One time division multiplexer based on half-reflective coating lens as beam splitter/combiner and fiber length to control relative time delay between two channels was demonstrated and experimentally studied in detail. This time-division multiplexer is a serial structure with four stages, and a pulse stream with sixteen times repetition rate can be achieved with the multiplexers. Its characteristics including polarization properties were experimentally studied in 16×10 Gb/s optical signal generation system.
The simple structure of a tunable polarization mode dispersion (PMD) compensator based on a cantilever beam and a high-birefringence linearly chirped fiber Bragg grating is proposed. A cantilever structure is used to introduce a linear strain gradient on the grating, and we can tune the compensated differential group delay (DGD) at a fixed signal wavelength just by changing the displacement at the free end of the beam. Based on numerical simulations, the performance of the cantilever structure as a PMD compensator is assessed for 10-Gbits/s nonreturn-to-zero transmission systems with a large DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal.
In this paper, we introduced a novel method to fabricate 40Gbit/s optical time division multiplexer by using PZT to modify the length of fiber, and investigated its polarization sensitivity. Optical fiber couplers were sensitive to polarization. Their coupling ratio changed with the fluctuation of polarization state, so the output power of multiplexer fluctuated. Polarization scrambler was adopted to reduce the polarization sensitivity of OTDM system for the first time and its validity was testified by the experiment.
We report on a 40 Gbit/s NRZ (non-return-to-zero) code transmission experiments including an dynamic Polarization mode dispersion (PMD) compensation. The dynamic PMD compensator is made up of two-stage four degrees. The first stage adopts polarization controller and fixed time-delayed line. The second stage is variable Differential Group Delay (DGD) element. The PMD monitoring technique is based on degree of polarization (DOP) as error signal. A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show that the performance of the PMD compensator is excellent for 40Gbits/s NRZ transmission systems with the large the DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal.
Dynamic programming, the ordinary adaptive compensation in the operational research, is used to resolve extremum of functions under the constraint condition. In this paper, it is introduced that, fundamentals, methods and steps about the first-order PMD compensation by dynamic programming. The result shows that, for the first-order PMD compensation, dynamic programming is used to carry out optimized design, and the result is satisfied. Beginning with recursive relation of PMD vectors in the fiber and the compensation devices, mathematical model of the first-order PMD compensation is established. Through optimized algorithm using dynamic programming, simulation and experiment for PMD adaptive compensation are both implemented. Some optimized algorithms once used in the PMD adaptive compensation have slow speed to approximate the optimal value and tends to become the local optimal solution; but if optimized algorithm using dynamic programming can approximate the global optimal solution directly. Therefore, it has the advantage of fast optimized speed. On this basis, the image of optimal solution is given and analyzed. PMD compensation scheme, based on PMD compensation vector, is proposed. The algorithm principle of adjusting control and the direction of improvement are also put forward. These results are benefit for dynamic adaptive compensation of PMD.