FREE SPACE OPTICS

Imagine an outdoor wireless technology that offers full-duplex Gigabit Ethernet throughput. A technology that can be installed license-free worldwide, and can be installed in less than a day. A technology that offers a fast, high ROI. That technology is Free Space Optics (FSO). This line-of-sight technology approach uses invisible beams of light to provide optical bandwidth connections. It's capable of sending up to 1.25 Gbps of data, voice, and video communications simultaneously through the air — enabling fiber-optic connectivity without requiring physical fiber-optic cable. It enables optical communications at the speed of light. And it forms the basis of a new category of products — optical wireless products from LightPointe, the recognized leader in outdoor wireless bridging communications. This site is intended to provide valuable background and resource information on FSO technology. Whether you're a student, an engineer, account manager, partner, or customer, this site provides the FSO insight you may require. And for providing high-speed connections, across Enterprises and between cell-site towers, it is the best technology available. FSO is a line-of-sight technology that uses invisible beams of light to provide optical bandwidth connections that can send and receive voice, video, and data information. Today, FSO technology — the foundation of LightPointe's optical wireless offerings — has enabled the development of a new category of outdoor wireless products that can transmit voice, data, and video at bandwidths up to 1.25 Gbps. This optical connectivity doesn't require expensive fiber-optic cable or securing spectrum licenses for radio frequency (RF) solutions. FSO technology requires light. The use of light is a simple concept similar to optical transmissions using fiber-optic cables; the only difference is the medium. Light travels through air faster than it does through glass, so it is fair to classify FSO technology as optical communications at the speed of light.

History of Free Space Optics

Originally developed by the military and NASA, FSO has been used for more than three decades in various forms to provide fast communication links in remote locations. LightPointe has extensive experience in this area: its chief scientists were in the labs developing prototype FSO systems in Germany in the late 1960s, even before the advent of fiber-optic cable. To view a copy of the original FSO white paper in German, published in Berlin, Germany, in the journal Nachrichtentechnik, in June 1968 by Dr. Erhard Kube, LightPointe's Chief Scientist and widely regarded as the "father of FSO technology," click on the link below:

While fiber-optic communications gained worldwide acceptance in the telecommunications industry, FSO communications is still considered relatively new. FSO technology enables bandwidth transmission capabilities that are similar to fiber optics, using similar optical transmitters and receivers and even enabling WDM-like technologies to operate through free space. Read more on the ultra high-speed multi-gigabit wireless laser.

How Free Space Optics / Laser Communications Works
FSO technology is surprisingly simple. It's based on connectivity between FSO-based optical wireless units, each consisting of an optical transceiver with a transmitter and a receiver to provide full-duplex (bi-directional) capability. Each optical wireless unit uses an optical source, plus a lens or telescope that transmits light through the atmosphere to another lens receiving the information. At this point, the receiving lens or telescope connects to a high-sensitivity receiver via optical fiber. This FSO technology approach has a number of advantages: Requires no RF spectrum licensing. Is easily upgradeable, and its open interfaces support equipment from a variety of vendors, which helps enterprises and service providers protect their investment in embedded telecommunications infrastructures. Requires no security software upgrades. Is immune to radio frequency interference or saturation. Can be deployed behind windows, eliminating the need for costly rooftop rights.

Choosing Free Space Optics or Radio Frequency Wireless

Speed of fiber — flexibility of wireless

Optical wireless, based on FSO-technology, is an outdoor wireless product category that provides the speed of fiber, with the flexibility of wireless. It enables optical transmission at speeds of up to 1.25 Gbps and, in the future, is capable of speeds of 10 Gbps using WDM. This is not possible with any fixed wireless or RF technology. Optical wireless also eliminates the need to buy expensive spectrum (it requires no FCC or municipal license approvals worldwide), which further distinguishes it from fixed wireless technologies. Moreover, FSO technology’s narrow beam transmission is typically two meters versus 20 meters and more for traditional, even newer radio-based technologies such as millimeter-wave radio. Optical wireless products' similarities with conventional wired optical solutions enable the seamless integration of access networks with optical core networks and helps to realize the vision of an all-optical network.

