The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform

R I Killey - One of the best experts on this subject based on the ideXlab platform.

  • comparison of low complexity Coherent receivers for udwdm pons lambda to the user
    Journal of Lightwave Technology, 2018
    Co-Authors: Seze M Erkilinc, Domanic Lavery, Seb J Savory, R I Killey, Kai Shi, E C Thomse, P Ayvel
    Abstract:

    It is predicted that demand in future optical access networks will reach multigigabit/s per user. However, the limited performance of the direct detection receiver Technology currently used in the optical network units at the customers’ premises restricts data rates per user. Therefore, the concept of Coherent-enabled access networks has attracted attention in recent years, as this Technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarization digital) Coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of Coherent Technology in access networks, low complexity Coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity Coherent (i.e., polarization-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that, of all the configurations considered, the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal implementation of the system), while requiring the lowest optical receiver hardware complexity (in terms of the optical component count). It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require over 1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate (10 Gb/s) was reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission.

  • comparison of low complexity Coherent receivers for udwdm pons lambda to the user
    arXiv: Signal Processing, 2017
    Co-Authors: Seze M Erkilinc, Domanic Lavery, Seb J Savory, R I Killey, Kai Shi, E C Thomse, P Ayvel
    Abstract:

    It is predicted that demand in optical access networks will reach multi-Gb/s per user. However, the limited performance of the direct detection receiver Technology currently used in the optical network units at the customers' premises restricts data rates/user. Therefore, the concept of Coherent-enabled access networks has attracted attention in recent years, as this Technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarisation digital) Coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of Coherent Technology in the ONUs, low complexity Coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity Coherent (i.e., polarisation-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal system simulations) whilst requiring the lowest optical receiver hardware complexity. It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require >1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission.

  • Bidirectional wavelength-division multiplexing transmission over installed fibre using a simplified optical Coherent access transceiver
    Nature Communications, 2017
    Co-Authors: M.s. Erkilinc, R I Killey, D. Lavery, B. C. Thomsen, S. J. Savory, P Bayvel
    Abstract:

    High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current Technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified Coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access Technology. The proposed solution indicates that digital Coherent Technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections. The signalling scheme used in access networks require electrical bandwidths many times greater than subscribers can utilise. Here, the authors describe a promising approach to achieve bidirectional transmission with bandwidth-efficient yet low-complexity Coherent optical network unit transceiver.

  • bidirectional wavelength division multiplexing transmission over installed fibre using a simplified optical Coherent access transceiver
    Nature Communications, 2017
    Co-Authors: M.s. Erkilinc, Domanic Lavery, Seb J Savory, Benn C Thomsen, R I Killey, Kai Shi, P Bayvel
    Abstract:

    High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current Technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified Coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access Technology. The proposed solution indicates that digital Coherent Technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections.

  • comparison of digital signal signal beat interference compensation techniques in direct detection subcarrier modulation systems
    Optics Express, 2016
    Co-Authors: Z Li, Sezer M Erkilinc, Lidia Galdino, Benn C Thomsen, P Bayvel, R I Killey
    Abstract:

    Single-polarization direct-detection transceivers may offer advantages compared to digital Coherent Technology for some metro, back-haul, access and inter-data center applications since they offer low-cost and complexity solutions. However, a direct-detection receiver introduces nonlinearity upon photo detection, since it is a square-law device, which results in signal distortion due to signal-signal beat interference (SSBI). Consequently, it is desirable to develop effective and low-cost SSBI compensation techniques to improve the performance of such transceivers. In this paper, we compare the performance of a number of recently proposed digital signal processing-based SSBI compensation schemes, including the use of single- and two-stage linearization filters, an iterative linearization filter and a SSBI estimation and cancellation technique. Their performance is assessed experimentally using a 7 × 25 Gb/s wavelength division multiplexed (WDM) single-sideband 16-QAM Nyquistsubcarrier modulation system operating at a net information spectral density of 2.3 (b/s)/Hz.

P Bayvel - One of the best experts on this subject based on the ideXlab platform.

  • Bidirectional wavelength-division multiplexing transmission over installed fibre using a simplified optical Coherent access transceiver
    Nature Communications, 2017
    Co-Authors: M.s. Erkilinc, R I Killey, D. Lavery, B. C. Thomsen, S. J. Savory, P Bayvel
    Abstract:

    High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current Technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified Coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access Technology. The proposed solution indicates that digital Coherent Technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections. The signalling scheme used in access networks require electrical bandwidths many times greater than subscribers can utilise. Here, the authors describe a promising approach to achieve bidirectional transmission with bandwidth-efficient yet low-complexity Coherent optical network unit transceiver.

  • bidirectional wavelength division multiplexing transmission over installed fibre using a simplified optical Coherent access transceiver
    Nature Communications, 2017
    Co-Authors: M.s. Erkilinc, Domanic Lavery, Seb J Savory, Benn C Thomsen, R I Killey, Kai Shi, P Bayvel
    Abstract:

    High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current Technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified Coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access Technology. The proposed solution indicates that digital Coherent Technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections.

