WO2006109292A1

WO2006109292A1 - Merging foreign optical channels in an optical communication network

Info

Publication number: WO2006109292A1
Application number: PCT/IL2006/000399
Authority: WO
Inventors: Eyal Lichtman; Uri Mahlab
Original assignee: Eci Telecom Ltd.
Priority date: 2005-04-13
Filing date: 2006-03-30
Publication date: 2006-10-19

Abstract

A technology is described for interlacing communication traffic carried along one or more foreign optical channels with communication traffic carried along an optical network, which network is adapted to handle a pre-defined number of original optical channels and characterized in that no communication traffic is being conveyed along one or more non-operative channels among the pre-defined number of optical channels. The technology comprises adapting at least one parameter (such as wavelength, power, chromatic dispersion, pilot tone) characterizing optical signals transmitted along the one or more foreign channels, so as to bring the parameter(s) into conformity with respective at least one parameter characterizing optical signals to be transmitted along the original optical channels. The adaptation is performed at the optical layer of the optical network.

Description

MERGING FOREIGN OPTICAL CHANNELS IN AN OPTICAL COMMUNICATION NETWORK

Field of the invention The present application relates to handling multi-channel optical signals in WDM (wavelength division multiplexing) communication optical networks.

Background of the invention

Majority of the modern WDM communication equipment, such as Multiplexers, Demultiplexers and OADMs (Optical Add Drop Multiplexers) are designed by manufacturers so as to perform monitoring and identifying the incoming/outgoing optical channels. The monitoring is usually provided for various purposes, for example such as performance monitoring in the network, channel count, etc. US published patent application 2004/0109685 Al describes an OADM comprising a demultiplexer wherein each optical channel is being marked with a pilot tone for channel identification and monitoring. The pilot tones are detected, cleaned from ghost tones, and then re-inserted in the respective optical channels being fed into the multiplexer of the OADM, for multiplexing said optical channels into a WDM output signal.

US patent 6735395 describes a WDM communication system utilizing WDM optical sources with stabilized wavelengths. Efficient stabilization of these characteristics is achieved by modulation of WDM sources by distinguishing low frequency electrical signals that are used as WDM source identifiers. WDM equipment that implements the above-mentioned identifying pilot tones for monitoring, actually uses "proprietary marks" and therefore becomes unsuitable for integrating it with different networks and with "foreign" equipment (say, equipment of other manufacturers). Volens-nolens, such "proprietary marks" may serve the purpose of protecting monopoly of a specific vendor in areas and networks occupied by communication equipment purchased from that vendor. This problem prevents a service provider from freely utilizing capabilities of the existing network, and sometimes from expanding the network in a desired manner.

Moreover, a number of important parameters of an optical signal transmitted along the foreign channel may be and usually are unsuitable to ranges of the respective parameters accepted for the original equipment. In such circumstances, the foreign channels are incompatible with the WDM original equipment. Object and summary of the invention

It is therefore the object of the present invention to provide an easy technique for using/ integrating so called foreign (non-conventional, non-original, different) equipment in existing optical networks (i.e., those served by existing "original" or "conventional" equipment).

The above object can be achieved by a method for interlacing communication traffic carried along one or more foreign optical channels with communication traffic carried along an optical network adapted to handle a pre-defined number of original optical channels and characterized in that no communication traffic is being conveyed along one or more channels, called non-operative, of said pre-defined number of optical channels; the method comprises: adapting at least one parameter characterizing optical signals transmitted along the one or more foreign channels so as to bring said at least one parameter into conformity with respective at least one parameter characterizing optical signals to be transmitted along the original optical channels, wherein said at least one parameter being selected from among: wavelength, power, chromatic dispersion, pilot tone, and wherein said adapting is performed at the optical layer.

Preferably, the adapting of the at least one parameter of optical signals transmitted along the one or more foreign channels is carried without prior converting said optical signals into their electrical form.

