IOWN’s all-photonic network vision
What is the best way to send large amounts of data between locations? Its a question made all the more relevant with the advent of AI, and one that has been preoccupying the Innovative Optical and Wireless Network (IOWN) Global Forum that now has over 160 member companies and organisations
Optical networking has long established itself as the high-speed communications technology of choice for linking data centres or large enterprises’ sites.
The IOWN Global Forum aims to take optical networking a step further by enabling an all-optical network, to reduce the energy consumption and latency of communication links. Latency refers to the time it takes transmitted data to start arriving at the receiver site.
“The IOWN all-photonic network is the infrastructure for future enterprise networking,” says Masahisa Kawashima, IOWN technology director, IOWN development office, NTT Technology working group chair, IOWN Global Forum.
“The main significance of IOWN is setting a roadmap,” says Jimmy Yu, vice president and optical transport senior analyst at Dell’Oro. “It helps component and systems companies understand what technology and architectures that companies, such as NTT, are interested in for a next-generation optical and wireless network. It also fosters industry collaboration.”
IOWN architecture
The IOWN Global Forum’s all-optical network (APN) is to enable optical connectivity from edge devices to data centres at speeds exceeding 100 gigabits-per-second (Gbps).
The Forum envisions energy and latency performance improvements by driving optics to the endpoints. Linking endpoints will require a staged adoption of photonic technology as it continues to mature.
Professor Ioannis Tomkos, a member of the Optical Communications Systems & Networks (OCSN) Research Lab/Group at the Electrical and Computer Engineering Department at the University of Patras, says the aim of the IOWN Global Forum is to gradually replace electronics-based transmission, switching, and even signal processing functions with photonics. The OCSN Group recently joined the IOWN Global Forum.
The Forum has defined a disaggregated design for the all-photonic network. The following stages will include using optics to replace copper interconnect within platforms, interfacing photonics to chips, and, ultimately, photonic communications within a chip.
“If information-carrying light signals can remain in the optical domain and avoid opto-electronic and electro-optical conversions, that will ensure enhanced bandwidth and much reduced power consumption per bit,” says Tomkos.
The IOWN Global Forum was created in 2019 by Japanese service provider, NTT, Sony, and Intel. Since then, it has grown to over 160 members, including cloud players Google, Microsoft, and Oracle, telecom service providers British Telecom, Orange, KDDI, Telefónica, and companies such as Nvidia.
The Forum has developed an IOWN framework that includes the all-photonic network, digital twin computing (DTC), and a ‘cognitive foundation’ (CF). Digital twin computing enables the creation of virtual representations of physical systems, while the cognitive foundation is the architecture’s brain, allocating networking and computing resources as required.
“We expect future societies will be more data-driven and there will be many applications that collect huge real-time sensor data and analyse them,” says Kawashima. “The IOWN all-photonic network and disaggregated computing platforms will enable us to deploy digital twin application systems in an energy-efficient way.”
Optical infrastructure
The IOWN Global Forum’s all-photonic network uses open standards, such as the OpenROADM (Open reconfigurable optical add-drop multiplexing) Multi-Source Agreement (MSA), the OIF and the OpenZR+ MSA pluggable coherent optics, and the OpenXR Optics Forum standards. The IOWN Global Forum also adheres to the ‘white box’ platform designs defined by the Telecom Infra Project (TIP).
“There is a lot of similarity with the approach and objectives of TIP,” says an unnamed industry veteran who has observed the IOWN Global Forum’s organisation since its start but whose current employer is not a member. “Although the scope is not the same, I cannot help but wonder why we don’t combine the two as an industry.”
Kawashima says that optical hardware, such as ROADMs, pluggable optics, and transponder boards, is located at one site and operated by one organisation. Now, the Forum has disaggregated the design to enable the ROADM and transponders to be in different locations: the transponder can be deployed at a customer’s premises, remote from the ROADM’s location.
“We allow the operator of the switch node to be different from the operator of the aggregator node, and we allow the operator of the transponder node to be different from the operator of the ROADM nodes,” says Kawashima.
