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WO2002063811A2 - Multiplexeur optique d'insertion/extraction a puissance equilibree et procedes d'equilibrage de puissance associes - Google Patents

Multiplexeur optique d'insertion/extraction a puissance equilibree et procedes d'equilibrage de puissance associes Download PDF

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Publication number
WO2002063811A2
WO2002063811A2 PCT/US2002/003489 US0203489W WO02063811A2 WO 2002063811 A2 WO2002063811 A2 WO 2002063811A2 US 0203489 W US0203489 W US 0203489W WO 02063811 A2 WO02063811 A2 WO 02063811A2
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WO
WIPO (PCT)
Prior art keywords
add
drop
module
path
signal
Prior art date
Application number
PCT/US2002/003489
Other languages
English (en)
Other versions
WO2002063811A3 (fr
Inventor
James E. Degrange, Jr.
Balakrishman Sridhar
Original Assignee
Ciena Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/777,774 external-priority patent/US6885825B2/en
Priority claimed from US09/777,786 external-priority patent/US6904241B2/en
Application filed by Ciena Corporation filed Critical Ciena Corporation
Publication of WO2002063811A2 publication Critical patent/WO2002063811A2/fr
Publication of WO2002063811A3 publication Critical patent/WO2002063811A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/293—Signal power control
    • H04B10/294—Signal power control in a multiwavelength system, e.g. gain equalisation
    • H04B10/296—Transient power control, e.g. due to channel add/drop or rapid fluctuations in the input power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0221—Power control, e.g. to keep the total optical power constant
    • H04J14/02216—Power control, e.g. to keep the total optical power constant by gain equalization
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0206—Express channels arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0213—Groups of channels or wave bands arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0209—Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers

Definitions

  • the present invention relates to an optical add/drop multiplexer (OADM) and a control method therefore. More specifically, the invention relates to an optical add/drop multiplexer with a controlled add amplifier and a method of controlling an add amplifier of an OADM. The invention also relates to an optical add multiplexer (OAM) and a control method therefore.
  • OADM optical add/drop multiplexer
  • OAM optical add multiplexer
  • Wavelength division multiplexing is a burgeoning field. The reason so much interest surrounds WDM is the ability to transmit a large amount of information.
  • Each of the wavelengths in a WDM system may carry in excess of 40 Gb/sec and advances in the WDM field are expected to increase the capacity of each wavelength dramatically. Moreover, the number of channels or operating wavelengths is also expected to increase dramatically.
  • a spectrally flat signal in which all of the channels have substantially the same gain is preferred because such a signal may be transmitted a longer distance without regeneration while still permitting the constituent channels to be distinguished from one another by a receiver.
  • OADM is disclosed in USP 6,069,719 (the Mizrahi patent). In that patent, a optical amplifier is placed before or after the OADM to balance or adjust the power levels of the WDM signal.
  • Drop Loss is the power loss incurred by a signal passing through an OADM module drop path.
  • Add Loss is the power loss incurred by a signal passing through an OADM module add path and
  • Through Loss is defined herein is the power loss incurred by a signal passing through an OADM module through path.
  • the present invention solves the above-identified and other problems with conventional OADMs and OAMs by providing power balanced systems and methods.
  • an optical communications apparatus for power balancing a wavelength division multiplexed (WDM) signal output from an add/drop module adding at least one channel to and dropping at least one channel from a signal input thereto, including: a gain element optically coupled to the add/drop module and to an add channel port receiving the at least one channel to be added; the gain element imparting optical gain to the at least one channel received from the add channel port; a controller operatively coupled to the gain element, the controller receiving a dropped channel power measurement of the at least one dropped channel dropped from the add/drop module; the controller determining an add path amplification value based on the dropped channel power measurement, a through loss associated with a signal passing through the add/drop module, a drop loss associated with a signal travelling a drop path of the add/drop module; and an add loss associated with a signal travelling an add path of the add/drop module; and the controller controlling the gain element according to the add path amplification value.
  • WDM wavelength division multiplexed
  • the controller may also receive a number of channels to be added by the add/drop module, a number of channels to be dropped by the add/drop module, or both. This channel count information may then be used to help determine the add path amplification value.
