The present invention provides optical filters that can be used in a range of telecommunications applications including optical multiplexers/demultiplexers, optical routers, and optical gain scalers. The optical filter is modular, using two or more couplers with a pair of delay paths between each pair of couplers in a sequence to generate a range of optical filter functions. The desired filter profile/function is obtained by proper selection of the coupling ratio for each coupler and by the length of each pair of delay paths. The couplers may be implemented as polarization or intensity beam splitters positioned along the optical path. Each coupler couples in controllable amounts, one or two inputs with the corresponding pair of delay paths. Where a coupler is implemented as a polarization beam splitter, the coupling is accomplished by input to the coupler of polarized light and by the subsequent separation of orthogonal "P" and "S" components of that light onto corresponding ones of the pair of delay paths. Where coupling is implemented with an intensity beam splitter, the coupling is accomplished by input of light with the percentage of reflection and transmission of the light determining the coupling ratio or percentage of the light input onto corresponding ones of the pair of delay paths. The pair of delay paths includes in an embodiment of the invention, passive thermal stabilization. The passive thermal stabilization of the filter(s) is accomplished by a plurality of optical elements positioned in and defining the optical path length of each member of the pair of paths. These optical elements are designed so that the optical path length difference between the pair of delay paths remains substantially invariant across a range of temperatures.
CROSS-REFERENCE TO RELATED APPLICATION
This application Claims priority from Provisional Application No. 60/269,190 entitled "ATHERMALIZED POLARIZATION INTERFEROMETER" filed on Feb. 14, 2001 which is incorporated herein by reference in its entirety.
An athermal interferometric wavelocker is disclosed having a beam splitter combiner and a first arm of a first material having a first refractive index, a first length, and a first coefficient of expansion; and, a second arm of a second material having a second refractive index, a second length, and a second coefficient of expansion. The refractive indices, lengths and coefficients of expansion of the first arm and the second arm are selected to provide a substantially athermal structure operating at ambient temperatures. The first arm and second arm have inner end faces that meet adjacent faces of the beam splitter and combiner. The first and second arms are of a different optical path length such that light launched into the beam splitter and combiner, interferes upon recombining, and is output from a combiner output port to provide a wavelocker signal having a detectable characteristic which varies with wavelength.
An optical interleaver for use in a range of telecommunications applications including optical multiplexers/demultiplexers and optical routers. The optical device includes an optical processing loop which allows multi-stage performance characteristics to be achieved with a single physical filtration stage. Optical processing on the first leg and second legs of the loop is asymmetrical thereby improving the integrity of the optical signals by effecting complementary chromatic dispersion on the first and second legs. A fundamental filter cell within the interleaver filters optical signals propagating on each of the two legs of the optical loop which intersects the fundamental filter cell.
