Abstract: An optical add/drop multiplexing (OADM) apparatus and method are disclosed for detecting pilot tones, removing ghost tones, and re-inserting pilot tones on WDM signals in an optical network. The OADM apparatus comprises a smart processing and control unit (PCU) for detecting pilot tones used for channel identifications, including identifying and removing ghost tones associated with respective optical channels, and re-inserting the processed pilot tones into the respective optical channels. The OADM apparatus and method may incorporate digital PCU or analog PCU for processing pilot tones and removing ghost tones.

Abstract: If a repeater supervisory control (SV), a pre-emphasis automatic adjustment (PE), a receiving side threshold value automatic adjustment (Vth), a transmitting side dispersion compensation value setting (VDC(T)), and a receiving side dispersion compensation value setting (VDC(R)) are executed for an optical main signal, these controls are executed in the above described priority order. Accordingly, if the controls are independently executed, or if two or more controls simultaneously occur, a control with a higher priority is executed. In this way, a transmission quality of an optical signal is prevented from being badly influenced as a result that the controls are simultaneously executed.

Abstract: In the WDM systems, the OSNR and the signal loss among the optical signals are substantially minimized at the receiving terminal to combat the SRS effects. An equal amount of the signal loss is expected for every span in the transmission path so that the optical amplifier gain tilt is not affected among a number of wavelength frequencies in the optical signal. This is accomplished by controlling the amplification process according to a feedback from the monitoring units for monitoring the optical signal.

Abstract: The present invention relates to a method for processing an optical signal is provided. An optical signal is input into an optical waveguide structure for providing a nonlinear effect. As a result, the optical signal undergoes chirping induced by the nonlinear effect. An output optical signal output from the optical waveguide structure is supplied to an optical bandpass filter to thereby extract components except a small-chirp component from the output optical signal. The optical bandpass filter has a pass band including a wavelength different from the wavelength of the optical signal. By extracting the components except the small-chirp component from the output optical signal in the form of pulse, it is possible to remove intensity fluctuations or accumulated noise especially at a top portion and/or a low-power portion of the pulse.

Abstract: A synchronous optical regenerator applies intensity modulation and phase modulation. The phase modulation is effected after the intensity modulation by the crossed Kerr effect in a Kerr fiber. The clock used for the phase modulation is obtained by injecting a continuous wavelength into the intensity modulator. The regenerator therefore includes a multiplexer coupling continuous light with the signals transmitted, an intensity modulator modulating the signals transmitted and the continuous light, and a Kerr fiber phase modulating the transmitted signals by crossed phase modulation with the intensity-modulated continuous light. Applications include wavelength division multiplex transmission systems.

Abstract: The present invention relates to a method for regenerating an optical signal suitable for WDM (wavelength division multiplexing). In this method, an optical signal is supplied to an optical waveguide structure (e.g., optical fiber) for providing a nonlinear effect. As a result, the optical signal undergoes chirp induced by the nonlinear effect. Then, an output optical signal output from the optical waveguide structure is supplied to an optical filter to thereby remove a small-chirp component from the output optical signal. By removing the small-chirp component from the output optical signal in the form of pulse, intensity fluctuations or accumulated noise especially at a top portion and/or a low-power portion of the pulse can be removed. Accordingly, the optical signal can be regenerated independently of the bit rate, pulse shape, etc. of the optical signal.

Abstract: In an optical transmission system, an optical terminal transmits a plurality of tone signals corresponding to a plurality of gain bands, where the frequencies of the plurality of tone signals are different from each other, and each of the plurality of tone signals has a characteristic which is varied according to detected power of optical signals in the corresponding gain band. Each optical repeater receives the plurality of tone signals, extracts the characteristics of the plurality of tone signals, and compares a signal representing each characteristic with a reference signal. The optical repeater controls the gains of optical amplification in the plurality of gain bands based on the comparison result so as to equalize the gains in the plurality of gain bands.

Abstract: An optical packet node for receiving and transmitting optical packets is disclosed. A multiwavelength band splitting device splits received optical packets transmitted via multiwavelength bands into at least three groups, each group including one multiwavelength band. A multiwavelength band combining device combine the three groups of multiwavelength bands. At least two optical packet add drop multiplexers are placed between the multiwavelength band splitting device and the multiwavelength band combining device. Each optical packet add drop multiplexer adds and drops at least one individual wavelength to a respective multiwavelength band group. A load balancing stage is connected to the optical packet add drop multiplexers to provide an interconnection between at least two wavelength bands.

Abstract: A repeater, useable for connecting switches in a data communication network, is provided in a distributed and/or modular fashion. The repeater includes a plurality of separate and distinct components or modules connected to or at least partially housed in, the various switches which the repeater modules couple. Preferably, the repeater autodetects and/or autoconfigures some or all aspects of repeater operations, such as detecting and/or configuring appropriate full/half-duplex mode operation or detecting and/or configuring in response to appropriate or approved cable-type connections. The distributed and/or modular repeater facilitates accommodating various switching or repeater needs as a network grows or contracts.

