A complex adaptive equalizer using a least-mean-square (LMS) algorithm is proposed to mitigate the effect of nonlinear interference induced by cross-phase modulation in wavelength-division multiplexing (WDM) coherent optical systems. We show the effect of nonlinear interference is equivalent to slow time-varying intersymbol interference. Simulations of dual-polarization 16 quadrature amplitude modulation (QAM) WDM systems are conducted to test the effectiveness of our proposed compensation method. The consequences show that significant improvement in system performance can be achieved by using the adaptive LMS equalization method.
Heterodyne method is used to monitor Brillouin gain spectrum in our slow light system. Accurate continuous Brillouin
gain spectrum is obtained and makes tunable laser accessible to adjusting wavelength of signal light into the spectrum
region. Maximum 32ns delay is achieved by 600MHz broadband Brillouin gain bandwidth.
Slow light is generated via the gain mechanisms of nonlinear optical phenomena-- stimulated stimulated Brillouin
scattering in optical fiber. Slow light is characterized in terms of Brillouin threshold, gain spectrum, Brillouin frequency
shift by using optical heterodyne detection. According to the measured Brillouin frequency shift, we set our signal
frequency in the gain region by manual matching method to get the maximum gain, and the gain bandwidth is broadened
to 450MHz using a phrase-modulated pump. A delay of 32ns is achieved for the 500ns input signal when the gain is
We proposed that nanomaterials can be used to change the characteristics of standard fibers. After two stages, preform
fabrication and fiber drawing, a novel inner cladding fiber with InP nano thin film has been successfully fabricated by
the means of MCVD. The thickness of the InP film is about 60nm. The electric field distribution is simulated through the
the finite element method. The simulation result indicates that the InP nano film can confine the electric distribution in
the core. In addition, it is calculated that the effective refractive index is 1.585.
We propose that nanomaterials can be used for fibers. A novel nano-InP doped fiber has been fabricated by the method of
modified chemical vapor deposition (MCVD).It has been measured that the doping concentration is 0.1%. The
relationship between refractive index and the wavelength is obtained by fitting experimental data to Sellmeier equation.
Dispersion of the fiber has been calculated in the wavelength range 1.2-1.6μm. As the wavelength varies from 1.2μm to
1.60μm, dispersion parameter D increases but is always negative. It has found that the dispersion of nano-InP doped
fibers is strongly changed compared to standard single-mode fibers, due to the nano-InP dopant which lead to a higher
refractive index difference.
As the key of these all optical techniques which would be widely used in the future optical fiber communication, the
stimulated Brillouin scattering (SBS) slow light draws a great of attention and shows several advantages over other slow
light methods. With recent growth of nano-technology, researchers are hoping to improve the nonlinearity of the optical
fiber by using the nano-technology. According to this current situation, a numerical model of the SBS slow light and
three typical experiments are discussed. A novel optical fiber doped with nano material as InP is manufactured and
introduced into the SBS slow light, serving as the nonlinear medium of SBS process. And the numerical simulations are
performed to validate our method. The results show a considerable time delay of the optical light can be achieved
through this novel optical fiber.
As the key of these optical devices which are widely used in the communication system, high nonlinear optical fibre
will play an important role in the future optical fibre communication. With recent growth of nano-technology,
researchers are hoping to obtain some kinds of optical fibre by combining the optical fibre with the nanotechnology.
According to this current situation, the optical fibre doped with nano-material as InP (indium
phosphide) is manufactured by using the MCVD (modified chemical vapor deposition) technology after our
comprehensive consideration of many relative factors. Proved by experiments, this novel optical fibre has an
excellent waveguide characteristic. After a consideration of the model of this novel optical fibre, its propagation
constant β has been simulated by using the FEM (finite element method), and the graphs of presentation
of magnetic field of the core are also obtained. In accordance with the results, the effective refractive index
neff = 1.401 has be calculated. Both the calculated result and the simulated graphs are matching well with the
test, and this result is a step-stone bridge for future research of nonlinear parameter on this novel optical fiber.
We develop a mathematical model of chirp in a Semiconductor Optical Amplifier (SOA)-based wavelength converters using cross-gain modulation (XGM).Using the model, we study numerically the effects that the chirp of Gaussian pluses and ultra-Gaussian pluses make into the optical signal pluses in Semiconductor Optical Amplifier (SOA), and theoretically analysis the parameters that affect chirp variations.
In this paper, the degradation of signal degree of polarization (DOP) by first and second order polarization mode dispersion (PMD) in 40Gb/s RZ and NRZ optical communication is analyzed by numerical simulation. The simulation results show that the degradation of signal DOP by first order PMD is monotony, but which is fluctuated by second order PMD. The influence of two components of second order PMD on DOP for NRZ code and RZ are also investigated by numerical simulation method. The results also show that the influence of the depolarization component and the PCD component on NRZ and RZ data formats are different. Those results will provide the theory basis for how to select proper compensation arithmetic. A compensation system is founded to compensate the first and high order PMD effectively by DOP as feedback signal and particle swarm optimizer (PSO) as compensation arithmetic. Here, we introduce an intelligent method PSO as a searching algorithm to multi-DOF (degree of freedom) PMD compensation, The PSO algorithm used here is described as: (1) Local neighborhood structure is employed to avoid being trapped into sub-optima. (2) 20 particles are employed. So 20 time units (less than 20 ms) are required in one iteration. (3) The maximum iteration number is set to 50. The experiment result show that the first and second PMD can be compensated at the same times for 10 Gb/s RZ and NRZ by using DOP as feedback signal and PSO as searching algorithm.