Characterization of optical properties of optical polymers

Possible applications of polymer materials in optical systems and devices are defined mainly by their optical properties in terms of refractive indices, transmission, dispersion and thermo-optic coefficients. We have examined more than twenty types of optical plastics including basic, commercial and some new development materials. Detailed measured refractometric data and transmission spectra in the visible and near infrared regions are presented. Variation of refractive indices with temperature is considered to obtain the thermo-optic coefficients. Discussion on dispersion of studied optical polymers and comparison to glass is included on the base of a number of dispersive characteristics and curves.     

Polarization-rotated optical feedback in self-coupled optical pickup

The rotation of the plane of polarization of the return beam perpendicular to that of the outgoing laser beam using a quarterwave plate in the self-coupled use of a semiconductor laser diode effectively suppresses the operation instability which degrade S/N performance in optical memory playback applications.     

Bending-induced optical loss in random-hole optical fibers

We present the experimentally determined optical bend loss for random hole optical fibers in the spectral range 1520 to 1570 nm induced by wrapping the optical fiber around a fixed diameter mandrel. The optical losses are compared to those obtained for a single-mode fiber and a multimode fiber using the same bending procedures. The bending induced optical losses in the random hole optical fibers were several orders of magnitude lower than for the single-mode fiber and were about 1 order of magnitude lower than for the multimode fiber.     

Giga-bit optical receiver for plastic optical fibre

An optical receiver with high sensitivity and linearity specially designed for Giga-bit communications over small-bandwidth high-attenuation multimode plastic optical fiber is presented. An automatic gain control transimpedance amplifier and linear post amplifiers are used to maintain a good performance with multilevel modulation. Using multilevel signaling and large-diameter integrated photodiodes make the presented optical receiver suitable for large core plastic optical fiber. For a wavelength of 675 nm, a sensitivity of −26.3 dB m (BER = 10⁻⁹) at 500 Mb/s is presented by a binary signal. A data rate of 1 Gb/s and a sensitivity of −19.8 dB m (BER = 10⁻⁹) are achieved with four-level pulse amplitude modulation.     

Performance of optical links with optical amplifiers

In this work a comparison between the performances of single and multichannel systems is reported for links with optical amplifiers, considering conventional and soliton signals, Time Division Multiplexing (TDM), and Wavelength Division Multiplexing (WM) techniques. The performance evaluation is obtained by means of numerical simulations taking into account the effects of the chromatic dispersion, the Kerr nonlinearity, and the ASE noise of the optical amplifiers. Both the regimes of constant and fluctuating chromatic dispersion along the link are studied. The possibility of implementing high-capacity optical systems for a high-bandwidth European network is evaluated.     

Low threshold optical bistability with optical pumping

By use of circularly polarized light we have exploited optical pumping within the Zeeman sublevels of the ground state to obtain optical bistability in sodium vapours with low threshold power (around 1 mW) and a wide tuning range (>12 GHz). Experimental results are presented for different conditions of operation and compared to computer calculations, that include propagation effects and inhomogeneous broadening, based on a three-level atomic model that accounts for optical pumping.CEILAP, Buenos Aires, Argentina     

Remote optical control of an optical flip-flop

We experimentally demonstrate control of a holding-beam-enabled optical flip-flop by means of optical signals that act in a remote fashion. These optical-control signals vary the holding-beam power by means of cross-gain modulation within a remotely located semiconductor optical amplifier (SOA). The power-modulated holding beam then travels through a resonant-type SOA, where flip-flop action occurs as the holding-beam power falls above and below the switching thresholds of the bistable hysteresis. Control is demonstrated using submilliwatt pulses whose wavelengths are not restricted to the vicinity of the holding beam. Benefits of remote control include the potential for controlling multiple flip-flops with a single pair of optical signals and for realizing all-optical control of any holding-beam-enabled flip-flop.     

