Manoj P. Thakur

Demonstration of Wireless Backhauling Over Long-Reach PONs

An IEEE 802.16e-2005 (WiMAX) compliant, long- reach passive optical network is demonstrated, focusing on the development of next generation optical access with transparent wireless backhauling. In addition to the extended feeder reach, a wavelength band overlay is used to enhance network scalability by maintaining passive splitting in the field and with some design modification at the optical line terminal and remote base station. Radio-over-fiber is used to minimize network installation and maintenance costs through the use of simple remote radio heads complemented by frequency division multiplexing to address individual base stations. The implementation of overlapping radio cells/sectors is also proposed to provide joint signal processing at wireless user terminals. Experimental measurements confirmed EVMs below -30 and -23 dB downstream and upstream, respectively, over fiber link lengths of up to 84.6 km. In addition, adjacent channel leakage ratio measurements demonstrated that a figure of -45 dB with 40 MHz subcarrier spacing, as specified by the standard, can be readily achieved.

Simple 60-GHz MB-OFDM Ultrawideband RoF System Based on Remote Heterodyning

A simple 60-GHz radio-over-fiber system employing a combination of uncorrelated optical heterodyning and envelope detection is proposed and experimentally demonstrated. At the central office, a multiband orthogonal frequency division multiplexing ultrawideband (MB-OFDM UWB) signal is used for the external modulation of a dual-arm Mach-Zehnder Modulator to generate an optical signal-sideband signal, which is then coupled with an unmodulated free-running continuous wave laser. Optical heterodyne mixing at the base station and envelope detection at the customer unit are utilized. The experimental results confirm that photonic millimeter-wave signal generation and detection can be achieved without the need for complex optical phase-locked loops and high-frequency microwave sources. As a proof of concept, successful transmission of a 3.84 Gb/s 16-QAM MB-OFDM UWB signal over 48-km standard single-mode fiber without chromatic dispersion compensation and a further 4-m wireless channel is experimentally demonstrated.

Investigation of a SMF-MMF Link for a Remote Heterodyne 60-GHz OFDM RoF Based Gigabit Wireless Access Topology

A simple single-mode fiber/multimode fiber (SMF-MMF) 60-GHz radio over fiber scheme using a conventional central launching technique at 1550 nm is proposed and experimentally evaluated. The system targets cost-efficient Gigabit wireless access using already installed indoor MMF fed by a passive optical network topology. A complete characterization of the composite SMF/MMF/SMF optical medium is presented, in terms of coupling loss, power stability, and chromatic and modal dispersion. A robust multiband orthogonal frequency-division multiplexing optical single-side-band technique, employing envelope detector scheme, is used as to address the performance limitations imposed by the simple SMF-MMF coupling scheme, chromatic dispersion degradation, and phase noise owing to ordinary long-wavelength lasers. A characterization of the system is performed and a 3.84-Gb/s transmission is demonstrated over a scheme including 17.5-km SMF and 250-m MMF.

Experimental performance analysis of MB-OFDM Ultra-Wideband Radio-Over-Fiber signals in the 60-GHz band using a commercially-available DFB laser

We present an experimental analysis of the performance of Multiband-Orthogonal Frequency Division Multiplexing (MB-OFDM) Ultra-Wideband (UWB) in the 60-GHz radio band distributed using Radio-Over-Fiber (RoF) techniques. To reduce cost, direct modulation of a commercially-available distributed feedback (DFB) laser is used with optical up-conversion achieved with a Mach-Zehnder modulator (MZM). The impact of various parameters including laser bias current, temperature, UWB drive power, local oscillator (LO) power, fiber transmission and the received optical power are investigated. System performance is evaluated at a bit rate of 3.84 Gb/s using Error Vector Magnitude (EVM) measurements as a performance metric. We evaluate the different effects of these parameters on system performance and demonstrate the optimum values and the limitations imposed in fiber distribution.

Wimedia-Defined, Ultra-Wideband Radio Transmission over Optical Fibre

We demonstrate combined wireless and optical fibre channel transmission of Wimedia- defined, MB-OFDM, UWB radio by directly modulation of 4.8GHz VCSELs. Range extension to 400m for multi-cell HDTV sharing is achievable with low-cost remote antenna units.

