Junhe Zhou

Stable dynamic detection scheme for magnetostrictive fiber-optic interferometric sensors

A stable dynamic detection scheme for magnetostrictive fiber-optic interferometric sensors is studied. The working principle is presented and the experimental verification is performed. The results show that the system employing the dynamic detection scheme has better stability and sensitivity in comparison with the system employing quadrature control technique.

An approach to the bulk textured Fe81Ga19 rods with large magnetostriction

Bulk textured Fe81Ga19 alloy with large magnetostiction of up to 830ppm is fabricated using the technique of rapid directional solidification by triggering the undercooled Fe81Ga19 melts. The saturation magnetostriction is about two times as large as the maximum of the earlier report on Fe–Ga bulk samples. The large magnetostriction is ascribed to the high concentration of Ga–Ga atom pairs created by rapid solidification and their preferential orientation in the [100] textured rod.

Simultaneous demodulation and slow light of differential phase-shift keying signals using stimulated-Brillouin-scattering-based optical filtering in fiber

For the first time to our knowledge, we demonstrate simultaneous demodulation and slow-light delay of differential phase-shift keying (DPSK) signals at flexible bit rates using the stimulated-Brillouin-scattering-based optical filtering effect in optical fiber. Both 10 and 2.5 Gbit/s DPSK signals have been demodulated and delayed with excellent performances. In the case of the 10 Gbit/s DPSK signal, after demodulation the tunable delay range with error-free operation is about 50 ps, which we believe is the best result obtained for 10 Gbit/s slow-light demonstrations. For the 2.5 Gbit/s DPSK signal, the optimal sensitivity after demodulation is -36.5 dBm, which is comparable with the back-to-back sensitivity of a 2.5 Gbit/s nonreturn-to-zero signal.

Robust, compact, and flexible neural model for a fiber Raman amplifier

In this paper, a novel robust, compact, and flexible neural-network model for a fiber Raman amplifier (FRA) is presented. The model can be used in various applications with promising accuracy and low requirement for memory. Analytical expressions are derived in order to make the optimal pump-power configuration much easier, and the computational time is reduced dramatically in comparison with other gain-design methods in real-time pump-power adjustment. The calculated on-off gain spectrum and the noise figure using the proposed model agree well with the experimental results. The model has a potential value in simulation and pump-power dynamic control.

A New Frequency Model for Pump-to-Signal RIN Transfer in Brillouin Fiber Amplifiers

In this letter, we propose a novel frequency model to evaluate the pump-to-signal relative intensity noise (RIN) transfer in stimulated Brillouin scattering (SBS). For the first time, the RIN transfer in Brillouin fiber amplifiers has been numerically determined in the pump depletion regime both in the time and frequency domains. Moreover, an analytical expression of RIN transfer has been derived from the well-known SBS coupling equations when pump depletion is ignored. Experimental results are found to be in good agreement with the theoretical analysis.

Exact analytical solution for Raman fiber laser

In this letter, Raman fiber laser (RFL) is studied theoretically with experimental demonstration. With the assistance of the Lambert function, the coupled equations describing the optical power evolution in the RFLs are solved analytically. The procedures to get the analytical solution are described in detail. The results are verified by the numerical simulations and the experimental demonstrations.

Measuring electro-optic coefficients of poled polymers using fiber-optic Mach¿Zehnder interferometer

It is proposed and demonstrated that fiber-optic Mach–Zehnder interferometer measures accurately electro-optic coefficients of, not only poled polymer thin films, but also poled polymer waveguides. Furthermore, the tensor components, both r13 and r33, of electro-optic coefficient can be measured simultaneously.

Superheated liquid fragility and thermodynamic refinement for evaluation of metallic glass-forming ability

Based on the super-Arrhenius equation and Angell’s fragility concept [J. Non-Cryst. Solids 131, 13 (1991)], the expression of the fragility parameter for superheated liquid is deduced as M=E∞∕kBTl, where E∞ is the activation energy, kB the Boltzmann constant, and Tl the liquidus temperature. It exhibits a negative correlation with the glass-forming ability (GFA) of the referenced metallic glasses in the same system rather than in the different systems, while the parameter e based on order-disorder competition is just the opposite. The refined fragility parameter M* (=M∕e) gives a much better reflection of the GFA for the metallic glasses.

An analytical approach for gain optimization in multimode fiber Raman amplifiers

In this paper, an analytical approach is proposed to minimize the mode dependent gain as well as the wavelength dependent gain for the multimode fiber Raman amplifiers (MFRAs). It is shown that the optimal power integrals at the corresponding modes and wavelengths can be obtained by the non-negative least square method (NNLSM). The corresponding input pump powers can be calculated afterwards using the shooting method. It is demonstrated that if the power overlap integrals are not wavelength dependent, the optimization can be further simplified by decomposing the optimization problem into two sub optimization problems, i.e. the optimization of the gain ripple with respect to the modes, and with respect to the wavelengths. The optimization results closely match the ones in recent publications.

All-Optical Discrete Sine Transform and Discrete Cosine Transform Based on Multimode Interference Couplers

In this letter, a novel method to realize all-optical discrete sine transform (DST) and discrete cosine transform (DCT) is proposed. The approach requires only one multimode interference (MMI) coupler and several phase shifters at the input and output ports. By properly arranging the length of the MMI coupler and adjusting the phase shifters, the DST can be directly realized all-optically. Meanwhile, the DCT is related to the DST with a simple formula. By changing the input phase and relabeling the output ports, it can also be realized on the MMI structure. The proposed methodology has no limit on the number of the inputs.