Frequency-variant optical systems for signal analysis and processing

Coherent optical systems have been employed in many configurations for the spectral analysis of signal waveforms. With some systems, signal time-bandwidth products approach 10⁷, and real time or near real time analysis is now common. We describe here methods for obtaining frequency-variant time and frequency resolution with a coherent optical spectrum analyzer and for displaying signal spectral content vs. arbitrary functions of frequency. These methods greatly enhance the applicability of optical systems to specific spectral analysis problems, A constant proportional bandwidth-log frequency system is considered as an example. Applications to frequency-mapping signal processing are also discussed.