. Paste the raw CLI output from your network switch and get an instant visual breakdown of optical health, power levels, and link budget.
Multi-Vendor Support
Works with Cisco NX-OS (Nexus), Cisco IOS/IOS-XE (Catalyst), Arista EOS, Juniper JunOS, Palo Alto PAN-OS, Nokia SR OS, Fortinet FortiOS, Extreme EXOS, and Dell OS9. Auto-detects the vendor from your paste — no manual selection needed.
Instant Diagnostics
Analyzes temperature, voltage, laser bias current, Tx power, and Rx power against alarm and warning thresholds. See at a glance which parameters are healthy, degraded, or critical.
Link Budget Analysis
Calculates path loss, Rx margin to alarm, and highlights whether your fiber link has adequate headroom — essential for troubleshooting intermittent optical errors and CRC issues.
Side-by-Side Compare
Paste two transceiver outputs and compare them side by side. See per-parameter deltas color-coded to show improvements vs degradation — ideal for before/after checks, A/B link troubleshooting, or comparing near and far end optics.
100% Private
Everything runs in your browser. No data is sent to any server. Safe to use with production network data, internal interface names, and serial numbers.
Supported Commands
- Cisco NX-OS:
show interface transceiver details - Cisco IOS-XE:
show interfaces transceiver detail - Arista EOS:
show interfaces transceiver detail - Juniper JunOS:
show interfaces diagnostics optics - Palo Alto PAN-OS:
show transceiver-detail - Nokia SR OS:
show port detail - Fortinet FortiOS:
get system interface transceiver - Extreme EXOS:
show ports transceiver information detail - Dell OS9:
show interfaces transceiver
What do the readings mean?
- Tx Power (dBm)
- The optical power your transceiver is transmitting. Typically between -8 and +5 dBm for most SFP+ modules.
- Rx Power (dBm)
- The optical power received from the far end. Low Rx power usually indicates fiber loss, dirty connectors, or a failing remote transceiver.
- Link Budget / Path Loss
- The difference between local Tx and remote Rx power. Higher values mean more signal is being lost in the fiber path.
- Margin to Alarm
- How much headroom remains before Rx power drops below the low-alarm threshold and the link becomes unreliable.