5x7 inch MSA Archives

OFC 2015 digest: Part 1

A survey of some of the key developments at the OFC 2015 show held recently in Los Angeles.

Part 1: Line-side component and module developments

Several vendors announced CFP2 analogue coherent optics
5x7-inch coherent MSAs: from 40 Gig submarine and ultra-long haul to 400 Gig metro
Dual micro-ITLAs, dual modulators and dual ICRs as vendors prepare for 400 Gig
WDM-PON demonstration from ADVA Optical Networking and Oclaro
More compact and modular ROADM building blocks

Coherent optics within a CFP2

Integrating line-side coherent optics into ever smaller pluggable modules promises higher-capacity line cards and transport platforms. Until now, the main pluggable module for coherent optical transmission has been the CFP but at OFC several optical module companies announced coherent optics that fit within the CFP2 module, dubbed CFP2 analogue coherent optics (CFP2-ACO).

Oclaro, Finisar, Fujitsu Optical Components and JDSU all announced CFP2-ACO designs, capable of 100 Gigabit-per-second (Gbps) line rates using polarisation-multiplexing, quadrature phase-shift keying (PM-QPSK) and 200 Gbps transmission using polarisation-multiplexing, 16-quadrature amplitude modulation (PM-16-QAM).

Unlike the CFP, the CFP2-ACO module houses the photonics for coherent transmission; the accompanying coherent DSP-ASIC resides on the line card. The CFP2’s 12W power consumption is insufficient to house the combined power consumption of the optics and current DSP-ASIC designs.

With the advent of the CFP2-ACO, five or even six modules can be fitted on a line card. “With five CFP2s, if you do 100 Gigabit, you have a 500 Gigabit line card, but if you can do 200 Gigabit using 16-QAM, you have a one terabit line card,” says Robert Blum, director of strategic marketing at Oclaro.

Such line cards can be used not just for metro and regional networks but for the emerging data centre interconnect market, says Blum. Using line-side pluggables also allows operators to add capacity as required.

Oclaro says its CFP2-ACO module has been shown to work with seven different DSP-ASICs; five developed by the system vendors and two merchant chips, from ClariPhy and NEL.

Oclaro uses a single high-output power narrow line-width laser for its CFP2-ACO. The bulk of the laser’s light is used for the transmitter path but some of the light is split off and used for the local oscillator in the receive path. This saves the cost of using a separate, second laser but requires that the transmit and receive paths operate on a common wavelength.

In contrast, Finisar uses two lasers for its CFP2-ACO: one for the transmit path and one for the local oscillator source. This allows independent transmit and receive wavelengths, and uses all the laser’s output power for transmission. Rafik Ward, Finisar’s vice president of marketing says the company has invested significantly to develop its CFP2-ACO, and using it own in-house components. Finisar acquired indium phosphide specialist u2t Photonics in 2014 specifically to address the CFP2-ACO design.

At OFC, fabless chip maker ClariPhy announced a CFP2-ACO reference design card. The design uses the company’s flagship CL20010 DSP-ASIC with a CFP2 cage into which various vendors’ CFP2-ACO modules can be inserted. The CL20010 DSP supports 100 Gbps and 200 Gbps data rates.

“Every major CFP2 module maker is sampling [a CFP2-ACO],” says Paul Voois, co-founder and chief strategy officer at ClariPhy. Having coherent optics integrated into a CFP2 is a real game-changer, he says. Not only will the CFP2-ACO enable one terabit line cards, but the associated miniaturisation of the optics will lower the cost of coherent transmission.

“The DSP’s cost will decline [with volumes] and so will the optics which account for two thirds of the transponder cost,” says Voois. Having a CFP2-ACO multi-source agreement (MSA) also promotes interoperability, further spurring the CFP2-ACO’s adoption, he says.

NeoPhotonics announced a micro integrated coherent receiver (micro-ICR) for the CFP2-ACO. NeoPhotonics all but confirmed it will also supply a CFP2-ACO module. “That would be a logical assumption given that we have all the pieces,” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.

5x7-inch MSAs: 40 to 400 Gig

Work continues to advance the line-side reach and line-speed capabilities of the fixed 5x7-inch MSA module.

Acacia Communications announced a 5x7-inch coherent transponder that supports two carriers, each capable of carrying 100, 150 or 200 Gigabit of data. The Acacia design uses two of the company’s silicon photonics chips, one for each carrier, coupled with Acacia’s DSP-ASIC.

