ABSTRACT Tackling the digital divide has become one of the main goals of many governments around ... more ABSTRACT Tackling the digital divide has become one of the main goals of many governments around the world, and a main target for the European Commission. Fibre-to-the-premises (FTTP) is the only access technology that has the potential to totally eliminate the digital divide since, within access distances, fibre capacity can be considered distance independent. In practice, however the higher cost means that many rural areas might not be served by FTTP services, further widening the capacity gap between rural and urban access. However, while fibre roll out is certainly less cost-effective in rural than urban areas, a proper deployment strategy that minimises cable installation costs can increase the network profitability and thus the rural FTTP coverage. In this paper, we propose a novel agglomerative clustering algorithm. The algorithm together with ILP and heuristic models, attempt to minimise the total fibre cable required to connect sparse rural users to a drop PON splitter located up to several kilometres away from the user. Our results show that proper deployment strategies can increase the use of large last-stage splitter, thus increasing sharing of fibre among users, while still minimising the overall cable length. In addition, we show that our heuristic is able to obtain similar results as the ILP (i.e. within an 8% margin), but can reduce the computation time by about 6 times, for the scenarios we have considered.
2012 17th Opto-Electronics and Communications Conference, 2012
ABSTRACT We address the cost-effective 2R/3R regenerators placement problem. An optimal polynomia... more ABSTRACT We address the cost-effective 2R/3R regenerators placement problem. An optimal polynomial-time algorithm for line network topologies and a heuristic for mesh network topologies are proposed. The benefits of combined 2R/3R regenerators placement are evaluated.
Integrated Photonics Research, Silicon and Nanophotonics and Photonics in Switching, 2010
We present a sensitivity study on how launch optical power can be managed to control the CAPEX of... more We present a sensitivity study on how launch optical power can be managed to control the CAPEX of a mixed line rate (i.e., 10/40/100 Gbps wavelengths on same fiber) optical network.
ABSTRACT With the use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA),... more ABSTRACT With the use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA), the long-reach passive optical network (LR-PON) can provide enormous bandwidth over large distances. However, these new technologies can also deteriorate the receivers' bit-error rate (BER) performance. By bringing the concept of BER-awareness into network planning, we can alleviate the performance deterioration, which could in turn lead to simpler design of receiver and thus lower the total cost of LR-PON. The effects of AWG and EDFA on BER are studied in this paper. An analytical model of BER performance is developed as a function of the output port location in the AWG and the distance of the receiver from the AWG. Not only does the proposed model capture the power loss caused by AWG, but it also accounts for several transmission impairments, including the beat noise due to inter-channel crosstalk in the AWG, the amplified spontaneous emission (ASE) noise related to EDFA, and the thermal noise related to the receiver. Based on this model, we propose both short-term and long-term distance-aware wavelength allocation schemes, which balance the BER among the optical network units (ONUs) at different distance. Simulation results show that average BER improves and the relative standard deviation decreases.
Optical network WDM Network design Mixed line rate Maximum transmission range Bit-error rate Chan... more Optical network WDM Network design Mixed line rate Maximum transmission range Bit-error rate Channel spacing Launch power Regenerator a b s t r a c t Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks are going through significant innovations. Wavelength-division multiplexed (WDM) optical networks can now cost-effectively support the growing heterogeneity of traffic demands by having mixed line rates (MLR) over different wavelength channels.
ABSTRACT An N:1 protection mechanism is proposed to reduce backup OLTs in a resilient dual-homed ... more ABSTRACT An N:1 protection mechanism is proposed to reduce backup OLTs in a resilient dual-homed LR-PON deployment. We model the problem as an Integer Linear Program and solve it for an Irish network deployment.
We propose new design models for mixed-line-rate (MLR) optical networks with no regeneration (tra... more We propose new design models for mixed-line-rate (MLR) optical networks with no regeneration (transparent) and selective regeneration (translucent). Our results show the interplay between transponder cost and regenerator card cost using mixed line rates.
The use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA) enables long-r... more The use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA) enables long-reach passive optical network (LR-PON) to provide enormous bandwidth over large distance, but they also deteriorate receivers' bit-error rate (BER) performance. In this paper, the effects of AWG and EDFA on BER are studied with both short-term and long-term distanceaware wavelength allocation schemes, to balance the BER among ONUs at different distance. Simulation results show that average BER improves and the relative standard deviation decreases.
With the growth of traffic volume and the emergence of various new applications, future telecom n... more With the growth of traffic volume and the emergence of various new applications, future telecom networks are expected to be increasingly heterogeneous with respect to applications supported and underlying technologies employed. To address this heterogeneity, it may be most cost effective to set up different lightpaths at different bit rates in such a backbone telecom mesh network employing optical wavelength-division multiplexing. This approach can be cost effective because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths), while a high-bit-rate service can be accommodated directly on a wavelength itself. Optical networks with mixed line rates (MLRs), e.g., 10/40/100 Gb/s over different wavelength channels, are a new networking paradigm. The unregenerated reach of a lightpath depends on its line rate. So, the assignment of a line rate to a lightpath is a tradeoff between its capacity and transparent reach. Thus, based on their signal-quality constraints (threshold bit error rate), intelligent assignment of line rates to lightpaths can minimize the need for signal regeneration. This constraint on the transparent reach based on threshold signal quality can be relaxed by employing more advanced modulation formats, but with more investment.
