We experimentally demonstrate a cost-effective coherent 10 Gb/s system for passive optical networks, exploiting off-the-shelf DFB lasers and a phase-diversity receiver based on a simple 3 & times; 3 fiber coupler. Since the system uses a simple amplitude-shift keying format, no complex electronic processing is required and there is no need of frequency/phase stabilization of the local oscillator, whose frequency can change by more than & plusmn;1 GHz with no significant performance variation. The system has a 40 dB loss budget and is, therefore, compatible with the high losses of practical optical distribution networks, where power splitting is used to distribute the signal to a high number of users. Error-free 10-Gb/s transmission at the FEC limit is obtained after transmission over up to 66 km of G.652 single mode fiber. Polarization-independent operation is also demonstrated with a simple modification of the detection scheme, without duplicating components, and with a small variation of the sensitivity. The limited complexity indicates the potential for a cost-effective implementation, which makes it compatible with the strictly cost-Aware access networks environment, even for high-end services

A 1.25-Gb/s ASK passive optical network (PON) system with a -51 dBm pre-FEC sensitivity (at BER = 2 × 10-3) is enabled by a real-time polarization-independent coherent receiver (PI-RX) that needs no DSP (nor ADC). The receiver, which only makes use of common DFBs and commercially available electronic ICs, is targeted for use on a 6.25-GHz UD-WDM grid and has a 52-dB dynamic range. Measurements of the robustness of the PI-RX against backreflections and crosstalk from coexistent adjacent channels show that this preliminary implementation is suitable for UD-WDM-PON systems with frequency spacing down to 5 GHz

We experimentally demonstrate an innovative Ultra Dense Wavelength Division Multiplexing (UDWDM) Passive Optical Networks (PON) that implements the full λ-to-the-user concept in a filterless distribution network. Key element of the proposed system is a novel class of coherent transceivers, purposely developed with a non-conventional technical approach. Indeed, they are designed and realized to avoid D/A-A/D converter stages and Digital Signal Processing (DSP) in favor of simple analog processing so that they match system, cost and power consumption requirements of the access networks without sacrificing the overall performance. These coherent transceivers target different use case scenarios (residential, business, fixed, wireless) still keeping perfect compatibility and coexistence with legacy infrastructures installed to support gray, Time Division Multiplexed (TDM) PON systems. Moreover, the availability of coherent transceivers of different cost/performance ratios allows for deployments of different quality service grades. In this paper, we report the successful field trial of the proposed systems in a testbed where 14 UDWDM channels (and one legacy E-PON system) are transmitted simultaneously in a dark-fiber network deployed in the city of Pisa (Italy), delivering real-time and/or test traffic. The trial demonstrated filterless operations (each remote node selects individually its own UDWDM channel on a fine 6.25 GHz grid), real-time GbE transmissions (by using either fully analog or light digital signal processing), multirate transmission (1.25 and 10 Gb/s/), high Optical Distribution Network loss (18 ÷ 40 dB) as well as a bidirectional channel monitoring system.

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We report enhanced 10 Gb/s operation of directly modulated bandwidth-limited reflective semiconductor optical amplifiers. By using a single suitable arrayed waveguide grating we achieve simultaneously WDM demultiplexing and optical equalization. Compared to previous approaches, the proposed system results significantly more tolerant to seeding wavelength drifts. This removes the need for wavelength lockers, additional electronic equalization or complex digital signal processing. Uniform C-band operations are obtained experimentally with < 2 dB power penalty within a wavelength drift of 10 GHz (which doubles the ITU-T standard recommendations).