Blind symbol rate estimation using nonlinearity on sample correlation for digital coherent systems

We propose a symbol rate estimation technique by using absolute value of correlation of received signal for single-carrier polarization division multiplexed (PDM) systems in coherent detection system. We analytically show that spectrum of absolute value of correlation contains a peak indicating the symbol rate and has a robust performance which is insensitive to accumulated chromatic dispersion (CD) and first-order polarization-mode dispersion (PMD), amplified spontaneous emission (ASE) noise and laser frequency offset. Simulation result shows that this technique is applicable to long-haul application.