Single Optical Head Interface Module The Agilent (now Keysight) 81618A single interface modules is used to connect optical heads (Agilent 8162x) to the mainframes 8163A/B, 8164A/B or 8166A/B. Fully compatible with all 8162x optical heads Fits in all 8163/8164/8166-series 1-channel option Following optical heads are used with these interfaces: 81623B Ge, +10 dBm to -80 dBm 81624B 5 mm InGaAs, +10 dBm to -90 dBm 81626B InGaAs, +27 dBm to - 70 dBm 81628B InGaAs, +40 dBm to - 60 dBm