Abstract: Methods and apparatus for managing static and dynamic optical network configurations to enable mapping an actual optical network or validating an expected optical network are provided. In one embodiment a validation method includes the step of selecting an optical path having a plurality of nodes from a database defining an expected optical network. A list of detected pilot tones from each node associated with the selected optical path is generated. An expected list of pilot tones associated with each node of the selected optical path is generated. Comparison of the expected and detected lists identifies any mismatched nodes. Another method includes the step of setting a first pilot tone source to have a first pilot tone value. All other network pilot tone sources are set to have another pilot tone value. An optical path associated with the first pilot tone source is then mapped by identifying each node of the network having the first pilot tone value.

Abstract: A method of gain control in a fiberoptic repeating system is disclosed. By the present invention, the signal levels of an optical cable can be frequently monitored without affecting the control operations of the base station. Thus, damped signal levels can effectively be compensated.

Abstract: The direct optical amplifier of the present invention monitors not only a pilot tone signal but also the main signal, and when the pilot tone signal loses relation to the main signal, re-establishes the relation between the level of the pilot tone signal and the average level of the main signal such that the pilot tone signal again functions as the reference light of the main signal. The average level of the true main signal from which a noise component has been eliminated is determined by means of a wavelength analyzer. The average level of the true main signal that has been determined is correlated with the level of a pilot tone signal that is monitored, whereby the pilot tone signal again functions as the reference light of the main signal. The monitored pilot tone signal is then controlled to obtain the desired average level of the true main signal.

Abstract: Embodiments of an apparatus for forming a WDM signal having orthogonally polarized optical channels are disclosed. Utilizing the optical channels formed using non-polarization-maintaining components, the apparatus selectively controls a state of polarization (SOP) of each optical channel.

Abstract: In an optical WDM network, each optical channel is modulated with a respective channel identity. Detectors, conveniently at multiplex ports of optical band filters, detect the channel identities of all of the optical channels in an optical signal at the respective points to produce respective channel lists. A network management system determines channel lists for through ports of the optical band filters, identifies matching pairs of channel lists to determine a topology of each node and to identify optical paths entering or leaving each node, and identifies matching pairs of channel lists for these paths to determine an inter-node topology of the network. The channel identity detector points can alternatively be at the optical paths entering or leaving each node.

Abstract: An optical communication system for optically transmitting transmission data from a transmitting station to a transmitting device includes an adder for adding an intermediate frequency subcarrier signal modulated with data to be transmitted to a pilot carrier signal as a sinusoidal wave, and an electro-optical converter for electro-optically converting the above sum signal to an optical signal by directly modulating a semiconductor laser element having a resonant frequency fr in accordance with the sum signal and transmitting the signal to an optical fiber for a down link. The frequency fIF of the intermediate frequency subcarrier signal and the frequency fLO of the pilot carrier signal satisfy fLO?fIF?1[GHz], 2×fIF<fLO<(?)×fr, fIF<1[GHz], and 2 [GHz]<fLO.

Abstract: An optical transmission system including at least one optical transmitter configured to transmit at least one signal wavelength and a tuning wavelength, an optical receiver including an optical filter having a filter bandwidth including the at least one signal wavelength and a percentage of the tuning wavelength and an optical to electrical signal converter configured to receive the at least one signal wavelength from said filter, a first tuning optical to electrical converter configured to receive a first portion of the tuning wavelength stopped by said filter, a second tuning optical to electrical converter configured to receive a second portion of the tuning wavelength passed by said filter, and a filter controller configured to tune the filter bandwidth based on the relative proportion of first and second portions of the tuning wavelength provided to the first and second tuning optical to electrical converters.

Abstract: To automate fiber connectivity management in optical systems, a dedicated low bit-rate communications channel unique to each fiber connection in an optical system is provided. The dedicated communications channel simplifies fiber connectivity management by supporting the exchange of port identification information from one optical component to another after which processing determines if the specific connection is a desired association. The dedicated communications channel supports optical interconnection surveillance for all card-to-card optical connections within a group of related cards or within an optical network link. Automating fiber connectivity management in this manner will enhance future products by simplifying the fiber connection validation process and ensuring that any specific connection between optical components is the required association.

