Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0226—Fixed carrier allocation, e.g. according to service
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
  • H04J14/0228—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths
  • H04J14/023—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths in WDM passive optical networks [WDM-PON]
  • H04J14/0232—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths in WDM passive optical networks [WDM-PON] for downstream transmission
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
  • H04J14/0238—Wavelength allocation for communications one-to-many, e.g. multicasting wavelengths
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
  • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
  • H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
  • H04J14/0245—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU
  • H04J14/0247—Sharing one wavelength for at least a group of ONUs
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
  • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
  • H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
  • H04J14/0249—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for upstream transmission, e.g. ONU-to-OLT or ONU-to-ONU
  • H04J14/0252—Sharing one wavelength for at least a group of ONUs, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/22—Adaptations for optical transmission
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0278—WDM optical network architectures
  • H04J14/0282—WDM tree architectures

Definitions

• Device for optical communication comprising an integrated optical combining module and an optical communication system provided with such a device
• the invention relates to a device for optical communication comprising an integrated optical combining module which comprises connection means for exchanging information signals with several end station connections in a bidirectional manner, receiving means for receiving and passing on one or several broadcast/multicast signals, splitting means for distributing said one or several broadcast/multicast signals over said end station connections, and combining means for combining said information signals and said one or several broadcast/multicast signals for each end station connection, all the above as recited in the pre-characterizing part of claim 1.
• an integrated optical combining module which comprises connection means for exchanging information signals with several end station connections in a bidirectional manner, receiving means for receiving and passing on one or several broadcast/multicast signals, splitting means for distributing said one or several broadcast/multicast signals over said end station connections, and combining means for combining said information signals and said one or several broadcast/multicast signals for each end station connection, all the above as recited in the pre-characterizing part of claim 1.
• Such a device is used in particular as a module in a point-to-point fiber-based architecture for connecting individual residences, subscribers, and the like to sources of TV signals, other broadcast signals, other multicast signals, and even point-to-point signals.
• the end stations in that case are connected together therewith to information networks with individual communication paths such as Ethernet, the latter networks then being logically separated from the categories mentioned earlier, such as TV.
• this separation is preferably centrally implemented for the decentralized equipment of the users or subscribers, while the cabling to the latter should be as simple as possible.
• each CATV "packet” would then have its own specific wavelength (band) or "color” on which the packet and the like is superimposed.
• a simple implementation would be one with an on/off switch.
• Tuning and filtering is preferably achieved with a compact (dense) tunable filter (DWDM) according to a division as to wavelength.
• DWDM compact (dense) tunable filter
• An advantageous idea is to introduce the plurality of provider information streams into the optical combining module in accordance with a compact wavelength grid, for example an International Telecom Union (ITU) grid with 50, 100, or 200 GHz spacings between the individual wavelength channels.
• a compact wavelength grid for example an International Telecom Union (ITU) grid with 50, 100, or 200 GHz spacings between the individual wavelength channels.
• One or several client-specific wavelengths are then filtered out so as to pass on to a triple WDM stage (cf. Fig. 6) on the integrated chip and hence to the client. Filtering is controlled by means of a voltage supply to the component.
• the DWDM filter may be an interferometer with one or several stages based on a Mach-Zehnder interferometer or other switching element, or on a micro-ring resonator.
• thermo -optical switching is based on a change in refractive index in a material caused by a stepwise change of an ambient temperature.
• the heat is supplied, for example, by a film heater that converts an applied electric current into a rise in temperature.
• the device according to the invention is characterized in that switching means are provided which are connected to the splitting means downstream thereof for selectively passing on said one or several broadcast/multicast signals under the control of externally supplied control signals, as recited in the characterizing part of claim 1.
• the combining means and switching means act so as to allow said one or several broadcast/multicast signals to pass superimposed on respective frequency- specific color carrier signals.
• the switching means may thus also comprise filters, while each carrier wave frequency represents a respective color.
• the splitting means are preferably connected to a measuring device for determining/detecting whether a function in a connection and/or end station has been selected through the action of said switching means.
• the determination can be carried out selectively as well as automatically, and possibly with a selectable repetition frequency, because of the selectivity provided by the switching means, which makes for a greater simplicity, speed, and effectiveness.
