The invention relates to an electrode for a plasma generator for generating plasmas at atmospheric pressure or near-atmospheric pressures by means of excitation using microwaves. Accordingly, a PON multicast communication system, an OLT, and an ONU are disclosed. A multi-target link may be implemented as a hypertext link defined by a hypertext link definition embedded in a hypertext document, or as a bookmark for use in a custom bookmark list for a user. The flexible side portion has one side attached to the top panel. The control device controls a maximum output voltage of the DC power supply source so that the voltage difference between the maximum output voltage of the DC power supply source and the load voltage at the time of normal operation falls within a predetermined range in which arc discharge is suppressed.