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Calient uses its optical switch to boost data centre efficiency  

For Calient Technologies, an approach by one of the world’s largest data centre operators changed the company’s direction.

The company had been selling its 320x320 non-blocking optical circuit switch (OCS) for applications such as submarine cable landing sites and for government intelligence. Then, five years ago, a large internet content provider contacted Calient, saying it had figured out exactly where Calient’s OCS could play a role in the data centre.


This solution could deliver a significant percentage-utilisation improvement

Daniel Tardent



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PMC advances OTN with 400 Gigabit processor

Optical modules for the line-side are moving beyond 100 Gigabits to 200 Gigabit and now 400 Gigabit transmission rates. Such designs are possible thanks to compact photonics designs and coherent DSP-ASICs implemented using advanced CMOS processes. 


An example switching application showing different configurations of the DIGi-G4 OTN processor on the line cards. Source: PMC

For engineers, the advent of higher-speed line-side interfaces sets them new challenges when designing the line cards for optical networking equipment. In particular, the framer silicon that interfaces to the coherent DSP-ASIC, on the far side of the optics, must cope with a doubling and quadrupling of traffic.  

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Heading off the capacity crunch

Feature - Part 1: Capacity limits and remedies

Improving optical transmission capacity to keep pace with the growth in IP traffic is getting trickier. 

Engineers are being taxed in the design decisions they must make to support a growing list of speeds and data modulation schemes. There is also a fissure emerging in the equipment and components needed to address the diverging needs of long-haul and metro networks. As a result, far greater flexibility is needed, with designers looking to elastic or flexible optical networking where data rates and reach can be adapted as required.

Figure 1: The green line is the non-linear Shannon limit, above which transmission is not possible. The chart shows how more bits can be sent in a 50 GHz channel as the optical signal to noise ratio (OSNR) is increased. The blue dots closest to the green line represent the performance of the WaveLogic 3, Ciena's latest DSP-ASIC family. Source: Ciena.

But perhaps the biggest challenge is only just looming. Because optical networking engineers have been so successful in squeezing information down a fibre, their scope to send additional data in future is diminishing. Simply put, it is becoming harder to put more information on the fibre as the Shannon limit, as defined by information theory, is approached.

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Acacia unveils 400 Gigabit coherent transceiver

  • The AC-400 5x7 inch MSA transceiver is a dual-carrier design
  • Modulation formats supported include PM-QPSK, PM-8-QAM and PM-16-QAM
  • Acacia’s DSP-ASIC is a 1.3 billion transistor dual-core chip 

Acacia Communications has unveiled the industry's first flexible rate transceiver in a 5x7-inch MSA form factor that is capable of up to 400 Gigabit transmission rates. The company made the announcement at the OFC show held in Los Angeles. 

Dubbed the AC-400, the transceiver supports 200, 300 and 400 Gigabit rates and includes two silicon photonics chips, each implementing single-carrier optical transmission, and a coherent DSP-ASIC. Acacia designs its own silicon photonics and DSP-ASIC ICs.

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Ciena's Tom Mock reflects on a career in telecom

It has been a strange week for Tom Mock. Not only is it his last at Ciena, after working for the company for 18 years, it has also been abnormally quiet since many of his colleagues are away at the OFC show in Los Angeles. 

Working for one technology company for so long may be uncommon, says Mock, but not at Ciena: the CTO has clocked 20 years while the CEO boasts 15 years. 


Tom Mock: “I’m about ready to go do something else.”

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OIF shows 56G electrical interfaces & CFP2-ACO 

The Optical Internetworking Forum (OIF) is using the OFC exhibition taking place in Los Angeles this week to showcase the first electrical interfaces running at 56 Gigabit. Coherent optics in a CFP2 pluggable module is also being demonstrated.


“The most important thing for everyone is power consumption on the line card”

The OIF - an industry organisation comprising communications service providers, internet content providers, system vendors and component companies - is developing the next common electrical interface (CEI) specifications, as well as continuing to advance fixed and pluggable optical module specifications for coherent transmission including the pluggable CFP2.

“These are major milestones that the [demonstration] efforts are even taking place,” says Nathan Tracy, technologist at TE Connectivity and the OIF technical committee chair.

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MultiPhy readies 100 Gigabit serial direct-detection chip

MultiPhy is developing a chip that will support serial 100 Gigabit-per-second (Gbps) transmission using 25 Gig optical components. The device will enable short reach links within the data centre and up to 80km point-to-point links for data centre interconnect. The fabless chip company expects to have first samples of the chip, dubbed FlexPhy, by year-end.

Figure 1: A block diagram of the 100 Gig serial FlexPhy. The transmitter output is an electrical signal that is fed to the optics. Equally, the input to the receive path is an electrical signal generated by the receiver optics. Source: Gazettabyte

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