Abstract: Hybrid enclosures for power and optical fiber are provided herein. A hybrid enclosure includes a power conductor terminal and an optical fiber splice area that are in separate first and second trays, respectively. In some embodiments, the power conductor terminal is a terminal of a circuit that is configured to supply power exceeding 150 Watts. Enclosures including multiple protective lids over power conductor terminal blocks are also provided.

Abstract: Disclosed is a submarine network device, comprising a fiber set, a pump laser set, an erbium doped fiber amplifier (EDFA) set, a primary fiber coupler (CPL) set and a secondary CPL set, wherein the primary CPL set comprises N primary CPLs, the secondary CPL set comprises N secondary CPLs, with N being an integer greater than or equal to 3. The fiber set is configured to connect the pump laser set, the primary CPL set, the secondary CPL set and the EDFA set. An input port of each primary CPL in the primary CPL set is at least connected with a pump laser. An output port of each secondary CPL in the secondary CPL set is at least connected with an EDFA. Output ports of each primary CPL in the primary CPL set are respectively connected with two different secondary CPLs that are spaced by a secondary CPL, and input ports of each secondary CPL in the secondary CPL set are respectively connected with two different primary CPLs that are spaced by a primary CPL.

Abstract: Techniques for data transmission include a geostationary earth orbiting satellite that includes a first optical communication system configured to receive forward-direction user data via a forward optical link between the satellite and a stratospheric high-altitude communication device, and a first radio frequency (RF) communication system configured to transmit, via a plurality of RF spot beams, the forward-direction user data. The stratospheric high-altitude communication device includes a second RF communication system configured to receive the forward-direction user data via a plurality of concurrent forward RF feeder links, and a second optical communication system configured to transmit to the satellite, via the forward optical link, the forward-direction user data received via the plurality of forward RF feeder links.

Abstract: A transmission device includes an interface configured to acquire, from a base band unit having a communication destination that is one of remote radio heads, communication destination information relating to the remote radio head of the communication destination, a receiver configured to receive signals of given wavelength from optical termination devices, and a transmitter configured to transmit a first signal that includes wavelength information indicative of the given wavelength and the communication destination information to optical termination devices, wherein, when the receiver receives, from an optical termination device of the remote radio head of the communication destination from among optical termination devices, a second signal of the given wavelength according to the first signal, the receiver sets, between the receiver and the optical termination device, a relay path that relays communication between the base band unit and the remote radio head of the communication destination.

Abstract: Provided are transmitting, receiving and communication systems of an optical network and a method for modulating a signal. The transmitting system includes: first Passive Optical Network (PON) equipment, configured to output a binary digital signal; and an M-order digital modulator, configured to modulate the binary digital signal into an M-order digital signal, and output the M-order digital signal, wherein each transmission symbol in the M-order digital signal carries information of N=log2M bits, where N is a natural number greater than 1 and M is a natural number. By the disclosure, the problems in the related art is solved, the bandwidths required by transmission are further reduced, and the actual cost of the optical transceiver modules is lowered.

Abstract: An optical communication system includes an optical transmitter that sends an optical signal; and an optical receiver that receives the optical signal. The optical transmitter controls a transmission rate of the optical signal to a first transmission rate corresponding to first reception light power lower than target reception light power of the optical receiver in response to transmission light power control for the optical signal corresponding to the target reception light power.

Abstract: An optical communication system includes an optical-signal transmission unit transmitting an existing optical signal and a low-rate-signal superimposition unit superimposing a low-rate signal on the existing optical signal by intensity modulation. It further includes: a low-rate-signal extraction unit that extracts the low-rate signal from the existing optical signal on which the low-rate signal is superimposed and converts the extracted low-rate signal into a low-rate electric signal; an add-on optical-signal transmission unit that transmits an add-on optical signal; a low-rate-signal superimposition unit that superimposes a low-rate signal on the add-on optical signal by the intensity modulation based on the low-rate electric signal; and a repeater that repeats the add-on optical signal on which the low-rate signal is superimposed, to a transmission destination.