• the measuring device is preferably based on the principle of an optical time domain reflectometer (OTDR), so that a state and/or quality of the connection can be selectively determined/detected for each end station connection through detection of the dynamic reflection behavior in time. Any errors and the like that occur can now be quickly detected and localized by the controllable switching means for a large number of stations without mechanical intervention.
• ODR optical time domain reflectometer
• the respective provider streams in a network infrastructure are subsequently multiplexed with one another, for example before they reach an optical amplifier, but it is also feasible to do this the other way round.
• the expensive optical amplifier is preferably integrated together with the other circuitry on a single carrier, which can then serve a number of end stations. This may be implemented, for example, as a separate multichannel compact multiplexer based on wavelength division or as a multichannel combiner. All provider streams are thus amplified by the same optical amplifier. This is advantageous in particular because this amplifier is a very expensive component.
• the multiplexed and amplified information stream is then fed to the integrated combining module which comprises, for example, tunable filter elements.
• the invention also relates to an optical communication system comprising a device with an integrated optical combining module connected so as to receive several broadcast or multicast signals and to communicate information signals bidirectionally with several end stations, as recited above.
• This will require substantially less space in many cases compared with solutions realized in the prior art. In particular, controlling becomes simpler because the switching means are centrally controlled by a management platform.
• Optical amplifier means are preferably present in a range upstream of the one or several broadcast/multicast signals.
• a unity gain amplifier in particular can strongly reduce the sensitivity to disturbances and the like.
• such a system is placed in a Central Office in order to be connected through from there to underground end station terminals, in particular when placed in the limited space of an Optical Distribution Frame.
• the integration offers the possibility to arrange many elements close together, whereby the number of splices is drastically reduced. Further advantageous aspects of the invention are recited in the dependent claims.
• Fig. 1 gives an overall view of a known network structure for Ethernet/CATV
• Fig. 2 shows a modification of Fig. 1 with a single fiber per subscriber
• Fig. 3 shows a known distribution mechanism for CATV with combined WDM
• Fig. 4 shows an improved distribution mechanism with controlled DWDM (Dense Wavelength Division Multiplexing) filters
• Fig. 5 shows a further improved distribution mechanism with controlled switches for
• Fig. 6 shows a detailed design for a WDM filter
• Fig. 7 shows the use of the invention with an OTDR (Optical Time Domain Reflectometer) or other measuring device.
• OTDR Optical Time Domain Reflectometer
• Fig. 1 gives an overview of a known network structure for Ethernet/CATV. Broadcast, multicast, and similar signals may be present instead of CATV, possibly even provided with a return path belonging to the broadcast/multicast.
• Each "client" or end station terminal 26 herein is connected via a two-wire system 24 to an access switch 20 for cable TV and a splitter 22 for the information network. Further present are, if applicable: a control module 28, a through passage 30, a firewall module 32, a PSTN gateway 34, an SIP proxy 36, a 1550-nm band transceiver 38, and an optical EDFA or some other type of amplifier module 40. All these elements are known from the prior art.
• the client 26 may be one out of several who are jointly connected via the pair 24, while the access switch 20 and the splitter 22 may be connected to several such pairs, and the through passage 30 and EDFA 40 may be connected to several access switches 20 and EDFAs 40, respectively. Further elements (not numbered) are equivalent to similar elements which have been similarly represented.
• the output frequencies lie in the 1550-nm band and the input frequencies in the 1310-nm band, as shown. As is apparent, the control is accommodated in the central office 18.
• Fig. 2 shows a modification of Fig. 1 with only one fiber 44 per subscriber. The output frequency then moves to the 1490-nm band, while the splitters are replaced by splitters/combiners 42 which are connected to the respective access switches 20.
• Fig. 3 in this connection illustrates a distribution mechanism for CATV and the like known from the patent application cited above with combined WDM (Wavelength Division Multiplexing) filters 50, 51, 52, 53 which act as combining means.
• Figs. 1 and 2 Fig. 3 shows a connection 23 for the CATV signal at 1550 nm with an optical interface 23a, all of which is to be connected to the optical amplifier 40 of Fig. 1, and a splitter 22 as shown above.
• Ethernet connections 59 which are connected to the filters 50, 51, 52, 53 via a distributor 54, for the respective end stations.
• Fig. 4 illustrates how, according to an aspect of the invention, selective transmission takes place by means of DWDN (Dense Wavelength Division Multiplexing) filters 60, 61, 62, 63 which are controlled by externally supplied control signals 64, for example from a central management platform, and which at the same time act as switching means.
• DWDN Dense Wavelength Division Multiplexing
• the transmissivity of these switching means may be set to suit a plurality of desired transmission patterns, so that the end stations can receive corresponding selections of the broadcast/multicast signals.
• Connection to the Ethernet terminals 75, 76, 77, 78 takes place separately for each end station terminal via the filters 50, 51, 52, 53. Since the switch-over is allowed to take place at a low speed, it is possible to use for this purpose, for example, a comparatively slowly acting thermo -optical effect: raising the temperature changes the refractive index of an optically active substance.
