Abstract: An optical fiber and an optical amplifier including the optical fiber are disclosed, the optical fiber includes a core region for guiding a propagation of a multimode optical signal, a cladding region laterally surrounding the core region and at least two doped rings, each of the at least two doped rings having a corresponding rare-earth or transition metal dopant concentration. The core region includes a central core having a first refractive index, at least one core layer laterally surrounding the central core, each of the at least one core layer having corresponding internal and external radii, an internal radius of an innermost core layer corresponding to a radius of the central core and an external radius of the outermost core layer corresponding to a radius of the core region.

Abstract: An improved method and apparatus for optical and radio frequency implementation of a fast frequency hopping spread spectrum communication for code division multiple access systems is disclosed. The method avoids the frequency hopping synthesizer requirements in the transmitter as well as in the receiver. In a system where a pool of CDMA users share a channel characterized by a number of F available frequencies (or frequency bands), each user is assigned a subset of M (M less than or equal to F) frequencies from the F available frequencies, selected and ordered in time as prescribed by his own code (or address). In the transmitter, the information bit sequence modulates a broadband source so that the energy assigned to a data bit is concentrated on just a short interval of the bit period which is less than or equal to the so-called chip interval.

Abstract: An improved method and apparatus for optical and radio frequency implementation of a fast frequency hopping spread spectrum communication for code division multiple access systems is disclosed. The method avoids the frequency hopping synthesizer requirements in the transmitter as well as in the receiver. In a system where a pool of CDMA users share a channel characterized by a number of F available frequencies (or frequency bands), each user is assigned a subset of M (M less than or equal to F) frequencies from the F available frequencies, selected and ordered in time as prescribed by his own code (or address). In the transmitter, the information bit sequence modulates a broadband source so that the energy assigned to a data bit is concentrated on just a short interval of the bit period which is less than or equal to the so-called chip interval.