An optical waveguide structure has a single port on one inputoutput side, a plurality of ports on another inputoutput side and an S-curve optical waveguide portion arranged on the outermost side of the waveguide structure and including a first circular arc optical waveguide portion and a second circular arc optical waveguide portion connected thereto. The belt is contained in a manner which causes structures on the belt to engage with exposed gear teeth of the ratchet wrench or an attachment. This design provides for increased accessibility and visibility within the gap defined between the cryostat enclosures, and allows for reduced amounts of superconducting material in the coils. The oxide layer has a plurality of bond defects. 50 to 150 phr of silica; 30 to 70 phr of processing oil; and 0.