A study on radiated emissions from fiber optical modules

Attempts have been made to evaluate and investigate the radiated emissions from fiber optical modules that are currently available in the market. Far electric field strength measurements show that the radiated emission has a peak at a high-order harmonic wave of the fundamental pulse frequency and r eaches a level exceeding the limiting values of the CISPR noise specificati ons. Near magnetic field distribution measurements show that the source of the interference noise lies between a light emitting diode (LED) module and an LED driver. These measurements are compared with those of electromagnet ic field calculations based on a high-frequency equivalent circuit. As a re sult, it was established that both the peaking effects of deformed pulse wa ves transmitted between an LED module and an LED driver and the radiation c haracteristics of the optical transmitter circuit act as factors for increa sing the: radiation level of the peak frequencies in the radiated emission from fiber optical modules.