Search

This paper describes novel configurations of shorted fractal Sierpinski gasket antenna. The antenna uses half the structure of a conventional Sierpinski gasket antenna and is folded over to be parallel to the ground plane, to form an element similar to that of the inverted L antenna. A quasi log periodic resonance behavior is obtained with a shorting pin placed at the far end of the antenna. Several configurations are shown and a design using two shorting pins which improves the bandwidth at the fundamental band is also demonstrated.

The terminal equipment costs associated with electronic multiplexing can comprise of a dominating percentage of the total network costs in today's backbone wavelength-division-multiplexed (WDM) synchronous optical network (SONET) ring networks. The deployment of wavelength add-drop multiplexers (WADM) allows certain wavelengths to optically bypass the nodes without being electronically terminated, thus can effectively reduce the total equipment costs if connections and channels are appropriately assigned in traffic grooming. This paper presents a series of wavelength assignment algorithms with the objective to optimize the number of required wavelengths and SONET add-drop multiplexers in both unidirectional and bi-directional rings under an arbitrary grooming factor. In our analysis, we have considered both uniform and non-uniform all-to-all network traffic. As a simple model for realistic traffic pattern, a special case of non-uniform traffic, distance-dependent traffic is analyzed in detail. Significant ADM savings are reported for different traffic scenarios using our proposed algorithms.

An optical spectral-amplitude-coding CDMA network is proposed as a solution to the IP routing bottleneck in the global Internet. Its performance has been analysed for two different cases. For a given peak bit rate the network performance can be improved by reducing channel utilisation. However, when each user in the network has a fixed average bit rate, an optimal utilisation exists for the overall network performance. Analytical results clearly indicate that optical spectral-amplitude-coding CDMA technology may be a good candidate for the future IP backbone.

Unipolar codes with ideal in phase cross-correlation are important in spectral amplitude-coding optical code-division multiple-access (CDMA) systems since these codes eliminate multiuser interference and also suppress the effect of phase-induced intensity noise. However, very little research work has been done on such codes although codes with ideal cross-correlation have been studied for many years. In the paper by Zhou et al.(see Electron. Lett., vol.36, p.728-29, 2000), such a code has been introduced without a clear construction method. In this paper, we firstly review this old code, and then construct two new codes with ideal in-phase cross-correlation in algebraic ways. Both of the proposed new codes are obtained by modifying former codes with ideal cross-correlation. It has been shown that the system performance can be improved significantly by using codes with ideal in-phase cross-correlation instead of the Hadamard code. These codes can also be used in synchronous optical CDMA systems for multiuser interference cancellation.

In this paper we have investigated various effects that determine the performance of a multi-wavelength Brillouin-Erbium Fiber Laser (MWBEFL) system. The process of multiple generation and the importance of the erbium doped fiber laser (EDFL) lasing gain to produce multiple Stokes signals in the system have been discussed. It has been found that the lasing gain plays an important role in determining the threshold, peak power, number of Stokes signals generated and the tuning capabilities of this system. The threshold and output power of the proposed MWBEFL system are 35.8 mW and -8 dBm, respectively, which can deliver up to 13 Stokes signals (laser lines) at 0.08 nm (11 GHz) line spacing.

In high-speed wavelength-division-multiplexed synchronous optical network (SONET) ring networks, the terminal equipment costs associated with electronic multiplexing can be predominantly high. Placing a wavelength add-drop multiplexer (WADM) at each network node allows certain wavelengths to optically bypass the node without being electronically terminated. This approach can effectively reduce the total equipment cost if connections and channels are appropriately assigned in traffic grooming. In this paper, we present a series of wavelength optimization and wavelength assignment algorithms with the objective to optimize the number of required SONET add-drop multiplexers and yet minimizes the number of wavelengths in both unidirectional and bidirectional rings under an arbitrary grooming factor. In our analysis, we have considered both uniform and general nonuniform all-to-all network traffic. As a simple model for realistic traffic patterns, a special case of nonuniform traffic, distance-dependent traffic, is analyzed in detail. Significant ADM savings are observed for different traffic scenarios using our proposed algorithms.

We have proposed a new dynamic model for both tapered laser oscillator and laser amplifier structures based on transmission-line laser modeling. The internal laser processes are represented in terms of microwave circuit theory, giving additional insight to the operation of the laser. The model is semianalytical to improve computational efficiency and is in time domain to allow inclusion of nonlinear effects. Simulation results agree with published results, proving the validity of the model. The dynamics of picosecond pulse amplification in tapered amplifier structures have been studied using the model, taking into account the effects of pulse energy and residual reflectivity. It has been found that residual reflectivity can give an almost undistorted amplified pulse, at the expense of pulse energy gain.

The transmission-line laser model is a powerful and flexible method to model various types of laser devices. An integrated laser transmitter model comprising the intrinsic laser, an electrical parasitics network and a passive matching network is proposed for microwave-optoelectronic simulation in the time domain. Transmission-line matrix stub lines and link lines are used to model the matching network and electrical parasitics. The passive matching network is based on monolithically integrated lumped elements. The effect of electrical parasitics has been taken into account when designing the matching network. Simulation results are in good agreement with those of commercial software. A microwave application of the integrated laser transmitter model is demonstrated in harmonic generation through gain switching.

The sub-picosecond gain dynamic in a highly index guided tapered-waveguide laser diode amplifier is studied. The analysis is based on a set of rate equations for the carrier density N and carrier temperature T, where the effects of lateral distributions of both N and T are considered. It is found that both N and T have significant effects on the gain dynamic of the tapered-waveguide laser diode amplifier. The gain saturation of the tapered-waveguide amplifier for both 20ps and 200fs pulses is also calculated.

