altera transceiver support burst mode?

Hi Rick,

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Have you ever heard about passive optical network. From the ONU to OLT, several clients will share the same physical link. In this case, ONU should send packet in optical layer to OLT in order not to interfere other clients packets. As a result, OLT should recover the clock very fast (packet usually contains preambles) - for detecting the effective packet.

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I have heard of it, but have never looked at any of the details.

What you describe occurs on the fiber. What happens at the optical-to-electrical interface? Is it simply optical-to-electrical conversion of whatever is on the fiber, or is something smarter used?

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In your case, what kind of transceivers I/O standard do you choose, basic or else? If there is no communication between nodes, do the links keep zero or send some training packets like K28.5..

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I use basic mode. There are two clocking methods that I need to investigate; lock-to-reference and lock-to-data. In lock-to-reference, the transceiver PLLs lock to an external reference clock and ignore the CDR recovered clock (if there is one), otherwise you can switch to a recovered clock (in lock-to-data mode). There are status bits in the transceiver block that indicate whether there is a CDR PLL lock. It sounds like you could use something similar; when there is no traffic, and the CDR PLLs lose lock-to-data, switch them back to lock-to-reference, then when data comes, they can go back to lock-to-data.

What you would need to investigate is how fast this can happen, and whether or not it will be sufficient to capture traffic. Given that the packet contains preambles, I suspect they are there for lock-to-data to occur. If you know the preamble length, and the worst-case lock-to-data time, you will be able to determine if it can work.

Cheers,

Dave