WO2012113844A1

WO2012113844A1 - Optical system

Info

Publication number: WO2012113844A1
Application number: PCT/EP2012/053034
Authority: WO
Inventors: Norberto AMAYA GONZALES; Georgios ZERVAS; Dimitra Simeonidou
Original assignee: Wivenhoe Technology Limited
Priority date: 2011-02-22
Filing date: 2012-02-22
Publication date: 2012-08-30
Also published as: GB201103057D0; EP2679018A1

Abstract

The present invention relates to an optical system including: at least one optical system input (12) for receiving an input optical signal, at least one optical system output (14) for outputting an optical signal, an optical switch (1) including a plurality of inputs (8) for receiving an optical signal and a plurality of outputs (10) for outputting an optical signal, the optical switch (1) being configured to transfer an optical signal from any one of the optical switch inputs (8) to any one of the optical switch outputs (10), a plurality of modules (2) for processing an optical signal, each module (2) of the plurality of modules being configured to carry out a specific optical signal processing and includes at least one input (4) for receiving an optical signal to be processed and at least one output (6) for outputting a processed optical signal, the at least one input (4) of each module being optically connected to an output (10) of the optical switch (1), and the at least one output (6) of each module (2) being optically connected to an input (8) of the optical switch (1), an input (8) of the optical switch (1) other than that used for a module (2) is used as the at least one system input (12) and an output (10) of the optical switch (1) other than that used for a module (2) is used as the at least one system output (14). The optical system is configured to establish an optical path (OPP), along which an optical signal is routed, between the at least one optical system input (12) and the at least one optical system output (14) that includes at least one module (2) selected amongst the plurality of modules (2) for processing an optical signal received at the at least one system input (12).

Description

OPTICAL SYSTEM

TECHNICAL FIELD OF THE INVENTION:

The present invention relates to an optical system and in particular an optical switching or signal processing system or sub-system having a programmable and adaptive architecture on demand.

BACKGROUND OF THE INVENTION:

There has been a considerable increase in the range of transmission rates and the spread between large and small bandwidth demands that current optical networks are required to provide [see, for example, O. A. Gerstel, "Flexible Use of Spectrum and Photonic Grooming" in Photonics in Switching, OSA Technical Digest (CD) (Optical Society of America, 2010), paper PMD3. Requirements for dissimilar data rates may arise from the geographic distribution of traffic or the variety of services provided. For instance, in some cases high-bit-rate traffic (e.g. 100 Gb/s) may be needed for datacenter interconnection, whilst other users may require transport of 100 Mb/s, 1 Gb/s and 10 Gb/s circuits. This vast range of traffic granularities is expected to expand in the future as networks migrate to support higher transmission rates beyond 100G. There is a significant amount of research focusing on high- capacity superchannels at 400 Gb/s (see, for example, P.J. Winzer, A. H. Gnauck, S. Chandrasekhar, S. Draving, J. Evangelista, and B. Zhu, "Generation and 1200-km transmission of 448-Gb/s ETDM 56-Gbaud PDM 16- QAM using a single l/Q modulator," in 2010 36th European Conference and Exhibition on Optical Communication (ECOC), 19-23 Sept. 2010), 1 Tb/s (see, for example, S. Chandrasekhar and X. Liu, "Terabit superchannels for high spectral efficiency transmission" in 2010 36th European Conference and Exhibition on Optical Communication (ECOC), 19-23 Sept. 2010) and beyond (see, for example, J. Yu, Z. Dong and N. Chi, "Generation, Transmission and Coherent Detection of 11.2 Tb/s (112x100Gb/s) Single Source Optical OFDM Superchannel" in Optical Fiber Communication Conference (OFC 2011), 6 -10 March 2011 , paper PDPA6). Such superchannels may require channel spacings that would not be compatible with today's 100-GHz or 50-GHz ITU grid e.g. 75 GHz for 400Gb/s and 150 GHz for 1 Tb/s. Hence, there has been growing interest in gridless and elastic optical networking (see, for example, B. Kozicki, H. Takara, Y. Tsukishima, T. Yoshimatsu, K. Yonenaga, and M. Jinno, "Experimental demonstration of spectrum-sliced elastic optical path network (SUCE)" Opt. Express 18(21 ), 22105-22118 (2010) and S. Thiagarajan, M. Frankel, and D. Boertjes, "Spectrum efficient super-channels in dynamic flexible grid networks - A blocking analysis" in 2010 36^th European Conference and Exhibition on Optical Communication (ECOC), 19-23 Sept. 2010) as a means to efficiently accommodate a mix of superchannels and low-speed channels as well as to improve point-to-point and overall network efficiency, e.g. 400G occupying 75- GHz bandwidth is more than twice as efficient as 100G using 50 GHz.

On the other hand, efficient transport of lower bit-rate channels (e.g. hundreds of Mb/s) requires the implementation of sub-wavelength granularity whereby the transmission capacity of an optical channel is multiplexed among lower bit- rate demands.

Thus, in the future optical network, optical nodes will need to allocate resources in a flexible and efficient manner to efficiently support high-speed channels (beyond 100G), lower speed channels (e.g. 40 Gb/s, 10Gb/s) and sub-wavelength channels (e.g. hundreds of Mb/s).

Currently there are no optical systems that allow to dynamically configure the system architecture, use it for a particular purpose and re-configure it on the fly, for example, if current system requirements or conditions change. Current optical systems and sub-systems, including transparent optical cross-connects and signal processing units, have a static architecture that requires manual intervention when it needs to be reconfigured. A number of optical switch architectures have been proposed to support various forms of optical switching such as MG-OXC (see, for example, O. Moriwaki, et.al, "Terabit-scale Compact Hierachical Optical Cross-connect System Employing PLC Devices and Optical Backplane", OFC, PDPC9, San Diego, USA, March 2010), hybrid optical packet/circuit switch nodes (see, for example, H. Furukawa, et.al., First Demosntration of Integrated Optical Packet and Circuit Switching Node for New-Generation Networks, ECOC 2010), Packet-OADMs (D. Chiaroni et al., "Demonstration of the Interconnection of Two Optical Packet Rings with a Hybrid Optoelectronic Packet Router", ECOC, PD3.5, Torino, Italy, September 2010). In addition, recent developments in elastic/flexible bandwidth allocation demonstrate the ability to deliver higher level of switching flexibility by the use of bandwidth adaptive (BA) wavelength selective switches (WSS) (see, for example, H. Takara et al, "Distance- Adaptive Super-Wavelength Routing in Elastic Optical Path Network (SLICE) with Optical OFDM ", ECOC 2010).

Current optical cross-connects and optical signal processing architectures are static as the elements that make up the system/sub-system cannot be rearranged in order to provide additional functionality, modify the behaviour of the system or to relocate idle hardware so it can be utilised for another user, function or process.

Some existing solutions provide some level of configurability but it is only with respect to the optical signals that are processed (e.g. Wavelength Selective Switches (WSS), Multi-Granular Optical Cross-connects (MG-OXC) or Reconfigurable Optical Add Drop Multiplexers (ROADMs)). Thus, for these systems, although optical signals can be processed differently by the system/device, the architecture of the system/device itself is fixed and preconfigured as the components that make up the system/device are hard- wired in a static configuration.