  • the invention may use a coupler optically coupled to a drop output of the add/drop module, an optical-to-electrical converter optically coupled to the coupler, the optical to-electrical coupler receiving a portion of light from the at least one dropped channel.
  • the controller may then determine the dropped channel power measurement from an output of the optical -to-electrical converter.
  • the controller may also receive an added channel power measurement of the least one added channel being added to the input signal by the add/drop module. The controller may then feedback control the gain element based on the added channel power measurement and the add path amplification value.
  • the invention may also use a gain element having a gain profile substantially matching a gain profile of a signal input to the add/drop module.
  • an input amplifier may be optically coupled an input port of the add/drop module and receive a plurality of input channels.
  • the gain element may be designed to have a gain profile substantially matching a gain profile of the input amplifier.
  • a drop amplifier may also be optically coupled to the drop port of the add/drop module to amplify the dropped channels.
  • an output amplifier may be optically coupled to the add/drop module to amplify the output of the add/drop module.
  • This output amplifier may also perform gain flattening amplification for the signal output from the add/drop module.
  • the controller may then control the add amplifier according to the add path amplification value.
  • the gain element may include an add amplifier and a variable optical attenuator.
  • the controller may then control the variable optical attenuator and/or the add amplifier according to the add path amplification value.
  • the invention also includes a method of power balancing a wavelength division multiplexed (WDM) signal output from an add/drop module adding at least one channel to and dropping at least one channel from a signal input thereto, including: receiving a dropped channel power measurement of the least one dropped channel dropped from the add/drop module; determining an add path amplification value based on the dropped channel power measurement, a through loss associated with a signal passing through the add/drop module, a drop loss associated with a signal travelling a drop path of the add/drop module; and an add loss associated with a signal travelling an add path of the add/drop module; and controlling an add path amplification of the add path according to the add path amplification value.
  • WDM wavelength division multiplexed
  • Fig. 1 is a block diagram of an optical add drop multiplexing system according to the invention
  • Fig. 2 is a block diagram of another optical add drop multiplexing system according to the invention
  • Fig. 3 is a block diagram of yet another optical add drop multiplexing system according to the invention
  • Fig. 4 is a block diagram of a still another optical add drop multiplexing system according to the invention
  • Fig. 5 is a block diagram of an optical add multiplexing system according to the invention
  • Fig. 6 is a high level flowchart illustrating an optical add drop multiplexer control methodology according to the invention:
  • Fig. 7 is a graph illustrating a typical optical amplifier gain profile that is useful for illustrating the concepts of the invention.
  • Fig. 8 is a graph illustrating a gain profile a signal passing through an optical add drop multiplexer after dropping channels
  • Fig. 9 is a graph illustrating a gain profile of channels to be added to a signal before amplification by an add amplifier according to the invention
  • Fig. 10 is a graph illustrating a gain profile of channels to be added to a signal after amplification by an add amplifier according to the invention.
  • Fig. 11 is a graph illustrating a gain profile of channels to be added to a signal after amplification by an alternative add amplifier according to the invention.
  • optical communicates refers to any connection, coupling, link or the like by which optical signals carried by one optical system element are imparted to the "communicating" element.
  • Such “optically communicating” devices are not necessarily directly connected to one another and may be separated by intermediate optical components or devices.
  • connection and "operative connection” as used herein is a relative term and does not require a direct physical connection.
  • controller 70 may communicate with other elements by using a communication pathway over a fiber span, an Internet connection, or wireless communication pathway.
  • Such alternative communication pathways may be convenient in view of the potentially physically distinct locations that may be provided for the various elements.
  • Fig. 1 illustrates an OADM system 10 according to a first aspect of the invention.
  • An exemplary construction of the invention, as shown in Fig. 1, includes an add/drop multiplexing (ADM) module 30.
  • the ADM module 30 may be optically coupled mid-span such as between an input amplifier 20 and output amplifier 60 shown in Fig. 1. It is to be understood that the input and output amplifiers 20, 60 are not necessary for the invention to operate and that the location of the ADM module 30 shown in the figures is exemplary in nature.
