This thesis investigates the security of optical fiber communication and demonstrates the feasibility of eavesdropping using different tapping methods and superconducting nanowire single-photon detectors (SNSPDs). Methods for surveillance against fiber intrusion are also investigated. The setups were built from mainly commercially available components and a 3D-printed sculpture and data analysis was done using open-source software. By the use of a clip-on coupler, classical systems were tapped. Transmission loss and tapping efficiency was measured to 42% and 1.5% respectively. Continuous system monitoring for tap detection using an SNSPD was performed showing that photon backscattering increased by a factor of 6 when the tap was applied. A qualitative investigation on tapping light via fiber bending was performed with signal loss/coupling efficiency registered with regards to bending diameter. Loss in a light conducting fiber and detection events in the tapping fiber increased with decreasing bend diameter. It is also shown that keeping a constant bend diameter while increasing the number of turns of the tapping fiber can increase amount of tapped light while keeping signal loss constant. Lastly, optical routers were tapped, the tapped light was analysed through a spectrum analyser yielding the lights wavelength and signal-to-noise ratio. The tapped light was then connected to a SNSPD and photon detection events was registered. / Denna avhandling undersöker säkerheten för optisk fiberkommunikation inom telekomområdet och genomförbarheten av avlyssing med olika avlyssningsmetoder samt superconducting nanowire single-photon detectors (SNSPDer). Även metoder för att övervaka mot avlyssing undeersöks. Utrustningarna byggdes med kommersiellt tillgängliga komponenter och en 3D-utskriven skulptur och dataanalysen utfördes med hjälp av öppen källkodsprogramvara. Genom användning av en Clip-On-Coupler avlyssnades klassiska system. Överföringsförlusten och avlyssningseffektiviteten mättes till 42% respektive 1,5%. Kontinuerlig systemövervakning för att upptäcka avlyssning med hjälp av en SNSPD utfördes och visade att antalet bakreflekterade fotoner ökade med en faktor på 6 när avlyssningen applicerades. En kvalitativ undersökning av att avlyssna ljus genom att böja fiber utfördes, där signalförlust och kopplingseffektivitet registrerades med avseende på böjningsdiameter. Förlusten i en ljusledande fiber och fotonförekomst i avlyssningsfibern ökade med minskande böjningsdiameter. Det visas också att genom att behålla en konstant böjningsdiameter samtidigt som antalet varv på avlyssningsfibern ökas kan mängden avlyssnat ljus öka samtidigt som signalförlusten hålls konstant. Slutligen avlyssnades optiska routrar, det avlyssnade ljuset analyserades med hjälp av en spektrumanalysator som utvann ljusets våglängd och signal-brusförhållande. Det avlyssnade ljuset kopplades sedan till en SNSPD och fotonförekomst registrerades.

Fiber-optic Bragg grating (FBG) sensors are a very attractive technology for the measurement of strain and temperature. They have many advantages over conventional sensors in sensing applications such as sensitivity, immunity to electromagnetic interferences,large bandwidths,capability of remote operation and the potential power to sense micro strain at high temperature. They can be directly embedded into many structures such as concrete to evaluate the material deformation. FBGs are fabricated by photo-inscribing through a phase mask technology on a photosensitive fiber. A periodic refractive index is formed in the fiber core, introducing a reflection at the Bragg wavelength. Since the FBG is characterized by a low insertion loss and controllable reflectance, it has the potential to be multiplexed in very large numbers. The major purpose of this dissertation research is to develop an innovative, high- resolution fiber Bragg grating sensing system using photon-counting optical time domain reflectometry (pc-OTDR) based multiplexing technology. The system uses a Fresnel reflection OTDR with a zero deadzone to detect FBG sensors, which improves both the system detection ability and spatial resolution. A low reflectance FBG with broad bandwidth has been developed that is appropriate for the pc-OTDR measurement. Hundred of multiplexed sensors have been implemented in this system. Two theoretical analyses and preliminary results are presented. The greatest advantage of the system is to increase the maximum multiplexing sensor number to one thousand within a short fiber range. Self-referencing demodulation is necessary to eliminate multiplexed system noise caused by the source power fluctuation and fiber bending effects. A referencing FBG with a different wavelength from the sensing FBG has to be introduced to achieve compensation of disturbances in the measurement. The spectral properties of the FBGs and the combination of WDM/TDM are also discussed to evaluate multiplexing sensor performance. The sensor crosstalk and other noise performances are assessed to evaluate the possibility of large scale multiplexing. / Ph. D.

