In dual Mach-Zehnder interferometer (DMZI) system, polarization induced phase shift (PIPS) leads to a big location error. Traditional approaches adopt polarization controller (PC) to eliminate PIPS by controlling polarization state (PS) of light source. Through establishing the influence model of input light PS and equivalent polarization parameters of sensing cable on interference signals, an approach using a simplified polarization controller (PC) to obtain high location accuracy is proposed. The simplified PC is composed of a polarizer and a fiber-fused half-wave plate and can provide a linearly polarized light with azimuth angle controlled. Simulation and experiment indicate that the proposed method and PC design not only has capability of eliminating PIPS, but also has the benefits of low cost and easy control.
In this paper, the influences of fiber link and laser source on performances of Radio over Fiber (RoF) including error vector magnitude (EVM), constellation and eye diagram are investigated by simulation using Opti-system12 (trial version). The investigated RoF network is built on IEEE 802.16a WiMAX, with 16 QAM and a Mach-Zehnder modulator for intensity modulation. The mechanism of that the dispersion in fiber link makes the constellation rotate is investigated. The relationship between the rotation angle of the constellation and dispersion is analyzed, where we first put forward a fitting formula to describe this approximate quantitative relation. In the analysis of the influence of the laser source on the network, where the dispersion compensates fiber (DCF) is applied to compensate the rotation in constellation caused by fiber link, the threshold in the relationship curve of the linewidth and EVM is obtained. It is found that if the laser linewidth exceeds this threshold, the EVM will increase rapidly, then, the performance decreases.
A time-resolved optical imaging system is developed for "Qiangguang-I" generator to diagnose the early stage of wire
array Z-pinch. The optical imaging system is consisted by several independent modules. Each module includes a set of
object lens, an image intensifier, a set of relay lens and a CCD camera. The peak response of the system is at 439 nm.
The temporal resolution of the system is about 5ns, and the equivalent spatial resolution on the object plane is 6.5 lp/mm
when MTF=0.05. A series of images of 12mm diameter 32xΦ5μm tungsten wire array obtained by the system are shown
in this paper. We find that in the 32xΦ5 μm wire array experiments on "Qiangguang-I", from the implosion start to 60%
of implosion time, the behavior of single wire is dominant. The implosion time is (113±7) ns and the ratio of acceleration
time to implosion time ta/timp is about 0.60~0.75. The trailing mass distribution and the m=1 mode instability after the
stagnation phase are also observed in our experiments.
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