Abstract: An optical fiber transmission link has a first optical fiber with a high effective area coupled to a second, downstream optical fiber with a low effective area. The downstream fiber has non-zero dispersion and low dispersion slope. Characteristics of the upstream fiber permit the launching of high power channels in a wavelength division multiplexing, and characteristics of the downstream fiber enable Raman amplification along that fiber to extend the transmission distance before a need for discrete amplification. The downstream fiber has a non-zero dispersion in the C-band wavelengths and a low dispersion slope and has low attenuation at the signal and pump wavelengths. Refractive-index profiles include variations of W-type fibers that may include outer rings of positive or negative index. Pumping of the downstream fiber may occur either co-directionally to the signals, counter-directionally to the signals, or in both directions.

Abstract: Different bands (C-band and L-band) are allotted respectively to an upstream optical signal and a downstream optical signal. In a transmission-path optical fiber for Raman amplification, the C-band optical signal is amplified by pumping light from a C-band pumping light source, and the L-band optical signal is amplified by pumping light from an L-band pumping light source. As a result of this configuration, the optical signals are Raman-amplified through backward pumping in both upstream and downstream directions, whereby negative effects, which could be exerted on the optical signals by forward pumping, can be avoided.

Abstract: A system and method for optical power transient control and prevention in communication networks. An optical signal propagating on a network is demultiplexed into individual spectral bands, e.g. at an OADM, and an optical power monitor point is included into each band. A separate idler laser is provided for each OADM band. The power output of each laser is adjusted such that it compensates for the signal power lost from each band. The wavelength of each laser is chosen to fall within the associated OADM spectral band, but outside of the window of individual signal wavelengths, so that it may propagate through the network without causing deleterious interference at the receiver.

Abstract: The invention relates to a method of activating an optical communication system comprising a plurality of optical amplifiers having an optical amplifier, between optical transmission lines in which wavelength-division multiplex optical signals are transmitted. The method comprises steps of: generating a desired slope in a desired wavelength range of a gain wavelength curve of the optical amplifier; adjusting an output of the optical amplifier to a desired output level; performing the above two steps in a plurality of optical repeater stations, the steps being carried out in sequence from the first to the last optical repeater stations; and adjusting a level in each optical signal in the wavelength-division multiplex optical signal so as to have substantially constant optical signal-to-noise ratios in the optical signals to be received. Activating the optical communication system according to this procedure allows proper execution of gain slope compensation, output control, and pre-emphasis control.

Abstract: In one aspect of the invention, a system operable to reduce degradation of an optical signal to noise ratio where signals having multiple wavelengths are communicated over a common optical link includes an amplifier assembly operable to introduce to a lower communication band a first gain and to introduce to a higher communication band a second gain that is different from the first gain. In addition, the system is operable to introduce a variable gain tilt into at least one of the communication bands. The different gains introduced to the higher and lower bands and the variable gain tilt introduced into at least one of the bands result in a reduction of a degradation of optical signal to noise ratio that could otherwise be caused by wavelength dependent attenuation when the communication bands are combined and communicated over an optical link.

Abstract: The invention describes a two-stage optical amplifier adapted for inserting OADM in the mid-stage, and an integrated assembly designed for implementing the amplifier in a way suitable for forming unidirectional and bi-directional configurations useful in optical networks. One of them is a so-called east-west configuration for a bi-directional transmission, where each direction of the optical transmission is served by the two-stage optical amplifier the 1st stage of which belongs to one integrated assembly, and the 2nd stage—to another assembly.

Abstract: There is proposed a method and a module for real time control of power per optical channel in a multi-channel optical communication line formed by a group of optical elements connected in a chain by fiber spans. The group of elements comprises one or more optical fiber amplifiers (OFA); each of the spans is characterized by its span loss, while each of the OFA is characterized by its gain and its designed output power per channel. The method comprises steps of calculating an expected total input power value (EIP) for a particular optical amplifier (OFA) in the line, measuring a real total input power (MIP) at the particular optical amplifier, and comparing the values. If a difference between the EIP and the MIP at the OFA exceeds a predetermined value, the method (and the module) ensures adjusting the gain of the OFA to maintain its output power per channel constant.

Abstract: The invention provides for optical circulators which redirect light from port to port sequentially in one direction used to separate traffic in a bidirectional optical fiber transmission system. The invention provides for using two optical circulators in each span of bidirectional fiber so that the OSC channel can be transmitted in one direction opposite to the WDM channels.

