Chin-Pang Liu

High-Dynamic-Range Wireless-Over-Fiber Link Using Feedforward Linearization

We demonstrate the implementation of feedforward linearization at 5 GHz, which is the highest operating frequency yet reported, with 500-MHz linearization bandwidth having at least 24-dB distortion suppression. Simultaneous reduction of 26-dB third-order intermodulation distortion and 7-dB laser-noise reduction is achieved at 5.2 GHz, leading to enhanced spurious-free dynamic range of 107 dB (1 Hz) in a directly modulated uncooled semiconductor laser for applications in wireless-over-fiber (WoF) systems. This paper also provides detailed analysis on feedforward, theoretical distortion reduction, criteria for component selection, and the effect of dispersion. The effectiveness of feedforward in a multichannel system is demonstrated at 5.8 GHz for fixed wireless systems, such as WiMAX. These results suggest that the feedforward-linearization arrangement can make practical multichannel and multioperator WoF systems.

A single-stage three-terminal heterojunction bipolar transistor optoelectronic mixer

A high-conversion gain three-terminal heterojunction bipolar transistor (HBT) optoelectronic mixer has been demonstrated. The maximum obtained intrinsic conversion gain was 10.4 dB. The mixing performance was measured as a function of the dc bias of the device and local oscillator power level. A SPICE-based large signal model was employed to simulate the device. The main nonlinear effects which contributed to the mixing process were the voltage dependence of the dynamic emitter resistance, and the variation of the current gain in the saturation regime.

Two-terminal edge-coupled InP/InGaAs heterojunction phototransistor optoelectronic mixer

We report the first experimental results for optoelectronic mixing using a two-terminal edge-coupled InP/InGaAs heterojunction phototransistor (HPT). The HPT optoelectronic mixer (OEM) exhibits a maximum of 7-dB conversion gain relative to a 100% quantum efficient photodetector operated at the optical modulation frequency. We give a qualitative explanation for the observed conversion gain variation with the HPT bias voltage.

Transmission of Wireless MIMO-Type Signals Over a Single Optical Fiber Without WDM

The problem of sending multiple wireless signals of the same carrier frequency, such as the multiple-input-multiple-output (MIMO) signals specified in the IEEE 802.11n standard, over a single optical fiber is that they overlap in the frequency domain. Traditional solutions using wavelength division multiplexing or even deploying multiple optical fibers are, however, far too expensive for this particular application. We propose and demonstrate transmission of three MIMO radio signals all with a 11-MSymb/s, 16 quadrature amplitude modulation, and 2.44-GHz carrier frequency over an optical fiber using a novel single-sideband frequency-translation technique. The maximum crosstalk level between the different MIMO channels was . Compared with sub-carrier multiplexing, where transmitting three such signals would require frequency shifting two of them using two separate local oscillators (LOs), the new technique requires only a single low-frequency LO. This novel technique can be implemented in add-on modules to work with existing commercially available radio-over-fiber systems, which were not originally designed to carry such MIMO signals having the same frequency.

Full-duplex DOCSIS/WirelessDOCSIS fiber-radio network employing packaged AFPM-based base-stations

The simultaneous wireline (600 MHz) and wireless (5.5 GHz) transmission of data over cable service interface specification (DOCSIS) signals in a hybrid fiber-radio access network is presented. The DOCSIS signal wireless replica is generated by means of an optical harmonic up-conversion technique based on a dual-drive Mach-Zehnder modulator. The optical signal is fed to a base station (BS) where a packaged asymmetric Fabry-Pe/spl acute/rot modulator/detector acts simultaneously as a photodetector and an optical modulator. At the BS, the DOCSIS signals can be fed either to a wireline or a wireless access network, in a highly flexible approach. Full-duplex operation has been demonstrated for both access types, including indoor wireless transmission.

Full-Duplex DOCSIS/WirelessDOCSIS Fiber–Radio Network Employing Packaged AFPMs as Optical/Electrical Transducers

A hybrid fiber-radio access network architecture for simultaneous wireline and wireless transmissions of data-over-cable service interface specification (DOCSIS) signals is presented. An all-optical harmonic up-conversion technique using a dual-drive Mach-Zehnder modulator provides the downstream optical signal modulated not only at the intermediate frequency in the 600- to 900-MHz band for wireline transmission but also at the up-converted frequency in the 5.45- to 5.75-GHz band for wireless transmission. An InGaAsP/InGaAsP multiple-quantum-well asymmetric Fabry-Perot modulator/detector has been designed, fabricated, and packaged and has been employed in the base station (BS) as an optical/electrical transducer, simultaneously providing the functions of optical intensity modulation and photodetection. At the BS, the DOCSIS signals are recovered at the wireline and wireless frequencies for the respective feeding of a cable access network or a fixed wireless access network in a highly flexible approach. Full-duplex operation has been demonstrated for both access types in an indoor laboratory environment. In a subsequent small-scale field trial, real-life Internet traffic provided by a local community antenna television system operator has been transported over the present hybrid fiber-radio access network architecture, and simultaneous transmission of both DOCSIS and digital television signals has also been performed.

A 65-km span unamplified transmission of 36-GHz radio-over-fiber signals using an optical injection phase-lock loop

We report generation and transmission of single side-band millimeter-wave modulated optical signals using a reference-modulated optical injection phase-lock loop. A 36-GHz 68-Mbit/s differential phase shift keyed signal is transmitted over a 65-km unamplified standard single-mode fiber using no dispersion compensation with a BER < 10/sup -9/.

Interchannel distortion suppression for broadband wireless over fibre transmission using feed-forward linearised DFB laser

We describe the first transmission of triple 11 Msymb/s QPSK channels over 2.2 km SMF using a feed-forward linearised uncooled DFB laser achieving 11 dB interchannel distortion suppression and 10.5 dB power advantage compared to the non-linearised case.

Multiple-quantum-well asymmetric Fabry-Perot modulators for microwave photonic applications

We describe the development of InGaAsP multiquantum-well asymmetric Fabry-Perot modulators (AFPM) for RF-over-fiber applications. Advantages of the AFPM include low drive voltage and loss, high linearity and simple fiber alignment. Experimental results of initial devices, exhibiting 5.5-dB modulation depth and >3-GHz operation, are described. The effect of the optical power on the device performance was assessed, and the modulation bandwidth was found to be unaffected by incident optical powers up to 0 dBm. The linearity of the modulation characteristic was measured by carrying out two-tone intermodulation distortion tests, and a third-order intercept point of 30 dBm was observed.

InGaAsP-based uni-travelling carrier photodiode structure grown by solid source molecular beam epitaxy

We report the first InGaAsP-based uni-travelling carrier photodiode structure grown by Solid Source Molecular Beam Epitaxy; the material contains layers of InGaAsP as thick as 300 nm and a 120 nm thick InGaAs absorber. Large area vertically illuminated test devices have been fabricated and characterised; the devices exhibited 0.1 A/W responsivity at 1550 nm, 12.5 GHz -3 dB bandwidth and -5.8 dBm output power at 10 GHz for a photocurrent of 4.8 mA. The use of Solid Source Molecular Beam Epitaxy enables the major issue associated with the unintentional diffusion of zinc in Metal Organic Vapour Phase Epitaxy to be overcome and gives the benefit of the superior control provided by MBE growth techniques without the costs and the risks of handling toxic gases of Gas Source Molecular Beam Epitaxy.