Fujitsu Develops Technology Enabling Real-time Multiple-Point Temperature Measurement

Kawasaki, Japan, April 04, 2008

Fujitsu Laboratories Ltd. announced today the development of a new technology, based on optical fibers, that enables accurate and real-time temperature distribution measurement in large datacenters which have multiple heat sources. Through a single optical fiber, this technology makes it possible to measure simultaneously the temperature of over 10,000 areas in a facility, thereby enabling visibility of temperature distribution in large datacenters. Combining this technology with an air conditioning control system will enable fine-tune air conditioning, allowing for more energy-efficient large-scale data centers.

Background

With mounting concern over global warming resulting from greenhouse-gas emissions, there is a growing awareness of the importance of reducing the energy consumed by air conditioning, which is one cause behind the increasing consumption of energy in recent years. In the IT industry, with increasingly powerful servers, larger systems installations, and expanded operational times, the waste heat generated by data centers has been on a continuous upward slope. Thus, in order to lower both energy costs and CO2 emissions, there is a need for more efficient air-conditioning systems in large datacenters. As part of Fujitsu's Green Policy Innovation⁽¹⁾ initiatives, which seek to help customers reduce their environmental footprint, the company is researching ways to help lower the energy demands of IT systems.

In the past, air-conditioning systems would monitor temperatures at a few specific points and cool the building to a uniform temperature, which could lead to temporary cold spots. To solve this problem requires not only designing more energy-efficient servers and other heat generators, but also fine-grained temperature control based on multiple-point temperature readings in a large facility.

Technological Challenges

Conventional building temperature measurement is executed using semiconductor-based sensors and thermocouple temperature sensors⁽²⁾, which can only measure the temperature at specific points. Because all these systems use power sources and signal lines, multiple-point temperature measurements would entail a proliferation of cables that would be difficult to manage and be expensive. Particularly for mid-sized or large data centers, which have numerous server racks, collecting data from multiple points in real time and flexibly adjusting to equipment changes or the addition or subtraction of server racks in response to changes in operational requirements has been extremely difficult.

As a currently available technology method for multiple-point temperature measurement, there is a method that entails using optical fibers as sensors to measure the strength of Raman scattering light⁽³⁾. However, as this method lacks "position resolution⁽⁴⁾" , it is not suited for temperature measurement of multiple heat sources, and thus it is difficult to accurately measure temperature distribution in large data centers using this method.

Newly Developed Technology

Because the minute Raman scattering light intensity of an infrared laser shining through an optical fiber changes, the optical fiber itself can be used as a way to measure temperature. By improving the position resolution, Fujitsu Laboratories developed a practical method technology for measuring with high accuracy the temperature distribution in large data centers.

Key features of this technology are as follows:

1. By combining the following two technologies, the new technology enables accurate temperature measurement (position resolution of less than 1 meter) of large data centers which have multiple heat sources, such as from severs, within the facility:
   
   • A technology that adjusts variations in measurement that occur, depending on the width of a pulse inserted into an optical fiber, or if the pulse widens during transmission
   • A technology based on thermo-fluid simulation that optimizes the method in which optical fiber is laid
2. As the new technology makes it easy to assess positional information about the point being monitored, it can accommodate changes and updates of server racks.

Results

Because a single strand of optical fiber can measure up to 10,000 locations in real time, large data centers can measure their temperature distribution precisely and inexpensively (assumes optic fiber length of 10 km).

As this system uses only light to take measurements, it imposes no risk of disrupting electrical signals in nearby servers and networking equipment.

Because the system can be used to monitor temperature irregularities of servers and air-conditioning systems in real time, it can help lessen the risk of high temperatures creating fires.

Future Developments

Fujitsu plans to develop this technology for use in air conditioning control systems, as well as complementary technologies to effectively use waste heat, thereby enabling large data centers to consume less energy.