We have experimentally demonstrated what to our knowledge is a novel framing-recognition and performance-monitoring scheme for the synchronous optical network (SONET) using the radio-frequency spectral analysis and taking advantage of the intrinsic data structure of the SONET signal itself. This scheme does not require access to individual bits or recovered clock and data. It can recognize SONET frame-alignment sequences and generate framing pulses correspondingly. It also provides an analog indicator that varies monotonically with the in-band signal-to-noise ratio and hence the channel bit error rate. In principle the proposed scheme can be scaled to data rates of OC-192 and higher.
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