Any transmitter has an optical power, defined in mW (milliwatts) respectively dBm. 0dBm is equal to 1mW, 3dBm is equal to 2mW (dB, doubling of power).
Any receiver has a minimum sensitivity. This is also defined in mW and dBm.
The Optical Loss Budget is calculated by subtracting the receivers minimum sensitivity from the transmitters optical power. For instance for a transmitter with a power of 1mW ( = 1dBm) and a receiver with a minimum sensitivity of -8dBm the optical loss budget is:
(+1dBm) - (-8dBm) = 9dB
Each Connector and each splice has a transmission loss of its own and the cable itself has a link loss per distance:
- typical connector loss: 1dB (adding two connecting sides with each 0,5dB)
- typical splice loss: 0,5dB
- typical link loss for singlemode cable: 0,4dB/kilometer
For any calculation an additional error margin of 3dB should be considered!
Adding the cable link loss, all connector losses and all splice losses results in the total link loss of a glasfiber transmission line. This total link loss must always be smaller than the optical loss budget!
The Optical Link Loss Budget is the entire optical loss for a fiber link to meet the specifications.
The insertion loss should be measured according to standard IEC61300-3-45.