K.C. Reichmann

A spectrally sliced PON employing Fabry-Perot lasers

We investigate using Fabry-Perot lasers as the upstream transmitters in a wavelength-division-multiplexed passive optical network (WDM-PON). We demonstrate transmission of a 10-Mb/s signal through each port of a wavelength-grating router followed by 18 km of fiber using an uncooled Fabry-Perot laser. These signals could be subcarrier multiplexed together, so that each user would have a dedicated radio-frequency channel. Since Fabry-Perot lasers provide more output power than low-cost light-emitting diodes, this may enable deployment of WDM-PONs in areas where optical loss prohibits the use of other low cost optical sources. The bit-rate is limited by mode-fluctuations being converted into intensity noise when transmitted through the router.

End-to-end equalization experiments in amplified WDM lightwave systems

It is experimentally verified that signal-to-noise ratio equalization in amplified wavelength-multiplexed lightwave systems can be achieved by adjusting input optical signal powers according to a simple algorithm. The experiment involved four channels spaced by 2 nm transmitted through 550 km of fiber with the aid of eight erbium-doped optical amplifiers.<<ETX>>

An eight-wavelength 160-km transparent metro WDM ring network featuring cascaded erbium-doped waveguide amplifiers

We demonstrate an 8/spl times/2.5 Gb/s wavelength-division-multiplexing metropolitan ring network in which each network-sourced wavelength constitutes a distinct multiuser virtual ring. The rings four nodes feature erbium-doped waveguide amplifiers, which promise future integrability.

2.5 Gb/s transmission over 674 km at multiple wavelengths using a tunable DBR laser with an integrated electroabsorption modulator

We present a distributed Bragg reflector (DBR) laser/modulator photonic integrated circuit capable of transmission over 674 km of conventional fiber at 2.5 Gb/s. Transmission was performed at four wavelengths over a range of >4 nm. The bit error rate (BER) sensitivity achieved at each wavelength varied by less than 1.1 dB. These results produce a record bit rate-distance product at each wavelength of 1.7 Tb.km/s for monolithic transmitters through nondispersion shifted fiber. Such devices are ideal sources for multichannel wavelength-division-multiplexed (WDM) transmission systems.<<ETX>>

4-Gb/s heterodyne transmission experiments using ASK, FSK and DPSK modulation

An experimental heterodyne lightwave transmission system operating at 4 Gb/s is described. The optical sources were 1.5- mu m-wavelength DFB (distributed feedback) and DBR (distributed Bragg reflector) semiconductor lasers. ASK, FSK, and DPSK modulation formats were investigated; baseline receiver sensitivities of 175, 191, and 209 photons/bit, respectively, were achieved. Transmission experiments through up to 160 km of conventional single-mode fiber and up to 175 km of dispersion-shifted fiber are also reported.<<ETX>>

Spectral slicing in WDM passive optical networks for local access

Spectral slicing techniques can support point-to-point, point-to-multipoint, and multiple access applications in the local access network. With spectral allocation it enables operation of multiple independent networks on a common infrastructure, with partitioning of both services and quality of service.

Full-duplex optical transmission using self-heterodyne laser transceivers

The use of semiconductor diode lasers simultaneously as heterodyne receivers and lightwave transmitters in a full-duplex single optical fiber transmission system is reported. A transmission distance of 16 km, limited by Rayleigh backscattering, is obtained at a bit rate of 40 Mb/s for this simple system, which requires no optical couplers or photodiodes. The proposed operation is analogous to that of the so-called autodyne radio receiver in which the local oscillator circuit also performs the heterodyne mixing. The optical counterpart is called a self-heterodyne mixer and offers the same frequency selectivity and tunability as a conventional heterodyne detector but with reduced receiver complexity. In the self-heterodyne receiver, an optical signal to be detected is introduced directly into the lasing cavity by coupling the signal into the laser through an uncoated cleaved end facet. Changes in the optical cavity field, which result from interference between the lasing mode and the injected signal, modulate the rate of stimulated carrier recombination and thus produce a change in the injection current. This alternating current component is detected and amplified in the laser active region bias.<<ETX>>

Spectral filtering and dispersion penalties associated with broad-band sources in digital broadcast video delivery

Broadcast digital video with QPSK modulation has been delivered over WDM passive optical networks by using spectral slicing of broad-band sources such as LEDs. We compare a model for, and experimental measurements of, dispersion induced impairments in QPSK video transmission systems with broadband optical carriers. The model is a universal function of RF frequencies, PON fiber length, and source spectral width for any given spectral shape, and describes the functional form and major portion of the observed impairments. The system implications of spectral filtering for unamplified systems are also discussed.

Enhanced privacy in broadcast passive optical networks through the use of spectral slicing in waveguide grating routers

We have measured the ability of a third party to intercept upstream messages in both passive splitter-based and waveguide-grating router-based broadcast passive optical networks. Bit-error-rate (BER) measurements at 150 Mb/s indicate that privacy is enhanced by at least 14 dB in the router-based network, and will improve further with router developments.

Thermal characteristics of light-emitting diodes and their effect on passive optical networks

LEDs have been demonstrated in several new passive optical networks (PON) architectures which capitalize on their wide spectral emission. We show that, due to thermal properties, LEDs exhibit higher than expected output powers under RF subcarrier modulation and baseband packet modulation, leading to advantageous power budgets in PON applications.