Showing papers presented at "International Conference on Transparent Optical Networks in 2000"

Conversion efficiency of fiber wavelength converter based on degenerate FWM

Abstract: This paper I present the design theory of the FWM wavelength converter using single-mode optical fiber. The conversion efficiency for far off and around zero-dispersion wavelength of a fiber are discussed and compared. The theoretical calculations of the conversion efficiency for both cases are made. The numerical results for wavelength conversion around zero-dispersion wavelength are clearly shown in conversion diagrams. In this paper I also address the optimization of conversion efficiency and bandwidth.

Protection and restoration in optical networks

Abstract: Summary form only given. Today's DWDM optical line systems (OLS) carry OC48/OC192 SONET/SDH voice and data, fiber-cut and equipment-failure protected by the SONET/SDH rings. Emergence of new transmission protocols such as IP over fiber or gigabit Ethernet requires protocol independent optical protection implemented in the new transmission layer called an optical network. High cost of 1+1 dedicated protection is reduced with the optical shared ring protection (OSPring) where a single protection wavelength protects against simultaneous failures of non-overlapping paths on several service wavelengths. Simultaneous failures of overlapping paths cannot be protected by OSPring. Optical cross connects interconnect DWDM OLS systems to give the ability to restore traffic from the failed OLS by re-routing it through its inter-connected partners. The required 50 milliseconds protection delay is much shorter than the seconds long restoration.

Selective wavelength transparent optical add-drop multiplexer based on fibre Bragg gratings

Abstract: A configurable optical add-drop multiplexer (OADM) based on fibre Bragg gratings is reported. Dynamical selection of the add-drop or pass-through functionality is realised according to the control of an optical switch. OADM performances measurements in a 70 km, 3/spl times/2.5 Gb/s channel WDM network are reported.

Computer networks based on optical passive couplers

Abstract: The practical realisation of passive fibre coupler network Ethernet 10 Mb/s is presented The passive star coupler configuration has been particularly emphasised The practical configurations of the Ethernet 1O Mb/s-computer network using special properties of passive star fibre couplers have been described It allows using the ordinary transceivers with simple algorithm of collision detection

All-optical analog-to-digital converter for photonic networks using multilevel signaling

Abstract: We propose an all-optical analog-to-digital converter that can extract a binary word from a multilevel optical signal during a single bit interval. This optical circuit is constructed using optical limiters whose transmitted power clamps to a fixed maximum level for inputs exceeding a chosen threshold.

Wave propagation through all-dielectric multilayered optical fiber

Abstract: All dielectric fibers with a uniform core and multi-layered cladding have been analyzed using modal analysis and beam propagation methods. It has been shown that multi-layered fibers can provide an alternative to photonic crystal fibers for large-core amplifiers and the active elements of fiber lasers.

Optical fiber devices

Abstract: Recent progress in research on optical fiber devices, especially optical fiber couplers and optical fiber grating couplers are reviewed. Add-drop multiplexer operation by optical fiber grating couplers has recently attracted attention, because of its inherent low-insertion loss, simple implementation, and potential low-cost.

Reflection and transmission of a light on a dielectric boundary in a time domain

Abstract: The description and understanding of the propagating of THz pulses in optical systems has recently attracted considerable research efforts. Common methods to generate sub-picosecond, single-cycle electromagnetic pulses evoke great interest and there is an excitation of a biased semiconductor or an electro-optic crystal with a femtosecond light pulse among them. It needs a detailed investigation of the propagation properties of ultrashort pulse beams scattered by interfaces with time-varying properties. In this paper we obtain integral operators that describe in time domain in the 3-D case an interaction of complex electromagnetic signals with the flat interface between dielectric media when the medium in one of the two halfspaces changes its permittivity and acquires a conductivity.

Towards an all-optical terabit network: the impact of photonic bandgap structure technology

Abstract: Photonic band-gap (PBG) structures, also known as photonic crystals, are one of the crucial technology factors leading to the achievement of several functions that an all-optical network asks for. PBG-based devices have numerous potential functional locations within the advanced all-optical network architecture. In the paper the state-of-art and also the possibility of potential future applications of PBG structures in optical telecommunication systems are reviewed, and their impact on the development of all-optical transport networks is discussed.

Realization of SSFM for nonlinear pulse interactions influence on transmission efficiency in soliton communication lines

Abstract: Numerical analysis of nonlinear Schrodinger equation with split-step Fourier method for modeling of pair soliton pulses propagation in fiber optic communication lines is used. Some results of computation of real optical lines are presented.

Influence of the laser detuning on optical WDM network performance

Abstract: The laser wavelength dependence on the temperature, polarization current, aging can represent a problem in networks where multiple multiplexing and demultiplexing operations occur. In this contribution we evaluate the system performance dependence on the laser frequency alignment, considering demultiplexing performed by some of the commonly used filters.

