The power and control unit of the FIBER version, DUAL-PAM/F, contains all actinic and measuring light sources as well as the photodiode signal detector. Fiberoptics is used to guide light from the power and control unit to the sample, and to direct light from the sample back.

The DUAL-PAM/F is designed to assess PS II activities by measuring red-induced fluorescence, and PS I activities by measuring the intensities of reflected light at 830 and 870 nm. The fiberoptics version is required when opaque samples do not allow P700 measurements in the transmissions mode but it is also used in field studies and for screening of plant mutant collections.