Fault analysis: optical performance investigation of fiber connections with imperfect physical contact.

We investigated the insertion and return losses of optical fiber connections with various air-filled gaps. Such gaps might occur when a fiber connection using physical contact unexpectedly fails, resulting in imperfect physical contact. The optical performance of these fiber connections depends on wavelength and gap size. We revealed that the measured optical performance of fiber connections with an imperfect physical contact, i.e., with an air-filled gap, might deteriorate to ∼18  dB for insertion loss and 9.4 dB for return loss at worst.