A round-up of some of the main announcements and demonstrations at the recent OFC/NFOEC 2012 exhibition and conference.
100 Gigabit coherent
Finisar demonstrated its first 100 Gigabit coherent receiver transponder. The 5x7inch dual-polarisation, quadrature phase-shift keying (DP-QPSK) module complies with the Optical Internetworking Forum's (OIF) multi-source specification. The companies joins Fujitsu Optical Components, Opnext and Oclaro that have already detailed their 100 Gigabit coherent modules. Since OFC/NFOEC, Oclaro and Opnext have announced their intention to merge.
"We can take off-the-shelf DSP technology and match it with vertically-integrated optics and come up with a module that is cost effective while enabling higher density for system vendors," says Rafik Ward, vice president of marketing at Finisar. "This will start the shift away from the system vendors' proprietary line cards."
Opnext announced it has demonstrated interoperability between its OMT-100 100 Gigabit-per-second (Gbps) coherent module and 100 Gigabit systems from Fujitsu Optical Systems and NEC. All three designs use NTT Electronics' (NEL) DSP-ASIC coherent receiver chip. "For those that use the same NEL modem chip, we can interoperate with each other," says Ross Saunders, general manager, next-generation transport for Opnext Subsystems.
They come back to folks like us and say: 'If you can hit this price point, then we will use you'
Ross Saunders, Opnext
Oclaro's MI 8000XM 100Gbps module also uses the NEL DSP-ASIC but was not part of the interoperability test sponsored by Japanese operator, NTT.
Oclaro announced its 100Gbps coherent module is now being manufactured using all its own optical components. These include a micro integrated tunable laser assembly (ITLA) - the latest ratified MSA that is more compact and has a higher output power, its modulator and its coherent receiver module.
Using its components enables the company to control performance-cost tradeoffs, says Per Hansen, vice president of product marketing, optical networks solutions at Oclaro: "This [vertical integration] gives us a flexibility we didn’t have in the past."
Finisar is not saying which merchant DSP-ASIC it is using. But like the NEL device, the DSP-ASIC supports soft-decision forward error correction (SD-FEC) to achieve a reach of over 2,000km.
Meanwhile, the module makers' 100Gbps modules are starting to be shipped to customers.
"We shipped [samples] to four customers last quarter and we are probably going to ship to another four or five by the end of this quarter," says Opnext's Saunders.
Opnext says nearly all of its early customers do not have their own in-house 100Gbps developments. However, the systems vendors that have internal 100Gbps programmes have designed their line cards using the same 168-pin interface. This allows them to replace their own 100Gbps daughter cards with a merchant 5x7-inch module.
"This [vertical integration] gives us a flexibility we didn’t have in the past."
Per Hansen, Oclaro
The company also announced its OTS-100FLX 100Gbps muxponder, transponder and regenerator line cards that use the OTM-100 module and which slot into its OTS-4000 chassis. The chassis supports eight 100Gbps cards. Opnext's smaller 4RU OTS-mini platform hosts two 100Gbps line cards, mounted horizontally. Over half of Opnext's revenues are from subsystems sales which it brands and sells to system vendors.
As for the other 100Gbps transponder makers, Oclaro is sending out its first module samples now. Finisar says its module will be generally available by the year-end, while Fujitsu Optical Components' module was released in April.
Optical components for 200Gbps DP-QPSK
u2t Photonics announced its latest 64Gbaud photo-detector that points to the next speed shift in line-side transmission. The photo-detector is one key building block to the eventual development of a single-carrier DP-QPSK capable of 200Gbps or using 16-QAM, 400Gbps.
"We can already support the higher interface speed and data throughput"
Jens Fiedler, u2t Photonics
"System companies are looking for two things: to increase the baud rate and to use more complex modulation schemes," says Jens Fiedler, vice president sales and marketing at u2t Photonics. "[With this announcement] from the optical component perspective, we can already support the higher interface speed and data throughput."
1x23 Wavelength-selective switch
Oclaro announced a 1x23 wavelength selective switch at OFC. According to Oclaro, the 1x23 WSS has come about due to the operators' desire to support 12-degree nodes: an input port (1 degree) and through-connections on 11 other ports. The remaining 12 [of the WSS's 24 ports] are used as drop ports.
"If for each of those ports you have a fan-out that is steerable to 8 ports, you have 12x8 or 96 as the total channels you can support for a full add-drop," says Hansen. Such a 12-degree, 96-channel requirement was set by operators early on, or at least it was an industry desire, says Hansen.
Switching elements that address these drop requirements - multicast switches - were announced by NeoPhotonics and Enablence Technologies at OFC. The switches, planar lightwave circuit (PLC) hybrid integration designs, implement 8x16 multicast switches.
"The multicast switch takes signals from eight different inputs - 8 different directions in a ROADMs node and distributes those signals to up to 16 drop ports," says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
Such PLC designs are complex, comprising power splitters, waveguide switching, variable optical attenuators and photo-detectors for channel monitoring.
According to NeoPhotonics, the number of optical functions used to implement the multicast switch is in the hundreds.