The method can be used for various optical networks, for example OTN (Optical Transport Network), but is most advantageous for WDM (Wavelength Division Multiplexing) optical networks.

It should be noted that for solving such a problem, optical transponders that perform the expensive 0/E/O conversion have been widely utilized in the prior art systems. In the frame of the present patent application, the foreign channels are intended to be introduced into the original optical network (say, via its coupler, multiplexer Optical Add Drop Multiplexer, etc.), without using an optical transponder (OEO).

The original optical channels should be understood as multiple optical carrier wavelengths that, according to the presently actual configuration are pre-occupied for transmitting and processing informational optical signals (_^communication iraiπc; uy the original optical network equipment, usually WDM equipment.

The original WDM equipment should be understood as equipment originally installed in the WDM network; it comprises at least one of the equipment pieces listed below: laser sources of the wavelength earners combined with modulators, couplers, multiplexers, demultiplexers, OADMs, i.e. the equipment units being operative to produce, receive or process optical signals over original optical channels, within ranges of parameters accepted for the original equipment (vendor), and also operative to insert, monitor, and/or detect in the respective signals "proprietary marks" such as dither or pilot tones .

In the further description, the non-operative channels may be called vacant or additional channels. Such channels can be preliminarily freed before introducing the one or more foreign channels in the optical network.

The foreign channels should be understood as optical channels originating from equipment different from the original (existing) optical network equipment.

Such different equipment usually belongs to another vendor or another system, and can be called "foreign equipment". The foreign optical channels (i.e., the optical signals transmitted there-along) usually have values of at least one of the mentioned parameters different from those accepted for the communication traffic carried along the original optical channels.

In the widely used and preferred case, the original WDM equipment utilizes

ITU-T standard recommendation G.694.1 "Spectral grid for WDM applications" and therefore all the original (including the non-operative or vacant) channels have strictly defined wavelength ranges. In this case, the foreign channels must either initially use the wavelengths ranges standardized by the same standardization body, or be in principle adjustable to such wavelengths ranges. In one specific case, the foreign channels wavelengths are respectively similar to those of the non-operative

(additional) channels; however, one may not rule out a possibility of performing wavelength conversion of the optical carrier in the foreign channel before feeding thereof to the WDM network.

Most preferably, the method comprises a preliminary step of monitoring the one or more foreign channels to allow evaluation of said one or more parameters, and further adapting thereof in a controlled manner. In one particular case, at least one (but preferably eacnj υi uic pic-ucimtu number of original optical channels is associated with an original pilot tone; in this case the method comprises: selecting one or more pilot tones respectively suitable for the one or more non-operative channels, said pilot tones being called additional pilot tones, modulating the traffic conveyed along said one or more foreign channels with corresponding one or more additional pilot tones (thereby respectively imitating original channels of the optical network), and interlacing communication traffic conveyed along said one or more foreign channels carrying said respective one or more additional pilot tones with communication traffic carried along said original optical channels in the place of said respective one or more non-operative channels.

The original pilot tones are usually utilized for identification and monitoring the channel by original WDM equipment of the WDM network.

Preferably, the step of modulating is performed by activating a variable optical attenuator (VOA) switched in the foreign channel and controlling the VOA according to the selected corresponding additional pilot tone. Such operation allows modulating attenuation of the optical signal transmitted via the foreign channel, and therefore enables simple and cheap integration of different types of equipment (say, without manipulating the laser source of the foreign channel).

In the present description, the foreign optical channels convey optical signals generated by equipment different from the original (existing) equipment, over optical wavelengths, which (preferably) are substantially and respectively identical to those of the additional channels. In the above-mentioned particular version of the method, the optical signals transmitted along the foreign channels do not carry the pilot tone(s) intrinsic for the original equipment. In one version of the method, especially when different original pilot tones are used for different original optical channels in the optical network, the additional pilot tones can be determined by processing (say, by extrapolation —possibly computerized) of information or knowledge about one or more original pilot tones. For example, frequency of a particular additional pilot tone can be obtained based on the frequency of a first original pilot tone and a particular coefficient, wnicn - Dotn or at least one or them-can be either preliminarily known or determined by monitoring.

