Optical System Comprising a Reconfigurable Device and Optical System Control Method

Abstract

An optical system (100) is described, which includes a reconfigurable optical device (103) having multiplexed wavelength division, the reconfigurable optical device (103) including a plurality of actuators (A1-AN) associated with a number of optical channels (M) and a number of degrees of freedom (N) less than the number of optical channels, and an optical stimulus signal (S) having a wavelength band including a plurality of wavelengths associated with the optical channels. in an optical stimulus source (106) connected to the reconfigurable optical device (103) to provide an optical stimulus signal (S); and an optical stimulus source (106) connected to the reconfigurable optical device (103) to provide an optical stimulus signal (S in ) corresponding to the optical monitoring signal (S out ) and an optical monitoring signal (S out ) are a group of electrical signals (S EL1 ~S ELK ) and a photoelectric conversion device (200) configured to provide said group of electrical signals (S EL1 ~S ELK ) and a control device (110) configured to control the plurality of actuators (A1 to AN) according to a control law.

Description

Technical Field

[0001] The present invention relates to a method for controlling a reconfigurable optical device that can be used, for example, but not limited thereto, in an electrical communication sector within a reconfigurable optical network.

Background Art

[0002] An example of a reconfigurable optical device is described in U.S. Patent No. 6,892,021. This document describes an optical gain equalizer filter having a waveguide grating router with Mach-Zehnder adjustable optical attenuators respectively associated with the relative wavelengths of the optical channels used.

[0003] Furthermore, the document "Smart dynamic wavelength equalizer with on-chip spectrum analyzer" by Schiffer, P.M.J., et al., IEEE Photonics Technology Letters 12.8 (2000): 1019 - 1021 describes a dynamic wavelength equalizer that uses two WGRs and feedback control via a spectrum analyzer.

[0004] In addition, the document "Design and analysis of a control system for an optical delay-line circuit used as reconfigurable gain equalizer" by Schlipf, T.R., et al., Journal of lightwave technology 21.9 (2003): 1944 describes an open-loop control system for a reconfigurable gain equalizer formed by a two-port lattice optical delay-line circuit.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Literature

[0006]

Non-Patent Literature 1

Non-Patent Literature 2

Summary of the Invention

[0007] The applicant of the present application notes that the known closed-loop control technology is too complex both in terms of calculation and in relation to the structure of the control circuit.

[0008] The present invention addresses the problem of providing an optical system that shows a control technology for a reconfigurable device of the system itself, which is not particularly troublesome in terms of calculation and is not complex from a structural point of view.

[0009] According to a first aspect, the object of the present invention is the optical system according to claim 1 and its preferred embodiments defined in claims 2 - 15.

[0010] Another object of the present invention is also a method for controlling the optical system according to claim 16.

[0011] The present invention will be described in detail below by way of example and not limitation with reference to the accompanying drawings.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0013] In this description, similar or identical elements or components are shown in the figures with the same reference symbols.

[0014] FIG. 1 schematically shows a first embodiment of an optical system 100 including a reconfigurable optical device 103, a control device 110 (CONT-DEV), a light source 106 (OP-SR), and a photoelectric conversion device 200.

[0015] In particular, the optical system 100 is such that it operates with electromagnetic radiation having a wavelength between 300 nm and 5000 nm, preferably between 1480 nm and 1620 nm.

[0016] For example, the optical system 100 is a system that operates in the field of optical communication, particularly in a reconfigurable optical network.

[0017] The reconfigurable optical device 103 (abbreviated as reconfigurable device) operates according to the WDM (wavelength division multiplexing) technique with a plurality of M optical channels (at least two optical channels), that is, M optical signals having carriers of different wavelengths.

[0018] In particular, the reconfigurable device 103 includes at least one adjustable optical element Gi (such as an optical delay line, an adjustable optical coupler, or an adjustable attenuator, etc.) configured to operate with WDM. As an example, a single adjustable optical element Gi having M channels or a plurality of adjustable optical elements Gi operating with M channels can be used.

[0019] The reconfigurable device 103 also includes a plurality of N actuators A1 to A N and this plurality of actuators is associated with the adjustable optical element Gi and modifies the optical properties (such as the refractive index and / or attenuation of the medium in which the adjustable device 103 is fabricated) according to the corresponding control signals S1 to S N supplied by the control device 110. The reconfigurable device 103 can take on a discrete number of states according to the values of its N state variables θ1,..., θ N controlled by the N control signals S1 to S N .

[0020] It should be noted that the N actuators A1 to A N define the number of degrees of freedom of the reconfigurable device 103, that is, the number of independent variables required to completely determine the state of the reconfigurable device 103 itself.

