ABSTRACT
Many optical systems require the use of filters or frequency-selective arrangements. In most cases the filter has a fairly simple task, e.g. defining the range of signal frequencies coupled onto a bolometric detector. However, it is worth noting that, in conventional electronics and microwave systems, frequency-sensitive arrangements are used for a number of other functions. These include impedance matching, reflection suppression, and diplexing or multiplexing. All these functions may also be provided in optical systems by employing appropriate arrangements.
