CN112291033A - Wavelength division multiplexing optical cross-connect system - Google Patents
Wavelength division multiplexing optical cross-connect system Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0215—Architecture aspects
- H04J14/0219—Modular or upgradable architectures
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29331—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by evanescent wave coupling
- G02B6/29335—Evanescent coupling to a resonator cavity, i.e. between a waveguide mode and a resonant mode of the cavity
- G02B6/29338—Loop resonators
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0202—Arrangements therefor
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0202—Arrangements therefor
- H04J14/021—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
- H04J14/0212—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM] using optical switches or wavelength selective switches [WSS]
Abstract
A wavelength division multiplexing optical cross-connect system based on a double-micro-ring coupling Mach-Zehnder structure comprises an optical cross-connect chip and an automatic control device. The optical cross connection chip comprises an optical input coupler, an N wavelength division multiplexer, an MxM optical switch array and an optical output coupler; the automatic control device comprises a wide-spectrum laser module, an adjustable filtering module, a multi-channel electric signal output module, a multi-channel optical power acquisition module, an optical switch module and an upper computer module. The optical cross-connect chip simultaneously realizes the wavelength division multiplexing and demultiplexing functions by utilizing a serial double-micro-ring coupling Mach-Zehnder structure, and has the advantages of compact structure and halved control complexity. The automatic control device adopts wide-spectrum optical power monitoring and feedback, and carries a wavelength automatic alignment algorithm and an optical switch array routing path selection algorithm, so that rapid wavelength routing and path routing are realized, and the automatic control device has the advantages of simplicity, high regulation efficiency and the like.
Description
Technical Field
The invention relates to the field of integrated optoelectronics, in particular to a wavelength division multiplexing optical cross-connect system.
Background
In recent years, the continuously upgraded communication technology deeply fuses big data and cloud computing services into people's daily life, which causes exponential increase of the capacity of the optical fiber communication system. In order to meet the urgent needs of the above-mentioned situations, optical wavelength division multiplexing systems have come to be developed. In a wavelength division multiplexing system, a reconfigurable optical add-drop multiplexer is an efficient and reliable optical switching channel distribution and management tool, and a high-performance wavelength division multiplexing optical cross-connect chip is a core element of the reconfigurable optical add-drop multiplexer. For the wavelength division multiplexing optical cross-connect system, the existing implementation modes mainly include free space and on-chip integration, and the on-chip integration mode becomes a research hotspot of people in the field due to the advantages of compact size, large scale potential, low power consumption and the like.
A silicon-on-insulator (SOI) waveguide can realize a compact optical device because the waveguide bending radius can be as small as a micrometer scale due to its large refractive index difference, and the loss of the silicon waveguide is relatively low. Therefore, compared with the traditional micro-electro-mechanical systems (MEMS), liquid crystal on silicon (LCoS) and silicon dioxide planar waveguide link (SiO)2PLC), etc., SOI platforms are more popular in passive integrated optical device material selection.
A key element of wavelength division multiplexed optical cross-connect systems is an optical device with wavelength selective properties. Based on the SOI platform, researchers have designed a wavelength division multiplexing optical cross-connect chip composed of waveguide array grating (AWG) (Journal of Lightwave Technology, vol.30, No.4,2012), integrated nanopore waveguide (Nanobeam) (Journal of Lightwave Technology, vol.38, No.2,2020), cascaded micro-ring resonator (MRR) (OECC,2019), counter-coupler assisted micro-ring resonator (Journal of Lightwave Technology, vol.38, No.12,2020), and the like. Although they all implement the functions of wavelength division multiplexing and path routing, they all have undeniably some drawbacks, such as complex chip waveguide links based on AWG, large area, large insertion loss; the chip based on MRR and Nanobeam has low extinction ratio and is not enough to support the function of simultaneously realizing wavelength division and multiplexing by using a single unit; in particular, the Nanobeam structure has smaller process tolerance and is difficult to prepare by using a 180nm standard silicon photo process.
