Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

[802.3_100GNGOPTX] Chomatic bandwidth of TxVEC



Title: RE: [802.3_100GNGOPTX] MMF ad hoc, Thursday 5th June, 2014, 9am to 10.30 am Pacific

On today’s MM ad-hoc call I suggested that there could be a way of assessing the actual chromatic dispersion of a transmitter in the proposed TxVEC measurement rather than the current approach of building into the fixture a filter that always included a worst-case value for chromatic dispersion based on the widest spectral width permitted.  The alternative would be to use a length of MMF chosen to have very high modal bandwidth (> ~10,000 MHz*km) at 850 nm.  This approach is already used in the measurement of single-mode transmitters.

 

The advantage2 of the approach include:

1.       not leaving margin on the table for transmitters having narrower than the maximum permitted spectral width,

2.       possibility of including MPN in the Tx test.

 

Disadvantages include:

1.       requiring a “specialty” MMF,

2.       the impact on measurement uncertainty due to variability of specimens of such fiber.

 

Contributions on this topic were previously presented to 802.3ba.  See kolesar_01_0309, kolesar_01_0509, kolesar_02_0509, and others.  At the time, these proposals were aimed at enabling extended-reach for 40G and 100G multimode solutions.  Now the purpose would be simply to improve yield of transmitters and accuracy/comprehensiveness of test.

 

The proposals were rejected by P802.3ba.  But it was suggested that I float the concept to 802.3bm to see if there was interest in pursuing it once more.

 

Your feedback will determine if I dust off the previous material for 802.3bm.  If there is a groundswell of support I will make the effort.  If the feedback is mostly negative I will not.

 

Regards,

Paul