Abstract: The path selection and wavelength assignment to a selected path are performed by mapping the wavelength reach to the demand distribution (agile reach) resulting in a 50-60% increase in the network reach. The network reach is further increased (about 2.2 times) when on-line measured performance data are used for path selection and wavelength assignment. The connections may be engineered/upgraded individually, by optimizing the parameters of the entire path or of a regenerator section of the respective path. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter and/or receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc.

Abstract: Optical regenerators and amplifiers are expensive to implement and maintain. A method or corresponding apparatus in an example embodiment of the present invention relates to an optical planning tool that plans an optical network configuration by determining a plurality of costs for maintaining signal strength in corresponding network configurations including (i) a configuration of regenerators, (ii) a configuration of pre-or post-amplifiers, and (iii) a configuration of pre- and post-amplifiers in candidate locations and regenerator modules. The candidate locations for placing pre-or post-amplifiers are determined based on loss in each span, expected traffic patterns, and proposed regeneration locations along paths of expected traffic. The regeneration modules are located in locations determined based on the candidate locations. The example embodiment selects a configuration from among the network configurations as a function of the plurality of costs, helping reduce the cost of network deployment.

Abstract: A transmission apparatus includes: an amplifier controller configured to determine a target value for an average optical input power of a transmitting amplifier in a transmitting-side apparatus, based on an index based on a quality of transmission from an output of the transmitting amplifier to an output of a receiving amplifier in a receiving-side apparatus; and a pre-emphasis controller configured to determine amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the output of the receiving amplifier.

Abstract: A relay device includes: a first port, a plurality of second ports, a splitter configured to branch first optical signals input from the first port into the plurality of second ports; and a plurality of optical modulators configured to modulate shared carrier light by multiplexing the carrier light with a plurality of second optical signals with different frequencies input from the plurality of second ports and by inputting the multiplexed carrier light into a plurality of nonlinear optical mediums, and to transmit the carrier light to the first port.

Abstract: Embodiments of the present invention provide a repeater, including a local unit and a remote unit. The local unit includes a base station interface unit, multiple local basic units and a controller. The remote unit includes multiple remote basic units. The controller is configured to generate, according to a down-tilt angle and/or azimuth angle of a downlink signal instructed by a control instruction, a downlink signal phase for each remote basic unit. The multiple local basic units each are configured to perform, according to the downlink signal phase generated by the controller for a corresponding remote basic unit, phase adjustment on the downlink signal sent by the base station interface unit. The multiple remote basic units each are configured to receive the downlink signal sent by a corresponding local basic unit and to send the downlink signal.

Abstract: Provided are a passive optical network reach extender based on a wavelength tunable optical module and a method thereof. According to an embodiment of the invention, a passive optical network reach extender includes a first optical splitter configured to receive an optical signal from an optical line terminal and split the signal into optical signals having a multiplexed wavelength, a wavelength tunable remote relay configured to receive the optical signals split from the first optical splitter, and select and control an available wavelength for each port, a wavelength multiplexer configured to multiplex a wavelength of the optical signal output from the wavelength tunable remote relay, and a second optical splitter configured to split the optical signal multiplexed by the wavelength multiplexer into a plurality of optical network units.

Abstract: An optical transmission system is provided. The optical transmission system includes a user side optical repeater device (ORD), a central office side ORD, and wavelength multiplexing and wavelength de-multiplexing functions (MUX/DEMUX). The user side optical repeater device (ORD) is to be connected with a user side optical network unit (ONU), transmits data in two ways, and is used for wavelength division multiplexing (WDM). The central office side ORD is to be connected with a central office side optical line terminal (OLT), transmits data in two ways, and is used for WDM. The wavelength multiplexing and a wavelength de-multiplexing functions (MUX/DEMUX), are used for relaying between the user side ORD and the central office side ORD.