  • comparison of digital signal signal beat interference compensation techniques in direct detection subcarrier modulation systems
    Optics Express, 2016
    Co-Authors: Z Li, Sezer M Erkilinc, Lidia Galdino, Benn C Thomsen, P Bayvel, R I Killey
    Abstract:

    Single-polarization direct-detection transceivers may offer advantages compared to digital Coherent Technology for some metro, back-haul, access and inter-data center applications since they offer low-cost and complexity solutions. However, a direct-detection receiver introduces nonlinearity upon photo detection, since it is a square-law device, which results in signal distortion due to signal-signal beat interference (SSBI). Consequently, it is desirable to develop effective and low-cost SSBI compensation techniques to improve the performance of such transceivers. In this paper, we compare the performance of a number of recently proposed digital signal processing-based SSBI compensation schemes, including the use of single- and two-stage linearization filters, an iterative linearization filter and a SSBI estimation and cancellation technique. Their performance is assessed experimentally using a 7 × 25 Gb/s wavelength division multiplexed (WDM) single-sideband 16-QAM Nyquistsubcarrier modulation system operating at a net information spectral density of 2.3 (b/s)/Hz.

Seb J Savory - One of the best experts on this subject based on the ideXlab platform.

  • Coherent Access: Status and Opportunities
    2020 IEEE Photonics Society Summer Topicals Meeting Series (SUM), 2020
    Co-Authors: Saifuddin Faruk, Seb J Savory
    Abstract:

    Coherent Technology has the potential to be a disruptive Technology for access networks. However, deployment of Coherent-access remains challenging due to its higher complexity and power-consumption compared with conventional approaches. Herein we review present research status on reduced-complexity Coherent PON and outline the future opportunities.

  • OFC - Coherent ONU Designs for 50 Gb/s/λ PON
    Optical Fiber Communication Conference (OFC) 2019, 2019
    Co-Authors: M.s. Erkilinc, Domanic Lavery, Seb J Savory, Polina Bayvel, Robert I. Killey, Colja Schubert
    Abstract:

    The required complexity of Coherent Technology has always been a show-stopper in optical access networks. Here, the recent compelling research activities in low-complexity Coherent PONs are reviewed, and their feasibility for 50 Gb/s/λ is investigated.

  • comparison of low complexity Coherent receivers for udwdm pons lambda to the user
    Journal of Lightwave Technology, 2018
    Co-Authors: Seze M Erkilinc, Domanic Lavery, Seb J Savory, R I Killey, Kai Shi, E C Thomse, P Ayvel
    Abstract:

    It is predicted that demand in future optical access networks will reach multigigabit/s per user. However, the limited performance of the direct detection receiver Technology currently used in the optical network units at the customers’ premises restricts data rates per user. Therefore, the concept of Coherent-enabled access networks has attracted attention in recent years, as this Technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarization digital) Coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of Coherent Technology in access networks, low complexity Coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity Coherent (i.e., polarization-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that, of all the configurations considered, the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal implementation of the system), while requiring the lowest optical receiver hardware complexity (in terms of the optical component count). It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require over 1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate (10 Gb/s) was reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission.

  • comparison of low complexity Coherent receivers for udwdm pons lambda to the user
    arXiv: Signal Processing, 2017
    Co-Authors: Seze M Erkilinc, Domanic Lavery, Seb J Savory, R I Killey, Kai Shi, E C Thomse, P Ayvel
    Abstract:

    It is predicted that demand in optical access networks will reach multi-Gb/s per user. However, the limited performance of the direct detection receiver Technology currently used in the optical network units at the customers' premises restricts data rates/user. Therefore, the concept of Coherent-enabled access networks has attracted attention in recent years, as this Technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarisation digital) Coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of Coherent Technology in the ONUs, low complexity Coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity Coherent (i.e., polarisation-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal system simulations) whilst requiring the lowest optical receiver hardware complexity. It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require >1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission.

  • bidirectional wavelength division multiplexing transmission over installed fibre using a simplified optical Coherent access transceiver
    Nature Communications, 2017
    Co-Authors: M.s. Erkilinc, Domanic Lavery, Seb J Savory, Benn C Thomsen, R I Killey, Kai Shi, P Bayvel
    Abstract:

    High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current Technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified Coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access Technology. The proposed solution indicates that digital Coherent Technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections.

Shenglun Cheng - One of the best experts on this subject based on the ideXlab platform.

