Gain-Flattened Optical Limiting Amplifier Modules for Wavelength Division Multiplexing Transmission

Crosstalk due to four-wave mixing (FWM) is increasing sharply when lightwave channel is upgrading in wavelength division multiplexing (WDM) fiber-optical communication systems. A technique, designed the channel wavelength allocation to reduce the crosstalks due to FWM, is submitted, when multi-channel is extended easily from 3-channel to 22-channel in WDM system. The result of simulation is presented. It is shown that suitable unequally channel separations can be found for which no FWM product term is superimposed on any of the transmitted channels, and the bandwidth expansion factor is not always increasing, and the span between the FWM crosstalks and channel wavelengths are not always decreasing, when increasing WDM system channels.

We propose and demonstrate a novel technique that uses a FabryPerot laser diode （FPLD） to perform simultaneous alloptical individual channel clock extraction and wavelength conversion. The nonlinear dynamical period1 oscillation can occur when a semiconductor laser is optically injected. By utilizing the crossgain modulation effect and the period1 oscillation harmonic frequencylocked in an optically injected semiconductor laser, we can extract the wavelength conversional individual channel optical clock from the opticaltimedivisionmultiplexing （OTDM） signal. In a FPLD, we numerically simulate the extraction of 20 GHz optical clock at 1550 nm from the 2×20 Gb/s OTDM signal at 1555 nm, and experimentally obtain the -105 dBc/Hz phase noise frequency division clock of 1236 GHz to 618 GHz with simultaneous wavelength conversion from 155024 nm to 154591 nm. Moreover, we investigate the influence of the injection optical power level, wavelength detuning, the FPLD's bias current level and the longitudinal mode selection on the optical clock extraction. This method is potential to technologically apply in the alloptical demultiplexing and wavelength routing in the OTDM mixed wavelengthdivisionmultiplexing （WDM） communication system.

In this paper, a simulation analysis of 40 Gb/s wavelength division multiplexing system of 32 channels is implemented through RZ modulation format by using a different hybrid fiber amplifier (HFA) configurations, namely, serial HFA, parallel HFA, and combined serial–parallel hybrid fiber amplifier (CSP-HFA). The performance of the proposed amplifiers is compared in terms of average gain level, average noise figure, flat gain bandwidth. In addition, quality factor, bit error rate, and eye diagram for the demonstrated 32 channel × 40 Gb/s wavelength division multiplexing optical communication system utilizing different configurations of the hybrid fiber amplifier is compared. The CSP-HFA shows better performance than serial and parallel hybrid amplifiers in terms of wider flat gain bandwidth, higher quality factor, lower bit error rate, and wider and clearer eye opening. Furthermore, CSP-HFA exhibits a flat gain bandwidth of 65 nm with an acceptable average gain of 16 dB and average noise figure of 7 dB.

Over 23.43 Gbps visible light communication system based on 9 V integrated RGBP LED modules

In this paper, a new design for a demultiplexer device for Wavelength Division Multiplexing (WDM) communication system is proposed. The proposed device consists of an inhomogeneous layer of a semiconductor material with refractive index that is graded according to a given profile. To minimize the size of the proposed device and achieve better spatial shift between the multiplexed wavelengths, several mirrors are placed at different locations inside the device. These mirrors will force the multiplexed light to be reflected before reaching the total internal reflection point. By controlling the different design parameters such as incident angle, the refractive index profile, etc., a small size, low cost and less complexity WDM device can be realized. In the design process, we exploits the ray’s spatial shift that results from the introduced mirrors and the material dispersion. In addition, the effect of the aforementioned design parameters on the amount of spatial shift between the adjacent wavelengths and the size of the device has been investigated. Results show that the proposed design achieves higher spatial shift as well as smaller device size in comparison with precedent WDM device designs.

A novel proposal for DWDM demultiplexer design using modified-T photonic crystal structure

In this paper, a high-speed tunable filter using optical polarization control module is proposed and experimentally demonstrated. The output spectrum of the filter and is obtained and high-speed tuning performance is demonstrated. The proposed filter is cost effective and simple; consisting of polarization controller (PC), polarizer(P) and polarization maintaining fiber (PMF). To testify the high speed tuning effect, the eye diagram and ON/OFF switching performance are measured. Experimental results revealed that the proposed filter is a good candidate to be applied in wavelength-division multiplexing (WDM) communication systems.

