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We propose and experimentally demonstrate a photonic integrated circuit (PIC) that operates as an optical equalizer (OE) with multi-rate and multi-channel capability. The OE has the structure of a 3-tap direct form finite impulse response (FIR) filter and is based on the use of micro-ring resonators (MRRs) for the tuning of its delay lines. The PIC is fabricated on TriPleX platform and has 17 reconfigurable elements in total including nine MRRs, five optical couplers and three standalone phase shifters. Using this OE in an on-off keying system with bandwidth limitations we achieve an eye-diagram opening improvement more than 14 dB working with signals at 4.67 and 5.84 Gbaud both in single- and dual-channel operation. Extension to higher modulation formats is direct. Extension to higher symbol rates is also possible via the use of smaller MRRs.

International audience; In this paper, we address the experimental implementation of an all-optical packet routing scheme, with contention resolution capability, using interconnected semiconductor optical amplifier (SOA)-based Mach- Zehnder interferometer (SOA-MZI) structures. Cross talk stemming from the blocked packets, due to the nonideal switching performed by the SOA-MZIs, is analyzed in every stage of the routing configuration. The routing functions and states performance are evaluated through bit-error ratio measurements and extinction ratio analysis.

International audience; We introduce a novel design of an all-optical packet routing node that allows for the selection and forwarding of optical packets based on the routing information contained in hybrid wavelength division multiplexing/optical code division multiple access (WDM/OCDMA) labels. A stripping paradigm of optical code-label is adopted. The router is built around an optical-code gate that consists in an optical flip–flop controlled by two fiber Bragg grating correlators and is combined with a Mach–Zehnder interferometer (MZI)-based forwarding gate. We experimentally verify the proof-of-principle operation of the proposed self-routing node under NRZ and OCDMA packet traffic conditions. The successful switching of elastic NRZ payload at 40 Gb/s controlled by DS-OCDMA coded labels and the forwarding operation of encoded data using EQC codes are presented. Proper auto-correlation functions are obtained with higher than 8.1 dB contrast ratio, suitable to efficiently trigger the latching device with a contrast ratio of 11.6 dB and switching times below 3.8 ns. Error-free operation is achieved with 1.5 dB penalty for 40 Gb/s NRZ data and with 2.1 dB penalty for DS-OCDMA packets. The scheme can further be applied to large-scale optical packet switching networks by exploiting efficient optical coders allocated at different WDM channels.

International audience; we propose and demonstrate experimentally an allopticalpacket routing scheme using hybrid wavelength divisionmultiplexing/optical code division multiple access labeling for 40Gb/s NRZ data. With no electronic control, the system forwardsasynchronously packets delimited by valid label and suppressesunwanted traffic. It consists in an optical flip-flop controlled bytwo correlators combined with a Mach-Zehnder interferometerthat selects packets for each fiber output. The experimentalresults show optical switching operation for the optical-code gatewith an extinction ratio of 16 dB between the switched andun-switched packets in a switching time below 2 ns. Error-freeoperation has been successfully achieved with low power penaltyfor 40 Gb/s NRZ data.

