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.
Presented principle of PSW is based on rate-equation model in the SOA.
The TE and TM modes experience different refractive indexes, which lead to phase difference between the two modes,
then they interfere at the output of the SOA, and the switching effect is obtained. The rate-equation model is effective in
describing the switching effect. But in experiments, this model is hard to realise and track on line, and there are many
difficulties for achieving the switching effect.
In the SOA, there are four nonlinear effects: cross-gain modulation, cross-phase modulation, cross-polarization
modulation, and four-wave mixing. These nonlinear effects are widely researched in optical devices. Several models that
describe the nonlinear effects had been presented. Moreover, these models are microscopic models that describe the
SOA carrier dynamics, and in many experimental setups, SOAs are pigtailed with standard signal mode fibers at input
and output. But the changes of polarization state in the pigtail fiber remain unnoticed. In this paper, we present a
macroscopic model of SOA that includes pigtailed fiber and SOA. In this model, we use principal states of polarizations
(PSP) to analyse the nonlinear polarization rotation. The PSPs are defined as those output SOPs that remain unchanged
to the first order approximation, when the parameter, such as bias current or power of optical control pulse, is adjusted.
Our model is a more practical design tool for optical switching configuration. We develop a theoretical relationship
between the polarization rotation and the bias current of the SOA. Then, the nonlinear polarization switching is
demonstrated. Compared with the reported Optical switching that based on rate-equation model, this switching is stable
and easier to be realised.
In section II, we present the model based on the principal states of polarizations (PSP). Experimental results show
that this model can explain the nonlinear polarization rotation in SOA. In section III, we demonstrate the polarization
switching use polarization rotation. We find an excellent agreement between our model and experimental results. We
conclude our paper by summarizing important finding in section IV.
The measurement of magneto-optical effects in the fiber core absorption is powerful tool in a number of applications. The polarimetry rotatory angle measurement play a key role in these applications, especially in the case with a tiny rotatory angle. With Faraday magneto-optical modulator of Tb3Ga5O12 and the polarizer controlled by step-motor, the accurate measurement is improved of tiny rotation angle of the linearly polarized light. The development is reported here.
Full characterization of the sensitivity of the LPFG is a precursor to practical device design, and knowledge of the sensitivity of the Long-period fiber gratings to the parameters of its physical environment processed is clearly important. We present a theoretical and experimental investigation into the sensitivity of long-period fiber gratings as a function of processed parameters by high-frequency CO2 laser pulses.
A theoretically and experimentally analysis was presented of ultrasonic wave generation in water by intensity modulated elliptical Gaussian laser beams. It was found that generated acoustic radiation is highly directional both in polar and azimuthally directions. Experimental results showed that over the frequency range of 5 to 20 kHz, there was an almost flat response with an average normalized phase sensitivity of -300 dB re 1/μPa and an average pressure sensitivity of -150.0 dB re rad/μPa. These results indicate that the present design offers the possibility of getting highly directional sound beams in a simple configuration.
A new and simple method was developed for accurate measurement of Faraday rotation in materials with low rotation using Faraday magneto-optical modulator. A rode of glass with a large Verdet constant is used for this measurement. The rotatory angle can take values in the magnitude of sub-millidegree (10-4 degrees). Detailed theoretical and experimental analysis was given.
THe emission spectrum of Xe2+Cl- in HCl plus Xe doped crystalline CO, excited by 308 nm laser, are firstly observed. The cooperative charge transfer absorptions: HCl plus Xe plus 2 hv yields [Xe+(HCL)-] is demonstrated, and the four-body, two-photon cooperative absorption cross section at 308 nm is 5 multiplied by 10-42 cm4s.
In our work, the design and performance of a new kind TEA CO2 laser is reported. It was preionized by ultraviolet (UV) from surface corona discharge. A BN ceramic structure was employed as an assembly of resonators. The output energy of 143 mJ, the pulse duration of 50 ns, the transverse mode of TEM00, the repetition-rate of 50 Hz, the divergence of only 4 mrad was obtained. Comparing with UV bare-spark- preionized (BSP) TEA CO2 lasers, it was found that (1) the uniform of the main electrode discharge was improved, (2) the repetition-rate was improved from 30 Hz to 50 Hz, (3) the input energy was four times lower than that of BSP TEA CO2 laser under the same output energy, (4) the lifetime reached 106 pulse, (5) the stability of resonator was improved, the output energy eliminated only 14% after 3.5 hours operation. The performance was improved because the intrinsic efficiency of surface corona preionization was four times higher than that of BSP one, the corona discharge was very uniform and photodissociation processes involved in BSP were avoided. The extremely low thermal-expansion of BN minimized the misalignment, so the high reliability can be obtained.