Total Power Consumed by an Entire Opto-electronic Link

The total power consumed by an entire opto-electronic link is given by: Power required by laser driver. Power required by laser Power required by photodiode Power required by TransImpedance Amplifier for converting photocurrent to voltage Power required by Clock and Data Recovery circuitry For zero length link

P Driver According to various references we have: Dominated by the capacitance of the laser, about 10 pF. V dd =Typical 3.3 V Bit/second Switching factor = duty cycle of the link (modulation and activity dependant)

P VCSEL Steady state power dissipation of a VCSEL (vertical cavity laser – or conventional diode laser).  6 mA for VCSEL  50 mA for conventional Laser diode (LD)  20 mA for VCSEL  80 mA for LD  0.7V About 1.8 V About 0.2 V

P photodiode The photodiode requires a bias voltage and the associated power is negligible respect to TIA power. APDs require high voltage sources that are not energetically negligible: Typical power required by APD bias circuitry is 10 mW (activation time hundreds ms) see datasheet of LT3482. P TIA  =2  Bitrate Dark current 40 nA About photodiode capacitance (1 pF) Amplifier gain at DC and in band about 5000 About 15 V 3.3 V Output capacitance of amplifier, about 1 pF Output voltage swing (3V)

P CDR Capacitance of the clock and data recovery unit. About 1 pF