Why add an optical attenuator
Optical attenuators are commonly used in, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter and receiver levels. They are usually installed at the transmit end of active modules, such as OTU and OSC boards, to prevent the downstream receiver modules from being burnt due to excessively high output optical power. Transmitter power (TP) = 3dBm Receiver maximum optical input power (MP) = -6dBm Total losses (TL) = 5dB Minimum attenuation required = MP + TL – TP = -6dBm + 5dB – 3dBm = – 4 dB At a minimum, a 4 dB attenuator is required.
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