We experimentally show optically filtered lasers reduce OSNR penalty due to phase tracking error ... more We experimentally show optically filtered lasers reduce OSNR penalty due to phase tracking error up to 3 dB for two parallel decision directed algorithms with feedback delay in an 11 Gbaud/s 16QAM coherent system.
The 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2002
(I) Department of Electronic Engineering, Dublin City University, D. 9, Ireland (liam.barry@dcuie... more (I) Department of Electronic Engineering, Dublin City University, D. 9, Ireland (liam.barry@dcuie) (2) Physics Department, Trinity College Dublin, Dublin 2, Ireland (3) Department of Electronic Engineering, University of Sheffield, Sheffield, SI 3JD, England
The future development of high-speed optical data channels, operating at individual data rates in... more The future development of high-speed optical data channels, operating at individual data rates in excess of 100Gbit/s, will require a sensitive and ultra-fast method for pulse measurement . Current high-speed signals are usually characterized using a fast photodetector in conjunction with a high-speed oscilloscope, but are limited to maximum data rate of approximately 40Gbit/s. An alternative is to employ all-optical sampling techniques based on ultra-fast optical nonlinearities present in optical fibres, crystals and semiconductors. One such nonlinearity is the optical-to-electrical process of Two-Photon Absorption (TPA) in a semiconductor .
(CLEO). Conference on Lasers and Electro-Optics, 2005., 2005
We demonstrate a highly-efficient optical sampling system based upon the nonlinear process of Two... more We demonstrate a highly-efficient optical sampling system based upon the nonlinear process of Two-Photon Absorption in a specially designed semiconductor microcavity. The sensitivity of the system is around 0.1mW2 and the temporal resolution is 2ps.
Investigation of the cross-channel interference in wavelength packet switched networks is present... more Investigation of the cross-channel interference in wavelength packet switched networks is presented. The results show that the output of a tunable laser needs to be correctly attenuated during the switching event in order to avoid system performance degradation.
Conference on Lasers and Electro-Optics 2010, 2010
ABSTRACT Two Michelson fiber interferometers were used to measure the in-band OSNR of a noisy sig... more ABSTRACT Two Michelson fiber interferometers were used to measure the in-band OSNR of a noisy signal between 5 and 30dB within ±0.5dB without prior knowledge of the noise-free extinction ratio of the signal.
ABSTRACT In-band OSNR from 5 to 30dB of a single 10G NRZ-OOK channel was measured by two fiber in... more ABSTRACT In-band OSNR from 5 to 30dB of a single 10G NRZ-OOK channel was measured by two fiber interferometers within an accuracy of ±0.5dB without requirement for knowledge of the noise-free extinction ratio of the signal.
36th European Conference and Exhibition on Optical Communication, 2010
The in-band OSNR of SP and DP QPSK signals were measured over a range of 10 to 21dB ±1dB using a ... more The in-band OSNR of SP and DP QPSK signals were measured over a range of 10 to 21dB ±1dB using a pair of polarisation independent Michelson fibre interferometers without the requirement for prior knowledge of the signal's coherence properties.
ABSTRACT Monolithic semiconductor passively mode locked lasers (MLL) are very attractive componen... more ABSTRACT Monolithic semiconductor passively mode locked lasers (MLL) are very attractive components for many applications including high bit rate telecommunications, microwave photonics and instrumentation. Owing to the three dimensional confinement of the charge carriers, quantum dot based mode-locked lasers have been the subject of intense investigations because of their improved performance compared to conventional material systems. Indeed, the inhomogeneous gain broadening and the ultrafast absorption recovery dynamics are an asset for short pulse generation. Moreover, the weak coupling of amplified spontaneous emission with the guided modes plus low loss waveguide leads to low timing jitter. Our work concentrates on InAs quantum dash nanostructures grown on InP substrate, intended for applications in the 1.55 μm telecom window. InAs/InP quantum dash based lasers, in particular, have demonstrated efficient mode locking in single section Fabry-Perot configurations. The flat optical spectrum of about 12 nm, combined with the narrow RF beat note linewidth of about 10 kHz make them a promising technology for optical frequency comb generation. Coherence between spectral modes was assessed by means of spectral phase measurements. The parabolic spectral phase profile indicates that short pulses can be obtained provided the intracavity dispersion can be compensated by inserting a single mode fiber.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
Advanced optical pulse characterization methods are essential for high-speed optical communicatio... more Advanced optical pulse characterization methods are essential for high-speed optical communications. Recently non-iterative characterization of general optical pulses using sinusoidal optical phase modulation has been reported [12]. However, the usable phase ...