[0021] Advantageously, the number N of degrees of freedom of the reconfigurable device 103 is less than the number M of channels in which the reconfigurable device itself operates.

[0022] Actuators A1 to A NIt can be such as to induce a change in the optical parameters (e.g., phase or amplitude) of the associated adjustable optical element Gi. For example, the following devices can be used as actuators A1 to A N : thermo-optical, electro-optical, piezoelectric, electro-absorptive, electromechanical, electrochemical, or all-optical actuators (regardless of whether based on non-linear optical effects).

[0023] Regarding an exemplary sector of a reconfigurable optical network, the reconfigurable device 103 can be, for example, an optical filter, an equalizer filter, a dispersion compensator filter, a FIR filter, an IIR filter, a lattice filter, a binary tree filter.

[0024] For example, the reconfigurable device 103 can be fabricated using integrated waveguide technology on an optical platform (or optical chip). Some examples of optical platforms that can be used include semiconductor platforms (e.g., silicon, indium phosphide, gallium arsenide), amorphous glasses (silicon dioxide, silicon nitride, silicon oxyfluoride, silicon oxycarbon, silicon carbide), polymers and crystals (lithium niobate) optionally integrated with two-dimensional materials (graphene, silicene), and their possible hybrid integrations.

[0025] According to the example of FIG. 1, the reconfigurable optical device 103 is a device having at least four optical ports. More specifically, the reconfigurable optical device 103 includes an optical input port 101 and an optical output port 102. The optical input port 101 is configured to receive a plurality of M optical input signals that are multiplied by the input signal I, and the optical output port 102 is configured to transmit an optical output signal O, particularly the multiplied M optical output signals, as a result of the operation of the reconfigurable optical device 103.

[0026] In addition, the reconfigurable optical device 103 includes an optical stimulation port 111 connected to a light source 106 and an optical monitoring port 112 connected to a photoelectric conversion device 200.

[0027] The plurality of M optical input signals within the input signal I occupy the entire band Δλ that specifies the operating wavelength range of the reconfigurable device 103.

[0028] In particular, referring to the linear mode application, in each state specified by the state variables θ1,..., θ N the reconfigurable device 103 behaves as a time-invariant linear system in each of the states it can take.

[0029] The transmission of the input signal I from the optical input port 101 to the optical output port 102 can be described via the frequency response H 12,i (f) of the reconfigurable device 103, or equivalently by the wavelength response H 12,i (λ), where the subscript "i" indicates the general state that the device itself takes.

[0030] The light source 106 is configured to generate an optical Si n stimulating signal supplied to the stimulation port 111. The light source 106 is configured to emit optical radiation over a wavelength range that is equal to or greater than the operating wavelength Δλ range of the reconfigurable device 103. The optical monitoring port 112 is configured to provide an optical monitoring signal S in as an output corresponding to the optical stimulating signal S out .

[0031] In the case of an integrated optical device, the light source 106 can be integrated on the same optical platform (i.e., an optical chip) as the reconfigurable device 103, or can be external to that platform and connected to the reconfigurable device 103 via an optical fiber.

[0032] Preferably, the light source 106 comprises a superluminescent diode (SLD), but other broadband light sources can be used, such as, for example, the "amplified spontaneous emission" noise (ASE noise) of a fiber amplifier (e.g., Erbium-doped fiber amplifier, EDFA) or a semiconductor optical amplifier (SOA), from a "super-continuous laser" type light source, from a laser array (e.g., Distributed Laser Feedback, DFB), a comb spectral array (comb) generated by a fiber comb generator or integrated on an optical chip.

[0033] The photoelectric conversion device 200 converts the monitoring optical signal S ou t and the supervisory signal S evaluated in terms of relative wavelength out A set of electrical intensity signals S, each of which represents the intensity of EL1 ~S ELN (e.g., on electrical terminal 108). A set of intensity electrical signals S EL1 -S ELK It should be noted that has a cardinality equal to K. Preferably, this cardinality K is equal to N, i.e., the group S of intensity electrical signals EL1 ~S ELK has a cardinality equal to the number of degrees of freedom of the reconfigurable device 103.

[0034] According to a particular example shown in FIG. 1 again, the photoelectric conversion device 200 includes a spectral range selector 105 (SP-SL), hereinafter also called a spectral slicer, and a photoelectric converter 104 (DET-ARR). The spectral slicer 105 is a out It has a corresponding optical input port connected to an optical monitoring port 112 for receiving a monitoring signal, and a number of optical output ports 109 (K optical ports 109, preferably K=number N degrees of freedom).

[0035] The spectral slicer 105 detects the kth wavelength λ k The monitoring signal S centered on out The selected S corresponds to a part of outk The optical signal is configured to be transmitted to its general kth output port.

