IEEE802.3aq%20Channel%20model%20ad%20hoc%20Task%202:%20Time-varying%20study%20

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IEEE802.3aq Channel model ad hocTask 2
Time-varying study modal noise

• Teleconference notes, 13 Oct 2004
• Jonathan King

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Agenda

• attendees
• update on activities
• Time variance in MMF links - further tests
  -Robert Coenen
• Proposed experiments on time-variation due to
  polarization and MMF shaking and initial results
  - Jonathan King
• other business
• next meeting date/time

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1) Attendees

• Jonathan King, Big Bear Networks
• Petre Popescu, Quake
• Yu Sun, Optium
• Robert Coenen, Scintera
• Piers Dawe, Agilent
• John Ewen, JDSU
• Petre Popescu, Quake
• Petar Pepeljugoski, IBM
• Paul Kolesar, Systimax
• Piers Dawe, Agilent
• Bretwood Lock, Phyworks
• Gary Shaulov, Rsoft
• Joerg Kropp, Infineon
• Abijhit Shanbag, Scintera
• please let me know if you or your organization
  have been missed

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3)

• a) Time variance in MMF links - further tests -
  Robert Coenen
• Further experiments on vibrating a fibre coil
  (total of 10m fibre) vertically vibration
  amplitude was tailored as per GR 63 CORE (1g) A
  5GHz optical tone from a DFB laser was
  transmitted via an OSL launch and the vibration
  sidebands were recorded for worst case vibration
  axis and input polarization.
• Key findings
• Sideband height was proportional to the
  amplitude of movement.
• Second and higher sideband ratios are
  consistantly smaller than first.
• Max frequency at which vibration induced
  sidebands drop below -24dB (a nominal 'just
  noticeable' value) was 40Hz for the first
  sideband (24-28Hz for second and third
  sidebands).
• Similar experiments with a 900MHz carrier showed
  significantly reduced envelope modulation,
  showing the effect was due to impulse response
  variation rather than amplitude modulation.
• Optical switches introduced mode selective loss
  of 1dB before and after the main fibre
• Questions raised during discussion
• Was the noise floor affected by vibration,
  indicating a change in HF modal noise ?
• What was the fibre impulse response, and how
  does the impulse vary through the vibration cycle
  ?

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3)

• b) Proposed experiments on time-variation due to
  polarization and MMF shaking and initial results
  - Jonathan King
• Described test bed for measuring polarization
  and mechanical time varying effects, using a 3
  kinds of polarization explorer and 2 mechanical
  figure of 8 MMF shakers. Initial results compared
  envelopes of impulse response variation for a
  single mechanical MMF shaker (for 2 polarization
  inputs) a single mechanical MMF shaker and a
  polarization scrambler and 2 mechanical MMF
  shakers. Range of impulse response variation for
  last 2 shown to be equivalent.
• Discussion following
• TIA-F04 recommends a mechanical fibre shaker
  made up of 3 figure-of-8 elements.
• There was some discussion the cause of
  polarization dependence of impulse response.
  Joerg Kropp confirmed that in his experiments,
  only polarization was varied, and that mode
  selective loss through the system was negligible.
• Polarization induced variation of the channel
  was expected to depend somewhat on source type,
  because of spectral width differences.
  Polarization stability of VCSELs was raised as a
  potential issue in combination with the
  polarization effect, but experimental results
  with VCSELs did not show polarization instability
  to be an issue.

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4) Other business

• Petar Pepeljugoski requested a time slot in next
  weeks meeting for a presentation modal noise
  calculations

5) Next meeting

• Wednesday 20th Oct 9.30am PCT, 5.30pm UK