The disaggregation goal is to encourage the growth of a multi-operator ecosystem, unlike how optical transport is currently implemented. It is also the first stage in making the infrastructure nodes all-optical. Separating the transponder and the ROADMs promises to reduce capital expenditure, as the transceiver nodes can be upgraded separately from the ROADMs that can be left unchanged for longer.
Kawashima says that reducing infrastructure capital expenditure promises reduced connectivity prices: “Bandwidth costs will be cheaper.”
Service providers can manage the remote transponders at the customers’ sites, creating a new business model for them.
Early use cases
IOWN has developed several use cases as it develops the technology.
One is a data centre interconnect for financial service institutions that conduct high-frequency trading across geographically dispersed sites.
Another is remote video production for the broadcast industry. Here, the broadcast industry would use an all-photonic network to connect the site where the video feed originates to the cloud, where the video production work is undertaken.
A third use case is for AI infrastructure. An enterprise would use the all-photonic network to link its AI product development engineers to GPU resources hosted in the cloud.
If the network is fast enough and has sufficiently low latency, the GPUs can source data from the site, store it in their memory, process it, and return the answer. The aim is for enterprises not to need to upload and store their data in the cloud. “So that customers do not have to be worried about data leakages,” says Kawashima.
The Forum also publishes documents. “Once the proof-of-concept is completed, that means that our solution is technically proven and is ready for delivery,” says Kawashima.
Goals
At OFC 2025, held earlier this year, NTT, NTTCom, Orange, and Telefónica showcased a one terabit-per-second optical wavelength circuit using the IOWN all-photonics network.
The demonstration featured a digital twin of the optical network, enabling automated configuration of high-speed optical wavelength circuits. The trial showcased the remote control of data centre communication devices using an optical supervisory channel.
The Forum wants to prove the technical feasibility of the infrastructure architecture by year-end. It looks to approve the remote GPUs and financial services use cases.
“What we are trying to achieve this year is that the all-photonic network is commercially operable, as are several use cases in the enterprise networking domain,” says Kawashima.
IOWN’s ultimate success will hinge on the all-photonic network’s adoption and economic viability. For Kawashima, the key to the system architecture is to bring significant optical performance advantages.
Tomkos cautions that this transformation will not happen overnight and not without the support of the global industry and academic community. But the promise is growth in the global network’s throughput and reduced latency in a cost and power-efficient way.
Ciena's multi-format 400G coherent QSFP-DD pluggable
Ciena showcased a working 400-gigabit Universal coherent pluggable module at the ECOC 2022 conference and exhibition in Basel, Switzerland.
Ciena is using its WaveLogic 5 Nano coherent digital signal processor (DSP) for the Universal QSFP-DD coherent pluggable module.
“We call it universal because it supports many transmission modes – interoperable and high performance; the most in the industry,” says Helen Xenos, senior director of portfolio marketing at Ciena.
The pluggable has custom extended-performance modes and supports three industry formats: the 400ZR interoperable standard, the 400ZR+ multi-source agreement (MSA), and the OpenROADM MSA. (See tables below).
IP over DWDM
Communications service providers (CSPs) want to add pluggable coherent modules to their IP routers, removing the need for a separate transponder card or box linking the router to the optical line system.
The advent of coherent QSFP-DD pluggables has meant the same form factor can be used for client-side and line-side optics, ensuring efficient use of the router ports.
The CSPs want the coherent QSFP-DD module to have sufficient optical performance to meet their demanding networking requirements. For example, the module’s output signal can pass through the filtering stages of reconfigurable optical add-drop multiplexers (ROADMs) along the optical link.
Optical amplification and filtering
Ciena’s coherent QSFP-DD adds a fibre-based optical amplifier and a tunable optical filter to the coherent photonics and electronic ICs.
The optical amplification enables the high-performance mode and the launching of a 4dBm output signal. In contrast, 400ZR and 400ZR+ have a launch power of -10dBm.
“This is the industry’s highest [QSDP-DD] transmit power,” says Xenos.
The tunable optical filter improves the optical performance of the coherent receiver.
In an optical line system with colourless ROADMs, the Erbium-doped fibre amplifiers (EDFAs) generate out-of-band transmission noise – amplified spontaneous emission (ASE). The noise sources superimpose and become significant, impairing wavelength and system performance dramatically.