Therefore, the step of determining the additional pilot tone(s) may comprise a preliminary sub-step of monitoring said one or more original pilot tones for obtaining the information about them.

In a simple and most preferred version of the method, the step of selecting the additional pilot tone(s) comprises determining a single original pilot tone in a single original channel (say, by monitoring the single original channel), and the step of modulating said one or more foreign channels comprises applying to each of the optical signals transmitted along the one or more foreign channels, an additional pilot tone identical to said determined single original pilot tone.

According to one version of the method, it further comprises a step of carrier frequency adaptation prior to interlacing the communication traffic conveyed along the one or more foreign optical channels with the original optical channels in the optical network. In other words, the carrier wavelength of a specific foreign channel should be adjusted (shifted) so as to be essentially equal to the carrier wavelength characteristic for a suitable, presently non-operative channel of the optical network.

According to an additional or alternative version of the method, it comprises a step of power adaptation of optical signals transmitted via the one ore more foreign optical channels, and includes an operation of controlled amplifying and/or an operation of controlled attenuating performed selectively on the optical signal(s) of said one or more foreign channels, and preferably prior to interlacing thereof with the traffic conveyed along the original channel(s) of the optical network. According to yet another version of the method, it includes adapting the one or more foreign channels from the point of chromatic dispersion, and comprises a step of controlled compensation of dispersion in the optical signal(s) conveyed along said one or more foreign channels, while integrating thereof into the optical network. The treatment from the point of dispersion can preferably be performed immediately prior to or immediately after the foreign channel(s) introduction into the optical system.

According to a second aspect of the invention, there is proposed a system for interlacing communication traffic carried along one or more foreign optical channels with communication traffic carried along an optical network adapted to handle a predefined number of original optical channels and characterized in that no communication traffic is being conveyed along one or more channels, called non- operative, of said pre-defined number of original optical channels, the system comprising means for adapting at least one parameter characterizing optical signals transmitted along said one or more foreign channels, so as to bring said at least one parameter into conformity with respective at least one parameter characterizing optical signals to be transmitted along the original optical channels, wherein said at least one parameter being selected from among: wavelength, power, chromatic dispersion, pilot tone, and wherein said system being operable to perform the adaptation at the optical layer.

Preferably, the system is capable of adapting said at least one parameter of optical signals transmitted along the one or more foreign channels without prior converting said optical signals into their electrical form.

Preferably, the optical network is a WDM network. When the original channels of the WDM network are defined according to ITU-T standard recommendation G.694.1, the system is capable of introducing traffic (optical signals) conveyed along the foreign channel(s) in the place of said one or more respective non- operative channels.

Further preferably, the system is arranged in the form of a module for interlacing communication traffic carried along said one or more foreign channels into said optical network, wherein the module is capable of adapting said at least one parameter of optical signals transmitted along the one or more foreign channels. Further preferably, the module suits for adapting said at least one parameter immediately before introducing the foreign channels into the optical network.

Preferably, the system further comprises a monitoring unit for monitoring said at least one parameter characterizing optical signals conveyed along the one or more foreign channels, the system thereby ensuring evaluation of the parameters and adaptation of the. foreign channels having said parameters changing in time.

In one preferred embodiment, the system is adapted to introduce one or more pilot tones (additional pilot tones), being suitable for the respective one or more non- operative (vacant) channels, in the one or more foreign channels respectively, to allow interlacing the foreign channels in the optical network. According to one preferable embodiment of the system, the above operations can be performed by said module.

The system (say, in the form of the above module) may then comprise a control and processing block (CP) and a modulation block controllable by said CP, wherein: said CP block being capable of selecting one or more pilot tones called additional tones, respectively suitable for the one or more non-operative channels, based on information about original pilot tones characteristic for said original optical channels, and also capable of controlling the modulation block in response to the selected one or more additional pilot tones, the modulation block being operative to modulate optical signals transmitted along the one or more foreign channels according to the selected one or more additional pilot tones.