Abstract: A system and method for sizing transponder pools in a dynamic wavelength division multiplexing optical network having selected nodes designated to have a shared transponder pool is presented.

Abstract: In an optical signal processing apparatus, carrier light propagates through a nonlinear optical medium. An optical combiner optically combines output control light for generating idler light of the carrier light with the carrier light. An optical splitter splits the idler light from the carrier light. A receiver acquires a signal multiplexed on the carrier light from the idler light split by the optical splitter.

Abstract: An optical transmission apparatus includes a reception part for receiving a wavelength division multiplexed (WDM) signal reached via optical amplifiers; a measuring part for measuring an optical power level of each wavelength of the WDM signal received by the reception part; a determination part for determining whether an amount of tilt of the WDM signal calculated based on measurement results of the measuring part is suitable or not; an operation part for calculating the tilt correction amount to be applied to tilt correction processing performed by the optical amplifiers if the amount of tilt of the WDM signal is not suitable; and a notification part for notifying the optical amplifiers of the tilt correction amount.

Abstract: The present invention relates to an optical relay system for transmitting multi-band frequency signals with limited bands by using optical lines. According to the present invention, a plurality of band-limited signals are band-combined into one signal by using a combiner, and the signals are transmitted through multiple outputs by using a distributor, and thus a multi-stage filter is not necessary. In addition, the present invention is capable of effectively solving various problems such as damage to the original signals caused by the band combination of the multi-stage filter, and there is no need to precisely connect each of the band-limited signals to the determined ports of the combiner and the signals can be connected to random ports, thereby improving convenience of use.

Abstract: The path selection and wavelength assignment to a selected path are performed by mapping the wavelength reach to the demand distribution (agile reach) resulting in a 50-60% increase in the network reach. The network reach is further increased (about 2.2 times) when on-line measured performance data are used for path selection and wavelength assignment. The connections may be engineered/upgraded individually, by optimizing the parameters of the entire path or of a regenerator section of the respective path. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter and/or receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc.

Abstract: A ROADM device generates link information including a virtual link in which a first link that is used by a node apparatus for transmitting a signal and a second link of a ROADM device that is capable of branching a signal transmitted via the first link when the signal is transmitted via a WDM network are virtually connected each other, and transmits the generated link information.

Abstract: Provided is a time division multiple access over wavelength division multiplexed passive optical network (TDM-over-WDM-PON) system. According to the TDM-over-WDM-PON system, a downstream optical signal is separated according to a wavelength in a remote node, transmitted to an optical amplifying device located in subscriber equipment, amplified in the optical amplifying device, transmitted back to the remote node, and then transmitted to the subscriber equipment. Also, an upstream optical signal is transmitted to a wavelength converting device located in the subscriber equipment from the remote node, wavelength-converted in the wavelength converting device, returned back to the remote node, and then transmitted to a central office.

Abstract: A relay apparatus including: a first interface 11 that branches an optical signal that is input in a first direction from one side of the optical transmission line, and directs the optical signal to a first path and a second path, the first path being a processing path of an optical signal having a first transmission speed, the second path being a processing path of an optical signal having a second transmission speed that is different from the first transmission speed; a processing section 12 that executes processing on an optical signal propagating through each of the paths in accordance with a corresponding transmission speed; and a second interface 13 that binds the first path and the second path of the optical signal on which the processing is executed by the processing section, by means of wavelength multiplexing and directs to the other end of the optical transmission line.

Abstract: An optical communication system includes an optical-signal transmission unit transmitting an existing optical signal and a low-rate-signal superimposition unit superimposing a low-rate signal on the existing optical signal by intensity modulation. It further includes: a low-rate-signal extraction unit that extracts the low-rate signal from the existing optical signal on which the low-rate signal is superimposed and converts the extracted low-rate signal into a low-rate electric signal; an add-on optical-signal transmission unit that transmits an add-on optical signal; a low-rate-signal superimposition unit that superimposes a low-rate signal on the add-on optical signal by the intensity modulation based on the low-rate electric signal; and a repeater that repeats the add-on optical signal on which the low-rate signal is superimposed, to a transmission destination.