Enablence already has 8x8 and 8x12 multicast switches and has launched its 8x16 device. Although the company is a hybrid PIC specialist and has PLC technology, it uses polymer PLCs for the multicast designs, claiming they are lower power. NEL is another company offering 8x8 and 8x12 multicast switches.
Passive optical networking
Finisar also demonstrated a mini-PON network, highlighting its optical line terminal (OLT) transceivers, splitters and its latest GPON-stick, an GPON optical network unit built into an SFP. The demo involved using the ONU SFP transceiver in an Ethernet switch port as part of a PON network to deliver high-definition video and audio from the OLT to a high-definition TV.
The company also introduced two splitter products a 1:128 port splitter and a 2:64 (used for redundancy). These high-split ratios are being prepared for the advent of 10 Gigabit PON.
Enablence also demonstrated a WDM-PON 32-channel receiver module at OFC. "It takes 32 TO-can receivers and replaces them with a small module which includes the AWG (arrayed waveguide grating demultiplexer) and the 32 receivers," says Matt Pearson, vice president, technology, optical components division at Enablence Technologies. The design promises to increase system density by fitting two such receivers on a single blade.
Optical engines
Silicon photonics firm, Kotura, detailed its 100Gbps optical engine chip, implemented as a 4x25Gbps design. The optical engine consumes 5W and has a reach of at least 10km, making it suitable for requirements in the data centre including the 100 Gigabit Ethernet IEEE 100GBASE-LR4 standard.
"The 100Gbps chip - 5mmx6mm - is small enough to fit in the QSFP+ and emerging CFP4 optical modules
Arlon Martin, Kotura
Kotura demonstrated to select customers its optical engine. "We are not announcing the product yet," says Arlon Martin, vice president of marketing at Kotura.
Optical engines are used in several applications: pluggable modules on a system's face-plate, the optics at each end of an active optical cable, and for board-mounted embedded applications.
For embedded applications, the optical engine is mounted deeper within the line card, close to high-speed chips, for example, with the signals routed over fibre to the face-plate connector. Using optics rather than high-speed copper traces simplifies the printed circuit board design.Embedded optical engines will also be used for optical backplane-based platforms.
Kotura's silicon photonics-based optical engine integrates all the functions needed for the transmitter and receiver on-chip. These include the 25Gbps optical modulators and drivers, the 4:1 multiplexer and 1:4 demultiplexer and four photo-detectors. To create the lasers, an array of four gain blocks are coupled to the chip. Each of laser's wavelength, around 1550nm, is set using on-chip gratings.
The 100Gbps chip, measuring about 5mmx6mm, is small enough to fit in the QSFP+ and emerging CFP4 optical modules, says Martin. The QSFP+ is likely to be the first application for Kotura's 100Gbps optical engine, used to connect switches within the data centre.
Finisar demonstrated its own VCSEL-based board mount optical assembly - also an optical engine - to highlight the use of the technology for future optical backplanes.
The demonstration, involving Vario-optics and Huber + Suhner, included boards in a chassis. The board includes the optical engine coupled to polymer waveguides from Vario-optics which connect it to a backplane connector, built by Huber + Suhner. "The idea is to show what an integrated optical chassis will look like," says Ward.
Finisar's optical backplane demo using board-mounted optics. Source: Finisar
The optical engine comprises 24 channels - 12 transmitters at 10Gbps and 12 receivers in a single board-mounted package. The optics can operate at 10, 12, 14, 25 and 28Gbps, says Finisar. The connector allows the optical engines on different cards to interface via the waveguides. The advantage of polymer waveguides is that they are relatively easy to etch on printed circuit boards and since they replace fibre, they remove fibre management issues. However the technology needs to be proven before system vendors will use such waveguides as standard in their platforms.
Interconnect specialist Reflex Photonics demonstrated an 8.6Tbps optical backplane at OFC. The demonstrator uses Reflex's LightABLE optical engines to implement 864 point-to-point optical fibre links to achieve 8.6Tbps in a single chassis.
The optical fabric comprises six layers of 12x12 fully connected broadcast meshes. Each line card supports 720Gbps into the optical backplane and 60Gbps direct bandwidth between any two cards.
32G Fibre channel
Finisar also highlighted its 28Gbps VCSEL that will be used for the 32 Gigabit Fibre Channel standard. The actual line rate for 32Gbps Fibre Channel is 28.05Gbps. The VCSEL is packaged into a transmitter optical sub-assembly (TOSA) that fits inside a SFP+ module.
"We view 28Gbps VCSEL as strategic due to all the applications it will enable," says Ward.
Besides 32Gbps Fibre Channel, the high-speed VCSEL is suited for the next Infiniband data rate - enhanced data rate (EDR) at 4x25Gbps or 12x25Gbps. There is also standards work in the IEEE for a new 100Gbps Ethernet standard that can use 4x25Gbps VCSELs.
Further reading:
Gazettabyte's full OFC NFOEC 2012 coverage
LightCounting: Notes from OFC 2012: Onset of the Terabit Age
Ovum's OFC coverage