The mentioned information about original pilot tones can be obtained by various means; say, it can be entered in the CP block in advance, or be obtained by monitoring the original optical channels.

According to one embodiment, the system further comprises a monitoring block, said CP block being in communication with the monitoring block and the modulation block, said monitoring block being adapted to monitor one or more of said original pilot tones and to provide the infoπnation about them to said CP.

The modulation according to the selected additional pilot tone(s) is preferably performed by one or more controlled variable optical attenuators (VOAs) switched in the respective one or more foreign channels before connecting them to input ports of the original WDM equipment. In this embodiment, the VOAs play part of controlled modulators; however, they may also operate as power regulators/adapters. Alternatively or in addition, the proposed system may comprise a configurable matrix having a first plurality of input ports and a second plurality of output ports, wherein at least one of the input ports is connectable to an incoming fiber, at least one of the output ports is connectable to an outgoing fiber, and a number of adaptation blocks are associated with said matrix, wherein each of said adaptation blocks being capable of adapting at least one parameter of an optical signal passing there-through, and is connected between at least one input port and at_.least one output port of the matrix; ana wnerem trie matπx being configurable in such a way mai an optical signal transmitted along a foreign channel via the incoming fiber, is directed to pass through at least one of said adaptation blocks in a desired order and to be outputted via the outgoing fiber in the form acceptable by the optical network. The proposed method and system are advantageous in that they give a simple and inexpensive solution to increase flexibility of optical networks (for example, WDM networks) from the point of integrating equipment of different types and vendors. The proposed technique is effective even in cases when optical signals in the foreign channels have changeable parameters, and in cases when parameters of optical signals in the original channels are changed or alter in any manner (periodically from time to time or randomly); the technique ensures that the required parameters, for example additional pilot tones, be dynamically updated to stay suitable to the original optical network, so that the foreign channels will remain compatible to the network in any circumstances.

Brief description of the preferred embodiments

The invention will further be described in detail with reference to the following non-limiting drawings in which:

Fig. 1 illustrates an exemplary block diagram of one embodiment of the invention.

Fig. 2 illustrates an exemplary block diagram of another embodiment of the invention.

Fig. 3 illustrates a schematic block diagram of an exemplary implementation of the proposed inventive system or module.

Detailed description of the preferred embodiments

Fig. 1 illustrates an embodiment of a system 10 that allows integrating one or more foreign channels to a piece of original WDM equipment 12 (being a multiplexer MUX, Optical Add Drop multiplexer OADM, a coupler, etc.). For the sake of simplicity, let the block 12 is configured to receive three original optical channels λl, λ2 and λ3, while it is capable of multiplexing additional channels λk and λk+1 which are presently vacant or have been freed. Original equipment of the WDM network, being laser transmitters 14, 16 and 18 respectively generate optical signals via the cnanneis Ai, Ki and Ki, and impresses (applies) ontυ me Mgiuub icbpcuuvc iυw frequency pilot tones fl, £2 and β. Let the service provider of the WDM network is interested in interlacing therein two foreign channels, which are transmitted using wavelengths that can be received by the block 12. For example, such wavelength are the respective wavelengths of additional optical channels λk and λk+1. In Fig. 1, the foreign channels are transmitted from non-original (foreign) transmitters equipment (Tx)k (22) and (Tx)k+1 (24). Since the foreign equipment does not ensure all those parameters of optical signals, which are accepted in the original WDM equipment, the system 10 performs adaptation of the foreign channels by means of: a) introducing one or more adapting blocks in the incoming foreign channel (two controllable adapting blocks 23 and 25 are shown) for adjusting at least one of the following parameters of the optical signal in the foreign channel: wavelength, power, dispersion, and b) providing in the foreign channel(s) pilot tone(s) similar to those required by the original equipment.