Abstract: A system and method for Raman amplification of optical signals in a wavelength division multiplexing (WDM) optical transmission system includes transmitting optical signals within a transmission band via an optical waveguide between a transmitter and a receiver, Raman-amplifying the optical signals with at least one pump so as to distort an amplification profile of the Raman amplification within the transmission band, and rectifying the distorted amplification profile so as to compensate for the distortion.

Abstract: A device may include a component, a first switch, a repeater, and a second switch. The component may configure optical paths between ports. The component may comprise a first pair of optical ports connected to a first pair of optical fibers, and a second pair of optical ports connected to a second pair of optical fibers. The first switch may be configured to output one of two optical signals received by the first pair of optical ports from the first pair of optical fibers. The repeater may reshape or amplify the outputted optical signal. The second switch may be configured to direct the reshaped or amplified signal to one of the second pair of optical ports.

Abstract: Consistent with the present disclosure, a method and apparatus for providing a uniform spectral gain of an optical amplifier is provided. Namely, a “balancing” step is carried out in which an optical channel having the lowest power level input to an optical circuit, such as an dynamic gain equalizer (DGE), is assigned a zero “attenuation error” and is substantially un-attenuated by the DGE. The lowest power level optical signal does not require further attenuation and effectively serves as a reference power level, which the power levels of the remaining optical signals are set to. For example, remaining optical signals are assigned either positive or negative attenuation errors relative to the zero attenuation error based on optical signal input powers to the DGE and accumulated DGE attenuations over time. Those optical signals having a negative attenuation error are substantially unattenuated by the DGE, because such optical signals are adequately attenuated and do not require further attenuation.

Abstract: A repeater is disclosed that transmits an optical signal using wave division multiplexing. The repeater includes a demultiplexing unit that separates plural channels contained in the optical signal, an adjusting unit that adjusts at least optical power of each of the channels according to a control signal, a multiplexing unit that outputs a multiple wavelength signal in which the channels are multiplexed, and a monitoring unit that determines a modulation scheme and a bit rate of the optical signal for each of the channels so as to generate the control signal.

Abstract: An optical transmission system is provided. The optical transmission system includes a user side optical repeater device, a central office side optical repeater device, and wavelength multiplexing and wavelength de-multiplexing functions. The user side optical repeater device is to be connected with a user side optical network unit, transmits data in two ways, and is used for wavelength division multiplexing. The central office side optical repeater device is to be connected with a central office side optical line terminal, transmits data in two ways, and is used for wavelength division multiplexing. The wavelength multiplexing and wavelength de-multiplexing functions are used for relaying between the user side optical repeater device and the central office side optical repeater device.

Abstract: The present invention provides a remodulating channel selector for a wavelength division multiplexed optical communication system. The remodulating selector receives a WDM input signal, selects a particular optical channel from the WDM signal and places the information from the selected signal onto a newly-generated optical output signal. The wavelength of the output optical signal can be the same as or different from one of the optical channels which comprises the WDM input signal. When used in a WDM optical communication system with remodulators at the transmission input, the remodulating selectors provide complete control over the interfaces with optical transmitters and receivers, permitting use with a broad range of optical equipment.

Abstract: There is provided a WDM transmission apparatus including a calculator being operable to calculate an optical signal level of a wavelength after wavelength demultiplexing based on information of OSNR, an amplifier controller being operable to compensate for the optical signal levels of all the wavelengths after wavelength demultiplexing to become a target level based on an optical signal level calculated by the calculator, and an deviation corrector being operable to correct a deviation of an optical signal level between each wavelength based on the optical signal level calculated by the calculator.

