Eamonn Martin - Academia.edu (original) (raw)

Papers by Eamonn Martin

Optical Fiber Communication Conference (OFC) 2022

We demonstrate the successful generation of 28.2 and 35.3 GHz mm-wave signals through optical inj... more We demonstrate the successful generation of 28.2 and 35.3 GHz mm-wave signals through optical injection locking and direct modulation of a DFB laser. The low phase noise mm-wave signal generated supports 5G compatible OFDM signals.

A 5G millimeter-wave radio over fibre optical fronthaul system based on optical heterodyning, uti... more A 5G millimeter-wave radio over fibre optical fronthaul system based on optical heterodyning, utilising an externally injected gain switched distributed feedback laser, is successfully demonstrated. Five bands of UF-OFDM are transmitted over 25 km of fibre and a 28 GHz Vivaldi Antenna wireless link. Transmission performance below the 7% FEC limit is achieved with an aggregate total data rate of 4.56 Gb/s

Conference on Lasers and Electro-Optics, 2020

Application of two mutually injection-locked gain-switched optical frequency combs for near-infra... more Application of two mutually injection-locked gain-switched optical frequency combs for near-infrared spectroscopy of H2S in air is demonstrated. The high phase correlation between OFCs allows measurement sensitivities of 740 ppmv using a compact, flexible device.

Journal of Lightwave Technology, 2021

A novel dual-stage optical frequency comb (OFC) demultiplexer, for use in a photonic millimeter-w... more A novel dual-stage optical frequency comb (OFC) demultiplexer, for use in a photonic millimeter-wave (mmW) generator, is demonstrated. Unlike other demultiplexing techniques, the proposed method features a single optical path for both tones used for the mmW generation, thus eliminating the challenges related to the mismatch of path lengths. In addition, the use of active demultiplexing provides filtering, amplification and data modulation of the comb tones, all in a single device. In this article, we demonstrate the operational principle of the dual-stage active demultiplexer-enabled mmW generation, verify the quality (beat tone width ∼13 Hz) and stability (power fluctuation ∼0.26 dB) of the generated mmW signal and validate the performance of an A-RoF system employing the proposed device. For the system demonstration, 64-QAM UF-OFDM signals, at frequencies of 29.5 and 38 GHz, are generated and transmitted over 25 km of single-mode fiber. A BER of 3.2e-4 for 29.5 GHz and 1.6e-4 for 38 GHz is achieved without the use of optical amplifiers, showing the great potential of the proposed technique. Finally, a case study of an A-RoF distribution system, employing three different demultiplexing techniques, is presented. We demonstrate that the proposed transmitter, in comparison to other demultiplexing techniques, provides a larger power budget (> 6 dB) that can be used to extend the reach of the system and/or increase the number of remote radio units served using a single OFC.

Optics Express, 2021

The measurement of distance plays an important role in many aspects of modern societies. In this ... more The measurement of distance plays an important role in many aspects of modern societies. In this paper, an absolute distance measurement method for arbitrary distance is proposed and demonstrated using mode-resolved spectral interferometry with a gain-switched dual comb. An accuracy of 12 µm, when compared to a He-Ne fringe counting laser interferometer, for a displacement up to 2.5 m is demonstrated by tuning the repetition frequency of the dual comb from 1.1 GHz to 1.4 GHz. The compact measurement system based on a gain-switched dual comb breaks the constraint of periodic ambiguity. The simplification and improvements are significant for further industrial applications.

2014 The European Conference on Optical Communication (ECOC), 2014

A 25 Gb/s OFDM 60 GHz radio over fibre transmission system employing an externally injected gain ... more A 25 Gb/s OFDM 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. Transmission performance below the 7% FEC limit is achieved over 25 km of SSMF with 2 m wireless.

2020 European Conference on Optical Communications (ECOC), 2020

A simple, highly efficient scheme of generating mmW signals, employing an optical frequency comb ... more A simple, highly efficient scheme of generating mmW signals, employing an optical frequency comb and a dual-stage active demultiplexer is proposed. We experimentally demonstrate the generation and distribution of 38 GHz 64-QAM UF-OFDM signal over 25 km of fibre, achieving a BER of 1.6 e-4.

