Oclaro makes available its EMLs and backs 400G-FR4

Lumentum’s plan to acquire Oclaro for $1.8 billion may have dominated the news at last month’s OFC show held in San Diego, but it was business as usual for Oclaro with its product and strategy announcements.

Adam Carter, chief commercial officer (pictured), positions Oclaro’s announcements in terms of general industry trends. 

“On the line side, everywhere there are 100-gigabit and 200-gigabit wavelengths, you will see that transition to 400 gigabit and 600 gigabit,” he says. “And on the client side, you have 100 gigabit going to 400 gigabit.” 

400G-FR

Oclaro announced it will offer the QSFP56-DD module implementing 400-FR4, the four-wavelength 400-gigabit 2km client-side interface. The 400G-FR4 is a design developed by the 100G Lambda MSA. 

“This [QSFP-DD FR4] will enable our customers, particularly network equipment manufacturers, to drive 400 gigabit up to 36 ports in a one-rack-unit [platform],” says Carter.

Oclaro has had the required optical components - its 53-gigabaud lasers and high-end photo-detectors - for a while. What Oclaro has lacked is the accompanying 4-level pulse amplitude modulation (PAM-4) gearbox chip to take the 8x50 gigabits-per-second electrical signals and encode them into four 50-gigabaud ones.  

The chips have now arrived for testing and if the silicon meets the specs, Oclaro will deliver the first modules to customers later this year.

Oclaro chose the QSFP-DD first as it expects the form factor to sell in higher volumes but it will offer the 400G-FR4 in the OSFP module. 

Certain customers prefer the OSFP, in part because of its greater power-handling capabilities. “Some people believe that the OSFP’s power envelope gives you a little bit more freedom,” he says. “There is still a debate in the industry whether the QSFP-DD will be able to do long-reach [80km data centre interconnect] types of products.” 

Oclaro says its transmit and receive optical sub-assemblies (TOSAs and ROSAs) are designed to fit within the more demanding QSFP-DD such they will also suit the OSFP.  

If people want to buy the [EML] chips and do next-generation designs, they can come to Oclaro

EMLs for sale

Oclaro has decided to sell its electro-absorption modulated lasers (EMLs), capable of 25, 50 and 100-gigabit speeds. 

“If people want to buy the chips and do next-generation designs, they can come to Oclaro for some top-end single-mode chipsets that we have developed for our own use,” says Carter.   

Oclaro's EMLs are used for both coarse wavelength-division multiplexing (CWDM) and the tighter LAN-WDM wavelength grid based client-side interfaces and are available in uncooled and cooled packages. 

Until now the company only sold its 25-gigabit directly modulated lasers (DMLs). “We have been selling [EMLs] strategically to one very large customer who consigns them to a manufacturer,” says Carter. 

The EMLs are being made generally available due to demand. “There are not many manufacturers of this chip in the world,” says Carter, adding that the decision also reflects an evolving climate for business models.

5G and cable

Oclaro claims it is selling the industry’s first 10-gigabit tunable SFP+ operating over industrial temperature (I-temp) ranges: -40 to 85oC. There are two tunable variants spanning 40km and 80km, both supporting up to 96 dense WDM (DWDM) channels on a fibre. The module was first announced at OFC 2017.

Oclaro says cable networks and 5G wireless will require the I-temp tunable SFP+. 

The cable industry’s adoption of a distributed access architecture (DAA) brings fibre closer to the network’s edge and splits part of the functionality of the cable modem termination system (CMTS) - the remote PHY - closer to the residential units. This helps cable operators cope with continual traffic growth and their facilities becoming increasingly congested with equipment. Comcast, for example, says it is seeing an annual growth in downstream traffic (to the home) of 40-50 percent. 

The use of tunable SFP+ modules boost the capacity that can be sent over a fibre, says Carter. But the tunable SFP+ modules are now located at the remote PHY, an uncontrolled temperature environment.   

For 5G, the 10Gbps tunables will carry antenna traffic to centralised base stations. Carter points out that the 40km and 80km reach of the tunable SFP+ will not be needed in all geographies but in China, for example, the goal is to limit the number of central offices such that the distances are greater.

Oclaro also offers an I-temp fixed-wavelength 25-gigabit SFP28 LR module. “It is lower cost than the tunable SFP+ so if you need 10km [for mobile fronthaul], you would tend to go for this transceiver,” says Carter.     

Also unveiled is an optical chip combining a 1310nm distributed feedback laser (DFB) laser and a Mach-Zehnder modulator. “The 1310nm device will be used in certain applications inside the data centre,” says Carter. “There are customers that are looking at using PAM-4 interfaces for short-reach connections between leaf and spine switches.” The device will support 50-gigabit and 100-gigabit PAM-4 wavelengths. 

Line-side optics 

Oclaro announced it is extending its integrated coherent transmitter and integrated coherent receiver to operate in the L-band. The coherent optical devices support a symbol rate of up to 64 gigabaud to enable 400-gigabit and 600-gigabit wavelengths.

Telcos want to use the L-band alongside the C-band to effectively double the capacity of a fibre.

Also announced by Oclaro at OFC was a high-bandwidth co-packaged modulator driver, an indium phosphide-based Mach-Zehnder modulator.

Oclaro was part of the main news story at last year’s OFC when Ciena announced it would share its 400-gigabit WaveLogic Ai coherent digital signal processor (DSP) with three module makers: Oclaro, Lumentum and NeoPhotonics. Yet there was no Oclaro announcement at this year’s OFC regarding the transponder.

Carter says the WaveLogic Ai transponder is sampling and that it has been demonstrated to customers and used in several field trials: “It is still early right now with regard volume deployments so there is nothing to announce yet."