Agilent Quality Measures for Complex Modulated Signals Reaching for Standardization - Application Note 5991- free download

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Keysight Technologies Quality Measures for Complex Modulated Signals Reaching for Standardization Application Note Introduction The reputation of complex modulation is growing rapidly due to its successful use in optical transmission. It is becoming increasingly adopted, especially in the core networks, due to its superiority over traditional on-off-keying (OOK) in terms of bit transfer eficiency. Along with these new concepts, a new set of parameters for determining the quality of complex modulated signals and of standardized test conditions is also provided. But why should you get used to new test parameters and install new test setups if you can avoid it? Before you invest in this change, you will probably ask for the proof that any previously used method has severe limitations or even that it does not work. In some cases where a new quality parameter provides a clear advantage in both ease of use and the cost of test, standardization will follow what is already broadly accepted and implemented. In this application note, we analyze whether we need a new parameter to quantify complex modulated signal quality and, if so, consider the necessary steps to make this broadly accepted and standardized. 03 | Keysight | Quality Measures for Complex Modulated Signals Reaching for Standardization - Application Note Do we need a new quality parameter for complex modulated signals? In conventional OOK we only use one dimension to code the Figure 1 shows typical parameters that are derived from an information onto the carrier signal, represented by the eye-diagram of on-off keyed signals. In many cases, an estimate amplitude of the light. In complex modulation we typically add of the bit error ratio (BER) is derived from the noise distribution one more dimension on top of the amplitude -- the optical phase. during the ,1` and ,0` amplitude segments of the signal. Assuming The quadrature phase shift keying (QPSK) modulation scheme a Gaussian noise distribution, the Q-factor can be derived, which is a special case where information is coded only in the phase of is then directly related to the expected BER, based on statistical the carrier signal, but the signal is still usefully represented in rules. In addition, a hit ratio of the mask is often determined as two dimensions. (As dual polarization is more like an additional another parameter describing the quality of the signal or system. transmission channel than a 3rd modulation parameter, we do not Performance standards specify a limiting number of allowed hits need to consider this as a third dimension.) This two-dimensional of the mask. This mask is deined