Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

http://ieeexplore.ieee.org/iel5/3/23094/01073023.pdf

Statistical optics

Broadband and low loss capability of photonics has led to an ever-increasing interest in its use for the generation, processing, control and distribution of microwave and millimeter-wave signals for applications such as broadband wireless access networks, sensor networks, radar, satellite communitarians, instrumentation and warfare systems. In this tutorial, techniques developed in the last few years in microwave photonics are reviewed with an emphasis on the systems architectures for photonic generation and processing of microwave signals, photonic true-time delay beamforming, radio-over-fiber systems, and photonic analog-to-digital conversion. Challenges in system implementation for practical applications and new areas of research in microwave photonics are also discussed.

Microwave Photonics

Microwave photonics is an area that studies the generation, processing, control and transmission of microwave signals by means of photonics. In this paper, microwave photonics techniques developed in the past few years will be reviewed, with an emphasis on system architectures for microwave applications.

http://ieeexplore.ieee.org/iel5/6305327/6320324/06320333.pdf

Microwave photonics

The investigation of nonlinear wave phenomena has been one of the main direc tions of research in optics for the last few decades. Soliton concepts applied to the description of intense electromagnetic beams and ultrashort pulse propagation in various media have contributed much to this field. The notion of solitons has proved to be very useful in describing wave processes in hydrodynamics, plasma physics and condensed matter physics. Moreover, it is also of great importance in optics for ultrafast information transmission and storage, radiation propagation in resonant media, etc. In 1973, Hasegawa and Tappert made a significant contribution to optical soliton physics when they predicted the existence of an envelope soliton in the regime of short pulses in optical fibres. In 1980, Mollenauer et al. conducted ex periments to elucidate this phenomenon. Since then the theory of optical solitons as well as their experimental investigation has progressed rapidly. The effects of inhomogeneities of the medium and energy pumping on optical solitons, the interaction between optical solitons and their generation in fibres, etc. have all been investigated and reported. Logical devices using optical solitons have been developed; new types of optical solitons in media with Kerr-type nonlinearity and in resonant media have been described.

Optical Solitons

Publisher Summary Polarization mode dispersion (PMD) is a linear effect that can be compensated in principle. In an ideal circularly symmetric fiber, the two orthogonally polarized modes have the same group delay. However, in reality, fibers exhibit a certain amount of birefringence because of imperfections in the manufacturing process or mechanical stress on the fiber after manufacture. It is noted that fluctuations in the polarization mode and fiber birefringence produced by the environment lead to dispersion that varies statistically with time and frequency. PMD causes different delays for different polarizations and when the difference in the delays approaches a significant fraction of the bit period, it leads to pulse distortion and system penalties. Environmental changes— including temperature and stress—cause the fiber PMD to vary stochastically in time. PMD, illustrating the basic concepts, the measurement techniques, the PMD measurement, the PMD statistics for first- and higher orders, the PMD simulation and emulation, the system impairments, and the mitigation methods has been summarized in the chapter. Both the optical and the electrical PMD compensations are considered.

Polarization-Mode Dispersion

In this paper, the phase-noise performance of optically generated electrical signals based on external optical modulation techniques is investigated theoretically and experimentally. Mathematical models are developed to represent perturbations on the transmitted optical signal caused by the phase fluctuations of the electrical drive signal applied to the external modulator and the optical carrier that feeds the external modulator. Closed-form expressions of the power spectral density (PSD) for the electrical signals, generated both locally and remotely, are derived. The calculated PSD of the locally generated electrical signal indicates that its phase noise is determined only by the phase noise of the electrical drive signal. The PSD of the remotely generated signal shows that its spectral quality is also affected by the chromatic dispersion of the fiber and the optical carrier linewidth. An experimental setup that can generate a millimeter-wave (mm-wave) signal, continuously tunable from 32 to 60 GHz using an electrical drive signal tunable from 8 to 15 GHz, is built. The spectra of the generated millimeter-wave signal are measured for both locally and remotely generated electrical signals, with optical carriers of different linewidths. The theoretical results agree with the experimental measurements

Phase-Noise Analysis of Optically Generated Millimeter-Wave Signals With External Optical Modulation Techniques