The tunable optical filter eliminates this effect and simplifies deployment over any photonics line system. In addition, Ciena says the pluggables can now work alongside high-baud rate transponders in existing ROADM applications.
The QSFP-DD’s tunable optical filter means its optical performance closely matches that of the CFP2-DCO, aiding the two classes of pluggables working together.
Modes of operation
400ZR defines the module’s baseline coherent performance. The OIF developed the 400ZR standard so hyperscalers can link their equipment in two separate data centres up to 120km apart.
The 400ZR specification delivers just enough optical performance to meet the optical link budget. The OIF produced a low-cost, interoperable, pluggable coherent specification.
400ZR supports a single baud rate – 60 gigabaud (GBd), and modulation scheme – dual-polarisation 16-QAM, and carries Ethernet frames.
Google, Meta, Microsoft and Alibaba were all involved in the OIF development, with the 400ZR Implementation Agreement published in early 2020.
400ZR supports two-channel widths: 75GHz and 100GHz, while the forward error correction scheme used is CFEC.
The 400ZR+ MSA enhances the performance by supporting other data rates – 100, 200 and 300 gigabits-per-second (Gbps) – as well as 400Gbps. In addition, it uses several modulation schemes and the enhanced O-FEC error correction scheme that extends reach.
Ciena’s module also meets the OpenROADM MSA, supporting Ethernet and OTN and an enhanced reach at 400Gbps.
Ciena’s Universal module’s extended performance modes up the symbol rate to 65 and 70 gigabaud (GBd) and uses probabilistic constellation shaping (PCS).
PCS maps the bitstream onto the constellation to maximise the data recovery at the coherent receiver, thereby improving overall optical performance. The scheme also allows the fine-tuning of the data rate sent.
At ECOC, Ciena showed the module implementing the high-performance mode at 70GBd and PCS.
ECOC innovation award
The ECOC Exhibition Market Focus Advisory Committee awarded the most innovative product award to Ciena’s WaveLogic 5 Nano 400G Universal QSFP-DD.
Lumentum ships a 400G CFP2-DCO coherent module
Lumentum has started supplying customers with its CFP2-DCO coherent optical module. Operators use the pluggable to add an optical transport capability to equipment.
The company describes the CFP2-DCO as a workhorse; a multi-purpose pluggable for interface requirements ranging from connecting equipment in separate data centres to long-haul optical transmission. The module works at 100-, 200-, 300- and 400-gigabit line rates.
The pluggable also complies with the OpenROADM multi-source agreement. It thus supports the open Forward Error Correction (oFEC) standard, enabling interoperability with oFEC-compliant coherent modules from other vendors.
“We are encountering a fundamental limit set by mother nature around spectral efficiency,”
“Optical communications is getting more diverse and dynamic with the inclusion of the internet content providers (ICPs) alongside traditional telecom operators,” says Brandon Collings, CTO at Lumentum.
The CFP2-DCO module is being adopted by traditional network equipment makers and by the ICPs who favour more open networking.
CFP2-DCOs modules from vendors support the OIF’s 400ZR standard that links switching and routing equipment in data centres up to 120km apart and more demanding custom optical transmission performance requirements, referred to as ZR+.
So what differentiates Lumentum’s CFP2-DCO from other coherent module makers?
Kevin Affolter, Lumentum’s vice president, strategic marketing for transmission, highlights the company’s experience in making coherent modules using the CFP form factor. Lumentum also makes the indium phosphide optical components used for its modules.
“We are by far the leading vendor of CFP2-ACO modules and that will go on for several years yet,” says Affolter.
Unlike the CFP2-DCO that integrates the optics and the digital signal processor (DSP), the earlier generation CFP2-ACO module includes optics only, with the coherent DSP residing on the line card.
The company also offers a 200-gigabit CFP2-DCO that has been shipping for over 18 months.
As a multi-purpose design, Affolter says some customers want to use the CFP2-DCO primarily at 200 gigabits for its long-haul reach while others want the improved performance of the proprietary 400-gigabit mode and its support of Ethernet and OTN clients.
“Each of the [merchant] DSPs has subtly different features,” says Affolter. “Some of those features are important to protect applications, especially for some of the hyperscalers’ applications.”