Optical network WDM Network design Mixed line rate Signal regeneration Maximum transmission range... more Optical network WDM Network design Mixed line rate Signal regeneration Maximum transmission range Bit-error rate a b s t r a c t Future telecommunication networks employing optical wavelength-division multiplexing (WDM) are expected to be increasingly heterogeneous and support a wide variety of traffic demands. Based on the nature of the demands, it may be convenient to set up lightpaths on these networks with different bit rates. Then, the network design cost could be reduced because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths) while high-bit-rate services can be accommodated on a wavelength itself. Future optical networks may support mixed line rates (say over 10/40/100 Gbps). Since a lightpath may travel a long distance, for high bit rates, the effect of the physical impairments along a lightpath may become very significant (leading to high bit-error rate (BER)); and the signal's maximum transmission range, which depends on the bit rate, will become limited.
Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks ... more Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks are going through new innovations and paradigm shift. The wavelength-division multiplexed (WDM) optical networks may cost-effectively support the growing heterogeneity of traffic demands by having mixed line rates (MLR) over different wavelength channels. The coexistence of wavelength channels with different line rates in the same fiber brings up the important issue of the choice of the channel spacing that one can have in these MLR networks. The channel spacing affects the signal quality in terms of bit-error rate (BER), and hence affects the maximum reach of the lightpaths, which is a function of line rates. Various approaches to set an opportunistic width of the channel spacing can be considered: i) on a practical side, one may choose uniform fixed channel spacing specified by the ITU-T grid (typically 50 GHz); ii) alternatively, to optimize the usage of the fiber spectrum, one can explore different channel spacing for different line rates, also referred to as the "one-size-does-not-fit-all" approach; iii) else an optimal value of channel spacing that leads to minimum cost can be sought. In this work, we investigate the third case by evaluating the cost of a MLR network for different channel spacings. Our results show that, even under the assumption of uniform channel spacing for a MLR network, it is possible to identify optimal values of channel spacing for a minimum-cost MLR network design.
ABSTRACT Tackling the digital divide has become one of the main goals of many governments around ... more ABSTRACT Tackling the digital divide has become one of the main goals of many governments around the world, and a main target for the European Commission. Fibre-to-the-premises (FTTP) is the only access technology that has the potential to totally eliminate the digital divide since, within access distances, fibre capacity can be considered distance independent. In practice, however the higher cost means that many rural areas might not be served by FTTP services, further widening the capacity gap between rural and urban access. However, while fibre roll out is certainly less cost-effective in rural than urban areas, a proper deployment strategy that minimises cable installation costs can increase the network profitability and thus the rural FTTP coverage. In this paper, we propose a novel agglomerative clustering algorithm. The algorithm together with ILP and heuristic models, attempt to minimise the total fibre cable required to connect sparse rural users to a drop PON splitter located up to several kilometres away from the user. Our results show that proper deployment strategies can increase the use of large last-stage splitter, thus increasing sharing of fibre among users, while still minimising the overall cable length. In addition, we show that our heuristic is able to obtain similar results as the ILP (i.e. within an 8% margin), but can reduce the computation time by about 6 times, for the scenarios we have considered.
2012 17th Opto-Electronics and Communications Conference, 2012
ABSTRACT We address the cost-effective 2R/3R regenerators placement problem. An optimal polynomia... more ABSTRACT We address the cost-effective 2R/3R regenerators placement problem. An optimal polynomial-time algorithm for line network topologies and a heuristic for mesh network topologies are proposed. The benefits of combined 2R/3R regenerators placement are evaluated.
Integrated Photonics Research, Silicon and Nanophotonics and Photonics in Switching, 2010
We present a sensitivity study on how launch optical power can be managed to control the CAPEX of... more We present a sensitivity study on how launch optical power can be managed to control the CAPEX of a mixed line rate (i.e., 10/40/100 Gbps wavelengths on same fiber) optical network.
ABSTRACT With the use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA),... more ABSTRACT With the use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA), the long-reach passive optical network (LR-PON) can provide enormous bandwidth over large distances. However, these new technologies can also deteriorate the receivers' bit-error rate (BER) performance. By bringing the concept of BER-awareness into network planning, we can alleviate the performance deterioration, which could in turn lead to simpler design of receiver and thus lower the total cost of LR-PON. The effects of AWG and EDFA on BER are studied in this paper. An analytical model of BER performance is developed as a function of the output port location in the AWG and the distance of the receiver from the AWG. Not only does the proposed model capture the power loss caused by AWG, but it also accounts for several transmission impairments, including the beat noise due to inter-channel crosstalk in the AWG, the amplified spontaneous emission (ASE) noise related to EDFA, and the thermal noise related to the receiver. Based on this model, we propose both short-term and long-term distance-aware wavelength allocation schemes, which balance the BER among the optical network units (ONUs) at different distance. Simulation results show that average BER improves and the relative standard deviation decreases.
