Showing papers by "Periklis Petropoulos published in 2009"

Phase sensitive amplification based on quadratic cascading in a periodically poled lithium niobate waveguide.

Abstract: We propose and demonstrate phase-sensitive amplification based on cascaded second harmonic generation and difference frequency generation within a periodically poled lithium niobate waveguide. Excellent agreement between our numerical simulations and proof-of-principle experiments using a 3-cm waveguide device operating at wavelengths around 1550 nm is obtained. Our experiments confirm the validity and practicality of the approach and illustrate the broad gain bandwidths achievable. Additional simulation results show that the maximum gain/attenuation factor increases quadratically with input pump power, reaching a value of ± 19.0dB at input pump powers of 33 dBm for a 3 cm-long waveguide. Increased gains/reduced powers for a fixed gain could be achieved using longer crystals.

Dispersion-shifted all-solid high index-contrast microstructured optical fiber for nonlinear applications at 1.55µm

Abstract: We report the fabrication of an all-solid highly nonlinear microstructured optical fiber. The structured preform was made by glass extrusion using two types of commercial lead silicate glasses that provide high index-contrast. Effectively single-moded guidance was observed in the fiber at 1.55µm. The effective nonlinearity and the propagation loss at this wavelength were measured to be 120W/km respectively at 1.55µm. These predictions are consistent with the experimentally determined dispersion of +12.5ps/nm/km at 1.55µm. Tunable and efficient four-wave-mixing based wavelength conversion was demonstrated at wavelengths around 1.55µm using a 1.5m length of the fiber.

Efficient All-Optical Wavelength-Conversion Scheme Based on a Saw-Tooth Pulse Shaper

Abstract: We experimentally demonstrate the use of saw-tooth optical pulses, generated using a superstructured fiber Bragg grating, to achieve high performance and efficient all-optical wavelength conversion in a scheme based on cross-phase modulation in a highly nonlinear fiber, with subsequent offset filtering. Compared to the use of more conventional waveforms, such as Gaussian pulses, the purpose-shaped saw-tooth pulses allow an improvement in the optical signal-to-noise ratio of the wavelength-converted signal of around 15 dB as well as a more than 6-dB improvement in receiver sensitivity.

Time domain add–drop multiplexing scheme enhanced using a saw-tooth pulse shaper

Abstract: We experimentally demonstrate the use of saw-tooth optical pulses, which are shaped using a fiber Bragg grating, to achieve robust and high performance time-domain add-drop multiplexing in a scheme based on cross-phase (XPM) modulation in an optical fiber, with subsequent offset filtering. As compared to the use of more conventional pulse shapes, such as Gaussian pulses of a similar pulse width, the purpose-shaped saw-tooth pulses allow higher extinction ratios for the add and drop windows and significant improvements in the receiver sensitivity for the dropped and added channels.

Experimental comparison of gain and saturation characteristics of a parametric amplifier in phase-sensitive and phase-insensitive mode

Abstract: We demonstrate a parametric amplifier with precise control of the in-going waves and study gain and saturation properties in both PSA and PIA mode. A PSA gain of 33 dB is achieved.

An optical frequency comb generator as a broadband pulse source

Abstract: We demonstrate the generation of wavelength tunable, 0.62 ps, near transform-limited pulses at a repetition rate of 20 GHz by combining an ultra-stable optical frequency comb generator with a delay line interferometer.

All-Optical 160-Gbit/s Retiming System Using Fiber Grating Based Pulse Shaping Technology

Abstract: This paper demonstrates a retiming system operating at rates of 40 and 160 Gbit/s, which incorporates a superstructured fiber Bragg grating (SSFBG) as a pulse shaping element. The original data pulses are shaped into flat-topped (rectangular) pulses to avoid conversion of their timing jitter into pulse amplitude noise at the output of a nonlinear fiber-based Kerr switch. Thus retiming is performed in a single step avoiding wavelength conversion. The benefits of using shaped rather than conventional pulse forms in terms of timing jitter reduction are confirmed by bit-error rate (BER) measurements.