Optics Express, 2020

A monolithically integrated dual-channel optical frequency comb source is demonstrated in this pa... more A monolithically integrated dual-channel optical frequency comb source is demonstrated in this paper. Three lasers are integrated on a single chip using a regrowth-free fabrication process in a master-slave-slave configuration. The master laser’s power is split equally using a 1x2 multimode interference coupler and injection locks the two slave lasers. The slave lasers are gain-switched to produce dual optical frequency combs at 4.1 GHz and 5 GHz. To the best of our knowledge, this is the first demonstration of a dual optical frequency comb source with all light sources monolithically integrated in a photonic integrated circuit (PIC).

Sensors, 2019

A custom-designed gain-switched frequency comb (GSFC) source was passively coupled to a medium fi... more A custom-designed gain-switched frequency comb (GSFC) source was passively coupled to a medium finesse (F ≈ 522) cavity in off-axis configuration for the detection of ammonia (14NH3) in static dry air. The absorption of ammonia was detected in the near infrared spectral region between 6604 and 6607 cm−1 using a Fourier transform detection scheme. More than 30 lines of the GSFC output (free spectral range 2.5 GHz) overlapped with the strongest ro-vibrational ammonia absorption features in that spectral region. With the cavity in off-axis configuration, an NH3 detection limit of ∼3.7 ppmv in 20 s was accomplished in a laboratory environment. The experimental performance of the prototype spectrometer was characterized; advantages, drawbacks and the potential for future applications are discussed.

Journal of Lightwave Technology, 2018

The millimeter-wave (mm-wave) frequency band has emerged as a means to overcome current radio fre... more The millimeter-wave (mm-wave) frequency band has emerged as a means to overcome current radio frequency spectral limitations and represents an interesting solution to fulfill the bandwidth and networking requirements of fifth generation (5G) mobile communications and beyond. Photonic generation of these frequencies holds advantages over electronic methods in terms of cost and effective network distribution. Due to their coherent nature, optical frequency combs (OFC) are a promising solution for the efficient generation of mm-wave frequencies. The work outlined examines the use of OFCs in a mm-wave radio-over-fiber (RoF) heterodyne system with regard to the specific requirements of a 5G candidate waveform, universally filtered orthogonal frequency division multiplexing. Through experimentation and simulation, the key limitations of linewidth, effective path length difference, and relative intensity noise (RIN) are explored. Results are presented, in terms of error vector magnitude (EVM), for a wide range of system parameters highlighting important considerations to be taken in designing future mm-wave RoF systems employing OFCs. Performance of ∼5% EVM using single sideband modulation is achieved for optimized system conditions and an RIN level of −132 dB/Hz.

IEEE Photonics Technology Letters, 2017

Millimeter-wave communications may be harnessed to help meet future 5G network bandwidth requirem... more Millimeter-wave communications may be harnessed to help meet future 5G network bandwidth requirements, but the generation of these frequencies in the electronic domain can be difficult and costly. Photonic techniques, such as optical heterodyning, can be exploited to generate millimeter-wave frequencies in a manner which is efficient and compatible with fiber transport infrastructure. In this letter, analog radio-overfiber transmission of five bands of UF-OFDM, with optical heterodyning around 60 GHz, is experimentally demonstrated over 25 km SSMF, and performance well below the forward error correction limit is achieved for an aggregate raw bit rate of 4.56 Gb/s. Additionally, the importance of precise optical phase correlation in these systems is highlighted with respect to future 5G system requirements.

Applied Sciences, 2017

Microwave-based all-analogue (orthogonal) subcarrier multiplexing (SCM) permits a direct processi... more Microwave-based all-analogue (orthogonal) subcarrier multiplexing (SCM) permits a direct processing of baseband data at Gbit/s while achieving low power consumption, low latency, low cost, and tolerance to dispersion. A key figure of merit in any SCM link is the sensitivity in the receiver, which depends on the transmitter, the link and the receiver. By analysing the impact of the nonlinearities of an optical IQ modulator in the presence of optical noise, sensitivities are mathematically estimated as a function of the optical modulation index (OMI) at the transmitter. The results are verified with simulations achieving a good agreement with the mathematical model. The theoretical model provided can be employed as a tool to predict the best achievable sensitivities and the optimum OMI in broadband SCM and orthogonal SCM links.

Optical Fiber Communication Conference, 2016

We demonstrate the polarization insensitive wavelength conversion of polarization-multiplexed Nyq... more We demonstrate the polarization insensitive wavelength conversion of polarization-multiplexed Nyquist QPSK superchannel with an overall data rate of 200 Gb/s using four-wave mixing in a co-polarized pump and co-propagating configuration in a SOA.

