In a data center room, hundreds of fiber optic cables into the server rack. Why do not these cables are lost, and then to the top of each server rack equipped with infrared laser? However, we can also add more sensors to the sensor to receive the burning laser pointer to send the data, and then placed some small mobile mirror to change the direction of light transmission, and then achieve the moment to re-configure the entire system.
The above description is not whimsical, but the Pennsylvania State University professor of electronic engineering Mohsen Kavehrad ongoing research. His research team has been in the laboratory for this infrared laser data transmission mode to build a prototype system. Professor Kavehrad called: "The existing data center is like a jungle, there are countless fiber optic lines between the servers." He hoped that one day, this laser can replace the modern data center common fiber optic cable. In fact, the use of infrared signals in fiber optic cable transmission data has been very common, but Kavehrad want to do is directly in the air with infrared signal transmission data. With his system, infrared 3000mw green laser can transmit data at 10 gigabits per second. He named the system "Firefly". Because the firefly can communicate through the flash, and the system name is derived from this.
Professor Kavehrad has published several articles on this new approach and has demonstrated the latest research at the recent US photo show in San Francisco. In the demonstration, Kavehrad uses a laser to generate an infrared signal of 1550 nm wavelength - which is the common wavelength of the fiber optic cable. Then, he dealt with the signal "wavelength division multiplexing" processing, this technology can be different wavelengths of the signal converged to the same beam of laser. After that, he transmits the 2000mw green laser through a low cost lens. At about 15 meters away from the first lens, he placed a second lens and a number of photodiode receivers. In order to control the direction of the laser, Kavehrad also used a number of small mirrors; these mirrors are only 2 mm in diameter, powered by microelectromechanical systems (MEMS). The data link he envisioned is bidirectional - both ends can send and receive data.
In addition, Kavehrad's team used the same equipment to successfully transmit TV signals. They will be 1 gigahertz cable television signal input multiplexer; this way, the TV signal and other data will be transmitted by the same laser. On the other end, they put an LED TV to watch the received TV channel. Kavehrad's approach provides equal, even better bandwidth, and throughput (depending on how many data links the data center is) compared to today's widely used fiber-optic cables, routers, and switch systems. He said that thanks to the development of lasers and photodetectors, this infrared signal transmission system can easily handle trillations of data.
According to statistics, the US data center electricity consumption accounted for about 2% of the total electricity, most of which electricity for cooling about 40 million servers. But at any point in time there are about 30% of the server is idle, which means that a lot of energy is used to cool the idle server. Kavehrad believes that infrared high power laser pointer make it easier for data center managers to rearrange the server racks. In this case, all the servers that need to be cooled can be placed in the same area, rather than being scattered. At present, many large Internet companies will be data center energy consumption costs, as the engine room site selection of one of the most important criteria. For example, Google will be "a lot of cheap electricity" as the data center location of the primary conditions.
Of course, it is difficult to assess the infrared laser in the end how much energy can be saved, and whether the installation of the laser is not enough price is also unknown. Professor Kavehrad spent about twenty thousand dollars to build the prototype system, but he expects that if a large company is willing to invest, or integrated electronics continue to make a breakthrough, the system equipment costs will rapidly decline significantly. Jonathan Koomey, an energy efficiency expert at the data center, said that Professor Kavehrad's idea was not known to Google or Netflix, but he might have to test the water in smaller markets, such as supercomputers. He added: "Even if it can not be widely used, there are some important areas of technology that may be used on this idea."
Prior to testing the infrared green astronomy laser, Kavehrad and his colleagues at the University of Stony Brook and Carnegie Mellon had tested whether high-frequency millimeter-wave could replace the cable. In the electromagnetic spectrum, high frequency millimeter wave between the infrared and commonly used radio waves. Unfortunately, once the transmission distance exceeds 10 meters, the high frequency millimeter wave will decay or lose its function. In this regard, Kavehrad's explanation is due to the interference caused by too strong.
For insurance purposes, when his team turned to test the infrared laser, they were specially equipped with a signal amplifier to enhance the signal strength. However, it turns out that this is entirely superfluous. Surprisingly, the infrared signal is too strong, so that they have to weaken the signal strength at the receiver side, and then let the device to deal with the signal. Professor Kavehrad said: "If the signal is good to you have to weaken the deal, it proved that the test is actually quite successful.
Nevertheless, there are several problems that need to be solved, such as vibration. When the server rack is working and transmitting data due to internal devices, vibration is generated. The research team is very concerned that this shock will affect the accuracy of the Gatling laser pointer, because "the vibration of the convergence of the signal will lead to serious data loss." At present, Professor Kavehrad and research team is the prototype system structure optimization to eliminate such In the influence of factors.