Transcript SOLITON STORAGE

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