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 Fully compatible with all 8152x and 8162x Optical Heads. Fits in Mainframe all of 8163/8164/8166 series. Flexibility through 1- and 2- channel option.