Spectrally Efficient WDM Nyquist Pulse-Shaped Subcarrier Modulation Using a Dual-Drive Mach–Zehnder Modulator and Direct Detection

High data transmission capacity is increasingly needed in shortand medium-haul optical communication links. Cost-effective wavelength division multiplexed (WDM) transceiver architectures, achieving high information spectral densities (ISDs) (>1 b/s/Hz) and using low-complexity direct detection receivers are attractive solutions for such links. In this paper, we assess the use of dual-drive Mach-Zehnder modulators (DD-MZMs), and compare them with in-phase quadrature (IQ)-modulators for generating spectrally-efficient single sideband Nyquist pulse-shaped 16-QAM subcarrier (N-SCM) modulation format signals. The impact of the extinction ratio (ER) of a modulator on the optical sideband suppression ratio (OSSR) was investigated for the SSB signals in WDM systems, together with the resulting impact on inter-channel crosstalk penalties. First, in back-to-back operation, an IQ-modulator with an ER of 30 dB and a DD-MZM with an ER of 18 dB were experimentally compared in a 6×25 Gb/s WDM system by varying the channel spacing. Following this comparison, 16 GHz-spaced 6×25 Gb/s WDM signal transmission was experimentally demonstrated using the DD-MZM. The experiment was performed using a recirculating loop with uncompensated standard single-mode fiber (SSMF) and EDFA-only amplification. The maximum achievable transmission distances for single channel and WDM signals were found to be 565 and 242 km, respectively, at a net optical ISD of 1.5 b/s/Hz. This is the first experimental comparison of such modulator types for SSB N-SCM signal generation and the highest achieved ISD using a DD-MZM in direct-detection WDM transmission.

Optical frequency tripling with improved suppression and sideband selection

A novel, optical dispersion tolerant millimetre-wave radio-over-fibre system using optical frequency tripling technique with enhanced and selectable sideband suppression is demonstrated. 3 dB RCE penalties for multichannel WiMax transport was recorded after 40 km of fibre.

Bi-directional, 480Mbps, ultra-wideband, radio-over-fibre transmission using a 1310/1564nm reflective electro-absorption transducer and commercially-available components

We present the first experimental demonstration of a bi-directional, reflective, electro-absorption transducer-based, 480 Mbps UWB-wireless/optical transmission system. A -21.4 dB error vector magnitude was observed over 1 km of single mode fibre.

A 2.5 Gb/s Edge-Detecting Burst-Mode Receiver for GPON Access Networks

We describe a 2.5 Gb/s burst-mode receiver featuring edge-detecting data recovery. A high-performance SiGe comparator and standard optical front-end combination removed all burst-format issues. Error-free performance was achieved in a 32 km radius GPON test-bed.

Graeco-Latin-routed, self-wrapping, FSR-interleaved, AWG-based access network

Feature Issue on Passive Optical Network Architectures and TechnologiesWe describe, to the best of our knowledge, a novel WDM-TDM switched access network architecture featuring cascaded 16×16 and 1×32 arrayed waveguide gratings (AWGs), such that the AWG free spectral ranges (FSRs) have been matched to provide cascaded, cyclical, Graeco-Latin-routing protocols for downstream and upstream routing. In particular, use of FSR-multiplexed wavelengths allows greatly reduced cross talk between upstream and downstream signals and also doubling of the available network bandwidth capacity, while maintaining the same N×N AWG in the central office. Alternatively, this allows significant increase in the number of end users served by the network. We provide theoretical and simulation studies of our bidirectional access network topology, and experimental proof of principal results. Three sets of simulations with data rates from 2.5, 5.0, and 10.0Gbits/s have been performed for downstream and upstream transmissions. For the experimental part, eight ITU wavelengths were multiplexed at the exchange point and successfully transmitted at 2.5Gbits/s for simultaneous bidirectional transmission. Bit-error-rate measurements show error-free transmission is achievable for both directions with minimal cross talk between the channels.