Optical grooming switch with regenerative functionality for transparent interconnection of networks

Abstract: We demonstrate a regenerative optical grooming switch for buffer-less interconnection of metro/access and metro/core ring networks with switching functionality in time, space and wavelength domain Key functionalities of the router are the traffic aggregation with time-slot interchanging (TSI) functionality, the WDM-to-ODTM multiplexing and the OTDM-to-WDM demultiplexing of high-speed channel into lower bit-rate tributaries as well as multi-wavelength all-optical 2R regeneration of several higher-speed signals BER and Q-factor measurements of different switching scenarios show excellent performance with no error floor and Q-factors above 21 dB

2R regeneration of two 130 Gbit/s channels within a single fiber

Abstract: We experimentally demonstrate the simultaneous all-optical regeneration of two 130Gbit/s signals in a single highly nonlinear fibre using self-phase modulation and offset filtering. No degradation was observed due to the presence of the second channel.

Field trial of WDM-OTDM transmultiplexing employing photonic switch fabric-based buffer-less bit-interleaved data grooming and all-optical regeneration

Abstract: We report, for the first time, a field trial of a novel 42.7Gbps/128.1Gbps WDM/OTDM grooming node, and confirm node interoperability and the data integrity of asynchronous retiming.

Optical WDM regeneration: Status and future prospects

Abstract: Principles of 2R all-optical regeneration in the context of multi-channel operation are presented. Existing fiber-based solutions are reviewed both in terms of implementation issues and performance.

Four-wave mixing-based wavelength conversion in a short-length of a solid 1D microstructured fibre

Abstract: We demonstrate a four-wave mixing based wavelength conversion scheme at 1.55µm in a 1.5m long highly nonlinear, dispersion tailored one-dimensional (1D) soft glass microstructured optical fibre.

Highly nonlinear non-silica glass microstructured optical fibers with near-zero dispersion and dispersion slope for 1.55µm applications

Abstract: Microstructured optical fiber (MOF) technology has generated several new opportunities for the implementation of optical fibers with novel properties and functions [1]. The novel optical properties of MOFs arise from the combination of wavelength-scale features in the fiber cross-section with the large index-contrast of the materials comprising the microstructured cladding. Due to the higher linear (n) and nonlinear refractive index (n 2 ) of non-silica glasses as compared to silica, it has been demonstrated that the effective nonlinearity (γ) of a non-silica glass MOF can be between 2−4 orders of magnitudes higher than that of the conventional silica fiber (g∼1W−1km−1), thus enabling the realisation of compact nonlinear devices operating at practical power levels. However, for such applications as wavelength-conversion, optical parametric amplification, supercontinuum generation etc, apart from a high γ value, it is equally desirable that the nonlinear fiber also exhibits near-zero dispersion and dispersion slope at the operating wavelengths. We report here our recent advances on the fabrication of single-mode highly nonlinear lead-silicate MOFs with low dispersion and dispersion slope values at 1.55 µm.

Applications of superstructured fibre Bragg gratings in all-optical signal processing

Abstract: We review our recent progress in the area of reshaping of short optical pulses in both time and frequency domain produced using superstructured fibre Bragg gratings (SSFBGs). We mainly focus our discussion on the saw-tooth pulse shape as an interesting example of the powerful combination of nonlinear optical switches and tailored optical pulses.

Optical Signal Processing Techniques for Signal Regeneration and Digital Logic

Abstract: This chapter presents recent developments in optical signal processing techniques and digital logic. The first section focuses on techniques to obtain key functionalities as signal regeneration and wavelength conversion exploiting nonlinear effects in high nonlinear fibres and semiconductor optical amplifiers. The second section covers techniques for clock recovery and retiming at high-speed transmission up to 320 Gb/s. In addition a technique to obtain OTDM demultiplexing based on cross-phase modulation is reported.

Nonlinear optical thresholding in a 4-channel OCDMA system via Two-Photon Absorption

Abstract: We demonstrate the use of a Two-Photon Absorption based detector in an OCDMA system. This detector provides a significant performance improvement over standard linear detection.

