Monia Najjar

Slow light optimization in symmetric photonic crystal waveguide with elliptical holes

In this paper, we propose a slow light structure formed by circular and elliptic air hole where the innermost two rows on each side of the waveguide is shifted vertically. By adjusting radii of shifted holes, we obtained a large value of Normalized Delay Bandwidth Product (NDBP) about 0.42, group index of 50 and ratio normalized bandwidth/normalized central frequency of 0.0084.

Slow-Light Enhanced Second Harmonic Generation in Lithium Niobate Photonic Crystal Waveguides

In this research study, we propose a slow-light-based photonic crystal waveguide consisting of a combination of circular and elliptic airholes with a background material of lithium niobate LiNbO3 (refractive index n = 2.211). By modifying the radii of the closest row to the waveguide in each side, we demonstrate a high value of normalized delay-bandwidth product, equal to 0.60. Using finite-difference time-domain method (FDTD), a significant increase of second harmonic generation efficiency of about 0.14 at a moderate power is observed when analyzing the nonlinear performance of the designed slow-light structure.

Simulation and Modelization of Multimode Interference Demultiplexer by using BPM Method

Optical switches based on planar lightwave technology offer stable and robust means of achieving space- division switching. One form of integrated switch that shows some promise is the generalized Mach-Zehnder optical switch. This switch normally comprises two multimode interference (MMI) couplers connected by an array of phase shiffers. We show through detailed simulations that the length of conventionally designed multimode-interference couplers. A 1310 and 1550 nm coarse wavelength multi/demultiplexer based on polymer is demonstrated for the first time. The device is designed based on a combination of general interference and paired interference mechanisms of multimode interference (MMI). Short tuning of the device makes it possible to fabricate MMI coupler with larger free spectral range, significantly increases the 3-dB bandwidth for the total transmittance. By the structure improvement by S-curve we increase the normalized output power of the field for A=1310 nm from 0.8 to 0.95.

Performance study of high bit rate indoor wireless optical networks

In this paper, we propose a high bit rate system by using a LASER diode in wireless optical communication technique. Two applications are studied, the home network and local area network. For the different applications, the quality of transmission depends on the system parameters that must be selected by precision. From numerical simulation results, it is confirmed that as the bit rate increase as the system parameters selection becomes more critical. The lasers used in these systems have a high power output and good directivity which minimize the loss of the link in comparison with the classical emitters utilized in the infrared wireless optical communication links. Our system can give a good quality of transmission with a bit rate until 40 Gbit/s.

Performance analysis of a 2 Tb/s DWDM system based on narrow channel spacing and multi-diagonal code

Wavelength division multiplexing is used to design and to realize multi-channel optical communication systems to meet the growing demand for bandwidth. Dense wavelength division multiplexing (DWDM) technique, characterized by channel spacing equals or less than 0.8 nm or the use of more than 16 channels, offers the full use of the fiber bandwidth. Therefore, it is the perfect means of network enlargement. In this paper, we design a DWDM system with 100 channels each 20 Gbps data rate multiplexed with channel spacing of 0.2nm and using the multi-diagonal (MD) code: a new family of SAC-OCDMA codes. The system performance is optimized by using two different dispersion compensation techniques: Dispersion compensation fiber and fiber Bragg grating.

Optimization of WDM demultiplexer based on photonic crystal

In this paper, two-dimension band pass filters are proposed to design CWDM de-multiplexer which permit to separate two telecom wavelengths (1.31 μm and 1.55 μm). The square lattice with TE mode are adapted to designed the proposed de-multiplexer with help Photonic Band Gap (PBG). The structure has been designed using silicon rods, refractive index 3.45, which are embedded in air. The Plane Wave Expansion (PWE) method and 2D Finite Difference Time Domain (FDTD) method are employed to calculate the PBG range and output spectra of the filter. The localization property of photonic crystal has been used to guide the wavelengths in two different output with high transmission.

Conception and Simulation of Wavelength Demultiplexer for C and L Bands based on MMI Structure

The self-imaging property of a homogeneous multimode planer optical waveguide has been applied in this paper in the design of passive planer demultiplexer based on multimode interference (MMI). The modeling is used to arrive at the simulation of the demultiplexer operating at 1565 nm-1530 nm in polymer as a core materiel and BK7 as a cladding with an insertion loss of 1.1 dB and 1.7, respectively, for a 12.4 mm long device. In addition a device with a cross-power ratio smaller than 18.75 dB has also achieved. All results are simulated in two dimensions beam propagation method (2D-BM).

Concave Rectangle Photonic Crystal Ring Resonator for Ultra-Fast All-Optical Modulation

Abstract In this paper, an ultra-fast all-optical modulator, based on a new shape of nonlinear photonic crystal ring resonator, is designed and studied. Numerical methods such as plane wave expansion (PWE) and finite-difference time domain (FDTD) are used to perform simulations. The modulation technique consists of carrier light controlling by means of input light signal and Kerr effect. The investigation of extinction ratio and insertion loss within the carrier input power shows that the choice of 0.7 W is the optimal value of that power to ensure the tradeoff between both characteristics. The suggested modulator demonstrates an excellent extinction ratio about 20.8018, a very low insertion loss of −13.98 and a short switching time about 13.4 ps. According to the obtained results, the modulator can be considered as an ultra-fast and ultra-compact optical component.

Design and analysis of a 2Tb/s UDWDM system based on the combination of advanced modulation techniques and multi-diagonal code

In this paper, an optical Ultra Dense Wavelength Division Multiplexing (UDWDM) system based on the combination of advanced modulation formats and multi-diagonal code with an ultra high transmission capacity of 2 Tb/s using different modulation formats is developed; 100 channels with channel spacing of 0.4 nm and 0.2 nm are studied in order to find the optimum modulation format for a high bit rate optical transmission system. The effect of channel spacing variation is observed in terms of bit error rate for various formats: Return to zero (RZ), Non return to zero, (NRZ), Modified duobinary RZ (MDRZ), Carrier suppression RZ (CSRZ).

Performance enhancement of OCDMA system based on 3D-Multi-Diagonal codes

A new family for three dimensional (3D) Optical Code Division Multiple Access using Multi-Diagonal (MD) code is developed. It is characterized by a large cardinality, high autocorrelation and zero cross correlation. So, the multi-access interference (MAI) is totally eliminated. Mathematically, it is seen that the correlation property of the proposed 3D code depends on the code weights of different sequence code used for its construction. For results, the 3D-MD has a better performance than the one and two-dimensional (1D and 2D) codes. The importance of introducing the 3rd dimension is justified by the high signal to noise ratio (SNR) and low bit error rate (BER) compared to 1D and 2D MD codes.