Miniature fiberoptic filter and method of manufacture therefor

A miniature fiberoptic filter comprising

• a first optical fiber;
• a first multimode optical fiber segment attached to an end of said first optical fiber, said first multimode optical fiber segment having a step index of refraction and axially aligned with said first optical fiber, said first multimode optical fiber segment having a first length;
• a second multimode optical fiber segment attached to said first multimode optical fiber segment, said second multimode optical fiber segment having a graded index of refraction core and axially aligned with said first multimode optical fiber segment, said second multimode optical fiber segment having a second length, said first and second lengths selected to define a collimation and focusing function for light from and to said first optical fiber;
• a plurality of dielectric coatings on an end of said second multimode optical fiber segment opposite said first multimode optical fiber segment, said plurality of dielectric coatings forming a wavelength-dependent optical filter;
• a second optical fiber;
• a third multimode optical fiber segment attached to an end of said second optical fiber, said third multimode optical fiber segment having a step index of refraction and axially aligned with said second optical fiber, said third multimode optical fiber segment having a third length;
• and
• a fourth multimode optical fiber segment attached to said third multimode optical fiber segment, said fourth multimode optical fiber segment having a graded index of refraction core and axially aligned with said third multimode optical fiber segment, said fourth multimode optical fiber segment having a fourth length, said third and fourth lengths selected to define a collimation and focusing function for light from and to said second optical fiber, said fourth multimode optical fiber segment having an end opposite third multimode optical fiber segment and facing said end of said second multimode optical fiber segment;
• said first optical fiber, said first multimode optical fiber segment, said second multimode optical fiber segment, said plurality of dielectric coatings, said second optical fiber, said third multimode optical fiber segment, said fourth multimode optical fiber segment arranged and oriented with each other so light from said core of said first optical fiber passing through said plurality of dielectric coatings enters said core of said second optical fiber.