[0036] The spectral slicer 105 used to select the K wavelengths k to be monitored can be implemented according to different technical and architectural solutions. For example, the spectral slicer 105 is λ k a passive device that does not require external active control for wavelength selection.

[0037] Possible architectures that can be used for the spectral slicer 105 include Array Waveguide Gratings (AWG), echelle gratings, and other types of interference filters such as Mach Zehnder interferometers, Bragg gratings, ring resonators, and any combination thereof.

[0038] The spectral slicer 105 is preferably fabricated in a waveguide and, for example, integrated on the same optical platform as the reconfigurable optical device 103. The spectral slicer 105 can also be implemented with alternative technologies, for example, using individual optical components, optical fiber components, and combinations thereof in free space.

[0039] According to this example, the 104 photoelectric converters include a plurality of photodetectors configured to convert the K sampled optical signals S out (λ k ) into K electrical signals S of intensity EL1 ~S ELK .

[0040] The control device 110 is configured to control the plurality of actuators A1~A EL1 ~S ELK while generating N control signals S1~S N according to a pre-established control rule according to the set of intensity electrical signals S N .

[0041] Regarding the control law, for the purpose of reconfigurability, the control device 110 operates such that the i-th state taken by the reconfigurable device 103 is as close as possible to the i-th "desired" state under the operating conditions. For example, the control device 110 uses a method to minimize the mean square error between the actual transfer function of the reconfigurable device 103 and the desired transfer function of the reconfigurable device 103 for a plurality of control signals S1 to S N is defined as such.

[0042] The control device 110 can be realized, for example, by a microcontroller, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and is programmed according to the control method described below.

[0043] Note that the optical system 100 can also include an optical device 300 (APP) operably associated with the reconfigurable optical device 103.

[0044] For example, the optical device 300 can be an optical amplifier (especially of the doped fiber type) that enables long-distance transmission of optical signals without photoelectric conversion and regeneration. Optical amplifiers generally operate with a large number of optical signals, for example, more than 100 signals.

[0045] According to this example, the reconfigurable optical device 103 can be an equalizer filter, and this equalizer filter is configured to equalize the gain band of the erbium-doped fiber of the optical amplifier 300 that does not have a constant gain over the entire frequency range occupied by the signal.

[0046] The use of the reconfigurable equalizer filter 103 makes it possible to adapt the optical amplifier 300 to the requirements of a reconfigurable optical network. For example, in the case of an erbium-doped fiber optical amplifier 300, the reconfigurable equalizer filter 103 can have a number of degrees of freedom N = 20 and operate with a number of optical channels M = 100.

[0047] Hereinafter, an example of a control method that can be used by the optical system 100 to reconfigure the reconfigurable device 103 will be described.

[0048] Referring to the wavelength region, the optical output signal O(λ) supplied to the optical output port 102 is given by the following equation. O(λ)=H 12、i (λ)I(λ) (1) Here, I(λ) is the input signal I represented in the wavelength region, and H 12、i (λ) is the already defined wavelength response of the reconfigurable device 103, and the subscript "i" indicates the general state taken by the device itself with respect to the transmission of the input signal I from the input optical port 101 to the output optical port 102.

[0049] To facilitate the understanding of the following mathematical notations, in FIG. 1, the numbers 1, 2, 3, and 4 are added in parentheses to the relevant optical ports of the reconfigurable device 103.

[0050] The control method starts when there is a request to reconfigure the optical system 100, particularly the reconfigurable device 103.

[0051] As already described, the control method to be explained is such that the effective wavelength response taken by the reconfigurable device 103 under operating conditions

Number

[0052] The optical stimulation signal S generated by the light source 106 in measures the actual state H i、e (λ) in real time, and the desired state H i、dTo evaluate the deviation (i.e., distance) with respect to (λ), it is supplied to the input of the stimulation port 111 of the reconfigurable device 103.

[0053] Desired H i,d It should also be noted that the (λ) state is specified in advance and stored, for example, in a look-up table in the control device memory 110, but can be dynamically updated and changed during the operation of the reconfigurable device 103.

[0054] The reconfigurable device 103 receives the stimulation signal S in and returns the monitoring signal S out (λ) to the optical monitoring port 112. The optical monitor signal S out (λ) is described by the following relationship. S out (λ)=H 34,i (λ)S in (λ) (2)

[0055] Function H 34,i (λ) specifies the transfer function of the reconfigurable device 103 from the stimulation port 111 to the monitoring optical port 112 when the device itself is in the i-th state associated with the transfer function H 12,i (λ) for transmission from the input optical port 101 to the output optical port 102.

