A Highly Versatile Broadband Tunable Compact Spectral Filter for Fiber Optic Communications

Phycical Optics Corporation (POC) proposes a monolithic tunable optical filter module, compatible with the size and power requirements of military fiber optic systems, and which overcomes drawbacks of current state-of-the-art tunable filters. This new tunable filter is based on the unique concept of spectrum division by spatial filtering (SDSF). This concept can be readily implemented in a minaturized form without any moving parts by integrating four of POC's well developed technologies; fiber optics, planar waveguides, planar (volume holographic) diffractive optics, and spatial light modulators (SLM). The filter module will be highly stable (thermal and long-term), rugged, and compact (low profile printed circuit board mountable). Innovations of our proposed approach include: (1) spectrographic optics are miniaturized and confined to 2D, using waveguide geometry, which is highly compatible with fiber optic systems. Spatial filtering by an SLM array eliminates all mechanical movements in the tuning process; (2) a single, very broad band, multiplexed volume holographic grating provides very wide band tunability with uniformly high efficiency; (3) parallel addressable 1D reflective SLM arrays allow recombination of the filtered spectrum back through the same set of planar optics and into the output fiber; a very efficient process.