Showing papers by "Periklis Petropoulos published in 2012"
TL;DR: Single-laser 32.5 Tbit/s 16QAM Nyquist-WDM transmission with 325 carriers over 227 km at a net spectral efficiency of 6.4 bit/s/Hz is reported.
Abstract: We demonstrate single-laser 32.5 Tbit/s 16QAM Nyquist wavelength division multiplexing transmission over a total length of 227 km of SMF-28 without optical dispersion compensation. A number of 325 optical carriers is derived from a single laser and encoded with dual-polarization 16QAM data using sinc-shaped Nyquist pulses. As we use no guard bands, the carriers have a spacing of 12.5 GHz equal to the symbol rate or Nyquist bandwidth of the data. We achieve a net spectral efficiency of 6.4 bit/s/Hz using a software-defined transmitter, which generates the electric drive signals for the electro-optic modulator in real time.
132 citations
TL;DR: In this paper, the authors show how non-silica fibers are of benefit not only because their broad mid-IR transparency enables continuum generation in the 2-5 µm region but also since the high intrinsic nonlinearity of the glasses reduces the power-threshold for devices at wavelengths below 2µm.
86 citations
TL;DR: Two fiber-based multichannel 2R regeneration techniques for return-to-zero-on-off keying based on 1) dispersion managed systems and 2) direction and polarization multiplexing are described.
Abstract: Multiwavelength all-optical regeneration has the potential to substantially increase both the capacity and scalability of future optical networks. In this paper, we review recent promising developments in this area. First, we recall the basic principles of multichannel regeneration of high bit rate signals in optical communication systems before discussing the current technological approaches. We then describe in detail two fiber-based multichannel 2R regeneration techniques for return-to-zero-on-off keying based on 1) dispersion managed systems and 2) direction and polarization multiplexing. We present results illustrating the levels of performance so far achieved and discuss various practical issues and prospects for further performance enhancement.
48 citations
16 Sep 2012
TL;DR: In this paper, the first demonstration of a hollow core photonic bandgap fiber suitable for high-rate data transmission at 2µm was presented using a custom built Thulium doped fiber amplifier, error-free 8Gbit/s transmission in an optically amplified data channel at 2008nm was reported.
Abstract: The first demonstration of a hollow core photonic bandgap fiber suitable for high-rate data transmission at 2µm is presented. Using a custom built Thulium doped fiber amplifier, error-free 8Gbit/s transmission in an optically amplified data channel at 2008nm is reported for the first time.
40 citations
TL;DR: This study addresses both theoretically and experimentally the important issue of how a PSA-based signal regenerator works with more realistic random broadband amplitude/phase noise distributions and presents a simplified regenerator implementation providing highly stable operation and representing a significant further step toward a practical device.
Abstract: The performance of future ultralong-haul communication systems exploiting phase-encoded signals is likely to be compromised by nonlinear phase noise generated during signal transmission. One potential way to mitigate against nonlinear phase noise is to use phase-sensitive amplifiers (PSAs) that have been demonstrated to help remove such phase noise as well as to provide simultaneous signal amplitude noise suppression when operated in saturation. Recently, we have shown that a PSA-based signal regenerator based on degenerate four-wave mixing could be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). However, this scheme was tested only with relatively high-frequency deterministic perturbations applied to the signal. Here, we address both theoretically and experimentally the important issue of how such a regenerator works with more realistic random broadband amplitude/phase noise distributions. Good regenerative performance is demonstrated and our study also illustrates an additional unique feature of PSA-based regenerators-namely error correction for differentially encoded signals when placed in front of a DPSK receiver. Furthermore, we present a simplified regenerator implementation providing highly stable operation and representing a significant further step toward a practical device.
37 citations
TL;DR: In this article, an adaptive pulse shaping system exploiting optimization algorithms (evolution strategy-ES) allows for automatic convergence to the desired spectrum, which can be used to generate even broader spectra or indeed spectra exhibiting more exotic shapes.
Abstract: This paper investigates the nonlinear generation of ultra-flat broadband spectra suited to communication applications. The technique is based on the inclusion of a linear pulse shaping element prior to a nonlinear fiber, where highly controllable spectral broadening is enabled. An adaptive pulse shaping system exploiting optimization algorithms (evolution strategy-ES) allows for automatic convergence to the desired spectrum. Using this technique, a spectrum exhibiting a 3-dB bandwidth of ~12 nm and a 0.5-dB bandwidth of ~8 nm is reported. The technique can be used to generate even broader spectra or indeed spectra exhibiting more exotic shapes.
26 citations
TL;DR: In this paper, a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network compatible manner in which only the (noisy) signal is present at the device input (black-box operation).
Abstract: The performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phase-encoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach.
