ThistypealsocanbecalledPulseModulationLaserDiodeModule.Itcanbedividedintooutexternalmodulationandinnermodulation.ExternalmodulationLaserDiodeModulehasspecial-purposesignalsocket.Pulsesignalisconnectedbythecustomer.Signalcanbesinewaveorsquarewave.Modulationfrequencycanbeto1MHz;Innermodulationtypenoneedsignalfromoutside.Itworkswithpulse.Butworkingfrequencycan tbechangedatwill.Thistypeisnormallymadetocustomers requests.