Richard Wyatt

A 135-km 8192-Split Carrier Distributed DWDM-TDMA PON With 2

We present a hybrid dense wavelength-division-multiplexed time-division multiple access passive optical network (DWDM-TDMA PON) with record performance in terms of reach (135.1 km of which 124 km were field-installed fibers), number of supported optical network units (ONUs-8192) and capacity (symmetric 320 Gb/s). This was done using 32-, 50-GHz-spaced downstream wavelengths and another 32-, 50-GHz-spaced upstream wavelengths, each carrying 10 Gb/s traffic (256 ONUs per wavelength, upstream operated in burst mode). The 10 Gb/s downstream channels were based upon DFB lasers (arranged in a DWDM grid), whose outputs were modulated using a electro-absorption modulator (EAM). The downstream channels were terminated using avalanche photodiodes in the optical networks units (ONUs). Erbium-doped fiber amplifiers (EDFAs) provided the gain to overcome the large fiber and splitting losses. The 10 Gb/s upstream channels were based upon seed carriers (arranged in a DWDM grid) distributed from the service node towards the optical network units (ONUs) located in the users premises. The ONUs boosted, modulated, and reflected these seed carriers back toward the service node using integrated 10 Gb/s reflective EAM-SOAs (EAM-semiconductor optical amplifier). This seed carrier distribution scheme offers the advantage that all wavelength referencing is done in the well-controlled environment of the service node. The bursty upstream channels were further supported by gain stabilized EDFAs and a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation. The demonstrated network concept allows integration of metro and optical access networks into a single all-optical system, which has potential for capital and operational expenditure savings for operators.

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We report on a hybrid DWDM-TDM A optical access network that provides a route for integrating access and metro net- works into a single all-optical system. The greatest challenge in using DWDM in optical access networks is to precisely align the wavelength of the customer transmitter (Tx) with a DWDM wave- length grid at low cost. Here, this was achieved using novel tunable, external cavity lasers in the optical network units (ONUs) at the customers end. To further support the upstream link, a 10 Gb/s burst mode receiver (BMRx) was developed and gain-stabilized erbium-doped fiber amplifiers (EDFAs) were used in the network experiments. The experimental results show that 10 Gb/s bit rates can be achieved both in the downstream and upstream (operated in burst mode) direction over a reach of 100 km. Up to 32 × 50 GHz spaced downstream wavelengths and another 32 × 50 GHz spaced upstream wavelengths can be supported. A 512 split per wave- length was achieved: the network is then capable of distributing a symmetric 320 Gb/s capacity to 16384 customers. The proposed architecture is a potential candidate for future optical access net- works. Indeed it spreads the cost of the network equipment over a very large customer base, allows for node consolidation and integration of metro and optical access networks into an all-optical system.

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Recent developments in the photosensitivity of germania doped silica glass are reviewed. The cause and nature of the absorption band centered near 240 nm are discussed and possible structures for this defect are reported together with a summary of the proposed mechanisms for the UV index change. Experimental techniques for assessing the refractive index change are listed and this leads to a consideration of the effects of non-ideal grating formation. Mechanisms for enhancing the photosensitivity of fibers and germania doped silica films are assessed using a systematic study of the photosensitivity of fibers fabricated under the different techniques. Finally some of the possible applications for photosensitivity are briefly discussed.

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Abstract This paper reviews the current world-wide status of fibres based on the fluoride glass system for optical amplification, with particular emphasis on telecom applications. The key feature of fluorozirconate glasses, with the very long wavelength multiphonon edge, is the accompanying relatively low non-radiative decay rate of excited rare-earth dopant ions. This gives unique opportunities compared with the better known oxide glass systems. Amplifiers with high gains have been demonstrated at important wavelengths such as 0.8, 1.3 and 1.5 μm. Improvements to allow the fabrication of more efficient fibres are also discussed.

10 Gb/s Capacity

A DWDM-TDMA PON using carrier distribution with symmetric 320 Gb/s capacity is demonstrated over 124 km field-installed fibers. The upstream channels feature a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation, burst-mode EDFAs and integrated reflective SOA-EAMs.

Demonstration of a 32

A praseodymium doped fluoride fiber amplifier (PDFFA) exhibiting efficient operation in both the large- and the small-signal regimes is described. The amplifier, based on a high NA fluoride fiber, exhibited a maximum small-signal gain of 29 dB and a low-pump small-signal. efficiency of 0.13 dB/mW. In the saturated regime a maximum output power of 212 mW was achieved. In this format, the signal-out versus pump-in characteristic, exhibited a slope efficiency of 30%, representing the most efficient conversion from pump to signal yet reported. Detailed spectral characterization reveals small-signal gain in excess of 20 dB over a wavelength range of almost 50 nm and in excess of 100 mW of saturated output available over a 30-nm wavelength range. >

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The characteristics of a praseodymium-doped fluoride fiber amplifier (PDFFA) pumped using a high-power diode-pumped Nd:YLF laser operating at 1.047 mu m are described. High small signal gains (29.5 dB) and the highest saturated output yet reported for PDFFAs (250 mW) have been achieved using this commercial diode-pumped source. The spectral characteristics have also been examined in both the large and small signal regimes. It is concluded that there is no significant penalty associated with pumping PDFFAs in the long wavelength wing of their pump band, even though this pump wavelength is almost 40 nm away from the peak of the absorption band.<<ETX>>

512 Split, 100 km Reach, 2

Abstract Pr-doped fluorozirconate fibre with a Δn=0.047 has been fabricated. The LP11 cut-off was at 650 nm, the minimum loss was 0.08 dB/m and the fibre had a two-point-bending median strength of 2.96%. Configured as a power amplifier, a slope efficiency of 30% was obtained, giving 212 mW of output power at 1.30 μm when counter-directionally pumped with 900 mW of 1.10 μm light.

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Coherent optical communication systems became possible with development of the gas laser in the early 1960s. During the decade following development of the laser, Enloe and Rodda showed homodyne detection to be possible when they successfully phase-locked two gas lasers. DeLange and Dietrich showed that stable heterodyne detection was possible over an enclosed optical transmission path. However, not until the 1980s were optical waveguide and semiconductor laser technologies developed to the stage where they could be used for coherent optical fiber transmission.

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We demonstrate a DWDM-TDMA PON with symmetric 320 Gb/s capacity shared between 16384 customers. The upstream channels were tested in burst-mode and feature low-cost tuneable lasers, monolithically integrated SOA-EAMs, burst-mode EDFAs and a 10 Gb/s burst-mode receiver.