Buzz
An artist's visual representation of NASA's Lunar Laser Communications Demonstration
Image courtesy of NASAWhen lasers were first discovered, they were regarded as a solution seeking a problem. They were as intriguing as Bose-Einstein condensates, yet no one really understood the practical applications of these devices capable of generating a concentrated beam of light.
Today, lasers have evolved into one of the most pivotal technologies globally, finding applications across a wide array of fields, including information technology, telecommunications, healthcare, consumer electronics, law enforcement, military, entertainment, and manufacturing.
From the very beginning of laser research, scientists recognized that light could surpass radio in both speed and information density. This was purely a matter of physics. Light wavelengths are much more tightly packed than sound waves, enabling them to carry more data per second with a stronger signal. Once realized, laser communications would be the bullet train compared to radio's slow-moving wagon train [sources: Hadhazy; Thomsen].
In many ways, lasers have already been used for communication for years. We use lasers daily for tasks like reading CDs and DVDs, scanning barcodes at checkout counters, and tapping into the fiber optic networks that power phone and Internet services. Now, a more direct approach is emerging that will enable high-speed, point-to-point communication over long distances, through air or space, with minimal data loss.
The journey to this point has been long. As far back as 1964, NASA experimented with the idea of using lasers for communication in airplanes. The concept was to convert a pilot's voice into electrical pulses, which would then be turned into a light beam. A receiver on the ground would reverse the process [source: Science News Letter]. In October 2013, NASA surpassed this early vision by successfully transmitting data from a spacecraft orbiting the moon to an Earth station using a pulsed laser beam—covering 239,000 miles (384,600 kilometers) at an unprecedented download rate of 622 megabits per second (Mbps) [source: NASA]. In comparison, typical consumer high-speed data plans are usually measured in tens of megabits.
High-speed and high-density transmission is the new frontier. Throughout much of its history, NASA has faced limitations in exploration due to slow, dial-up-like speeds. With the advent of laser communications, NASA is entering the high-speed era, unlocking the potential for applications such as high-definition video transmission from future rovers.
NASA isn't the only one interested in laser technology. Cryptographers and security experts are turning to lasers as a secure, near-instantaneous method of data transmission, while high-frequency traders on Wall Street are willing to invest heavily in any technology that can cut down on the milliseconds in trade times. Additionally, computer manufacturers, nearing the physical limits of copper and silicon, are exploring potential laser applications as well.
When speed is paramount and light defines the universe's speed limit, lasers are destined to be the solution—if the technology can be made practical.
The Next Best Thing to Being There
The aim of communication technologies is to transmit information quickly, completely, and accurately. If you've ever dined with a rude individual, you understand how little value a stream of noise holds; and if you've ever played the game telephone, you know how meaning can be distorted when the message isn't communicated well.
Historically, the challenges of long-distance communication have only grown. Methods like drum beats, bonfires, smoke signals, flags, or light required the use of a basic code. Telegraph cables and Morse code enabled complex messages to be sent, though at a significant cost, reinforcing the need for brevity in communication.
Modern electronic communication requires a transmitting device that can encode data into a format that can be transmitted, and a receiver capable of distinguishing the message (signal) from the surrounding interference (noise). Information theory, a mathematical framework developed by U.S. engineer Claude Shannon in 1948, provided the foundation for solving this issue, ultimately enabling technologies like cell phones, the Internet, and modems to become a reality [source: National Geographic].
In essence, laser communication systems function similarly to the modems that have been in use in our homes since the advent of the Internet. The term 'modem' stands for MODulation-DEModulation, a process in which digital data is converted to analog for transmission and then back to digital at the receiving end. Early acoustic modems employed sound waves to transmit data over phone lines, while optical modems shift from sound to the higher frequency light spectrum.
This is not a completely new idea. Audiovisual devices equipped with optical audio, like many DVD players, utilize a modem-like component known as a transmission module to convert digital signals into LED or laser light. This light travels through fiber optic cables to components such as a television or audio receiver. There, a light reception module converts the light back into a digital electrical signal, which is then suitable for speakers or headphones.
