Y. Ben Ezra

Ultrafast All-Optical Processor Based on Quantum-Dot Semiconductor Optical Amplifiers

We have developed a theoretical model of an ultra- fast all-optical signal processor based on the Mach-Zehnder interferometer with quantum-dot semiconductor optical amplifiers in both its arms. It is shown that such a processor under different conditions may realize wavelength conversion, XOR logic operation, and optical 3R regeneration.

Ultra-Wideband Radio-Over-Optical Fiber Concepts, Technologies and Applications

We have developed novel ultra-wideband (UWB) radio-over-optical-fiber (UROOF) concepts and technologies for a number of important in-house applications characterized by a high data rate. We propose the novel components, architecture, and realization of UWB UROOF systems. We present new experimental results related to UWB signal up-conversion, photonic radio impulse generation, and digital and analog signal coexistence. We also discuss future trends in the field of UWB UROOF technologies.

Proposal for All-Optical Generation of Ultra-Wideband Impulse Radio Signals in Mach–Zehnder Interferometer With Quantum-Dot Optical Amplifier

We developed a theoretical analysis of a novel method of ultra-wideband impulse radio signals all-optical generation based on cross-phase modulation and cross-gain modulation in a nonsymmetric integrated Mach-Zehnder interferometer (MZI) containing quantum-dot semiconductor optical amplifier. The proposed method is promising due to the advantages of compact, easily controlled, and low energy integrated MZI structures as compared to optical fiber systems.

All-Optical Signal Processing for High Spectral Efficiency (SE) Optical Communication

© 2012 Lembrikov et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. All-Optical Signal Processing for High Spectral Efficiency (SE) Optical Communication

Up-Conversion of Triple-Band OFDM UWB Signals by a Multimode VCSEL

We present novel experimental results for the all-optical up-conversion of the triple-band orthogonal frequency-division-multiplexing ultra-wideband radio signals from lower frequency band group 1 up to higher frequency band groups 2 or 3 based on the vertical-cavity surface-emitting laser optical second- and third-order nonlinearities. Low conversion losses and error vector magnitude values, respectively, for low bias currents have been demonstrated.

All-optical memory based on quantum dot semiconductor optical amplifiers (QD-SOAs) for advanced modulation formats

We proposed a fast all-optical regenerative memory loop which can be used for pulse amplitude modulation (PAM). The ultra-fast all-optical memory loop is based on the Mach-Zehnder interferometer (MZI) with quantum dot (QD) semiconductor optical amplifier (SOA) in each arm. It can operate at bit rates up to 100 Gb/s due to the fast gain recovery typical for QD-SOA. We have carried out the numerical simulations of the proposed fast all-optical regenerative memory loop for the PAM 4 modulation format.

All Optical Generation and Processing of IR UWB Signals

1.1 Impulse Radio (IR) Ultra Wideband (UWB) Communications Ultra wideband (UWB) communication is a fast emerging technology that offers new opportunities such as high data rates, low equipment cost, low power, precise positioning capability and extremely low interference Ghawami (2005). A wide range of possible UWB communication system applications includes radars due to UWB ultra high precision ranging at the centimeter level, wireless personal area networks (WPAN), sensor networks, imaging systems, UWB positioning systems, etc. Yang (2004), Kshetrimayum (2009). From a commercial point of view, the high data rates are the most attractive feature of UWB systems for which speeds of over 100Mb/s have been demonstrated Ghawami (2005). There exist three main types of UWB technologies: impulse radio (IR UWB), direct sequence (DS UWB), and multi-band orthogonal frequency division multiplexing (MB OFDM) Ran (2009). IR UWB communication technique is essentially different from all other communication techniques because it is carrier free and uses for communication between transmitters and receivers very narrow radio frequency (RF) pulses generated from the UWB pulse generator, while traditional transmission systems transmit information by varying the power, frequency, and/or phase of a sinusoidal wave in a modulation process Kshetrimayum (2009), Yao (2007). Consequently, complicated frequency mixers and local oscillators for carrier frequency up and down conversion are not necessary Yao (2007). IR UWB modulation techniques are especially important because the UWB spectrum has been made available by the Federal Communication Commission (FCC) and it can be used with IRs developed to date Lin (2005). Waveforms for IR UWB are designed to obtain a flat frequency response over the bandwidth of the pulse and to avoid a DC component. The large spectrum of a UWB signal may interfere with existing users. In order to keep this interference to the minimum, FCC specifies spectral masks for different applications, i.e. the allowed power output for specific frequencies Ghawami (2005). A contiguous bandwidth of 7.5GHz is available in the frequency interval of (3.1− 10.6)GHz at a maximum power output of −41.3dBm/MHz which is considered as extremely low Ghawami (2005). The power spectral density (PSD) of UWB systems defined as a ratio of the transmitted power P in watts and a signal bandwidth B in hertz is extremely low as compared to other communication systems due to the very wide bandwidth B of short pulses that are typically of nanosecond or picosecond order Ghawami (2005). The selection of the impulse signal type for IR UWB communication system is essential since it determines

