Aeneas B. Massara

Physical layer strategies for 10 gigabit Ethernet

This paper reviews some of the options and key challenges that are currently being considered for local area network upgrades to operating speeds of 10 Gb/s, focussing on the 10 Gigabit Ethernet standard. In particular, technologies including serial, wavelength division multiplexing and parallel optics are discussed. In addition work being currently carried out on uncooled serial links at the University of Bristol is highlighted within this context. Finally, methods including subcarrier multiplexing and multilevel coding schemes are described that may also be suitable for high bandwidth computer interconnects.

10-Gbit/s transmission over 300-m standard multimode fiber using multilevel coding and 2-channel WDM

Summary form only given.This paper shows that the combination of multilevel coding schemes and simple 2-channel WDM at 1300 and 1550 nm could be used to transmit an aggregate of 10 Gbit/s over 300 m of multimode fiber that is typical of that employed in current LANs. This technique could be a simple solution for achieving 10 Gigabit Ethernet links over installed multimode fiber building backbones.

Uncooled, 10 Gb/s operation of two-contact InGaAsP lasers with low drive current

Uncooled, high-speed modulation of two-contact lasers is presented with ultra-low drive currents. Practical operation at 10 Gb/s up to temperatures of 85/spl deg/C and extinction ratios of 6 dB are found for current swings which are less than 40% of conventional lasers.

Investigation of 2-D-lattice distributed reflector lasers

The introduction of a deep-etched hexagonal lattice of round holes around a short section of the ridge waveguide of a Fabry-Perot laser can be used to create single-mode lasers suitable for high-speed data communications. A detailed characterization of the operating characteristics of the two-dimensional-lattice laser is presented. In addition, modeling of gain, reflectivity, and waveguide properties is used to explain experimentally observed results.

Ridge waveguide 1.55-μm DFB lasers with uncooled 10-Gb/s operation at 55° C

Uncooled direct modulation of a 1.55 micrometers distributed feedback (DFB) laser is demonstrated at 10 Gbit/s is demonstrated. The small signal performance of the laser at 25 degree(s)C gives rise to a -3 dB bandwidth in excess of 9 GHz, reducing to 8 GHz at 55 degree(s)C. Under uncooled, direct modulation at 10 Gbit/s the back-to-back eye diagrams obtained at temperatures up to 55 degree(s)C are found to be open, with extinction ratios of 6 dB for a peak-to-peak current swing of 40 mA. Transmission at 10 Gbit/s over standard singlemode fiber, is demonstrated over 12 km with the uncooled device. Using this device, multi-level coding is demonstrated at 20 Gb/s, and transmission at 5 Gb/s over 700 m of multi-mode fiber at 60 degree(s)C.

Novel athermal WDM laser with polymer grating

In this work we propose and fabricate a novel low cost wavelength stable single mode laser for uncooled WDM applications using hybrid semiconductor-polymer diode structures. A ridge waveguide Fabry-Perot laser with an integrated spot size convertor on the output is modified for athermal single frequency operation. The prototype device consists of an active section and an athermalized polymer grating structure. The latter is etched by focused ion beam (FIB) and filled with a negative temperature coefficient polymer material to compensate thermal wavelength drift. The active region thermal drift is thereby partially compensated by the polymer grating without requiring active wavelength or temperature control. This potentially facilitates low-cost, low-footprint, low-power-consumption packaging.

Eye-opening lattice work

The 2-D lattice laser is a promising low-cost device for high-speed optical data communications applications.

Mode beating in spot-size converter lasers

An anomalous modulation in the wavelength spectrum has been observed in lasers with spot-size converters. This intensity modulation is shown to be caused by beating between the fundamental lasing mode and radiation modes in the taper. This results in a periodic modulation in the net gain spectrum, which causes wavelength jumps between adjacent net gain maxima, and a drive current dependent spectral width that is expected to affect system performance. The amplitude of this spectral modulation is reduced significantly by either using an angled rear-facet which reflects the beating radiation modes away from the laser axis, or by using a nonlinear, adiabatic taper.

High coupling in novel 2D-lattice distributed reflector laser gratings

It is shown that 2D lattice gratings, despite being placed outside the waveguide region, exhibit sufficiently strong coupling coefficients that optical modes rapidly. couple transversely into the etched grating region, yielding high coupling coefficients of 270 cm/sup -1/. This performance allows mode-hop-free lasing operation in DBR structures.

Performance of single mode laser components using 2D photonic lattice reflectors

This paper will report studies of the placement of 2D photonic gratings on either side of the ridge in a Fabry Perot laser device in order to cause single mode emission. Using this approach, side mode suppression ratios of up to 30 dB are achieved, the emission remaining single mode even under 10 Gb/s large signal modulation. It is found that the use of the grating not only causes spectrally dependent reflection but in addition can lead to transverse mode fluctuations. The action of the grating has been studied not just in terms of its edge emission where conversion of the transverse modes is achieved, but also through measurement of the vertical emission from the structure where strong filtering action is observed.