Disclosed is a scheme of transmitting at least two or more transmission signals, in which at least two or more pure random noise signals are contained, through multiple paths, according to one embodiment of the present invention. To implement such a scheme, a complementary noise generator may be used in a high-speed communication method and system with enhanced security according to the present invention. Here, the complementary noise generator refers to an apparatus in which a total sum of summing altogether at least two or more generated noises becomes 0. Namely, the complementary noise generator can generate m noises, and the sum of the in noises becomes 0. By injecting a plurality of noises having such feature into different paths, a channel capacity of each channel is reduced, thereby making a single wiretapping difficult. In comparison, because a receiver receiving a plurality of transmission signals with injected noises receives all noise signals and then sums up the noise signals, the noises are offset, and it is possible to effectively receive the original signal (random key K) intended for transmitting by a transmitter.

We provide methods and apparatus for preparing crystalline-clad and crystalline core optical fibers with minimal or no breakage by minimizing the influence of thermal stress during a liquid phase epitaxy (LPE) process as well as the fiber with precisely controlled number of modes propagated in the crystalline cladding and crystalline core fiber via precisely controlling the diameter of crystalline fiber core with under-saturated LPE flux. The resulting crystalline cladding and crystalline core optical fibers are also reported.

An optical beam delivery device, such as an optical fiber, includes: a first length of fiber having a first refractive index profile (RIP) to enable modification of one or more beam characteristics of an optical beam having a first wavelength; and a second length of fiber having at least one wavelength-modifying confinement region and situated to receive the optical beam from the first length of fiber.

Methods, apparatus, and systems for active saturable absorbance of an optical beam. An active saturable absorber may comprise an optical input to receive an optical beam, and one or more lengths of fiber between the optical input and an optical output. At least one of the lengths of fiber comprises a confinement region that is optically coupled to the output. The active saturable absorber may further comprise an optical detector to sense a characteristic of the optical beam, such as power. The active saturable absorber may further comprise a perturbation device to modulate, through action upon the one or more lengths of fiber, a transmittance of the beam through a fiber confinement region from a lower transmittance level to a higher transmittance level based on an indication of the characteristic sensed while the transmittance level is low.

Methods, apparatus, and systems for modulation of a laser beam. An optical modulator may comprise an optical input to receive an optical beam, and one or more lengths of fiber between the optical input and an optical output. At least one of the lengths of fiber comprises a confinement region that is optically coupled to the output. The optical modulator may further comprise a perturbation device to modulate, through action upon the one or more lengths of fiber, a transmittance of the beam through the confinement region from a first transmittance level at a first time instance to a second transmittance level at a second time instance. The optical modulator may further comprise a controller input coupled to the perturbation device, wherein the perturbation device is to act upon the one or more lengths of fiber in response to a control signal received through the controller input.

We provide methods and apparatus for preparing crystalline-clad and crystalline core optical fibers with minimal or no breakage by minimizing the influence of thermal stress during a liquid phase epitaxy (LPE) process as well as the fiber with precisely controlled number of modes propagated in the crystalline cladding and crystalline core fiber via precisely controlling the diameter of crystalline fiber core with under-saturated LPE flux. The resulting crystalline cladding and crystalline core optical fibers are also reported.