Abstract

Optical time-domain reflectometry (OTDR) has recently become a popular technique lor locating breaks and measuring return/transmission losses along optical-fiber links. However, as the length of the link becomes longer owing to the installation of erbium-doped liber amplifiers (EDFAs), the dynamic range of a conventional OTDR must be increased correspondingly. The dynamic range of a conventional single-pulse OTDR can be maximized by increasing the peak power or the duration of the probe pulse, by reducing the receiver noise, or by using digital signal-processing techniques. In order to increase the peak power of a probe pulse and the sensitivity of a receiver, an EDFA can possibly be used simultaneously as a power amplifier and a preamplifier for the OTDR.¹ This appears to be an attractive approach because the OTDR and the EDFA can be integrated into a single measurement unit. EDFAs can also be used as in-line amplifiers to enhance the dynamic range of an OTDR.² In this paper, however, we point out a fundamental problem with using a conventional OTDR together with a saturated power or in-line EDFA.

© 1994 Optical Society of America