Ioannis Papagiannakis

Investigation of 10-Gb/s RSOA-Based Upstream Transmission in WDM-PONs Utilizing Optical Filtering and Electronic Equalization

Enhanced upstream transmission at 10 Gb/s using a low-bandwidth reflective semiconductor optical amplifier is demonstrated and discussed for extended wavelength- division-multiplexing passive-optical-network applications. Significant improvement in terms of transmission performance is achieved with the use of electronic equalization and optimum filter offset placed at the receiver (optical line terminal) end only. According to filtering detuning, an analytical discussion is presented, explaining the bandwidth enhancement achieved with the proposed technique. The experimental studies consider the benefits of the electronic feed-forward and decision-feedback equalization as well as the required optimum offset optical filtering characteristics.

10 Gb/s full-duplex bidirectional transmission with RSOA-based ONU using detuned optical filtering and decision feedback equalization

Full-duplex bidirectional transmission at 10 Gb/s is demonstrated for extended wavelength division multiplexed passive optical network (WDM-PON) applications, achieving transmission distances up to 25 km of standard single mode fiber (SSMF) when using a low-bandwidth (approximately 1.2 GHz) reflective semiconductor optical amplifier (RSOA) for signal re-modulation at the optical network unit (ONU). The system is assisted by optimum offset filtering at the optical line terminal (OLT)-receiver and the performance is further improved with the use of decision-feedback equalization (DFE). Chromatic dispersion (CD) and Rayleigh Backscattering (RB) effects are considered and analyzed.

Design Characteristics for a Full-Duplex IM/IM Bidirectional Transmission at 10 Gb/s Using Low Bandwidth RSOA

In this paper, the optimum design characteristics and the transmission performance limits of an intensity modulation full-duplex bidirectional transmission system at 10 Gb/s are experimentally studied and presented for application in next-generation-extended wavelength-division-multiplexed passive optical networks. A low-bandwidth (~1.2 GHz) reflective semiconductor optical amplifier (RSOA) is utilized at the optical network unit (ONU) site of the system. Its remodulation properties and performance are examined for both continuous wave and modulated downstream signal, stemming from the optical line terminal (OLT). The techniques adopted to optimize performance are: 1) the use of detuned optical filtering at the OLT receiver that takes advantage of the RSOA chirp and 2) the use of decision feedback equalization (DFE). The extinction ratio of the downstream signal and the driving operation point of the RSOA are examined experimentally in order to find the optimum conditions for the bidirectional transmission. Moreover, the impact of patterning effects in the performance of the system is evaluated. Finally, the additional performance improvement that is achieved with the use of DFE technique is shown.

Performance Improvement of Low-Cost 2.5-Gb/s Rated DML Sources Operated at 10 Gb/s

The transmission performance improvement of low-cost conventional directly modulated laser (DML) sources, fabricated for operation at 2.5 Gb/s but modulated at 10 Gb/s is presented and experimentally demonstrated. Performance improvement is achieved by electronic feed-forward and decision-feedback equalization as well as offset optical filtering at the receiver end. Experimental studies consider both transient and adiabatic chirp dominated DML sources. The transmission improvement is evaluated in terms of required optical signal-to-noise ratio (OSNR) for bit-error-rate values of 10-9 versus transmission length over uncompensated links of standard single-mode fiber (SSMF). Additionally, the optimum filter position is examined in combination with equalization and in terms of OSNR versus detuning from the center wavelength.

Demonstration of a Low-Cost Inband FEC Scheme for STM-64 Transparent Metro Networks

A novel inband forward error correction (FEC) method, developed for the electronic-mitigation of physical optical impairments is implemented and experimentally demonstrated. The proposed inband FEC scheme, FOCUS, is an inherently low-cost approach scalable to any SDH/SONET rate and capable to significantly increase the performance characteristics of metro optical networks. The performance efficiency of the FOCUS method is evaluated in terms of optical signal to noise ratio (OSNR) degradation and chromatic-dispersion degradation associated with the signal transmission over standard single mode fibre. In addition, the system performance is examined using wavelength division multiplexing (WDM) in order to evaluate the effect of nonlinearities. Bit error rate measurements at the standard STM-64 rate (9.953 Gb/s) reveal significant coding-gain improvement for all the examined cases. The benefit of the FOCUS scheme is that it does not require an increased line-rate, as is the case with outband FEC, and therefore offers significant efficiency improvement at an exceptionally low implementation cost

Electronic Channel Equalization Techniques

This paper presents the key design approaches and results in the field of optical impairment distortion compensation by electronic means, as an outcome of the studies and research innovations developed within the COST 291 action. The research topics addressed are related with chromatic dispersion and nonlinearities, with particular reference on FFE/DFE and MLSE-based equalizers as well as with the assistance of different modulation formats. Additionally, the use of electronic compensation in metroaccess applications is examined with reference on studies related with the performance enhancement of DML transmitters.

Upstream transmission in WDM PONs at 10Gbps using low bandwidth RSOAs assisted with optical filtering and electronic equalization

Upstream transmission at 10 Gbps over extended access fibre links is demonstrated using a low-bandwidth RSOA assisted by electronic equalization and optimum filter offset at the receiver (OLT) end.

Electronic mitigation of the filter concatenation effect of low-cost 2.5 Gb/s rated DMLs sources operated at 10 Gb/s

We experimentally investigate (using a re-circulating loop) the benefit of electronic equalization in the mitigation of filter concatenation effects for low-cost DML transmitters rated for 2.5 Gb/s but operated at 10 Gb/s, applicable in transparent metro networks.

Comparison of electronic pre-compensation and post-compensation for cascaded optical filtering of 10 Gb/s NRZ-OOK signals

Using a recirculating loop, the performance improvement for cascaded optical filtering by using precompensation at the transmitter and post-compensation at the receiver is compared.

Transmission performance improvement studies for low-cost 2.5 Gb/s rated DML sources operated at 10 Gb/s

Performance improvement methods for the operation of 2.5 Gbps rated low-cost DML sources at 10 Gbps over record distances are studied by means of chirp characteristics, offset receiver filtering and DFE equalization.