Free-Space Link Margin
Calculate a free-space optical link budget from caller-supplied gains, losses, and sensitivity.
Description
A free-space link budget adds supplied transmitter/receiver gains and subtracts path loss.
A free-space link budget adds supplied transmitter/receiver gains and subtracts path loss. Margin compares predicted received power with sensitivity.1
Calculate a free-space optical link budget from caller-supplied gains, losses, and sensitivity.
When to use Free-Space Link Margin
Use this tool to calculate a free-space optical link budget from caller-supplied gains, losses, and sensitivity.
Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
How to use Free-Space Link Margin and understand its results
- Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
- Enter transmitPowerDbm, transmitGainDb, receiveGainDb, pathLossDb, receiverSensitivityDbm using the field table and calculation rules, then run the tool.
- Read receivedPowerDbm, linkMarginDb, closesLink. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| transmitPowerDbm | Transmit power (dBm) | number | Required |
| transmitGainDb | Transmit gain (dB) | number | Required |
| receiveGainDb | Receive gain (dB) | number | Required |
| pathLossDb | Path and weather loss (dB) | number; minimum: 0 | Required |
| receiverSensitivityDbm | Receiver sensitivity (dBm) | number | Required |
Enter finite signed powers/gains/sensitivity and nonnegative path loss. Return dBm, margin dB and inclusive margin≥0 link flag.
receivedDbm=transmitDbm+TxGainDb+RxGainDb−pathLossDb; margin=received−sensitivity Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| receivedPowerDbm | Received power (dBm) | number |
| linkMarginDb | Link margin (dB) | number |
| closesLink | Closes link | boolean |
{
"input": {
"transmitPowerDbm": 20,
"transmitGainDb": 10,
"receiveGainDb": 10,
"pathLossDb": 5,
"receiverSensitivityDbm": -60
},
"output": {
"receivedPowerDbm": 35,
"linkMarginDb": 95,
"closesLink": true
}
}Limitations and assumptions
No path loss, weather, pointing, bandwidth or reliability model is derived.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use Underwater Optical Mode Comparison: Compare Beer–Lambert transmission for two underwater optical bands. For a complementary task, use Lidar Photon Return: Estimate monostatic lidar received photons from pulse energy and geometric spreading.
References
-
Free-Space Link Margin — tool.io
Similar or alternative tools
- Underwater Optical Mode Comparison
Compare Beer–Lambert transmission for two underwater optical bands.
- Lidar Photon Return
Estimate monostatic lidar received photons from pulse energy and geometric spreading.