Finisar announced two 5x7 inch MSAs: one capable of 100 Gigabit and 200 Gigabit and one tailored for submarine and ultra long-haul applications using 40 Gig or 50 Gig binary phase-shift keying (PM-BPSK).

Finisar claims it offers the industry’s broadest 200 Gigabit optical module portfolio with its 5x7 inch MSA and its CFP2-ACO. It demonstrated its 5x7-inch MSA also working with its CFP2-ACO at OFC. For the demonstration, Finisar used its CFP2-ACO module plugged into ClariPhy’s reference design.

Micro-ITLAs, modulators and micro-ICRs go parallel

Oclaro announced a dual micro-ITLA suited for two-carrier signals for a 400 Gig super-channel, with each carrier using PM-16-QAM.

“People are designing discrete line cards using micro-ITLAs, lithium niobate modulators and coherent receivers for 400 Gig, for example, and they need two lasers, one for each channel,” says Oclaro’s Blum. This is the main application Oclaro is seeing for the design, but another use of the dual micro-ITLA is for networks where the receive wavelength is different to the transmitter one. “For that, you need a local oscillator that you tune independently,” says Blum.

JDSU also showed a dual-carrier coherent lithium niobate modulator capable of 400 Gig for long-reach applications. The company is also sampling a dual 100 Gig micro-ICR also for multiple sub-channel applications.

Avago announced a micro-ITLA device using its external cavity laser that has a line-width less than 100kHz. The micro-ITLA is suited for 100 Gig PM-QPSK and 200 Gig 16-QAM modulation formats and supports a flex-grid or gridless architecture.

Tunable SFP+

Oclaro announced a second-generation tunable SFP that has a power consumption below 1.5W, meeting the SFP MSA. The tunable SFP also operates over an extended temperature range of up to 85oC, but here the power consumption rises to 1.8W.

“We see a lot of applications that need these higher temperatures: racks running hot, WDM-PON and wireless front-hauling,” says Blum. Wireless fronthaul typically uses grey optics to carry the radio-head traffic sent to the wireless baseband unit. But operators are looking to WDM technology as a way to aggregate traffic and this is where the extended temperature tunable SFP+ can play a role, says Blum.

WDM-PON demonstration

ADVA Optical Networking and Oclaro demonstrated a WDM-PON prototype at OFC. WDM-PON has been spoken of for over a decade as the ultimate optical access technology, delivering dedicated wavelengths to premises. More recently, WDM-PON has been deployed to deliver business services and is being viewed for mobile backhaul and fronthaul applications.

The ADVA-Oclaro WDM-PON demonstration is a 40-wavelength system using the C- and L-bands. The system’s 10 Gigabit wavelengths are implemented using tunable SFP+ modules at the customer’s site.

The difference between Oclaro’s second-generation tunable SFP+ and the WDM-PON demonstration is that the latter module does not use a wavelength locker. Instead, a centralised wavelength controller is used to monitor all 40 channels and sends information back to the customer premise equipment via the L-band if a particular wavelength has drifted and needs adjustment. “We can get away with a very low-cost tunable laser in the customer premises [using this approach],” says Blum.

ROADM building blocks

JDSU showcased its latest ROADM line cards at OFC. These included its second-generation twin 1x20 wavelength-selective switch (WSS), part of its TrueFlex Super Transport blade, and its TrueFlex Multicast Switch blade that features a twin 4x16 multicast switch and a 4+4 array of amplifiers.

JDSU’s first-generation twin 1x20 WSS required more than two slots in a chassis; two slots for the twin WSS and another for amplification and optical channel monitoring. JDSU can now fit all the functions on one blade with its latest design.

The 4x16 multicast switch supports a four-degree (four directions) ROADM and 16 drop or add ports. The twin multicast switch design is used for multiplexing and demultiplexing of wavelengths. “This size multicast switch needs an amplifier on each of those four ports,” says Brandon Collings, CTO for communications and commercial optical products at JDSU. The 4+4 array of amplifiers is for the multicast switch multiplexing and the demultiplexing, “four amps on the mux side of the multicast switch and four amps for the demux side of the multicast switch”, says Collings.

NeoPhotonics announced a modular 4x16 multicast switch which it claims does not need drop amplifiers.

Being modular, operators can grow their systems based on demand, avoiding up-front costs and having to predict the ultimate size of the ROADM node. For example by adding multicast switches they can go from 4x16, 8x16, 12x16 to a full 16x16 switch configuration. “Carriers do not like to have to plan in advance, and they like to be future-proofed,” says Lipscomb.