  • the ADM module 30 is, by itself, a conventional element that may be constructed in a variety of fashions including a variety of components.
  • the ADM module may be constructed with a static add/drop multiplexer as described in USP 6,069,719; with the add/drop multiplexers shown and described in US Patents 6,002,503; 5,778,118; 5,748,349; or 5,982,518; or with any other known or future-developed OADM.
  • the ADM module 30 should have the capability to add one or more channels to an available or otherwise unoccupied channel slot(s) of a WDM signal.
  • the ADM module 30 may also have the capability to drop one or more channels to make a channel slot available to the signal to be added.
  • the ADM module 30 will typically utilize wavelength selective elements such as
  • ADM module 30 Bragg gratings, thin film filters, and/or arrayed waveguide gratings to add and drop channels. While the particular construction of the ADM module 30 is largely irrelevant to the invention, a material point is that the ADM module will have various optical losses associated with the three main optical signals paths (add, drop and through).
  • the ADM module 30 has an associated Drop Loss which is the power loss associated with a signal passing through the drop path of the ADM module 30.
  • the ADM module 30 also has an associated "Through Loss" which is the power loss incurred by a signal passing through the ADM module 30.
  • the ADM module 30 also has an Add Loss associated therewith that is the power loss associated with a signal passing through the add path of the ADM module 30.
  • the drop, through, and add paths may only include the ADM module 30 as shown in Fig. 1 and the respective internal drop, through and add paths within ADM module 30.
  • the add, drop and through paths may also include other components such as connectors, isolators, and fiber situated along the respective paths and may be either internal or external to the ADM module 30.
  • the add, drop and through losses are preferably measured before the system is installed.
  • the add, drop and through losses are known, calibrated values stored within or retrievable by the controller 70.
  • the OADM system 10 also includes a drop amplifier 40 optically coupled to a drop output port of ADM module 30 and an add amplifier 50 optically coupled to an add input port of the ADM module 30.
  • the drop amplifier 40 and add amplifier 50 may be constructed with a variety of known or future developed amplifiers such as Erbium doped fiber amplifiers, other rare- earth doped fiber amplifiers, Raman amplifiers, Brillouin amplifiers or a combination thereof having one or more stages of amplification.
  • one or more pump lasers are typically coupled to the active optical fiber (e.g. rare-earth doped fiber) in one or more stages of each amplifier to excite the fluorescent material or to stimulate Raman and/or Brillouin amplification.
  • the pump light is of sufficient magnitude and the composition of optical fiber being pumped is such that the optical signals output from each stage are amplified.
  • the add amplifier 50 has a gain profile similar to the gain profile of input amplifier 20 or otherwise similar to the gain profile of a signal input to the ADM module 30. The reason for this is discussed below in more detail. Briefly, it is preferable to substantially match the gain profiles because the added channels should be amplified to match the WDM signal output from the ADM module 30 according to the concepts of the present invention.
  • Various power measurements are taken by the invention (as represented by couplers
  • Couplers 22, 42, and 52 may constructed with a conventional tap or splitter so that a small amount of light (e.g. approximately 2% of the input power fed thereto) is fed to the an optical-to-electrical (O/E) converter 72 that may be constructed with a conventional element such as a photodetector. The electrical signal may then be converted to a digital signal by analog-to-digital (A/D) converter 74.
  • O/E optical-to-electrical
  • A/D analog-to-digital
  • Controller 70 may be constructed in a variety of fashions utilizing electronic components, optical components, computer hardware, firmware, software or a combination thereof. Controller 70 may also utilize processing resources of an existing controller such as a network element controller, terminal controller, or network managing controller that already exists in the communication system to which the system 10, 1 1, 12, 13 or 14 is connected. It is to be understood that a variety of devices and methods can be utilized to measure power at certain points in the optical path and that the couplers (22, 42, and 52) shown in the figures are but one example of these alternatives. Indeed, the amps (e.g. 20, 40, 50 and 60) as well as the ADM module 30 may have the capability to measure input and output power levels and supply the measurement or a value indicative thereof to controller 70.
