Showing posts with label 400G ZR. Show all posts
Showing posts with label 400G ZR. Show all posts

Sunday, August 15, 2021

Blueprint column: Wavelength routing in the 400GE era

by Arnold Jansen, Senior Product Marketing Manager, Nokia

The introduction of 400 Gigabit Ethernet (GE) pluggable digital coherent optics (DCOs) has stirred up considerable debate about innovative approaches to metro access and metro/regional network design that blend IP and optical networking technologies in more optimal ways. The key question is how this technology can be leveraged to more cost-efficiently meet service-level requirements without adding more complexity to network operations. 


Routers, ROADMs and rings

Due to their lower cost, power and space requirements, pluggable 400GE DCOs are generally more economical for shorter reaches than connecting routers to dense wavelength division multiplexing (DWDM) transponders in optical line systems. With in-line amplification, 400ZR+ coherent optics can interconnect 400GE router ports over hundreds of kilometers of fiber, and up to 1,000 km at lower bit rates. 

This capability is certainly adequate for most point-to-point fiber applications, but dedicated fiber may not be readily available where it is needed because laying new fiber is costly and time consuming. At least initially, new 400GE router-to-router connections will be implemented over existing fiber plant in metro/regional access and aggregation networks. This fiber is typically laid as interconnected and overlapping rings that aggregate traffic from multiple central offices. 

An IP-centric way to look at metro/regional access and aggregation rings is as a distributed leaf-spine fabric with access routers on the ring (the leaves) connecting into a centralized aggregation router at the ring head-end (the spine). Ideally, each access leaf directly connects with the spine in a logical hub-and-spoke IP topology, especially since the volume and growth of ingress traffic on individual access leaves can differ greatly in urban and regional settings. This allows transport efficiency and latency to remain low and deterministic, as access traffic on the ring is passed to the hub router in a single hop. 

The first option to implement this target architecture leverages 2-degree ROADMs and optical transponders (OTs) to connect access routers to the centralized hub router over protected, point-to-point wavelengths. This is the present mode of operation (PMO) for most communication service provider networks, and is depicted at the left side of Figure 1. Routers connect using 400GE gray optics to performance-optimized OTs that can operate over long fiber spans with many ROADM hops, allowing single-hop connections from each access router to the hub node at full 400G rates.  

Figure 1. IP aggregation over metro/regional fiber rings

In the center, future mode of operation 1 (FMO1) leverages 400ZR+ pluggable router optics instead of WDM transponders to save space, power and cost through IP-optical integration. Through 2-degree ROADMs, all access routers connect to the hub router in a single hop over dedicated wavelengths. For large rings with many nodes, it may be necessary to reduce the line rate of 400ZR+ pluggable DCOs for an increased reach when and where it’s needed. 

On the right side of Figure 1, FMO2 bypasses ROADMs altogether and interconnects routers in a daisy chain over point-to-point WDM line systems between each node on the ring. Each router aggregates local ingress traffic with transit traffic from other nodes, and passes it hop-by-hop along the ring until it reaches the hub router at the ring head-end. With wavelengths having to travel only one hop to the adjacent routers, 400ZR/ZR+ DCOs can connect at the full 400 Gb/s line rate for most router-to-router distances. 

Figure 2. Comparing scaling properties of PMO, FMO1 and FMO2 in aggregation rings 

Figure 2 compares the scaling properties of the PMO with FMO1 and FMO2 for a single aggregation ring with varying numbers of access nodes and amounts of ingress traffic. Although this is a simple modeling exercise, it illustrates several points:  

