Monitoring technique for waveform distortion of 160 Gb/s signal by prescaled-clock tone detection using EA modulator

In order to monitor quality of ultra high bit-rate optical signals in a future optical network, such as 160 Gb/s, a simple monitoring technique is required. Therefore, a novel waveform monitoring technique by prescaled-clock tone detection was proposed in a previous report. In this paper, detailed principle of the proposed technique was explained. The monitoring technique is based on an asynchronous beat signal generation using an elecro-absorption modulator (EAM) and is able to separately observe waveform distortion caused by accumulated chromatic dispersion (CD), polarization mode dispersion (PMD) and optical signal-to-noise ratio (OSNR) degradation. The verification of concepts was performed by experiments, in which 1 GHz pre-scaled signals were employed to monitor distortion of OTDM 160 Gb/s carrier suppressed return-to-zero (CS-RZ) signals. Furthermore, applicability to Q factor estimation was verified by an experiment. In addition, an observation of 160 Gb/s signal by the proposed monitor was demonstrated over 120 minutes using an installed fiber in JGNII testbed.