Patent ID: 7711220

Claim:
A mode selective optical fiber stub assembly comprising: an optical fiber stub having a core and a cladding layer, the fiber stub having a proximal portion and a distal portion, the proximal portion having a proximal end corresponding to an entrance facet of the stub and the distal portion having a distal end corresponding to an exit facet of the stub, the cladding layer having an inner surface that is in contact with an outer surface of the core, the cladding layer having an inner diameter corresponding to the inner surface of the cladding layer, the cladding layer having a first outer diameter corresponding to the outer surface of the cladding layer in the proximal portion of the fiber stub, the cladding layer having a second outer diameter corresponding to the outer surface of the cladding layer in the distal portion of the stub, wherein the first outer diameter is smaller than the second outer diameter; a ferule, the fiber stub being secured within the ferule, wherein a cavity formed in the ferule surrounds the proximal portion of the fiber stub; and a light-absorbing material disposed within the cavity formed in the ferule and surrounding at least the outer surface of the cladding layer in the proximal portion of the fiber stub, the light-absorbing material having a refractive index that is equal to, or at least substantially equal to, a refractive index of the outer surface of the cladding layer, wherein the refractive indexes of the light-absorbing material and of the outer surface of the cladding layer remain at substantially constant values that are substantially equal to each other, wherein the light-absorbing material is absorptive to light of at least one particular wavelength or wavelength range such that at least one mode of light of the particular wavelength or wavelength range that is propagating in the cladding layer propagates into the light-absorbing material and is absorbed thereby, and wherein the light-absorbing material surrounding at least the outer surface of the cladding layer in the proximal portion of the fiber stub creates a pin hole opening in the proximal end of the fiber stub, wherein light from a light source is launched into the fiber stub through the pin hole opening.