1. Teleconference notes, 13 Oct 2004 Jonathan King
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise
Teleconference notes, 13 Oct 2004
Jonathan King
13 Oct 2004
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise

2. Agenda attendees update on activities other business
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
13 Oct 2004
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise

3. 1) Attendees Jonathan King, Big Bear Networks Petre Popescu, Quake
Yu Sun, Optium
Robert Coenen, Scintera
Piers Dawe, Agilent
John Ewen, JDSU
Petar Pepeljugoski, IBM
Paul Kolesar, Systimax
Bretwood Lock, Phyworks
Gary Shaulov, Rsoft
Joerg Kropp, Infineon
Abijhit Shanbag, Scintera
please let me know if you or your organization have been missed
13 Oct 2004
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise

4. 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 ?
13 Oct 2004
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise

5. 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.
13 Oct 2004
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise

6. 4) Other business 5) Next meeting
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
13 Oct 2004
IEEE802.3aq Channel model ad hoc Task 2: Time-varying study & modal noise