Specialty Optical Fibers Handbook

ranging from 0:052 to 0:09 ps=nm

2

-km. The three-layer core structure includes a

high-index, low-alpha, central core, surrounded by a narrow annular region with

index that is nearly matched to the cladding index. This structure is then

surrounded by a second annular region with index raised above the cladding

index. Fabrication techniques that build the index structure by radially layering

multiple deposition steps, such as the OVD, MCVD, or PCVD methods, have

been successfully used for fibers of these designs. It is also possible to use

the VAD method when multiple deposition torches (as many as five torches

have been used with some success) are employed. ...