Abstract: An optical transmission system including an optical transmission path for transmitting WDM signals multiplexed different wavelength optical signals, the WDM signals including different bit rate optical signals or different modulation format optical signals; a repeater arranged in the optical transmission path, the repeater including a chromatic dispersion compensation unit for compensating chromatic dispersion compensation for the WDM signals; and a network management system including processes of determining a dispersion compensation ratio indicating the ratio with respect to the dispersion compensation amount at which the residual dispersion of the WDM signals are zero after transmission via the optical transmission path, on the bases of the mixture ratio of different optical signals included in the WDM signals, and variably setting the dispersion compensation amount for the in-line repeater according to the dispersion compensation ratio.

Abstract: The path selection and wavelength assignment to a selected path are performed by mapping the wavelength reach to the demand distribution (agile reach) resulting in a 50-60% increase in the network reach. The network reach is further increased (about 2.2 times) when on-line measured performance data are used for path selection and wavelength assignment. The connections may be engineered/upgraded individually, by optimizing the parameters of the entire path or of a regenerator section of the respective path. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter and/or receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc.

Abstract: A control-target-value setting unit sets a control target value corresponding to the number of multiplexed wavelengths measured by a number-of-multiplexed-wavelengths measuring unit. A controller controls the variable optical attenuator based on the control target value. An optical amplifier performs an optical amplification with a constant gain regardless of power of a wavelength-multiplexed light. The controller performs feedback control of the variable optical attenuator such that a result of measurement of the total power of the wavelength-multiplexed light coincides with the control target value.

Abstract: An optical network node for an n-channel dense wavelength division multiplexing (DWDM) optical communications network, includes an add path for adding an n-channel wavelength multiplex onto the network. The add path has an n-channel signal combiner for combining the n signal channels. An optical amplifier amplifies an output of the signal combiner. A multichannel wavelength selective filter with variable-per-channel attenuation filters out noise from the amplifier on a channel which carries no content to be added to the network, and controls amplitude of signals in channels to be added to the network. An add coupler couples the add path to the network.

Abstract: An optical transmission device includes: an optical signal generator to generate and transmit an optical signal that transmits data; a detector to detect a number of active clients; and a processor to determine transmission rate of the optical signal according to the number of active clients and quality of the optical signal at an optical receiver.

Abstract: Where an integrated monitoring and controlling unit is to control an optical add-drop unit so as to cause transmit signals from the optical transceiver of a first optical node to be received by the optical transceivers of plural different optical nodes, this purpose can be achieved by an optical transmission system provided with an alarm inhibiting device that can inhibit the optical transceiver, which is a source of transmission, from issuing any unexpected alarm.

Abstract: The present invention relates to an optical relay system that transmits a band-limited multi-band frequency signal via an optical line. According to an embodiment of the present invention, since a remote unit includes a multiplexer that fixes a power flow direction to combine wireless signals of various bands and outputs the combined signals to a mobile terminal, or distributes wireless signals wireless signals received from the mobile terminal and fixes a power flow direction to output the distributed wireless signals, even if frequency bands of signals combined by the multiplexer overlap or are adjacent, power delivery in a direction opposite to the power delivery direction of a signal during a signal combining process can be prevented, reducing signal distortion, and thus improving efficiency in combining a number of signals.

Abstract: An optical transmission apparatus is arranged by: means for demultiplexing monitoring light for received wavelength-multiplexed signal light so as to detect optical intensity of the monitoring light; means for detecting optical intensity of wavelength-multiplexed signal light after the monitoring light has been demultiplexed therefrom; a gain controlling type optical amplifier for amplifying the wavelength-multiplexed signal light; an optical attenuating unit for adjusting optical intensity of the amplified wavelength-multiplexed signal light; and a monitoring control unit for controlling the gain controlling type optical amplifier in such a manner that the gain of the optical amplifier becomes constant, and for controlling an attenuating amount of the optical attenuating unit in such a manner that the optical intensity of the wavelength-multiplexed signal light becomes a predetermined target value.

