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High-order quadrature amplitude modulation (QAM) is a promising approach for increasing the spectral efficiency of wavelength-division-multiplexing transmission, but its optical implementation is still challenging. We propose a customized IQ modulator for generating 64-QAM using equal-amplitude electrical binary drive signals and verify the operation through simulations. Using the embedded VOAs, the transmitter can be finely controlled and flexible for several modulation formats. [ABSTRACT FROM AUTHOR]

A novel photonic crystal fiber (PCF) based on a four-hole unit is proposed in order to meet the requirements of high birefringence, negative dispersion and confinement loss in fiber-optic communication. The proposed design has been simulated based on the full vector finite element method (FVFEM) and anisotropic perfectly matched layers (APML). Analysis results show that the proposed PCF can achieve a high birefringence to the order of 10 −2 at the wavelength of 1.55 μm, a large negative dispersion over a wide wavelength range and confinement losses lower than 10 −9 dB/m simultaneously, which has important applications in polarization-maintaining (PM) fibers, single-polarization single-mode (SPSM) fibers, dispersion compensation fibers and so on. [ABSTRACT FROM AUTHOR]