We previously developed an optical sampling oscilloscope (EDT-OSO) based on an envelope detection triggering method. This EDT-OSO can stably measure eye-diagram waveforms of signals exceeding 100Gbps without an external high-frequency clock signal. However far-end waveform measurements during a long distance place could not be realized. Because the EDT-OSO requires to link 10-MHz time bases in the EDT-OSO and a light under test (LUT) generator for synchrinizing.
To overcom this drawbak, we developed a direct bit-rate measureing method for synchronizing both 10-MHz time bases vartually and a self-synchronized EDT-OSO (SSEDT-OSO) based on this method simulteniously. We confirmed that a bit-rate measurement repetability of the SSEDT-OSO was from 10^-9 to 10^-8 by evaluating a standard deviation and the SSEDT-OSO could measure an eye-diagram without linking 10-MHz time bases.
This paper explains the basic principle for measuring the bit-rate of the LUT directly. Furthermore, we describe a configuration of the SSEDT-OSO and evalluation results.