[0056] For the purposes of the following explanation, it should be noted that the reconfigurable device 103 is considered to have the following characteristics defined below according to the transfer function between the optical ports of the device itself. - Reciprocal: H mn,i (λ)=H nm,i (λ); - No retroreflection at all optical ports (101, 102, 111, 112): H 11,i (λ)=H 22,i (λ)=H 33,i (λ)=H 44,i (λ)=0; - No coupling between ports 1 to 4 (H 14、i (λ)=H 41,i (λ)=0) and no coupling between ports 2 to 3 (H23,i H(λ) = 32,i (λ) = 0); - There is no leakage.

[0057] In the characteristics shown above, the term "none" is to be understood as meaning that the retroreflection, coupling or loss shown above is invalid or negligible for the purposes of the following discussion.

[0058] As will be appreciated by those skilled in the art, the characteristics described above apply to the following relationships. |H 12,i (λ)| 2 + |H 13,i (λ)| 2 = 1 |H 31i (λ)| 2 + |H 34,i (λ)| 2 = 1 From this, |H 12,i (λ)| 2 = |H 34,i (λ)| 2 (3) can be understood.

[0059] Relationship (3) shows how the optical monitoring signal S related to the transfer function |H 34,i (λ)| 2 provides the same information as the direct monitoring of the optical output signal O(λ) related to the transfer function |H out(λ) monitoring related to 12,i (λ)| 2 .

[0060] Considering the reciprocal of the reconfigurable device 103, the transfer function |H 34,i (λ)| 2 e|H 43,i (λ)| 2They are theoretically identical and both can be monitored. However, in practice, it is convenient to use a stimulation signal that propagates in the opposite direction (backpropagation) to the signal of interest. In fact, in the case of a co-propagating signal, the reconfigurable device 103 is involved in the crosstalk phenomenon and part of the input stimulation signal can be transmitted from port 4 towards port 2. Therefore, the backpropagation configuration is preferred, even if it is not the only possible configuration.

[0061] Since the spectrum of the Sin(λ) stimulation signal is known, the transfer function H 34,i (λ) can be directly derived from the monitoring signal S out (λ) at the monitoring port 112 through the relationship (2).

[0062] Also, it should be noted that the system 100 preferably operates based on the knowledge of the spectrum of the signal S out (λ) for only K wavelengths, where K is preferably equally spaced and preferably equal to the number N of degrees of freedom of the device 103 (K = N).

[0063] Signal S out It should be noted that the number K of wavelengths for which the spectrum of (λ) is considered can also be selected to be greater than the number N of degrees of freedom: K > N. In this case, the system 100 is particularly robust against noise but is more complex than when K is equal to N.

[0064] On the other hand, if a number K (K < N) less than the number of degrees of freedom is selected, the system 100 will exhibit worse performance than when K ≥ N.

[0065] The number K can be between a minimum Kmin and a maximum Kmax value. For example, the minimum value can be given by Kmin = N - 20%N or Kmin = N - 5%N. For example, regarding the maximum value, Kmax = N + 100%N, or Kmax = N + 50%N, or Kmax = N + 20%N.

[0066] Regarding the selection of the number K, it should be noted that in system 100, it is not necessary to be equal to the number of optical channels M, and it may be less than the number of optical channels M, or even much less (K < M). For example, when the reconfigurable device 103 is used in an amplification system having M = 130 channels, the number of wavelengths K to be monitored may be less than 15%, that is, K < 15%M. Other possible example values are K < 50%M and K < 30%M.

[0067] The number K is selected by appropriately combining both the above-mentioned relationship regarding the number of degrees of freedom N and the above-mentioned relationship regarding the number of optical channels M, considering the trade-off between robustness and complexity according to the application.

[0068] Furthermore, regarding the control method, it should be noted that it is sufficient to know only the intensity of the optical monitoring signal |S out (λ)| 2 at various wavelengths, rather than its phase.

[0069] Therefore, the information used by the control device 110 is the intensity of the optical monitoring signal. |S out (λ k )| 2 (4) where the subscript k = 1, 2,... K indicates the discrete frequencies at which the spectral power density |S out (λ)| 2 is sampled.

[0070] The spectral slicer 105 receives the monitoring optical signal S out (λ) and transmits the sampled optical signal S k corresponding to a part of the monitoring optical signal S out (λ) centered at the k-th wavelength λ out (λ k ) to each associated output port 109. In particular, the spectral slicer 105 provides a plurality of sampled optical signals S S1 ~S SK in parallel mode on its output port 109.

