Top 3 Reasons to Deploy Point-to-Multipoint Optics Within Conventional DWDM Networks

Anyone visiting the Infinera booth at OFC probably couldn’t fail to notice the buzz and excitement around ICE-X, Infinera’s new range of intelligent coherent pluggables for point-to-point ZR+ and point-to-multipoint XR optics applications. The live ICE-X demo was fully booked weeks before the event kicked off, showing the high level of interest in this new technology. Now, very importantly, ICE-X has moved from pre-release discussions and early trials to reality, with the first shipments to customers going out in Q1 of this year and starting to ramp in Q2.

ICE-X XR and ZR+ demos at OFC showcased a broad range of capabilities:

• Multiple network architectures with the new XR optics subcarrier-based point-to-multipoint architecture for traffic aggregation and high-speed business services over an existing PON infrastructure, in addition to record-breaking performance in a point-to-point ZR+ application.
• Multiple management strategies – in the point-to-point ZR+ demo, Infinera demonstrated a host-based management scheme in line with the industry’s management of ZR+ optics in IP host devices, and in the point-to-multipoint demo, a dual management scheme was used, highlighting host-independent management of ICE-X pluggables in four different host devices in line with the Open XR Forum’s management specifications.
• Five different host devices for ICE-X optics, including UfiSpace’s S9700-23D disaggregated router running DriveNets NOS software, Juniper’s PTX 10001 packet transport router, Edgecore’s AS-9726 data center switch running SONiC NOS software, Sumitomo Electric’s FTU9100 metro aggregation switch, and an Infinera ICE-X Network Demarcation Unit (ICE-X NDU). Naturally, the focus of this demo was the full XR optics architecture implemented via Infinera’s ICE-X optics hosted directly in a broad range of third-party devices. The only Infinera host in the demo was the ICE-X NDU, which is designed to support cases where mounting ICE-X optics directly into legacy host devices isn’t possible, such as in cases where the devices don’t support QSFP-DD optics.

Third-party host support is really important, but not all the time…

The full XR optics architecture of point-to-multipoint optics hosted directly in third-party devices has been modeled by network operators to show very significant total cost of ownership (TCO) savings, ranging from 45% up to even 70% in some applications. However, the XR optics architecture, and specifically the subcarrier-based variants of Infinera’s ICE-X portfolio, can also bring significant economic and operational advantages when subcarrier-based coherent optics are used within a conventional DWDM transport network where the coherent optics are still deployed in a transponder/muxponder.

There are really two main advantages of this concept – better network economics and enabling network designs that just aren’t possible any other way. But “top three reasons” sounds a lot better for a blog title, so I’ve split the overall TCO savings benefits into CapEx and OpEx elements. Apologies to anyone who was expecting more! So here are those top three reasons:

1. Lower CapEx costs with a reduced need for DWDM hardware within the network design
2. Lower OpEx costs with reduced space and power costs
3. Enabling single fiber working for coherent optics

Let’s look at those main advantages of economics and enabling something that was previously impossible to do in a bit more detail.

At the end of the day, cost per bit is key in optical transport networks

Working with network operators, we have modeled numerous networking scenarios to evaluate the economics of point-to-multipoint optics within DWDM networks. Naturally, the TCO savings aren’t as high as in the full XR optics architecture, as we have not hosted the coherent optics directly in the third-party device. We are still using transponders/muxponders and using grey optics between the DWDM system’s client ports and those third-party devices, just like in a normal DWDM network. But the use of point-to-multipoint optics within the DWDM network can allow higher-speed 400G ports to communicate directly with lower-speed 100G/200G ports, which can reduce the need for intermediate DWDM hardware or enable the use of simpler, more cost-efficient hardware in the network. It can also lower the number of coherent optics in the network or change the requirements to lower-speed and lower-cost coherent optics. Overall, network designs have shown savings on the order of 30% for both hardware CapEx and space- and power-related OpEx costs, which is very significant.

From an overall external interface perspective, these point-to-multipoint-enabled DWDM networks are exactly the same as conventional DWDM network designs, with the same grey optics interfaces to the client equipment and the same NMS/SDN interfaces northbound into the management domain. They simply take advantage of this new point-to-multipoint technology internally to provide better TCO. And of course, these networks can be a stepping stone to that full XR optics architecture in the future, where the coherent pluggables are hosted directly in third-party devices.

Bringing coherent optics to single-fiber domains

Many networks have domains that are built on single-fiber working (SFW) rather than fiber pairs. This could be an access network initially built to support PON infrastructure, or it could be deeper in the network where fibers are leased and it is more cost effective to use a single fiber. In the 10G DWDM era, this was no problem, as 10G direct-detect optics work fine over SFW. But as network capacity demands grow and higher-capacity DWDM is pushed closer to the edge of optical networks, pushing the optics up to higher 100G+ coherent optics speeds, then these single-fiber domains can be a real challenge as coherent optics generally don’t work over SFW.

While 10G direct-detect DWDM optics can easily use two different wavelengths over SFW – one per direction – modern coherent optics are challenged over this infrastructure as they use the transmitter laser as a local reference oscillator for the receiver, which locks both directions to the same wavelength. This capability is a benefit in normal dual-fiber networks but a real challenge in single-fiber infrastructure for higher-speed coherent DWDM optics. Using digital subcarrier-based XR optics, and Infinera’s ICE-X specifically, we can enable coherent DWDM over SFW infrastructure by using differing subcarriers within the same wavelength in each direction. This capability can be used in point-to-multipoint environments such as high-capacity PON overlay networks, as shown below, or in point-to-point links anywhere in a DWDM network design. As a reminder, the OFC demo included ICE-X optics over a single-fiber PON domain running both GPON and XGS-PON supplied by DZS.

This means ICE-X can take conventional DWDM networks running at 100G and above into these SFW domains, which just wasn’t possible before at these speeds. This capability is proving to be a very interesting application in network operator discussions. Check out this earlier blog I wrote discussing the importance of SFW in 5G networks after Heavy Reading reported in its 5G transport survey that 72% of operators view SFW as either critical or important.

Don’t just take my word for it…

I mentioned earlier that we have now started shipping our first ICE-X pluggables to customers, and we will be rapidly adding capabilities to the portfolio over the coming months. We have also carried out many network modeling exercises with network operators to compare standard designs to new point-to-multipoint XR optics-based designs. Some of these are included in a new ICE-X Point-to-Multipoint Optics in Infinera Metro DWDM Networks application note. Check out the application note and see how this technology can be used in numerous networking scenarios to lower TCO and/or enable coherent DWDM in places it just couldn’t go before.