OPTICAL DISCRIMINATORS AND SYSTEMS AND METHODS
An optical multi-filter discriminator suitable for treating optical signals from an optical signal source, e.g., a direct modulated laser ("DML"), comprises a first optical filter, a second optical filter optically coupled to the first optical filter, an input port operative to receive optical signals from an optical signal source and oriented to launch the optical signals directly or indirectly to the first optical filter, and an output port oriented to receive optical signals treated by the multiple optical filters and operative to pass the optical signals directly or indirectly to an optical waveguide "downstream" of the discriminator. The first filter is transmissive (i.e., at the angle of incidence received from the input port) of at least a first wavelength band having a first center wavelength and reflective (again, meaning in this instance at the angle of incidence received from the input port) of at least a second wavelength band different from the first wavelength band. The optical multi-filter discriminator defines an optical path for optical signals in the first wavelength band received by the input port. The optical path includes at least (i) transmission from the input port directly or indirectly to and through the first optical filter, and (ii) then, prior to the output port, from the first optical filter directly or indirectly to the second optical filter at an angle of incidence at which the second optical filter is reflective of the first wavelength band. The at least two filters of the optical multi-filter discriminator can be packaged together in a common housing along with some or all of the other components, if any, of the optical multi- filter discriminator, e.g., lenses, isolators, mounting components, etc. An optical communication system comprises a DML or other optical signal source optically coupled to one or more of the aforesaid optical multi-filter discriminators. A method of operating an optical communication system comprises actuating an optical signal source to generate optical signals to one or more of the aforesaid optical multi-filter discriminators to increase the extinction ratio, and by passing the signals through the multi-discriminator to a downstream optical fiber or other optical waveguide.