The NeoPhotonics multicast switch uses planar lightwave circuit (PLC) technology and has a broadcast-and-select architecture. As such, the architecture uses optical splitters which inevitably introduce signal loss. By concentrating on reducing switch loss and by increasing the sensitivity of the integrated coherent receiver, NeoPhotonics claims it can do away with the drop amplifiers for metro networks and even for certain long-haul routes. This can save up to a $1,000 a switch, says Lipscomb.

NeoPhotonics’ multicast switch has already been designed on a line card and introduced into a customer’s platform. It is now undergoing qualification before being made generally available.

ROADM status

“This type of stuff [advanced WSSes and multicast switches for ROADMs] is what Verizon has been pushing for all these years,” says JDSU’s Collings. “These developments have been completed because operators like Verizon are getting serious.” Earlier this year, Verizon selected Ciena and Cisco Systems as the equipment suppliers for its large metro contract.

Some analysts argue that it is largely Verizon promoting advanced ROADM usage and that the rest of the industry is less keen. Collings points out that JDSU, being a blade supplier and not a system vendor, is one customer layer removed from the operators. But he argues that other operators besides Verizon also want to deploy advanced ROADM technology but that two milestones must be overcome first.

“People are waiting to see the technology mature and Verizon really do it,” he says. “[Their attitude is:] Let Verizon run headlong into that, and let’s see how they fare before we invest.” Collings says that until now, ROADM hardware has not been sufficiently mature: “Even Verizon has had to wait to start deploying this stuff.”

The second milestone is having a control plane to manage the systems’ flexibility and dynamic nature. This is where the system vendors have focused their efforts in the past year, convincing operators that the hardware and the control plane are up and running, he says.

“There is lots of interest [in advanced ROADMs] from a variety of carriers globally,” says Collings. “But they have been waiting for these two shoes to drop.”

For Part 2, click here

by Michael

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.

"The ASIC continues to drive performance while the optics continues to drive cost leadership," says Raj Shanmugaraj, Acacia's president and CEO.

The AC-400 uses several modulation formats that offer various capacity-reach options. The dual-carrier transceiver supports 200 Gig using polarisation multiplexing, quadrature phase-shift keying (PM-QPSK) and 400 Gig using 16-quadrature amplitude modulation (PM-16-QAM). The 16-QAM option is used primarily for data centre interconnect for distances up to a few hundred kilometers, says Benny Mikkelsen, co-founder and CTO of Acacia: "16-QAM provides the lowest cost-per-bit but goes shorter distances than QPSK."

Acacia has also implemented a third, intermediate format - PM-8-QAM - that improves reach compared to 16-QAM but encodes three bits per symbol (a total of 300 Gig) instead of 16-QAM's four bits (400 Gig). "8-QAM is a great compromise between 16-QAM and QPSK," says Mikkelsen. "It supports regional and even long-haul distances but with 50 percent higher capacity than QPSK." Acacia says one of its customer will use PM-8-QAM for a 10,000 km submarine cable application.

Source: Gazettabyte

Other AC-400 transceiver features include OTN framing and forward error correction. The OTN framing can carry 100 Gigabit Ethernet and OTU4 signals as well as the newer OTUc1 format that allows client signals to be synchronised such that a 400 Gigabit flow from a router port can be carried, for example. The FEC options include a 15 percent overhead code for metro and a 25 percent overhead code for submarine applications.

The 28 nm CMOS DSP-ASIC features two cores to process the dual-carrier signals. According to Acacia, its customers claim the DSP-ASIC has a power consumption less than half that of its competitors. The ASIC used for Acacia’s AC-100 CFP pluggable transceiver announced a year ago consumes 12-15W and is the basis of its latest DSP design, suggesting an overall power consumption of 25 to 30+ Watts. Acacia has not provided power consumption figures and points out that since the device implements multiple modes, the power consumption varies.

The AC-400 uses two silicon photonics chips, one for each carrier. The design, Acacia's second generation photonic integrated circuit (PIC), has a reduced insertion loss such that it can now achieve submarine transmission reaches. "Its performance is on a par with lithium niobate [modulators]," says Mikkelsen.

