OPTICS 2011 Abstracts


Full Papers
Paper Nr: 13
Title:

PHOTONIC ANALOGUE-TO-DIGITAL CONVERTER BASED ON WAVELENGTH DIVISION MULTIPLEXING TECHNIQUE

Authors:

Tiago Alves and Adolfo Cartaxo

Abstract: A photonic (Ph) analogue-to-digital (ADC) converter architecture based on the wavelength division multiplexing (WDM) technique used to provide compressed spectrum of the ultra wideband radio signals that are being used in a given pico-cell area for monitoring purposes is presented. The signal at the different points of the WDM Ph-ADC architecture is analyzed and discussed in detail. The advantages/disadvantages of the WDM architecture are identified and compared with its time division multiplexing (TDM) counterpart. It is shown that the WDM Ph-ADC architecture provides adequate time stretching of the wireless signals captured in a given pico-cell. This system enables relaxing the bandwidth requirements of the electrical ADCs used to digitize the wireless signals prior digital signal processing is applied for spectrum and transceivers localization monitoring. In addition, it is concluded that the WDM Ph-ADC architecture supports higher pulse repetition rates than the TDM Ph-ADC architecture being of special interest when a fast up-date of the radio channel monitoring is required.

Short Papers
Paper Nr: 1
Title:

A STABLE TUNABLE AND SWITCHABLE DUAL-WAVELENGTH SINGLE-LONGITUDINAL-MODE ERBIUM-DOPED FIBER LINEAR-CAVITY LASER

Authors:

Xiaoying He

Abstract: A simple linear cavity erbium-doped linear-cavity laser is proposed and experimentally demonstrated, with tunable and switchable multi-wavelength SLM operation. The main mode-selection components of our system include an FBG Sagnac loop, an umpumped EDF together with a tunable FBG. The unpumped EDF together with the tunable FBG form a super narrow-band self-tracking FBG around the reflection peak of such tunable FBG, which ensures the SLM laser operation. By simple adjustment of two polarization controller, the laser can be designed to operate in a stable single-wavelength or dual-wavelength with a wavelength spacing of 0.05 nm at room temperature.

Paper Nr: 2
Title:

OPTICAL MIMO MULTIMODE FIBER LINKS - Channel Measurements and System Performance Analysis

Authors:

Andreas Ahrens and Jens Pankow

Abstract: Wireless communication is nowadays one of the areas attracting a lot of research activity due to the strongly increasing demand in high-data rate transmission systems. The use of multiple antennas at both the transmitter and receiver side has stimulated one of the most important technical breakthroughs in recent communications allowing increasing the capacity and dropping the bit-error rate. However, multiple-input multiple-output (MIMO) systems are not limited to wireless MIMO systems and can be observed in a huge variety of transmission links and network parts and have attracted a lot of attention since the mid 90's. In the field of optical MIMO transmission systems, multi-mode (MM) fibre offers the possibility to transmit different signals by different mode groups. The perspective of the MIMO philosophy within the field of optical transmission systems is elaborated in this contribution based on channel measurements within a 2 x 2 MIMO system. For the channel measurements the second optical window and a fibre length of 1,4 km was chosen. Computer simulations on an overall data rate of 10,24 Gbps underline the potential of multi-mode fibres in optical high-data rate MIMO communication systems and show that in order to achieve the best bit-error rate, not necessarily all MIMO layers have to be activated.

Paper Nr: 9
Title:

OPTIMIZATION OF OPTICAL SSB-OFDM SYSTEM WITH DIRECT DETECTION FOR APPLICATION IN METROPOLITAN/REGIONAL NETWORKS

Authors:

Bruno M. M. Meireles and João L. Rebola

Abstract: Due to its spectral efficiency, dispersion robustness, simplicity and transparency to electrical modulation format, orthogonal frequency division multiplexing (OFDM) is a promising technique that allows to increase the capacity and to make the upgrade of optical telecommunications systems already installed. In this work, the study and optimization of OFDM transmission in an optical communication system using direct detection with a short and medium range (metropolitan and regional networks) for a target bit rate of 10 Gbps will be performed exhaustively. The optimization is carried out taking into account the impact of noise accumulation and of signal distortion resulting from bandwidth narrowing introduced by the cascade of add-drop multiplexing nodes on the network performance. Optical transmission of single sideband OFDM signals is considered and the carrier-to-signal power ratio of the OFDM signal is optimized in order to achieve the best network performance.

Posters
Paper Nr: 10
Title:

A COMPARATIVE STUDY OF THE TEMPERATURE DEPENDENCE OF LASING WAVELENGTH OF CONVENTIONAL EDGE EMITTING STRIPE LASER AND VERTICAL CAVITY SURFACE EMITTING LASER

Authors:

Niazul Islam Khan

Abstract: Semiconductor lasers are the integral parts of optical communication systems. The temperature dependence of the lasing wavelength of a laser is an important issue because it is used in different environment with varying thermal conditions. In this paper, a comparative study of the temperature dependence of lasing wavelength of two types of laser diode has been presented. The comparison was made between an InGaAsP/InP stripe geometry edge-emitting laser and vertical cavity surface emitting laser (VCSEL) with GaAs in the active region. For both cases, the temperature dependence was observed for different heat sink temperatures ranging from 20ºC to 50ºC at an interval of 5ºC for an operating current of 0.763A and 1.88mA respectively. The lasing wavelength shifts for stripe laser and VCSEL have been found to be 0.3nm/K and 0.06nm/K respectively. VCSEL exhibits significantly greater thermal stability than stripe laser. The result has also been elucidated with a comprehensive theoretical excerpt.

Paper Nr: 12
Title:

OPTICAL DOMAIN MULTIUSER INTERFERENCE ESTIMATION FOR SPECTRAL PHASE ENCODING OPTICAL FIBRE CDMA SYSTEMS

Authors:

Arash Yazdani, Morteza Noshad and Hojat Jaliloghli

Abstract: In this paper, an effective technique for reducing the multi-user interference (MUI) in spectrally-phase encoded optical code division multiple access (SPE-OCDMA) systems has been proposed. In this method the effect of MUI signal on the main user’s signal has been decreased using multiuser interference detection (MID). Two structures have been introduced for accomplishing MID and degrading its destructive effect on the decoded ultra-short light pulse; temporal multiuser interference estimation (TMIE) and nonlinear multiuser interference estimation (NMIE). Both of these methods utilize two photo-detectors for estimating the MUI signal. In spite of simple structure of these two receivers, their performance analysis shows an improved performances comparing to other receivers.