How much does a cleave angle greater than 1 degree affect splice loss?
A cleave angle greater than 1 degree will significantly increase splice loss. For single-mode fibers, even a small angular misalignment can lead to substantial loss due to the precise alignment required for efficient light transmission.
Typically, an ideal cleave angle is 0 degrees, and most fusion splicers are designed to work optimally with cleave angles less than 0.5 degrees. When the cleave angle exceeds 1 degree:
- Increased Fresnel Reflection: A non-perpendicular end-face causes more light to be reflected back at the splice point, rather than transmitted through.
- Reduced Mode Field Diameter Overlap: The angled faces lead to a geometric offset between the fiber cores, reducing the overlap of the mode field diameters and thus decreasing coupling efficiency.
- Angular Misalignment: The primary source of loss from an angled cleave is the angular misalignment it introduces, which causes light to diverge rather than couple cleanly into the receiving fiber.
While the exact splice loss can be calculated using specific formulas involving the fiber’s numerical aperture and core diameter, a general guideline is that splice loss increases exponentially with increasing cleave angle. For angles exceeding 1 degree, splice loss can easily be in the range of several tenths of a decibel (dB) or even higher, which is often unacceptable for many optical link budgets.