What is the light attenuation of the optical splitter? How to calculate?
Four common technical indicators of optical splitters: wavelength, insertion loss, additional loss and splitting ratio. In fact, the most important indicator of a beam splitter is the different light attenuation produced by the beam splitter under a specific splitting ratio. Under the conditions of different splitting ratios, the light attenuation of the beam splitter will not be different. So how to calculate the light attenuation of the optical splitter? The optical attenuation value of the optical splitter = transmit optical power + additional loss + insertion loss + bare fiber loss.
1. Calculation of the splitting ratio of the optical splitter
Formula: ki=Pi/SP*100%
Among them, Pi is the required drive power of each optical link, and SP is the sum of the required drive power of each optical link carried by the laser.
Note: In actual use, the manufacturer has indicated the splitting ratio, such as 80% for two points: 20% or 70%: 30%; 70% for three points: 15%: 15%; 70% for four points: 10 %: 10%: 10%.
2. Additional loss calculation
In the actual operation process, the additional loss value can be measured. It is only necessary to carry out the value detection and recording according to a certain operation specification, and to do a good job of classifying the different links.
Generally, the loss of 1×N single-mode standard optical splitter is as follows:
No. of branches | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 16 |
Additional loss/dB | 0.2 | 0.3 | 0.4 | 0.45 | 0.5 | 0.55 | 0.6 | 0.7 | 0.8 | 0.8 | 1.0 | 1.2 |
3. Insertion loss calculation
Formula: IL=-10lg(Po/Pi)
Among them, Po is the optical power at the output end, and Pi is the optical power at the input end.
Note: In the formula, Po/Pi is equivalent to the splitting ratio of the optical splitter, namely: IL=-10lg(ki). For example, there is a two-to-two splitter, which means that the splitting ratio is 20%:80%. The theoretical value of the insertion loss of the 20% split optical link is -10lg (20%), which is approximately equal to 6.99dB.
4. Bare fiber loss calculation
In actual operation, this value does not need to be calculated, and there is a certain reference standard. It is necessary to strictly refer to the numerical standard to measure the loss values of different wavelengths to determine the final loss value.
Wavelength | Optical fiber attenuation coefficient (reference value) |
1310nm | 0.3~0.4dB/km |
1550nm | 0.15~0.25dB/km |
850nm | 3.75dB/km |
Note: Active connector attenuation: generally 0.5dB each.