Optical Fiber Communication Conference, 2016

Journal of Lightwave Technology, 2016

Electro-optical transceivers can be implemented employing all-analogue signal processing in order... more Electro-optical transceivers can be implemented employing all-analogue signal processing in order to achieve low values of power consumption and latency. This paper shows that the spectral efficiency of such solutions can be increased by combining orthogonal multicarrier techniques and off-the-shelf microwave components. A real-time 108 Gbit/s experiment was performed emulating a wavelength division multiplexing (WDM) system composed of five optical channels. The optical carriers were provided by an externally injected gain switched optical frequency comb. Each optical channel transmitted a 21.6 Gbit/s orthogonal subcarrier multiplexing (SCM) signal that was modulated and demodulated in the electrical domain without the requirement for digital signal processing. The net data rate remained higher than 100 Gbit/s after taking into account forward error correction overheads. The use of orthogonally overlapping subchannels achieves an unprecedented spectral efficiency in all-analogue real-time broadband WDM/SCM links.

Journal of Lightwave Technology, 2015

This paper studies the key aspects of an optical link which transmits a broadband microwave filte... more This paper studies the key aspects of an optical link which transmits a broadband microwave filter bank multicarrier (FBMC) signal. The work is presented in the context of creating an all-analogue real-time multi-gigabit orthogonal frequency division multiplexing (OFDM) electro-optical transceiver for short range and high capacity data center networks. Passive microwave filters are used to perform the pulse shaping of the bit streams, allowing an orthogonal transmission without the necessity of digital signal processing (DSP). Accordingly, a cyclic prefix that would cause a reduction in the net data rate is not required. An experiment consisting of three orthogonally spaced 2.7 Gbaud quadrature phase shift keyed (QPSK) subchannels demonstrates that the spectral efficiency of traditional DSP-less subcarrier multiplexed (SCM) links can be potentially doubled. A sensitivity of-29.5 dBm is achieved in a 1 kilometer link.

Microwave Photonics (MWP) and the 2014 9th Asia-Pacific Microwave Photonics Conference (APMP) 2014 International Topical Meeting on, 2014

ABSTRACT A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre tran... more ABSTRACT A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. The effects of nonlinear distortions, due to a high launch power, on system performance are experimentally investigated. Single sideband (SSB) OFDM is employed to reduce the fibre nonlinearity effects. Keywords—radio over fibre (RoF), gain-switching, optical comb source, orthogonal frequency division

IEEE Photonics Technology Letters, 2015

We propose a 60-GHz orthogonal frequency division multiplexing (OFDM) radio over fiber system bas... more We propose a 60-GHz orthogonal frequency division multiplexing (OFDM) radio over fiber system based on direct modulation-direct detection using an externally injected gainswitched DFB laser with adaptive modulation format. Power fading due to chromatic dispersion is mitigated by optimizing the bias current. Adaptive modulation for OFDM is used to improve the signal transmission performance. A 15.31-Gb/s 60-GHz OFDM signal generation and transmission over 25-km standard single-mode fiber is experimentally demonstrated.

Journal of Lightwave Technology, 2015

A 25-Gb/s OFDM 60-GHz radio over fiber (RoF) transmission system employing a gain switched DFB la... more A 25-Gb/s OFDM 60-GHz radio over fiber (RoF) transmission system employing a gain switched DFB laser for millimeter-wave generation is demonstrated. Transmission performance below the 7% FEC limit is achieved over 50 km of fiber initially by employing precompensation. This precompensation overcomes phase noise caused by the optical phase decorrelation induced by chromatic dispersion on the two optical channels separated by 60 GHz. An externally injected gain switched laser is subsequently employed to eradicate the need for the precompensation, thus reducing phase noise and increasing the tolerance to the induced time delay between the optical tones. Transmission performance below the 7% limit is achieved over 25 km of fiber with 2-m wireless transmission in this case. Index Terms-Gain-switching, optical comb source, orthogonal frequency division multiplexing, phase noise, radio over fibre (RoF).

IEEE Photonics Technology Letters, 2015

We propose a 60-GHz orthogonal frequency-division multiplexing radio over fiber system based on d... more We propose a 60-GHz orthogonal frequency-division multiplexing radio over fiber system based on direct modulation-direct detection using an externally injected gain-switched distributed feedback (DFB) laser. External injection from a master laser into the gain-switched DFB laser is used to mitigate chirp in the directly modulated DFB laser and 25-km fiber transmission is investigated. Power fading due to multipath transmission induced by fiber chromatic dispersion is theoretically analyzed and experimentally demonstrated.

