In telecommunications, the term ovality has the following meanings:

1. The attribute of an optical fiber, the cross section of the core or cladding of which deviates from a perfect circle.

2. In an optical fiber, the degree of deviation, from perfect circularity, of the cross section of the core or cladding.

Note 1: The cross sections of the core and cladding are assumed to first approximation to be elliptical. Quantitatively, the ovality of either the core or cladding is expressed as 2(a-b )/(a +b ), where a is the length of the major axis and b is the length of the minor axis. The dimensionless quantity so obtained may be multiplied by 100 to express ovality as a percentage.

Note 2: Alternatively, ovality of the core or cladding may be expressed or specified by a tolerance field consisting of two concentric circles, within which the cross section boundaries must lie. Synonym noncircularity.

Source: from Federal Standard 1037C