It has been surprising to us, and probably even more surprising to our customers, how well silicon photonics is performing

The PIC’s basic optical building blocks - the modulators and the photo-detectors - have not been changed from the first-generation design. What has been improved is how light enters and exits the PIC, thereby reducing the coupling loss. The latest PIC has the same pin-out and fits in the same gold box as the first-generation design. "It has been surprising to us, and probably even more surprising to our customers, how well silicon photonics is performing," says Mikkelsen.

Acacia has not tried to integrate the two wavelength circuits on one PIC. "At this point we don't see a lot of cost savings doing that," says Mikkelsen. "Will we do that at some point in future? I don't know." Since there needs to be an ASIC associated with each channel, there is little benefit in having a highly integrated PIC followed by several discrete DSP-ASICs, one per channel.

The start-up now offers several optical module products. Its original 5x7 inch AC-100 MSA for long-haul applications is used by over 10 customers, while it has two 5x7 inch modules for submarine operating at 40 Gig and 100 Gig are used by two of the largest submarine network operators. Its more recent AC-100 CFP has been adopted by over 15 customers. These include most of the tier 1 carriers, says Acacia, and some content service providers. The AC-100 CFP has also been demonstrated working with Fujitsu Optical Components's CFP that uses NTT Electronics's DSP-ASIC. Acacia expects to ship 15,000 AC-100 coherent CFPs this year.

Each of the company's module products uses a custom DSP-ASIC such that Acacia has designed five coherent modems in as many years. "This is how we believe we out-compete the competition," says Shanmugaraj.

Meanwhile, Acacia’s coherent AC-400 MSA module is now sampling and will be generally available in the second quarter.

by Michael

ECI Telecom demos 100 Gigabit over 4,600km

4,600km optical transmission over submarine cable
The Tera Santa Consortium, chaired by ECI, will show a 400 Gigabit/ 1 Terabit transceiver prototype in the summer
100 Gigabit direct-detection module on hold as the company eyes new technology developments

"When we started the project it was not clear whether the market would go for 400 Gig or 1 Terabit. Now it seems that the market will start with 400 Gig."

Jimmy Mizrahi, ECI Telecom

ECI Telecom has transmitted a 100 Gigabit signal over 4,600km without signal regeneration. Using Bezeq International's submarine cable between Israel and Italy, ECI sent the 100 Gigabit-per-second (Gbps) signal alongside live traffic. The Apollo optimised multi-layer transport (OMLT) platform was used, featuring a 5x7-inch MSA 100Gbps coherent module with soft-decision, forward error correction (SD-FEC).

"We set a target for the expected [optical] performance with our [module] partner and it was developed accordingly," says Jimmy Mizrahi, head of the optical networking line of business at ECI Telecom. "The [100Gbps] transceiver has superior performance; we have heard that from operators that have tested the module's capabilities and performance."

One geography that ECI serves is the former Soviet Union which has large-span networks and regions of older fibre.

Tera Santa Consortium

ECI used the Bezeq trial to also perform tests as part of the Tera Santa Consortium project involving Israeli optical companies and universities. The project is developing a transponder capable of 400 Gigabit and 1 Terabit rates. The project is funded by seven participating firms and the Israeli Government.

"When we started the project it was not clear whether the market would go for 400 Gig or 1 Terabit,” says Mizrahi. “Now it seems that the market will start with 400 Gig."

The Tera Santa Consortium expects to demonstrate a 1 Terabit prototype in August and is looking to extend the project a further three years.

100 Gigabit direct detection

In 2012 ECI announced it was working with chip company, MultiPhy, to develop a 100 Gigabit direct-detection module. The 100 Gigabit direct detection technology uses 4x28Gbps wavelengths and is a cheaper solution than 100Gbps coherent. The technology is aimed at short reach (up to 80km) links used to connect data centres, for example, and for metro applications.

“We have changed our priorities to speed up the [100Gbps] coherent solution,” says Mizrahi. “It [100Gbps direct detection] is still planned but has a lower priority.”

ECI says it is monitoring alternative technologies coming to market in the next year. “We are taking it slowly because we might jump to new technologies,” says Mizrahi. “The line cards will be ready, the decision will be whether to go for new technologies or for direct detection."

Mizrahi would not list the technologies but hinted they may enable cheaper coherent solutions. Such coherent modules would not need SD-FEC to meet the shorter reach, metro requirements. Such a module could also be pluggable, such as the CFP or even the CFP2, and use indium phosphide-based modulators.

“For certain customers pricing will always be the major issue,” says Mizrahi. “If you have a solution at half the price, they will take it.”

by Michael

Teraxion embraces silicon photonics for its products

Teraxion has become a silicon photonics player with the launch of its compact 40 and 100 Gigabit coherent receivers.

