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Stage 2002-2003 MERCIER Clotilde 2nd year - Option Physique Electronic Department North Ryde NSW 2109 Sydney AUSTRALIA SOLITON STORAGE Internship master : TOWN Graham 46, allée d’Italie 43, Boulevard du 11 novembre 1918 69364 Lyon Cedex 07 69622 Villeurbanne Cedex FRANCE FRANCE Introduction : Internship presentation Solitons : - advantages - Problems Dispersion details Recirculating fiber loop : - Circuit - Explanations about our choices - Methods Fiber Splicing : - Definition - Realisation - Problems - Splice loss determination Conclusion / Aim Introduction : Internship presentation • Optic data packets transmission in network • Solitons are the natural way to transmit data in non-linear and dispersive optical fiber systems Necessity to have enough solitons Soliton storage by mean of recirculating loop Rerouting or bit rat Conversion Solitons Advantages : Soliton refers to special kinds of waves that can propagate undistorted over long distances and remain unaffected after collision with each other Problems which can happen with solitons during signal propagation in optical fiber loop : • Long distance transmission systems : deterioration of signals due to : - dispersion - Non-linear effects - Noise added by amplification each round-trip • Gain control can be difficult in recirculating loop Solitons (continuation) Dispersion details To limit dispersion during the recirculating in the loop, we use DCM (dispersion compensation) fiber With the length of DCF available : define length of SMF-28 fiber with the equation : LSMF. DSMF + LDCF.DDCF = 0 Where : L is the fiber length D is the dispersion Thus we can define all the fiber we need (type, length…) Recirculating fiber loop Circuit Band-Pass filter (1.5251.556 .106m) EDFA AOM (1205C/1206-C) SMF-28 (1) DCM-40 SMF-28 (2) SMF-28 (3) DCM-20 50:50 Coupler SMF-28 (4) SMF-28 (5) SMF-28 (6) Recirculating fiber loop topology (continuation) Explanations about our choices • 8 spools : allow to separate SMF (single mode fiber) section in the middle Optimum position for injection of transform-limited pulse into the fiber loop, as a minimum chirp point appears there • DCF (Dispersion-compensation fiber): minimise the non-linear effects • Band-Pass Filter : to remove the spontaneous emission noise and to cause pulse attenuation and to reduce non-linear effects before the SMF • AOM : placed before the EDFA (Erbium Doped Fiber Amplifier) to reduce the chance of saturation Recirculating fiber loop topology (continuation) Methods • Inject or couple in short bursts of optical pulses (1 Gb/s) from an externally modulated laser into the ring • Monitor the evolution as a function of input power, sequence duration, storage time, loop gain Fiber splicing Definition : Splice : connection between two optical fibers Realisation : Use of Fusion Splicer S175 Problems : No program done for DCM-DCM splices Find or create one No program done for DCM-SMF splices DCM-DCM splices : modification of one program parameters DCM-SMF splices : use another apparatus Fiber splicing (continuation) Splice loss determination : Making a splice, Fusion Splicer S175 indicates the loss in dB Impossible to define precise parameters on the Fusion Splicer S175 for making a particular splice ( for instance, SMF-28/SMF28), it depends how we cleave the fiber To determine the splice loss there are two anothers methods which are more precised than with the Fusion Splicer S175 : • With an OTDR (optical time-domain reflectometer) : launch a short and high power optical impulse into the fiber and a consequent detection of back scattered optical power as a response of the fiber • Cut back method of splice loss measurement Conclusion/Aim • Study and solve some problems associated with data storage ring • Comparison of the results to the performance of the storage ring without the additional control mechanisms • Hope : Improving the time for which the pulse groups may be stored before recovery without errors from noise • Use of storage ring in future projects requiring moderate term optical storage of very high bandwidth signals