NASA's proof-of-concept Lunar Laser Communication Demonstration (LLCD), created by MIT's Lincoln Laboratory, operates on a similar principle but replaces fiber optics with laser transmission through air and space (often referred to as free-space optical communication, or FSO). The LLCD system includes three main components:
- A modem module (MM)
- An optical module (OM), which transmits and receives modulated laser beams via a 4-inch (10-centimeter) telescope
- A controller electronics (CE) module that connects the first two components and also links the LLCD to NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE). This module manages critical tasks such as sequencing, stabilization, and relaying commands and telemetry [sources: Britannica; NASA; NASA].
With the successful outcome of this experiment, the future of laser communications has brightened considerably. But is there a potential market for this technology outside of the space agency? Absolutely.
Fiber optics, first made viable by British physicist Harold Hopkins in 1952, gradually replaced electronic cable as the technology evolved, with more precisely tunable lasers and superior quality fiber. Today, it stands as the preferred technology for communications — at least until FSO communication becomes more efficient and practical. The technology, which uses light pulses traveling through internally reflective glass or plastic cables, can transmit more data per second, over longer distances, and without signal loss, compared to electric pulses over copper wires [source: National Geographic; Thomsen].
Laser Communication Applications: From Outer Space to Wall Street
Laser communications may prove invaluable for space exploration, but it is more earthly industries that will determine its success as a commercial technology.
Consider, for instance, the rising group of high-speed traders on Wall Street who harness the power of quantitative analysis, ultra-fast broadband, and a multitude of microtransactions to generate profits one fraction of a penny at a time. In a world driven by "robo-traders" — computer algorithms executing trades in milliseconds based on predefined rules — transmission time equates to money, and lasers represent the fastest option available [sources: Adler; CBS News; Strasburg].
To maximize the value of each trade, firms like Spread Networks invested in top-tier fiber and eliminated every possible kink and curve in the data pipelines linking trading hubs such as Chicago, New York, London, and Tokyo (with each extra mile adding approximately eight microseconds to the round-trip time). When this wasn't fast enough, other companies, including McKay Brothers and Tradeworx, moved beyond fiber optics to microwave transmission through the air. While microwaves are only slightly faster than radio in terms of power and speed, they move faster through the air than light travels through fiber optics [sources: Adler; Strasburg].
Lasers could potentially achieve the fastest speeds ever recorded; light travels nearly as quickly through air as it does in a vacuum, making it possible to cover the 720 miles (1,160 kilometers) between New York and Chicago in just 3.9 milliseconds — resulting in a round-trip (or latency) of 7.8 milliseconds. This is much quicker than the 13.0-14.5 milliseconds required for the newest fiber optic systems and the 8.5-9.0 milliseconds of microwave transmitters [source: Adler].
In the realm of security, lasers and other optical communication technologies offer enhanced secure communications — but they also introduce the potential for eavesdropping. Quantum cryptography leverages a principle of quantum physics: a third party cannot observe the quantum state of the photonic encryption key without altering it and thus revealing its presence. This allows for the establishment of highly secure communications using beams of photons generated by weakened lasers [sources: Grant; Waks et al.]. In the fall of 2008, researchers in Vienna began exploring a quantum Internet based on this principle [source: Castelvecchi]. Unfortunately, lasers have also been used to intercept and spoof these signals in a non-quantum manner, bypassing detection. Companies working on quantum encryption are addressing this challenge [sources: Dillow; Lydersen et al.].
The main challenges for laser communications within the atmosphere are interference from rain, fog, or pollutants, but these hurdles are unlikely to hinder the progress of the technology given its significant advantages. So, whether literal or figurative, the sky remains the limit for the future of laser communication technologies.
The ability to transmit high-speed data between networks is just the beginning of what laser communications can achieve, many of which stem from the lack of a physical connection. Laser beams can link computer chips inside computers, cross land and roads without needing rights-of-way or ownership, and even be set up as temporary networks during military operations or disaster recovery efforts. They can provide redundancy to networks, connect existing optical infrastructures, or bring us closer to converged voice-data systems — all while maintaining high speeds, low error rates, and resistance to electromagnetic interference [sources: Carter and Muccio; Markoff].