A novel two-section tunable laser diode is demonstrated by etching slots into the laser ridge. A ... more A novel two-section tunable laser diode is demonstrated by etching slots into the laser ridge. A discontinuous tuning-range of 30 nm was achieved with a SMSR of 38 dB. A wavelength switching time of 1.5 ns is demonstrated.
ABSTRACT Wavelength conversion via four-wave mixing (FWM) schemes of high-bit rate data formats a... more ABSTRACT Wavelength conversion via four-wave mixing (FWM) schemes of high-bit rate data formats are conventionally achieved using a strong pump source and a secondary nonlinear device, such as highly nonlinear fibre [1] or semiconductor optical amplifier [2]. In this work we obviate the need for a secondary nonlinear device, and achieve wavelength-conversion of high repetition-rate pulse trains by externally injecting a strong optical tone directly into the cavity of the 48GHz repetition-rate passively mode-locked semiconductor laser, achieving wavelength-conversion via partially-degenerate FWM. For the first time to our knowledge, we provide experimental results of the wavelength tunability of this wavelength-conversion scheme and show that the entire signal spectrum undergoes parametrically conversion.
We propose and verify the use of the power spectral density of the FM noise spectrum to study the... more We propose and verify the use of the power spectral density of the FM noise spectrum to study the phase noise relationship between the four-wave mixing components.
Conference on Lasers and Electro-Optics 2012, 2012
ABSTRACT Device characterizations of QDash semiconductor lasers as a subchannel comb generator ar... more ABSTRACT Device characterizations of QDash semiconductor lasers as a subchannel comb generator are presented, including measurements of electric field, optical linewidth, and mode coherence out to 1.5THz spectral mode separation.
Opto-Ireland 2005: Optoelectronics, Photonic Devices, and Optical Networks, 2005
Future high-speed optical communications networks operating at data rates in excess of 100Gbit/s ... more Future high-speed optical communications networks operating at data rates in excess of 100Gbit/s per channel will require a sensitive and ultrafast technique for precise optical signal monitoring. 1 The standard way of characterising high-speed optical signals to use a fast photodetector in conjunction with a high-speed oscilloscope. However, this method is limited to a maximum data rate of approximately 40Gbit/s. An alternative is to employ all-optical sampling techniques based on ultrafast optical nonlinearities present in optical fibres, optical crystals and semiconductors. One such nonlinearity is the optical-to-electrical process of Two-Photon Absorption (TPA) in a semiconductor. This paper presents an optical sampling technique based on TPA in a specially designed semiconductor microcavity. By incorporating the microcavity design, we are able to enhance the TPA efficiency to a level that can be used for high-speed optical sampling.
European Conference and Exhibition on Optical Communication, 2012
Next generation optical access networks will require low cost lasers in conjunction with network ... more Next generation optical access networks will require low cost lasers in conjunction with network flexibility and higher data rates. This work presents the direct modulation of a low cost tuneable slotted Fabry-Pérot laser (tuneable over 14nm) with AM-OFDM. Characteristics of this dual section laser are presented and transmission of 10Gb/s over 50km is achieved with this device.
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT Phase locked frequency combs spanning > 1.5 THz have been generated using passive... more ABSTRACT Phase locked frequency combs spanning > 1.5 THz have been generated using passively mode locked quantum dash based lasers emitting at 1.55 µm. These combs are particularly suited for future OFDM transmission systems.
Lasers with narrow-linewidth emission are a key component for higher-order modulation formats. We... more Lasers with narrow-linewidth emission are a key component for higher-order modulation formats. We report on discrete-mode laser diodes designed for narrow-linewidth emission and demonstrate linewidths less than 80 kHz. Using these devices in quadrature phase shift keying and 16-quadrature amplitude modulation transmission setups, similar performance to that of an external cavity laser is demonstrated.
China-Ireland International Conference on Information and Communications Technologies (CIICT 2008), 2008
ABSTRACT This paper investigates the use of a two-photon absorption photodetector for all-optical... more ABSTRACT This paper investigates the use of a two-photon absorption photodetector for all-optical signal processing. Continuous, wavelength selective chromatic dispersion monitoring in a high-speed multi-wavelength system is discussed. The reduction of multiple access interference in an optical code division multiple access network using a TPA photodetector is also presented.
