- Gap or space between the cable ends
- Core size mismatch
- Angular misalignment
- Numerical aperture mismatch (Correct)
As noted above, there are many potential causes of transmission loss or attenuation. When two cables are spliced together or joined with mated connection, several types of coupling loss can occur, such as:
- Core size mismatch: Occurs when the core of one cable is smaller/larger than the other.
- Numerical aperture loss: Occurs when the transmitting fiber core emits a larger cone of light than the receive fiber core can accept. This can occur even when the cores are exactly the same size and perfectly aligned.
- Angular misalignment: Happens when the cable ends aren’t completely flush, but one or both are tilted slight away from each other.
- Axis/Lateral misalignment: Occurs when the fiber cores are completely flush and the same size, but not aligned on the same central axis.
Gap or space between the cable ends: Occurs when a connector is not completely seated and a space exists between the two cable ends.