To provide a foreign channel with a suitable pilot tone, the system 10 performs the following operations. A monitoring block 26 monitors samples of the optical signals transmitted over the original channels λl - λ3 to detect and recognize pilot tones fl, £2 and £3. The monitoring block 26 transmits information on the detected pilot tones to a processing and control block 28 which analyzes parameters (frequency, amplitude, type of modulation) of the detected original pilot tones and makes a decision which parameters are to be used for producing suitable "additional" pilot tones for the additional channels λk and λk+1. For example, if the processing block reveals that the original pilot tones perform simple amplitude modulation, and that £2 =2fl, and f3=3fl, the frequencies of the additional pilot tone determined by the block 28 will be: for the additional channel λk: fk =k*fl, and for the additional channel λk+1: fk+1 =(k+l)*fl.

The block 28 controls a modulation block 30 which, in this case, comprises two modulation sub-blocks 31 and 32. Under control of the processing/control block

28, the modulators 31 and 32 apply amplitude modulation to the signals transmitted by the transmitters 22 and 24, according to the determined additional pilot tones and at respective frequencies fk and fk+1. It should be noted that other types of modulation and more complex principles of forming different pilot tones can be recognized and reproduced by the processing/control block 28.

Upon applying the above-described modulation, the foreign channels' signals generated by the transmitters 22 and 24 can be recognized by the MUX 12 as additional channels Lambda k and Lambda k+1, multiplexed and transmitted over the WDM network in the multiplexed form for further processing, demultiplexing and dropping at any required site. The impressed additional pilot tones will serve as passwords of the foreign channels from (Tx)k and (Tx)k+1 while passing through the WDM network original equipment. It should be noted that the monitoring block 26 is an optional block. In case the processing and control block 28 is preliminary update about the required pilot tones, or is capable of processing thereof according to any algorithm without monitoring, the block 26 may be absent.

Fig. 2 illustrates one of the basic embodiments of the proposed technique and comprises elements similar to those in Fig. 1. In the drawing, the like elements are marked with like numbers. Let in the WDM network, portion of which is shown in Fig. 2, all the original channels are amplitude modulated by identical low frequency pilot tones. A system 110, for integrating into the WDM network a foreign channel λ5 issued by the foreign equipment (Tx)5, comprises a combined monitoring/processing/control block 128 and a modulator 131. In this particular example, the modulator 131 is a controllable optical attenuator VOA. The block 128 monitors a sample of optical signal transmitted via the original channel λl, detects a low frequency pilot tone fl and controls the VOA 131 in accordance with the detected pilot tone. Low frequency changes of attenuation of a signal transmitted over the foreign channel λ5 simulate the modulation frequency that has been applied to any of the original channels at the respective transmitter blocks Txl-Tx3 (114, 116,118).

The foreign channel λ5 can therefore be admitted to multiplexing in the MUX 112 and be transmitted via the cable 120 in the multiplexed form towards other nodes of the WDM network.

As has been mentioned, the character of original pilot tones introduced in the original channels may be known in advance and, if such pilot tones are not subjected to essential dynamic changes, there will not be a need in monitoring the original channels/original pilot tones (the arrows between the original channels and the blocks 26, 128 are therefore shown as dashed lines). The block 28 of Fig. 1 and the block 128 of Fig. 2 can then perform only the function of controlling the one or more modulating blocks 31, 32, 131. hi this case the block 28 may be decentralized, and local control sub-blocks (not shown) may be integrated with each of the modulation blocks 31, 32, similar to the manner of connection between blocks 128 and 131.

The VOA 131 may also perform power adaptation of the foreign channel. To make the module shown in Fig. 2 more universal, it may additionally comprise a power amplifier (not shown) so as to adjust the power of the foreign channel in any desired direction.