Optical Fiber Communication Conference (OFC) 2022

We demonstrate the successful generation of 28.2 and 35.3 GHz mm-wave signals through optical inj... more We demonstrate the successful generation of 28.2 and 35.3 GHz mm-wave signals through optical injection locking and direct modulation of a DFB laser. The low phase noise mm-wave signal generated supports 5G compatible OFDM signals.

A 5G millimeter-wave radio over fibre optical fronthaul system based on optical heterodyning, uti... more A 5G millimeter-wave radio over fibre optical fronthaul system based on optical heterodyning, utilising an externally injected gain switched distributed feedback laser, is successfully demonstrated. Five bands of UF-OFDM are transmitted over 25 km of fibre and a 28 GHz Vivaldi Antenna wireless link. Transmission performance below the 7% FEC limit is achieved with an aggregate total data rate of 4.56 Gb/s

Conference on Lasers and Electro-Optics, 2020

Application of two mutually injection-locked gain-switched optical frequency combs for near-infra... more Application of two mutually injection-locked gain-switched optical frequency combs for near-infrared spectroscopy of H2S in air is demonstrated. The high phase correlation between OFCs allows measurement sensitivities of 740 ppmv using a compact, flexible device.

Journal of Lightwave Technology, 2021

A novel dual-stage optical frequency comb (OFC) demultiplexer, for use in a photonic millimeter-w... more A novel dual-stage optical frequency comb (OFC) demultiplexer, for use in a photonic millimeter-wave (mmW) generator, is demonstrated. Unlike other demultiplexing techniques, the proposed method features a single optical path for both tones used for the mmW generation, thus eliminating the challenges related to the mismatch of path lengths. In addition, the use of active demultiplexing provides filtering, amplification and data modulation of the comb tones, all in a single device. In this article, we demonstrate the operational principle of the dual-stage active demultiplexer-enabled mmW generation, verify the quality (beat tone width ∼13 Hz) and stability (power fluctuation ∼0.26 dB) of the generated mmW signal and validate the performance of an A-RoF system employing the proposed device. For the system demonstration, 64-QAM UF-OFDM signals, at frequencies of 29.5 and 38 GHz, are generated and transmitted over 25 km of single-mode fiber. A BER of 3.2e-4 for 29.5 GHz and 1.6e-4 for 38 GHz is achieved without the use of optical amplifiers, showing the great potential of the proposed technique. Finally, a case study of an A-RoF distribution system, employing three different demultiplexing techniques, is presented. We demonstrate that the proposed transmitter, in comparison to other demultiplexing techniques, provides a larger power budget (> 6 dB) that can be used to extend the reach of the system and/or increase the number of remote radio units served using a single OFC.

Optics Express, 2021

The measurement of distance plays an important role in many aspects of modern societies. In this ... more The measurement of distance plays an important role in many aspects of modern societies. In this paper, an absolute distance measurement method for arbitrary distance is proposed and demonstrated using mode-resolved spectral interferometry with a gain-switched dual comb. An accuracy of 12 µm, when compared to a He-Ne fringe counting laser interferometer, for a displacement up to 2.5 m is demonstrated by tuning the repetition frequency of the dual comb from 1.1 GHz to 1.4 GHz. The compact measurement system based on a gain-switched dual comb breaks the constraint of periodic ambiguity. The simplification and improvements are significant for further industrial applications.

2014 The European Conference on Optical Communication (ECOC), 2014

A 25 Gb/s OFDM 60 GHz radio over fibre transmission system employing an externally injected gain ... more A 25 Gb/s OFDM 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. Transmission performance below the 7% FEC limit is achieved over 25 km of SSMF with 2 m wireless.

2020 European Conference on Optical Communications (ECOC), 2020

A simple, highly efficient scheme of generating mmW signals, employing an optical frequency comb ... more A simple, highly efficient scheme of generating mmW signals, employing an optical frequency comb and a dual-stage active demultiplexer is proposed. We experimentally demonstrate the generation and distribution of 38 GHz 64-QAM UF-OFDM signal over 25 km of fibre, achieving a BER of 1.6 e-4.

Optics Express, 2020

A monolithically integrated dual-channel optical frequency comb source is demonstrated in this pa... more A monolithically integrated dual-channel optical frequency comb source is demonstrated in this paper. Three lasers are integrated on a single chip using a regrowth-free fabrication process in a master-slave-slave configuration. The master laser’s power is split equally using a 1x2 multimode interference coupler and injection locks the two slave lasers. The slave lasers are gain-switched to produce dual optical frequency combs at 4.1 GHz and 5 GHz. To the best of our knowledge, this is the first demonstration of a dual optical frequency comb source with all light sources monolithically integrated in a photonic integrated circuit (PIC).

