Using fiber Bragg grating (FBG) as reflectors of the pump light, which could be made by using high power femtosecond pulse laser in the inner cladding of the DCF, shorter fiber is needed in optical fiber amplifiers, while maintaining at least the same performance as that without FBG. Based on the rate and propagation equations, numerical analysis of Er∶ Yb co-doped double cladding fiber amplifiers with and without FBG has been performed. The results show that amplifiers with FBG can reach the same output powers as those of without gratings, but only half-length of fibers are needed, either for forward or backward pumping. With FBG for backward pumping, the highest output power can be acquired for all cases, while using shorter fibers

A Talbot interferometer used for fabrication of fiber Bragg grating is analyzed in this paper. As the light ray tracing method can not give the actual intensity distribution of interference field when spatial coherence and temporal coherence of excimer laser are taken into account, electromagnetic theory is used for the detail description of the near interference field and far interference field, and a computation model is established, which considering the turning angle of mirrors as a model parameter for the first time. With the model, a series of simulations are carried out. From the results of calculations, we obtained a more actual status of interference field. The results showed that spatial coherence had a large influence on fringe visibility of both near and far field interference, and the far field was stricter with spatial coherence. The effect of turning angles of mirrors on far field interference cannot be negligible

The group delay characteristics of apodized, linearly chirped dual overwritten fiber Bragg gratings and their potential as dispersion compensators have been investigated. It is demonstrated that the group delay characteristics are affected significantly by period difference ΔΛ and different chirp parameter C. The results in this paper have implications on higher order fiber dispersion compensation and optical CDMA

The aberration characteristics and the conditions of the absence of various aberrations of the optical system of a two-lens null corrector and a single reflector are studied.A set of formulae are derived based on third-order aberration theory which are proved correct to be used in designing the initial structure of the optical system.The best choice for the structure and the single lens′ optical power of the corrector in a spherical reflector system is also investigated

A drive system for a 16-channel waveguide optical phased array beam deflector is presented, where the control unit for drive voltage regulation is implemented with a field programmable gate array (FPGA) chip. With the drive system, a beam scan rate above 580 kHz can be achieved, which is far higher than that obtained with other implementation methods based on microcontrollers