We propose and demonstrate a novel and simple predistortion circuit using reflective antiparallel diodes for linearization of electro-absorption modulators (EAMs) in multiband orthogonal frequency-division multiplexing (MB-OFDM) ultra-wideband (UWB) radio-over-fiber systems for UWB signals from 3.1 to 4.8 GHz. In this novel predistortion circuit, neither amplifiers, nor phase shifters are used, while only two antiparallel connected diodes are used, and the predistortion signal is adjusted by tuning the diodes' dc-bias current. The simple architecture makes the circuit cost effective and suitable for UWB system applications. By adding the predistortion circuit before the EAM, more than 7-dB suppression in third-order intermodulation distortion and 11-dB improvement in spurious-free dynamic range are achieved over the frequency range of 3.1-4.8 GHz, i.e., bandgroup 1 of MB-OFDM UWB. Correspondingly, 1-dB improvement in error vector magnitude is obtained experimentally when the designed predistortion circuit is used.

A Novel Analog Broadband RF Predistortion Circuit to Linearize Electro-Absorption Modulators in Multiband OFDM Radio-Over-Fiber Systems

In this paper, we propose a novel millimeter-wave-band radio-over-fiber (RoF) system with a dense wavelength-division multiplexing (DWDM) bus architecture. Two lasers with a small wavelength difference, phase locked and polarization aligned, are allocated at a central station (CS) for connecting the CS and each base station (BS), one laser for transmitting and the other for detection (the remote local oscillator). For the conceptual illustration, we consider a DWDM RoF system with a channel spacing of 12.5 GHz and RF of /spl sim/30-GHz millimeter-wave band. In the downlink system, a single-sideband (SSB) subcarrier is used with low RF imposed on an optical carrier at the CS, and an millimeter-wave-band RF signal is obtained at each BS using direct photodetection by the SSB subcarrier beat with the remote oscillator. In the uplink system, the received millimeter-wave-band RF signal at each BS is imposed on the two optical carriers simultaneously, one optical carrier with the closest SSB subcarrier is optically filtered out and fed into in the uplink transmission fiber without frequency interleaving; the electrical signal with a low IF can be photodetected directly at the CS. Such an RoF system has simple, cost-effective, and maintenance-reduced BSs, and is immune to laser phase noise in principle.

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A novel millimeter-wave-band radio-over-fiber system with dense wavelength-division multiplexing bus architecture

A compact disc ultrawideband (UWB) antenna with quintuple band rejections is proposed and demonstrated, which has a portrait shape and is therefore “portrait antenna.” The quintuple band-notched functions are achieved by utilizing C-shaped slots, nested C-shaped slots, U-shaped slots, and open-circuit stubs. It is demonstrated that the portrait antenna operating from 2.45 to 12 GHz (VSWR ; 2) of 3.27-3.57, 5.01-5.45, 5.55-6.05, 7.05-7.45 and 7.83-8.19 GHz are implemented simultaneously for rejecting WiMAX, WLAN, downlink of X-band satellite communication, and ITU 8-GHz band signals. Moreover, the antenna has a simple structure and a compact size.

A Compact Disc UltrawideBand (UWB) Antenna With Quintuple Band Rejections

We propose and investigate a linearized optical single-sideband (OSSB) Mach-Zehnder modulator (MZM) for radio-over-fiber systems. The linearized MZM makes use of a dual electrode z-cut LiNbO3 MZM with linear polarizers placed before and after it, respectively. By carefully selecting the angles of the two linear polarizers, third-order intermodulation and second-order distortion can be suppressed significantly. More importantly, it will be shown that with this linearized modulator, not only can OSSB modulation be obtained, but also an improvement in spurious free dynamic range of 15 dB is achieved as compared to the conventional MZM.

Xiupu Zhang

Papers

Phase-Noise Analysis of Optically Generated Millimeter-Wave Signals With External Optical Modulation Techniques

A Novel Analog Broadband RF Predistortion Circuit to Linearize Electro-Absorption Modulators in Multiband OFDM Radio-Over-Fiber Systems

A novel millimeter-wave-band radio-over-fiber system with dense wavelength-division multiplexing bus architecture

A Compact Disc UltrawideBand (UWB) Antenna With Quintuple Band Rejections

Linearized Optical Single-Sideband Mach–Zehnder Modulator for Radio-Over-Fiber Systems