234 σ., Η ανάπτυξη αμιγώς οπτικών διατάξεων επεξεργασίας σήματος αποτελεί σταθερή ερευνητική επιδίωξη με στόχο την επέκταση της διαφάνειας των οπτικών δικτύων και την πλήρη αξιοποίηση του εύρους ζώνης που παρέχει η οπτική ίνα ως φυσικό μέσο μετάδοσης. Για την υλοποίηση αυτού του είδους των διατάξεων, η αξιοποίηση των μη γραμμικών ινών και γενικότερα των μη γραμμικών μέσων Kerr, αποτελεί βασική επιλογή καθώς διαθέτουν τη δυνατότητα λειτουργίας σε υπερυψηλούς ρυθμούς μετάδοσης λόγω της φύσης του φαινομένου Kerr και της πρακτικά ακαριαίας απόκρισης της αντίστοιχης μη γραμμικότητας. Μέσα σε αυτό το πλαίσιο, η διατριβή εστιάζει στη μελέτη, ανάπτυξη και πειραματική αξιολόγηση πρωτότυπων διατάξεων μη γραμμικών ινών για την οπτική επεξεργασία σήματος, οι οποίες διακρίνονται για τη σύνθετη λειτουργικότητα και τη συμβατότητά τους με καινούργια σχήματα κωδικοποίησης και επιβεβαιώνουν ανεπιβεβαίωτα ως σήμερα εν πολλοίς χαρακτηριστικά των μη γραμμικών ινών, όπως η δυνατότητα πολυκυματικής λειτουργίας και ταυτόχρονης επεξεργασίας πολλαπλών καναλιών WDM. Υπό αυτήν την έννοια, η παρούσα διατριβή αντιπροσωπεύει μία ολοκληρωμένη και καλά ορισμένη ερευνητική προσπάθεια, συμπληρωματική ως προς την πλειονότητα των αντίστοιχων ερευνητικών προσπαθειών κατά την τελευταία δεκαετία, οι οποίες εστίασαν στην υλοποίηση απλούστερων τεχνικών σε διαρκώς υψηλότερους ρυθμούς μετάδοσης ή με τη χρήση ολοκληρώσιμων μη γραμμικών μέσων Kerr. Στα πλαίσια της διατριβής μελετήθηκαν και υλοποιήθηκαν τέσσερα συγκεκριμένα οπτικά κυκλώματα, τα οποία περιλαμβάνουν κύκλωμα πολυκυματικής αναγέννησης καναλιών WDM, κύκλωμα ανάκτησης ρολογιού από σύγχρονα ή ασύγχρονα οπτικά πακέτα μικρού μήκους, κύκλωμα αναγέννησης οπτικών σημάτων DPSK και κύκλωμα ανάδρασης για τον πολλαπλασιασμό ρυθμοδότησης ψευδοτυχαίων δυαδικών ακολουθιών (ΨΔΑ). Το κύκλωμα πολυκυματικής αναγέννησης βασίζεται στην υλοποίηση κατάλληλα σχεδιασμένου χάρτη διασποράς με χρήση συμβατικών ινών μετάδοσης και ινών αναίρεσης διασποράς, ο οποίος μειώνει τη μη γραμμική αλληλεπίδραση των καναλιών WDM επιτρέποντας την ταυτόχρονη αναγέννησή τους με τη βοήθεια του φαινομένου της αυτοδιαμόρφωσης φάσης. Το κύκλωμα ανάκτησης ρολογιού βασίζει τη λειτουργία του στη χρήση φίλτρου Fabry-Perot και περιοριστή οπτικής ισχύος μη γραμμικής ίνας. Ο περιοριστής οπτικής ισχύος δέχεται την έξοδο του φίλτρου Fabry-Perot, καταπιέζει δραστικά τη διακύμανση πλάτους που αυτή παρουσιάζει, και αποδίδει κατά αυτόν τον τρόπο ανακτημένο σήμα ρολογιού υψηλής ποιότητας. Το κύκλωμα αναγέννησης οπτικών σημάτων DPSK βασίζει τη λειτουργία του στην αποκωδικοποίηση των εισερχόμενων σημάτων και την εκ νέου διαμόρφωση κατά φάση ενός καινούργιου φέροντος με τη βοήθεια συμβολόμετρου Sagnac μη γραμμικής ίνας. Η συγκεκριμένη διαδικασία εκμεταλλεύεται τη μη γραμμικότητα του συμβολόμετρου Sagnac, έτσι ώστε να καταπιέσει το θόρυβο φάσης και πλάτους των εισερχόμενων σημάτων και να εξασφαλίσει την αναγέννησή τους. Τέλος, το οπτικό κύκλωμα ανάδρασης χρησιμοποιεί τη συγκεκριμένη τοπολογία ανάδρασης, καθώς και την οπτική υλοποίηση πύλης OR με χρήση συμβολόμετρου Sagnac μη γραμμικής ίνας, και επιτυγχάνει τον πολλαπλασιασμό ρυθμοδότησης ΨΔΑ με μεγαλύτερη ευελιξία, ευνοϊκότερους κανόνες κλιμάκωσης και υψηλότερη ποιότητα λειτουργίας σε σύγκριση με τις αντίστοιχες συμβατικές (γραμμικές) διατάξεις πολλαπλασιασμού ρυθμοδότησης. Και τα τέσσερα κυκλώματα επιδείχθηκαν πειραματικά στην περιοχή ρυθμών μετάδοσης των 40 Gb/s, αλλά η δυνατότητα επέκτασης της λειτουργίας τους σε υψηλότερες ταχύτητες είναι δεδομένη. Η πρακτική εφαρμογή τους αφορά οπτικά δίκτυα επικοινωνιών πρώτης, δεύτερης και τρίτης γενιάς, καθώς και συστήματα μετρήσεων και ελέγχου λειτουργίας άλλων οπτικών στοιχείων, διατάξεων, υποσυστημάτων και συστημάτων.The development of all-optical signal processing techniques and circuits has attracted particular interest over the last decades, aiming at the enhancement of optical networks transparency and the exploitation of the huge bandwidth, being made available by the optical fiber as a transmission line. One of the most preferable options for the implementation of this type of circuits is the use of nonlinear fibers, and in