22 citations
TL;DR: It is suggested and demonstrated how fiber optic parametric amplifiers can be used to enhance all of these key comb parameters, allowing frequency span multiplication, low noise amplification with simultaneous comb spectrum flattening, and improvement in optical tone-to-noise ratio through various phase insensitive as well as phase sensitive implementations.
Abstract: Low noise optical frequency combs consist of equally spaced narrow-linewidth optical tones. They are useful in many applications including, for example, line-by-line pulse shaping, THz generation, and coherent communications. In such applications the comb spacing, extent of spectral coverage, degree of spectral flatness, optical tone power and tone-to-noise ratio represent key considerations. Simultaneously achieving the level of performance required in each of these parameters is often challenging using existing comb generation technologies. Herein we suggest and demonstrate how fiber optic parametric amplifiers can be used to enhance all of these key comb parameters, allowing frequency span multiplication, low noise amplification with simultaneous comb spectrum flattening, and improvement in optical tone-to-noise ratio through various phase insensitive as well as phase sensitive implementations.
21 citations
04 Mar 2012
TL;DR: In this article, a technique that allows the all-optical quantization of M-PSK signals using a parametric mixing process is discussed, including recent experimental demonstrations of high baud rate QPSK regeneration, and issues regarding future scalability.
Abstract: A technique that allows the all-optical quantization of M-PSK signals using a parametric mixing process is discussed, including recent experimental demonstrations of high baud rate QPSK regeneration, and issues regarding future scalability of the scheme.
18 citations
04 Mar 2012
TL;DR: Modulation formats for realizing high data rate and high power sensitivity using coherent reception with low noise-figure optical preamplification are experimentally investigated.
Abstract: We experimentally investigate modulation formats for realizing high data rate and high power sensitivity using coherent reception with low noise-figure optical preamplification. 40 Gbit/s PS-QPSK exhibits a sensitivity of 4.3 photons/bit while 100 Gbit/s PDM-QPSK exhibits a sensitivity of 5.3 photons/bit at 3.8×10−3 BER.
16 citations
TL;DR: This work proposes and experimentally study the passive coherent optical addition of complex modulation format signals through the use of a delay line interferometer followed by a temporal gate to increase the encoded bits per symbol and consequently, the spectral efficiency of an incident signal.
Abstract: We propose and experimentally study the passive coherent optical addition of complex modulation format signals through the use of a delay line interferometer followed by a temporal gate to increase the encoded bits per symbol and consequently, the spectral efficiency of an incident signal. Modulation format conversion and packet compression are demonstrated as two possible application examples. A variety of modulation formats can be accommodated, whereas higher compression factors can be achieved through the use of a cascade of delay line interferometers.
TL;DR: Results show an improvement in the Error Vector Magnitude (EVM) and a reduction of almost a factor of 2 in the phase noise of the signal after regeneration for various noise levels at the input.
Abstract: We experimentally demonstrate phase regeneration of a 40-Gb/s differential phase shift keying (DPSK) signal in a 1.7-m long highly nonlinear lead silicate W-type fiber using a degenerate two-pump phase-sensitive amplifier (PSA). Results show an improvement in the Error Vector Magnitude (EVM) and a reduction of almost a factor of 2 in the phase noise of the signal after regeneration for various noise levels at the input.
TL;DR: In this article, the authors demonstrate 32.5 Tbit/s 16QAM Nyquist WDM transmission over a total length of 227 km of SMF-28 without optical dispersion compensation.
Abstract: We demonstrate 32.5 Tbit/s 16QAM Nyquist WDM transmission over a total length of 227 km of SMF-28 without optical dispersion compensation. A number of 325 optical carriers are derived from a single laser and encoded with dual-polarization 16QAM data using sinc-shaped Nyquist pulses. As we use no guard bands, the carriers have a spacing of 12.5 GHz equal to the Nyquist bandwidth of the data. We achieve a high net spectral efficiency of 6.4 bit/s/Hz using a software-defined transmitter which generates the electrical modulator drive signals in real-time.
Proceedings Article•
01 Sep 2012
TL;DR: In this article, a single-laser 32.5 Tbit/s 16QAM Nyquist-WDM transmission with 325 carriers over 227 km at a net spectral efficiency of 6.4 bit/s/Hz is reported.
Abstract: Single-laser 32.5 Tbit/s 16QAM Nyquist-WDM transmission with 325 carriers over 227 km at a net spectral efficiency of 6.4 bit/s/Hz is reported.
04 Mar 2012
TL;DR: In this article, four wave mixing was used to precisely multiply the modulation depth of a phase encoded signal, demonstrating 3-extra effective bits of resolution at 32GHz, enabling a new class of optical signal processing functions.
Abstract: We utilize four wave mixing to precisely multiply the modulation depth of a phase encoded signal, demonstrating 3-extra effective bits of resolution at 32GHz. The technique enables a new class of optical signal processing functions.