We experimentally show optically filtered lasers reduce OSNR penalty due to phase tracking error ... more We experimentally show optically filtered lasers reduce OSNR penalty due to phase tracking error up to 3 dB for two parallel decision directed algorithms with feedback delay in an 11 Gbaud/s 16QAM coherent system.
The 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2002
(I) Department of Electronic Engineering, Dublin City University, D. 9, Ireland (liam.barry@dcuie... more (I) Department of Electronic Engineering, Dublin City University, D. 9, Ireland (liam.barry@dcuie) (2) Physics Department, Trinity College Dublin, Dublin 2, Ireland (3) Department of Electronic Engineering, University of Sheffield, Sheffield, SI 3JD, England
The future development of high-speed optical data channels, operating at individual data rates in... more The future development of high-speed optical data channels, operating at individual data rates in excess of 100Gbit/s, will require a sensitive and ultra-fast method for pulse measurement . Current high-speed signals are usually characterized using a fast photodetector in conjunction with a high-speed oscilloscope, but are limited to maximum data rate of approximately 40Gbit/s. An alternative is to employ all-optical sampling techniques based on ultra-fast optical nonlinearities present in optical fibres, crystals and semiconductors. One such nonlinearity is the optical-to-electrical process of Two-Photon Absorption (TPA) in a semiconductor .
(CLEO). Conference on Lasers and Electro-Optics, 2005., 2005
We demonstrate a highly-efficient optical sampling system based upon the nonlinear process of Two... more We demonstrate a highly-efficient optical sampling system based upon the nonlinear process of Two-Photon Absorption in a specially designed semiconductor microcavity. The sensitivity of the system is around 0.1mW2 and the temporal resolution is 2ps.
Investigation of the cross-channel interference in wavelength packet switched networks is present... more Investigation of the cross-channel interference in wavelength packet switched networks is presented. The results show that the output of a tunable laser needs to be correctly attenuated during the switching event in order to avoid system performance degradation.
Conference on Lasers and Electro-Optics 2010, 2010
ABSTRACT Two Michelson fiber interferometers were used to measure the in-band OSNR of a noisy sig... more ABSTRACT Two Michelson fiber interferometers were used to measure the in-band OSNR of a noisy signal between 5 and 30dB within ±0.5dB without prior knowledge of the noise-free extinction ratio of the signal.
ABSTRACT In-band OSNR from 5 to 30dB of a single 10G NRZ-OOK channel was measured by two fiber in... more ABSTRACT In-band OSNR from 5 to 30dB of a single 10G NRZ-OOK channel was measured by two fiber interferometers within an accuracy of ±0.5dB without requirement for knowledge of the noise-free extinction ratio of the signal.
36th European Conference and Exhibition on Optical Communication, 2010
The in-band OSNR of SP and DP QPSK signals were measured over a range of 10 to 21dB ±1dB using a ... more The in-band OSNR of SP and DP QPSK signals were measured over a range of 10 to 21dB ±1dB using a pair of polarisation independent Michelson fibre interferometers without the requirement for prior knowledge of the signal's coherence properties.
ABSTRACT Monolithic semiconductor passively mode locked lasers (MLL) are very attractive componen... more ABSTRACT Monolithic semiconductor passively mode locked lasers (MLL) are very attractive components for many applications including high bit rate telecommunications, microwave photonics and instrumentation. Owing to the three dimensional confinement of the charge carriers, quantum dot based mode-locked lasers have been the subject of intense investigations because of their improved performance compared to conventional material systems. Indeed, the inhomogeneous gain broadening and the ultrafast absorption recovery dynamics are an asset for short pulse generation. Moreover, the weak coupling of amplified spontaneous emission with the guided modes plus low loss waveguide leads to low timing jitter. Our work concentrates on InAs quantum dash nanostructures grown on InP substrate, intended for applications in the 1.55 μm telecom window. InAs/InP quantum dash based lasers, in particular, have demonstrated efficient mode locking in single section Fabry-Perot configurations. The flat optical spectrum of about 12 nm, combined with the narrow RF beat note linewidth of about 10 kHz make them a promising technology for optical frequency comb generation. Coherence between spectral modes was assessed by means of spectral phase measurements. The parabolic spectral phase profile indicates that short pulses can be obtained provided the intracavity dispersion can be compensated by inserting a single mode fiber.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
Advanced optical pulse characterization methods are essential for high-speed optical communicatio... more Advanced optical pulse characterization methods are essential for high-speed optical communications. Recently non-iterative characterization of general optical pulses using sinusoidal optical phase modulation has been reported [12]. However, the usable phase ...