Higher baud rates
Lumentum did not make any announcements at the recent OFC virtual conference and show regarding indium phosphide-based coherent components operating at the next symbol rate of 128 gigabaud (GBd). But Collings says work continues in its lab: “This is a direction we are all headed.”
The latest coherent optical components operate at 100GBd, making possible 800-gigabit-per-wavelength transmissions. Moving to a 128GBd symbol rate enables a greater reach for the given transmission speed as well as the prospect of 1.2+ terabit wavelengths.
This means fewer coherent modules are needed to send a given traffic capacity, saving costs. But moving to a higher baud rate does not improve overall spectral density since a higher baud rate signal requires a wider channel.
“We are encountering a fundamental limit set by mother nature around spectral efficiency,” says Collings.
Optical transmission technology continues to follow the familiar formula where the more challenging high-end, high-performance coherent systems start as a line-card technology and then, as it matures, transitions to a more compact pluggable format. This trend will continue, says Collings.
The industry goal remains to scale capacity and reduce the dollars-per-bit cost and that applies to high-end line cards and pluggables. This will be achieved using greater integration and increasing the current baud rate.
“Getting capacity up, driving dollars-per-bit down is now what the game is going to be about for a while,” says Collings.
Whether the industry will go significantly above 128GBd such as 256GBd remains to be seen as this is seen as a technically highly challenging task.
However, the industry continues to demand higher network capacity and lower cost-per-bit. So Collings sees a couple of possible approaches to continue satisfying this demand.
The first is to keep driving down the cost of the 128GBd generations of transceivers, satisfying lower cost-per-bit and expanding capacity by using more and more transceivers.
The second approach is to develop transceivers that integrate multiple optical carriers into a single ‘channel’. A channel here refers to a unit of optical spectrum managed through the ROADM network. This would increase capacity per transceiver and lower the cost-per-bit.
“Both approaches are technical and implementation challenges and it remains to be seen which, or both, will be realised across the industry,” says Collings.
100-gigabit PAM-4 directly modulated laser
At OFC Lumentum announced that its 100-gigabit PAM-4 directly modulated laser (DML), which is being used for 500m applications, now supports the 2km-reach FR single-channel and FR4 four-channel client-side module standards.
This is a normal progression of client-side modules for the data centre where the higher performance externally-modulated laser (EML) for a datacom transceiver is the one paving the way. As the technology matures, the EML is replaced by a DML which is cheaper and has simpler drive and control circuitry.
“We started this [trait] with the -LR4 which was dominated by EMLs,” says Mike Staskus, vice president, product line management, datacom at Lumentum. “The fundamental cost savings of a DML is its smaller chip size, more chips per wafer, and fewer processes, fewer regrowths.”
The company is working on a 200-gigabit EML and a next-generation 100-gigabit DML that promises to be lower cost and possibly uncooled.
Reconfigurable optical add-drop multiplexers (ROADMs)
Lumentum is working to expand its wavelength-selective switches (WSSes) to support the extended C-band, and C- and L-band options as a way to increase transmission capacity.
“We are expanding the overall ROADM portfolio to accommodate extended C-band and more efficient C-band and L-band opportunities to continue to build capacity into ROADM networks,” says Collings. “As spectral efficiency saturation sets in, we are going to need more amplified bandwidth and more fibres, and the C- and L-bands will double fibre capacity.”
The work includes colourless and directionless; colourless, directionless and contentionless, and higher-degree ROADM designs.
Acacia unveils its 400G coherent module portfolio
Acacia Communications has unveiled a full portfolio of 400-gigabit coherent optics and has provided test samples to customers, one being Arista Networks.
Delivering a complete set of modules offers a comprehensive approach to address the next phase of coherent optics, the company says.
The 400-gigabit coherent designs detailed by Acacia are implemented using the QSFP-DD, OSFP and CFP2 pluggable form factors.
Collectively, the pluggables support three performance categories: the 400ZR standard, OpenZR+ that is backed by several companies, and the coherent optics specification used for the Open ROADM multi-source agreement (MSA).
