How DSP smarts continue to improve optical transport

• Kim Roberts explains the signal processing techniques Ciena is using for its WaveLogic 6 coherent DSP.
• Roberts explains how the techniques squeeze, on average, a 15 per cent improvement in spectral efficiency.
• The WaveLogic 6 Extreme chip can execute 1,600 trillion (1.6 x 10¹⁵) operations per second and uses the equivalent of 4km of on-chip copper interconnect.

Part 2: WaveLogic 6's digital signal processing toolkit

Kim Roberts, Ciena’s vice president of WaveLogic Science and winner of the 2019 John Tyndall Award

Bumping into Kim Roberts on the way to the conference centre at OFC, held in San Diego in March, I told him how, on the Ciena briefing about its latest WaveLogic 6 coherent digital signal processor (DSP), there had been insufficient time to dive deeply into the signal processing techniques used.

“What are you doing now?” said Roberts.

“I’m off to the plenary session to catch the keynotes.”

Chatting some more, I realised I was turning down a golden opportunity to sit down with a leading DSP and coherent modem architect.

“Is that offer still open?” I asked.

He nodded.

We grabbed a table at a nearby cafe and started what would prove to be an hour-long conversation.

Click to read more ...

Do optical DACs have a role in future coherent modems?

• A proposed optical digital-to-analogue converter (oDAC) concept offers several system benefits, including better signal performance, higher bit rates and lower power consumption.
• The oDAC design benefits coherent optics but can also be used in direct-detect designs. This article focusses on coherent optics.
• Coherent system vendors are aware of oDAC technology but it is not part of their current roadmaps. 

A 256-QAM constellation using a conventional coherent transmitter (left) and using the oDAC. Note there is no modulator loss (the full area is used) nor any optical warping using the oDAC. Source: Tomkos and Nazarathy.

Click to read more ...

Ciena advances coherent technology on multiple fronts

• Ciena has unveiled the industry’s first coherent digital signal processor (DSP) to support 1.6-terabit wavelengths
• Ciena announced two WaveLogic 6 coherent DSPs: Extreme and Nano
• WaveLogic 6 Extreme operates at a symbol rate of up to 200 gigabaud (GBd) while the Nano, aimed at coherent pluggables, has a baud rate from 118-140GBd

Part 1: WaveLogic 6 coherent DSPs

Helen Xenos

Ciena has leapfrogged the competition by announcing the industry’s first coherent DSP operating at up to 200GBd.

The WaveLogic 6 chips are the first announced coherent DSPs implemented using a 3nm CMOS process.

Ciena’s competitors are - or will soon be - shipping 5nm CMOS coherent DSPs. In contrast, Ciena has chosen to skip 5nm and will ship WaveLogic 6 Extreme coherent modems in the first half of 2024.

Click to read more ...

The Metaverse and the network

CTO interviews part 1: Stephen Alexander

"The inability to precisely predict how we'll use it [the Metaverse], and how it will change our daily life, is not a flaw. Rather, it is a prerequisite for the Metaverse's disruptive force."

The Metaverse: And How it Will Revolutionize Everything by Matthew Ball, 2022.

CTO Interview 

Stephen Alexander's trusty 20-year-old dishwasher finally stopped working during the pandemic.

Unfortunately, getting spare parts shipped to the US was impossible, so Alexander, the CTO of Ciena (pictured), resorted to 'how-to' YouTube videos and got bits from eBay.

It highlighted the power of the online experience, something set to ramp significantly with the advent of the Metaverse.

Click to read more ...

ECOC '22 Reflections - Part 2

Gazettabyte is asking industry and academic figures for their thoughts after attending ECOC 2022, held in Basel, Switzerland. In particular, what developments and trends they noted, what they learned, and what, if anything, surprised them. 

maytikka, Shutterstock.com

In Part 2, Broadcom‘s Rajiv Pancholy, optical communications advisor, Chris Cole, LightCouting’s Vladimir Kozlov, Ciena’s Helen Xenos, and Synopsys’ Twan Korthorst share their thoughts.

Click to read more ...

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. 

A look inside Ciena's 400-gigabit Universal coherent pluggable module. TOF is the tunable optical filter. Source: 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).

Click to read more ...

Hyperscalers' needs drive a new class of coherent DSP

Coherent digital signal processors (DSPs) companies have supported two families of coherent chips for some time. That's because no single coherent DSP can meet all the market's requirements.

The coherent DSP used for highest-performance optical transmissions must include advanced coding techniques, forward error correction, and a high symbol rate to send as much data as possible on a single wavelength and maximise reach.

Helen Xenos at NGON & DCI World

In contrast, a DSP for coherent pluggable modules needs to be power-efficient and compact to meet the optical module's power envelope and size constraints; a 400ZR QSFP-DD and a CFP2-DCO 400ZR+ being examples.

According to Ciena, now there is a need for a third category of coherent DSP for 1.6 terabit-per-second (Tbps) and 3.2Tbps transmissions over short distances for next-generation switch routers.

Click to read more ...