A novel two-section tunable laser diode is demonstrated by etching slots into the laser ridge. A ... more A novel two-section tunable laser diode is demonstrated by etching slots into the laser ridge. A discontinuous tuning-range of 30 nm was achieved with a SMSR of 38 dB. A wavelength switching time of 1.5 ns is demonstrated.
ABSTRACT Wavelength conversion via four-wave mixing (FWM) schemes of high-bit rate data formats a... more ABSTRACT Wavelength conversion via four-wave mixing (FWM) schemes of high-bit rate data formats are conventionally achieved using a strong pump source and a secondary nonlinear device, such as highly nonlinear fibre [1] or semiconductor optical amplifier [2]. In this work we obviate the need for a secondary nonlinear device, and achieve wavelength-conversion of high repetition-rate pulse trains by externally injecting a strong optical tone directly into the cavity of the 48GHz repetition-rate passively mode-locked semiconductor laser, achieving wavelength-conversion via partially-degenerate FWM. For the first time to our knowledge, we provide experimental results of the wavelength tunability of this wavelength-conversion scheme and show that the entire signal spectrum undergoes parametrically conversion.
We propose and verify the use of the power spectral density of the FM noise spectrum to study the... more We propose and verify the use of the power spectral density of the FM noise spectrum to study the phase noise relationship between the four-wave mixing components.
Conference on Lasers and Electro-Optics 2012, 2012
ABSTRACT Device characterizations of QDash semiconductor lasers as a subchannel comb generator ar... more ABSTRACT Device characterizations of QDash semiconductor lasers as a subchannel comb generator are presented, including measurements of electric field, optical linewidth, and mode coherence out to 1.5THz spectral mode separation.
Opto-Ireland 2005: Optoelectronics, Photonic Devices, and Optical Networks, 2005
Future high-speed optical communications networks operating at data rates in excess of 100Gbit/s ... more Future high-speed optical communications networks operating at data rates in excess of 100Gbit/s per channel will require a sensitive and ultrafast technique for precise optical signal monitoring. 1 The standard way of characterising high-speed optical signals to use a fast photodetector in conjunction with a high-speed oscilloscope. However, this method is limited to a maximum data rate of approximately 40Gbit/s. An alternative is to employ all-optical sampling techniques based on ultrafast optical nonlinearities present in optical fibres, optical crystals and semiconductors. One such nonlinearity is the optical-to-electrical process of Two-Photon Absorption (TPA) in a semiconductor. This paper presents an optical sampling technique based on TPA in a specially designed semiconductor microcavity. By incorporating the microcavity design, we are able to enhance the TPA efficiency to a level that can be used for high-speed optical sampling.
European Conference and Exhibition on Optical Communication, 2012
Next generation optical access networks will require low cost lasers in conjunction with network ... more Next generation optical access networks will require low cost lasers in conjunction with network flexibility and higher data rates. This work presents the direct modulation of a low cost tuneable slotted Fabry-Pérot laser (tuneable over 14nm) with AM-OFDM. Characteristics of this dual section laser are presented and transmission of 10Gb/s over 50km is achieved with this device.
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT Phase locked frequency combs spanning > 1.5 THz have been generated using passive... more ABSTRACT Phase locked frequency combs spanning > 1.5 THz have been generated using passively mode locked quantum dash based lasers emitting at 1.55 µm. These combs are particularly suited for future OFDM transmission systems.
Lasers with narrow-linewidth emission are a key component for higher-order modulation formats. We... more Lasers with narrow-linewidth emission are a key component for higher-order modulation formats. We report on discrete-mode laser diodes designed for narrow-linewidth emission and demonstrate linewidths less than 80 kHz. Using these devices in quadrature phase shift keying and 16-quadrature amplitude modulation transmission setups, similar performance to that of an external cavity laser is demonstrated.
China-Ireland International Conference on Information and Communications Technologies (CIICT 2008), 2008
ABSTRACT This paper investigates the use of a two-photon absorption photodetector for all-optical... more ABSTRACT This paper investigates the use of a two-photon absorption photodetector for all-optical signal processing. Continuous, wavelength selective chromatic dispersion monitoring in a high-speed multi-wavelength system is discussed. The reduction of multiple access interference in an optical code division multiple access network using a TPA photodetector is also presented.
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Papers by Liam P Barry