What is the expected impact of ZR on the DCI segment's pricing and market share
he network, where you're obviously talking about investments. But as some of the discussions around 5G picks up, and Nokia being the large incumbent there, how should we be thinking about the opportunity for share gains over the next few years in that part of the network? And I have a follow-up.
Gary B. Smith -- President and Chief Executive Officer
Scott, you want to take it?
Scott McFeely -- Senior Vice President, Global Products and Services, Ciena
Yes. So first of all, our Edge and Access piece, our next generation metro included in that, 5G is one driver there, also the evolution of an enterprise business services in general is another driver. I think we've talked in the past around our existing businesses, very strong in those areas, wireless backhaul and enterprise services in North America and India, I'll just say under distributed in the rest of the world, partially because historically it was not playing in the IP space. The investments that we're making there is really around our next generation IP capability with a ground-up IP OS integrated with our optics, integrated with our multilayer domain controllers, and then a series of products optimized for things like 5G, fiber deep and the next generation sort of aggregation networks for converged traffic.
All of those things we think is an opportunity that will show up in our Metro and our Packet business, and we expect that to grow faster than our aggregate part of the business going forward.
Now, 5G specifically, I think what's going on right now is sort of augmentation on their existing architectures, that will benefit us where we have wireless backhaul instalments today, but our real opportunity longer term is as they start to look at stand-alone architectures and make architectural decisions, that will allow us to expand our addressable market beyond our historical installed base of wireless backhaul.
Samik Chatterjee -- JP Morgan -- Analyst
Got it. And if I can follow-up with a question for Jim, just if you can give us some color on, you talked about the investments that are kind of probably going to be elevated for a bit here. But how long is that going to run for? Primarily, because if I think about what you said for your three-year outlook and you ended the year with 17.6% margin, which is higher than your long-term range. If I think about gross margins moderating a bit, but you also guided to having opex leverage for the three-year. Do we end up kind of three years out about the long-term range that you provided of 16% to 17%?
James E. Moylan, Jr. -- Senior Vice President, Finance & Chief Financial Officer
Without giving a specific number, I would say that we would expect operating margin to increase from what we're going to deliver in 2021, if we hit our plan. So yes, we said that we are going to grow opex more slowly than revenue would grow in the two years beyond 2021. We did indicate that our gross margins, we think our base rate of gross margins have improved a little bit. So yes, we do expect our operating margin over the next couple of years to increase than what we're going to post in 2021.
Gregg Lampf -- Vice President, Investor Relations
Thanks, Samik.
Samik Chatterjee -- JP Morgan -- Analyst
Thank you.
Operator
Your next question comes from Ryan Koontz of Rosenblatt Securities. Your line is open.
Ryan Koontz -- Rosenblatt Securities -- Analyst
Hi. Thanks for the question. As you look ahead to the impact from ZR on the DCI segment, assuming you're able to retain share with your incumbent customers there, how should we think about the deflationary price per wavelength there? Seems like pretty disruptive impact to pricing and when we think about that deflating the market there a little bit? Thank you.
Gary B. Smith -- President and Chief Executive Officer
Yes, Ryan, here's how I think about it, if you drive sort of the typical price erosion curve over the last decade in the optical space and you think about the timing of ZR and some of the price point that we sort of see in the marketplace, you can extrapolate that curve. It's the natural price
he network, where you're obviously talking about investments. But as some of the discussions around 5G picks up, and Nokia being the large incumbent there, how should we be thinking about the opportunity for share gains over the next few years in that part of the network? And I have a follow-up.
Gary B. Smith -- President and Chief Executive Officer
Scott, you want to take it?
Scott McFeely -- Senior Vice President, Global Products and Services, Ciena
Yes. So first of all, our Edge and Access piece, our next generation metro included in that, 5G is one driver there, also the evolution of an enterprise business services in general is another driver. I think we've talked in the past around our existing businesses, very strong in those areas, wireless backhaul and enterprise services in North America and India, I'll just say under distributed in the rest of the world, partially because historically it was not playing in the IP space. The investments that we're making there is really around our next generation IP capability with a ground-up IP OS integrated with our optics, integrated with our multilayer domain controllers, and then a series of products optimized for things like 5G, fiber deep and the next generation sort of aggregation networks for converged traffic.
All of those things we think is an opportunity that will show up in our Metro and our Packet business, and we expect that to grow faster than our aggregate part of the business going forward.
Now, 5G specifically, I think what's going on right now is sort of augmentation on their existing architectures, that will benefit us where we have wireless backhaul instalments today, but our real opportunity longer term is as they start to look at stand-alone architectures and make architectural decisions, that will allow us to expand our addressable market beyond our historical installed base of wireless backhaul.
Samik Chatterjee -- JP Morgan -- Analyst
 Got it. And if I can follow-up with a question for Jim, just if you can give us some color on, you talked about the investments that are kind of probably going to be elevated for a bit here. But how long is that going to run for? Primarily, because if I think about what you said for your three-year outlook and you ended the year with 17.6% margin, which is higher than your long-term range. If I think about gross margins moderating a bit, but you also guided to having opex leverage for the three-year. Do we end up kind of three years out about the long-term range that you provided of 16% to 17%?
James E. Moylan, Jr. -- Senior Vice President, Finance & Chief Financial Officer
Without giving a specific number, I would say that we would expect operating margin to increase from what we're going to deliver in 2021, if we hit our plan. So yes, we said that we are going to grow opex more slowly than revenue would grow in the two years beyond 2021. We did indicate that our gross margins, we think our base rate of gross margins have improved a little bit. So yes, we do expect our operating margin over the next couple of years to increase than what we're going to post in 2021.
Gregg Lampf -- Vice President, Investor Relations
Thanks, Samik.
Samik Chatterjee -- JP Morgan -- Analyst
Thank you.
Operator
Your next question comes from Ryan Koontz of Rosenblatt Securities. Your line is open.
Ryan Koontz -- Rosenblatt Securities -- Analyst
Hi. Thanks for the question. As you look ahead to the impact from ZR on the DCI segment, assuming you're able to retain share with your incumbent customers there, how should we think about the deflationary price per wavelength there? Seems like pretty disruptive impact to pricing and when we think about that deflating the market there a little bit? Thank you.
Gary B. Smith -- President and Chief Executive Officer
Yes, Ryan, here's how I think about it, if you drive sort of the typical price erosion curve over the last decade in the optical space and you think about the timing of ZR and some of the price point that we sort of see in the marketplace, you can extrapolate that curve. It's the natural price