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MeasurementBlues
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Re: Testing Ethernet Compliance
MeasurementBlues   4/1/2014 8:28:54 AM
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Sanjib,

In this case, the formatting of the bits into packets don;t matter. Speed experiments are done using a PRBS pattern to assure an almost random set of bits. The point is to prove that data rates are possible. What those bits represent is irrelevant here.

zeeglen
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Re: Multimode?
zeeglen   3/31/2014 7:41:33 PM
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@ DKuchta In general, 1310nm VCSELs have lower ouput power and, to date, much lower modulation speeds than 850nm devices.


Thanks, this answers my question.  Was thinking of an external modulator rather than laser keying.  Amazing that VCSELs can be directly keyed at this rate!


 

DKuchta
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Re: Multimode?
DKuchta   3/31/2014 2:47:32 PM
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Is your question about fiber properties or VCSEL poperties?

In general, 1310nm VCSELs have lower ouput power and, to date, much lower modulation speeds than 850nm devices.  In the literature, 30Gb/s over 10km of single mode fiber has been demonstrated from a 1270nm (~1310nm) VCSEL.

For 1310nm VCSELs, the single mode fiber distance will be in the 10km range, limited by either the available optical power or the spectral width.

zeeglen
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Multimode?
zeeglen   3/30/2014 10:54:00 AM
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Since the 850 nm multimode fiber lengths have such significance in the test results, wonder what would the maximum lengths be using singlemode fiber at 1310 nm?

Sanjib.A
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Testing Ethernet Compliance
Sanjib.A   3/30/2014 3:36:18 AM
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While reading this article, a question just occurred to me, which I came across a few days back and I did not know the answer. To implement Fast Ethernet or Giga-bit Ethernet, we generally use the off-the-shelf processors with in-built MAC, 0ff-the-shelf PHY chips compliant to the Ethernet standard and magnetics, connectors per standard. What are the test cases which need to be done to check whether Ethernet implemented actually complied to the respective standards?



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As data rates begin to move beyond 25 Gbps channels, new problems arise. Getting to 50 Gbps channels might not be possible with the traditional NRZ (2-level) signaling. PAM4 lets data rates double with only a small increase in channel bandwidth by sending two bits per symbol. But, it brings new measurement and analysis problems. Signal integrity sage Ransom Stephens will explain how PAM4 differs from NRZ and what to expect in design, measurement, and signal analysis.

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