More than 3.4 billion people are connected to the Internet, placing an ever-increasing demand on the telecom industry to provide bigger, better and faster bandwidth to users. Most of the data for the Internet travel on fiber-optic cables, which are made up of bundles of threads that transmit laser light. As the fiber gets longer, however, power is lost due to attenuation. In the late 1980s and early '90s, researchers discovered that they could mitigate this loss by developing inline fiber-optic amplifiers.
At the time, lasers operated at a wavelength of 1.3 microns, or 1,300 nanometers (nm). No optical amplifiers were developed, however, that worked well in that region. Researchers were able to develop an amplifier at 1.55 microns, or 1,550 nm, so laser transmission systems were switched to match. At the same time, they discovered that inline optical amplifiers allowed them to amplify many different lasers at one time, a discovery that increased the information carrying capacity of a single optical fiber from 155 megabits a second to more than one terabit a second. While this was a huge increase, it is still a limited amount of information, requiring many cables to transmit.
Lawrence Livermore National Laboratory (LLNL) researchers have taken an important step in addressing that need by developing a new type of optical fiber amplifier that could potentially double the information-carrying capacity of fiber-optic cables.
Lawrence Livermore researchers are the first to successfully develop a practical fiber-optic amplifier that generates significant optical gain from 1,390 nanometers (nm) to 1,460 nm with relatively good efficiency. This discovery enables the potential for installed optical fibers to operate in an untapped spectral region known as the E-band, in addition to the C- and L-bands where they currently operate -- effectively doubling a single optical fiber's information-carrying potential.
LLNL’s new amplifier design is based on a novel Neodymium-doped microstructured optical fiber that is tailored to preferentially enhance optical signal gain in the E-band while effectively suppressing competing gain in other spectral bands. The new amplifier design is built around the same architecture as current conventional erbium-doped fiber amplifiers. The new amplifier can easily be converted to a fiber laser operating over the same wavelength range.
Installation of new cable is expensive; a service provider must not only purchase new cables, but also undergo the large expense of digging trenches to install the new cable.
LLNL's new amplifiers would potentially allow telecom companies to more advantageously leverage their installed base of equipment, requiring less capital investment than new cable -- resulting in expanded bandwidth and lower costs for their customer base.
Technical and economic advantages of LLNL's Neodymium-doped Fiber Amplifier technology include:
- opens up a new telecom transmission band that is compatible with existing infrastructure
- enables increasing the data transmission capacity of optical fiber networks without having to install new fiber
- operates in a spectral band that is sufficiently separated from existing C- and L-bands enabling simple, inexpensive provisioning at substations for independent amplification and routing
- no other practical fiber amplifier solutions exist in this spectral range which is still in the low loss window for most long haul optical fibers
- operates in a spectral band sufficiently far from the current C- and L-bands to minimize non-linear interactions
- the Neodymium-doped fiber amplifier is very similar in “look and feel” to conventional Erbium-doped fiber amplifier for easy adoption by the telecom industry
The primary utility of the Neodymium-doped fiber amplifier is in regeneration of telecommunication signals in the wavelength range from 1,390 – 1,460 nm. The Neodymium amplifier can also be converted to a laser operating over the same spectral range.
The LLNL Neodymium-doped fiber amplifier has the same architecture as conventional fiber amplifiers already widely deployed. Instead of having to lay more cable, these new amplifiers could be installed in the same buildings as the current amplifiers, resulting in twice as much bandwidth on current cables.
LLNL's proprietary Neodymium-doped Fiber Amplifier and Laser technology is described in U.S. Patent Application No. 15/288,810 – Nd3+ Fiber Laser and Amplifier.
For further details on the development status see articles "New Horizons for High-Power Fiber Lasers" and "Researchers develop new amplifier that could double the capacity of fiber-optic cables".