Experimental and theoretical investigation of the multiband OFDM ultra-wideband radio over multimode fiber transmission

A combined wireless and optical channel for multiband orthogonal frequency division multiplexing (MB OFDM) ultra-wideband (UWB) radio transmission has been investigated both experimentally and theoretically. The channel consists of a directly modulated vertical cavity surface emitting laser (VCSEL), wireless channel, ultra-wideband (UWB) antenna, multimode optical fiber (MMF) and a p-i-n diode as a photodetector (PD). It has been shown both experimentally and theoretically the advantages of the MB OFDM transmission through MMF. The transmission distance increases in such a case up to 750 m. Numerical simulations carried out in the framework of the developed model show a good accord with the experimental data.

New Approach to Ultra-Fast All-Optical Signal Processing Based on Quantum Dot Devices

Fiber-optic technology is characterized by enormous potential capabilities: huge bandwidth up to nearly 50Tb/s due to a high frequency of an optical carrier, low signal attenuation of about 0.2dB/km, low signal distortion, low power requirement, low material usage, small space requirement, and low cost Agrawal (2002), Mukherjee (2001). However, the realization of these capabilities requires very high-bandwidth transport network facilities which cannot be provided by existing networks consisting of electronic components of the transmitters and receivers, electronic switches and routers Agrawal (2002). Most current networks employ electronic signal processing and use optical fiber as a transmission medium. Switching and signal processing are realized by an optical signal down-conversion to an electronic signal, and the speed of electronics cannot match the optical fiber bandwidth Ramamurthy (2001). For instance, a single-mode fiber (SMF) bandwidth is nearly 50Tb/s, which is nearly four orders of magnitude higher than electronic data rates of a few Gb/s Mukherjee (2001). Typically, the maximum rate at which a gateway that interfaces with lower-speed subnetworks can access the network is limited by an electronic component speed up to a few tens of Gb/s. These limitations may be overcome by the replacement of electronic components with ultra-fast all-optical signal processing components such as fiber gratings, fiber couplers, fiber interferometers Agrawal (2001), semiconductor optical amplifiers (SOAs) Dong (2008), Hamie (2002), SOA and quantum dot SOA (QD-SOA) based monolithic Mach-Zehnder interferometers (MZIs) Joergensen (1996), Wang (2004), Sun (2005), Kanellos (2007), Wada (2007), Ben-Ezra (2008), Ben-Ezra (2009), all-optical switches based on multilayer system with enhanced nonlinearity and carbon nanotubes Wada (2007). SOAs are among the most promising candidates for all-optical processing devices due to their high-speed capability up to 160Gb/s , low switching energy, compactness, and optical integration compatibility Dong (2008). Their performance may be substantially improved by using QD-SOAs characterized by a low threshold current density, high saturation power, broad gain bandwidth, and a weak temperature dependence as compared to bulk and multi-quantum well (MQW) devices Bimberg (1999), Sugawara (2004), Ustinov (2003). High-speed wavelength conversion, logic gate operations, and signal regeneration are important operations of the all-optical signal processing where SOAs are widely used Agrawal (2002), Ramamurthy (2001), Dong (2008). A wavelength converter (WC) changes the input wavelength to a new wavelength without modifying the data content of a signal Agrawal (2002). Wavelength conversion is essential for optical wavelength division multiplexing (WDM) network operation Ramamurthy (2001). 18

Applications of quantum dot (QD) lasers in optical communications for datacenters

Optical communication technologies are the best solutions for the high-performance computing infrastructures (HPCs) and datacenter networks (DCNs). All-optical approach consists of switching all data at the packet in the optical domain which requires data rates higher than 100 Gbit/s. The quantum dot (QD) lasers are the promising candidates for such applications due to their high operation rates, light generation at the wavelengths of 1.33 µm and 1.55 µm, and low injection currents. We investigated theoretically the modulation process of the optically injected QD laser placed in a DCN for advanced modulation format PAM-4. The numerical simulation results show that the DCN performance significantly improves due to the optical synchronization of the QD laser carrier dynamics.