The double micro-ring coupling Mach-Zehnder interference structure can effectively overcome a series of problems, has a simpler structure than AWG, and has been provided with a case of large-scale integrated preparation on a standard silicon optical process platform (Journal of Lightwave Technology, Vol.36, No.2,2018); the unit device size is slightly larger than the cascade MRR but close to the Nanobeam; selective filtering of target wavelength can be realized by tuning the micro-ring resonators integrated on the two arms, so that the function of wavelength division multiplexing/demultiplexing is realized; most importantly, the wavelength division multiplexing unit has higher extinction ratio, and can simultaneously realize wavelength division and multiplexing functions by using one wavelength division multiplexing unit, thereby enabling the system on chip to be more compact. Based on the wavelength division multiplexing optical cross-connection chip based on the double-micro-ring auxiliary Mach-Zehnder interference structure, an optical cross-connection system with automatic wavelength and optical exchange path reconstruction is formed through an upper computer-external equipment combined control device.
Disclosure of Invention
Aiming at the urgent application requirements of the wavelength division multiplexing optical cross connection chip and system and the respective defects of the existing schemes, the invention provides a wavelength division multiplexing optical cross connection system. The system has the advantages of simple structure, easy scale, high reconfigurability, continuous and automatic setting of working wavelength and free path selection. Most importantly, the wavelength division multiplexing device of the chip has high extinction ratio, and a single unit has the functions of wavelength division and multiplexing, so that the number of calibration units is reduced by half, the complexity of a calibration system is reduced, and the chip has obvious application value.
In order to achieve the above object, the technical solution of the present invention is as follows:
a wavelength division multiplexing optical cross-connect system comprises a silicon-based optical chip and an automatic control device, and is characterized in that the silicon-based optical chip comprises M paths of optical input couplers, M groups of N wavelength division multiplexers, N groups of MxM optical switch arrays and M paths of optical output couplers, wherein the input ends of the M paths of optical input couplers and the input ends of the M groups of N wavelength division multiplexers are connected one by one, N wavelength division output ends of the N wavelength division multiplexers are connected with the appointed input ends of the corresponding N groups of MxM optical switch arrays, M output ends of each MxM optical switch array are respectively connected with the appointed multiplexing input ends of the M groups of N wavelength division multiplexers, and the output ends of the M groups of N wavelength division multiplexers and the M paths of optical output couplers are connected to output signal light. The automatic control device is composed of a wide-spectrum laser module, an adjustable filtering module, a multi-channel electric signal output module, a multi-channel optical power acquisition module, an upper computer module and an optical switch module. The output end of the wide-spectrum laser module is connected with the input end of the adjustable filtering module to perform band-pass filtering on the wide-spectrum light, the output end of the adjustable filtering module is connected with all the optical input couplers through an optical switch module, and the optical switch module is controlled by a routing path selection algorithm to switch optical signals to the specified optical input couplers. And the input end of the multichannel optical power acquisition module is connected with the output ends of all the M paths of optical output couplers. The upper computer module is respectively connected with the communication interfaces of the broad spectrum laser module, the adjustable filter module, the multi-channel electric signal output module and the multi-channel optical power acquisition module.
The wavelength division multiplexing optical cross-connect system is characterized in that the M paths of optical input couplers and the output couplers adopt a grating coupler structure to couple optical signals to the system on chip in a vertical coupling mode or adopt an inverted cone-shaped spot-size conversion structure to couple optical signals to the system on chip in a horizontal coupling mode.
The wavelength division multiplexing optical cross connection system is characterized in that the N wavelength division multiplexer is formed by connecting N double-micro-ring coupling Mach-Zehnder structures in series, namely a second output end of a previous-stage unit and a first input end of a next-stage unit are sequentially connected, and the first input end of the first stage and the second output end of the Nth stage are respectively an optical input end and an optical output end of the wavelength division multiplexer; the first output end of the double-ring coupling Mach-Zehnder structure on all the cascade structures is the wavelength division output end of the wavelength division multiplexer, and the second input end of the double-ring coupling Mach-Zehnder structure is the multiplexing input end of the wavelength division multiplexer. The double-micro-ring coupling Mach-Zehnder structure is composed of two input waveguides, two micro-ring resonators, a 2 multiplied by 2 equiarm Mach-Zehnder interferometer, four waveguide phase shifters and two optical output waveguides. The two micro-ring resonators are respectively coupled with two arms of the equal-arm Mach-Zehnder interferometer, and coupling parameters are the same; two waveguide phase shifters are integrated on the micro-ring resonators and used for adjusting and controlling phase difference of the two micro-ring resonators so as to change working wavelength and working state of the device. The rest two waveguide phase shifters are integrated on two arms of the 2 x 2 equal-arm Mach-Zehnder interferometer and used for regulating and controlling the phase difference between the two arms so as to further improve the roll-off and extinction ratio of the device; the waveguide phase shifter adopts structures such as a TiN thermal resistor or a semiconductor heater and the like, and realizes waveguide phase shift through a thermo-optic effect; or a P-I-N structure is adopted, and waveguide phase shift is realized through a carrier dispersion effect; and the electric signal input end of the waveguide phase shifter is connected with the output end of a multi-channel electric signal output module in the control device. The two input waveguides and the two output waveguides are used as two input ends and two output ends of the double-ring coupling Mach-Zehnder structure.