[0071] FIG. 2 refers to a numerical simulation and shows, for example, the signal S for a possible configuration of the reconfigurable device 103 out (λ) spectrum 702, and the same signal and its sub-bands S each having its own band B λ,k respectively out (λ k ) and a segmented version 701 thereof

[0072] Each optical output 109 of the spectral slicer 105 is optically connected to the photodetector of the photoelectric converter 104 that measures the input optical intensity, and the optical monitoring signal S integrated into its own sub-band B λ,k respectively out (λ k ) having an electrical signal S proportional to the intensity |S out (λ k )| 2 is provided on the associated terminal 108. The photoelectric converter 104 generates N electrical signals S ELj ~S EL1 ~S ELN in parallel to a plurality of terminals 108

[0073] The plurality of electrical signals S EL1 ~S ELK are transmitted to the control device 110, and the control device monitors in real time the effective frequency response taken by the reconfigurable device 103 in the operating state at the k-th wavelength λ k respectively

Number

Number

[0074] The control device 110 changes the current state

Number

[0075] For example, the determination of the control signals S1 to S N can be carried out according to a method of minimizing the mean square error, based on the current state

Number

[0076] During the initialization stage of the optical system 100, the values of the control signals S1 to S N applied can be obtained from a look-up table obtained from the numerical simulation of the reconfigurable device 103. When these values are applied to the reconfigurable device 103, the method described above is applied to bring it to the desired state indicated by the look-up table.

[0077] Simulation FIG. 3 shows a numerical simulation showing the effectiveness of the optical system 100. Consider a general reconfigurable device 103 having 15 degrees of freedom N = 15. In this simulation, the reconfiguration of the device 103 is considered such that its frequency response in the wavelength range between 1528 nm and 1568 nm can take three predetermined trends (301, 302, 303). Starting from an arbitrary initial configuration, if we want to bring the reconfigurable device 103 to the i-th state (301, 302 or 303), the mean square error

Number

Number

[0078] In this simulation, the inventors first applied the methods of the prior art and accordingly, the transfer functions |H 12,i (λ k )| 2 measured at a number of wavelengths (white circles) (K = M = 130) equal to the number of optical channels used in the target wavelength range, in three different states (301, 302, and 303). By applying this conventional method, the curve shown in FIG. 3 by the dashed line was obtained.

[0079] Instead, the control methodology described with reference to the optical system 100 is applied to measure the transfer function |H 12,i (λ k )| 2 at a limited number of wavelengths (K = N = 15) equal to the number of degrees of freedom of the reconfigurable device 103 (complete circle). By applying the method described with reference to the system 100, the curve shown in FIG. 3 by the continuous line was obtained.

[0080] FIG. 3 shows that the difference between the dashed curve (conventional method) and the continuous curve (method of system 100) is less than 0.2 dB over the entire operating bandwidth, confirming the efficiency of the described method.

[0081] According to another embodiment of the optical system 100 schematically shown in FIG. 4, the photoelectric conversion device 200 is realized by a wavelength-variable monitor, and the wavelength-variable monitor is an optical monitoring signal S outStarting from, continuously over time (i.e., in serial mode), a set S of electrical signals of intensity is supplied to the control device 110 EL1 ~S ELN is configured to supply.

[0082] This wavelength-variable detector 200 includes, according to one example, a wavelength-variable optical filter 205 (TUN-FIL) having a single optical output 209 and, following it, a photodetector 204 (DET) having a single electrical output 208. The wavelength-variable detector 200 is a passive device that receives an external active control (S k control signal) for selecting the wavelength. CR is a passive device that receives an external active control (S

[0083] The optical output 209 of the wavelength-variable optical filter 205 is optically connected to the photodetector 204, which measures the input optical intensity and provides an electrical signal S out (λ k )| 2 having a current or voltage proportional to. ELk to provide.

[0084] By sequentially adjusting the wavelength-variable detector 200 over time, information regarding the current transfer function of the reconfigurable device 10 around all frequencies of interest

Number

[0085] The electrical S EL1 ~S ELK signals sequentially output from the photodetector 204 are sent to the control device 110 to provide monitoring of the actual frequency response

Number

[0086] Possible architectures that can be used for the wavelength - tunable optical filter 205 include optical ring resonators, Mach - Zehnder interferometers, Bragg gratings, and possible combinations thereof.

[0087] The wavelength - tunable detector 200 is preferably realized within a waveguide and is preferably integrated on the same photonic platform as the reconfigurable optical device 103 already described, or can be realized by separate optical elements, optical fiber components, and combinations thereof in free space.