Abstract: An optical auxiliary signal, produced in a central device, is transmitted in addition to a user signal from the central to a remote optical device via at least two optical supply line fibers which are provided for transmitting optical signals between the central and remote optical devices. The optical auxiliary signal received in the remote optical device is diverted, is transmitted via a second optical supply line fiber to the central optical device, and the reception or the absence of the optical auxiliary signal and of the optical user signal in the central optical device are evaluated in order to monitor the operational state of the optical supply line fibers.

Abstract: In a method and system for evaluating distributed gain in an optical transmission system, a data signal and a residual pump laser signal propagating in opposite directions within a waveguide are monitored. Modulation of the residual pump laser signal is correlated with low frequency components of the data signal. This correlation is used to determine cross-talk between the data signal pump laser signals, as a function of location within the waveguide. The distributed gain is then evaluated from the cross-talk, using a known relationship, or proportionality, between gain and cross-talk.

Abstract: A method of optical communication includes providing a plurality of optical signals each associated with a distinct channel of a composite optical signal. A unique pilot tone signature is superimposed on each channel. The spectral composition of each signature includes a plurality of frequencies. In one embodiment, binary frequency shift keying at a frequency fm is used to shift between instantaneous frequencies f1 and f2 wherein f2+&Dgr;f=f1−&Dgr;f=fc. Choosing 1 Δ ⁢   ⁢ f f m ≈ 1.

Abstract: In the WDM communication system, in the absence of data to be transmitted on an optical channel, a pilot signal transmitting means transmits the channel-unique pilot signal data on the channel. A WDM communication apparatus on a receiving end detects the pilot signal data in the received WDM signals, and on the basis of the detection result, it evaluates whether each channel is used or not. It is thus easy to recognize which channel is unused (idle) of the WDM signals, so that channel resources can be used effectively according to the traffic.

Abstract: The present invention provides an automatic power restoring method capable of reliably detecting continuity by the dissolution of a line fault, to restore the optical power, even in a structure including an optical amplification medium on an optical transmission path and an optical communication system using the method. To this end, in an optical communication system to which the automatic power restoring method of the invention is applied, a pilot signal having a low transmission rate, a wavelength of which is set based on loss wavelength characteristics obtained by combining loss wavelength characteristics of an optical fiber used for the optical transmission path and loss wavelength characteristics of the optical amplification medium on the optical transmission path, is transmitted and received between an optical transmitting station and an optical receiving station when a line fault occurs, and a detection of continuity is thus performed.

Abstract: An optical line terminal determines an approximate location of impairment in an optical transmission path (e.g., optical fiber) without disconnecting the optical line terminal from the optical transmission path. The optical line terminal generates pilot tones that are modulated on an optical signal and used to make reflection and dispersion measurements in a frequency domain reflectometry manner, thus providing for in-vivo diagnostic testing of the optical transmission path. The dispersion can be automatically corrected by using a dispersion compensator.

Abstract: There is disclosed an optical wireless transmission apparatus in which a pilot light emitting section of a receiving/emitting section sends a pilot light in a wavelength region of 930 nm to 960 nm to a target apparatus, and a light receiving device having a light receiving sensitivity only to the same wavelength region of 930 nm to 960 nm receives light sent from the target apparatus. When the pilot light in the wavelength region of 930 nm to 960 nm is used, the pilot light is not obstructed by sunlight, and therefore optical axis adjustment can be mutually and exactly performed by the use of the pilot light sent from the target apparatus.

Abstract: An optical wireless communications system has a first optical wireless communications apparatus for transmitting a pilot beam and a second optical wireless communications apparatus for receiving the pilot beam to have a match for an optical axis of the first optical wireless communications apparatus and another optical axis of the second optical wireless communications apparatus. The first optical wireless communications apparatus has a modulator for modulating the pilot beam with a specific signal. The second optical wireless communications apparatus has a demodulator for demodulating the modulated and transmitted pilot beam to reproduce the specific signal and sending the reproduced specific signal to at least either the second optical wireless communications apparatus or an apparatus connected to the second optical wireless communications apparatus.

Abstract: A method and system for identification of a channel in an optical network is provided. The channel is identified by the use of unique combinations of two or more low frequencies, or tones, modulated onto the channel and optionally, a network parameter associated with the channel.

