Building the data rate out of smaller baud rates

In the second article addressing the challenges of increasing the symbol rate of coherent optical transport systems, Professor Andrew Lord, BT’s head of optical network research, argues that the time is fast approaching to consider alternative approaches.

Coherent discourse 2

Coherent optical transport systems have advanced considerably in the last decade to cope with the relentless growth of internet traffic.

Professor Andrew Lord

One-hundred-gigabit wavelengths, long the networking standard, have been replaced by 400-gigabit ones while state-of-the-art networks now use 800 gigabits.

Increasing the data carried by a single wavelength requires advancing the coherent digital signal processor (DSP), electronics and optics.

It also requires faster symbol rates.

Moving from 32 to 64 to 96 gigabaud (GBd) has increased the capacity of coherent transceivers from 100 to 800 gigabits.

Last year, Acacia, now part of Cisco, announced the first 1-terabit-plus wavelength coherent modem that uses a 128GBd symbol rate.

Other vendors will also be detailing their terabit coherent designs, perhaps as soon as the OFC show, to be held in San Diego in March.

The industry consensus is that 240GBd systems will be possible towards the end of this decade although all admit that achieving this target is a huge challenge.

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The many paths to 400 gigabits

The race is on to deliver 400-gigabit optical interfaces in time for the next-generation of data centre switches expected in late 2018.

The industry largely agrees that a four-wavelength 400-gigabit optical interface is most desirable yet alternative designs are also being developed.

Optical module makers must consider such factors as technical risk, time-to-market and cost when choosing which design to back.

Rafik Ward, FinisarUntil now, the industry has sought a consensus on interfaces, making use of such standards bodies as the IEEE to serve the telecom operators.

Now, the volumes of modules used by the internet giants are such that they dictate their own solutions. And the business case for module makers is sufficiently attractive that they are willing to comply.

Another challenge at 400 gigabits is that there is no consensus regarding what pluggable form factor to use. 

“There is probably more technical risk in 400 gigabits than any of the historical data-rate jumps we have seen,” says Rafik Ward, vice president of marketing at Finisar.

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Acacia looks to co-package its coherent PIC and DSP-ASIC

• Acacia Communications is working to co-package its coherent DSP and its silicon photonics transceiver chip. 

• The company is also developing a digital coherent optics module that will support 400 gigabit. 

Acacia Communications is working to co-package its coherent DSP and its silicon photonics transceiver chip. The line-side optical transceiver company is working on a digital coherent optics module that will support 400 gigabits.

Acacia announced last November that it was sampling the industry’s first CFP2 Digital Coherent Optics (CFP2-DCO) that supports 100- and 200-gigabit line rates. The CFP2-DCO integrates the DSP and its silicon photonics chip within a CFP2 module, which is half the size of a CFP module, with each chip packaged separately.

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Effdon Networks extends the 10x10 MSA to 80km

Effdon Networks has demonstrated a 100 Gigabit CFP module with an 80km reach; a claimed industry first. The company has also developed the Qbox, a 1 rack unit (1RU) extended reach platform capable of 400-800 Gigabit-per-second (Gbps) with a reach of 80-200km.

Effdon's CFP does not require the use of external DWDM multiplexing/ demultiplexing and can be added directly onto a router. Source: Effdon Networks

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NeoPhotonics' PIC transceiver tackles PON business case

Gazettabyte completes its summary of optical announcements at ECOC, held in Amsterdam. In the third and final part, NeoPhotonics’ GPON multiport transceiver is detailed.

Part 3: NeoPhotonics

“Anything that can be done to get high utilisation of your equipment, which represents your up-front investment, helps the business case"

Chris Pfistner, NeoPhotonics  

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Does Cisco Systems' CPAK module threaten the CFP2?

Cisco Systems has been detailing over recent months its upcoming proprietary optical module dubbed CPAK. The development promises to reduce the market opportunity for the CFP2 multi-source agreement (MSA) and has caused some disquiet in the industry.

Source: Cisco Systems, Gazettabyte, see comments

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The CFP2 pluggable module gains industry momentum

Finisar and Oclaro unveiled their first CFP2 optical transceiver products at the recent ECOC exhibition in Amsterdam. JDSU also announced that its ONT-100G test equipment now supports the latest 100Gbps module form factor.

Source: Oclaro

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