Abstract: An optical transmission system with two counter propagating wavelength division multiplexed (WDM) optical signals carried by an optical fiber transmission line, has a first Raman pump for launching a first beam of pump energy for amplifying both WDM signals so that the first beam counter-propagates with respect to a first WDM signal The system also includes a second Raman pump for launching a second beam of pump energy for amplifying both WDM signals so that the second beam counter-propagates with respect to a second WDM signal.

Abstract: An optical network comprises a plurality of nodes connected by an optical fiber. The nodes each comprise a pump combiner coupled to the optical fiber and operable to insert pump power into the fiber to provide Raman amplification of a signal in a connected section of the optical fiber. A pump source remote from the nodes and coupled to the pump combiners is operable to provide pump power to each of the pump combiners for Raman amplification.

Abstract: The invention relates to a system for injecting into a fiber signals from multiple sources at different wavelengths. The signals from each source are injected into the fiber by a circulator. The circulators of the various sources are cascaded. Reflector means for reflecting signals from sources previously injected are provided between each source and its circulator. The invention is used to inject signals from multiple sources without the injection of signals from one source attenuating signals from sources previously injected. It applies in particular to Raman amplification, for which purpose it provides a multiband source without attenuation between bands. Multiband amplifications is achieved without loss of gain between bands.

Abstract: A gain equalizer which equalizes gain versus wavelength characteristics of an optical amplifier. The gain versus wavelength characteristics of the optical amplifier include first, second and third gain peaks in a wavelength band with the second gain peak being between the first and third gain peaks. The optical amplifier amplifies an input signal in accordance with the gain versus wavelength characteristics to produce an output signal. The gain equalizer includes first, second and third optical filters having first, second and third transparency characteristics, respectively. The first, second and third transparency characteristics are periodic waveforms having different periods related to the wavelength difference between the first and third gain peaks. The second transparency characteristic is a periodic waveform having a period equal to 1/(2n) of the period of the waveform of the first transparency characteristic.

Abstract: Flatness of a gain (optical output level) is maintained even when a wavelength division multiplex signal light (WDM signal light) is amplified in an optical amplification utilizing Raman amplification function. The optical amplifier comprises: two (first and second) pumping light sources for Raman amplification for outputting first and second pumping lights; the wavelength multiplexer for Raman amplification for allowing the first and second pumping lights to be incident on optical fiber transmission paths, where the WDM signal light propagates, in the direction opposite to the propagation direction of the signal light. The signal lights are Raman amplified by the both pumping lights. A wavelength of the first pumping light is set such that the gain of the Raman amplified signal light declines in the right direction, and, on the other side, the wavelength of the second pumping light is set such that the gain declines in the left direction.

Abstract: The present invention relates to an optical transmission system and a channel assigning method with structure to reduce dispersion of power levels among signals dropped at respective signal branchpoints on an optical transmission line out of signals of multiple channels amplified in an optical amplifier. The optical transmission system has an optical transmission line in which signals of multiple channels propagate, an optical amplifier provided on the transmission line, and a plurality of signal branchpoints disposed on the downstream transmission line in which the signals of the channels outputted from the optical amplifier propagate. Each of the signal branchpoints drops a signal of a channel with a lowest power level out of arriving signals in the channels. This reduces the dispersion of power levels among signals dropped at the respective branchpoints, as a whole of the optical transmission system.

Abstract: Disclosed is an optical switch for transmitting or shutting down an input light signal in accordance with a set switching state. The optical switch comprises first and second optical amplifiers connected in cascade. When an optical fiber amplifier comprising EDFs (11 and 12) and pumping sources (31 and 32) is used as the first and second optical amplifiers, the switching is accomplished by switching on or off the pumping sources (31 and 32) in accordance with control signals supplied from a control circuit (300). One input light signal can be dropped through a first optical branch (51) located on the input side of the optical switch, while another input light signal can be added through a second optical branch (53).

Abstract: An optical fiber (12a) with a large effective core area and a large chromatic dispersion value is disposed on an input side of signal light, and an optical fiber (12b) with a small effective core area and a small chromatic dispersion value or a chromatic dispersion value of negative polarity is disposed on an output side of the signal light. A pumping light source (14) generates pumping light of 1450 nm to cause Raman amplification of 1550 nm in the optical fiber (12b). The output light from the pumping light source (14) enters the optical fiber (12b) from the back through a WDM optical coupler (16). Provided that y=(Pin−&agr;)/(Pp·10 Log L) where input power of the optical fiber (12a) (i.e.

Abstract: An optical dropping apparatus and an optical add/drop multiplexer capable of dropping optical signals of an arbitrary wavelength from a WDM optical signal. The apparatus comprises a generating means for occurring four-wave mixing, a dropping means for dropping light of a predetermined wavelength, and a controlling means for controlling the wavelength of a pump light which is occurred four-wave mixing at the generating means. This apparatus is able to change the wavelength of the optical signals to be dropped, by changing the wavelength of the pump light.