general of nonlinear Kerr media, mainly due to their potential for high-speed operation that originates from the nature of the Kerr effect itself and the practically instantaneous response of the Kerr nonlinearity. Within this framework, the thesis focuses on the study, development and experimental demonstration of novel, nonlinear fiber-based, all-optical signal processing subsystems that exhibit a high-degree of network functionality and compatibility with novel modulation formats, and additionally verify further characteristics of the fiber-based processors, such as their capability of multi-wavelength operation and thus, of simultaneous processing multiple WDM channels. In this sense, the present doctoral thesis represents a complete and well-defined research effort, complementary to other efforts over the last decade that have been aiming at implementing simpler concepts at increasingly high data rates and with the use of advanced Kerr media and integrated circuits. Within the framework of the thesis, four particular circuits were studied and experimentally demonstrated for the first time. These include a multi-wavelength regeneration circuit for on-off keying (OOK) signals, a clock recovery circuit for ultra-short, synchronous or asynchronous optical packets, a circuit for regeneration of optical differential phase-shift keying (DPSK) signals and a feedback circuit for rate multiplication of pseudo-random binary sequences (PRBS). The multi-wavelength regeneration circuit is based on the implementation of a carefully designed dispersion map that allows for the elimination of the nonlinear interaction between the WDM channels and for their simultaneous regeneration by means of the self-phase modulation effect. The clock recovery circuit is based, in turn, on the use of a Fabry-Perot filter (FPF) and a subsequent optical power limiter, which drastically suppresses the intense amplitude modulation of the FPF output and delivers the high-quality signal of the recovered clock. The DPSK regenerator relies on the decoding of the input data streams and the phase re-modulation of a new optical carrier using a nonlinear fiber-based Sagnac interferometer. The concept exploits the nonlinear transfer function of the Sagnac gate and offers the possibility for suppressing both the phase- and the amplitude-noise of the input signals, thus resulting in their regeneration. Finally, the all-optical feedback circuit exploits the feedback topology and the functionality of an optical OR gate to achieve the data rate multiplication of PRBS with higher flexibility, favorable scaling laws and higher operation quality as compared to the conventional, linear techniques. The optical implementation of the OR gate relies again on the nonlinear fiber-based Sagnac interferometer. All four circuits were experimentally demonstrated at 40 Gb/s data rate range, but the capability of extending their operation at higher data rates is given. Their practical significance refers to their potential for deployment in first-, second- and third-generation optical communication networks, as well as in test & measurement systems for the performance evaluation of a variety of optical elements, circuits, subsystems and systems., The development of all-optical signal processing techniques and circuits has attracted particular interest over the last decades, aiming at the enhancement of optical networks transparency and the exploitation of the huge bandwidth, being made available by the optical fiber as a transmission line. One of the most preferable options for the implementation of this type of circuits is the use of nonlinear fibers, and in general of nonlinear Kerr media, mainly due to their potential for high-speed operation that originates from the nature of the Kerr effect itself and the practically instantaneous response of the Kerr nonlinearity. Within this framework, the thesis focuses on the study, development and experimental demonstration of novel, nonlinear fiber-based, all-optical signal processing subsystems that exhibit a high-degree of network functionality and compatibility with novel modulation formats, and