Ohishi, Nagano (NICT)

Decreasing of output power of superluminescent-diodes (SLDs) for optical levers is being reported recently. According to manufacturer, it might be caused by the degradation of SLDs due to the back-reflected light from a collimation lens attached to patch code (not the lifetime of SLDs). Therefore, we measured the output voltage of back-facet monitor photodiode (PD) in the SLD modules used for IMMT1 and 2 optical levers.

The measured voltages were not changed with/without the patch code with collimation lens. (They were not changed even if the strong back-reflected light were intentionally returned by aluminum plate used instead of a low-reflectivity mirror.) The data from 7 pin are the output voltage of the PD (See attached file for pin assignement).