Abstract: A method and system for identification of a channel in an optical network is provided. The channel is identified by the use of unique combinations of two or more low frequencies, or tones, modulated onto the channel and optionally, a network parameter associated with the channel.

Abstract: In a method of controlling a switching operation of an optical network for use in connection between an optical transmitter and an optical receiver through an optical switch is controlled by a switch controller, the optical receiver is given through the optical switch a sequence of combined optical signals which is formed by combining a sequence of optical signals with an additional sequence of optical signals. The additional sequence of the optical signals may be either a sequence of optical signals sent to another optical receiver or a sequence of dummy optical signals. The combined optical signal sequence has a time interval which is defined between two adjacent ones of the combined optical signals and which is shorter than a predetermined time interval of, for example, 1 millisecond. Such a combined optical signal sequence serves to avoid occurrence of an optical surge appearing when the time interval is longer than the predetermined time interval.

Abstract: A communications network (e.g. fibre to the home (FTTH) or wireless) comprises a head end, to which outstations are couples via a shared point-to-multipoint medium. The head end is arranged to transmit downstream to the outstations a sequence of frames comprising data frames and command frames. The command frames marshal control of upstream transmissions from the outstations. A first downstream command frame directed to a specific outstation indicates the beginning of a timeslot, and also indicates the time slot duration (including an indefinite duration). Where the duration is indefinite, a second command frame directed to at least the same outstation indicates the end of the allotted time slot. Further methods are provided to optimise timeslot allocation, and to support addition and removal of outstations on the network.

Abstract: A main optical signal is wavelength-multiplexed with an optical identifier which is different in wavelength from this main optical signal, before a wavelength-demultiplexing is take place at a desired point so as to isolate the optical identifier from the main optical signal for the purpose of monitoring establishment of correct or incorrect transmission route between transmission and receiving sides based on the detected optical identifier with reference to the stored corresponding data to the relationship between the main optical signal and the optical identifier which belongs to the main optical signal, wherein the monitoring is made without any photoelectric conversion of the main optical signal and any deterioration in quality of the main optical signal.

Abstract: The present invention relates to prevention of erroneous connection in an optical network and, in particular, it provides an optical communication node having route switching function as well as an optical network system using the same in a wavelength division multiplex (WDM) network system. There is provided an optical communication node that is connected to a specific optical path in an optical network, said optical communication node having: an external network that is placed thereunder; and an interruption means for interrupting connection between said optical network and said external network, wherein said interruption means interrupts the connection until a sequence of changing a route is completed when the route setting of said optical path is changed.

Abstract: An optical transmission apparatus capable of suppressing SBS by multiplexing an input signal with a pilot signal, and further capable of eliminating an adverse effect of intermodulation distortion between the input signal and the pilot signal is provided. When the input signal is a frequency-multiplexed signal obtained by multiplexing a plurality of signals aligned on a frequency axis at regular intervals &Dgr;f (&Dgr;f>0), a pilot signal generation part generates the pilot signal having a frequency {m−(1/2)}×&Dgr;f (m is an arbitrary natural number). A multiplex part multiplexes the input signal (electrical signal to be transmitted) with the pilot signal generated by the pilot signal generation part. An electrical-optical conversion part converts an electric signal outputted from the multiplex part into an optical signal through direct intensity modulation.

Abstract: A method, a system and a module are proposed for detecting and locating faults in an optical multi channel network composed of network nodes. The method includes assigning different sub-carrier pilot tones to a number of the nodes comprising Network Elements (NE), applying the different sub-carrier pilot tones to any signal added to the network via the respective nodes, checking presence of one or more of the sub-carrier pilot tones at one or more points of the network, and, based on results of the checking, locating a faulty section of the network in case a fault occurred.

Abstract: In an optical transmitter comprising a laser module including a laser diode and a monitor photodiode, a laser drive circuit for supplying a drive current to the laser module and an APC circuit for applying a bias current to the laser module on the basis of a detection signal from the monitor photodiode so that the output level of the laser module becomes constant, there is further provided an extinction ratio control circuit including an RF signal generating circuit, a low-pass filter and a peak detecting circuit. The extinction ratio control circuit superimposes an RF signal on an input data signal to the laser drive circuit to control the amplification degree of the laser drive circuit on the basis of the RF signal of the detection signal from the monitor photodiode so that the extinction ratio of the output light from the laser module becomes constant.