Hollow core optical fiber preform with seal and method of manufacturing hollow core optical fiber therefrom

A method of manufacturing a hollow core optical fiber comprising:

• a drawing step comprising drawing a hollow core optical fiber from a hollow core optical fiber preform comprising:
• a preform longitudinal axis extending between a preform first end and a preform second end;
• a cladding tube comprising (i) a cladding glass composition exhibiting a cladding coefficient of thermal expansion, (ii) a cladding interior through which the preform longitudinal axis extends, (iii) a cladding first end proximate the preform first end, (iv) a cladding second end proximate the preform second end, and (v) a cladding opening at the cladding first end;
• one or more capillary tubes disposed within the cladding interior and around the preform longitudinal axis, each of the one or capillary tubes comprising (i) a capillary glass composition exhibiting a capillary coefficient of thermal expansion, (ii) a capillary longitudinal axis that is parallel to the preform longitudinal axis, (iii) a capillary interior through which the capillary longitudinal axis extends, (iv) a capillary first end proximate the preform first end, (v) a capillary second end proximate the preform second end, (vi) a capillary opening at the capillary first end, and (vii) a capillary outer surface at a capillary outer radius from the capillary longitudinal axis;
• an effective core region through which the preform longitudinal axis extends, the effective core region comprising a core radius from the preform longitudinal axis that is tangential to the capillary outer surface of each of the one or more capillary tubes;
• a seal at least partially sealing one or more of the cladding opening and the capillary opening of each or some of the one or more capillary tubes, the seal comprising a seal glass composition exhibiting a seal coefficient of thermal expansion, the seal coefficient of thermal expansion within ±10% of the cladding coefficient of thermal expansion or the capillary coefficient of thermal expansion;
• and
• one or more metal tubes extending through the seal, each of the one or more metal tubes comprising (i) a first tube end disposed within the cladding interior, (ii) a second tube end dispose outside of the cladding interior, and (iii) an outer surface at least partially facing the seal,
• wherein, (i) the seal at least partially seals the cladding opening, and the first tube end of at least one of the one or more metal tubes is disposed within the cladding interior and outside of the capillary interior of all of the one or more capillaries, (ii) the seal at least partially seals the capillary opening of each or some of the one or more capillaries, and, the capillary interior of the at least partially sealed ones of the one or more capillaries receives a second end of a different one of the one or more metal tubes, or (iii) both (i) and (ii).