The WDM optical cross-connect system is characterized in that the MXM optical Switch array is composed of a plurality of 2 × 2 optical Switch units, input/output waveguides and waveguide cross-junctions, and adopts topologies including but not limited to Benes, Crossbar, Switch and Select, DLN, and PILOSS. The 2 multiplied by 2 optical switch unit can adopt structures such as a Mach-Zehnder interferometer, a micro-ring resonator, a multi-mode interferometer or a double micro-ring coupling-Mach-Zehnder interferometer; the waveguide cross-over junction adopts a multimode interferometer or a multilayer waveguide structure. The 2 x 2 optical switch unit integrates a waveguide phase shifter to realize waveguide phase shift, and adopts a thermo-optic effect or a carrier dispersion effect to adjust the optical switch unit to a cross state or a through state. And the electric signal input end of the waveguide phase shifter is connected with the output end of a multi-channel electric signal output module in the control device.
The broad spectrum laser module can simultaneously output stable optical signals in a specified wavelength range.
The adjustable filtering module can realize stable optical bandpass filtering under the condition of appointed central wavelength and bandwidth.
The wavelength division multiplexing optical cross-connect system is characterized in that the optical switch module can switch the input optical signal to any appointed output port of the optical switch module, and keeps enough large bandwidth and enough small insertion loss.
The multi-channel electrical signal output module can output electrical signals with specified voltage or specified power at the output end of the multi-channel electrical signal output module respectively, and the electrical signals include but are not limited to direct current or pulse width modulation electrical signals with certain frequency and adjustable duty ratio.
The multichannel optical power acquisition module can simultaneously acquire and display the average optical power value in real time, and the acquired optical power can be used for realizing the wavelength and routing path calibration of the system.
The upper computer module can control the wide-spectrum laser module to output an optical signal with specified power; the controllable adjustable filtering module can be controlled to realize optical signal filtering according to the specified central wavelength and bandwidth; the multi-channel electric signal output module can be controlled to output an electric signal with certain voltage or power at an appointed end; the optical power of the appointed end of the multi-channel optical power acquisition module can be acquired and uploaded in real time; the mutual communication can be realized through interfaces such as a serial port, a USB or a GPIB.
The upper computer module carries an automatic calibration algorithm of the N-wavelength division multiplexing optical cross-connect system and can be realized by MATLAB, Python or Labview. The automatic calibration algorithm comprises a wavelength automatic alignment algorithm of the N wavelength division multiplexer and a routing path selection algorithm of the M multiplied by M optical switch array. The wavelength automatic alignment algorithm is used for realizing the wavelength alignment of N different double-ring coupling Mach-Zehnder structures and can be realized by adopting a machine learning auxiliary transmission spectrum identification algorithm; the method can also be realized by adopting an unconstrained search algorithm such as a hill climbing algorithm, a gradient descent method, a simplex method, a simulated annealing algorithm or a particle swarm optimization algorithm based on average light power under the condition of wide-spectrum optical signal input. The routing path selection algorithm of the MxM optical switch array is used for calibrating the N MxM optical switch arrays to a specified optical switching path, and can be realized by violence search and optimization of waveguide phase shifters one by one, or by simultaneously tuning a plurality of waveguide phase shifters and adopting group optimization methods such as particle swarm optimization, simulated annealing, bacterial foraging optimization and the like.
Compared with the prior art, the invention has the following advantages:
1. the wavelength division multiplexing optical cross connection chip can realize monolithic integration on an SOI platform, has simple and compact structure and smaller chip size, is compatible with a CMOS (complementary metal oxide semiconductor) process, is favorable for reducing the manufacturing cost, and has diversified control modes.