The Canadian optical component company has long been known for its fibre Bragg gratings and tunable dispersion compensation products. But for the last three years it has been developing expertise in silicon photonics and at the recent European Conference on Optical Communications (ECOC) exhibition it announced its first products based on the technology.

"You don't have this [fabless] model for indium phosphide or silica, while an ecosystem is developing around silicon photonics"

Martin Guy, Teraxion

"We are playing mainly in the telecom business, which accounts for 80% of our revenues," says Martin Guy, vice president, product management & technology at Teraxion. "It is clear that our customers are going to more integration and smaller form-factors so we need to follow our customers' requirements."

Teraxion assessed several technologies but chose silicon photonics and the fabless model it supports. "We are using all our optical expertise that we can apply to this material but use a process already developed for the CMOS industry, with the [silicon] wafer made externally," says Guy. "You don't have this [fabless] model for indium phosphide or silica, while an ecosystem is developing around silicon photonics."

The company uses hybrid integration for its coherent receiver products, with silicon implementing the passive optical functions to which the active components are coupled. Teraxion is using externally-supplied photo-detectors which are flip-chipped onto the silicon for its coherent receiver.

"We need to use the best material for the function for this high-end product," says Guy. "Our initial goal is not to have everything integrated in silicon."

Coherent receiver

A coherent receiver comprises two inputs - the received optical signal and the local oscillator - and four balanced receiver outputs. Also included in the design are two polarisation beam splitters and two 90-degree hybrid mixers.

Several companies have launched coherent receiver products. These include CyOpyics, Enablence, NEL, NeoPhotonics, Oclaro and u2t Photonics. Silicon photonics player Kotura has also developed the optical functions for a coherent receiver but has not launched a product.

One benefit of using silicon photonics, says Teraxion, is the compact optical designs it enables.

The Optical Internetworking Forum (OIF) has specified a form factor for the 100 Gigabit-per-second (Gbps) coherent receiver. Teraxion has developed a silicon photonics-based product that matches the OIF's form factor sized 40mmx32mm. This is for technology evaluation purposes rather than a commercial product. "If customers want to evaluate our technology, they need to have a compatible footprint with their design," explains Guy. This is available in prototype form and Teraxion has customers ready to evaluate the product.

Teraxion will come to market with a second 100 Gigabit coherent receiver design that is a third of the size of the OIF's form factor, measuring 23mmx18mm (0.32x the area of the OIF specification). The compact coherent receivers for 40 and 100Gbps will be available in sample form in the first quarter of 2013.

Teraxion's OIF-specification 100 Gig coherent receiver (left) for test purposes and its compact coherent receiver product. Source: Teraxion

"We match the OIF's performance with this design but there are also other key requirements from customers that are not necessarily in the OIF specification," says Guy.

The compact 100Gbps design is of interest to optical module and system vendors but there is no one view in terms of requirements or the desired line-side form-factor that follows the 5x7-inch MSA. Indeed there are some that are interested in developing a 100 Gigabit CFP module for metro applications, says Guy.

Roadmap

Teraxion's roadmap includes further integration of the coherent receiver's design. "We are using hybrid integration but eventually we will look at having the photo-detectors integrated within the material,” says Guy.

The small size of the coherent design means there is scope for additional functionality to be included. Teraxion says that customers are interested in integrating variable optical attenuators (VOAs). The local oscillator is another optical function that can be integrated within the coherent receiver.

In 2005 Teraxion acquired Dicos Technologies, a narrow line-width laser specialist. Teraxion's tunable narrow line-width laser product - a few kiloHertz wide - is available in the lab. "The purpose of this product is not to be deployed on the line card - right now," says Guy. "We believe this type of performance will be required for next-generation 100 Gig, 400 Gig, 1 Terabit coherent communication systems where you will need a very 'clean' local oscillator."

Teraxion is also working on developing a silicon-photonics-based modulator. The company has been exploring integrating Bragg gratings within silicon waveguides for which it has applied for patents. This is several years out, says Guy, but has the potential to enable high-speed modulators suited for short-reach datacom applications.

by Michael

5×7 inch MSA

OFC 2015 digest: Part 1

Acacia unveils 400 Gigabit coherent transceiver

ECI Telecom demos 100 Gigabit over 4,600km

Teraxion embraces silicon photonics for its products