Sensors, 2019

A custom-designed gain-switched frequency comb (GSFC) source was passively coupled to a medium fi... more A custom-designed gain-switched frequency comb (GSFC) source was passively coupled to a medium finesse (F ≈ 522) cavity in off-axis configuration for the detection of ammonia (14NH3) in static dry air. The absorption of ammonia was detected in the near infrared spectral region between 6604 and 6607 cm−1 using a Fourier transform detection scheme. More than 30 lines of the GSFC output (free spectral range 2.5 GHz) overlapped with the strongest ro-vibrational ammonia absorption features in that spectral region. With the cavity in off-axis configuration, an NH3 detection limit of ∼3.7 ppmv in 20 s was accomplished in a laboratory environment. The experimental performance of the prototype spectrometer was characterized; advantages, drawbacks and the potential for future applications are discussed.

Journal of Lightwave Technology, 2018

The millimeter-wave (mm-wave) frequency band has emerged as a means to overcome current radio fre... more The millimeter-wave (mm-wave) frequency band has emerged as a means to overcome current radio frequency spectral limitations and represents an interesting solution to fulfill the bandwidth and networking requirements of fifth generation (5G) mobile communications and beyond. Photonic generation of these frequencies holds advantages over electronic methods in terms of cost and effective network distribution. Due to their coherent nature, optical frequency combs (OFC) are a promising solution for the efficient generation of mm-wave frequencies. The work outlined examines the use of OFCs in a mm-wave radio-over-fiber (RoF) heterodyne system with regard to the specific requirements of a 5G candidate waveform, universally filtered orthogonal frequency division multiplexing. Through experimentation and simulation, the key limitations of linewidth, effective path length difference, and relative intensity noise (RIN) are explored. Results are presented, in terms of error vector magnitude (EVM), for a wide range of system parameters highlighting important considerations to be taken in designing future mm-wave RoF systems employing OFCs. Performance of ∼5% EVM using single sideband modulation is achieved for optimized system conditions and an RIN level of −132 dB/Hz.

IEEE Photonics Technology Letters, 2017

Millimeter-wave communications may be harnessed to help meet future 5G network bandwidth requirem... more Millimeter-wave communications may be harnessed to help meet future 5G network bandwidth requirements, but the generation of these frequencies in the electronic domain can be difficult and costly. Photonic techniques, such as optical heterodyning, can be exploited to generate millimeter-wave frequencies in a manner which is efficient and compatible with fiber transport infrastructure. In this letter, analog radio-overfiber transmission of five bands of UF-OFDM, with optical heterodyning around 60 GHz, is experimentally demonstrated over 25 km SSMF, and performance well below the forward error correction limit is achieved for an aggregate raw bit rate of 4.56 Gb/s. Additionally, the importance of precise optical phase correlation in these systems is highlighted with respect to future 5G system requirements.

Applied Sciences, 2017

Microwave-based all-analogue (orthogonal) subcarrier multiplexing (SCM) permits a direct processi... more Microwave-based all-analogue (orthogonal) subcarrier multiplexing (SCM) permits a direct processing of baseband data at Gbit/s while achieving low power consumption, low latency, low cost, and tolerance to dispersion. A key figure of merit in any SCM link is the sensitivity in the receiver, which depends on the transmitter, the link and the receiver. By analysing the impact of the nonlinearities of an optical IQ modulator in the presence of optical noise, sensitivities are mathematically estimated as a function of the optical modulation index (OMI) at the transmitter. The results are verified with simulations achieving a good agreement with the mathematical model. The theoretical model provided can be employed as a tool to predict the best achievable sensitivities and the optimum OMI in broadband SCM and orthogonal SCM links.

Optical Fiber Communication Conference, 2016

We demonstrate the polarization insensitive wavelength conversion of polarization-multiplexed Nyq... more We demonstrate the polarization insensitive wavelength conversion of polarization-multiplexed Nyquist QPSK superchannel with an overall data rate of 200 Gb/s using four-wave mixing in a co-polarized pump and co-propagating configuration in a SOA.

