R.A. Griffin

Coherence coding for photonic code-division multiple access networks

We analyze a code-division multiple access technique where information is optically encoded by manipulating the coherence between a pair of transmitted signals. Key features are intrinsic security, operation of the receiver at only the bit rate of a single channel, and reconfiguration without switching optical delays, which are considerable advantages compared to previously proposed CDMA schemes. Experimental results demonstrating the basic operation of the scheme are presented. The performance limitations are calculated and novel implementations are proposed. >

Photonic code-division multiple-access communications

Abstract Photonic code-division multiple access schemes have been proposed since the 1970s. Although there are many published proposals for new coding schemes, there are many less experimental verifications of these schemes, even fewer reports of successful data transmission, and no commercial systems. We attempt to explain the key factors that have led to the current state-of-the-art. In so doing, we describe the fundamental principles of matched filtering and noise in photonic CDMA schemes. We survey important developments and show how various schemes are related. We review recent experimental advances and compare the published experimental and theoretical performance for different schemes. We discuss the current major issues and likeb future directions.

Photonic CDMA by coherent matched filtering using time-addressed coding in optical ladder networks

We investigate a photonic CDMA system based on coherent matched filtering in ladder networks, employing both time-spreading and selective interference to discriminate wanted from unwanted signals. A theory is presented for time-resolved pulses which takes account of arbitrary source coherence. We examine the key issues of optical source requirements and phase and polarization control of en/decoder networks. And demonstrate key concepts experimentally. The crosstalk-limited signal-to-noise ratio is shown to be much higher than previous, purely incoherent systems. CDMA systems using coherent matched filtering therefore offer renewed promise for practical high capacity, multigigabit/s, multiuser networks. >

Optical phase coding for code-division multiple access networks

An all-optical code-division multiple access (CDMA) network is presented which uses optical phase information to encode and decode transmitted data from a low-coherence source, using simple, compact, reconfigurable optical delay networks. The use of a master encoding network to provide a reference for the system is demonstrated experimentally, and examples of phase codes ensuring minimum interference between users are given.<<ETX>>

Demonstration of data transmission using coherent correlation to reconstruct a coded pulse sequence

An optical pulse sequence derived from a single pulse can be summed coherently by a delay network provided that delay lengths are strictly controlled. Coherent correlation was demonstrated experimentally, using an electronic feedback circuit to interferometrically stabilize fiber delay lengths. The potential for application to code-division multiple access (CDMA) networks is demonstrated by using coherent correlation to distinguish a data sequence from an incoherent background signal.<<ETX>>

Radio-over-fiber distribution using an optical millimeter-wave/DWDM overlay

We demonstrate an optical MM-wave/DWDM overlay using optical suppressed-carrier modulation to simultaneously upconvert multi-wavelength subcarriers to 35 GHz. Performance of the system is analyzed for radio-over-fiber distribution.

Broadband wireless systems and networks: an enabling role for radio–over–fibre

There has been a remarkable take up of wireless and mobile communications in recent years, such that in a number of countries the number of mobile phones now exceeds the number of fixed network connections. Alongside this, we are seeing dramatic growth in data on the network compared with voice: the so–called ‘data wave’. While much mobile network traffic is currently voice there is increasing use of the available data facilities with these now being enhanced (e.g. via evolution of the global system for mobile communications and subsequently the introduction of ‘third–generation’ systems such as the universal mobile telecommunications system). Accordingly, there is considerable interest and activity in the research community concerning possible technologies exploiting yet higher frequencies where truly broadband future wireless networks may be realized. This paper will review some of the technology options currently available or under examination for millimetre-wave broadband wireless networks and will go on to consider in some detail a specific example of ‘fixed-wireless’ technology synergies exploiting radio-over-fibre techniques to achieve flexible, reconfigurable broadband wireless networks.

System capacity for millimeter-wave radio-over-fiber distribution employing an optically supported PLL

We consider the performance of a hybrid radio-over-fiber distribution system with a remote phase-locked loop (PLL) providing the local oscillator for upconversion to millimeter (mm)-wave frequencies. The reference signal for the PLL is transmitted together with digitally modulated subcarriers over a fiber link, allowing centralization of radio processing. Through analysis and simulation, we identify the relationship between the phase noise requirement for the PLL and the data capacity of the fiber link. For a practical link, we provide an upper limit on system capacity for transmission of 16 quadrature amplitude modulation (QAM) subcarriers.

InP Mach–Zehnder Modulator Platform for 10/40/100/200-Gb/s Operation

We describe the design and performance of a wavelength-flexible modulator platform based on multiple quantum well epitaxy on InP. The Mach-Zehnder modulator platform provides high levels of performance in a compact footprint, is suitable for high volume manufacturing, and is compatible with integration of a tunable laser source. Applications spanning 10-, 40-, 100-, and 200-Gb/s transmission are described.

Miniaturized InP dual I&Q mach Zehnder modulator with full monitoring functionality for CFP2

A compact InP modulator chip is presented for 32Gbaud coherent transmission having high efficiency and linear EO response V2π<;5V and ER>25dB; and a full set of integrated waveguide detectors and phase-controls for testing, set-up and monitoring.