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Summary For high‐precision timing synchronization in feedback Gardner algorithm and different feedforward nonlinear algorithms, timing jitter reduction is the key problem, especially with a small roll‐off factor in high‐order modulation. Through the elaborate analysis about the timing jitter, this paper proposes a new prefilter design method based on finite impulse response structure. Using a suitable Kaiser window for suppressing the sidelobe energy of the proposed prefilter, this method can further decrease the complexity of filter design and eliminate most part of the pattern noise. Compared with the previous prefilter design algorithms, the approach has a better improvement in steady‐state phase jitter reduction without increasing the capture time in Gardner timing error detector. Meanwhile, with such kind of prefilter, the performance of logarithmic nonlinearity is better than that of square law nonlinearity, this is not reported in literature. Simulation results show that the residual timing jitter in both kinds of algorithms is closed to the modified Cramer‐Rao bound when the roll‐off factor is equal to 0.1 in 1024QAM.

Microchip lasers are applied as the light sources on various occasions with the end-pumping scheme. However, the vibration, the temperature drift, or the mechanical deformation of the pumping light in laser diodes in the end-pumping scheme will lead to instability in the microchip laser output, which causes errors and malfunctioning in the optic systems. In this paper, the side-pumping scheme is applied for improving the disturbance-resisting ability of the microchip laser. The transverse mode and the frequency purity of the laser output are tested. To ensure unicity in the frequency of the laser output, numerical simulations based on Fresnel-Kirchhoff diffraction theory are conducted on the parameters of the microchip laser cavity. Film-etching technique is applied to restrain the area of the film and form the microcavity mirrors. The laser output with microcavity mirrors is ensured to be in single frequency and with good beam quality, which is significant in the applications of microchip lasers as the light sources in optical systems.

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