OFC/NFOEC Press Releases

Technical Research News Summaries

Below are news summaries from some of the key technical research taking place at this year’s OFC/NFOEC conference. For technical papers, contact the media team at media@ofcconference.org.

FASTEST FIELD TEST EVER FOR LIVE VIDEO STREAMING
Demand for video streaming over the Internet is expected to grow rapidly in the next few years. As it does, one important question will be how the existing network infrastructure will adapt to handle the increased traffic. Currently, the standard speed for high-speed Internet transmission over existing lines is 10 Gigabits per second (Gb/s), though Verizon is moving to a new standard that will allow 40 Gb/s rates. As video over the Web and other high-bandwidth applications become increasingly popular, however, transmission rates of 100 Gb/s or greater will be needed.

Last November, a team of scientists led by T. J. Xia of Verizon and P. J. Winzer of Alcatel-Lucent’s Bell Labs successfully showed in a live trial that existing optical networks can be upgraded to carry these higher transmission rates. They used an advanced modulation format called DQPSK to stream video at a rate of 107 Gb/s. A number of laboratories have achieved 100 Gb/s Ethernet transmission under ideal conditions but this was the first time that a live 100Gb/s transmission had been sent in the field. What was also unique was that Verizon did not require a wholesale upgrade of equipment for this trial but rather used its existing optical networking equipment.

In several talks at the meeting, Xia, Winzer, and their colleagues will discuss how the team streamed a live HDTV video feed from Tampa, Fla., to Miami, some 300 miles away. Several of Verizon’s senior vice presidents came to the Miami central office to witness this milestone. What channels were watched during this historic moment? High-definition channels HDNet and the Discovery Channel.

• Talk NMC2, “Transmission of 107Gb/s DQPSK over Verizon 504-km Commercial LambdaXtreme® Transport System” (2:10 p.m. Monday, Feb. 25 in room 9).
  
  
• Talk OMQ4, “107-Gb/s Transmission over 700 km and One Intermediate ROADM Using LambdaXtreme® Transport System” (5 p.m. Monday, Feb. 25 in room 6B).
  
  
• Talk OTuG1 “100 Gb/s Challenges and Solutions (tutorial)” (2 p.m. Tuesday, Feb. 26 in room 6F).

INTEL DEVELOPS SILICON-BASED PHOTODETECTORS, ADDRESSES “DARK CURRENT”
Utilizing technology from current high-volume complementary metal-oxide semiconductor (CMOS) computer chips, Intel has developed silicon-germanium (Si-Ge) photodetectors – the devices that convert optical signals into electronic ones for communications – capable of performance similar to that of today's mainstream photodetectors used in 40 Gb/s optical networks. Most photodetectors used in networks today are based on gallium arsenide or indium phosphide, semiconducting compounds that are relatively scarce and expensive to produce compared to silicon, the second most abundant element on Earth and the foundational input of the mass market chip industry. Introducing silicon photodetectors to communications systems would take advantage of the composition of silicon chips themselves, leading to more efficient and less costly data transmission.

Intel’s new high-bandwidth photodetectors are extremely sensitive to light with a wavelength of 1,550 nanometers, which is a standard in the photonics industry. And perhaps more critically, the Intel photodetectors, which represent the latest manifestations of a 25-year effort by optics researchers to develop commercially viable Si-Ge technology, address the problem of dark current, the relatively small current that's present even when no photons are striking the device. Separating useful information from the electrical noise associated with dark current, a consequence of irregularities between the Ge and Si layers of the device, has been the single biggest stumbling block to widespread use of Si-Ge-based photodetectors. Dark current in the new devices is negligible, measuring just a few hundred nanoamperes, or one billionth of an ampere.

Beyond their potential in today's high-speed communication networks, Intel's Si-Ge-based photodetectors might someday serve as the optical interconnects between chips in PCs and servers, taking advantage of the same high-volume manufacturing processes that companies use to produce microprocessors and chipsets. Tao Yin of Intel will announce details of this work at the OFC meeting. Talk OMK2, "40Gb/s Ge-on-SOI waveguide photodetectors by selective Ge growth" (1:45 p.m. Monday, Feb. 25 in room 6D) 

GROWING ON-CHIP MICRORESONATORS
For years chip manufacturers building photonic integrated circuits (PICs) have lacked a good analog to what those working with electronic circuits have in the multi-purpose transistor, which can be used for everything from switching to amplification to impedance transformation. Now, new research from Dan Dapkus and his colleagues at the University of Southern California suggests that PIC-integrated microresonators might fill that gap.

Microresonators, a class of devices that naturally oscillate at certain frequencies, have previously been used to build lasers, modulators and other functional components for photonic circuits. Today, most of these components are first assembled by the vast microelectronics and photonics packaging industry based in low-cost labor markets outside of the United States and Western Europe and then later inserted into optical networks or systems. Dapkus and his colleagues have advanced their earlier work to essentially “grow” microresonators on top of a chip's underlying waveguides via an epitaxial process that could someday be used by PIC manufacturers.

The work suggests that these manufacturers might be able to achieve higher levels of component integration and thus blunt some of their need for low-cost offshore packaging vendors. Dapkus says his successful on-PIC integration of the micron-dimension devices could also bring more transistor-like versatility to microresonators, allowing them add time delay or phase control functionality to photonics chips. Talk OWQ2, "Microresonators for Photonic Integrated Circuits" (4p.m. Wednesday, Feb. 27 in room 6C).

OPTICAL BUFFER
The traditional electrical routers that connect the Internet already use tremendous amounts of power, and as the need for bandwidth increases, so will the power consumption and size of these routers. A promising solution is the use of optical routers to eliminate the conversions between the optical and electrical domains and to allow data to pass through transparently. One of the biggest challenges and controversies is to find an optical equivalent of electrical memory.

The first compact optical buffer able to store reasonable packet lengths of 40 bytes has been demonstrated by Emily Burmeister and her colleagues in the Electrical and Computer Engineering Department of the University of California at Santa Barbara. In her talk, OWE4, "SOA Gate Array Recirculating Buffer for Optical Packet Switching" (9:30 a.m., Wednesday, Feb. 27 in room 6E), Burmeister will discuss the details of the recirculating buffer experimental results.