M. Rannello

Coherent PON system with high-sensitivity polarization-independent receiver and no ADC/DSP

A 1.25 Gb/s ASK PON system with -51dBm sensitivity (at BER=2-103) is enabled by a polarization-independent coherent receiver that needs no DSP (nor ADC). The system just uses common DFBs and commercial electronic devices and has 52 dB dynamic range.

10 Gb/s long-reach PON system based on directly modulated transmitters and simple polarization independent coherent receiver

We demonstrate a coherent 10 Gb/s PON system solution exploiting a direct modulated laser (DML) transmitter to obtain long reach (>100 km). The system exploits a simplified coherent receiver. This receiver, which is similar to the scheme that we recently proposed, had to be adapted to obtain polarization-independent operation with a chirped signal from a DML and is still based on simple optical and electrical components. Thanks to the combined use of coherent-RX and DML, the system achieves a link budget of 43 dB for 105 km transmission distance with no need of dispersion compensation. This makes it a cost-effective, simple, and robust solution for satisfying the increasing capacity request of access networks.

Polarization-Independent Coherent Real-Time Analog Receiver for PON Access Systems

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.

Hitless dynamic wavelength allocation in coherent WDM-PONs

We introduce a novel algorithm for real-time ONU activation (λ - assignment) and reconfiguration (λ - tuning) in WDM coherent PONs. The algorithm prevents service interruption of lighted channels and it is experimentally demonstrated by using real-time fully-analog coherent transceivers.

Field-trial of a λ-to-the-user high-budget PON using a novel class of low-cost coherent transceivers and compatible with EPON system operation

COCONUT project demonstrated an innovative DWDM Passive Optical Network implementing the full λ-to-the-user concept in a filterless distribution fiber network. We make use of an innovative class of coherent transceivers that exploit the advantages of coherent detection in terms of sensitivity and channel selectivity in a cost efficient manner. The different transceivers developed target different use case scenarios, showing perfect compatibility with legacy infrastructures installed. In this paper, we report the successful trial of the proposed system in a testbed where 4 different coherent transceivers (plus one legacy E-PON system) ran simultaneously, operating over 14 DWDM channels, in a dark-fiber network in the city of Pisa, delivering real-time and/or test traffic. The testbed demonstrated filterless operations, multi-rate transmission (from 1.25 to 10 Gb/s/λ), high ODN loss (18 – 40 dB) as well as a bi-directional channel monitoring system.

4×10 Gb/s coherent WDM-PON system over 110 km single mode fibre and with 55 dB ODN power budget

We experimentally show that, using simplified coherent detection and directly modulated DFB lasers, a 40 Gb/s (4×10 Gbit/s) WDM-PON system can be realized, providing a very high power budget (55 dB) and 110 km reach. This enhances currently considered NG-PON2 solutions, both in terms of reach and acceptable loss.

Hitless wavelength assignment in filterless optical access networks

Advantages offered by coherent detection systems in access networks are not limited to the increase of power budget due to the superior sensitivity. Channel selectivity is another intriguing feature offered by coherent systems that can be exploited to enable advanced system and network functionalities for access systems. Among them, we focus here on the implementation of filterless optical networks and network reconfiguration capabilities which might be required to satisfy dynamic load balancing requests and new terminal activations. We show that in the access domain these functionalities do not require DSP-aided coherent receivers, but can be easily realized by means of simpler, fully analogue real-time coherent terminals matching the access network low-cost paradigm. This paper discusses these concepts and how they can be experimentally implemented by using a novel wavelength allocation algorithm and real-time analogue coherent transceivers based on DFB lasers, whose wavelengths are tuned by a simple temperature control.