[0088] For example, to adjust the wavelength - tunable optical filter 205, an electrical control signal S (generated by the control device 110) CR can be used, which acts on an actuator (not shown) incorporated in the wavelength - tunable optical filter 205. These actuators change the behavior of the wavelength - tunable filter 205, for example, by changing the optical parameters of the material medium through which the optical radiation propagates, utilizing, for example, the thermo - optical effect, the electro - optical effect, or the elasto - optical effect. Alternatively, a micro - mechanical actuator (MEMS) that changes the path of the optical radiation within the device can be used.

[0089] FIG. 5 shows a numerical simulation of an optical system 100 similar to that described in FIG. 4, including the wavelength - tunable optical filter 205.

[0090] The curve 802 in FIG. 5 shows the spectrum of the optical monitoring signal S out (λ) for a particular configuration of the reconfigurable optical device 103. FIG. 5 also shows the optical monitoring signal having its band B λ,k obtained through the wavelength - tunable filter 205 that can be adjusted over the entire operating band, and a “sampled” version of its sub - bands (curve 801).

[0091] FIG. 6 schematically shows a further optical system 400 that is similar to the optical system 100 already described with reference to FIG. 1, but uses a reconfigurable optical device 103 having two ports (input optical port 101 and output optical port 102).

[0092] The further optical system 400 includes a first circulator 401 and a second optical circulator 402. The first optical circulator 401 includes a first port 403 for an input signal I and a second port 404 connected to the optical input port 101 of the reconfigurable device 103 to which the input signal I can be supplied. The optical input port 101 of the reconfigurable device 103 is also such that it supplies a monitoring optical signal S to the second port 404 of the first optical circulator 401. The circulator 401 of the first one is connected to a spectrum slicer 105 and includes a third port 405 for supplying the optical monitoring signal S to the spectrum slicer. out is supplied. out to supply.

[0093] The second optical circulator 402 includes a related first port 406 connected to the output port 102 of the reconfigurable device 103. The optical output port 102 is such as to supply an output signal O to the second optical circulator 406 and is such as to receive a stimulation signal S. in to receive.

[0094] The second optical circulator 402 also includes a relative second port 407 configured to supply the output signal O, and a related third port 408 configured to receive the stimulation signal S generated by the light source 106 and transmitted to the corresponding first port 406 and then (via the output port 102) to the reconfigurable device 103. in to receive.

[0095] When the reconfigurable two-port optical device 103 is the reciprocal, the transfer function H 21 is equal to the transfer function H 12 is equal to.

[0096] Note that the structure having the reconfigurable two-port optical device 103 provided with two optical circulators 401 and 402 is also applicable to the form of the structure of FIG. 4.

[0097] FIG. 7 is a schematic diagram of an optical grating filter 203 showing an example of the reconfigurable device 103.

[0098] The optical grating filter 103 includes a plurality of optical couplers K1 to K14 and a plurality of actuators Bal1, 2... 7 and Unbal1, 2,... 6 suitable for introducing delay or imbalance into the optical channels for a total of 13 actuators.

[0099] The grating filter 103 in FIG. 7 has a number of degrees of freedom N equal to 13, i.e., equal to the number of actuators used, and can process up to a number M of optical channels equal to 96. By monitoring only the number K of wavelengths equal to N = 13, it is possible to manage the reconfigurability of the grating filter 103.

[0100] The optical couplers K1 to K14 are an example of the optical element Gi described with reference to FIG. 1, and the plurality of actuators Bal1, 2... 7 and Unbal1, 2,... 6 are A1 to A described with reference to FIG. 1 N An example of an actuator.

[0101] Note that each of the actuators Bal1, 2... 7 and Unbal1, 2,... 6 acts on the optical behavior of the corresponding Kj optical coupler operating in the WDM mode, i.e., enables the propagation of some optical channels.

[0102] Generally, the reconfigurable device 103 can be an optical filter including, as the optical element Gi, a binary tree or a lattice interferometer, an AWG (arrayed waveguide grating), or a similar structure used as a power divider, for example, a multimode interferometer (MMI), a directional coupler, or a y-branch.

[0103] The solutions described above are mainly applicable in the telecommunications industry, particularly in the field of reconfigurable optical networks, but it should be noted that they are not exclusive. Other possible applications of the lessons described are as follows: 1) Optical devices for both fiber optic sensors and waveguide sensors that require stabilization of the optical circuit to process sensor readings, 2) Optical devices for distance measurement such as LIDAR that require a very wide operating temperature range and can utilize the stabilization obtained by the present invention, 3) Optical circuits for 5G wireless networks that can utilize photonic circuits to improve the performance of mobile network coverage, for example, using a beamforming network having an integrated photonic circuit controlled by the method described in the present invention, 4) Reconfigurable optical circuits that can introduce adjustable delay times, for example, used in optical interferometry, optical tomography, and other applications where it is necessary to synchronize the relative delays between two or more optical signals.