In addition, traditional optical cross-connects (OXC), having static architectures that limit the efficiency of the system and the types of traffic that can be supported, have been proposed that can do a number of things e.g. MG-OXC, hybrid nodes in parallel for packet and circuit switched (CS) traffic, ROADMs but these architectures are static and do not change to suit traffic requirements. Also, they do not support gridless or elastic traffic and sub- wavelength granularity.

Current designs of signal processing units are also static and do not implement an adaptive architecture to provide specific functionality. Many static solutions have been proposed that provide fixed functionality such as optical signal generation, multiplexing, de-multiplexing, amplification, regeneration, wavelength conversion, optical switching, power coupling, power splitting, filtering, format conversion, synchronisation, delaying, buffering, modulation, de-modulation, non-linear processing, signal generation. However, the specific functionality provided by current signal processing systems (sub-systems) is fixed, generally limited to a small number of functions, and cannot be configured or re-configured according to traffic, system or operator's requirements.

The goal of the present invention is to solve the above mentioned problems.

SUMMARY OF THE INVENTION:

The present invention thus relates to an optical system according to claim 1.

Additionally, the invention concerns a method for controlling an optical system according to claim 14 and a computer program according to claim 15.

Other features and advantages are found in the dependent claims.

BRIEF DESCRIPTION OF THE FIGURES:

The above object, features and other advantages of the present invention will be best understood from the following detailed description in conjunction with the accompanying drawings, in which: Figure 1 illustrates an optical system according to the present invention;

Figure 2 shows an example architecture of the optical system of the present invention;

Figure 3 shows a system controller for controlling the optical system according to the present invention; Figure 4 illustrates an example of an optical system architecture implemented by the optical system of the present invention;

Figure 5 illustrates optical processing paths of the optical system of Figure 4; Figure 6 illustrates steps carried out by the optical system to determine an optical system arrangement to satisfy given traffic parameters when a request to route a given traffic load is received by optical system,

Figures 7(a),(b) and (c) show example optical cross-connect architectures that can be dynamically configured by the optical system of the present invention;

Figures 8 and 9 show a network arrangement in which the optical system of the present invention is employed; Figure 10 shows an arrangement/architecture of the optical system of the present invention used in the network illustrated in Figures 8 and 9;

Figure 11 shows another arrangement architecture of the optical system of the present invention used in the network illustrated in Figures 8 and 9;

Figure 12 shows measured results of sub-λ 10&40 Gb/s data-sets switched from Nodes A and B to nodes E and F, together with their eye diagrams, by the optical system of the present invention; Figure 13 presents measured results showing that there is a maximum 2 dB node and 4.5 dB end-to-end penalty for all channels switched routed through the optical system based on the present invention, plus field fibre links, using the arrangement illustrated in Figure 11 ;

Figure 14 shows measured spectrum plots of the signals switched through the optical system based on the present invention towards their destination for the optical system architecture illustrated in Figure 4;

Figure 15 shows measured spectrum plots of the signals switched through the optical system based on the present invention towards their destination for the optical system architecture illustrated in Figure 10; Figure 16 shows measured spectrum plots of the signals switched through the optical system based on the present invention towards their destination for the optical system architecture illustrated in Figure 11.

DETAILED DESCRIPTION:

As shown in Figure 1 , the present invention relates to an optical system comprising an optical switch 1 and a plurality of modules 2.

Each module 2 comprises a plurality of input ports 4 and output ports 6 and each module 2 is configured to process optical signals where a different type of module provides a different type of optical signal processing.

A module 2 may perform optical, and/or opto-electronic, and/or electronic signal/data processing and/or optical signal/data generation including, for example, at least one of: multiplexing, de-multiplexing, amplification, regeneration, wavelength conversion, optical switching, power coupling, power splitting, filtering, format conversion, synchronisation, delaying, buffering, modulation, de-modulation, non-linear processing, signal generation, encoding, decoding, time-slot interchanging, and electronic routing or switching, electronic data processing, electronic/optical data storage .

For example, module 2 may be a LCoS-based spectrum selective switch (SSS), a 2x2 PLZT optical switch (lead lanthanum zirconate titanate optical switch), a wavelength/waveband multiplexer, a wavelength/waveband demultiplexer or a 1x4 coupler and EDFAs.

Each module 2 of the plurality of modules is configured to carry out a different optical signal processing function. Alternatively, the plurality of modules may include a number of modules that carry out the same optical and/or optoelectronic and/or electronic signal/data processing function.

The optical switch 1 includes a plurality of input ports 8 and a plurality of output ports 10 to which the modules 2 are connected. The module input ports 4 are connected to the optical switch output ports 10 and the module output ports 6 are connected to the optical switch input ports 8.

Some of the optical switch inputs are used as system inputs where input signals are connected and some of the optical switch outputs are used as system outputs.

A plurality of input ports of the optical switch 1 that are not used to connect to a module 2 are used as system input ports 12 for receiving input optical signals to be processed by the optical system, and a plurality of output ports of the optical switch 1 that are not used to connect to a module 2 are used as system output ports 14 for outputting optical signals processed by the optical system. In the present embodiment, as illustrated in Figure 1 , the optical system comprises four system input ports 12 and four system output ports 14.

The input and output ports of the optical switch 1 and the modules 2 are connected, for example, using optical fibers. The optical signals to be processed by the optical system are also communicated to the system input ports 12 using optical fibers connected to the system input ports 12 and the optical signals processed by the optical system are communicated from the system output ports 14 using optical fibers connected to the system input ports 14.

The optical switch 1 is configured to interconnect the inputs, modules and outputs by means of internal cross-connections. The optical switch 1 is configured to optically interconnect a system input port 12 or an optical switch input port 8 with an optical switch output port 10, a module input port 4 or a system output port 14. The optical switch 1 is further configured to optically interconnect an optical switch input port 8 or a module output port 6 with an optical switch output port 10, a module input port 4 or a system output port 14. These interconnections are implemented using internal cross connections 16 of the optical switch 1. In the present embodiment of the invention, the optical switch is an optical fibre switch and, in particular, a NxM optical cross-connect 3D micro-electro-mechanical (MEMS) optical switch (N=M=96), for example, the model Calient FiberConnect. Alternatively, the optical switch may be, for example, a Liquid crystal on silicon (LCoS) switch, a 2D- MEMS switch or a direct beam-steering switch.

A specific sequence of connected modules 2 to process and/or generate signal(s) defines the optical system architecture. Different architectures or optical system arrangements may be constructed for different system inputs and may be dynamically changed/reconfigured on the fly by re-configuring the connections in the optical switch 1 according to signal or system requirements.

The processing of optical signals by the optical system is as follows:

1. Input signals are connected by the optical switch 1 to the switch output that connects to the input of the module 2 required to process the signal.

2. The optical signal is processed at the module.

3. After the signal has been processed by the module it appears at the module's output(s), which is(are) connected to input(s) of the optical switch 1. 4. From here, depending on the optical system architecture, the optical signal(s) is directed to other module(s) for further processing and the sequence is repeated from step 2 for the resulting signal(s), or the optical signal(s) is switched to the output(s) of the optical system.