Free Space Technology in Communication Networks

Free-space optics technology (FSO) has several applications in communications networks, where a connectivity gap exists between two or more points. FSO technology delivers cost-effective optical wireless connectivity and a faster return on investment (ROI) for Enterprises and Mobile Carriers. With the ever-increasing demand for greater bandwidth by Enterprise and Mobile Carrier subscribers comes a critical need for FSO-based products for a balance of throughput, distance and availability.During the last few years, customer deployments of FSO-based products have grown.Here are some of the primary network uses:

Enterprise
Because of the scalability and flexibility of FSO technology, optical wireless products can be deployed in many enterprise applications including building-to-building connectivity, disaster recovery, network redundancy and temporary connectivity for applications such as data, voice and data, video services, medical imaging, CAD and engineering services, and fixed-line carrier bypass.

Mobile Carrier Backhaul
ing services, and fixed-line carrier bypass. Mobile Carrier Backhaul: FSO technology and optical wireless products can be deployed to provide up to 16xE1/T1 backhaul connectivity and Greenfield mobile networks.

Mobile Carrier Base Station “Hoteling”
FSO-based products can be used to expand Mobile Carrier Network footprints through base station “hoteling” in tandem with ADC’s Digivance™ solution.

Will we hear the light?

University of Utah researchers used invisible infrared light to make rat heart cells contract and toadfish inner-ear cells send signals to the brain. The discovery someday might improve cochlear implants for deafness and lead to devices to restore vision, maintain balance and treat movement disorders like Parkinson's.

"We're going to talk to the brain with optical infrared pulses instead of electrical pulses," which now are used in cochlear implants to provide deaf people with limited hearing, says Richard Rabbitt, a professor of bioengineering and senior author of the heart-cell and inner-ear-cell studies published this month in The Journal of Physiology
The studies � funded by the National Institutes of Health � also raise the possibility of developing cardiac pacemakers that use optical signals rather than electrical signals to stimulate heart cells. But Rabbitt says that because electronic pacemakers work well, "I don't see a market for an optical pacemaker at the present time".

The scientific significance of the studies is the discovery that optical signals � short pulses of an invisible wavelength of infrared laser light delivered via a thin, glass optical fiber � can activate heart cells and inner-ear cells correlation to balance and hearing.

In addition, the research showed infrared activates the heart cells, called cardiomyocytes, by triggering the movement of calcium ions in and out of mitochondria, the organelles or components within cells that convert sugar into usable energy. The same process appears to occur when infrared light stimulates inner-ear cells.

Infrared light can be felt as heat, raising the possibility the heart and ear cells were activated by heat rather than the infrared radiation itself. But Rabbitt and his colleagues did "elegant experiments" to show the cells indeed were activated by the infrared radiation, says a commentary in the journal by Ian Curthoys of the University of Sydney, Australia.

Curthoys writes that the research provides "stunningly bright insight" into events within inner-ear cells and "has great potential for future clinical application."

Shedding Infrared Light on Inner-Ear Cells and Heart Cells.

The low-power infrared light pulses in the study were generated by a diode � "the same thing that's in a laser pointer, just a different wavelength," Rabbitt says.

The researchers exposed the cells to infrared light in the laboratory. The heart cells in the study were newborn rat heart muscle cells called cardiomyocytes, which make the heart pump. The inner-ear cells are hair cells, and came from the inner-ear organ that senses motion of the head. The hair cells came from oyster toadfish, which are well-establish models for comparison with human inner ears and the sense of balance.

Inner-ear hair cells "convert the mechanical vibration from sound, gravity or motion into the signal that goes to the brain" via adjacent nerve cells, says Rabbitt.

