| Parameter | Definition |
| φP | The pump photon flux |
| φs | The signal photon flux |
|
| The stimulated emission cross section for Er+3 |
|
| The absorption cross section for Er+3 |
|
| The stimulated emission cross section for Yb+3 |
|
| The absorption cross section for Yb+3 |
| A21 | The spontaneous emission rate of Er+3 |
| A65 | The spontaneous emission rate Yb+3 |
| K and K' | The coefficient of energy transfer (m3∙s−1) for the concentrations of Er+3 and Yb+3 |
| Cup | The up conversion coefficient |
