Feedforward LF compensation for laser fibre optic transmitter

Direct intensity modulation of laser optical power is probably the one most often used in practice. Classical circuits for semiconductor laser driving are not suitable for operation with unbalanced codes or data transmitted in the form of bursts. The reason for this is a low-frequency (LF) cut-off caused by the laser stabilising circuit. In the paper a concept is presented, along with practical realisation of the laser driving and stabilising circuit for unbalanced codes or burstmode transmission. A developed circuit allows modulation of the laser diode from DC up to the maximum modulation frequency of the laser. Experimental data including pulse tests, eye pattern test and thermal properties of proposed solutions are presented.