• a thin- film heater element may for this purpose be applied on the switching element, for example an interferometer or a resonator. In such a case the filters 60, 61, 62, 63 selectively control a blocking of the CATV signals.
• the control 64 thereof may accordingly have a greater number of discrete states.
• Fig. 5 shows an alternative, improved distribution mechanism with controlled switches 65, 66, 67, 68 for CATV and the like.
• the switches again receive an energizing signal 64 so as to make them non-transmitting (65), otherwise they are transmitting (66, 67, 68) in the absence of said received energizing signal.
• the subscriber will then always receive a CATV signal, which reduces the occurrence of subjectively annoying disturbances: the subscriber will in general find the absence of a TV signal immediately annoying, which will occur less readily in relation to the information link. This is true is particular for subscribers who pay for the TV link.
• the switch may be constructed as a bistable element that switches over only upon receiving an actuation current (pulse) and remains otherwise unchanged.
• the splitter 22 may be constructed as a cascade of 1 :2 splitter elements, which is not specifically shown for simplicity's sake.
• Fig. 5 further shows an optical amplifier 90 which again may be arranged for several sources 80 (Fig. 4). It may be an erbium-doped fiber amplifier (EDFA) or a semiconductor optical amplifier (SOA), or alternatively an optical amplifier of a different type.
• EDFA erbium-doped fiber amplifier
• SOA semiconductor optical amplifier
• the component shown will usually have a considerable loss of signal strength owing to the presence of the splitter, switching elements, and WDM filters.
• the optical amplifier compensates this loss and may be, for example, a unity gain amplifier.
• the amplifier may obviously be differently located in the signal path.
• Fig. 6 illustrates a detailed design for a WDM filter.
• the black lines represent optical waveguides provided on a carrier or substrate.
• the connection 90 was active in receiving at 1310 nm and transmitting at 1490 nm.
• the double filter 92 operating on the Mach-Zehnder principle transmits at 1490 nm (in fact from 1480 to 1500 nm) and 1550 nm to the right and at 1310 nm to the left. A comparatively great bandwidth is possible owing to the double design.
• the wavelength of 1310 nm is in fact a central wavelength covering a range of 1260 to 1360 nm.
• a further filter 94 blocks the wavelength of 1310 nm to the left, but effectively transmits the wavelength of 1550 to the right. This latter transmission in particular is allowed to have only very low losses. The losses are less critical for the other wavelengths (data traffic).
• the optical waveguides are connected via splices (not shown) to fibers extending outside the module.
• a single carrier semiconductor substrate or otherwise
• dimensions of the order of 2x6 cm may be designed to accommodate a larger number of filters, for example 16, according to the principle of Fig. 6. Since the dimensions are small, the elements shown may be arranged immediately before the point where the fiber cables disappear underground.
• Fig. 7 illustrates the use of the invention in conjunction with a measuring device such as, for example, an OTDR (Optical Time Domain Reflectometer).
• the circuit comprises an OTDR 110, a splitter 112 as discussed with reference to Fig. 4, a (large) number of subscriber units 114, and an interruption 116 or other source of excessive signal reflection in the fiber wiring, splices, and the like to one of the subscribers.
• the tunable or switchable filter elements as described above have not been shown in detail for simplicity's sake.
• the elements such as 110 are known per se and are used for determining the state and quality of the fiber connections and the connectors, splitters, etc. included therein.
• a very short light pulse is sent into the fiber for this purpose, and the occurring reflections are determined as a function of time.
• the location and gravity of any discontinuities and the like can be determined from this time-dependent behavior. If the connection on which the discontinuity occurs is also to be identified, the reflectometer must be connected to all individual fibers consecutively. This is obviously time-consuming.
• an integrated optical combiner module is used for this. This may be achieved in that the specific wavelength of the OTDR is tuned to a channel or in that the WDM filters are consecutively switched on/off, such that one connection can be selectively monitored each time without any manual or mechanical on/off switching action being required.
• a total broadcast or multicast system can be temporarily converted into a point-to-point connection.
• the signals are combined with the total broadcasting system, and accordingly the status of the entire network can be measured from a central location.
• the component 110 may be realized as a permanent component in the network and may be connected to several optical combiner modules, if so desired, for example by a switching matrix.
• the optical combiner with tunable elements is used, because in that case the OTDR is realized with its own, highly specific wavelength band.
• the optical combiner module with the on/off switching facility is used, this module can replace the total CATV broadcast signal by means of the switching matrix. The implementation thereof may take place in a usual manner. It is further apparent from the previous Figure(s) that the static WDM filters here are not a necessary condition for the combining of the CATV/OTDR signals in this application of a measuring device.

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• Signal Processing (AREA)
• Computer Networks & Wireless Communication (AREA)
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Cited By (1)

Citations (3)

• 2008
  • 2008-09-03 NL NL2001948A patent/NL2001948C/nl not_active IP Right Cessation
• 2009
  • 2009-08-25 WO PCT/EP2009/060948 patent/WO2010026083A1/en active Application Filing

Patent Citations (3)

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