[0104] The optical systems described above are particularly advantageous in terms of simplicity and performance. In fact, these optical systems make it possible to manage their reconfiguration by monitoring a number of signals (i.e., the sampled optical signals S S1 ~S SK ) that is less than the number of optical channels in which the system itself operates, while maintaining the desired performance.

[0105] Furthermore, the optical systems described have the advantages provided by closed-loop control without requiring the high complexity of an actuator system controlled by a control device.

[0106] The small number of signals to be monitored means a reduction in the costs associated with the necessary components and in the physical dimensions of the control system, facilitating the packaging operation. A

Claims

1. An optical system (100; 400), comprising: A plurality of actuators (A １ ~A Ｎ ), having a number M of associated optical channels, and a number N of degrees of freedom, defined by the number of said actuators (A １ ~A Ｎ ) and being smaller than said number M of optical channels, a reconfigurable wavelength division multiplexed optical device (103); A stimulation light signal (S ｉｎ ) having a wavelength band including a plurality of wavelengths related to the optical channel, and a stimulation light source (106) connected to the reconfigurable optical device (103) for providing The monitoring optical signal (S ｉｎ ) generated in response to the stimulation optical signal (S ｏｕｔ ) is received from the reconfigurable optical device (103), and the intensity of the monitoring optical signal (S ｏｕｔ ) evaluated at each wavelength included in the wavelength band, and a group of intensity electrical signals (S ＥＬ１ to S ＥＬＫ ) each representing the intensity are provided, and a photoelectric conversion device (200) configured to: The group (S ＥＬ１ ~S ＥＬＫ ) of the intensity electrical signals, and in accordance with a control law, a control device (110) configured to control the plurality of actuators (A １ ~A Ｎ ), wherein the group (S ＥＬ１ ~S ＥＬＫ ) is selected based on the number of the degrees of freedom N and has a cardinality K included between a first minimum value K1min = N - 20%N and a first maximum value K1max = N + 100%N, and the cardinality K is smaller than the number M of the optical channels, the control device (110) and An optical system (100; 400) comprising the following.

2. The cardinality K is included between a second minimum value K2min = N - 5%N and a second maximum value K2max = N + 50%N, or The cardinality K is included between the second minimum value K2min and a third maximum value K3max = N + 20%N, The optical system (100; 400) according to claim 1.

3. The optical system (100; 400) according to claim 1, wherein the cardinality K is equal to the number of degrees of freedom N.

4. The control device (110) is configured to: said group (S ＥＬ１ ~S ＥＬＫ ) and the stimulation optical signal (S ｉｎ ), evaluate the effective transfer function of the said reconfigurable optical device (103), Compare the effective transfer function of the reconfigurable optical device (103) with a desired transfer function, generating a plurality of control signals (S １ to S Ｎ ) for the plurality of actuators (A １ to A Ｎ ) to cause the reconfigurable device (103) to have the desired transfer function １ to A Ｎ ), of the plurality of actuators (A １ to S Ｎ ) The optical system (100; 400) according to claim 1, configured as such.

5. The following method applied by the control device (110) to the effective transfer function and the desired transfer function: minimizing the mean squared error, non-linear optimization, genetic algorithm, particle swarm optimization, machine learning, using one of the methods of neural networks to define the plurality of control signals (S １ ~S Ｎ ), the optical system (100; 400) according to claim 4, which is configured to be.

6. The reconfigurable device (103) has: An operable input (101; 403) for an input optical signal (I), An operable output (102; 402) for an output optical signal (O) corresponding to the input optical signal (I), The stimulus input (111; 408) for receiving the stimulus optical signal (S ｉｎ ) and The monitoring optical signal (S ｏｕｔ ) and a monitoring output (112; 405) for providing the photoelectric conversion device (200) with the same The optical system (100; 400) according to claim 1, comprising the above.

7. The photoelectric conversion device (200) is configured to: Comprising a plurality of output optical ports (109), receiving the monitoring optical signal (S ｏｕｔ ), and delivering a plurality of sampled optical signals (S ｏｕｔ ), each corresponding to a portion of the monitoring optical signal (S Ｓ１ ~S ＳＫ ), to the plurality of output optical ports (109); The plurality of output optical ports (109) for receiving the plurality of sampled optical signals (S Ｓ１ to S ＳＫ ), and a plurality of electrical terminals (108) configured to transmit the group of intensity electrical signals (S ＥＬ１ to S ＥＬＫ ) to the control device (110), an optoelectronic converter (104) comprising The optical system (100; 400) according to claim 1, comprising the following.

