The single ( Agilent 81618A ) or dual (Agilent 81619A ) interface modules are used to connect optical heads ( Agilent 8162x ) to the mainframes 8163A/B, 8164A/B or 8166A/B.

Following optical heads are used with these interfaces:
81623B Ge, +10dBm to -80dBm
81624B 5mm InGaAs, +10dBm to -90dBm
81626B InGaAs, +27 dBm to - 70 dBm
81628B InGaAs, +40 dBm to - 60 dBm