The optical system of the present invention addresses the limitations of existing OXCs and optical signal processing (sub)-systems by providing flexible processing and switching of optical signals through customised/programmable architectures of the optical system. Unlike existing OXC and optical signal processing (sub)-system architectures, the components (modules 2) of the optical system used for optical processing e.g. multiplexer (MUX), de-multiplexer (DEMUX), spectrum selective switch (SSS), optical fast switch, wavelength conversion (WC), regenerator; are not hardwired within the architecture but can be interconnected together in a completely free manner. They can be dynamically added/removed from implemented OXC or optical signal processing (sub)-system architectures or re-located anywhere to form new arrangements within an architecture. As an example, Figure 2(a) shows a possible implementation of the optical system of the present invention where a number of architecture-building modules 2 are attached to an optical backplane implemented with a large port-count optical switch 1 (e.g. 3D-MEMS). An architecture, such as the one shown in Figure 2(b), is constructed by interconnecting suitable architecture-building modules 2 using cross-connections in the optical backplane. In accordance with the present invention, architectures that support the processing and switching requirements of input optical signals are devised and implemented by an automated mechanism. Also, as architectures utilise only the needed architecture-building modules 2 to provide the required functionality, the requested switching complexity is reflected on the architecture complexity. For instance, in the example architecture depicted in Figure 2(b), only one cross- connection is used to switch traffic from input C to output G (fiber switching). Conversely, traffic going from input A to output E have a more complex switching requirement that is realised with the modules 2 of a SSS (e.g. for elastic spectrum) and a PLZT switch (e.g. for time-shared sub-wavelength granularity). Thus, each optical system port may implement different levels of switching granularity, from fiber/fiber-core switching to fine-granular frequency and time switching. Support for high-speed signals can be provided by utilising modules that allow the allocation of arbitrary bandwidth to a particular channel e.g. LCoS-based spectrum selective switches (SSS). Also, efficient transport of multiple bit-rates may require using different filter bandwidths for (de)-multiplexing. Therefore, the optical system of the present invention supports multiple bit-rates either by using (DE)MUX modules 2 with different channel spacings or by using spectrum selective switches The optical system of the present invention also provides support for sub-wavelength traffic in the frequency domain i.e. as sub- carriers of an orthogonal frequency-division multiplexing (OFDM) super- channel; or in the time domain i.e. in the form of optical burst switching (OBS), optical packet switching (OPS) or any alternative time-shared optical transport and switching systems. In the former case, spectrum selective switches can provide the required spectrum granularity, whereas, in the latter case fast optical switches are required (e.g. 10-ns PLZT switch). Additionally, The optical system of the present invention enables the combination of small (1x2 or 2x2) fast switch elements to build larger fast switch matrixes with a structure tailored to the switching requirements of sub-wavelength traffic.

A major benefit of the optical system of the present invention is the flexibility to simultaneously accommodate multiple services including existing 10 Gb/s, 100 Gb/s, future higher bit-rates with arbitrary bandwidth requirements and bit-rate variable OFDM with elastic bandwidth allocation. The optical system of the present invention also enables support for arbitrary switching granularity, such as superwavelength, waveband, wavelength and sub-wavelength switching, on any port. Furthermore, the modularity of the optical system facilitates dimensioning, provisioning and upgrading with enhanced or new functionality. For instance, if a new signal processing function is required (e.g. single or multi-wavelength conversion, regeneration, etc.), a module providing such functionality is plugged into the optical backplane/optical switch 1 and, immediately, the system can start using it when and where required. All optical restoration and self-healing from module failures is also enhanced either by swapping the faulty module with an operational module or by self-constructing an alternative architecture that does not require the functionality provided by the faulty module.

The optical system of the present invention provides dynamic reconfiguration of the optical system architecture and more efficient use of hardware resources that may be released when no longer required and relocated to where their functionality is needed within the optical system.

The optical system can process an input optical signal received at one system input port 12 and output the processed optical signal at a system output port without conversion of the optical signal into an electrical signal. Alternatively, the optical signal can be converted into an electrical signal by a module 2 for electronic processing and reconverted back to an optical signal after electronic processing.

The optical system includes an optical system controller 18, as illustrated in Figure 3, for controlling the optical system illustrated in Figures 1 and 2. The optical system controller 18 of the present embodiment comprises an optical switch controller 20, a communication unit 22, a communication interface 24, a system architecture calculating unit 26, an optical system controller microprocessor 28, memory 30 and bus 32 permitting the above elements of the optical system controller 18 to intercommunicate.

It is to be noted that the system architecture calculating unit 26 is optional and in an alternative embodiment of the present invention, the optical system controller 18 does not include a system architecture calculating unit 26.

In the present embodiment, the memory 30 stores data relating to the optical system such as a list of the modules 2 and the functionality of each module 2, as well as the architecture or arrangement currently implemented in the optical system, if one is implemented. Memory 30 also includes control programs that are executed by the microprocessor 28 to operate and control the general functioning of the optical system using the optical switch controller 20, the communication unit 22, the communication interface 24 and the system architecture calculating unit 26.

Memory 30 also stores a module control program for each module 2 for individually controlling each module 2 of the optical system. The microprocessor 28 executes a module control program to control the functions of the module 2 and to change and set the internal settings of the module 2.

For modules such as, for example, a multiplexer, de-multiplexer, wavelength selective switch or time switch, whose operation in the spectral domain and/or the time domain can be set to specific values or ranges, the microprocessor 28 is configured, through a corresponding module control program, to modify and set the operating spectral domain and/or the time domain values to permit the module to process inputted optical signals in a given spectral range or with respect to given optical signal timings. The microprocessor 28 is further configured to allocate spectral and/or time domain resources to the optical signals processed by the module and outputted from the module.

In addition, the microprocessor 28 is configured, through a corresponding module control program, to modify and set the spatial resources of a module 2 by defining the available input ports of the module for receiving optical signals and the available output ports of the module 2 for outputting processed signals.

The internal processing carried out on an optical signal by the module 2 can thus be configured and reconfigured by the microprocessor 28 and the optical system. This permits specific optical processing of the optical signals inside each module to be finely setup and implemented by the optical system. This also permits elastic or flexible allocation of spectral, time and space resources of a module and the optical system, and in particular, per input port of the optical system. Module control programs for each module 2 stored in memory 30 is optional and in an alternative embodiment the optical system does not include module control programs and the microprocessor 28 does not execute a module control program to change and set the internal settings of a module 2.

In this alternative embodiment, the processing function carried out by each module is predefined and known to the optical system, and how an optical signal will be processed if inputted at a given port of a module and at what output ports the processed signal will arrive are also known to the optical system.

For example, memory 30 contains data relevant to each module indicating the input ports of a module that an optical signal should be inputted to for the optical signal to undergo a given processing, and what output ports of the module the processed signal will be outputted at. The optical system solely connects an input optical signal to the relevant input port(s) of one module and the relevant output port(s) of that module to the input port(s) of another module (and to as many modules as is necessary) to carry the required processing of an input optical signal.