Stable optical trapping based on optical binding forces

Various trapping configurations have been realized so far, either based on the scattering force or the gradient force. In this Letter, we propose a new trapping regime based on the equilibrium between a scattering force and optical binding forces only. The trap is realized from the interaction between a single plane wave and a series of fixed small particles, and is efficient at trapping multiple free particles. The effects are demonstrated analytically upon computing the exact scattering from a collection of cylindrical particles and calculating the Lorentz force on each free particle via the Maxwell stress tensor.     

Fiber optical parametric amplifiers in optical communication systems

The prospects for using fiber optical parametric amplifiers (OPAs) in optical communication systems are reviewed. Phase‐insensitive amplifiers (PIAs) and phase‐sensitive amplifiers (PSAs) are considered. Low‐penalty amplification at/or near 1 Tb/s has been achieved, for both wavelength‐ and time‐division multiplexed formats. High‐quality mid‐span spectral inversion has been demonstrated at 0.64 Tb/s, avoiding electronic dispersion compensation. All‐optical amplitude regeneration of amplitude‐modulated signals has been performed, while PSAs have been used to demonstrate phase regeneration of phase‐modulated signals. A PSA with 1.1‐dB noise figure has been demonstrated, and preliminary wavelength‐division multiplexing experiments have been performed with PSAs. 512 Gb/s have been transmitted over 6,000 km by periodic phase conjugation. Simulations indicate that PIAs could reach data rate x reach products in excess of 14,000 Tb/s × km in realistic wavelength‐division multiplexed long‐haul networks. Technical challenges remaining to be addressed in order for fiber OPAs to become useful for long‐haul communication networks are discussed.

     

Generation of optical vortices in multihelical optical fibers

It is theoretically demonstrated that multihelical fibers are capable to change the topological charge of the incoming field by l units in the transmitted and reflected light. The magnitude of the change in the topological charge coincides with the number of coaxial helicoids forming the fiber core. This can be used in designing generators of optical vortices (OVs) from Gaussian beams: broadband ones in transmitted light and narrowband ones in reflected light.     

Active optical compensation of low-quality optical system aberrations

We describe a method for the correction of slowly varying wavefront aberrations of low-quality telescope mirrors by using a DM in an active optical compensation system. Our goal is to reduce the surface wavefront error of low-cost multimeter-diameter mirrors from approximately 10 waves peak-to-valley (P-V), at a 1 microm wavelength, to approximately 1 wave or less. In a proof-of-concept demonstration using a 0.3m telescope at a wavelength of 633 nm, the rms wavefront error improved to 0.05 waves (0.26 waves P-V) from the original value of 1.4 waves rms (6.5 waves P-V). The Strehl ratio improved to 89% from the original value of 0.08%. The types of aberrations corrected include astigmatism, coma, defocus, trefoil, and higher-order aberrations.     

Ultra-short optical pulse shaping using semiconductor optical amplifier

Optical ultra-short pulse compression and amplification using semiconductor optical amplifier (SOA) is presented. Using pump-probe pulse configuration, we present an SOA model which includes the nonlinear effects such as, spectral hole burning (SHB), carrier heating (CH), two-photon absorption (TPA) and group velocity dispersion (GVD) taking into account gain spectrum effect. Then by adjusting time delay between the pump pulse and probe pulse we use the model for simultaneous compression and amplification of probe pulse. We also analyze the four wave mixing (FWM) signal during pulse compression process. It is shown that dispersive effect of GVD on output probe pulse becomes more important for larger cavity length and probe-pump pulses relative time delays.     

High-speed optical signal processing using semiconductor optical amplifiers

The authors report on all-optical switching devices based on semiconductor optical amplifiers (SOA) in applications for optical time division multiplexing (OTDM) transmission technology. The report includes a discussion on the basic properties of an SOA, on the nonlinear processes of cross-phase modulation and four-wave mixing in the SOA used for all-optical switching, and on the application of the SOA as demultiplexer, add-drop multiplexer, clock recovery and wavelength converter. The devices considered here operate at data rates in excess of \Gb80, where electrical signal processing is not available today.     