Using infrared radiation, "we were stimulating the hair cells, and they dumped neurotransmitter onto the neurons that sent signals to the brain," Rabbitt says.

He believes the inner-ear hair cells are activated by infrared radiation because "they are full of mitochondria, which are a primary target of this wavelength".

The infrared radiation affects the flow of calcium ions in and out of mitochondria � something shown by the companion study in neonatal rat heart cells.

That is important because for "excitable" nerve and muscle cells, "calcium is like the trigger for making these cells contract or release neurotransmitter," says Rabbitt.

The heart cell study observed that an infrared pulse lasting a mere one-5,000th of a second made mitochondria rapidly suck up calcium ions within a cell, then slowly release them back into the cell � a cycle that makes the cell contract.

"Calcium does that normally," says Rabbitt. "But it's normally controlled by the cell, not by us. So the infrared radiation gives us a tool to control the cell. In the case of the [inner-ear] neurons, you are controlling signals going to the brain. In the case of the heart, you are pacing contraction".

New Possibilities for Optical versus Electrical Cochlear Implants
Rabbitt believes the research � including a related study of the cochlea last year � could lead to better cochlear implants that would use optical rather than electrical signals.

Existing cochlear implants convert sound into electrical signals, which typically are transmitted to eight electrodes in the cochlea, a part of the inner ear where sound vibrations are converted to nerve signals to the brain. Eight electrodes can deliver only eight frequencies of sound, Rabbitt says.

"A healthy adult can hear more than 3,000 different frequencies. With optical stimulation, there's a possibility of hearing hundreds or thousands of frequencies instead of eight. Perhaps someday an optical cochlear implant will allow deaf people to once again enjoy music and hear all the nuances in sound that a hearing person would enjoy".

Unlike electrical current, which spreads through tissue and cannot be focused to a point, infrared light can be focused, so numerous wavelengths (corresponding to numerous frequencies of sound) could be aimed at different cells in the inner ear.

Nerve cells that send sound signals from the ears to the brain can fire more than 300 times per second, so ideally, a cochlear implant using infrared light would be able to perform as well. In the Utah experiments, the scientists were able to apply laser pulses to hair cells to make adjacent nerve cells fire up to 100 times per second. For a cochlear implant, the nerve cells would be activated within infrared light instead of the hair cells.

Rabbitt cautioned it appears to be five to 10 years before the development of cochlear implants that run optically. To be practical, they need a smaller power supply and light source, and must be more power efficient to run on small batteries like a hearing aid.

Optical Prosthetics for Movement, Balance and Vision Disorders
Electrical deep-brain stimulation now is used to treat movement disorders such as Parkinson's disease and "essential tremor, which causes rhythmic movement of the limbs so it becomes difficult to walk, function and eat," says Rabbitt.

He is investigating whether optical rather than electrical deep-brain stimulation might increase how long the therapy is effective.

Rabbitt also sees potential for optical implants to treat balance disorders.

"When we get old, we shuffle and walk carefully, not because our muscles don't work but because we have trouble with balance," he says. "This technology has potential for restoring balance by restoring the signals that the healthy ear sends to the brain about how your body is moving in space".

Optical stimulation also might provide artificial vision in people with retinitis pigmentosa or other loss of retinal cells � the eye cells that detect light and color � but who still have the next level of cells, known as ganglia, Rabbitt says.

"You would wear glasses with a camera [mounted on the frames] and there would be electronics that would convert signals from the camera into pulses of infrared radiation that would be patterned onto the diseased retina that normally does not respond to light but would respond to the pulsed infrared radiation" to create images, he says.

Hearing and vision implants that use optical rather than electrical signals do not have to penetrate the brain or other nerve tissue because infrared light can penetrate "quite a bit of tissue," so devices emitting the light "have potential for excellent biocompatibility," Rabbitt says. "You will be able to implant optical devices and leave them there for life".