Daisy Chained Fiber Explained

By Brian Rhodes, Published Jul 26, 2013, 12:00am EDT (Info+)

Fiber is a mainstay for networking cameras run far apart. The number of cameras seldom matches the fiber available, and having two strands to run multiple cameras can be a showstopper. In this case, 'daisy chaining', or running multiple cameras in series is a common solution, but it can be a major headache when equipment breaks. In this note we look at fiber 'daisy chaining', discussed why it is used, and what options for improving reliability are available.

Definition

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The ***** ******** *********

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Ideal ** *********

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Comments (6)

we are using the same ring topology in our upcoming project for perimeter cameras

We use this apporach with many perimeter or multi-building systems. If possible and economically feasible, it's best practice to run the return fiber (segment 3 in the above diagram) back to the switch in a separate conduit. That way if a conduit gets cut (happens a lot when utilities contractors trench) there is no loss of functionality.

The minumum density of fiber that we pull is a 6-strand. The cost difference between a 2-strand fiber and a 6-strand is fairly minimal as part of the overall cost (trenching, conduit, labor). With a 6-strand, if you don't have a separate return conduit, you can still create the STP ring and have a pair of fiber left over.

We frequently face this kind of topology, and usually the question ends up being: Will the core switch with sfp module brand "X" work with media converter brand "Y"? To be on the safe side, we specify the same provider for both, or other times we just use the same media converters connected to a copper port of the core switch (instead of an SFP module).

I seriously doubt that the picture is what the text claims it is. Using a Reconfigurable Optical Add Drop Multipexor (ROADM) is silly on its face. And there are no multimode ROADMs. The fiber in the picture is all orange and therefore not single mode. And -- unless you needed to send video TO the cameras, you would just use colored optic SFPs and sort it out with a CWDM mux at the hub site. But this is still not a good idea.

Standard data wiring is radial from concentration points -- usually in data closets. I assume that the problem is outdoor cameras that exceed the 100 M copper cable distance. Otherwise that would be the more cost-effective and maintainable solution. If you need to use fiber to get to the distant cameras, you should run it radially back to a serving switch. You can use the same conduit layout as you would for daisy-chained -- just run multiple fiber circuits in the cable. One conclusion in the article that I agree with is that glass is cheap. The money is in the conduit.

What are the brands of the media converters?

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If you going back with the fiber to the switch (better with one additional switch, where both are interconnected) after the last cam/media converter, then you building a classic "campus topology", and it will be less issue if something brakes in the chain or maintaining one of the switches.

Sometimes this is more wisely to build than building "star topology", even if my preferred topology is star.

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