Three-dimensional optical profilometry using a four-core optical fibre

This paper describes the use of a four-core optical fibre for measurements of three-dimensional rigid-body shapes. A fringe pattern, which is generated by interference of four wavefronts emitted from the four-core optical fibre, is projected on an object's surface. The deformed fringe pattern containing information of the object's surface topography is captured by a digital CCD camera and is analysed using a two-dimensional Fourier transform profilometry. It is demonstrated for the first time that the use of such a four-core optical fibre increases the compactness and the stability of the fringe projection system.     

Twisted optical fibers sustaining propagation of optical vortices

The mode structure (the orbital number l = 1) of a few-mode weakly guiding optical fiber with high linear birefringence and a regular twist of its anisotropy axes is investigated. It is shown that, for certain values of twist pitch, the modes with l = 1 are almost pure linearly polarized optical vortices in the local coordinate system associated with the anisotropy axes. The range of values of twist pitch in which twisted fibers sustain propagation of linearly polarized optical vortices is determined numerically.     

All optical latches using quantum-dot semiconductor optical amplifier

The design and performance of two optical latches, the Set-Reset (SR) latch and D-Flip-Flop has been studied. These latches are the building blocks of large optical processors. The latches are built using two optical logic operations NAND and NOT. Both NAND and NOT operations are realized by using Mach-Zhender interferometer (MZI) utilizing semiconductor optical amplifier with quantum dot active region (QD-SOA). Nonlinear dynamics including carrier heating and spectral hole-burning in the QD-SOA are taken into account together with the rate equations in order to realize the all-optical logic operations. Results show that this scheme can realize the functions of Set-Reset latch and D-Flip-Flop at high speeds (∼250 Gb/s). The dependence of the output quality (Q factor) on QD-SOA parameters is also discussed.     

Experimental demonstration of tunable multiple optical orthogonal codes sequences-based optical label for optical packets switching

In this paper, the tunable multiple optical orthogonal codes sequences (MOOCS)-based optical label for optical packet switching (OPS) (MOOCS-OPS) is experimentally demonstrated for the first time. The tunable MOOCS-based optical label is performed by using fiber Bragg grating (FBG)-based optical en/decoders group and optical switches configured by using Field Programmable Gate Array (FPGA), and the optical label is erased by using Semiconductor Optical Amplifier (SOA). Some waveforms of the MOOCS-based optical label, optical packet including the MOOCS-based optical label and the payloads are obtained, the switching control mechanism and the switching matrix are discussed, the bit error rate (BER) performance of this system is also studied. These experimental results show that the tunable MOOCS-OPS scheme is effective.     

数字光开关网络中四功能交换开关光学Omega网络

本文提出了一种用于数字光开关网络中，四功能交换开关光学Ｏｍｅｇａ网络。文中详细地阐述了用液晶空间光调制方法实现光学四功能交换开关，和Ｏｍｅｇａ互连网络的原理，并给出了光学系统和实验结果。     

光纤通信光开关的物理基础

光开关是光交换系统的基本元件，也是一种基本的控光器件，本文综述了目前光纤通信中所研究和开发的光通信开关器件的物理原理，并给出各类光开关的阈值条件和典型参量。     

光纤通信光开关的物理基础(续)

3.2　定向耦合器电光开关定向耦合器电光开关是在电光材料 (如L i Nb O3、化合物半导体、有机聚合物 )的衬底上制作 1对条形波导和 1对电极构成 ,如图 5所示 .当不加电压时 ,它是 1个具有 2条波导和 4个端口的定向耦合器 .一般称 1 -3和 2 -4为直通臂 ,1 -4和 2 -3为交叉臂 .图 5　定向耦合器型光开关假设两波导的耦合较弱 ,各自保持独立存在时的场分布和传输系数 ,耦合的影响只表现在场的振幅随耦合长度的变化 .设两波导中的复数振幅分别为 E1(z)和 E2 (z) ,相位常量是β1和 β2 ,其变化规律可用一阶微分方程组表示 [3]d E1(z)dz =-ik12…