A defected core decagonal photonic crystal fiber is designed and numerically optimized to obtain its residual chromatic dispersion compensation in the wavelength range of 1460 to 1675 nm i.e., over S+C+L+U wavelength bands having an average dispersion of about −390 ps/(nm km) with a dispersion variation of 7 ps/(nm km). The designed fiber, with a flattened dispersion profile, has four rings of holes in the cladding region, which results in low confinement loss and small effective mode area at wavelength 1550 nm. For residual chromatic dispersion compensation, the proposed fiber can be used in wavelength division multiplexing optical fiber data communication systems.

We have developed a 1.55 µm superluminescent light-emitting diode (SLD) with a tapered active region. We achieved high power and broadband operation demonstrating an output power of 330 mW under cw operation at 7°C. We examined the beam profile of output light by measuring its near field and far field patterns. It was found that the output light shows a fundamental transversal mode profile in both horizontal and vertical directions. This device will be applicable to spectrum-sliced multiwavelength light sources for use in wavelength division multiplexing optical communication systems as well as in lightwave sensing.

We propose a broadband tunable negative dispersion photonic crystal fiber (BT-ND-PCF) for dispersion compensation over the S + C + L wavelength bands. BT-ND-PCF is a dual-core structure in which air holes are arranged with a hexagonal lattice and temperature-sensitive liquid is infiltrated into the air holes of the fourth layer. The performance of BT-ND-PCF is numerically analyzed by the finite element method with an anisotropic perfect matching layer. The results show that BT-ND-PCF has a broadband negative dispersion coefficient of −1533.2 to −2836.4 ps / km / nm over the S + C + L wavelength bands, a dispersion coefficient of −2268.9 ps / km / nm at 1550 nm, and a kappa value of 287.9 nm at 1550 nm, which matches with Corning single-mode fiber 28 (SMF). The residual dispersion (RD) after compensating for the dispersion of 1 km SMF is in the range of −0.22 to +0.16 ps / nm. In addition, the dispersion coefficient is changed by 0.679 ps/km/nm per 1°C by controlling the temperature, which is conducive to the accurate compensation of RD. Due to its unique optical properties, BT-ND-PCF can be used in broadband dispersion compensation for dense wavelength division multiplexing optical fiber communication systems.

We study the information capacity for an multi-span optical fiber transmission system with losses, dispersion, nonlinearity and amplified spontaneous emission (ASE) noise. A perturbation technique is developed to examine the information capacity, and a semi-analytic expression of the conditional probability distribution function is determined initially. A novel semi-analytical form of the information capacity was obtained, which can be extended to the wavelength division multiplexing (WDM) optical fiber communication systems. Computer simulations are executed for various parameters of the transmission system. The studied results indicate that the capacity does not monotone increase with the input power and is affected by the nonlinear coefficient prominently.

We have proposed a three-port high efficient channel-drop filter (CDF) with a coupled cavity-based wavelength-selective reflector, which can be used in wavelength division multiplexing (WDM) optical communication systems. The coupling mode theory (CMT) is employed to drive the necessary conditions for achieving 100% drop efficiency. The finite-difference time-domain (FDTD) simulation results of proposed CDF which is implemented in two dimensional photonic crystals (2D-PC), show that the analysis is valid. In the designed CDF, the drop efficiency larger than 0.95% and the spectral line-width 0.78 nm at the center wavelength 1550 nm have been achieved.

A novel multi-granularity flexible-grid switching optical-node architecture is proposed in this paper. In our system, the photonic lanterns are used as mode division multiplexing/demultiplexing (MD-Mux/MD-Demux) for selecting mode. The wavelength division multiplexer/demultiplexer (WD-Mux/WD-Demux) and the fiber bragg gratings (FBGs) are used to select wavelength channels with the various grid. The experimental results show that the transmission bandwidth covers the C+L band, the average transmission loss is −13.4 dB, and the average crosstalk is −30.5 dB. The optical-node architecture is suit for mode division multiplexing (MDM) optical communication system.

Development of an OADM to reduce the incoherent crosstalk in WDM system

A simple theory for the crosstalk in multichannel wavelength-division multiplexing (WDM) communication systems caused by the cross gain saturation in semiconductor optical amplifier (SOA) is developed. It is shown that increasing the carrier recombination lifetime while reducing the differential gain in the SOA greatly mitigates the crosstalk. An SOA using type-II quantum wells with reduced recombination probability is designed, and its characteristics are numerically modeled for a number of different WDM systems. It is shown that when used as a preamplifier or in local/metro networks with a small number of amplifiers, error-free transmission can be achieved with the type-II SOA.