16 Sep 2012
TL;DR: In this paper, the authors characterized the chirp of a fast silicon optical modulator using frequency resolved optical gating and optical modulation analysis, and demonstrated that the output of the silicon OO modulator has very small intrinsic chirps across the modulated pulses.
Abstract: The chirp of a fast silicon optical modulator is characterized in this paper. Two diagnostic methods, frequency resolved optical gating and optical modulation analysis, are employed respectively. We demonstrate that the output of silicon optical modulators have very small intrinsic chirp across the modulated pulses.
17 Jun 2012
TL;DR: In this article, the authors demonstrate phase regeneration of a 40-Gb/s DPSK signal in a 1.7m-long lead-silicate fiber using a black-box phase-sensitive amplifier.
Abstract: We demonstrate phase regeneration of a 40-Gb/s DPSK signal in a 1.7m-long lead-silicate fiber using a black-box phase-sensitive amplifier. Results show an improvement in the EVM values of the signal after regeneration for various noise levels.
17 Jun 2012
TL;DR: In this paper, the authors demonstrate and characterize a technique to emulate broadband phase noise by exploiting cross-phase modulation induced spectral broadening, in a highly nonlinear fiber, of a signal from an intense incoherent light source.
Abstract: We demonstrate and characterize a technique to emulate broadband phase noise. This is achieved by exploiting cross-phase modulation induced spectral broadening, in a highly nonlinear fiber, of a signal from an intense incoherent light source.
16 Sep 2012
TL;DR: In this paper, passive coherent optical addition of complex modulation formats using delay line interferometers to increase their bits per symbol and, thus, their spectral efficiency has been investigated and two possible applications are demonstrated as examples.
Abstract: We experimentally study passive coherent optical addition of complex modulation formats using delay line interferometers to increase their bits per symbol and, thus, their spectral efficiency. Two possible applications are demonstrated as examples.
02 Jul 2012
TL;DR: A packet compression scheme based on re-coding of complex modulation formats through the use of a delay line interferometer (DLI) followed by a temporal gate is proposed and numerically demonstrated.
Abstract: We propose and numerically demonstrate a packet compression scheme based on re-coding of complex modulation formats through the use of a delay line interferometer (DLI) followed by a temporal gate. A variety of modulation formats can be accommodated and high compression factors can be obtained by using multiple DLIs to achieve higher order modulation formats.
16 Sep 2012
TL;DR: In this article, the authors describe carrier depletion MZI and ring modulators, cavity structures for modulation enhancement and QCSE modulators which are under development as part of the UK Silicon Photonics project and the European HELIOS project.
Abstract: In the last 8 years carrier depletion modulators have become the mainstream high data rate building block for high performance silicon photonics link. In this work we describe carrier depletion MZI and ring modulators, cavity structures for modulation enhancement and QCSE modulators, all of which are under development as part of the UK Silicon Photonics project and the European HELIOS project.
17 Jun 2012
TL;DR: In this article, the authors review the recent work in the area of optical processing of phase encoded signals, focusing in particular on optical phase quantization, a key functionality for regeneration and test and measurement applications.
Abstract: We review our recent work in the area of optical processing of phase encoded signals, focusing in particular on optical phase quantization - a key functionality for regeneration and test and measurement applications.
Patent•
26 Dec 2012
TL;DR: In this paper, the first and second input optical signals are four-wave mixed (FWM) in a highly nonlinear fiber (HNLF) and generated a beating signal which is supplied to a frequency divider which divides the beat frequency by N, where N is an integer of 2 or more.
Abstract: A device for outputting an optical signal of a desired output frequency based on input optical signals of first and second input frequencies. First and second input optical signals are four-wave mixed (FWM) in a highly nonlinear fiber (HNLF) and generate a beating signal which is supplied to a frequency divider which divides the beat frequency by N, where N is an integer of 2 or more. The divided down signal is used to control an optical modulator to shift the frequency of the first input optical signal by 1/N of the beat frequency. The device may be used for carrier regeneration of phase modulated data signals where the first optical signal is a pump and the second optical signal is the data and the frequency shift moves the pump frequency to the data frequency.
02 Jul 2012
TL;DR: In this article, an experimental demonstration of a technique for the nonlinear generation of tailored broadband optical spectra is presented, which relies on the capability to precisely shape short optical pulses at the input of a highly nonlinear fiber.
Abstract: We present the experimental demonstration of a technique for the nonlinear generation of tailored broadband optical spectra. Our technique relies on the capability to precisely shape short optical pulses at the input of a highly nonlinear fibre. The precise pulse shape that needs to be fed to the nonlinear fibre is calculated from the spectral shape we wish to generate through inverse propagation calculations. A programmable optical filter is then used to transform the pulses of a short-pulse laser to the calculated waveform. An automated evolutionary algorithm is employed to monitor and optimise the filter characteristics. As an application example, we present the generation of a 10 GHz ultra-flat (less than 1 dB power fluctuations), broadband (> 30 nm) optical spectrum, starting from a 2 ps mode-locked laser.