8. The photoelectric conversion device (200) is configured to: The monitoring optical signal (S ｏｕｔ ), and a plurality of sampled optical signals (S ｏｕｔ ), respectively corresponding to the portions of the monitoring optical signal (S Ｓ１ to S ＳＫ ), are delivered to an output optical port (109) by serial transmission, and a wavelength variable filter (205) configured to do so. The optical detector (204) includes an electrical terminal (108) connected to the output optical port (109) for receiving the plurality of sampled optical signals (S Ｓ１ ~S ＳＫ ), and configured to transmit a group of the intensity electrical signals (S ＥＬ１ ~S ＥＬＫ ) to the control device (110) by serial transmission The optical system (100; 400) according to claim 1, comprising the following.

9. The reconfigurable device (103) is a two-port device having an operable input (101) for an input optical signal (I) and an operable output (102) for an output optical signal (O). The optical system (100; 400) has: A first optical circulator (401) having a first optical port (403) for receiving the input optical signal (I) from the outside, delivering the input optical signal (I) to the reconfigurable device (103), and receiving the monitoring optical signal (S ｏｕｔ ) from the reconfigurable device (103) at a second optical port (404) connected to the operable input (101), and a third optical port (405) for delivering the monitoring optical signal (S ｏｕｔ ) to the photoelectric conversion device (200), the first optical circulator (401); A second optical circulator (402), each first optical port (406) connected to the operable output (102), each second optical port (407) for externally providing the output optical signal (O), and the pump light signal (S ｉｎ ), and each third optical port (408) for receiving the pump light signal and transmitting the pump light signal to the reconfigurable optical device (103) by the operable output (102). The optical system (100; 400) according to claim 1, comprising the following.

10. The optical system (100; 400) according to claim 1, wherein the reconfigurable device (103) is a device belonging to the group of optical filters, equalization filters, dispersion compensation filters, FIR filters, IIR filters, lattice filters, and binary tree filters.

11. The optical system (100; 400) according to claim 10, wherein the reconfigurable device (103) comprises at least one of a binary tree interferometer, a lattice interferometer, an AWG (arrayed waveguide grating), a power splitter, a multimode interferometer, a directional coupler, and a y-branch optical component (Gi).

12. The plurality of actuators (A １ to A Ｎ ) includes at least one of a thermo-optic actuator, an electro-optic actuator, a piezoelectric actuator, an electro-absorption actuator, an electromechanical actuator, an electrochemical actuator, a complete optical actuator based on a linear optical effect, and a complete optical actuator based on a non-linear optical effect, the optical system (100; 400) according to claim 1.

13. The optical system (100; 400) according to claim 1, wherein at least the reconfigurable device (103) and the photoelectric conversion device (200) are fabricated by integrated optical technology.

14. wherein the reconfigurable device comprises a plurality of optical elements (Gi) adjustable by the plurality of actuators (A １ to A Ｎ ), and each optical element is configured to operate according to wavelength multiplexing technology, the optical system (100; 400) according to claim 1.

15. The optical system (100; 400) according to claim 1, wherein the excitation light source (106) is selected from the group including a superluminescent diode (SLD), ASE noise of a fiber amplifier, ASE noise of a semiconductor optical amplifier, a light source of the "supercontinuum laser" type, a laser array, a distributed feedback laser DFB, a fiber comb generator, and an integrated comb generator on an optical chip.

16. A method for reconfiguring an optical device, comprising: A plurality of actuators (A １ ~A Ｎ ), having a number M of associated optical channels and a number N of degrees of freedom, which is defined by the number of said actuators (A １ ~A Ｎ ) and is smaller than said number M of optical channels, to provide a wavelength division multiplexing type reconfigurable optical device (103). A stimulation optical signal (S ｉｎ ) having a wavelength band including a plurality of wavelengths associated with the optical channel is delivered to the reconfigurable optical device (103); Receiving, from the reconfigurable optical device (103), a monitoring optical signal (S ｉｎ ) generated in response to the stimulation optical signal (S ｏｕｔ ), and performing photoelectric conversion by providing a group (S ｏｕｔ ~S ＥＬ１ ~S ＥＬＫ ) of intensity electrical signals respectively representing the intensity of the monitoring optical signal (S ｏｕｔ ) evaluated at each wavelength included in the wavelength band. Said group (S ＥＬ１ ~S ＥＬＫ ) as a function of, and in accordance with a control law, controlling said plurality of actuators (A １ ~A Ｎ ) and including The group (S ＥＬ１ ~S ＥＬＫ ) is selected based on the number of degrees of freedom N, has a cardinality K included between a first minimum value K1min = N - 20%N and a first maximum value K1max = N + 100%N, and the cardinality K is smaller than the number M of the optical channels, method.

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