The optical switch controller 20 of the optical system is configured to actuate the optical switch 1 (in the present embodiment to actuate the movable reflective elements of the 3D MEMS, however any other switch technology is possible) to route optical signals to and from the input and output ports of the optical switch 1 and the modules 2 in order to set up an optical path from a system input port 12 to a module 2, and from said module to one or more modules 2 or to a system output port 14. The optical switch controller 20 is configured to set up such an optical path through the modules 2 for an optical signal to be received at a system input port 12, for each system input port 12. In this way, an optical signal arriving at a system input port 12 is communicated through one or more modules 2 where it is processed by each module it passes through and delivered to a system output port 14 as a processed optical signal. The optical switch controller 20 thus establishes an optical processing path or an arrangement through the optical system that an optical signal arriving at the system input port 12 follows and in which the optical signal is processed and then outputted as a processed optical signal at a system output port 14. The architecture of the optical system of Figure 1 can thus comprise one or a plurality of optical processing paths or arrangements through the optical system.

The optical switch controller 20, according to the present embodiment, is further configured to receive data defining an optical system architecture to be implemented from the system architecture calculating unit 26. The data defining an optical system architecture sets out which modules 2 of the optical system are to be interconnected to each other and interconnected to the system inputs and outputs, and the manner in which these modules 2 and the system inputs 12 and outputs 14 are to be interconnected (which specific ports are to be interconnected). If required, data relating to the internal configuration of the modules to be employed is sent by the system architecture calculating unit 26 to the microprocessor 28 which subsequently reconfigures the internal settings of the module to be employed to the required values. The optical switch controller 20 is configured to optically interconnect the modules 2 and the system inputs 12 and outputs 14 according to data defining the received optical system architecture and to establish the optical processing paths through the modules according to the received data defining the optical system architecture. The optical switch controller 20 used in this present embodiment is, for example, the controller provided by the Calient FiberConnect system which interfaces with the system controller 18 using TL1 or a GUI.

Figure 4 illustrates an example of an optical system architecture implemented by the optical system of the present invention. System input port 12 connected to Node A is to receive from Node A a plurality of communication channels containing optical signals and data that is required to be switched through towards a system output port 14 connected to Node E. System input port 12 connected to Node B is to receive a plurality of communication channels containing optical signals and data, some of which is to go to a system output port 14 connected Node E and some to a system output port 14 connected to Node F. System input port 12 connected to Node C is to receive a plurality of communication channels containing optical signals and data whose destination is Node G.

The architecture required to provide this switching functionality, shown in Figure 4, is implemented by establishing the required cross-connections in the 3D-MEMS switch between three modules (a de-multiplexer (DEMUX), a multiplexer (MUX) and an amplifier connected between two couplers) and the optical system input 12 and output ports 14. The de-multiplexer is used to split the signals from Node B, the multiplexer is used to recombine the signals towards Node F, the amplifier between the two couplers is used to merge the signals from Nodes A and B towards Node E. Switching the channels from Node C to Node G requires only one cross-connection in the 3D-MEMS optical switch and does not require the use of a module 2.

Specific arrangements of connected modules from a system input 12 to a system output 14 define the architecture of the system. Different arrangements are constructed from the different system inputs 12. One module (an amplifier connected between two couplers) is connected between the system input 12 connected to Node A and the system output 14 connected to Node E (a first arrangement comprising one module). An optical processing path OPP1 (see Figure 5), along which an optical signal is routed, for processing the channels and optical signals received at Node A is thus established between the system input 12 connected to Node A, the amplifier connected between two couplers module and the system output 14 connected to Node E. The optical processing to be carried out on optical processing path OPP1 is thus a coupling of the optical signals of the Node A to those from Node B (that have also been amplified) that are destined to Node E.

Two modules (de-multiplexer (DEMUX) and an amplifier connected between two couplers) are connected between the system input 12 connected to Node B and the system output 14 connected to Node E (a second arrangement comprising two modules). An optical processing path OPP2 (see Figure 5), along which an optical signal is routed, for processing some of the channels and optical signals received at Node B is established between the system input 12 connected to Node B, the de-multiplexer (DEMUX), the amplifier connected between two couplers module and the system output 14 connected to Node E. The optical processing to be carried out on optical processing path OPP2 is a demultiplexing of the received channels/optical signals, a coupling and then amplification of these optical signals and a further coupling with the optical signals of the Node A that are also destined to Node E.

This optical processing path OPP2 is set up using a selected number of the output ports of the de-multiplexer (DEMUX) module 2 that are optically connected to a selected number of the input ports of the amplifier connected between two couplers module 2, that is, those connecting to a first coupler 36. The remaining input port of the amplifier connected between two couplers module 2 connects to second coupler 38 and to which is connected the system input port 12 connected to Node A. The amplifier connected between two couplers module 2 has one output port that is connected to the system output 14 connected to Node E.

Two modules (de-multiplexer (DEMUX) and multiplexer (MUX)) are connected between the system input 12 connected to Node B and the system output 14 connected to Node F (a third arrangement comprising two modules). An optical processing path OPP3 (see Figure 5), along which an optical signal is routed, for processing the remaining channels and optical signals received at Node B is established between the system input 12 connected to Node B, the demultiplexer (DEMUX), the multiplexer (MUX) module 2 and the system output 14 connected to Node F. The optical processing to be carried out on optical processing path OPP3 is thus a demultiplexing of the remaining received channels/optical signals and a multiplexing of these remaining received channels/optical signals to be routed to Node F. This optical processing path OPP3 is set up using a selected number of the output ports of the de-multiplexer (DEMUX) module 2 (different to those used in OPP2) that are optically connected to a number of the input ports of the multiplexer (MUX) module 2. The sole output port of multiplexer (MUX) module 2 is connected to the system output 14 connected to Node F and the sole input port 12 of the de-multiplexer (DEMUX) module 2 is connected to the system input port 12 connected to Node B.

The optical system architecture illustrated in Figure 4 can be dynamically changed/reconfigured on the fly by re-configuring the cross-connections in the optical switch 1 to setup new inter-module connections according to the optical signal requirements to be received, or the requirements of a system or network in which the optical system according to the present invention is implemented. Moreover, the optical system is adapted to configure each module 2 internally and individually, using the microprocessor 28 executing a module control program, to set the internal settings of the module 2 so as to define the how optical signals are routed and processed internally in the spectral and time domain and to define those input ports 4 optical signals are to be received at, and those output ports 6 processed optical signals will exit the module at. For example, the number of output ports of the de-multiplexer (DEMUX) module 2 may be increased to use the full capacity of the de-multiplexer (DEMUX) and to direct additional optical signals to be received at given wavelengths to these additional output ports.

The communication unit 22 is configured to receive, via interface 24, a request message from an external source such as, for example, a network operator or service provider in the network in which the optical system is connected or a network traffic monitoring device configured to monitor traffic in the network in which the optical system is connected. The communication unit 22 is configured to transfer the request message to the system architecture calculating unit 26. The received request message provides information concerning the optical signals intended to be sent to the optical system and the switching and/or processing requirements of these optical signals in terms of optical spectrum requirements, time domain requirements and spatial requirements (for example, one or more of: the number of channels, the channel data rate, spectrum spacing and allocation, spacing in the time domain, splitting or coupling in the spatial domain, modulation type, wavelength or modulation format conversion requirement) and also provides information concerning the destinations to which these channels are to be routed.