OIF-defined 400ZR standard designed for hyperscalers
“These are challenging specifications,” says Tom Williams, vice president of marketing at Acacia. “Even the 400ZR, where the objective has been to simplify the requirements.”
400ZR and OpenZR+
The OIF-defined 400ZR standard is designed for hyperscalers to enable the connection of switches or routers in data centres up to 120km apart.
The 400ZR standard takes in a 400 Gigabit Ethernet (GbE) client signal and outputs a 400-gigabit coherent signal for optical transmission.
“Hyperscaler customers want a limited subset of performance [with the ZR] because they don’t want to introduce operational complexity,” says Williams.
Acacia is implementing the 400ZR standard with two module offerings: the QSFP-DD and the OSFP.
Acacia is also a founding member of OpenZR+, the industry initiative that supports both 400ZR and extended optical performance modes. The other OpenZR+ members are NEL, Fujitsu Optical Components, Lumentum, Juniper Networks and Cisco Systems which is in the process of acquiring Acacia.
OpenZR+ supports 100GbE and its multiples (200GbE and 300GbE) input signals, not just 400GbE as used for ZR. To transmit the 200- 300- and 400GbE client signals, OpenZR+ uses quadrature phase-shift keying (QPSK), 8-ary quadrature amplitude modulation (8-QAM), and 16-QAM, respectively.
OpenZR+ also employs an enhanced forward-error correction (oFEC) used for the Open ROADM specification and delivers improved dispersion compensation performance.
“OpenZR+ is not just about going further but also being able to offer more functionality than 400ZR,” says Williams.
Acacia is implementing OpenZR+ using the QSFP-DD and OSFP form factors.
Open ROADM
The Open ROADM specification is the most demanding of the three modes and is targeted for use by the telecom operators. Here, a CFP2-DCO module is used due to its greater power envelope. And while the Open ROADM optics is aimed at telcos, the CFP2-DCO also supports OpenZR+ and 400ZR modes.
“The telcos are not as focussed on [face plate] density,” says Williams. “The CFP2-DCO has a higher output and is not limited to just Ethernet but also multiplexed client signals and OTN.”
Since line cards already use CFP2-DCO modules, the Open ROADM module enables a system upgrade. Existing line cards using the 200-gigabit CFP2-DCO may not support 400GbE client signals but with the Open ROADM CFP2’s higher symbol rate, it offers enhanced reach performance.
This is because the Open ROADM CFP2-DCO uses a 64 gigabaud (GBd) symbol rate enabling a 200-gigabit signal to be transmitted using QPSK modulation. In contrast, 32GBd is used for the existing 200-gigabit CFP2-DCOs requiring 16-QAM. Using QPSK rather than 16-QAM enables better signal recovery.
There is also an interoperability advantage to the new CFP2-DCO in that its 200-gigabit mode is compliant with the CableLabs specification.
All three designs – 400ZR, OpenZR+ and Open ROADM – use Acacia’s latest 7nm CMOS Greylock low-power coherent digital signal processor (DSP).
This is the company’s third-generation low-power DSP following on from its Sky and Meru DSPs. The Meru DSP is used in existing 32GBd 100/ 200-gigabit CFP2-DCOs.
3D stacking
Acacia has spent the last year and a half focusing on packaging, using techniques from the semiconductor industry to ensure the pluggable form factors can be made in volume.
The higher baud rate used for the 400-gigabit coherent modules means that the electronic ICs and the optics need to be closely coupled. “Moving up the baud rate means that the interconnection between the [modulator] driver [chip] and the modulator can become a limiting factor,” says Williams.
Acacia is not detailing the 3D design except to say that the Greylock DSP, its silicon-photonics photonic integrated circuit (PIC), and the modulator driver and trans-impedance amplifier (TIA) are all assembled into one package using chip-stacking techniques. The chip is then mounted onto a printed circuit board much like a BGA chip, resulting in a more scalable process, says Acacia.
“We have taken the DSP and optics and turned that into an electronic component,” says Williams. “Ultimately, we believe it will lead to improvements in reliability using this volume-repeatable process.”
Acacia says its modules will undergo qualification during most of this year after which production will ramp.
No one module design will be prioritised, says Williams: “There are a lot of benefits of doing all three, leveraging a lot of common elements.”