Girts Ivanovs

Extending the reach of DWDM-PON access network using chromatic dispersion compensation

The maximum reach of the Dense Wavelength-Division-Multiplexed Passive Optical Network (DWDM-PON) system can be severely limited by chromatic dispersion (CD). This paper contains the investigation of long-reach high speed 16-channel DWDM-PON system with efficient CD compensation methods. It is shown that chromatic dispersion compensation has a crucial role for guaranteed downstream optical link performance and maximum link length of high speed long-reach DWDM-PON system. The results show that usage of additional 7 km long dispersion compensating fiber (DCF) placed in central office improves the DWDM-PON network reach by 19.3% (from 57 km up to 68 km) but usage of fiber Bragg grating (FBG) improves network reach up to 26.3% (from 57 km up to 72 km). As a result, authors recommend the use of FBG for chromatic dispersion compensation to increase the maximum transmission distance of high speed DWDM-PON system.

Mixed Chromatic Dispersion Compensation Methods for Combined HDWDM Systems

The authors have investigated the most efficient realization of mixed chromatic dispersion (CD) compensation schemes for high speed combined high density wavelength division multiplexing (HDWDM) systems. This research is performed with OptSim 5.1 simulation software. In this research it is shown that chromatic dispersion compensation scheme has a crucial role for guaranteed performance in combined HDWM transmission channels. Dispersion management strategy is needed when increasing the bit rate per channel by a factor of four. Therefore, the most efficient CD compensation scheme must be found for realized combined fiber optical transmission system. Authors have revealed that implementation of asymmetrical CD compensation schemes in pre-compensation and post-compensation modules are the most efficient and that it enables the best possible channels bit error ratio (BER) values.

Spectral and energy efficiency considerations in mixed-line rate WDM networks with signal quality guarantee

Mixed-Line Rate (MLR) is a cost efficient solution to cope with the rapidly increasing and heterogeneous Internet traffic. In a MLR-based scenario wavelength channels are organized in groups (i.e., sub-bands), each of which consisting of channels operating at the same rate, e.g., it is possible to have on the same fiber link subbands operating at 10 Gbps, 40 Gbps, and 100 Gbps. In order to increase spectral efficiency one can reduce not only the channel spacing within a sub-band but also the frequency spacing between sub-bands operating at different rates, i.e., the sub-band spacing. On the other hand smaller sub-band spacing may: (i) negatively impact the transparent optical reach of wavelength channels due to the higher inter-channel crosstalk levels, and consequently (ii) increase the network power consumption because of the need of more signal regeneration. This paper aims at assessing the trade-off between spectral efficiency and the power consumption in a WDM transport network, when a certain quality of transmission needs to be guaranteed at the receiving node. This is accomplished by evaluating a number of spectral efficient MLR solutions, where the number of wavelength channels allocated to each sub-band is varied while keeping the required Bit Error Rate (BER) level at the receiving node fixed. Results show that the width of each sub-band plays a central role in determining the power consumption of an end-to-end connection.

Latency causes and reduction in optical metro networks

The dramatic growth of transmitted information in fiber optical networks is leading to a concern about the network latency for high-speed reliable services like financial transactions, telemedicine, virtual and augmented reality, surveillance, and other applications. In order to ensure effective latency engineering, the delay variability needs to be accurately monitored and measured, in order to control it. This paper in brief describes causes of latency in fiber optical metro networks. Several available latency reduction techniques and solutions are also discussed, namely concerning usage of different chromatic dispersion compensation methods, low-latency amplifiers, optical fibers as well as other network elements.

Investigation of high-speed AWG filtered spectrum-sliced WDM PON system

This paper contains the investigation of 8-channel wavelength-division-multiplexed passive optical network by using spectrum-sliced amplified spontaneous emission (ASE) source as a seed light with arrayed-waveguide gratings (AWGs). There are investigated the impact of signal filtering for Gaussian and Flat-top type AWGs on the overall optical systems performance. It is shown that Gaussian type AWGs with channel interval 100 GHz are not suitable for SS-WDM PON systems with high data rate - 2.5 Gbit/s because of wide spectral shape and high channel crosstalk. Numerically it is proved that best solution for 8 channel SS-WDM PON system which provides high performance over the passive fiber optical link length up to 10 km with BER <; 1·10-10 are AWGs with Flat-top spectral shape. It has been investigated that Flat-top AWG unit shows high OSNR because of its amplitude transfer function that provides excellent channel separation and filtering at the same time passing sufficient high optical power from spectrally sliced ASE broadband light source.

Comparison of chromatic dispersion compensation techniques for WDM-PON solution

The upper transmission range of the wavelength division multiplexing passive optical network (WDM-PON) can be restricted by chromatic dispersion (CD). This paper contains the investigation of till 16-channel WDM-PON system with efficient CD pre-compensation and post-compensation methods. It is shown that CD offset has a marginal role for guaranteed optical link downstream performance and maximum length of high-speed WDM-PON system. The results show that employment of extra 7 km long dispersion compensating fiber (DCF) placed in central office (pre-compensation configuration) enhances the WDM-PON network link length by 19.3% (from 57 km up to 68 km), but if extra 2 km long DCF fiber is used in remote terminal (post-compensation configuration) link length can be extended up to 5.3% (from 57 km to 60 km). It was found that usage of fiber Bragg grating (FBG) in central office (pre-compensation configuration) improves network reach up to 26.3% (from 57 km up to 72 km), but using this FBG for CD post-compensation in remote terminal network reach can be improved by 15.8% or 9 km in length - from 57 km to 66 km. Basis on the results authors recommend to use FBG as the best solution for CD compensation in pre-compensation configuration (before SMF line) in future high speed long-reach DWDM-PON systems.

