Theoretical investigation of pilot allocation for pilot-aided phase channel estimation in optical-orthogonal frequency division multiplexed fiber system

In this paper, we show a novel pilot-aided phase channel estimation approach based on theoretical relation between chromatic dispersion and coherence bandwidth, for pilots allocation in an symbol multiplexed by orthogonal frequency division multiplexing and transmitted to optical fiber system. The method is implemented on Matlab® to make a linear interpolation between adjacent pilot carriers, which are separated by data, in the symbol. Our simulations use an optical bandwidth of 12.5 GHz and Fast Fourier Transform size of 128 to establish the number of pilots for having error free and suitable channel estimation for a fiber length up to 1000 km. In our simulations, we took into account the parameters of a standard single-mode fiber. We calculate the minimum number of pilot carriers for a suitable pilot-aided channel estimation based on the analysis of the symbol position in the constellation diagrams for QPSK and 16-PSK signals, which should be limited to a decision area. We show that the minimum number of pilots for suitable channel estimation is lower than the number of pilots for channel estimation with error free.