The system architecture calculating unit 26 includes a storage unit containing a software program for calculating optical system architectures. Upon receipt of the request, the system architecture calculating unit 26 is configured to execute the software program for calculating optical system architectures to determine those optical system architectures permitting the received request to be implemented (to compute suitable arrangements of modules 2 and a suitable optical system architecture) and that fulfil the requirements of the received request. That is, modules 2 and the optical processing paths to be set up using these modules 2 that can implement the received request are calculated. The system architecture calculating unit 26 is configured to then obtain, from memory 30, a list of the current plurality of modules 2 and the functionality of each of the modules 2 of the optical system, and then select a calculated system architecture that can be implemented based on the available modules 2 of the optical system. In the case where none of the calculated system architectures can be implemented based on the available modules 2 of the optical system, the system architecture calculating unit 26 is configured to communicate a message rejecting the request to the external network operator. The system architecture calculating unit 26 is configured to communicate the selected calculated system architecture that can fulfil the request to the optical switch controller 20 which then connects the modules in the required sequence and arrangements to set up the optical processing paths from the system input ports 12 through the modules 2 to the system output ports 14 according to the selected calculated system architecture.

Figure 6 illustrates the steps carried out by the optical system and, in particular, the system architecture calculating unit 26 when a new request is received and an optical system architecture is already implemented by the optical system. The received request relates to an optical signal requirement or an optical or opto-electronic or electronic signal processing requirement concerning an optical signal/data to be received at a system input, or to be generated by one of the system modules.

The system architecture calculating unit 26 calculates the optical system architectures permitting the received new request to be implemented. The system architecture calculating unit 26 then obtains, from memory 30, the current optical system architecture implemented by the optical system. The system architecture calculating unit 26 then determines, through a comparison with the list of calculated optical system architectures, whether the currently implemented optical system architecture can also be used to implement the new request. If this is the case, the currently implemented optical system architecture is used to implement the new request. This may or may not require some internal reconfiguration of the modules 2 in the present embodiment configured to carry out internal reconfiguration of the modules 2. In the alternative embodiment where internal reconfiguration of the modules 2 is not carried out, the system architecture calculating unit 26 calculates the optical system architectures based on the predefined processing functions of the modules 2.

In the case where the currently implemented optical system architecture cannot be used to implement the new request, the system architecture calculating unit 26 obtains, from memory 30, a list of the current modules 2 and the functionality of each of the modules 2 of the optical system, and then calculates a system architecture that can be implemented based on the available modules 2. In the case where none of the calculated system architectures can be implemented based on the available modules 2 of the optical system, the system architecture calculating unit 26 communicates a message rejecting the request to the external source that sent the request. The system architecture calculating unit 26 communicates the selected calculated system architecture to the optical switch controller 20 which then sets up the interconnections between the required modules 2 and the optical processing paths from the system input ports through the modules 2 to the system input ports according to the selected calculated system architecture for the new request.

The communication unit 22 of the present embodiment is also configured to receive, via interface 24, an optical system architecture to be implemented from an external source such as, for example, a network operator or service provider in the network in which the optical system is connected or a network traffic monitoring device configured to monitor traffic in the network in which the optical system is connected. In this case, the received optical system architecture to be implemented is already calculated and known. The communication unit 22 is configured to transfer the new optical system architecture to the optical switch controller 20 which then connects the modules in the required sequence and arrangements to set up the optical processing paths from the system input ports through the modules 2 to the system output ports according to the received optical system architecture. In the case where the received optical system architecture cannot be implemented by the optical system, a message signalling this impossibility is sent to the external source.

As can be understood from the preceding passages, the optical system architecture of the optical system of the present invention is re-configurable and can be re-configured automatically by an automated mechanism (system controller 18) without any manual intervention by a technician to reconfigure the components of the optical system, in particular, the interconnections between the module(s) and the system input and outputs. The reception of a new optical system architecture by the system controller 18 from an external source triggers an automatic architecture configuration /re-configuration by the system controller 18 without any intervention by a technician on the optical system, that is, the optical system autonomously proceeds to reconfigure the optical system to implement this new architecture or arrangement without the involvement or intervention of a technician having to be informed of the new optical system architecture and having to manually or remotely reconnect the optical system connections to implement the new optical system architecture. The process illustrated in Figure 6 and detailed previously can also trigger automatic architecture re-configurations without any manual intervention on the optical system. When a new request is received the system controller 18 evaluates whether it can be supported with the currently configured architecture or with a different optical system architecture. If a different optical system architecture is necessary, the optical system autonomously proceeds to reconfigure the optical system to implement this new architecture or arrangement without the involvement or intervention of a technician as previously mentioned.

Modules can be added to the optical system when and where required with the simplest architecture supported consisting of a switch cross-connection and the most complex architecture involving all the modules attached to the system.

Figures 7(a),(b) and (c) show example optical cross-connect architectures that can be configured using the present invention and appropriate modules to provide the various optical processing functionality. Example optical cross- connect architectures that can be dynamically configured by the invention are: Figure 7(a): Fibre cross-connect, Figure 7(b): gridless and elastic optical cross- connect, and Figure 7(c): optical cross-connect that enables flexible timeshared spectrum allocation.

The optical system according to the present invention procures the following advantages: 1. Flexible, automatic and dynamic optical system architectures on demand,

2. Programmable in real time,

3. Modular provisioning and modular growth,

4. Self-healing and fast recovery from module/system failures by detecting and replacing defective modules in real time,

5. Efficient use of hardware resources leading to a fewer number of required modules compared to a static architecture,

6. Upgradable with additional/improved capabilities by adding new/improved modules so the optical system is future-proof.

The optical system according to the present invention can be used, for example, for the following applications:

1. Flexible transparent optical cross-connect

2. Reconfigurable optical signal processing unit (optical analog of an electronic FPGA)

In what follows, the optical system according to the present invention is further described as part of a first field experiment. The field experiment demonstrates, for the first time, an adaptive optical cross- connect (OXC) that supports elastic allocation of arbitrary spectral, time and space resources per port in a (a)symmetric manner in order to dynamically synthesize suitable architectures-on-demand tailored to traffic requirements. The system is implemented to transparently switch up to 1.5 Tb/s of traffic with all-optical granularities ranging from 143 Mb/s up to 160 Gb/s (a factor of over 1000). Any OXC port is able to allocate any Gridless spectrum-slice within the range of 12.5 GHz-5THz with a step size of 1 GHz, as well as perform time- slice allocation with a minimum of 0.97 ps a step-size of 1.06 ps and a maximum of continuous time-allocation. The OXC is also able to optically groom channels with different bit-rates (10Gb/s and 40Gb/s) as well as multicast sub-λ data flows. Central to the proposed OXC architecture is a 20ms 96x96 3D-MEMS optical switch (however any other switching technology can be applied) complimented by several architecture-building modules such as 200ms LCoS-based spectrum selective switch (SSS) (see "WaveShaper S-Series Product Brief, http://www.finisar.com/optical_instrumentation, October 2010), 10ns 2x2 PLZT optical switch (K. Nashimoto et al, "High-speed switching and filtering using PLZT waveguide devices", OECC 2010, Japan, July 2010), wavelength/waveband (De)-Multiplexer, 1 x4 couplers and EDFAs. Modules are attached to the MEMS switch so that their inputs and outputs connect to the MEMs outputs and inputs respectively as illustrated in Figure 1. Some of the MEMS ports are reserved as OXC inputs/outputs and add/drop according to the required node degree and add/drop capability. The MEMS interconnects inputs, modules and outputs by means of internal cross-connections to deliver the architecture-on-demand OXC functionality.