The application of integral equations to calculation of diffraction on inhomogeneities in lightguide structures

Abstract: The numerical code for the simulating of electric fields scattered on two-dimensional bodies of arbitrary shape and either law of nonlinearity is elaborated. In this paper we present results of calculations for cylinders of elliptical cross-section and quadratic nonlinearity law. Due to good convergence of series and integrals it is enough to sum 20-30 terms in series and numerical quadrature to get a deviation up to 0.1%. In this paper we have simulated the power transmitting coefficients for diffraction on: 1) grating made of dielectric rods; 2) dielectric rod set inside of a planar metallic waveguide; 3) dielectric rod situated next to a dielectric planar waveguide layer.

Nonlinear optical propagation in periodical and quasiperiodical layered structures

Abstract: Summary form only given. The considered structures are obtained by alternating two dielectric layers of different refractive indices such that the highest refractive index layers belong to some fractal set. The triadic Cantor and the Fibonacci sets are considered as examples. The transfer matrix method is used and some of its properties are presented. Then the nonlinear transmission properties are discussed for second order nonlinear polarization. An analysis on phase matching conditions is presented. Additional analysis is performed when the input level intensity is so high to induce third order nonlinear polarization into the dielectric media constituting the structures. Mesoscopic model is also introduced.

Optical CDMA system based on amplifying fiber Bragg gratings chain

Abstract: In the presented paper frequency encoded Fiber-Optic Code Division Multiple Access (FO-CDMA) technique with broadband sources is investigated. The results of computer modeling of amplifying fiber Bragg gratings and the possibility of their implementation by using of consequent connected gratings as a coder in transmitter and correlator in receiver sides are shown. By applying of numerical models the performance analysis of frequency encoded FO-CDMA system is presented. Calculations are carried out for M-sequences and Walsh codes. It is shown that the choice of code sequence inside of the same family of codes, in the case of coded spectrum non uniformity, is an important factor for signal to noise ratio evaluation. The evaluation of the network operation distances under the fiber dispersion impact is also presented.

Pressure tuned laser diode as a light source for characterization of optical transmission lines

Abstract: Room-temperature emission of 1310 nm InGaAsP-InP laser diode has been studied as a function of hydrostatic pressure in an optical clamp cell up to 20 kbar. The diode was a commercial single-mode device by Siemens. The emission line shifted towards the shorter wavelengths similar to the bandgap of the constituent materials. The tuning range was over 200 nm. Here we consider the possibility of applying the high pressure cell with commercial laser diode inside as a pressure-tuned light source because of its narrow lines, wide tuning range and easy to implement portable equipment. It could be useful for measuring absorption and dispersion in optical transmission lines. Application of different types of electronically tunable lasers in the cell could further extend the tuning range and provide fine tuning and continuous tuning.

Long distance analog CATV link utilizing non-zero dispersion-shifted fiber

Abstract: Analysis of long distance analog CATV link utilizing NZDS fiber is presented. In externally modulated lightwave AM-CATV link the main limiting factor is transmitting medium i.e. optical fiber. High dispersion of standard fiber limits CATV link span to below 100 km. Presented results of simulations confirmed that utilizing NZDS fiber can improve the span to more than 150 km.

Optically controlling photonic band gap logic elements

Abstract: The change in the refractive index of GaAs due to the light-induced generation of nonequilibrium charge carriers is shown to substantially change the transmission of a one-dimensional GaAs/GaAlAs photonic band-gap structure, allowing low-threshold photonic-crystal optical logic gates to be created. Elementary logic operations of the Boolean algebra performed with nonlinear PBG structures, including the biconditional implication, module-two addition, Peirce's arrow, and disjunction, are demonstrated. We show how different logic operations can be performed with the same GaAs/GaAlAs PBG structure at different power densities of logic pulses.

Syntheses of single-mode optical fibers with minimal dispersion

Abstract: The development of the method of single-mode fibers for a given values of phase and group velocities of propagated wave at a fixed frequency is presented in this study. The received refraction profile provides minimal dispersion. New types of gradient single-mode dielectric fibers have a wide bandwidth of a single-mode regime and increased effective area of light flow.

Optical filters for systems with wavelength division-multiplexing

Abstract: The construction and results of accounts of the optical filter consisting of the ring resonator coupled with optical waveguides are submitted in this work. The characteristics of filters for different values of its parameters are represented. The expediency of application of filters in systems with WDM and DWDM is noted.

Fast solution to the scattering by arbitrary smooth dielectric cylinders based on the method of regularization

Abstract: Novel highly efficient algorithm for the solution of 2-D problems of the wave scattering from homogeneous dielectric cylinders of arbitrary cross-sections is presented and its applications to simulate optical waveguide components based on dielectric resonators (DR's) are discussed. The algorithm developed is based on the concept of analytical regularization (semi-inversion) of the singular integral operators.

