SOLITON STORAGE

Internship master : TOWN Graham

Stage 2002-2003

MERCIER Clotilde

2nd year - Option Physique

46, allée d’Italie

69364 Lyon Cedex 07

FRANCE

43, Boulevard du 11 novembre 1918

69622 Villeurbanne Cedex

FRANCE

Electronic Department

North Ryde NSW 2109

Sydney

AUSTRALIA

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

Problems which can happen with solitons during signal Problems which can happen with solitons during signal propagation in optical fiber loop :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

Solitons

AdvantagesAdvantages :

Soliton refers to special kinds of waves that can propagate undistorted over long distances and remain unaffected after collision with each other

• Gain control can be difficult in recirculating loop

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 :

Solitons (continuation)

LSMF. DSMF + LDCF.DDCF = 0

Thus we can define all the fiber we need (type, length…)

Dispersion details

Where :

L is the fiber length

D is the dispersion

Recirculating fiber loop

SMF-28 (1)

SMF-28 (2)

SMF-28 (3)

SMF-28 (4) SMF-28 (5) SMF-28 (6)

DCM-20

DCM-40

50:50 Coupler

Band-Pass filter (1.525-1.556 .10-6m)

EDFA AOM (1205-C/1206-C)

CircuitCircuit

Recirculating fiber loop topology (continuation)

• 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

Explanations about our choicesExplanations about our choices

• 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

MethodsMethods

• 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

Recirculating fiber loop topology (continuation)

Splice : connection between two optical fibers

Use of Fusion Splicer S175

ProblemsProblems :No program done for DCM-DCM splices

No program done for DCM-SMF splicesFind or create one

DCM-DCM splices : modification of one program parameters

DCM-SMF splices : use another apparatus

Fiber splicing

Definition :Definition :

Realisation :Realisation :

Splice loss determination :Splice loss determination :

Fiber splicing (continuation)

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/SMF-28), 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