Let the multiplexed optical signal is then separated into the optical channels λl - λ5 at a de-multiplexer (DMUX) 140, for example being part of an OADM (not shown). The system 110, for adapting the foreign channel transmitted over the wavelength λ5 to the WDM network, additionally comprises an adapting block 125 placed in the channel after the DMUXl 40 (in the channel already inserted in the system). For example, such an adapting block can be an additional power adjustment block, a dispersion compensation unit, a combination of adapting blocks. Adapting blocks responsible for wavelength shift or for inserting pilot tones must be placed in the foreign channel immediately before feeding thereof to the original WDM equipment.

Fig. 3 illustrates a generalized block-diagram of the proposed module 210 for adapting foreign channels before introducing thereof in the WDM network. The module comprises a controllably configurable connectivity matrix (switch) 240 which, according to a control signal 242 from a control unit 244 (for example, manipulated by an operator or automatically) is able to form various internal connections between its multiple input and output contacts. It can be seen that the connectivity matrix 240 is provided with a first plurality of input contacts marked with even numbers from 250 to 260, and a second plurality of output contacts marked with odd numbers from 251 to 261.

One of the input contacts marked 260 is used for connecting to the matrix an incoming fiber 246 via which an optical signal is transmitted over a foreign channel to be admitted to a WDM network. That foreign channel, upon being adapted, is outputted from the matrix 240 at an output contact marked 261 to an outgoing fiber 248.

When passing the connectivity matrix, the optical signal of the foreign channel can be selectively handled by a number of adaptation blocks. A limited number of such blocks are shown and marked by even numbers 270-278. If necessary, the carrier wavelength of the optical signal transmitted over the foreign channel can be treated by a wavelength shifting block 276. Power of the foreign channel can be regulated by using an optical amplifier 270 and/or a variable optical attenuator (VOA) 274. Chromatic dispersion of the optical signal can be compensated by a dispersion compensation unit (DCU) 272, for example a dispersion compensation fiber DCF. The blocks 270, 272 and 274 are shown as controllable blocks and can be controlled by the control unit 244.

However, the power control can be performed by selecting and switching in the foreign channel (by means of the matrix 240) a set of constant elementary amplification and attenuation blocks, as well as the dispersion compensation can be provided by using a chain of DCU blocks having constant values.

Insertion of a pilot tone, if required, can be accomplished by a controllable or configurable modulation block 278 which may comprise a set of various modulation means ready for being switched between an active mode and a passive mode. It should be noted that a real configurable connectivity matrix may comprise much more input and output contacts, and that more than one foreign channels can be connected to and handled in such a matrix independently from one another. Such a real matrix can be formed from a number of matrices similar to the matrix 240.

The module shown in Fig. 3 is also provided with a monitoring unit 280 responsible for monitoring parameters of the foreign channel 246. The unit 280 communicates with the control block 244 via connection 282. The control block 244 also receives information about pilot tones, in this figure it is symbolically shown by an arrow 284. Upon comparing the monitoring information about parameters of the foreign channel 246 with parameters required for the original channels, including the information concerning pilot tones, the control block 244 issues control signals 242 to the matrix 240, causing it to connect suitable adaptation blocks in the path of the signal incoming via port 260. It should be appreciated that "proprietary marks" other than pilot tones can be utilized by original equipment of optical networks in addition or instead of the pilot tones, therefore other modified systems can be proposed for analyzing and reproducing such "proprietary marks" in the foreign channels to be integrated in the network.

Also, various implementations of the proposed block diagrams are possible and those modifications and implementations should be considered part of the invention.

Claims

Claims:

1. A method for interlacing communication traffic carried along one or more foreign optical channels with communication traffic carried along an optical network, which network is adapted to handle a pre-defined number of original optical channels and characterized in that no communication traffic is being conveyed along one or more channels, called non-operative, of said pre-defined number of optical channels; the method comprises: adapting at least one parameter characterizing optical signals transmitted along the one or more foreign channels so as to bring said at least one parameter into conformity with respective at least one parameter characterizing optical signals to be transmitted along the original optical channels, wherein said at least one parameter being selected from among: wavelength, power, chromatic dispersion, pilot tone, and wherein said adapting is performed at the optical layer of said optical network.