During operation, the switching requirements (spectrum-time-space) of the optical signals determine the arrangement and interconnection of the modules, which would deliver the suitable OXC architecture. Individual architectures can be constructed and tailored on a per-port basis to switch data-sets carried over different spectral and time-shared channels by dynamically re-configuring the optical switch cross-connections.

The network scenario, displayed in Figures 8 and 9, consists of three source nodes (A, B and C), one adaptive OXC (D) and three destination nodes (E, F and G). Nodes A and E are linked to D by dispersion compensated ITU-T G.652 field fiber sections of 80 km and 1 10 km deployed in the UK between the University of Essex-Ipswich and the University of Essex-Chelmsford respectively (see Figure 9). Channels are generated at the source nodes and transmitted to D where they are switched to their destination node(s). At Node A, a multi-channel multi-format transmitter generates continuous 4x40 Gb/s NRZ and 3x40 Gb/s RZ plus sub-λ 8x40 Gb/s RZ channels, modulated with a PRBS7. Node B generates continuous 1x160 Gb/s RZ and 2x10 Gb/s NRZ data channels plus 52x10 Gb/s NRZ sub-λ data channels carrying PRBS7. Node C generates 20x10 Gb/s sub-λ PRBS32 data channels. Flexible channel spacing is used depending on channel bandwidth; namely, 50 GHz for the 10 Gb/s, 100 GHz for the 40 Gb/s NRZ, 150 GHz for the continuous 40 Gb/s RZ and 200 GHz for the 40 Gb/s sub-λ channels. The 160 Gb/s RZ signal requires a minimum spectrum allocation of 350 GHz. The OXC can support both 50/100 GHz ITU Grid spacing as well as Gridless/ arbitrary spectrum spacing and allocation. The sub-λ channels have data-unit durations and step size ranging from 0.97 ps (143 Mb/s@ 10Gb/s and 572Mb/s@ 40 Gb/s) up to 67.75 ps in a 67.84- ps frame and 90 ns inter data-unit gap needed for C-Band λ tuning (< 80 ns) and switching (10 ns).

The flexibility of the proposed adaptive node architecture is demonstrated in two scenarios with varied traffic load and switching requirements. Both architectures demonstrate multi bit-rate optical grooming and sub-λ multicasting. In addition, the flexibility in allocating spectrum, space and time resources is demonstrated in the 2^nd scenario where the node transparently switches continuous and sub-λ channels and as such is able to time-multiplex arbitrary spectrum among sub-λ channels of different bit rates (10Gb/s and 40Gb/s) and modulation formats.

In the first scenario, Node A transmits 4x40 Gb/s continuous NRZ and 10x40 Gb/s sub-λ RZ signals over the Ipswich link, some of which go to Node E and some to Node F as shown in Figures 8 and 9. Node B generates 54x10 Gb/s NRZ and one 160 Gb/s signal. The 160 Gb/s signal requires to be switched towards Node E together with 39 x 10 Gb/s channels, the 18 remaining go to Node F. Node C generates all its 20x10 Gb/s sub-λ channels with destination to Node G. The required architecture, shown in Figure 10, is implemented by establishing the cross-connections in the MEMS switch. A 1x4 100ms LCoS- based SSS that supports flexible spectrum allocation per port (multiple bands of 12.5-GHz up to 5-THz bandwidth in 1 -GHz steps) is used to switch the 160 Gb/s signal by programming a co-centered 600-GHz band to be passed from port 1 to its common port. Also, for the 10 Gb/s and 40 Gb/s signals destined towards Node E customized bandwidths per channel are used according to the required channel spacing. For the signals going to Node F, 150-GHz bandwidth (De)-Multiplexer are used to fit a 40 Gb/s channel and enable band switching of three 10 Gb/s channels per Band MUX/DEMUX port as in waveband switching (see, for example, O. Moriwaki, et.al,"Terabit-scale Compact Hierachical Optical Cross-connect System Employing PLC Devices and Optical Backplane", OFC, PDPC9, San Diego, USA, March 2010). Node C traffic is switched using a single MEMS cross-connection to Node G. In the second scenario, Node A traffic is increased by three continuous 40 Gb/s RZ and one sub-λ 40 Gb/s RZ channels. In order to free up spectrum for the new channels, three sub-λ 40 Gb/s channels are tuned to share the same λ with other sub-λ channels in time-domain. Therefore, data-units from Node A transmitted at the same λ but at different time intervals may have different destinations, and need to be switched independently. This new requirement of sub-λ switching is not accomplished by the previous scenario. Therefore, a new configuration (Figure 1 1 ) is implemented by re-configuring the MEMS switch. Thus, sub-λ data-units coming from A are switched at D using a 10-ns PLZT switch.

Those that go towards Node E are groomed with three sub-λ 10 Gb/s channels, that go to the same destination and use the same spectrum, selected on port 3 of the SSS and transmitted over the Chelmsford link. Data- units that go towards Node F are output on port 4 of the PLZT switch, amplified and replicated. Then, copies are input to the ports of the multiplexer that correspond to the Xs of the data-units. The minimum data rate switched with this architecture is a 10 Gb/s sub-λ channel transmitting one 0.97-με data-unit in the 67.84-ps frame (~143 Mb/s) and the maximum is the 160 Gb/s RZ continuous channel i.e. a multi-granularity factor greater than 1000. In both scenarios one10Gb/s channel is multicast to Node E and F. Both architectural scenarios are using a mix of multi-stage switching (1 &2 stages for scenario 1 and 1 , 2 & 3 stages for scenario 2). As such EDFAs are used internally to compensate the insertion loss of node paths and deliver a power balance of all channels per output port of less than 1.5 db.

Figure 12 shows the sub-λ 10&40 Gb/s data-sets switched from A and B to E and F together with their eye diagrams. The performance of the network was evaluated by measuring BER for the 10 Gb/s and 40 Gb/s continuous and sub- λ channels and Q-factor for the 160 Gb/s for the back-to-back, the OXC node and end-to-end (200km field fiber). In case of sub-λ channels data-unit sizes of 32ps and 5ps were measured for the 10 Gb/s and 40 Gb/s respectively. Results shown on Figure 13 illustrate that there is a maximum 2 dB node and 4.5 dB end-to-end penalty for all channels.