Optical network WDM Network design Mixed line rate Maximum transmission range Bit-error rate Chan... more Optical network WDM Network design Mixed line rate Maximum transmission range Bit-error rate Channel spacing Launch power Regenerator a b s t r a c t Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks are going through significant innovations. Wavelength-division multiplexed (WDM) optical networks can now cost-effectively support the growing heterogeneity of traffic demands by having mixed line rates (MLR) over different wavelength channels.
ABSTRACT An N:1 protection mechanism is proposed to reduce backup OLTs in a resilient dual-homed ... more ABSTRACT An N:1 protection mechanism is proposed to reduce backup OLTs in a resilient dual-homed LR-PON deployment. We model the problem as an Integer Linear Program and solve it for an Irish network deployment.
We propose new design models for mixed-line-rate (MLR) optical networks with no regeneration (tra... more We propose new design models for mixed-line-rate (MLR) optical networks with no regeneration (transparent) and selective regeneration (translucent). Our results show the interplay between transponder cost and regenerator card cost using mixed line rates.
The use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA) enables long-r... more The use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA) enables long-reach passive optical network (LR-PON) to provide enormous bandwidth over large distance, but they also deteriorate receivers' bit-error rate (BER) performance. In this paper, the effects of AWG and EDFA on BER are studied with both short-term and long-term distanceaware wavelength allocation schemes, to balance the BER among ONUs at different distance. Simulation results show that average BER improves and the relative standard deviation decreases.
With the growth of traffic volume and the emergence of various new applications, future telecom n... more With the growth of traffic volume and the emergence of various new applications, future telecom networks are expected to be increasingly heterogeneous with respect to applications supported and underlying technologies employed. To address this heterogeneity, it may be most cost effective to set up different lightpaths at different bit rates in such a backbone telecom mesh network employing optical wavelength-division multiplexing. This approach can be cost effective because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths), while a high-bit-rate service can be accommodated directly on a wavelength itself. Optical networks with mixed line rates (MLRs), e.g., 10/40/100 Gb/s over different wavelength channels, are a new networking paradigm. The unregenerated reach of a lightpath depends on its line rate. So, the assignment of a line rate to a lightpath is a tradeoff between its capacity and transparent reach. Thus, based on their signal-quality constraints (threshold bit error rate), intelligent assignment of line rates to lightpaths can minimize the need for signal regeneration. This constraint on the transparent reach based on threshold signal quality can be relaxed by employing more advanced modulation formats, but with more investment.
Optical network WDM Network design Mixed line rate Signal regeneration Maximum transmission range... more Optical network WDM Network design Mixed line rate Signal regeneration Maximum transmission range Bit-error rate a b s t r a c t Future telecommunication networks employing optical wavelength-division multiplexing (WDM) are expected to be increasingly heterogeneous and support a wide variety of traffic demands. Based on the nature of the demands, it may be convenient to set up lightpaths on these networks with different bit rates. Then, the network design cost could be reduced because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths) while high-bit-rate services can be accommodated on a wavelength itself. Future optical networks may support mixed line rates (say over 10/40/100 Gbps). Since a lightpath may travel a long distance, for high bit rates, the effect of the physical impairments along a lightpath may become very significant (leading to high bit-error rate (BER)); and the signal's maximum transmission range, which depends on the bit rate, will become limited.
Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks ... more Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks are going through new innovations and paradigm shift. The wavelength-division multiplexed (WDM) optical networks may cost-effectively support the growing heterogeneity of traffic demands by having mixed line rates (MLR) over different wavelength channels. The coexistence of wavelength channels with different line rates in the same fiber brings up the important issue of the choice of the channel spacing that one can have in these MLR networks. The channel spacing affects the signal quality in terms of bit-error rate (BER), and hence affects the maximum reach of the lightpaths, which is a function of line rates. Various approaches to set an opportunistic width of the channel spacing can be considered: i) on a practical side, one may choose uniform fixed channel spacing specified by the ITU-T grid (typically 50 GHz); ii) alternatively, to optimize the usage of the fiber spectrum, one can explore different channel spacing for different line rates, also referred to as the "one-size-does-not-fit-all" approach; iii) else an optimal value of channel spacing that leads to minimum cost can be sought. In this work, we investigate the third case by evaluating the cost of a MLR network for different channel spacings. Our results show that, even under the assumption of uniform channel spacing for a MLR network, it is possible to identify optimal values of channel spacing for a minimum-cost MLR network design.
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Papers by Avishek Nag