The application of multiplex spectrometry to cryogenically cooled LWIR extrinsic photodetectors is limited by system noise. This noise limitation results in a detector NEP that is directly proportional to bandwidth. Therefore, multiplex schemes that require increased bandwidth are not productive of real advantage. However, doubly encoded systems that are based on 2n - 1 or n + N - 1 measurements have the potential to provide a real throughput gain proportional to the number of elements used on the throughput matrix.
Clair L. Wyatt and Roy W. Esplin, "Multiplexed Dispersive Spectrometers Using Reduced Background Infrared Detectors," Appl. Opt. 13, 2651-2653 (1974)