Frequency Arrangement For 700 MHz Band

Abstract The 694-790 MHz (700 MHz) band was allocated by the 2012 World Radiocommunication Conference (WRC-12) in ITU Region 1 (Europe included), to the mobile service on a co-primary basis with other services to which this band was allocated on the primary basis and identified for the International Mobile Telecommunications (IMT). At the same time, the countries of Region 1 will be able also to continue using these frequencies for their broadcasting services if necessary. This allocation will be effective immediately after 2015 World Radiocommunication Conference (WRC-15). In order to make the best possible use of this frequency band for mobile service, a worldwide harmonized frequency arrangement is to be prepared to allow for large economies of scale and international roaming as well as utilizing the available spectrum in the best possible way, minimizing possible interference between services, facilitating deployment and cross-border coordination. The authors analyze different possible frequency arrangements and conclude on the frequency arrangement most suitable for Europe.

Performance improvement of high speed spectrum-sliced dense WDM-PON system

This paper contains the investigation of reach improvement of dense wavelength-division-multiplexed passive optical network (DWDM-PON) using spectrum-sliced amplified spontaneous emission (ASE) source as a seed light. It is shown that flat-top AWG unit provides excellent channel separation and filtering at the same time passing sufficient high optical power from spectrally sliced ASE broadband light source. The maximum reach of the spectrum-sliced dense wavelength-division-multiplexed passive optical network (SS-DWDM PON) system with data transmission speed 2.5 Gbit/s can be fairly limited by chromatic dispersion (CD) because of large optical bandwidth per channel compared to the bit rate. And therefore, dispersion degrades the performance of a SS-DWDM PON system more than it is observed in conventional laser-based system. This paper contains the investigation of improved high speed 8-channel spectrum-sliced DWDM PON system with efficient CD compensation methods like dispersion compensating fiber (DCF) and fiber Bragg grating (FBG). In this research it is shown that CD compensation has an important role for guaranteed downstream optical link performance and maximum link length of high speed SS-DWDM PON system. Results show that FBG used for CD compensation in high speed spectrum-sliced dense WDM PON systems provides better accumulated CD compensation and increase link length up to 150% while DCF fiber provides up to 130% network reach improvement.

New generation energy efficient WDM-PON system using spectrum slicing technology

The spectrum sliced dense wavelength division multiplexed passive optical network (SS-DWDM PON) is a cost effective and power efficient solution for passive optical access networks to satisfy the growing worldwide demand for transmission capacity. Originally resulting ASE spectrum on the output of EDFA is irregular and manipulation with EDFA parameters must be done to make it more flat. Flat optical spectrum of ASE source is an important premise to achieve minimal output power level fluctuations of obtained channels after spectrum slicing operation and provide stable data transmission with BER<;10-10 over the specified fiber optical link length. In this paper we successfully demonstrate the reach improvement by implementation of chromatic dispersion compensation for cost effective spectrum-sliced 16-channel DWDM PON system with data rate 2.5 Gbit/s per channel as well as realization of broadband ASE light source with output power +23 dBm, channel power variation 0.42 dBm and flat spectrum in wavelength range from 1545.32 nm to 1558.98 nm.

Reach Improvement of Spectrum-Sliced Dense WDM-PON System

In this paper we successfully demonstrate the reach improvement of spectrum-sliced dense wavelength-division-multiplexed passive optical network (SS-DWDM PON) where amplified spontaneous emission (ASE) source is used as a seed light. Investigated optical system is built on the ITU-T DWDM frequency grid, defined in recommendation G.694.1 and therefore it is potentially much more compatible with other already existing WDM PON optical systems. In this way it is possible to replace the classic WDM PON system with our proposed extended-reach spectrum-sliced WDM PON system and reduce complexity of network architecture as well as cost per one user. The maximum reach of the spectrum-sliced dense wavelength-division-multiplexed passive optical network (SS-DWDM PON) system with data transmission speed 2.5 Gbit/s can be fairly limited by chromatic dispersion (CD) because of large optical bandwidth per channel compared to the bit rate. And therefore, dispersion degrades the performance of a SS-DWDM PON system more than it is observed in conventional laser-based system. This paper contains the investigation of high speed 8-channel spectrum-sliced DWDM PON system with efficient CD compensation methods like dispersion compensating fiber (DCF) and fiber Bragg grating (FBG). It is shown that CD compensation has an important role for guaranteed downstream optical link performance and maximum transmission line length of high speed SS-DWDM PON system. Results show that FBG used for CD compensation in high speed spectrum-sliced dense WDM PON systems provide better accumulated CD compensation and increase optical link length up to 150% while DCF fiber provides up to 130% reach improvement.