Multi-wavelength all-optical regeneration techniques

Abstract: We review the progress on the various existing fibre-based solutions proposed to date to extend all-optical 2R regeneration to multi-channel operation. Our emphasis is on a bi-directional architecture based on offset filtering of an SPM-broadened spectrum.

An all-optical grooming switch with regenerative capabilities

Abstract: A regenerative optical grooming switch for interconnecting 130 Gbit/s and 40 Gbit/s networks with switching functionality in time, space and wavelength domain is demonstrated. Lab and field demonstrations show the feasibility of the new concept developed by the TRIUMPH project consortia. Q-factors above 20 dB are reported.

Simultaneous 2R regeneration of WDM signals in a single optical fibre

Abstract: Two experimental implementations of amplitude regeneration of WDM signals based on self-phase modulation (SPM) in optical fibres are discussed. The two examples differ in their approach of mitigation of inter-channel nonlinearities.

A solid one-dimensional microstructured optical fiber with high nonlinearity and low dispersion at 1.55μm

Abstract: We report on the fabrication of a solid one-dimensional microstructured fiber with high nonlinearity and low dispersion at 1.55μm. A four-wave-mixing based tunable wavelength-conversion scheme was experimentally demonstrated in just 1.5m of this fiber.

Efficient all-optical wavelength converter using saw-tooth pulses

Abstract: Wavelength conversion is a key WDM function which is used to avoid wavelength blocking, thus allowing greater flexibility in the network design. Wavelength conversion of an intensity modulated signal can be simply achieved by employing cross-phase modulation (XPM) on a CW beam placed at the desired wavelength, normally followed by a band-pass filter and a narrowband notch filter to reject the pump and the carrier frequency respectively. The notch filter in particular has to be precisely tuned to the CW wavelength and be extremely narrowband in order to avoid any distortions on the spectral envelope of the converted signal (see e.g. [1]). This extra complexity could be avoided using conventional band-pass filters only to select a single sub-carrier band, but this usually implies non optimal CW extinction and thus some extra power penalties as compared to the original signal. In this paper we investigate the use of pulse shaping of the signal to be converted into a saw-tooth waveform (i.e. a pulse with leading/trailing edges of a constant intensity gradient), to improve the performance of the converted signal. Due to their linear gradient, when saw-tooth pulses are used as the XPM pump, they induce a constant frequency shift to the signal [2, 3]. These new frequency components are highly spectrally confined and discretely separated from the CW carrier, thus allowing most of the wavelength converted signal energy to pass through the subsequent offset filters, thereby improving the overall optical signal to noise ratio (OSNR) and the overall system performance. Similarly, self-phase modulation (SPM) of saw-tooth pulses is more confined, giving more flexibility on the choice of the pump and signal wavelength allocations.

Complete temporal optical Fourier transformations using dark parabolic pulses

Abstract: A study of the dynamics of temporal optical Fourier transforms is presented in the interest of improving transform quality. Experimental verification of how a complete Fourier transform can be obtained in both domains is demonstrated.

Record-Length 10.7 Gb/s uncompensated transmission experiment over installed fiber using narrow-filtered duobinary and a correlation-sensitive MLSE-Rx

Abstract: We carried out an off-line 10.7 Gb/s transmission experiment over installed fiber, using narrow-filtered duobinary and a noise-correlation-sensitive MLSE receiver. We achieved MLSE-systems record distance (1300 km, 2048 states) and record efficiency (800 km, 64 states).

High performance optical processing systems incorporating grating based pulse shaping

Abstract: We review the operating principles and performance of optical pulse processing systems which exploit the powerful combination of Kerr-nonlinearity based optical switches and tailored optical pulses (e.g. square, triangular and parabolic) produced using superstructured fiber Bragg gratings.

Advanced fibre grating technologies for application in next generation lasers and networks

Abstract: We review the operating principles and performance of optical pulse processing systems exploiting the powerful combination of Kerr-nonlinearity based optical switches and tailored optical pulses (e.g. square, parabolic and saw-tooth) produced using superstructured fibre Bragg gratings.