Optical Fiber Communication Conference, 2016

Journal of Lightwave Technology, 2016

Electro-optical transceivers can be implemented employing all-analogue signal processing in order... more Electro-optical transceivers can be implemented employing all-analogue signal processing in order to achieve low values of power consumption and latency. This paper shows that the spectral efficiency of such solutions can be increased by combining orthogonal multicarrier techniques and off-the-shelf microwave components. A real-time 108 Gbit/s experiment was performed emulating a wavelength division multiplexing (WDM) system composed of five optical channels. The optical carriers were provided by an externally injected gain switched optical frequency comb. Each optical channel transmitted a 21.6 Gbit/s orthogonal subcarrier multiplexing (SCM) signal that was modulated and demodulated in the electrical domain without the requirement for digital signal processing. The net data rate remained higher than 100 Gbit/s after taking into account forward error correction overheads. The use of orthogonally overlapping subchannels achieves an unprecedented spectral efficiency in all-analogue real-time broadband WDM/SCM links.

Journal of Lightwave Technology, 2015

This paper studies the key aspects of an optical link which transmits a broadband microwave filte... more This paper studies the key aspects of an optical link which transmits a broadband microwave filter bank multicarrier (FBMC) signal. The work is presented in the context of creating an all-analogue real-time multi-gigabit orthogonal frequency division multiplexing (OFDM) electro-optical transceiver for short range and high capacity data center networks. Passive microwave filters are used to perform the pulse shaping of the bit streams, allowing an orthogonal transmission without the necessity of digital signal processing (DSP). Accordingly, a cyclic prefix that would cause a reduction in the net data rate is not required. An experiment consisting of three orthogonally spaced 2.7 Gbaud quadrature phase shift keyed (QPSK) subchannels demonstrates that the spectral efficiency of traditional DSP-less subcarrier multiplexed (SCM) links can be potentially doubled. A sensitivity of-29.5 dBm is achieved in a 1 kilometer link.

Microwave Photonics (MWP) and the 2014 9th Asia-Pacific Microwave Photonics Conference (APMP) 2014 International Topical Meeting on, 2014

ABSTRACT A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre tran... more ABSTRACT A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. The effects of nonlinear distortions, due to a high launch power, on system performance are experimentally investigated. Single sideband (SSB) OFDM is employed to reduce the fibre nonlinearity effects. Keywords—radio over fibre (RoF), gain-switching, optical comb source, orthogonal frequency division

IEEE Photonics Technology Letters, 2015

We propose a 60-GHz orthogonal frequency division multiplexing (OFDM) radio over fiber system bas... more We propose a 60-GHz orthogonal frequency division multiplexing (OFDM) radio over fiber system based on direct modulation-direct detection using an externally injected gainswitched DFB laser with adaptive modulation format. Power fading due to chromatic dispersion is mitigated by optimizing the bias current. Adaptive modulation for OFDM is used to improve the signal transmission performance. A 15.31-Gb/s 60-GHz OFDM signal generation and transmission over 25-km standard single-mode fiber is experimentally demonstrated.

Journal of Lightwave Technology, 2015

A 25-Gb/s OFDM 60-GHz radio over fiber (RoF) transmission system employing a gain switched DFB la... more A 25-Gb/s OFDM 60-GHz radio over fiber (RoF) transmission system employing a gain switched DFB laser for millimeter-wave generation is demonstrated. Transmission performance below the 7% FEC limit is achieved over 50 km of fiber initially by employing precompensation. This precompensation overcomes phase noise caused by the optical phase decorrelation induced by chromatic dispersion on the two optical channels separated by 60 GHz. An externally injected gain switched laser is subsequently employed to eradicate the need for the precompensation, thus reducing phase noise and increasing the tolerance to the induced time delay between the optical tones. Transmission performance below the 7% limit is achieved over 25 km of fiber with 2-m wireless transmission in this case. Index Terms-Gain-switching, optical comb source, orthogonal frequency division multiplexing, phase noise, radio over fibre (RoF).

IEEE Photonics Technology Letters, 2015

We propose a 60-GHz orthogonal frequency-division multiplexing radio over fiber system based on d... more We propose a 60-GHz orthogonal frequency-division multiplexing radio over fiber system based on direct modulation-direct detection using an externally injected gain-switched distributed feedback (DFB) laser. External injection from a master laser into the gain-switched DFB laser is used to mitigate chirp in the directly modulated DFB laser and 25-km fiber transmission is investigated. Power fading due to multipath transmission induced by fiber chromatic dispersion is theoretically analyzed and experimentally demonstrated.