Many optical data-transmission systems require accurate measurement of the light output at different parts of the systems. Some of these systems need light power as a feedback signal to optimize system performance. The hard part is accurately measuring power.
Analog Devices optimized its ADL5310 dual logarithmic converter for such situations. Potential applications include laser-control circuitry, optical switches, attenuators, and system monitoring. The device will help simplify the design of control loops for erbium-doped fiber amplifiers (EDFAs), variable optical attenuators (VOAs), and optical add/drop multiplexers.
The inputs to the ADL5310 come from photodiodes whose varying currents are converted into linear-in-decibel voltage outputs. The input dynamic range spans six decades from 3 nA to 3 mA. The nominal output slope of 10 mV/dB (200 mV/decade) is externally scalable. External resistors may independently set intercepts. The output buffer amplifiers are user-configurable. The device operates from a single supply as low as 3 V. However, dual-supply operation is possible as well.
The ADL5310 is housed in a space-efficient 24-lead 4- by 4-mm LFCSP. Pricing is $11.33 each in 1000-unit quantities.