Pre-form for and methods of forming a hollow-core slotted PBG optical fiber for an environmental sensor

A preform for forming a slotted photonic band-gap (PBG) optical fiber, comprising:

• a cylindrical cladding tube having a first central axis, a front end, a back end, an inner surface that defines an open interior, and an outer surface, the cladding tube having a first longitudinal slot formed in the outer surface through to the inner surface and having a front end and a back end;
• a cane having a second central axis, a PBG region arranged along the second central axis and having a hollow core substantially centered on the second central axis, and a solid outer region surrounding the PBG region and having an outer surface, the cane having a second longitudinal slot formed in the solid region outer surface;
• and
• wherein the cane is disposed within the cladding tube interior with the first and second central axes substantially aligned and with the first and longitudinal second slots substantially aligned.