| Date | May 2012 | Marks available | 3 | Reference code | 12M.3.HL.TZ2.5 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Calculate | Question number | 5 | Adapted from | N/A |
Question
This question is about transmission of digital signals in an optic fibre.
The input power to a single optic fibre X is 25 mW. The signal needs to be amplified when the power has been attenuated to 4.0 ×10–19 W. The attenuation loss in the optic fibre is 1.8 dB km–1.
Calculate the maximum distance between amplifiers in the system.
Markscheme
\(\frac{I}{{{I_0}}} = 101{\rm{g}}\left[ {\frac{{25 \times {{10}^{ - 3}}}}{{4 \times {{10}^{ - 19}}}}} \right]\left( { = 168} \right)\);
\(\frac{{168}}{{1.8}}\);
93 km;
Examiners report