  1. The PMO scales the best with increasing traffic and ring sizes and makes the most efficient use of available 400GE router ports. Although DWDM transponders cost more than pluggable DCOs, fewer of them are required on each ring and current investments in ROADMs and fiber can be fully leveraged. Also note that pluggable 400G Multihaul DCOs will become available for  routers to enable higher capacity-reach over 400ZR+, and as a lower-cost alternative to DWDM transponders. 
  2. The FMO1 can be deployed as an overlay to offload the PMO over an additional fiber pair. While FMO1 consumes slightly more 400GE router ports for larger rings and traffic volumes, this upfront cost is offset by incremental savings created by using router pluggable 400ZR+ DCOs instead of WDM transponders. 
  3. FMO2 has a marginally lower upfront cost than FMO1 due to minor savings on ROADM capabilities, but its incremental scaling costs are much higher. There is a sweet spot for small rings and low initial ingress traffic volumes where access routers can aggregate all ring traffic over one or two wavelengths, but the number of 400G DCOs required will quickly surpass the 4–6 QSFP-DD network ports that are typically available on a 1 RU leaf aggregation router.

Key Takeaways 

From an end-to-end cost perspective, a critical objective of any network architect is to minimize the number of hops required to transport traffic between source and destination. Each router hop adds cost, latency and power consumption that must be offset by statistical multiplexing gains of packet aggregation, and these gains have diminishing returns with each hop. 

400GE pluggable coherent optics are a new and powerful technology that can be used to cost-optimize IP networks, provided that the number of router hops in the end-to-end data path does not increase significantly as a result. There are two ways to achieve this:

  1. Deploy dedicated point-to-point fiber routes where available and feasible. 
  2. Provision dedicated point-to-point wavelengths over shared fiber using ROADMs.

When point-to-point wavelengths must traverse several ROADMs, it is generally more economical to either de-rate the capacity of 400ZR+ optics or deploy higher-performance optics such as 400G Multihaul DCOs or 400GE OTs than to bridge the distance with additional router hops or back-to-back DCOs. Importantly, this new generation of compact and modular line systems with ROADM capabilities can ensure that the capacity-reach and cost benefits of 400GE pluggable coherent optics can be maximized for all applications. 

About the author - Arnold Jansen, Senior Product Manager, Nokia

Arnold is responsible for promoting products and solutions for the IP/optical networks group at Nokia. Arnold has held a number of roles in research and innovation, sales, product management, and marketing during his 30 years in the telecommunications industry. Arnold is based in Ottawa, Canada and holds a Bachelor degree in Computer Science from the Rotterdam University of Applied Sciences


Monday, March 22, 2021

NeoPhotonics cover 800km reach with 400ZR+ QSFP-DD transceiver

NeoPhotonics demonstrated that its 400ZR+ QSFP-DD coherent pluggable transceiver can effectively transmit at a 400 Gbps data rate over a distance of 800 km in a 75GHz-spaced DWDM system with more than 3.5 dB of OSNR margin in the optical signal. 

This 400ZR+ coherent pluggable transceiver module is based on NeoPhotonics high performance coherent optics and its ultra-pure color tunable laser, and achieves a reach of 800 km while staying within the power consumption envelope of the QSFP-DD module’s power specification. 

Highlights:

  • This 800 km transmission demonstration was carried out on NeoPhotonics Transmission System Testbed and utilized 75 GHz spaced channels. 
  • The QSFP-DD uses NeoPhotonics Silicon Photonics based Coherent Optical Subassembly (COSA) and its ultra-narrow linewidth Nano-ITLA tunable laser. 

NeoPhotonics said the longer reach was enabled by the superior performance of these optical components along with a commercial digital signal processor (DSP) using proprietary forward error correction (FEC). The COSA exhibits low insertion loss and low impairments, making efficient use of the optical signal. The Nano-ITLA tunable laser exhibits ultra-low phase noise and low power consumption. Additionally, these components allow NeoPhotonics 400ZR+ QSFP-DD transceiver module to operate at a case temperature of up to 80 degrees Celsius, which is ten degrees higher than conventional telecom modules, thereby reducing air flow requirements resulting in lower fan speeds and reduced power for cooling in data centers.