Abstract: Provided is an optical relay system (10) which is capable of suppressing wasteful power consumption of an entire system to a low level. The optical relay system (10) includes a plurality of relay devices (30) and a network control device (20). The network control device (20) causes an optical signal to be regenerated by a regenerative repeater (35) within the relay device (30) existing at an upstream of the relay device (30) reporting that the optical signal has deteriorated by a degree exceeding a predetermined level. Further, the network control device (20) causes the regenerative repeater (35) to stop regenerating the signal in a case where deterioration of the signal remains within an allowable range even when the regenerative repeater (35) stops regenerating the signal.

Abstract: In the WDM optical transmission system, when performing a correction of a control target value of the total light intensity per one channel of the WDM light in each node on a transmission path, a correction value calculation section of each node determines the type of its own node, and if it corresponds to a node (for example, OADM node) that demultiplexes the WDM light into individual channels and performs a predetermined processing, performs correction of the control target value of the total light intensity according to a calculation expression with use of a noise cut ratio. The noise cut ratio is defined according to a filtering characteristic for when demultiplexing the WDM light into individual channels, so that the influence due to removal of the noise components distributed across the intermediate region of each channel due to filtering is reflected in the correction processing of the control target value of the total light intensity.

Abstract: An optically amplified wavelength division multiplexing network has the functionality to add/drop channels at the optical add/drop multiplexing (OADM) nodes. The OADM node includes a receiver amplifier, an OADM module, and a transmitter amplifier. Once the OADM node detects a loss of signal (LOS) due to a fiber cut or network element failure upstream, the receiver amplifier is kept in operation as a noise source. The output of the receiver amplifier is immediately raised by increasing pump power to compensate for the LOS. The noise power received at the transmitter amplifier from the receiver amplifier is substantially equal to the signal power expected before LOS. The transient effect of downstream optical amplifiers is therefore completely suppressed and the inter-channel stimulated Raman scattering (SRS) induced spectrum tilt does not change. After the noise power is raised, the receiver amplifier may be shut down at a speed much slower than the speed of downstream amplifier control circuitry.

Abstract: The invention relates to improvements in or relating to modulation in an Optical Network, and to an apparatus, a method and a communications network for modulation in an Optical Network. An apparatus is arranged to receive a modulated optical signal comprising a carrier wavelength and first data. The apparatus is arranged to substantially erase the first data from the optical signal by performing an inversion operation on the modulated optical signal. The apparatus is arranged to receive second data and to modulate the carrier wavelength with the second data for onward transmission of the second data. The inversion operation comprises applying a signal comprising an inverse of the first data to at least a portion of the modulated optical signal. The signal may further comprise the second data such that the modulation of the carrier wavelength and erasure of the first data is performed in a single operation.

Abstract: A method and apparatus for restoration of operating conditions of a WDM optical ring network comprising a plurality of amplifiers linked together in a ring after a break or fault has occurred in the network. The method comprises in response to repair of the break or other fault, increasing output power or/and pump power of an amplifier in the network such that the output power or/and pump power increases substantially in accordance with a ramp function.

Abstract: An optical network and an optical signal modulation method thereof are provided. The optical network includes an optical fiber and a remote node (RN). The RN receives a continuous carrier wave from the optical fiber and modulates the continuous carrier wave to generate a first frequency offset carrier wave The frequency of the first frequency offset carrier wave is different from that of the continuous carrier wave. A first user device re-modulates and loads data to the first frequency offset carrier wave to generate a first upstream signal. The frequency of the first upstream signal is the same as that of the first frequency offset carrier wave. The RN inputs the first upstream signal into the optical fiber.

Abstract: An apparatus and a method for accurately detecting Loss of Optical Power (LOS) by noise power cancellation effect and optical power is measured at two output ports of an athermal periodic filter, wherein one output port in the optical frequency domain, is aligned with the signal channels of an input WDM signal (on-grid port), whereas the second output port is aligned complementary to the first output port (off-grid port). In a preferred embodiment, the apparatus computes the ratio of the measured optical powers at the two output ports of the periodic filter, and comparing them to a threshold value that is determined from the overall common-mode rejection ratio (CMRR) of the detection apparatus. In an alternative embodiment, the apparatus additionally compares the optical power measured at the on-grid port to a threshold power that is determined from system design parameters.

