Optical Budget
Calculate the available optical power budget between transmitter and receiver.
About Optical Budget
The optical power budget is the total dB range a fiber link has to work with — the difference between the transmitter's launch power and the receiver's minimum sensitivity. Subtracting the actual total loss along the path (fiber attenuation, splices, connectors) from that budget gives the link margin, which must stay positive, ideally with several dB of headroom, for the link to operate reliably over its lifetime.
Formulas
Power budget
budget = Tx_power − Rx_sensitivity
Link margin
margin = budget − total_loss
Worked example
With the default values below, Optical Budget returns Link Margin of 10.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Transmitter Power
- 0 dBm
- Receiver Sensitivity
- -22 dBm
- Total Link Lossminimum 0 dB
- 12 dB
Results
- Link Margin
- 10.00 dB
- Total Power Budget
- 22.00 dB
- Received Power
- -12.00 dBm
Step by step
- 1Values used
- 2Power budget
- 3Link margin
- 4Link Margin= 10.00 dB
- 5Total Power Budget= 22.00 dB
- 6Received Power= -12.00 dBm
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What's the difference between this and the Fiber Loss Budget calculator?
The Fiber Loss Budget calculator breaks total loss down into its components (fiber length × attenuation, connectors, splices) and computes margin from those inputs. This calculator takes a single already-known total loss value and focuses on the overall budget-vs-margin relationship.
What margin is typically required for optical links?
A minimum of 3 dB is a common design rule, with 5-6 dB or more preferred for links expected to age, be re-spliced, or operate in variable environmental conditions, to avoid the link degrading below usability over its operational life.
Can increasing transmitter power always fix a negative margin?
Only up to a point — transmitters have a maximum safe launch power (exceeding it can cause nonlinear effects or damage receivers at short distances), and regulatory/eye-safety limits also cap output power, so excessive loss often needs to be addressed by reducing distance/splices instead.
Does a positive margin guarantee the link will always work?
It indicates the link should work under the conditions modeled, but real links can still fail from unaccounted factors like fiber degradation over time, dirty connectors, bend losses, or component aging — which is exactly why margin, not zero, is the design target.