An adaptive OXC that dynamically synthesizes architectures tailored to traffic requirements able to support elastic allocation of arbitrary spectral and time resources has been demonstrated. The system is evaluated in a field trial and demonstrates the ability to switch up to 1.5 Tb/s based on continuous and sub- λ signals at 160 Gb/s, 40 Gb/s and 10 Gb/s, with a record 1000-fold all-optical bandwidth granularity factor. In what follows, the optical system according to the present invention is further described as part of a second field experiment.

An adaptable optical cross-connect that dynamically synthesizes a suitable architecture tailored to the requirements of existing traffic and supports elastic allocation of spectral resources and time-sharing of arbitrary spectrum is experimentally demonstrated. The system is used to transparently switch up to 1.5 Tb/s of traffic with all-optical granularities ranging from 155 Mb/s up to 170.8 Gb/s (a factor of 1100) in a field trial of seven nodes with deployed field fiber links.

The adaptable optical cross-connect consists of a 96x96 3D-MEMS optical switch and several architecture-building modules such as LCoS-based spectrum selective switch (SSS), 2x2 PLZT optical switch [Epiphotonics], wavelength de-multiplexer, waveband de-multiplexer/multiplexer, 1x4 splitters/couplers and EDFAs. Modules are attached to the 3D-MEMS switch so that the module's inputs connect to the optical switch outputs and the module's outputs connect to the optical switch inputs. Some of the 3D-MEMS optical switch inputs are reserved for OXC inputs and some for add ports. Similarly, some of the 3D-MEMS optical switch outputs are reserved for OXC outputs and some for drop ports according to the required node degree and add/drop capability. The 3D-MEMS optical switch interconnects inputs, modules and outputs by means of internal cross-connections.

During normal operation, the switching requirements of the optical signals at the input of the adaptable optical cross-connect are used to devise a suitable arrangement of the architecture-building modules that would provide the required functionality. The arrangement of inter-connected modules (i.e. the architecture) is then implemented by configuring the required cross- connections in the 3D-MEMS optical switch. Several architectures may be constructed ranging from a single 3D-MEMS optical switch cross-connection to the most complex involving all the attached architecture-building modules. Also, different architectures may be built for different inputs and may be dynamically changed by re-configuring the cross-connections in the optical switch.

The network scenario is the same as that displayed in Figures 8 & 9 and consists of three source nodes (Nodes A, B and C), one adaptable optical cross-connect (Node D) and three destination nodes (Nodes E, F and G). Nodes A and E are linked to Node D by dispersion compensated ITU-T G.652 field fiber sections of 80 km and 110 km deployed in the UK between the towns of Colchester-Ipswich and Colchester-Chelmsford respectively. Channels are generated at the source nodes and transmitted to Node D where they are switched to their destination node(s). At Node A, a multi-channel multi-format transmitter generates continuous 4x42.7 Gb/s NRZ and 3x42.7 Gb/s RZ plus sub-wavelength 8x42.7 Gb/s RZ channels, modulated with a pseudo-random bit sequence of length 2⁷-1 (PRBS7). Node B generates continuous 1x160 Gb/s RZ and 2x10 Gb/s NRZ plus 52x10 Gb/s NRZ sub-wavelength channels carrying PRBS7. Also, node C generates 20x10Gb/s sub-wavelength channels modulated with PRBS23. Several channel spacings are used depending on the required channel bandwidth; namely, 50 GHz for the 10 Gb/s, 100 GHz for the 42.7 Gb/s NRZ, 150 GHz for the continuous 42.7 Gb/s RZ and 200 GHz for the 42.7 Gb/s sub-wavelength channels. The 160 Gb/s RZ signal requires a minimum bandwidth allocation of 350Ghz. All sub-wavelength channels have data-unit durations ranging from 1 ps up to 63 ps in a 64-ps frame. The system architecture flexibility of the proposed approach is demonstrated in three scenarios where the traffic load is varied as well as the switching requirements of individual signals. Additionally, the flexibility in allocation of spectrum and time resources is demonstrated in the third scenario where the system transparently switches continuous channels and time-multiplexes arbitrary spectrum among sub-wavelength channels of different bit rates and modulation formats.

In the first scenario, only some of the signals generated by the source nodes are active. From Node A, 5x42.7 Gb/s sub-wavelength and 1x42.7 Gb/s NRZ continuous channels are generated and transmitted over the Ipswich link (80 km of deployed fiber). They all require to be switched through towards Node E over the Chelmsford link ( 10km field fiber). Node B generates only 8x10 Gb/s sub-wavelength, some of which go to Node E and some to Node F. Node C generates all its 20x10 Gb/s sub-wavelength channels, which destination is Node G. The architecture required to provide this switching functionality, is the same as that shown in Figure 4 (and also shown in Figure 14), and is implemented by establishing the required cross-connections in the 3D-MEMS switch. It uses one de-multiplexer to split the signals from Node B, multiplexer to re-combine the signals towards Node F, amplifier and two couplers to merge the signals towards Node E. Switching the channels from Node C to Node G requires only one cross-connection in the 3D-MEMS optical switch. At Node D all signals are successfully switched through towards their destination as shown in the spectrum plots in Figure 14. It is important to note that this is not a fixed architecture but can be re-configured by setting up different cross- connections in the 3D-MEMS optical switch, with a re-configuration time of 20ms per cross-connection, as will be evident from the following scenarios. In the second scenario, additional traffic is generated. Node A transmits continuous 4x42.7 Gb/s NRZ and 10x42.7 Gb/s RZ sub-wavelength signals, some of which go to Node E and some to Node F. Node B generates 54x10 Gb/s NRZ and one 160 Gb/s signal. The 160 Gb/s signal requires to be switched towards Node E along with some of the 0 Gb/s channels, the rest go to Node F. Traffic from Node C does not change from the previous scenario. The architecture used in Scenario 1 is not suitable for the new switching requirements due to the non-standard bandwidth requirement of the 160 Gb/s signal and the need to split the channels coming from Node A and switch some to Node E and some to Node F. Therefore, a new architecture is created and implemented by rearranging the cross-connections in the 3D-MEMS optical switch, as shown in previous Figure 10 and in Figure 15. In the new architecture an LCoS-based Spectrum Selective Switch (SSS) that supports flexible spectrum allocation per port (multiple bands of 12.5-GHz up to 5-THz bandwidth in 1 -GHz steps) is used to switch the 160 Gb/s signal by programming a co-centered 600-GHz band to be passed from port 1 to its common port. Also, for the 10 Gb/s and 42.7 Gb/s signals destined towards Node E customized bandwidths per channel are used according to the required channel spacing. For the signals going to Node F, 150-GHz bandwidth multiplexer and de-multiplexer are used which can fit a 42.7 Gb/s channel and enable switching the 10 Gb/s channels in groups of three channels per MUXIDEMUX port as in waveband switching.

