Research And Design On Demultiplexer In All-optical OFDM Systems

With the explosive growth of the global transinformation, optical fiber communicationare moving toward the direction of ultra-high speed、ultra-large capacity and ultra-long haul(3U). Orthogonal frequency division multiplexing (OFDM) technology has become a hotresearch field by virtue of its high spectral efficiency and large dispersion tolerance.All-optical OFDM completes signal multiplexing and demultiplexing directly in the opticaldomain, which can effectively alleviate the electronic bottleneck limits of the transceiverwith a good prospect. This thesis focuses on the all-optical OFDM demultiplexing theory,research of the cascaded optical Fast Fourier Transform (OFFT) and reconfigurable opticalDiscrete Fourier Transform (ODFT) device have been extended. The main contents are asthe following:(1) Theoretical analysis of the ODFT structure realized by the cascaded MZ delayinterferometer and cascaded polarization interference unit have been listed respectively usingFFT algorithm from the optical transfer function. The key parameters affecting theperformance of those two cascaded devices are provided via numerical calculation.(2) A reconfigurable ODFT device is proposed, detailed structural design and numericalsimulation has been completed using the z-transform processing from the impulse responsetheory. The experiment results showed that the reconfigurable ODFT device could be able torealize arbitrary points and arbitrary frequency interval all-optical OFDM demultiplexing.(3) System simulation of all-optical OFDM systems based on the OFFT device andreconfigurable optical filter are conducted respectively. The influence of optical samplinggates, device performance, modulation formats as well as dispersion and nonlinear effectsfor the system transmission characteristics is investigated in detail. The results showed thatthe reconfigurable ODFT device could perform all-optical OFDM demultiplexing well and istransparent to modulation format、symbol width, which consistent with the performance ofthe cascaded MZ delay interferometer.