Were those really due to Rayleigh instability?

1. Long non-periodic filaments

• +3 more (Hand ’88, Driscoll ’91, Dianov ’92)
• The void is a capture of “incipient process”.  “Bubbles in optical fibers …
  are compatible with” Rayleigh instability —Atkins ’03

2. Counterarguments

• Viscosity of the melt is too high (Yakovlenko ’04)
• Can’t explain why O₂ is in the voids (Kashyap ’13)
• Similar void appears at a sudden pump power drop (this study)
  
  Launched light in the past experiments must be modulated w/o knowing it.
  (floating dust?)