Coherent photonic time stretch for ultrafast spectrum measurement

The paper presents an ultrafast spectrum measurement method based on photonic time stretching technology. The working principle of the photonic time stretch enhanced recording scheme is discussed. This scheme, based on the direct detection, have disadvantages such as loss of information about the phase of the modulated signal, high harmonic distortions due to the non-linear characteristic of the output signal due to the squaring of the electric field by photodetector. To avoid these disadvantages, the coherent photonic time stretch enhanced recording scheme is discussed. Further, this time stretching technology was designed in the VPIphotonics Design Suite software environment. Finally, based on the simulation, a graph of measurement error was constructed. The maximum error of the scheme is 180 MHz at the frequency before 5 GHz. After 5 GHz, the frequency measurement error less than 100 MHz and after 10 GHz, the frequency measurement error does not exceed 50 MHz.