NeoPhotonics QSFP-DD modules are in the final stages of qualification and have passed 2000 hours of High Temperature Operating Life (HTOL) and other critical tests per Telcordia requirements. The Company expects these modules to be at General Availability (GA) within the second quarter of 2021.

NeoPhotonics 400ZR+ QSFP-DD transceivers are designed to operate in 75 GHz spaced DWDM systems using 64 Channel Arrayed Waveguide Grating MUX and DMUX filters, such as those made by NeoPhotonics. In this case, a fully loaded fiber operating in the C-Band would provide a total of 25.6 Terabits per second (Tbps) capacity. To further maximize the data capacity of optical fibers, NeoPhotonics has developed an enhanced version of its ultra-low noise laser in a C++ LASERTM module, which has a tuning range of 6 THz, enabling a total fiber capacity of 32 Tbps using 400Gbps transceivers and 75 GHz channel spacing.

“We are excited to extend the operation of our QSFP-DD Coherent transceiver into metro and regional applications in this 400ZR+ configuration,” said Tim Jenks, Chairman and CEO of NeoPhotonics. “Advances in our ultra-pure light tunable laser, our silicon photonics integrated COSA and electronic DSPs have inexorably decreased the size, power and cost of coherent transmission such that a coherent transceiver capable of up to long haul distances can fit in the same form factor as a current generation high density client side pluggable module, such as a QSFP-DD. This has been a sea change for Data Center Interconnect networks, and we believe it will also bring fundamental changes to metro and regional networks,” concluded Mr. Jenks.

https://www.neophotonics.com/press-releases/?newsId=12251

NeoPhotonics ships QSFP-DD 400G ZR modules

NeoPhotonics announced the availability of its extended case temperature QSFP-DD 400G ZR modules.

NeoPhotonics said the new 400G ZR modules leverage its Silicon Photonics Coherent Optical Subassembly (COSA) and low power consumption, ultra-narrow linewidth Nano-ITLA tunable laser.  Each of these components can be operated over a wide module case temperature range up to 80C. This enables the Neophotonics 400G ZR modules to be deployed in extended temperature data center environments while reducing cooling requirements and fan power.

“The ability of 400G ZR vendors to offer thermally-optimized designs capable of supporting higher case temperatures will significantly help reduce system cooling requirements,” said Dr. Hacene Chaouch, Distinguished Engineer at Arista Networks. “This is an important consideration for implementing power efficient data center interconnect architectures.” 

“We are pleased to support customers with high-performance 400G ZR modules that operate across a wide thermal envelope, without sacrificing optical performance.” said Tim Jenks, Chairman and CEO of NeoPhotonics.  “By utilizing our leading high-speed coherent components technology and optimizing the entire optics suite through in-house design, we are able to favorably benefit data centers need to reduce power consumption and improve environmental sustainability,” concluded Mr. Jenks.

https://www.neophotonics.com/press-releases/?newsId=12221

Monday, March 9, 2020

Arista announces OSFP Optical Line System for 400G

Arista Networks announced an optical line system in an OSFP (Octal Small Form-factor Pluggable) module form factor. The OSFP-LS line system was purposely conceived and designed for the support of 400G ZR digital coherent optics.

The Arista OSFP-LS collapses legacy optical line systems into an OSFP module which can be plugged into any Arista OSFP port, supporting up to 8 DWDM wavelengths with a single fiber pair, and delivering up to 3.2Tbps of DCI traffic over 100km.

Arista describes its OSFP-LS as a highly compact, low power and cost-effective solution for increasing bandwidth between data centers without the need for external optical line systems. Features also include automatic setup with no operator configuration required.

“The OSFP-LS is far easier to deploy than conventional external line systems that require their own power feed and control management software while consuming valuable rack space. Interconnecting two data center sites with DWDM becomes as simple as connecting two switch ports,” said Hacene Chaouch, Distinguished Engineer, Arista Networks.

The OSFP-LS is in testing and qualification now with availability in 2H 2020.