NEW KIND OF LIGHT ON THE BASIS OF POLARIZATION
A new method of communication over fiber developed by physicists of the Department of Naval Research. Instead of using the amplitude and frequency of the electromagnetic waves, they use polarized waves to carry the signal. This method offers a novel and elegant method of secure communication over fiber optic cable.
Electromagnetic waves, like light and radio waves have an amplitude, frequency and polarization. Changes in amplitude and frequency has long been used to carry information in the radio frequency, but the polarization as a phenomenon never fully investigated.
Physics Division of the Naval Research Gregory van Vigdzheren (Technical College of Georgia), and Rajarshi Roy (University of Maryland) have demonstrated an ingenious method of communication through fiber-optic cable, using state of the dynamic vibration of polarized light. Unlike previous methods for transmitting signal light polarization state is not directly used to encode data. Currently, the optical fiber is practiced such transfer, which modulates a special kind of laser light carrying information in binary.
Van Vigdzheren and Roy used the ring laser with an erbium-doped fiber. Erbium amplifies an optical signal, and transmits a ring laser. In a ring laser, laser successive intervals (steps), the annular tracks may be split into individual rings to be transmitted via fiber optic cable.
This division into rings and allow to carry information also like binary, but only the evaluation of the Rings? Have | or no I | (1 or 0).
Nonlinear optical fiber produces dynamic random changes in the polarization of light, and the signal is input as a normal modulation. The incoming signal may be saved weak due to the use of relatively small amplitude. The incoming beam is split into two parts when ingested of communication channel to the receiver. One of them is delayed by approximately 239 nanoseconds, - the time it takes the signal to bypass once around the ring laser. Light obtained directly compared, time delayed light.
When random changes (noises) are subtracted, then the superposition of the two signals is a desired signal carrying information. Changes in voltage, and temperature on the communications equally summarized and included.
This is a very clever method that hides the signal in the noise, says the researcher of the Department of Naval Research Mike Schlesinger, who oversaw the study. This provides an advantage over direct encoding polarization which has no means to extract a signal.
Contact Information: Gail S. Cleere, cleereg@onr.navy.mil, 703-696-4987, Office of Naval Research
