Fixed vs tunable DWDM optics: understanding benefits & differences for telecom pros

In today’s Vitex Talks episode, we’ll explain the difference between fixed and tunable DWDM (dense wavelength-division multiplexing) optics and highlight the benefits of tunable optics, including inventory management, cost effectiveness, growth opportunity, and ease of installation.


(0:00-0:29) Intro
(0:30-1:38) Differences between fixed and tunable DWDM
(1:39-2:30) Tunable optics
(2:31-3:50) Why?
(3:51-4:54) Fixed optics
(4:55-5:55) ITU channels explained
(5:56-6:32) Conclusion

Complete Transcript


Hey everybody, this is Craig at Vitex, and today we’re going to be shining a light on some DWDM optics and especially if you’re in the line of work in telecom, you’re doing things like inventory management, you do things like field installation or field planning, then we have some good tips for you.

Differences between fixed and tunable DWDM

Before we get into what’s the difference in our options from a fixed to a tunable, let’s just understand what we’re talking about here in DWDM. Basically, we’re looking at our receive and transmit, right? On the receive side, our fixed and our tunable optics are going to be pretty much similar, right? We’re going to typically have an ADP that’s coming in that’s receiving all of our single wavelengths or multiple wavelengths, and it’s going to process it through the rest of the interface on the transceiver.

Coming the other way, our major difference we’re going to see here is in this tunable TOSA. What do we get here, right? At this point, we’re going to have the option of changing our wavelength. We don’t just have to pick, “Oh I’m on channel 37, I’m on channel 35.” You can actually pick whatever frequency and wavelength works best for you.

Right now we’re going to pause because we have a little bit of a challenge for you. You’ll probably see on the board behind me there are some math equations or statements that might seem like they’re wrong. Get some of your friends, your coworkers, hey, even your kids and see how many of these you can spot.

Tunable optics

But as we’re going through that we’re going to understand how the magic of tunable mathematics can really make all these statements true. One of the reasons I love tunable optics is because it allows us to look at different things related to our inventory, right?

Let’s just take this statement right over here. When are we ever going to have one that’s greater than 40 or 80? If we’re looking at the amount of different types of transceivers we’re going to have, if you’re using a single wavelength, you’re going to need multiple types of wavelengths, multiple different ones. If you have a tunable, then you’re able to use all of these channels, either 40 or 80, if we’re working in 100 gigahertz spacing, or if we’re working in 50 channel spacing, you only really need one.


What are some of the big “whys” that we’re going to get from this?

We’re going to look at our inventory which is over here. As I mentioned before, if you’re in inventory management, it makes it a lot easier to only have to worry about one type of module you need in your whole solution.

Okay. Costs, we’re going to get to that over here, and understand what are the different costs that are associated both from a unit perspective and from a whole solution perspective.

The next thing is growth, right? When you’re using fixed optics, you’re kind of just stuck. You’re at your one wavelength. You can’t do anything about it. If you’re growing your network and you have… It gives you opportunity to grow in different ways, to better yourself and better your network, right, through tunable. Next one is install ease. I was just talking before about how I needed channel 37 or 33. I totally forgot, right? But if I put the wrong optics in my solution and I’m connecting it to say a MUX or DEMUX product, I need that specific channel or it’s not going to work anywhere else. If I have tunable optics, it allows me to change it and I don’t have to worry about that. I’m never going to have that problem. For me, I really like change, but it comes at a price, right?

Fixed optics

If we look at our fixed optics, we know that they’re less, right? It’s just kind of, you’re getting this whole tunable, it’s a better performer, it allows more flexibility, so it costs more, so there’s a price on the single option. But when we talk about inventory, we’re going to have high levels of inventory because we’re going to have to worry about channel 21, channel 35, channel 40, whatever channels we’re using. But we can keep our inventory control low if we’re using tunable optics.

What about our total cost? Well, before, we talked about these numbers, right, how one wavelength is actually going to mean lots and lots of inventory of different types, so this is really in the end going to cost us a lot more money. And when we bring into problems with using the wrong optics, it costs a lot to roll a truck back out there and actually fix it just because the wrong optics were installed. At the end of the day, your total cost can be reduced if you go with the tunable optics.

ITU channels explained

But there’s one last thing, if you guys actually caught it, and for those of you who have kids, you may have heard of this like new mathematics that’s being used. When can we get 50 ever equal to 100? All right. Or what about 100 being equal to 50?

Of course, this is referencing our ITU channels. When we’re talking about 40 channels in 100G spacing versus typical 80 in 50, we’re able to use a 50 gigahertz spacing to give us all of the same channels that are available in 100, right? In this case, 50 does equal 100. But just like a square is a rectangle or a rectangle is not a square, I don’t actually remember which one it is, but in this case, it’s important to remember that 100 is not 50, right? If we buy a 100 gig solution, we’re not able to get all of those different channel numbers that are associated with our 50 gigahertz channel spacing. For right now, that’s it on fixed and tunable.


Again, I’m Craig. If you need to talk to us about a solution or drop us an email, we’re more than happy to help you out here at our New Jersey office. And that’s all for now. Until next time, I’ll see you then.

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