Abstract

Bit error rate (BER) is a statistical quantity. To measure BER with confidence, enough number of errors must be collected over a time interval. When the BER of the incoming signal is time-varying, the measurement accuracy degrades since the intervals with a high BER dominate over the ones with a low BER. However, when the BER of a signal is both time-varying and periodic, we can use a sampling technique to make a time-resolved measurement of BER—we vary the time delay in the gating pulse to map out the time evolution of the BER as shown in Fig. 1(a). Likewise, the optical signal-to-noise ratio (OSNR) of the signal can be resolved in time as well. This measurement method is useful for characterizing burst errors in networks that are caused by transient loading effects such as channel add/drop. In addition, the effectiveness of amplifier gain and transient control in such a dynamic environment can be studied in more detail. Similar techniques can be found in the field of femtochemistry, where ultrafast femtosecond (10⁻¹⁵ s) chemical reactions are too fast to be captured directly by a slow detector. Using an optical pump-probe technique, a fast event can be measured by a slow instrument (for example, a lock-in amplifier). To improve the measurement’s temporal resolution, we can characterize the gating pulse and perform a deconvolution process.

© 2002 Optical Society of America