  • the amps e.g. 20, 40, 50 and 60
  • the ADM module 30 may have the capability to measure input and output power levels and supply the measurement or a value indicative thereof to controller 70.
  • controller 70 is supplied with various power level measurement values. Specifically, the controller 70 receives power level measurement values via couplers 22 and 42 indicative of the input power level and dropped channel power level. In the preferred embodiment, the controller 70 also receives a measurement of the actual power output from the add amp 50 via coupler 52. While coupler 52 is shown in dotted lines to indicate that this element is optional, including coupler 52 or its equivalent to measure the power output by add amp 50 permits the controller 70 to more accurately control the add amplifier 50 through a feedback loop.
  • the controller 70 also stores or receives the following values: Drop loss, Add Loss and Through Loss. As mentioned above, the Drop Loss, Add Loss and Through Loss are preferably measured or calibrated at, for example, the factory and are known (e.g. stored or received) by controller 70.
  • Controller 70 preferably operates so as to match the added channel power level with the optical signal power level output from the ADM module 30.
  • One way in which to accomplish this inventive goal is for the controller 70 to control the amplification or gain imparted by add amp 50 to the channels to be added to the WDM signal in the ADM module 30.
  • the add channel power may be calculated by determining the dropped channel power as if the dropped channels had propagated through the ADM module 30. In other words, the add channel power is based on the dropped channel power plus an offset where the offset accounts for the gains and losses associated with the dropped channels actually passing through the ADM module 30.
  • An exemplary equation to achieve this goal is as follows:
  • Offset Drop Loss + Add Loss - Through Loss (respective losses associated with a signal travelling the drop path, add path and through path of ADM module 30 in dBm)
  • P add the power per channel added (absolute power of added channels divided by number of added channels, then converted to dBm)
  • P drop is the power per channel dropped (absolute power of dropped channels as measured via coupler 42 divided by number of dropped channels, then converted to dBm) substituting Offset in Equation (1) leaves:
  • Pad d Pd r op + (Drop Loss + Add Loss - Through Loss) Equation (2)
  • the above equations are on a per-channel basis. Since ADM 30 may add more than one channel, an additional calculation may be necessary in order for controller 70 to command the appropriate output power level (add path amplification value) of the add amp 50.
  • Paddtotai Padd + 10Log N ad d Equation (3)
  • P addtota i desired amplification in dBm at output of the add amp 50.
  • N add number of added channels.
  • Paddtotai Pdrop+ (Drop Loss + Add Loss - Through Loss) + lOLog N a dd Equation (4)
  • the ADM module 30 may be replaced by an add module 32 as shown in Fig. 5 which only has the capability to add but not drop channels.
  • the add power calculation changes when no channels are being dropped. Specifically,
  • P ⁇ n the power per channel input to ADM 30 (absolute power of input channels as measured via coupler 22 divided by number of input channels, then converted to dBm)
  • OffsefNoDrop Add Loss - Through Loss
  • P a ddtotai desired amplification in dBm at output of the add amp 50.
  • N add number of added channels.
  • the controller 70 preferably has knowledge of the number of channels input, dropped and added. To that end, controller 70 may include an input 75 which inputs information relating to the number of channels being dropped and added with respect to ADM module 30. It is to be understood that a subset of this information may be sufficient for the invention to operate correctly. For example, if the ADM module 30 is symmetric and always drops and adds a fixed number of channels, then it would be sufficient to know these number(s). A controller 70 working with an asymmetric ADM module 30 generally requires both add and drop channel count information.
  • the input 75 may be from a variety of sources one of which is a service channel which may be a separate wavelength of the WDM signal separate from the data wavelengths.
  • the channel count information may be transmitted to the input 75 via a network separate from the WDM signal such as an Ethernet connection, wireless connection or WWW (world wide web) connection. If the number of channels being transmitted, dropped and added are fixed, the input 75 may simply be from a register or other memory device operatively connected to the controller 70. Still further, the channel count information may be manually input via, for example, a craft terminal connected to input 75. Input 75 may also be used to input the calibrated Drop Loss, Through Loss and Add
  • Loss values may be programmed into or otherwise stored by controller 75 without using input 75.
