M02067 Datasheet, PDF (12/20 Pages) M/A-COM Technology Solutions, Inc. – Rise and fall times <150 ps

M02067 -12/-13
3.3 Volt Laser Driver IC for GbE and Fibre Channel to 2.1 Gbps
Figure 3-5. 2 x Fibre Channel 2.125 Gbps Electrical Eye Diagram
2 x Fibre Channel 2.125 Gbps
Rev V4
30 mApp Modulation Current
3.4
Mean Power Control Loop
The M02067 employs a Mean Power Control (MPC) loop to maintain a constant optical output power from the laser
across temperature, time and power supply variations. Laser diodes used for communication purposes come with
integrated photo-diodes to monitor the output power and provide the feedback for the MPC loop. The MPC loop (or
its integrated safety features) cannot be used without this feedback.
The MPC loop adjusts the laser bias current so that the monitor current from the photo-diode is matched to a
reference current set by a single external resistor, R_MPCSET. The time constant of the MPC loop is determined by
C_MPC.
Table 3-1.
C_MPC
0
1 nF
10 nF
100 nF
MPC Loop Bandwidth
6 dB cutoff frequency
17 MHz
100 kHz
10 kHz
1 kHz
(at 6 dB cut off frequency) vs C_MPC (for nominal process)
Figure 3-6 shows the bias current vs RMPCSET over the full operating temperature range for a typical laser and
monitor photodiode.
12
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