2. The method according to claim 1, wherein said adapting of the at least one parameter of optical signals transmitted along the one or more foreign channels is carried without prior converting said optical signals into their electrical form.

3. The method according to Claim 1 or 2, further comprising a preliminary step of monitoring said one or more foreign channels to allow evaluation of said at least one parameter.

4. The method according to any one of Claims 1 to 3, wherein at least one of the pre-defined number of original optical channels is associated with an original pilot tone, the method comprises: selecting one or more pilot tones respectively suitable for the one or more non-operative channels, said pilot tones being called additional pilot tones, modulating traffic conveyed along said one or more foreign channels with corresponding one or more additional pilot tones, and interlacing communication traffic conveyed along said one or more foreign channels carrying said respective one or more additional pilot tones with communication traffic carried along said original optical channels in the place of said respective one or more non-operative channels.

5. The method according to Claim 4, wherein the step of modulating is performed by activating a variable optical attenuator (VOA) upon the optical signal conveyed along the foreign channel and controlling the VOA according to the determined corresponding additional pilot tone.

6. The method according to any one of the preceding claims, further comprising a step of carrier frequency adaptation prior to interlacing the traffic conveyed along said foreign channel with the communication traffic carried along original optical channels.

7. The method according to any one of the preceding claims, further comprising a step of power adaptation of the optical signal prior to interlacing the traffic conveyed along the one or more foreign channels with the original optical channels.

8. A system for interlacing communication traffic carried along one or more foreign optical channels with communication traffic carried along an optical network adapted to handle a predefined number of original optical channels and characterized in that no communication traffic is being conveyed along one or more channels, called non-operative, of said pre-defined number of original optical channels, the system comprising means operative to adapt at least one parameter characterizing optical signals transmitted along said one or more foreign channels, so as to bring said at least one parameter into conformity with respective at least one parameter characterizing optical signals to be transmitted along the original optical channels, wherein said at least one parameter being selected from among: wavelength, power, chromatic dispersion, pilot tone, and wherein said system being operable to perform the adaptation at the optical layer of said optical network.

9. The system according to Claim 8, capable of adapting said at least one parameter of optical signals transmitted along the one or more foreign channels without prior converting said optical signals into electrical form.

10. The system according Claim 8 or 9, being arranged in the form of a module for interlacing communication traffic carried along said one or more foreign channels into said optical network, wherein the module is capable of adapting said at least one parameter of optical signals transmitted along the one or more foreign channels immediately prior to their interlacing with traffic carried along said original optical channels.

11. The system according to any one of Claims 8 to 10, wherein at least one of the pre-defined number of original optical channels being associated with an original pilot tone, wherein said means comprising a control and processing block (CP) and a modulation block controllable by said CP, said CP being capable of selecting one or more pilot tones called additional tones, and controlling the operation of the modulation block in response to the selected one or more additional pilot tones, the modulation block being operative to modulate optical signals transmitted along the one or more foreign channels according to the selected one or more additional pilot tones.

12. The system according to Claim 11, further comprising a monitoring block adapted to provide said CP with information relating to pilot tones conveyed along said optical network.

13. The system according to Claim 11 or 12, wherein the modulation of optical signals transmitted along said one or more foreign channels is performed by one or more controlled variable optical attenuators (VOAs).

14. The system according to any one of claims 8 to 13, comprising a configurable matrix having a first plurality of input ports and a second plurality of output ports, wherein at least one of the input ports is connectable to an incoming fiber, at least one of the output ports is connectable to an outgoing fiber, and a number of adaptation blocks are associated with said matrix, wherein each of said adaptation blocks being capable of adapting at least one parameter of an optical signal passing there-through, and is connected between at least one input port and at least one output port of the matrix; and wherein the matrix being configurable in such a way that an optical signal transmitted along a foreign channel via the incoming fiber, is directed to pass through at least one of said adaptation blocks in a desired order and to be outputted via the outgoing fiber in the form acceptable by the optical network.