1. Fiber Optic Communication Lec 11 By
Engr. Muhammad Ashraf Bhutta

12. Absorption
Ground State E1 E2 E3 E4 E5
Excited state l =
122nm

14. Spontaneous Emission l =122nm E5 Excited state E4 E3 E2 E1
Ground State E1 E2 E3 E4 E5
Excited state l
=122nm

16. Stimulated Emission
Ground State E1 E2 E3 E4 E5
Excited state l
=122nm

18. Energy Pumping Energy level diagram for a typical laser material. _ ~
Pumping level Lifetime
nsec ~ _
Level C
Level B
Level A
Ground State
Metastable
state Lifetime msec ~ _ X Y
Energy level diagram for a typical laser material.