2. The wavelength division multiplexing unit adopts a double-micro-ring coupling Mach-Zehnder structure, phase shifters are integrated on the micro-rings and the two arms, and the extinction ratio of the unit in a direct-through state at a target wavelength and the extinction ratio of the unit in a cross state at a non-target wavelength can be improved through the two groups of phase shifters.
3. The wavelength division multiplexing unit adopts a double-micro-ring complex Mach-Zehnder structure, and because the large extinction ratio can be realized through two groups of phase shifters, a single wavelength division multiplexing unit has the functions of wavelength division multiplexing and demultiplexing, so that the number of the wavelength division multiplexing units in the system is halved, and the complexity of a required control algorithm can be obviously reduced.
4. The MxM optical switch array for optical signal routing selection can be realized by a plurality of 2 x 2 switch units and low insertion loss and low crosstalk waveguide cross junctions in a blocking or non-blocking topological structure, optical signals with different wavelengths are routed through different MxM optical switch arrays, and crosstalk in the routing process can be effectively inhibited.
5. The invention adopts an external multi-channel optical power acquisition module, realizes target wavelength selection or routing path selection through a control program carried by an upper computer, transfers the complexity of a control system into an easily controlled software system, and avoids a complex digital control circuit.
Drawings
Fig. 1 is a general view of a wavelength division multiplexing optical cross-connect system of the present invention.
Fig. 2 is a structural diagram of a wavelength division multiplexing unit of the present invention.
Fig. 3 shows the phase relationship and transmission spectrum of two micro-rings when the wavelength division multiplexing unit of the present invention is in a normal operation state.
Fig. 4 is a structural diagram of the N-wavelength division multiplexer of the present invention.
Fig. 5 is a structural diagram of an embodiment 4 of the wavelength division multiplexing optical cross-connect system of the present invention, in which a 4 × 4 optical switch array employs a Double Layer (DLN) structure.
FIG. 6 is a general view of an automatic control device for N-wavelength division multiplexing optical cross-connect chips according to the present invention.
Fig. 7 is a flowchart of an automatic wavelength selection algorithm of a wavelength division multiplexer according to embodiment 4 of the present invention.
Fig. 8 is a flowchart of an automatic routing algorithm of a 4 × 4 mach-zehnder DLN optical switch array according to an embodiment of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and examples which, however, are capable of numerous forms and should not be construed as being limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Fig. 1 is a general view of a wavelength division multiplexing optical cross-connect system of the present invention. As shown in fig. 1, the wavelength division multiplexing optical cross-connect system of the present embodiment includes a wavelength division multiplexing optical cross-connect chip and a control device. The chip is composed of an M-path optical input coupler 101, M groups of N wavelength division multiplexers 102, N groups of M multiplied by M optical switch arrays 103 and M paths of optical output couplers 104. The M optical input couplers 101 are respectively connected with the signal input ends of the M groups of N wavelength division multiplexers 102, and the M (1 is not less than k and not more than M) th wavelength division output ends of the k (1 is not less than M and not more than N) th group of N wavelength division multiplexers 102 are respectively connected with the k input ends of the M groups of MxM optical switch arrays 103; the kth output end of the mth group of M × M optical switch arrays 103 is connected to the mth multiplexing input end of the kth group of N wavelength division multiplexers 102; finally, the signal output end of the N wavelength division multiplexer 102 is connected to the N optical output couplers 104.
The output end of the multi-channel electrical signal output module 3003 in the automatic control device 105 is connected to the electrical signal input ends of all the N wavelength division multiplexers 102 and all the M × M optical switch arrays 103, and the optical signal input end of the multi-channel optical power acquisition module 3004 in the automatic control device 105 is connected to the output ends of all the optical output couplers 104.