additionally verify further characteristics of the fiber-based processors, such as their capability of multi-wavelength operation and thus, of simultaneous processing multiple WDM channels. In this sense, the present doctoral thesis represents a complete and well-defined research effort, complementary to other efforts over the last decade that have been aiming at implementing simpler concepts at increasingly high data rates and with the use of advanced Kerr media and integrated circuits. Within the framework of the thesis, four particular circuits were studied and experimentally demonstrated for the first time. These include a multi-wavelength regeneration circuit for on-off keying (OOK) signals, a clock recovery circuit for ultra-short, synchronous or asynchronous optical packets, a circuit for regeneration of optical differential phase-shift keying (DPSK) signals and a feedback circuit for rate multiplication of pseudo-random binary sequences (PRBS). The multi-wavelength regeneration circuit is based on the implementation of a carefully designed dispersion map that allows for the elimination of the nonlinear interaction between the WDM channels and for their simultaneous regeneration by means of the self-phase modulation effect. The clock recovery circuit is based, in turn, on the use of a Fabry-Perot filter (FPF) and a subsequent optical power limiter, which drastically suppresses the intense amplitude modulation of the FPF output and delivers the high-quality signal of the recovered clock. The DPSK regenerator relies on the decoding of the input data streams and the phase re-modulation of a new optical carrier using a nonlinear fiber-based Sagnac interferometer. The concept exploits the nonlinear transfer function of the Sagnac gate and offers the possibility for suppressing both the phase- and the amplitude-noise of the input signals, thus resulting in their regeneration. Finally, the all-optical feedback circuit exploits the feedback topology and the functionality of an optical OR gate to achieve the data rate multiplication of PRBS with higher flexibility, favorable scaling laws and higher operation quality as compared to the conventional, linear techniques. The optical implementation of the OR gate relies again on the nonlinear fiber-based Sagnac interferometer. All four circuits were experimentally demonstrated at 40 Gb/s data rate range, but the capability of extending their operation at higher data rates is given. Their practical significance refers to their potential for deployment in first-, second- and third-generation optical communication networks, as well as in test & measurement systems for the performance evaluation of a variety of optical elements, circuits, subsystems and systems., Χρήστος Β. Κουλουμέντας

The EHEA (EEES in Spain) is creating common academic degree standards comparable and compatible between the European countries. The definition of the new Credit unit, the ECTS, focused on the hours of study devoted by the students, is also promoting the renovation of the educational process at the higher studies of Graduate Degree and Master. We describe the experience of innovation of the teaching practice of the “Fibres & Telecommunications” subject of the Master PhotonicsBCN (part of the Erasmus Mundus Master EUROPHOTONICS), by introducing team9 working techniques for promoting: the development of cooperative learning, interpersonal skills, and positive interdependence among the students, not forgetting the individual initiative and responsibility. The teamwork is oriented to small innovation projects (inspired in state9of9the9art research challenges faced by the European FP7 EURO9FOS Network9 of 9Excellence) promoting interactive and dynamic student learning process. Each team member is spontaneously encouraged to learn as much as possible on both: the area of his task inside the common project, and also the influence of his task in the over all results of the project. This is implemented by the use of commercial software for professional systems deployment (VPIphotonics TM ), which allows each team to check the real viability of their innovative solution