The Fabry-Perot laser diode controlled by the fibre Bragg grating

Abstract: A simple configuration of a multimode laser diode with external cavity terminated by a fibre Bragg grating is presented. The improvement of its spectral purity and wavelength stabilisation is demonstrated.

Improved dispersion tolerance of duobinary optical transmission considering the influence of duobinary filters and optical input power

Abstract: We consider the efficiency of dispersion compensation to optical duobinary transmission. Considering dispersion compensation of one span we study the influence of transmitter configuration and optical input power to the dispersion tolerance.

Conversion of LP/sub 02/-mode into LP/sub 01/-mode in optical fibers with Kerr-like nonlinearity

Abstract: Influence of Kerr-like nonlinearity on the transmittance of a guiding structure consisting of double mode and single mode step-index fiber sections is estimated. The possibility to use such structure for pulse compression is analyzed and parameters of the structure that correspond to the largest effect of pulse compression are determined. Interaction of modes in double mode nonlinear fiber is investigated.

Propagation of chirped rectangular pulses in nonlinear lossless optical waveguide

Abstract: Propagation of the chirped ultra-short optical pulses in nonlinear lossless optical waveguide is discussed. The nonlinear Schrodinger equation is solved numerically for complex initial conditions using beam propagation method. In order to calculate the stationary peak value of the envelope, an averaging filter was used, and estimated critical value of the chirp parameter was calculated with the use of rational extrapolation algorithm in case of rectangular initial pulse.

Etching of n-type GaAs for fabrication of semiconductor laser

Abstract: Formation of smooth-vertical mirrors on GaAs by wet etching and reactive ion etching has been investigated for the fabrication of oxide-isolated stripe geometry lasers. The wet etching was carried out by the solution H/sub 2/SO/sub 4/-H/sub 2/O/sub 2/-H/sub 2/O at 2/spl deg/C for 10 and 20 minutes. The dry etching was performed using SiCl/sub 4/ gas in a single chamber reactive ion etcher (RIE). The optimum values obtained for the RIE system to achieve a smooth and vertical profile were 25 mTorr, 25 seem and 50 W respectively for pressure of the etch gas, mass flow rate of the etch gas and power of the machine. The etch profiles obtained for both wet and dry etching were inspected in the scanning electron microscope (SEM). The etch rate for wet chemical etching was found 0.01 /spl mu/m/minute while it was 0.45 /spl mu/m/minute for dry etching.

Erbium doped fiber for L-band EDFA

Abstract: Extension of quantity of transmission channels quantities in wave division multiplexing (WDM) is possible by wide spectral range of erbium doped fiber amplifier (EDFA) work. In this paper we present description of preparation and results of measurements of optical and spectral property of optical fiber from silica glass, which was doped with erbium in core (erbium doped fiber-EDF). This is optical fiber about absorption and issue curves shifted in direction of longer waves with comparison to standard EDF uses for construction of EDFA on band C. Thanks to this, what is supposed, this fiber will be useful to construction of EDFA on band L.

All-optical demultiplexing and format conversion using an ultrafast polarization bistable VCSEL

Abstract: All-optical demultiplexing with a signal-bit width conversion function has been experimentally demonstrated using an ultrafast polarization bistable VCSEL. All-optical format conversions (both from RZ to NRZ and vice versa) have also been experimentally demonstrated.

Ways of raising the effectiveness and evaluating the exactitude of the stratification method of analysis of inhomogeneous dielectric waveguides

Abstract: We suggest ways of raising the effectiveness and of evaluating the exactitude of the method of stratification for the analysis of inhomogeneous dielectric waveguides. We will use the example of the symmetrical planar waveguide with dielectric boundaries. It is necessary to mention that the suggested method is valid both for the asymmetric planar optical waveguides, including those with reflecting metal boundaries, and for the optical fibers with diverse cross-sections.

Effect of homodyne crosstalk in WDM ring/bus networks

Abstract: The effect of homodyne crosstalk, including both coherent and incoherent crosstalk, introduced by optical add/drop multiplexers in wavelength division multiplexing ring/bus networks is studied. It is found that the effect of coherent crosstalk cumulates quickly as the number of nodes through which an optical signal passes increases, while the effect of incoherent crosstalk remains the same. Our results show that coherent crosstalk is the main source of signal degradation when the number of passed nodes is large.

Beam propagation analysis of non-linear tapers

Abstract: The beam propagation method implemented in a tapered co-ordinate system is used to analyse a nonlinear taper structure. The results obtained are compared with the ones computed using the standard beam propagation algorithm in the rectangular co-ordinate system. In all analysed cases the novel approach: the tapered beam propagation method, allows calculation of the field distribution and the field overlap at the end of the structure faster and using less computer memory.