  • the Paddtot a i value calculated above may be used to control the add amplifier 50. More specifically, the Paddt ota i value may used by controller 70 to command the pump lasers (not shown) within add amp 50 to tune the output power to P addtota i- To increase the accuracy of the output power, a feedback loop is preferably used. To that end, an add amp 50 output power measurement is taken via coupler 52. This add amp
  • This invention contemplates using conventional feedback control methods in this new environment to achieve more precise control.
  • the gain profile of add amp 50 is for the gain profile of add amp 50 to substantially match the gain profile of the input amp 20 or otherwise substantially match the gain profile of the WDM signal input to the ADM module 30. If the input amp 20 is used, a simple way to accomplish this goal is to use the same type of amplifier for input amp 20 and add amp 50. Since the added channels typically comprise only a portion of the total WDM spectrum the gain profile match need only be with respect to the added channel spectrum and not necessarily the total WDM spectrum.
  • the output of the ADM module 30 is preferably optically coupled to an output amp
  • the output amp 60 is preferably a gain-flattened amplifier having a frequency response that substantially flattens the frequency spectrum of the signal output from amp 60.
  • gain-flattened amplifiers are generally available and typically include a plurality of amplifier stages, variable optical attenuators, gain flattening filters and the like to impart the relatively flat gain profile.
  • the inventive processing of the added channels which seeks to match the gain and frequency profile of the added channels to the channels passing through the ADM module works particularly well with a gain-flattened output amp 60. The reason is that the amp 60 need not compensate for a different power level or frequency profile for the added channels and can thereby provide a overall flatter gain response for the WDM signal.
  • the invention is not limited to the equations or examples described above in relation to Fig. 1. A variety of changes to the OADM system 10 structure and the methods performed thereby are within the scope of invention.
  • Figure 2 shows one such variation on this theme which is to add one or more dispersion compensating elements to the OADM system 11.
  • Fig. 2 is the preferred embodiment in which a first dispersion compensating element (DCE) 90 is optically coupled to the input of the ADM module 30.
  • DCE dispersion compensating element
  • Dispersion compensating element 90 provides dispersion compensation for the optical signals output from the first amp stage 20 and input to the ADM module 30 , and can include a variety of elements such as a segment of known dispersion compensating fiber (DCF) or a dispersion compensating Bragg grating or both.
  • DCF dispersion compensating fiber
  • An optional DCE 95 may also be coupled between the ADM module 30 and the drop amp 40 as also shown in Fig. 2. It is noted that a dispersion compensating element may also be provided at any appropriate location within any one of the embodiments of the present invention.
  • a variable optical attenuator (VOA) 56 may be utilized to control the add channel power.
  • the add amp 50 may be set to a relatively high amplification value that ensures sufficient amplification for the add channels. This high amplification may then be tuned by the VOA 56 to provide the desired add channel power value.
  • the controller 70 may exercise this control over VOA 56 in accordance with the descriptions above.
  • the VOA 56 may be a separate element or provided within the add amp 50.
  • Optional coupler 52 may be used to create a feedback loop to ensure that the add channel power is equal to the desired value.
  • both the add amp 50 and VOA 56 may be controlled by controller 70 to produce the desired add channel power value.
  • the controller 70 may seek to find an appropriate balance between the amplification imparted by add amp 50 and the attenuation imparted by VOA 56 to produce the desired add channel power value.
  • optional couplers 50, 52 may be used by controller to feedback control the add amp 50 and the VOA 56.
  • VOA 56 is within the scope of invention, it is generally not preferred because of the additional expense and complexity. Moreover, the necessary control over the add channel power value may be appropriately performed by the add amp 50.
  • Fig. 1 illustrates a typical interface between the ADM module 30 and the drop/add, output/input signal pathways.
  • a demultiplexer 80 is typically used to separate the dropped WDM signals into component signals which may be supplied to a receiver (Rx).
