Abstract: The invention provides an optical fiber amplifier which assures stable operation of a pump light source and efficiently makes use of residual pump power to achieve improvement in conversion efficiency. The optical fiber amplifier includes a rare earth doped fiber. Pump light from a pump light source is introduced into one end of the rare earth doped fiber by way of a first optical coupler, and residual pump light originating from the pump light and arriving at the other end of the rare earth doped fiber is applied to the other rare earth doped fiber amplifier or the loss compensation of a dispersion compensating fiber by Raman amplification.

Abstract: An optical amplifier includes an optical feedback resonant laser cavity (OFRC) including a power dependent loss element (PDLE) having the characteristic that as the incident laser power on the PDLE increases the cavity loss decreases. The OFRC with the PDLE provides optical gain control or optical power control for a WDM amplifier or a single channel power equalization amplifier (PEA), respectively. A 1×N×N WADM node incorporating more than one of these amplifiers, at least some of which commonly share a pump source, and a method for controlling a transient power change in a single channel optical amplifier or reducing a DC gain error in a WDM optical amplifier that are subject to dynamically variable operating conditions at an input of the amplifier, are also disclosed.

Abstract: A multi-stage optical amplifier that has an optical fiber with a first length of amplifier fiber and a second length of amplifier fiber. The optical fiber is configured to be coupled to a signal source that produces at least a signal wavelength &lgr;s and a pump source that produces a pump wavelength &lgr;p. Pump wavelength &lgr;p is less than signal wavelength &lgr;s. Signal input, signal output and pump input ports are each coupled to the optical fiber. A first lossy member is coupled to the optical fiber and positioned between the first and second lengths of amplifier fiber. A pump shunt is coupled to the signal input port and the signal output port.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.

Abstract: A two-stage erbium doped fiber amplifier (EDFA) using remnant pumping light is provided. The two-stage erbium doped fiber amplifier (EDFA) using remnant pumping light includes a first erbium doped fiber amplifying unit for multiplexing remnant pumping light received from a rear-stage and received optical signal, wherein the input optical signal is amplified by the remnant pumping light and a second erbium doped fiber amplifying unit which receives pumping light generated by a pumping source and optical signal output from the first erbium doped fiber amplifying unit, multiplexes the same, amplifies the optical signal output from the first erbium doped fiber amplifying unit, and outputs the remnant pumping light to the first erbium doped fiber amplifying unit.

Abstract: An amplifier system includes: (i) a distributed Raman fiber amplifier adapted to amplify C and L-band signals and; (ii) a discrete Raman fiber amplifier module that includes a C-band amplification stage and an L-band amplification stage. The discrete Raman fiber amplifier module is operatively connected to the distributed Raman fiber amplifier and amplifies signals received from the distributed Raman fiber amplifier. In one embodiment the distributed Raman fiber amplifier and the discrete Raman fiber amplifier share optical pump power provided by the shared pump.

Abstract: The present invention is directed to an optical communication system and optical signal amplifier for amplifying said optical signal having at least a first and a second wavelength as it propagates therethrough. The optical signal amplifier includes an input port; an output port; an optical medium, wherein a portion of the optical medium comprises a plurality of optical paths corresponding to the first and second wavelengths of the optical signal; a light radiation generator capable of coupling light radiation of a plurality of light radiation wavelengths related to the first and second wavelengths of the optical signal into each of the optical paths, whereby the first and said second wavelengths are amplified by Raman amplification; and an optical combiner for recombining the first and second wavelengths of the optical signal to generate the amplified optical signal.

Abstract: A twin coupler system couples a multimode pump power signal from a pump fiber to an optical information carrying double-clad signal fiber. The twin coupler system includes first and second optical couplers and a mode scrambler. The first optical coupler couples the pump fiber to the optical signal fiber to transfer outer modes of the pump power signal from the pump fiber into the optical signal fiber. The mode scrambler scrambles the modes of the pump power signal remaining in the pump fiber beyond the first optical coupler. The second optical coupler couples the pump fiber to the optical signal fiber to transfer outer modes of the scrambled pump power signal from the pump fiber into the optical signal fiber.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.