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Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-03-07T15:50:18Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseInfluenciaMonitoramento.pdf: 1998332 bytes, checksum: 3137599690b5b1f015ab9ab0c585c5ad (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-05-13T17:13:08Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseInfluenciaMonitoramento.pdf: 1998332 bytes, checksum: 3137599690b5b1f015ab9ab0c585c5ad (MD5) / Made available in DSpace on 2014-05-13T17:13:08Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseInfluenciaMonitoramento.pdf: 1998332 bytes, checksum: 3137599690b5b1f015ab9ab0c585c5ad (MD5) Previous issue date: 2013 / Redes Ópticas Passivas estão cada vez mais difundidas como rede de acesso de banda larga. Devido à sua importância, tais redes necessitam constantemente de supervisão. Diversas técnicas vêm sendo empregadas para supervisão de redes ópticas, dentre as quais se destacam as que utilizam reflectometria, pois agregam vantagens, tais como: baixo custo, em comparação com outros métodos de supervisão, e não exigência de intervenção na casa do usuário. Esta dissertação apresenta uma estratégia capaz de quantificar, por meio de simulações, o impacto que a técnica de reflectometria no domínio do tempo gera como interferência em transmissões típicas de uma rede WDM-PON. / Passive Optical Networks are increasingly diffused as a broadband access technology. Due to their importance, such networks demands continue supervision scheme. Different techniques could be employed for Optical Network Supervision, among them those using reflectometry have highlighted, because it offer low cost when compared with other monitoring methods and do not require intervention in the user’s home. On the other hand, when doing monitoring, it is expected that this action does not influence the information signal transmitted to the subscriber. In this context, this work aims to quantify, through simulations, how the technique of time domain optical reflectometry interferes on the transmission of a WDM-PON network.

Η χρήση των οπτικών ινών στην κατασκευή μητροπολιτικών δικτύων είναι βασικός παράγοντας για την ποιότητα των υπηρεσιών που προσφέρονται στους τελικούς χρήστες, αφού οι οπτικές ίνες είναι η μόνη μακροπρόθεσμη λύση που μπορεί να παρέχει το απαιτούμενο εύρος ζώνης για πολυμεσικές και αλληλεπιδραστικές εφαρμογές σε παγκόσμιο και διεθνές επίπεδο. Η διπλωματική εργασία αυτή απευθύνεται σε άτομα που κατέχουν βασικές γνώσεις πάνω στην τεχνολογία επικοινωνιών και θέλουν να πληροφορηθούν περαιτέρω πάνω σε ζητήματα οπτικής ενίσχυσης σήματος και χρήσης νέων τεχνολογικών μέσων για τον χαρακτηρισμό και την πιστοποίηση long-haul ζεύξεων SMF οπτικών ινών. Στην διπλωματική αυτή αναλύονται θέματα όπως τα είδη εξασθένησης που συναντούμε στις μονότροπες οπτικές ίνες, η χρησιμότητα και η λειτουργικότητα της συσκευής OTDR (Optical time-domain reflectometer) στον χαρακτηρισμό δικτύων οπτικών ινών μεγάλου μήκους, όπως και η δυνατότητα οπτικής ενίσχυσης Raman, μιας μεθόδου με πολλά συγκριτικά πλεονεκτήματα σε σχέση με τις παρούσες τεχνολογίες ενίσχυσης οπτικού σήματος με ενισχυτές ίνας ερβίου. / -

This master’s thesis is focused on sensory systems and analysis of such signals. In the frst part, a theoretical analysis of each sensory system is conducted. Followingly, appropriate flters were used to process these signals. The last part of this thesis deals with the analysis of measured data.

This master’s thesis is focused on sensory systems and analysis of such signals. In the frst part, a theoretical analysis of each sensory system is conducted. Followingly, appropriate flters were used to process these signals. The last part of this thesis deals with the analysis of measured data.

The financial requirements between fiber optic sensors and conventional sensors are gradually declining, which, despite many advatages and wide range of applicationas, has slowed down the demand for these sensors. With the demand for fiber optic sensors also grow the requirements for the parameters of these sensors. This thesis deals with distributed temperature fiber optic sensors. Non--linear phenomen in optical fibers, such as Raman scattering is used for measuring with these sensors. This scatterin was used to obtain information about temperature, which effected the optical cable under the test.

The aim of this thesis was to ascertain with the measurement methods of passive optical networks and the creation of a simulation model that corresponds to the measured network and comparison of results. The first chapter deals with Triple Play services, which are focused on different services (transmission of television signals, voice and data transmission). Each service consists of a subchapter and presents a detailed description of the parameters associated with the transmission. The second chapter of the theoretical part consists of an analysis of passive optical networks according to termination method of FTTx optical fiber. Partial part of this chapter consists of description of standard passive optical networks APON, BPON, GPON and EPON. The EPON standard is explained in detail. The theoretical part of the thesis is concluded with a description of active elements that will form the laboratory measured network. Testing of designed passive optical network is performed in the practical part of the thesis. The measurement is divided into two chapters. The first chapter consist of measuring of the „inanimate network“, as there are missing active elements in the nominated net. Network measurements were done by a direct measuring method and reflectometric method. The second chapter of the practical part consists of measuring the parameters of quality of service (QoS). This chapter is divided into subchapters, such as: the measurement using RFC 2544 standard, the measurement using ITU-T standard Y.156 (EtherSam) and bit error rate testing (BERT). The practical part ends with a designed simulation network model, which was proposed in OptSim 5.2. The aim of the simulation model was to maximally resemble a real network, due to result comparison.

This diploma thesis is focused on realisation of the application, that process and display measured data from OTDR device. The first section describes optical fibers, transmission characteristics of fibers and measurement methods of the attenuation on optical path. The second section describes the principle of the OTDR method and measured events on optical path. Final part is dedicated to realisation of the appication by the assignment.