Metrology of complex optical modulation formats
Paper in proceedings, 2011
New modulation formats require sophisticated characterization equipment. Coherent optical signal analyzers are useful as they allow quantification of the hardware performance without the need for DSP and can serve as benchmark. Self-homodyne approach can serve as a benchmark for IF recovery algorithm evaluation. There is a need for both equivalent-time (high bandwidth) sampling and real-time burst sampling. Ideally, one would like real-time, high bandwidth sampling in a single instrument. Most of the transmitter impairments are found in the transitions, not at the center of the symbol/bit slot. When different transmitter and receiver impairments occur simultaneously, it is challenging to identify origin. There is still a lack of common testing standard for multi-level formats. Standardized repetitive sequences for noise averaging would simplify analysis and compliance testing.