  • a multiplexer 85 is another component of a typical interface in which a plurality of signals from, for example, a transmitter (Tx) may be multiplexed into a WDM signal and supplied to the ADM module 30.
  • Such demultiplexers 80 and multiplexers 85 are conventional elements the details of which are not necessary for the understanding of the current invention.
  • Fig. 4 illustrates one of a variety of alternative interfaces. Instead of multiplexer 85 and demultiplexer 80 as in Fig.
  • the added and dropped channels may be supplied from/to another span or amplifier (e.g. the span to which add amp is connected or the amplifier 100 to which the drop amp 40 is connected).
  • the illustrated amplifier 100 and span are merely examples of interfaces and may include a variety of other components.
  • the dropped channels may be supplied to another span or fiber plant for transmission. If there is more than one dropped channel, the signal being supplied will be a WDM-type signal.
  • Fig. 4 also illustrates a generalization of the add amp 50 and add amp 50/VOA 56 illustrated in previous figures.
  • This generalized version is labeled a gain element 58 and may include an add amp 50 as in Figures 1-2, a combination of add amp 50 and VOA 56 as in Figure 3 or any other combination of amplifiers and attenuators capable of adjusting the add path amplification in response to a command from controller 70.
  • the gain element 58 may also be feedback controlled by controller 70 using the power measurement taken via coupler 52.
  • the drop amplifier 40 is not necessary for the invention to operate. In other words, the focus of the present invention is on the add path amplification and the drop path amplification is a useful, albeit not strictly necessary, addition to the invention.
  • Fig. 6 is an example of the method performed by the invention. This method may be performed by controller 70 to control the add amp 50, the VOA 56 or gain element 58. As shown in Fig. 6, the inventive method includes monitoring the ADM 30 input power and the drop channel power. This may be accomplished as described above and involves measuring power via couplers 22 and 42.
  • the ADM input power does not need to be monitored if the ADM module 30 drops at least one channel. Furthermore, the dropped channel power does not need to be monitored if the ADM module 30 does not drop any channels.
  • the method also inputs the drop, add and input channel counts. As discussed above, only a subset of this information may be necessary such as just the add and drop channel counts.
  • the method may then calculate the desired add path amplification value. This calculation may be performed as described above.
  • An optional step may then be performed to determine whether any significant changes to the monitored or input values have occurred.
  • the degree of change sufficient to trigger a calculation and add amplification update may be adjusted or eliminated entirely to tune the system performance.
  • the degree of change may be detected by tracking or otherwise storing previously monitored or input values.
  • the change may relate to only one or a subset of the all values monitored or input. For example, at least a 2% change in the dropped channel power may be deemed a "significant" change meriting controlling the add path amplification to reach an updated value.
  • the method changes the add path amplification by controlling the add amp 50 and/or the VOA 56.
  • the method may continue in this fashion or may be triggered upon the occurrence of an event (e.g. the
  • Figs. 7-11 further illustrate the concepts of the invention.
  • Fig. 7 is a typical gain profile of a signal input to the ADM module 30. This gain profile may be preexisting (e.g. in case input amp is not used) or imparted by the input amp 20 if part of the system.
  • the gain profile shown in Fig. 7 is but one, non-limiting example of a typical gain profile of a WDM signal.
  • Fig. 8 illustrates a typical gain profile of the WDM signal passing through ADM module 30 after dropping one or more channels onto the drop path. As shown therein, a gap in the profile exists and corresponds to the channel(s) that were dropped.
  • Fig. 9 illustrates the channels to be added before amplification.
  • the added channel(s) output from the multiplexer 85 may have a gain profile as shown in Fig. 9.
  • the gain profile is flat but that is not always the case.
  • Fig. 10 illustrates the result of the inventive processing which is to match the power level and gain profile of the WDM signal.
  • the channels to be added (Fig. 9) are amplified by amp 50 to a level determined by controller 70. If the preferred add amp 50 is used having a gain profile that substantially matches the gain profile of the WDM signal input to the ADM module 30, then the added channel(s) output from add amp 50 will preferably look like those shown in Fig. 10.
  • the preferred result is that the combined signals (WDM signal after dropping and adding channels) will appear as shown in Fig. 7.
