Houria Rezig

Design of temperature-strain tunable UDWDM, DWDM, WDM FBG filter for Passive Optical Network Access

We report in this work, the simulation results of a tunable UDWDM, DWDM and WDM filter. The filter is based on Fiber Bragg Grating (FBG) component and will be printed on a Standard optical Fiber (SMF28) by photo-inscription. Filter response is studied versus temperature and strain variation applied on the fiber. Designed filter will be used to tune passive optical network (PON) access devices like Encoder, Decoder, DEMUX, etc... The results show that tuning wavelengths in UDWDM, DWDM or WDM is more suitable by strain effect. However, temperature will be used to tune DWDM or WDM wavelengths.

Pulse reflection of tunable Fiber Bragg Grating WDM filter

To determine the rate performance of tunable WDM filter at high bit rates, the pulse response of the filter based on Fiber Bragg Grating (FBG) is studied. We qualitatively explain the interaction of the input pulse when it propagates through the grating. For the three examined cases: 10 Gbit/s, 20 Gbit/s, 40 Gbit/s, the reflected pulses have the same input shape, but in the two latter cases, a wide Full Width at Half Maximum (FWHM) is noted what generating chromatic dispersion. Material dispersion is found to play only a minor role in the pulse response versus different rates. In a second part, under the appropriate bit rate, the pulse response of the WDM filter is investigated when it is tuned by temperature effect. The filter response will be tuned only in UDWDM and DWDM domain because of the high temperature value required in WDM. The main feature is the very weak amplitude of the reflected pulse from tuned FBG which provides negligible interference in high rate communication systems.

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.

DS-OCDMA encoders/decoders synthesis using fiber Bragg gratings

In this paper, we propose a numerical tool for the synthesis of DS-OCDMA Encoders/Decoders based on Fiber Bragg Gratings. The techniques of synthesizing FBG are described. In particular, we point out the layer peeling method as inverse scattering approach and a genetic algorithm approach to design DS-OCDMA Encoders/Decoders. Finally, we compare the results of the two synthesizing methods.

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).

Performance comparison of coherent versus incoherent direct sequence optical code division multiple access system

In this paper, we compare the performances of a coherent versus incoherent Direct Sequence Optical Code Division Multiple Access (DS-OCDMA) system. Superstructured Fiber Bragg Grating (S-FBG) encoders/decoders are used to implement unipolar codes such as Prime Sequence (PS) and Extended Quadratic Codes (EQC) codes. We implement the Importance Sampling (IS) technique, which is a variant of the well-known Monte-Carlo (MC) method, to evaluate the Bit Error Rate (BER) performances of the system. Our simulation results depict that coherent system outperforms the incoherent one. The last system can be used but a BER floor is demonstrated due to the beat noise of the incoherent source. We show that increasing bit rate leads to a deterioration of the BER behavior and requiring an increase of the optical bandwidth of the signal.

Comparison of unipolar codes for DS-OCDMA system

In this work, we describe a Direct Sequence Optical Codes Division Multiple Access (DS-OCDMA) system using unipolar codes which are the Prime Sequence (PS), the Quadratic Codes (QC) and the Extended Quadratic Codes (EQC). The performances comparison of the three family codes, for coherent and incoherent source, shows that the EQC codes offer better results on term of Bit Error Rate (BER) than the two others family codes. In fact this family codes presents the better correlation properties. Moreover, we demonstrate that by controlling the optical bandwidth of the encoders/decoders, we can improve system performances in the case of incoherent source.

Performance evaluation for a new implementation of multirate optical fast frequency hopping CDMA system for multimedia transmission

This paper reports a new implementation of all-optical communication system for high-bandwidth multimedia applications intended for the upcoming generation of optical access network. We propose a new configuration of multirate optical fast frequency hopping CDMA (OFFH-CDMA) system architecture using fibre Bragg gratings (FBGs). Indeed, the multimedia applications, including data, audio, video and voice with different performance and traffic constraints (i.e. real-time delivery), require different rates and different quality of service (QoS). Bit-error-rate analysis assuming Gaussian approximation for the error probability has been carried out. The results of the numerical analysis reveal that this system can support more simultaneous users than the other configurations over the same optical bandwidth with two different data rates. This result allows us to expect that the fast frequency hopping-optical code division multiple access system is qualified to support the multimedia applications in optical access network.

Reflection spectrum study and polarization effects on apodized fiber Bragg grating filter

Spectrum properties of apodized fiber Bragg gratings (AFBGs) are well studied, in particular, when there is a need to reduce transmission side lobes. Otherwise, the polarization properties of these gratings are rarely reported when evaluating system performance. We analyze the reflected spectrum, the polarization-dependent loss (PDL), and the differential group delay (DGD) of an AFBG written in a single-mode fiber (SMF28). The evolution of these properties versus the grating parameters is studied based on the coupled mode theory. We mainly focus on the PDL and DGD maximum amplitudes and their wavelength separation. The simulation analysis is developed by means of the transfer matrix method. We demonstrate that the apodization function induces some asymmetry between the left and right parts of the PDL and DGD curves. The maximum amplitudes of the PDL and DGD converge to constant values versus birefringence but increase with grating length.