  • mediating factors that influence the Technology integration practices of teacher educators
    Computers in Education, 2019
    Co-Authors: Michael J Nelson, Rick Voithofer, Shenglun Cheng
    Abstract:

    Abstract While the United States federal government and the main teacher education accreditation organization push for the inclusion of Technology in teacher education across the curriculum, little attention has been paid to understanding the Technology competencies and behaviors of teacher educators. This study explores this gap by investigating what direct and mediating factors predict technological pedagogical content knowledge (TPACK) in teacher educators, and how these factors along with TPACK influence the adoption of the ISTE Technology standards in teacher education. The findings from a sample of 806 teacher educators across the United States indicate that there are significant differences in both TPACK and ISTE standard alignment across subject areas, and that experience levels positively predict ISTE standard alignment to a small degree. More significant, however, is the finding that Technology knowledge and institutional support are important mediators, predicting TPACK and ISTE standard alignment. Additionally, TPACK strongly predicts ISTE standard alignment. These findings suggest that institutions should provide targeted support to teacher educators across disciplines and should adopt Coherent Technology frameworks for their programs.

  • mediating factors that influence the Technology integration practices of teacher educators
    Computers in Education, 2019
    Co-Authors: Michael J Nelson, Rick Voithofer, Shenglun Cheng
    Abstract:

    Abstract While the United States federal government and the main teacher education accreditation organization push for the inclusion of Technology in teacher education across the curriculum, little attention has been paid to understanding the Technology competencies and behaviors of teacher educators. This study explores this gap by investigating what direct and mediating factors predict technological pedagogical content knowledge (TPACK) in teacher educators, and how these factors along with TPACK influence the adoption of the ISTE Technology standards in teacher education. The findings from a sample of 806 teacher educators across the United States indicate that there are significant differences in both TPACK and ISTE standard alignment across subject areas, and that experience levels positively predict ISTE standard alignment to a small degree. More significant, however, is the finding that Technology knowledge and institutional support are important mediators, predicting TPACK and ISTE standard alignment. Additionally, TPACK strongly predicts ISTE standard alignment. These findings suggest that institutions should provide targeted support to teacher educators across disciplines and should adopt Coherent Technology frameworks for their programs.

Domanic Lavery - One of the best experts on this subject based on the ideXlab platform.

  • OFC - Coherent ONU Designs for 50 Gb/s/λ PON
    Optical Fiber Communication Conference (OFC) 2019, 2019
    Co-Authors: M.s. Erkilinc, Domanic Lavery, Seb J Savory, Polina Bayvel, Robert I. Killey, Colja Schubert
    Abstract:

    The required complexity of Coherent Technology has always been a show-stopper in optical access networks. Here, the recent compelling research activities in low-complexity Coherent PONs are reviewed, and their feasibility for 50 Gb/s/λ is investigated.

  • comparison of low complexity Coherent receivers for udwdm pons lambda to the user
    Journal of Lightwave Technology, 2018
    Co-Authors: Seze M Erkilinc, Domanic Lavery, Seb J Savory, R I Killey, Kai Shi, E C Thomse, P Ayvel
    Abstract:

    It is predicted that demand in future optical access networks will reach multigigabit/s per user. However, the limited performance of the direct detection receiver Technology currently used in the optical network units at the customers’ premises restricts data rates per user. Therefore, the concept of Coherent-enabled access networks has attracted attention in recent years, as this Technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarization digital) Coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of Coherent Technology in access networks, low complexity Coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity Coherent (i.e., polarization-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that, of all the configurations considered, the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal implementation of the system), while requiring the lowest optical receiver hardware complexity (in terms of the optical component count). It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require over 1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate (10 Gb/s) was reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission.

  • comparison of low complexity Coherent receivers for udwdm pons lambda to the user
    arXiv: Signal Processing, 2017
    Co-Authors: Seze M Erkilinc, Domanic Lavery, Seb J Savory, R I Killey, Kai Shi, E C Thomse, P Ayvel
    Abstract:

    It is predicted that demand in optical access networks will reach multi-Gb/s per user. However, the limited performance of the direct detection receiver Technology currently used in the optical network units at the customers' premises restricts data rates/user. Therefore, the concept of Coherent-enabled access networks has attracted attention in recent years, as this Technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarisation digital) Coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of Coherent Technology in the ONUs, low complexity Coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity Coherent (i.e., polarisation-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal system simulations) whilst requiring the lowest optical receiver hardware complexity. It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require >1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission.

  • bidirectional wavelength division multiplexing transmission over installed fibre using a simplified optical Coherent access transceiver
    Nature Communications, 2017
    Co-Authors: M.s. Erkilinc, Domanic Lavery, Seb J Savory, Benn C Thomsen, R I Killey, Kai Shi, P Bayvel
    Abstract:

    High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current Technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified Coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access Technology. The proposed solution indicates that digital Coherent Technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections.

  • digital Coherent Technology for long reach optical access
    Optical Fiber Communication Conference, 2014
    Co-Authors: Domanic Lavery, Seb J Savory
    Abstract:

    This semi-tutorial paper outlines the potential advantages afforded by digital Coherent receivers in long-reach optical access networks. Low complexity DSP algorithms are discussed which relax the optical complexity requirements of a Coherent receiver. © OSA 2014.