Quantifying end-face quality of cleaved fibers: Femtosecond laser versus mechanical scribing

Abstract

A femtosecond laser-based scribing procedure has been investigated for cleaving silica optical fiber. As a proof of concept, SMF 28 fiber was scribed by 1030 nm femtosecond laser pulses at 10 kHz and then placed under tension to initiate cleaving. The resulting end faces were measured using a noncontact optical interferometer, but the subsequent analysis identified deficiencies in the conventional “cleave angle” parameter. This was partly due to the difficulty of aligning the longitudinal axis of the fiber with the optical axis of the optical profilometer, but also because the end faces generally did not resemble a simple tilted plane. As an alternative metric, we therefore evaluated the probability density function of the local tilts over the central portion of the cleaved end faces (0.9 fraction of the fiber radius) after subtracting the global best fit plane. This provided a median tilt value of 0.17° for laser scribing and 0.55° for mechanical scribing (averaged over five samples of each). The laser-scribed fibers had a total height variation of 12 µm versus 17 µm for the mechanically-scribed fibers, and they were free of rounding and melting around the edges. Thus the cleaved end face produced by femtosecond laser scribing has superior quality in terms of flatness, smoothness and symmetry compared to mechanical scribing. The technique also has important potential advantages compared to laser cleaving based on CO2 lasers, where the glass is machined by melting. With further development of the technique, it has the potential to be used for automated cleaving of specialty fibers and multi fiber arrays with comparable cleave quality.