Keysight Laser Source Modules User’s Guide 75Cleaning Instructions 5How to clean instruments with a physical contact interfaceRemove any connector interfaces from the optical output of the instrumentbefore you start the cleaning procedure.Cleaning interfaces is difficult as the core diameter of a single-mode fiberis only about 9 mm. This generally means you cannot see streaks orscratches on the surface. To be certain of the degree of pollution on thesurface of your interface and to check whether it has been removed aftercleaning, you need a microscope.To assess the projection of the emitted light beam you can use an infraredsensor card. Hold the card approximately 5 cm from the interface. Theinvisible emitted light is project onto the card and becomes visible as asmall circular spot.Preferred ProcedureUse the following procedure on most occasions:1 Clean the interface by rubbing a new, dry cotton- swab over thesurface using a small circular movement.2 Blow away any remaining lint with compressed air.Procedure for Stubborn DirtUse this procedure particularly when there is greasy dirt on the interface:1 Moisten a new cotton- swab with isopropyl alcohol.2 Clean the interface by rubbing the cotton- swab over the surface usinga small circular movement.3 Take a new, dry soft- tissue and remove the alcohol, dissolvedsediment and dust, by rubbing gently over the surface using a smallcircular movement.4 Blow away any remaining lint with compressed air.WARNING Never look into an optical output, because this can seriously damageyour eyesight.