Loss and reflectance of standard cylindrical-ferrule single-mode connectors modified by polishing a 10 degrees oblique endface angles

It is shown that the reflectance performance of existing, cylindrical, keyed, single-mode fiber connectors can be significantly improved by polishing 10 degrees oblique endfaces. This results in a maximum of -60 dB to less than -70 dB reflectance. Due to the resulting air gaps and hence multiple beam interference, the average insertion loss increase compared to physical-contact-type connectors is 0.43 dB. This is in excellent agreement with the predicted value of 0.45 dB for this type of joint. In cases where insertion loss performance is not the limited factor, this straightforward modification of standard cylindrical connectors shows potential for use in bidirectional and/or analog AM transmission systems. When the additional insertion loss cannot be tolerated, design changes in endface profiles and keying features may also be required. If fiber-to-fiber endface contact can be achieved, the same excellent reflectance performance will be achieved even with the presence of a modified index layer on the endface.<>