Giuseppe Talli

Hybrid DWDM-TDM long-reach PON for next-generation optical access

A novel long-reach passive optical network (PON) architecture based on hybrid dense wavelength-division multiplexing (DWDM) and time-division multiplexing (TDM) is presented as a possible candidate for the next generation of optical access networks. The approach combines access and backhaul functions in a single optical network infrastructure that links end customers directly to core networks without the need for intermediate electronic conversions. A centralized optical carrier distribution and wavelength-independent remote modulation scheme is employed to avoid the potential inventory and deployment costs associated with the use of wavelength-specific lasers in the customer transmitter (TX). The customer TX is based on an electroabsorption modulator (EAM) monolithically integrated with two semiconductor optical amplifiers (SOAs), providing sufficient net gain and bandwidth to support large splitting factors and upstream bit rates up to 10 Gb/s. The experimental results reported show that the network, with a total reach of 100 km and an upstream bit rate of 10 Gb/s, can potentially support 17 TDM PONs operating at different wavelengths each with up to 256 customers, giving an aggregate number of 4352 customers in total.

Rayleigh noise mitigation in long-reach hybrid DWDM-TDM PONs

Feature Issue on Passive Optical Network Architectures and TechnologiesAn architecture employing a centralized light source and reflective modulator at the customer is proposed and demonstrated for a long-reach, hybrid dense wavelength division multiplexed (DWDM)-time-division multiplexed (TDM) passive optical network (PON). Impairments to the upstream channel caused by Rayleigh backscattering in the network are mitigated using a dual-feeder-fiber approach in conjunction with a novel detuned filtering and spectral-broadening scheme. The experimental results show that the network, with a total reach of 116km and an upstream bit rate of 10Gbits/s, can support up to 256 customers on each TDM PON. The potential performance improvements obtainable from an optimized architecture are also discussed.

Rayleigh Noise Reduction in 10-Gb/s DWDM-PONs by Wavelength Detuning and Phase-Modulation-Induced Spectral Broadening

A novel scheme for reducing Rayleigh beat noise in centralized light source dense wavelength-division-multiplexed passive optical networks is demonstrated using an optimized channel-detuned optical filtering of 30 GHz and phase-modulation-induced spectral broadening of a 10-Gb/s upstream nonreturn-to-zero (PM-NRZ) signal. The required optical-signal-to-Rayleigh-noise-ratio (OSRNR), characterized experimentally, can be reduced by up to 16 dB while retaining negligible transmission penalty over 20-km single-mode fiber without dispersion compensation. Numerical analysis is performed to study the tradeoff between OSRNR improvement and attenuation of the PM-NRZ signal as a function of different channel detuning and center wavelength suppressions

Analysis of the dimensional dependence of semiconductor optical amplifier recovery speeds

We investigate the dependence of the speed of recovery of optically excited semiconductor optical amplifiers (SOAs) on the active region dimensions. We use a picosecond pump-probe arrangement to experimentally measure and compare the gain and phase dynamics of four SOAs with varying active region dimensions. A sophisticated time domain SOA model incorporating amplified spontaneous emission (ASE) agrees well with the measurements and shows that, in the absence of a continuous wave (CW) beam, the ASE plays a similar role to such a holding beam. The experimental results are shown to be consistent with a recovery rate which is inversely proportional to the optical area. A significant speed increase is predicted for an appropriate choice of active region dimensions.

Long Reach Passive Optical Networks

This paper is a tutorial reviewing research and development performed over the last few years to extend the reach of passive optical networks using technology such as optical amplifiers.

Rayleigh noise mitigation in DWDM LR-PONs using carrier suppressed subcarrier-amplitude modulated phase shift keying

We demonstrate a novel Rayleigh interferometric noise mitigation scheme for applications in carrier-distributed dense wavelength division multiplexed (DWDM) passive optical networks at 10 Gbit/s using carrier suppressed subcarrier-amplitude modulated phase shift keying modulation. The required optical signal to Rayleigh noise ratio is reduced by 12 dB, while achieving excellent tolerance to dispersion, subcarrier frequency and drive amplitude variations.

Extended-reach PON employing 10Gb/s integrated reflective EAM-SOA

A novel integrated reflective EAM-SOA, capable of tolerating optical carrier power variations of up to 13dB, is operated in a 10Gb/s, 128-way split, 100km reach DWDM-TDMA PON.

10 Gb/s bidirectional transmission in a 116 km reach hybrid DWDM-TDM PON

We report bidirectional transmission at 10 Gb/s over a 116 km-reach DWDM amplified PON using remote reflective modulation of an optical carrier. The full network supports up to 1088 customers with mean data rates of 155 Mb/s.

Packaged hybrid III-V/silicon SOA

We present a hybrid III-V/silicon SOA, mounted in a planar package, with a fiber-to-fiber gain up to 10 dB, maximum internal gain of 28±2 dB, an internal noise figure of 10-11 dB and an output saturation power around 9 dBm.

Modeling of Modulation Formats for Interferometric Noise Mitigation

Interferometric noise in optical communication systems employing reflective modulation schemes can be mitigated by reshaping the data spectrum to reduce the spectral overlap with backscattered and backreflected light. A novel analytical model, capable of analyzing accurately the performance of modulation formats with a wide optical spectrum, is derived here and applied to study the case of interferometric noise caused by Rayleigh backscattering. Compared to more complex models and simulations the new method is fast, simple to implement, and gives clear insight into the physical phenomena involved. In addition, the performance of practical systems can be easily analyzed and optimized due to the capability of the model to include real component specifications such as arbitrary optical and electrical filter responses. The specific case of phase-modulated non-return to zero (PM-NRZ) modulation format is used to validate the model against experimental results and excellent agreement is obtained. The PM-NRZ performance is also investigated as a function of various parameters, quantifying, for example, the trade-off between phase modulation index and interferometric noise mitigation.