Optical Fiber Link Budget Calculator

A link budget checks whether enough light reaches the receiver. You start with the power the transmitter sends, subtract every loss along the way (fiber, connectors, splices, splitters), and compare what is left with the receiver's sensitivity.

Use it when you plan or troubleshoot a link: FTTH and GPON access networks with splitters, backbone and metro links between sites, and single-mode or multimode links in a campus LAN or data centre. A good design keeps a safety margin for ageing, repairs and temperature.

Fiber loss

= attenuation (dB/km) × length (km)

Connector loss

= connectors × loss per connector

Splice loss

= splices × loss per splice

Total link loss

= fiber + connectors + splices + splitter + other losses

Power budget

= Tx power − Rx sensitivity

Expected Rx power

= Tx power − total link loss

Link margin

= power budget − total link loss − safety margin

Max reach

= (power budget − all non-fiber losses − safety margin) ÷ attenuation

All values are in dB or dBm. The calculator works at full precision and rounds to two decimals only for display. Status: PASS when the link margin is 0 dB or more; MARGINAL from −1 to 0 dB; FAIL below −1 dB or when the expected Rx power is below the receiver sensitivity.

These are planning values. Real cables, connectors and transceivers vary, so use the figures from your datasheets when you have them.

• It only counts power loss. It does not model chromatic or modal dispersion, or the bandwidth limits of multimode fiber, which can cap the distance before loss does (for example 10G over OM3).
• It uses typical values, not measurements. It does not replace OTDR traces or measured insertion loss.
• Always verify a built link with a light source and power meter or an OTDR before putting it into service.