Fig. 2 is a structural diagram of a wavelength division multiplexing unit of the present invention, which shows a structural diagram of a dual micro-ring coupled mach-zehnder wavelength division multiplexing unit of the present embodiment, where the wavelength division multiplexing unit 102 is composed of two input waveguides 1001, two micro-ring resonators 1002, one 2 × 2 equi-arm mach-zehnder interferometer 1003, four waveguide phase shifters 1004, and two optical output waveguides 1005, and the two micro-ring resonators 1002 are respectively coupled with two arms of the 2 × 2 equi-arm mach-zehnder interferometer 1003 by the same parameters. Two of the four waveguide phase shifters 1004 are integrated on the two micro-ring resonators 1002 and are used for regulating and controlling the phase difference of the two micro-ring resonators 1002 so as to tune the working wavelength and state of the wavelength division multiplexing unit; the remaining two integrated waveguide phase shifters 1004 are disposed on two arms of the mach-zehnder interferometer 1003 for adjusting and controlling a phase difference between the two arms to improve an extinction ratio of the wavelength division multiplexing unit. The transmission characteristics of the device can be obtained by derivation through a transmission matrix method, and when the phase difference of the two micro-ring resonators 1002 meets a certain relation and the two arms of the Mach-Zehnder interferometer 1003 have no phase difference, the wavelength division multiplexing unit is in an ideal working state. This example shows the transmission spectrum in the ideal case, as shown in fig. 3, with the output optical signal at the through port in the bandwidth of about 0.4nm and the cross port in most of the remaining wavelength range.
Fig. 4 shows a structure diagram of the N-wavelength division multiplexer according to the embodiment, which is formed by cascading N double-microring coupled mach-zehnder interference structures. The left end of stage 1 of the wavelength division multiplexer 102 includes an input (out) waveguide and the right end of stage N includes an output (in) waveguide. The first input terminal of the kth (1< k < N) th stage wavelength division multiplexing unit is connected to the second output terminal of the kth-1 stage, and the second output terminal of the kth stage is connected to the first input terminal of the (k + 1) th stage. And the second output terminal of the kth stage serves as a signal output terminal of the wavelength division multiplexer 102 and the first input terminal of the kth stage serves as a signal input terminal of the wavelength division multiplexer 102. The second input ends of all the units are used as multiplexing input ends of the optical signals with different wavelengths, and the first output ends are used as wavelength division output ends of the optical signals with different wavelengths. It should be particularly noted that the dual micro-ring coupled mach-zehnder structure has symmetry, which also makes the structure of the wavelength division multiplexer 102 have symmetry, that is, the optical signal input and output thereof can be used interchangeably, and the corresponding wavelength division output and multiplexing input thereof can be used interchangeably, which makes each set of wavelength division multiplexer 102 have both wavelength division and multiplexing functions.
Taking a 4-wavelength division multiplexing optical cross-connect system as an example, as shown in fig. 5, each group of 4 × 4 optical switch arrays 103 is formed of 12 2 × 2 mach-zehnder optical switch units 2001, 16 input/output waveguides 2002, and 8 waveguide cross-junctions 2003 in a DLN structure, and each mach-zehnder optical switch unit has two-arm integrated waveguide phase shifters 2004, and the system uses 4 groups of 4 × 4 optical switch arrays. The m (1. ltoreq. m. ltoreq.4) th input terminal I of the kth (1. ltoreq. k. ltoreq.4) group 4X 4 optical switch array 103kmRespectively connected with the kth wavelength division output terminal (output optical signal wavelength lambda) of the mth group 4 wavelength division multiplexer 102k) Connecting; 4 output terminals O of the kth group 4 × 4 optical switch array 103kmRespectively with the kth multiplexing input terminal (input optical signal wavelength lambda) of the mth group 4 wavelength division multiplexer 102k) And (4) connecting.
The embodiment shows an overall diagram of an automatic control device for an N-wavelength division multiplexing optical cross-connect chip, as shown in fig. 6, including a broad spectrum laser module 3001, an adjustable filter module 3002, a multi-channel electrical signal output module 3003, a multi-channel optical power acquisition module 3004, an upper computer module 3005, and an optical switch module 3006. In the process of routing path and wavelength selection calibration, after the broad-spectrum laser module 3001 and the tunable filter module 3002 are connected to implement optical signal filtering, the optical switch module 3006 is switched to be connected to the designated input coupler 101 of the chip, the multichannel electrical signal output module 3003 is connected to the electrical signal input ends of the wavelength division multiplexer 102 and the mxm optical switch array 103, respectively, the multichannel optical power acquisition module 3004 is connected to the M output coupler 104 of the chip, respectively, and the upper computer module 3005 communicates with the broad-spectrum laser module 3001, the tunable filter module 3002, the multichannel electrical signal output module 3003, the multichannel optical power acquisition module 3004, and the optical switch module 3006 in a serial communication mode. In the calibration process, different routing paths and routing optical wavelengths are set through the upper computer module 3005; subsequently, the upper computer module 3005 locks the wavelength division multiplexing unit to be tuned and the corresponding mxm optical switch array unit in a lookup table manner; secondly, the upper computer module 3005 reads the optical power of the target output end through the multi-channel optical power acquisition module 3004, and the wavelength automatic selection of the routing optical signal is realized by using the wavelength automatic alignment algorithm 4001 based on the obtained optical power; the routing path selection algorithm 5001 is invoked to select the routing path of the M × M optical switch array 103.