  • the ADM 20 will appear power-transparent and insensitive to changes in the number of channels input, dropped, or added and or changes in the respective power values of the input, dropped, and added channels.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optical Communication System (AREA)

Abstract

Pour améliorer l'équilibre d'un multiplexeur optique d'insertion/extraction on couple optiquement un amplificateur d'insertion à la voie d'insertion d'un module d'insertion extraction. On connaît déjà ou on a déjà paramétré: la perte de transit associée au signal traversant le module d'insertion/extraction, la perte d'extraction associée au signal traversant la voie d'extraction du module d'insertion/extraction, et la perte d'insertion associée au signal traversant la voie d'insertion du module d'insertion/extraction. On utilise une mesure de la puissance du canal extrait en association avec la perte de transit la perte d'insertion, la perte d'extraction, le nombre de canaux extraits et le nombre de canaux insérés pour déterminer la valeur de l'amplification de la voie insérée. Le gain de l'amplificateur d'insertion est réglé en fonction de la valeur de l'amplification de la voie insérée pour que le niveau de puissance du ou des canaux insérés corresponde sensiblement à celui du signal MRL de sortie du multiplexeur d'insertion/extraction. En outre le profil de gain de l'amplificateur d'insertion correspond de préférence à celui du signal d'entrée du module d'insertion/extraction. Ainsi, le niveau de puissance et le profil de gain du ou des canaux insérés peut être réglé de manière à correspondre à ceux du signal traversant le module d'insertion/extraction.
PCT/US2002/003489 2001-02-06 2002-02-06 Multiplexeur optique d'insertion/extraction a puissance equilibree et procedes d'equilibrage de puissance associes WO2002063811A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US09/777,774 US6885825B2 (en) 2001-02-06 2001-02-06 Power balanced optical add/drop multiplexer and power balancing methods therefore
US09/777,774 2001-02-06
US09/777,786 US6904241B2 (en) 2001-02-06 2001-02-06 Power balanced optical add multiplexer and power balancing methods therefore
US09/777,786 2001-02-06

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GB2378070A (en) * 2001-03-21 2003-01-29 Nec Corp Setting a level of an add signal in an optical add-drop multiplexer (OADM)
EP1394976A1 (fr) * 2002-08-30 2004-03-03 Alcatel Procédé de commande de puissance de canal dans un système WDM
US6885825B2 (en) 2001-02-06 2005-04-26 Ciena Corporation Power balanced optical add/drop multiplexer and power balancing methods therefore
US6904241B2 (en) 2001-02-06 2005-06-07 Ciena Corporation Power balanced optical add multiplexer and power balancing methods therefore

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9516017D0 (en) * 1995-08-04 1995-10-04 Stc Submarine Systems Ltd Optical level control in wavelength add-drop multiplexing branching units
GB2347809B (en) * 1999-03-12 2001-06-20 Marconi Comm Ltd Signal transmission system
US6904241B2 (en) * 2001-02-06 2005-06-07 Ciena Corporation Power balanced optical add multiplexer and power balancing methods therefore
US6885825B2 (en) * 2001-02-06 2005-04-26 Ciena Corporation Power balanced optical add/drop multiplexer and power balancing methods therefore

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6885825B2 (en) 2001-02-06 2005-04-26 Ciena Corporation Power balanced optical add/drop multiplexer and power balancing methods therefore
US6904241B2 (en) 2001-02-06 2005-06-07 Ciena Corporation Power balanced optical add multiplexer and power balancing methods therefore
GB2378070A (en) * 2001-03-21 2003-01-29 Nec Corp Setting a level of an add signal in an optical add-drop multiplexer (OADM)
GB2378070B (en) * 2001-03-21 2004-04-07 Nec Corp Device and method for setting a level of an added signal in an OADM system
US7280761B2 (en) 2001-03-21 2007-10-09 Nec Corporation Device and method for setting add signal level for OADM system
EP1394976A1 (fr) * 2002-08-30 2004-03-03 Alcatel Procédé de commande de puissance de canal dans un système WDM

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