Pulse Shape Recovery
Optimization of Dispersion compensation
All this is made possible by complete optical phase recovery. Conventional detectors only give you half the story. For example, a 40Gb/s pulse stream remains unchanged on a oscilloscope display as the modulator bias voltage is adjusted, but the SP Pulse Analyzer shows the change in frequency chirp, allowing complete optimization.
The figure on the right shows the output of an externally modulated 40Gb/s pulse stream using a traditional fast detector and oscilloscope. The pulses appear as a 40GHz sine wave, thus giving no real feedback to whether the modulator is correctly biased, or if any residual chirp exists on the pulses.
With the SP Pulse Analyzer, however, the pulse shape and phase are measured, allowing the bias and modulation depth to be optimized, and any chirp characterized. The graph to the right shows a typical recovery of a 2ps pulse, where pulse amplitude is shown in blue and phase shown in green. As can be seen there is a quadratic phase profile across the pulse.