Abstract: According to a WDM optical transmission system of the present invention, wavelength numbers information of a WDM signal light output from an upstream side optical amplifying unit to a transmission path fiber, and signal output level information thereof are transmitted to a downstream side optical amplifying unit utilizing a supervisory control light. In the downstream side optical amplifying unit, a loss (span loss) in the transmission path fiber is computed using the upstream side signal output level information and downstream side signal input level information, so that a gain to be set for a downstream side optical amplifier is calculated based on the computed loss, and also, the gain is corrected based on a difference between a target value of the signal output level computed using the wavelength numbers information and an actual measurement value thereof, so that the optical amplifier is controlled in accordance with the post-corrected gain.

Abstract: A communication system for providing downlink and uplink communication between Service Providers, and users located in RF remotely located isolated areas, includes the sequential series connection of Service Provider signal sectors to Radio Interface Modules (RIM's), Service Combiner Units (SCU's), Fiber Transceiver Units (FTU's), Optical Multiplexer Units (OMU's), and Remote Fiber Nodes (RFN's), with only the RFN's being located in the RF isolated areas. The RIM's provide level control of RF signals bidirectional flowing between the Service Providers and SCU's. The SCU's both multiplex and split received downlink RF signals for inputting to the FTU's, and also combine and split RF uplink signals received from the FTU's for feed to the RIM's. The FTU's convert downlink RF signals into optical signals, and split the optical signals for connection to the OMU's. The FTU's also convert uplink optical signals received from the OMU's into uplink RF signals for connection to the SCU's.

Abstract: The add path of a dense wavelength division multiplexing (DWDM) add/drop node comprises an n:1 coupler for combining n signal sources. The combined signal is amplified and then demultiplexed. Each output of the demultiplexer is passed through a variable optical attenuator (VOA) and the VOA outputs multiplexed to form the add signal. Channels carrying no add signal and not used to control the added signals are attenuated to zero to remove a broadband noise contribution from those channels. The signal sources are run at maximum power and the signals of those channels are attenuated by the respective VOAs to control their amplitude and optimize the optical signal to noise ratio of the add signal.

Abstract: An optically amplified wavelength division multiplexing network has the functionality to add/drop channels at the optical add/drop multiplexing (OADM) nodes. The OADM node includes a receiver amplifier, an OADM module, and a transmitter amplifier. Once the OADM node detects a loss of signal (LOS) due to a fiber cut or network element failure upstream, the receiver amplifier is kept in operation as a noise source. The output of the receiver amplifier is immediately raised by increasing pump power to compensate for the LOS. The noise power received at the transmitter amplifier from the receiver amplifier is substantially equal to the signal power expected before LOS. The transient effect of downstream optical amplifiers is therefore completely suppressed and the inter-channel stimulated Raman scattering (SRS) induced spectrum tilt does not change. After the noise power is raised, the receiver amplifier may be shut down at a speed much slower than the speed of downstream amplifier control circuitry.

Abstract: An optical transmission apparatus comprising a first detector for detecting the power of the supervisory signal light separated from received wavelength-division multiplexed signal lights; a second detector for detecting the power of the wavelength-division multiplexed signal lights after the separation of the supervisory signal light; a gain-controlled type optical amplifier for amplifying the wavelength-division multiplexed signal lights; an optical attenuator coupled to the amplifier; and a control unit for controlling the optical amplifier and the optical attenuator so as to keep the output level of the wavelength-division multiplexed signal lights to a predetermined target value, wherein the control unit restrains automatic output level control by the optical attenuator when the supervisory signal light power fluctuates within its permissible range and fluctuations in the signal light power have deviated from its permissible range.