We have studied the effects of introducing phaseshifts in the active section of a m phaseshift-controlled DFB wavelength tunable filter on tuning range, peak power transmissivity and side-mode suppression ratio (SMSR). The analysis indicates that when the filter wavelength tuning range is 22.1 ? for the grating coupling coefficient while maintaining almost constant transmissivity (gain) of more than 35 dB. The filter SMSR ranges from 11.1 to 25.4 dB. The results for asymmetric values of and are also given.

A new semiconductor laser diode amplifier structure which consists of a semiexponential-linear tapered waveguide active layer has been proposed to improve the saturation output power. Various characteristic performances of this device have been analysed based on the step-transition approach taking into account the effects of the spatial distributions of the carrier density and the optical field. The effects of various tapered structures on the gain saturation, intensity distribution and amplified spontaneous emission noise have also been investigated.

This letter presents the design of six-resonator multiple-coupled microstrip filter. A low-pass prototype of six-resonator multiple-coupled filter is developed first based on the conventional Chebyshev filter. The characteristics of attenuation poles located on both sides of the frequency response are described. According to the low-pass prototype, the design of a six-resonator multiple-coupled microstrip hairpin filter at 6 GHz is completed with the aid of EM simulation. The experimental results are demonstrated and discussed.

The effects of strain upon the bandgap energy, the refractive index, and the confinement factor of a SCH laser diode with InxGa(1−x)As as its active layer have been investigated. © 1994 John Wiley & Sons, Inc.

We have proposed a new modified quadratic congruence (MQC) code for spectral amplitude-coding optical code division multiple access (CDMA) systems. Although this new MQC code has many advantages, however, it only exists for each prime number p. In this letter, we have proposed a family of new codes which can be constructed by an algebraic technique over each GF(Q) field for each prime power Q=p/sup n/ (where n is a positive integer). Therefore, compared with MQC, this new code exits for a much wider number of integers, and hence, we can choose a code with the desired length more freely. Moreover, with the same properties as the former MQC code, this new code possesses all the advantages of MQC code, such as suppression of the intensity noise, easy implementation by using fiber gratings, and convenience to realize flexible encoder reconfiguration.

The second harmonic power generation efficiency (SHPGE) obtained under phase-matching conditions in organic crystal-cored fibers having different cladding materials have been investigated. It has been found that a very high SHGPE can be obtained under certain conditions.

The dependence of the cleaved facet reflectivity R0 and hence the mirror loss alpha m0 for the fundamental TE0 mode oscillation of BH InGaAsP/InP laser diodes (LD) emitting at 1.3 and 1.55 mu m wavelengths, upon the laser diode parameters, has been studied.

We have proposed a novel approximate analytical expression for saturation intensity for tapered traveling-wave semiconductor laser amplifier structures. The application of this analytical expression of saturation intensity has been demonstrated by considering the effect of gain saturation on polarization sensitivity of two tapered amplifier structures, linear and exponential tapered amplifier structures. It is found that polarization sensitivity of the tapered amplifier structure is several decibels higher than that of passive tapered waveguides in unsaturated condition. Polarization sensitivity of the two tapered amplifier structures has also been investigated in a highly saturated condition. The combined effects of mode conversion and gain saturation on fundamental TE gain have also been investigated using the proposed analytical expression for saturation intensity.

We propose and demonstrate the use of a single long period grating (LPG), having one cladding mode that is unresponsive to changes in curvature, for simultaneous measurement of curvature and temperature. We also demonstrate that such a cladding mode can be produced at different wavelengths in a standard single mode fibre (SMF). Furthermore, we show that harmonic modes of LPGs, that are often undesirable in many applications, can now be utilized along with such a curvature-insensitive cladding mode to achieve a sensor that can measure curvature and temperature simultaneously, whilst having the capability to compensate for induced strain.

Numbers of small antennas were designed and various kinds of antennas were tested for measurement. The purpose of this paper is to show that the antenna efficiency can be measured accurately in much faster, easier and cost effectively reverberation chamber.

This paper presents the design of a six-resonator multiple-coupled microstrip filter. A lowpass prototype is developed first based on the conventional Chebyshev filter. According to the lowpass prototype, the design of a six-resonator multiple-coupled microstrip hairpin filter at 6 GHz is completed with the aid of EM simulation. The experimental results are demonstrated and discussed.

Wavelength conversion using cross-gain modulation (XGM) in linear tapered-waveguide semiconductor laser amplifiers (SLAs) has been investigated theoretically and compared with the non-tapered semiconductor laser amplifier. For example, we have found that for the linear tapered-waveguide SLA with a 450 pm cavity length, a higher signal power is required to achieve a similar extinction ratio as obtained by the conventional SLA with the same cavity length. However, a similar extinction ratio is observed for both conventional and linear tapered-waveguide with the cavity length of 1200 pm. The difference between the extinction ratio for up and down conversion is less severe in a linear tapered-waveguide SLA as compared to that for a conventional SLA. The rise time for linear tapered-waveguide is observed to be higher than that for conventional SLA. It is possible to attain extinction ratio conservation using XGM for both up and down conversions in a SLA with a very long cavity length of 2400 μm.

We investigate the inband crosstalk arising at the synchronization module of photonic packet switches, and find that the impact of the 2/sup nd/ order crosstalk is significant when the number of fiber delay lines is greater than 10.