Abstract: The present invention has an object to provide a WDM optical transmission system for effectively compensating such as wavelength dispersions of respective wavelength bands, by a simple constitution making use of a hybrid transmission path in case of transmitting a broadband WDM signal light containing a plurality of wavelength bands. To this end, wavelength dispersion characteristics of a hybrid transmission path utilizing a 1.3 &mgr;m zero-dispersion SMF and an RDF in the present WDM optical transmission system, are set such that compensation ratios of wavelength dispersion and dispersion slope become approximately 100% for a reference wavelength band which is one of a plurality of wavelength bands; and dispersion compensation fibers capable of compensating wavelength dispersions caused within the hybrid transmission path are inserted into propagation paths, respectively, within an optical amplifier, for the wavelength bands except for the reference wavelength band.

Abstract: In the variable gain compensating apparatus, input power of optical amplifiers employed in respective optical repeaters is monitored, and the monitored input power is transferred to a down-stream side by using supervisor (SV) light. In a repeater equipped with a variable gain tilt compensator, input power monitor information of the optical amplifiers employed in the respective repeaters provided on the upper stream side is acquired from a supervisor signal. While utilizing a linear relationship established between a gain tilt of an optical amplifier and input power of the optical amplifier, the acquired input power monitor information is compared with a reference power value so as to calculate gain tilt amounts of the respective optical amplifiers. Then, the optimum gain tilt compensation amount of the variable gain tilt compensator is determined based upon the calculated gain tilt amounts.

Abstract: The present invention provides a regenerator device for wavelength division multiplexed optical signals designed to regenerate the N channels of a multiplex simultaneously, the device being characterized in that it comprises at least one regenerator component (112, 152) suitable for coupling the inlet signal with a multiplex of N optical carriers, the regenerator component (112, 152) being constituted by a material presenting a spectrum line with non-uniform broadening so that there is no interaction between the various channels involved within the component.

Abstract: A system for reducing gain ripple of an optical system that includes a set of spans further includes a multiplexing unit and an optical filter. The multiplexing unit multiplexes a plurality of optical signals. The optical filter filters the multiplexed optical signals, prior to transmission of the multiplexed signals over the spans of the optical system, to reduce gain ripple.

Abstract: An optical transmitter is provided with: an optical signal generator for generating a main signal to be transmitted and its inversion signal as optical signals of different wavelengths; and a wavelength division multiplexer for wavelength division multiplexing the optical signals of different wavelengths generated by the optical signal generator and transmitting the multiplexed optical signal. By transmitting the main signal to be transmitted and its inversion signal as the wavelength division multiplexed optical signal (containing optical signals of different wavelengths corresponding to the main signal and the inversion signal), “inter-channel crosstalk” which occurs during multi-wavelength batch amplification by an optical amplifier (Raman amplifier, semiconductor optical amplifier, etc.) can be suppressed effectively, independently of the performance/characteristics of optical devices.

Abstract: There is suppressed deterioration of transmission quality resulting from FWM generated in the optical fiber of an optical transmission apparatus which performs wavelength division multiplex transmission. A wavelength division multiplexing optical transmission system is not restricted by a wavelength division multiplex density. Intensity of FWM generated in an optical fiber transmission line for each span is observed by a receiver side to determine intensity of output light to send the span by a sender side, to thereby suppress deterioration of the transmission quality due to the FWM generated in the optical fiber of a WDM optical transmission apparatus.

Abstract: A high-capacity optical transmission arrangement utilizing a plurality of laser sources and a plurality of wide-band optical amplifiers permit the reliable transmission of 1 Tb/sec rates over significant distances of optical fiber.

Abstract: A power controlling network element (10) for a communication system, is characterised in that it includes: (a) a detector (30) for measuring radiation power present in components of radiation; (b) element parts, for example a channel control unit (CCU) (60), transponders (90, 92, 94) and other modules, for at least one of: (i) transmitting to the detector (30) at least some components of input radiation received at the elements parts from the system; and (ii) generating one or more components of radiation and emitting said one or more components to the detector (30); (c) a field programmable gate array (FPGA) (40) for receiving data from the detector (30) indicative of radiation power in the components of radiation received at the detector (30), and for controlling radiation power emitted from or transmitted through the aforementioned element parts (60, 70, 80,90, 92, 94), so that the components of radiation received at the detector (30) are regulated in power to within predetermined power limits.

Abstract: A method, and optical network management system, including detecting, in an electrical domain, a change in performance of an optical transmission system, and determining a cause of the change based on data associated with an optical performance parameter. The data is collected from optical network elements that have a value for the optical performance parameter exceeding a threshold. Another embodiment includes an electrical monitoring device, including outputting an electrical signal that indicates a degradation in the performance, and transmitting a command to the optical network elements to collect the data. A further embodiment includes an optical network element, including transmitting an optical signal to the electronic monitoring point that converts the optical signal to the electrical signal, which is examined to detect the degradation, and transmitting the data to the network management system, if the value exceeds the threshold value.