Abstract: A multi-channel light source generator has a pumping laser source for generating a pumping laser having a predetermined wavelength, a multi-channel light source generating device for generating multi-channel light sources using the pumping laser, a light separating device for separating the pumping laser and the multi-channel light sources, a demultiplexing device for separating the multi-channel light sources into a plurality of individual light sources, an intensity adjusting device for adjusting an intensity of the individual light sources, and a multiplexing device for combining the individual light sources outputted from the intensity adjusting device.

Abstract: An object of this invention is to improve transmission characteristics in WDM transmission. An optical transmitter (10) wavelength-multiplexes signal lights of wavelengths &lgr;1 through &lgr;n and outputs them onto an optical transmission line (12). Optical powers of the signal lights of the respective wavelength &lgr;1 through &lgr;n are identical or become smaller proportional to the wavelength. One repeater span of the optical transmission line (12) is composed of an optical fibers (20, 22) and an optical amplifier (24), and a gain equalizer (26) is dispersed every several repeater spans. The optical amplifier (24) in the repeater span amplifies each signal light so that optical power of a signal on the shorter wavelength side becomes smaller than that of a signal on the longer wavelength side. The gain equalizer (26) equalizes optical powers of the respective signal lights.

Abstract: An optical communication system includes a plurality of optical channels, each of which passes a single optical wavelength signal. Each of the plurality of optical channels includes an optical amplifier which is controlled to operate at a predetermined output power level independent of channel wavelength and input power level by operating each optical amplifier in a saturation mode. Pumping power for operating each optical amplifier in the saturation mode is supplied from shared optical pumps or a plurality of one per channel optical pumps.

Abstract: An optical transmission system accomplishes optical transmission to a long distance by combining a multiplexing line terminal with optical amplifiers, linear repeaters, and regenerators with optical amplifiers combined together. The system also accomplishes the optical transmission to a short distance by directly connecting the linear terminals therebetween, with an electric-to-optic converter replaced by an electric-to-optic converter having a semiconductor amplifier, with an optic-to-electric converter by an optic-to-electric converter having an avalanche photodiode as light receiver, an with no use of any optical booster amplifier and optical preamplifier in the multiplexing line terminal. With these, the optical transmission system can be easily constructed depending on the transmission distance required.

Abstract: In an amplified wavelength division multiplexes (WDM) fiber optic communication system, each channel experiences a different optical gain, dispersion and noise. Also, the evolution of WDM fiber optic systems to higher density channel spacing has further aggravated multi-channel non-linear distortions such as four-wave mixing (FWM) and cross-phase modulation (XPM). The standard method for controlling these nonlinearities is the peak power control method. The performance of the channels can be equalized by adjusting the transmission powers of the optical transmitters. However, just equalization of a performance indication factor (PIF) such as BER or Q is not the optimum approach when peak power control mode of operation dominates. This invention is directed towards improving the margins of performance of WDM fiber optic channels.

Abstract: An Optical Power Supply module is configured to be engageable in optical communication to an optical device. This Optical Power Supply module comprises: an optical circuit including (i) at least one input port configured to receive an optical signal; (ii) an optical circuit connected to the input port and including (a) at least a one light source providing optical pump power at a first wavelength, the wavelength known to cause amplification in rare earth doped optical fiber; (b) at least one bi-directional light combiner/separator combining the optical pump power and the optical signal; and (c) at least one position for a directional optical attenuator; (iii) at least one output port connected to the optical circuit and configured to transmit the optical signal and the optical pump power at the first wavelength to the optical device.

Abstract: A Raman optical-fiber amplifier used in a wavelength-division-multiplexing optical communication system is provided. The inventive amplifier includes an optical transmitter for transmitting wavelength-division-multiplexed optical signals through an optical fiber and an optical receiver for receiving the optical signals through the optical fiber, and further comprises an erbium-doped fiber which Raman-amplifies and outputs optical signals inputted through the first end of the erbium-doped fiber amplifier connected with the optical fiber; a pumping source which outputs pump light with a predetermined wavelength so as to Raman-pump the erbium-doped fiber; and, a wavelength-selective coupler which outputs the pump light to be introduced into the erbium-doped fiber.

Abstract: A bidirectional optical amplifying apparatus-and method of controlling the optical gain in a bidirectional WDM optical communication network includes a bidirectional optical amplifier for amplifying a forward WDM optical input signal and a reverse WDM optical input signal, a measurement means for measuring the total input intensity and the total output intensity of the bidirectional optical amplifier,and a control means for measuring a gain using the total input intensity and the total output intensity, compensating the error between the measured gain and a reference gain, and feedback controlling the bidirectional optical amplifier to uniformly maintain the gain. The measurement means divides a forward optical input signal and a reverse optical input signal, in a constant ratio, respectively, converts the divided optical signal to an electrical signal, and measures total input intensity.