Comparison of some Cambridge model results with simulation results of RSoft and Optium in-house simulators

1
Comparison of some Cambridge model results with
simulation results of RSoft and Optium in-house
simulators

• Gary Shaulov, RSoft Design Group
• Yu Sun, Optium

2
Outline

• The purpose of these preliminary studies was to
  check the results of Cambridge model for
  scaled/non-scaled index profiles against results
  by other mode solvers (both commercial and
  proprietary)
• Just two fiber models were studies fibers 23
  and 29 before and after scaling
• Optium in-house simulator results were compared
  with RSoft commercial multimode simulator
  (ModeSYS ) results
• Optium and RSoft simulation results were compared
  with results from Cambridge model for output
  pulse shapes, DMD evolution, scaling factors, and
  OFL bandwidth.

3
Comparison of RSoft and Optium in-house simulators
Pulse shape of output from multimode fibers were
studied for new scaled Cambridge index profiles

• Parameters
• Input beam Gaussian with 7 µm FWHM
• Input pulse Gaussian with 50 ps FWHM
• Wavelength 1300 nm
• Fiber interested Cambridge 23 and 29
• Offset considered 17, 20 and 23 µm
• Fiber length 300m

4
Comparison of Rsoft and Optium in house simulator
Fiber 23 with offset of 17 µm
RSoft
Optium
5
Comparison of Rsoft and Optium in house simulator
Fiber 23 with offset of 23 µm
RSoft
Optium
6
Comparison of Rsoft and Optium in house simulator
Fiber 23 with offset of 20 µm
RSoft
Optium
7
Comparison of Rsoft and Optium in house simulator
Fiber 29 with offset of 17 µm
RSoft
Optium
8
Comparison of Rsoft and Optium in house simulator
Fiber 29 with offset of 20 µm
RSoft
Optium
9
Comparison of Rsoft and Optium in house simulator
Fiber 29 with offset of 23 µm
RSoft
Optium
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Comparison of pulse shapes Optium vs Rsoft
Blue curves Optium Red curves RSoft
Fiber 29, offset 17 µm
Fiber 23, offset 17 µm
Very good agreement for both fibers
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Comparison of pulse shapes Optium vs Cambridge
Blue curves Optium Red curves Cambridge
Fiber 23 Offset 17 µm
Fiber 29 Offset 17 µm
Good agreement for fiber 29 but not so good for
fiber 23
12
DMD study for scaled and non-scaled index
profiles comparison of Rsoft and Cambridge
results

• Two fiber index profiles were studied - fiber 23
  and 29 (according latest to Cambridge release)
  first non-scaled and then scaled profiles.

13
Fiber 23

• Note fiber 23 in previous Cambridge release for
  65 fibers is fiber 18

14
Fiber 23 contd

• Cambridge model gives scaling factor for fiber
  23 f2.7054 (r.3.0)
• According to J.Abbotts presentation OFL_BW600
  MHz km, DMD mean 1.98 ns/km
• RSoft simulations give in case of non-scaled
  index DMD3.3 ps/m, in case of scaled even higher
  DMD 5.9 ps/m.
• The difference in results may be due also to the
  difference in calculation methods for DMM

Calculated scaling factor 2/3.30.6 Calculated
OFL_BW 480 MHz km
15
Fiber 29

• Note fiber 29 in previous Cambridge release for
  65 fiber is fiber 24

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Fiber 29 contd

• Cambridge model gives scaling factor for fiber
  29 f0.8424 (r.3.0)
• According to J.Abbotts presentation OFL_BW660
  MHz km, DMD mean2.18 ns/km
• RSoft simulations give in case of non-scaled
  index DMD5.2 ps/m, in case of scaled index DMD
  4.7 ps/m.
• The difference in results may be due also to the
  difference in calculation methods for DMD

Calculated scaling factor f2/5.20.38 Calculated
OFL_BW 480 MHz km
17
DMD results comparison
Corning/Cambridge (DMD scaled)
RSoft (non-scaled)
See John Abbotts presentation at telecon
7/28/2004
18
Preliminary Conclusions

• The agreement between RSoft and Optium in-house
  simulators is excellent.
• Both RSoft and Optium results are in good
  agreement with Cambridge results for fiber 29,
  however for fiber 23 there is discrepancies
  between Cambridge and RSoft/Optium
• The agreement between RSoft and Cambridge models
  results in DMD evolution behavior is good except
  points at very high values of offsets
• More studies needed to identify if the difference
  comes from difference in approaches to calculate
  mean DMD
• Cambridge model prescribes to ignore degenerate
  mode groups with ggt20 (or ggt18?). It may be not
  always the case for RSoft and Optium mode solvers
  can that be the cause of discrepancies, and
  should we worry about higher order modes?