Hewlett Packard High-Speed Lightwave Converter. The part number is HP 83440B, option H10. There is a 1 meter long fiber optic cable with ST connector Following info is from original seller. It is a fast, accurate, DC-coupled optical-to-electrical converter packaged as a small optical probe. It can be mounted directly to electrical instrument front panels, such as the four channel test set of an HP high-speed digitizing oscilloscope (54120 type). The device has option H10 which is a special modified version of the HP 83440B. The modifications include the following: a 1 meter long fiber optic cable with ST connector, attached; seperate cable is not required, base can be bolted down to another piece of equipment for convenient mounting, unit has special PC assembly to provide the ability to monitor photodiode bias current. unit has 3 feedthru capacitors on the case to allow clean direct connection of DC supply (12 to 15 volts) and one connection to the bias current monitoring circuit. Data sheet, HP's description of modifications (Option H10) and certificate of calibration are included. The device was removed from its original shipping container with the intention of installing it in a circuit module but seems have not been used.