04 Mar 2012
TL;DR: In this article, the authors present the nonlinear generation of ultra-flat broadband spectra suited to high capacity communication signals, and a spectrum covering the full C-band (3dB bandwidth of 35nm) is generated in an adaptable and power-efficient fashion.
Abstract: We present the nonlinear generation of ultra-flat broadband spectra suited to high capacity communication signals. A spectrum covering the full C-band (3-dB bandwidth of 35nm) is generated in an adaptable and power-efficient fashion.
16 Sep 2012
TL;DR: In this article, a comb of phase-locked local oscillators was used to enhance the phase information with enhanced fidelity by cascaded four wave mixing to multiply the modulation depth of a phase-only optical signal.
Abstract: We utilise cascaded four wave mixing to multiply the modulation depth of a phase-only optical signal and generate a comb of phase locked local oscillators allowing homodyne retrieval of the phase information with enhanced fidelity.
TL;DR: In this article, a small-core high-nonlinearity non-silica Pb-HF with unique dispersive properties for compact nonlinear optics devices operating at low powers is presented.
Abstract: Holey Fibers (HFs) have generated enormous interest from areas as diverse as spectroscopy, metrology, biomedicine, imaging, telecommunication, industrial machining and the military. Recently, HFs made from compound glasses with high nonlinear refractive indices have attracted much attention for nonlinear device applications. In this study we used Lead-silicate (Pb) glass, which has proven to be a promising material for high nonlinearity HFs. Pb glasses offer high thermal and crystallization stability and less steep viscosity-temperature-curves with low softening temperatures, which allow the use of extrusion as an alternative fiber preform fabrication technology. Pb-HFs has a high material nonlinear refractive index and the index between the glass core and the air filled cladding enables tight mode confinement which results in a low effective area and thereby a high nonlinear coefficient. In addition, Pb has large normal material dispersion and bulk glass zero dispersion (ZD) wavelength at 1970nm, the tailorability of the cladding structure enables high flexibility in the design of the dispersion profile facilitating nonlinear effects, especially by the choice of ZD wavelengths at near IR region. This paper presents the development of small-core high-nonlinearity non-silica HFs with unique dispersive properties for compact nonlinear optics devices operating at low powers. To date, we managed to produce low-loss (2dB/m at 1550nm and ~1.5dB/m at 1060nm) Pb-HFs with very high nonlinearity coefficient up to ~2000W. A dispersion model simulated using finite element method has demonstrated that Pb glass HFs with core size of 1.7µm are anticipated to enable ZD at 1060nm and with very high nonlinearities, which should allow efficient supercontinuum generation in compact devices using commonly available femto-second lasers as the pump sources. These results show that Pb-HFs are indeed promising components that contribute to the significant advancement in the miniaturization of compact nonlinear devices operating at low powers and offering appropriate dispersion.
20 Nov 2012
TL;DR: In this paper, the authors present results from high performance silicon optical modulators produced within the two largest silicon photonics projects in Europe; UK Silicon Photonics (UKSP) and HELIOS.
Abstract: In this work we present results from high performance silicon optical modulators produced within the two largest silicon
photonics projects in Europe; UK Silicon Photonics (UKSP) and HELIOS. Two conventional MZI based optical
modulators featuring novel self-aligned fabrication processes are presented. The first is based in 400nm overlayer SOI
and demonstrates 40Gbit/s modulation with the same extinction ratio for both TE and TM polarisations, which relaxes
coupling requirements to the device. The second design is based in 220nm SOI and demonstrates 40Gbits/s modulation
with a 10dB extinction ratio as well modulation at 50Gbit/s for the first time. A ring resonator based optical modulator,
featuring FIB error correction is presented. 40Gbit/s, 32fJ/bit operation is also shown from this device which has a 6um
radius. Further to this slow light enhancement of the modulation effect is demonstrated through the use of both
convention photonic crystal structures and corrugated waveguides. Fabricated conventional photonic crystal modulators
have shown an enhancement factor of 8 over the fast light case. The corrugated waveguide device shows modulation
efficiency down to 0.45V.cm compared to 2.2V.cm in the fast light case. 40Gbit/s modulation is demonstrated with a
3dB modulation depth from this device. Novel photonic crystal based cavity modulators are also demonstrated which
offer the potential for low fibre to fibre loss. In this case preliminary modulation results at 1Gbit/s are demonstrated.
Ge/SiGe Stark effect devices operating at 1300nm are presented. Finally an integrated transmitter featuring a III-V
source and MZI modulator operating at 10Gbit/s is presented.