In the third scenario, traffic coming from Node A is increased by adding three continuous 42.7 Gb/s RZ and one sub-wavelength 42.7 Gb/s RZ channels. In order to free up spectrum for the new channels three sub-wavelength 42.7 Gb/s channels are re-tuned to share the same wavelength with other sub- wavelength channel. Therefore, now data-units from Node A transmitted at the same wavelength but at different time intervals may have different destinations, and need to be switched independently. This new requirement of sub- wavelength grooming is not accomplished by the architecture used for Scenario 2. Therefore, a new configuration, shown in previous Figure 11 and in Figure 16, is calculated and implemented by re-configuring the cross-connection in the 3D-MEMS switch. With the new architecture, data-units coming from Node A are segregated at Node D using a 10-ns PLZT switch. Those that go towards Node E are groomed with three sub-wavelength 10 Gb/s channels, that go to the same destination and use the same spectrum, selected on port 3 of the SSS and transmitted over the Chelmsford link. Data-units that go towards Node F are output on port 4 of the PLZT switch, amplified and replicated. Then, copies are input to the ports of the multiplexer that correspond to the wavelengths of the data-units. The minimum bit-rate switched with this architecture corresponds to a 10 Gb/s sub-wavelength channel transmitting one 1-με data-unit in the 64- με frame (-155 Mb/s) and the maximum is the 170.8 Gb/s RZ continuous channel i.e. a multi-granularity factor of 1100.

The performance of the network was evaluated by measuring BER for the 10Gb/s and 42.7 Gb/s channels and Q-factor for the 170.8 Gb/s. Sub- wavelength channels with data-unit sizes of 32 με and 5 ps were measured for the 10 Gb/s and 42.7 Gb/s respectively. Results for Scenario 3 are shown in Figure 16. An adaptable optical cross-connect that dynamically synthesizes architectures tailored to the requirements of existing traffic and supports elastic allocation of spectral resources and time-sharing of arbitrary spectrum has been experimentally demonstrated. The system is shown in a field trial to be able to switch up to 1.5 Tb/s traffic from CS signals at 170.8 Gb/s, 42.7Gb/s and 10 Gb/s, with a record all-optical multi-granularity factor of 1100.

Having described now the preferred embodiments of this invention, it will be apparent to one of skill in the art that other embodiments incorporating its concept may be used. It is felt, therefore, that this invention should not be limited to the disclosed embodiments, but rather should be limited only by the scope of the appended claims.

Claims

1. Optical system including:

- at least one optical system input (12) for receiving an input optical signal;

- at least one optical system output (14) for outputting an optical signal;

- an optical switch (1 ) including a plurality of inputs (8) for receiving an optical signal and a plurality of outputs (10) for outputting an optical signal, the optical switch (1 ) being configured to transfer an optical signal from any one of the optical switch inputs (8) to any one of the optical switch outputs (10);

- a plurality of modules (2) for processing an optical signal, each module (2) of the plurality of modules being configured to carry out a specific optical signal processing and includes at least one input (4) for receiving an optical signal to be processed and at least one output (6) for outputting a processed optical signal, the at least one input (4) of each module being optically connected to an output (10) of the optical switch (1 ), and the at least one output (6) of each module (2) being optically connected to an input (8) of the optical switch (1);

an input (8) of the optical switch (1 ) other than that used for a module (2) is used as the at least one system input (12) and an output (10) of the optical switch (1 ) other than that used for a module (2) is used as the at least one system output (14),

wherein the optical system is configured to establish an optical path (OPP), along which an optical signal is routed, between the at least one optical system input (12) and the at least one optical system output (14) that includes at least one module (2) selected amongst the plurality of modules (2) for processing an optical signal received at the at least one system input (12).

2. The optical system according to claim 1 , wherein the optical system is further configured to dynamically reconfigure the established optical path.

3. The optical system according to any previous claim, wherein the optical system is configured to establish an optical path that includes a sequence of optically connected modules selected amongst the plurality of modules.

4. The optical system according to claim 3, wherein the optical system is configured to dynamically reconfigure the sequence of connected modules so as to redefine the optical path along which an optical signal is routed.

5. The optical system according to any previous claim, wherein the optical system includes a plurality of system inputs (12) and a plurality of system outputs (14), and the optical system is configured to establish an optical path that includes at least one module (2) selected amongst the plurality of modules (2) from each system input (12) to anyone of the plurality of system outputs (14) for processing an optical signal received at each system input (12).

6. The optical system according to claim 5, wherein the optical system is configured to dynamically reconfigure each optical path established from each system input (12).

7. The optical system according to any previous claim, wherein the optical system is configured to calculate a configuration of connections between the at least one optical system input (12) and the at least one optical system output (14) that includes at least one module (2) selected amongst the plurality of modules (2) for processing an optical signal received at the at least one system input (12), and to reconfigure the optical switch to implement the calculated configuration of connections.

8. The optical system according to any previous claim, wherein the optical system is configured to receive a request relative to an optical signal requirement concerning an optical signal to be received at a system input, and includes a system controller (18) configured to evaluate whether the request can be supported using the currently established optical system configuration or whether a reconfiguration is necessary.

9. The optical system according to claim 8, wherein the system controller (18) is configured to determine whether an alternative optical system configuration can be established for the received request, and to reconfigure the optical system to said alternative system configuration.

10. The optical system according to any previous claim, wherein each module (2) of the plurality of modules is configured to carry out at least one of the following optical signal processing: multiplexing, de-multiplexing, amplification, optical signal regeneration, wavelength conversion, optical switching, power coupling, power splitting, optical filtering, format conversion, synchronisation, delaying, buffering, modulation, de-modulation, non-linear processing, and signal generation.

11. The optical system according to any previous claim, wherein each module (2) of the plurality of modules is configured to carry out a different type of optical signal processing.

12. The optical system according to any previous claim, wherein the optical system is configured to process the input optical signal received at the at least one system input (12) and output the processed optical signal at the at least one system output (14) without conversion of the optical signal into an electrical signal.

13. The optical system according to any previous claim, wherein the optical system is configured to control the optical switch (1 ) to direct the input optical signal at the at least one system input (12) to an input of a module (2) and to direct the processed optical signal exiting said module (2) to the input (4) of the next module (2) in a sequence of optically connected modules, or when the processed optical signal has exited the only module (2) or last module (2) of a sequence of modules, to direct said processed optical signal to the at least one system output (14).

14. Method for controlling an optical system, the optical system including:

- at least one optical system input (12) for receiving an input optical signal;

- at least one optical system output (14) for outputting an optical signal;

wherein the optical system is configured to establish an optical path (OPP), along which an optical signal is routed, between the at least one optical system input (12) and the at least one optical system output (14) that includes at least one module (2) selected amongst the plurality of modules (2) for processing an optical signal received at the at least one system input (12);

the method including the steps of:

- receiving a request relative to an optical signal requirement or an optical signal processing requirement concerning at least an optical signal to be received at the at least one system input or generated by one of the system modules;

- evaluating whether the request can be supported using the currently configured optical system, or whether a reconfiguration of the currently configured optical system is necessary;

- If the request can be supported using the currently configured optical system, accepting the request; - when a reconfiguration of the currently configured optical system is necessary, calculating an alternate optical system configuration and determining whether the alternative optical system configuration can be established to implement the received request; and

- reconfiguring automatically the optical system to the calculated alternative optical system configuration when the alternative optical system configuration can implement the requirements of the received request.

15. Computer program for a processing unit comprising a set of instructions which, when loaded into the processing unit, causes the processing unit to carry out the steps of the method as claimed in claim 14.