:: What is a fiber optic cleaver?
A fiber optic cleaver is a piece of tool or equipment to make an almost perfect fiber end face cut. Just like using a diamond scribe tool when cutting glass, a fiber cleaver’s cutting wheel (blade) makes a very tiny cut on the fiber first, then the fiber is pressed against the little cut to force it to break at 90° angle and expose a mirror like fiber end face.
:: Why do we need to cleave optical fibers?
Optical fiber needs to be cleaved for fusion splicing. Optical fiber fusion splicing nearly always requires that the fiber tips exhibit a smooth end face that is perpendicular to the fiber axis.
This sufficiently perpendicular and planar fiber end face can be achieved via the fiber cleaving process. In this cleaving process, the brittle glass fiber is fractured in a controlled manner.
Polishing a fiber tip can result in even higher quality fiber end faces, but polishing requires more expensive equipment and more processing time, so it is very rarely employed for fusion splicing.
:: Fiber optic cleaver designs
An optical fiber is cleaved by applying a sufficient high tensile stress in the vicinity of a sufficiently large surface crack, which then rapidly expands across the fiber cross section at the sonic velocity.
This idea has many different practical implementations in a variety of commercial cleaving equipment. Some cleavers apply a tensile stress to the fiber while scratching the fiber’s surface with a very hard scribing tool, usually a diamond edge.
Other designs scratch the fiber surface first, and then apply tensile stress. Some cleavers apply a tensile stress that is uniform across the fiber cross section while others bend the fiber through a tight radius, producing high tensile stresses on the outside of the bend.
Commercial instruments for simultaneously cleaving all the fibers in a ribbon fiber are also widely available. These ribbon fiber cleavers operate on the same principles as single fiber cleavers. The average cleave quality of a ribbon cleaver is somewhat interior to that of a single fiber cleaver.
Scribe-and-break cleaving can be done by hand or by tools that range from relatively inexpensive hand tools to elaborate automated bench tools. Any technique or tools is capable of good cleaves; the trick is consistent finishes time and time again.
In general, the less costly approaches require more skill and training for the technicians making the cleave.
:: Types of fiber cleavers
Most modern fiber cleavers are suitable for precision cleaving of all common single silica glass fibers, even under harsh on-side conditions. Special cleaver designs for applications in research, measurement technology and production of optical components are available.
:: The importance of cleave quality
The impact of cleave quality on the quality of the resulting fusion splice should not be underestimated. Deficiencies in a fiber cleave are one of the most common causes for geometric deformation in the resulting splice, which are particularly onerous for single mode fiber.
Much of the variation in splice loss observed between different splices fabricated using the same splice parameters is due to variation in cleave quality.
There are several ways in which a poor cleave can reduce the quality of the resulting splice. It can compromise the performance of image processing routines that perform fiber alignment. Cracks in the fiber’s end face can lead to a bubbles at the splice joint, which usually requires the splice to be remade.
:: Fiber Cleaver features:
Most high precision cleavers produce a cleave angle deviation typically <0.5° with very high reliability and low scattering under on-side conditions.
One-step cleaving operation are a reality now with cleavers. Fiber clamping, bending, scratching and cleaving with one single action.
Diamond blade presents the highest cleave quality and can last over 10,000 cleaves. They are even adjustable for cleaving fibers with increased tensile strength, e.g. titanium-coated fibers.
It is easy to cleave an 80um diameter fiber, possible to cleave a 125um diameter fiber, and usually difficult to cleave >200um fibers. To some extent, the difficulty in cleaving these fibers results from the fact that the material of the fiber is not crystalline. Again, torsion will produce a non perpendicular endface. In face, most commercially available angle cleavers rely on torsion. The endface angle is proportional to the amount of torsion.