Fiber architecture solutions for providing wireless network coverage by radio-over fiber feeding in buildings
are discussed. The focus is on very high wireless data rate applications (>>100 Mb/s) with short wireless
distances (typ. <10m). Up to 20 Gb/s signal transmission at 60 GHz is demonstrated.
Fiber-radio systems based on directly modulated high-speed VCSELs are investigated at both 850 nm and 1300 nm.
Multimode fiber for short reach applications as well as single-mode fiber to bridge longer distances have been
demonstrated to show high performance. Laser noise and linearity characterization as well as system design to achieve
high spur-free dynamic range of >95 dB•Hz2/3 are discussed. A comparative study of radio signal transport solutions based
on fiber or coaxial cable is presented and the long transmission distances achievable over multimode fiber links presented.
A picocellular network demonstrator comprising of 14 cells with a 4 m radius to investigate networking issues was
developed and key performance results are presented.
InP-based vertical cavity surface emitting lasers (VCSELs) with AlGaInAs QWs and AlGaInAs/InP DBR have been
demonstrated. Over 3 mW and ~1 mW powers at both 1.3 μm and 1.55 μm have been achieved at 20 °C and 85 °C,
respectively. Tests for various applications have been performed with our 1.3 and 1.55 μm VCSELs. Error free
transmission over 10 km under 10 Gbit/s, 85°C has been demonstrated with both 1.3 and 1.55 μm VCSELs. The effect of
electrical dispersion compensation (EDC) with 1.55 μm VCSELs has been confirmed for transmission of medium range
data transmission. Radio signal transmission with low error vector magnitude by 1.3 μm VCSELs has been achieved at 2.4
and 5 GHz-band radio frequency.
We show through numerical simulation of 10.7-Gbits/s dense wavelength-division multiplexed (DWDM) duobinary transmission over 800 km of nonzero-dispersion-shifted fiber that uncompensated dispersion can introduce significant departures from Gaussian statistics in the receiver current.
An optical cell switch for interconnecting massively parallel nodes offers the potential for reduction in size, power consumption, and cost of high-performance computing (HPC) interconnects. We designed an architecture based on a broadcast and select approach that is highly flexible in terms of supported ports and can easily scale from a 16x16 to a 2048x2048 port switch by exploiting both wavelength multiplexing and fiber multiplexing. The optical system is designed for 40 Gb/s operation, but the full 160 Gb/s switching likely required of a commercial system can be supported by this architecture. At the core of the switch is an array of semiconductor optical amplifiers (SOAs), which provide fast switching (~1 ns), high extinction ratio (>40 dB) for cross-talk reduction, and optical gain (15 dB typical). The full optical switch consists of a 2-stage broadcast and select design for fiber select and color select, leading to a bufferless low-latency crossbar cell switch. A switch system demonstrator with 8 full optical paths has been implemented and used for performance characterization. A fast 40 Gb/s cell receiver was developed and proven to support up to 9 dB dynamic range. System demonstration measurements have shown that a raw BER of 10-15 is achievable. Optical cross-talk is negligible and does not degrade the system performance. The system design and verification experiments demonstrate that a scaleable 40 Gb/s switch for massively parallel systems is feasible and offers the potential for significant size, power consumption, and cost reduction by applying the scalability of an optical solution to a HPC system.
Dynamic dispersion compensation based on non-linear self-phase modulation (SPM) in an all-fiber device is demonstrated. The basic design of the compensator is very simple, consisting only of a pre-compensating negative dispersion fiber, an optical amplifier, and a highly non-linear positive dispersion fiber. Multiple channel operation of the compensator is feasible and experimentally demonstrated. An increase of dispersion tolerance of at least a factor of 2 is shown with low penalty of less than 2 dB. Finally, device performance in a 2000 km fiber loop experiment is presented.
A fast spectral power equalizer was designed and tested in a reconfigurable optical network testbed. Its response time is ~100 microseconds. Dynamic power fluctuation caused by add/drop switching in reconfigurable optical networks can be compensated by this technology.