Optical Link Budget Calculator

Plan and verify fiber optic links by calculating power budgets, attenuation losses, and link margins. Determine if your fiber deployment will meet minimum receiver sensitivity requirements for specific SFP/SFP+ modules.

SFP/SFP+ Module Type:

Fiber Type:

Link Distance:

Connector Pairs (Patches):

Show Advanced Options (Splices, Custom Margins)

Fusion Splices:

Mechanical Splices:

Connector Loss (dB/pair):

Safety Margin (dB):

Calculation Results PASS

Link Margin

+5.2 dB

Link has sufficient power budget

Power Budget Summary

Transmit Power (Tx):

Receiver Sensitivity (Rx):

Available Link Budget:

Loss Breakdown

Loss Component	Value	Loss (dB)

About Optical Link Budget Calculations

What is Link Budget? Link budget is the accounting of all gains and losses in a fiber optic transmission system. It determines whether the optical power received at the detector is sufficient for reliable data transmission.

Basic Formula:

Link Margin = Link Budget - Total Loss - Safety Margin

Where:

Link Budget = Transmit Power (dBm) - Receiver Sensitivity (dBm)
Total Loss = Fiber Attenuation + Connector Loss + Splice Loss
Link Margin = Remaining power budget (should be positive for viable link)

Fiber Attenuation Values:

OS2 (Single-mode): 0.4 dB/km @ 1310nm, 0.25 dB/km @ 1550nm
OM3 (Multimode): 3.0 dB/km @ 850nm, 1.0 dB/km @ 1300nm
OM4 (Multimode): 3.0 dB/km @ 850nm, 1.0 dB/km @ 1300nm (better bandwidth)
OM5 (Multimode): 3.0 dB/km @ 850nm (optimized for SWDM)

Typical Loss Values:

Connector Pairs: 0.5-0.75 dB per mated pair (SC, LC, etc.)
Fusion Splices: 0.1 dB each (very low loss)
Mechanical Splices: 0.3-0.5 dB each (higher than fusion)

Why Safety Margin Matters:

A 3 dB safety margin accounts for:

Component aging and degradation over time
Temperature variations affecting laser output
Dirty or contaminated connectors
Fiber bending or stress-induced losses
Manufacturing tolerances and measurement uncertainties

Understanding Results:

PASS (Green): Link margin ≥ 0 dB. Link should work reliably.
WARNING (Yellow): Link margin 0 to -1 dB. May work but risky. Clean connectors and retest.
FAIL (Red): Link margin < -1 dB. Link will likely not establish or will have errors. Need different SFP, shorter distance, or better fiber.

Distance Limits:

Beyond power budget, fiber links are also limited by:

Chromatic Dispersion: Limits single-mode links at higher speeds
Modal Dispersion: Limits multimode links based on bandwidth (MHz·km)
IEEE Standards: Specify maximum distances for each transceiver type

Best Practices:

Always clean connectors before testing or deployment
Use proper bend radius (typically 10x cable diameter)
Verify fiber type matches SFP module requirements
Document power measurements for baseline reference
Use OTDR for long or complex links with many splices
Consider environmental conditions (temperature, humidity)

Standards References:

IEEE 802.3: Ethernet standards for fiber optics
TIA-568: Commercial building cabling standard
ITU-T G.652: Single-mode fiber specifications (OS2)
IEC 60793: Optical fiber specifications

Troubleshooting High Loss:

If your link fails the budget calculation:

Clean all connectors thoroughly with proper fiber cleaning tools
Inspect connectors for scratches or damage (use fiber microscope)
Verify correct fiber type is being used
Check for sharp bends or kinks in fiber cable
Test individual patch cords to isolate bad jumpers
Consider using higher power SFP or more sensitive receiver
Reduce number of connection points if possible