The embodiment shows an automatic calibration algorithm of a 4-wavelength division multiplexing optical cross-connect system, which includes a routing path selection algorithm 5001 of a 4 × 4DLN mach-zehnder optical switch array and a wavelength automatic alignment algorithm 4001 of a 4-wavelength division multiplexer, and before the calibration algorithm is implemented, a lookup table of relationships between an optical switch path and related optical switch units and related wavelength division multiplexing units should be established.
This embodiment shows a flow of a wavelength automatic selection algorithm of a 4-wavelength division multiplexer, as shown in fig. 7, which is executed after the 4 × 4 optical switch array routing path calibration, and the specific steps are as follows:
s11, establishing a wavelength selection and routing relation, namely, the wavelength lambdak(k is 1,2,3,4) optical signal from Im(m ═ 1,2,3,4) to specified output On(n＝1,2,3,4)；
S12, determining the wavelength division unit WD used by the mth group of wavelength division multiplexers 102k；
S13, determining the multiplexing unit WM used by the nth group of wavelength division multiplexers 102k；
S14, filtering out the central wavelength lambda by using a wide-spectrum laser module 3001 through an adjustable filter module 3002kThe optical switch module 3006 is used to switch the narrow-band optical signal to the mth input coupler 101 of the chip, and the multi-channel optical power acquisition module 3004 is used to read the optical power P of the mth output coupler 104 in real timem；
S15, the optical power P collected in S14mWavelength division multiplexing units WD as an objective functionkThe phase shift amount of the waveguide phase shifter is used as an independent variable, namely, the voltage (power) of the electrical signal input to the waveguide phase shifter by the multi-channel optical signal output module 3003 is constrained and optimized, and the optical power P is obtainedmAdjusting to the minimum;
s16, filtering out the central wavelength lambda by using a wide-spectrum laser module 3001 through an adjustable filter module 3002kIs inputted from the nth input coupler 101, and the optical power P of the nth output coupler 104 is read in real time using the multi-channel optical power collecting module 3004n；
S17, the optical power P collected in S16nAs an objective function, a wavelength division multiplexing unit WMkThe phase shift amount of the waveguide phase shifter is used as an independent variable, namely, the voltage (power) of the electrical signal input to the waveguide phase shifter by the multi-channel optical signal output module 3003 is constrained and optimized, and the optical power P is obtainednIs adjusted to the minimum.
The embodiment shows an automatic routing algorithm of a 4 × 4DLN mach-zehnder optical switch array as shown in fig. 8, which is characterized by comprising the following specific steps:
s21, establishing a wavelength selection and routing relation, namely, establishing a wavelength lambdak(k is 1,2,3,4) optical signal from Im(m ═ 1,2,3,4) to specified output On(n＝1,2,3,4)；
S22, filtering out the central wavelength lambda by using a wide-spectrum laser module 3002 through an adjustable filter module 3003kAnd the bandwidth is about the whole free spectral range of the wavelength division multiplexing unit, and the optical signal is switched to the mth input coupler I of the chip by using the optical switch module 3006m；
S23, determining a switching path lambda through the lookup tablek-Im～OnAll optical switch units E of interestkm1,Ekp2,Ekn3They are respectively positioned at 1 st, 2 nd and 3 rd stages of the k-th group of 4 × 4DLN optical switch arrays and are respectively numbered as m, n and p;
s24, observing by using a multi-channel optical power acquisition module 3004Nth output coupler OnThe optical power of the terminal, as an objective function, of the three-level optical switch unit Ekm1,Ekp2,Ekn3The phase shift amount of all waveguide phase shifters, i.e. the voltage (power) of the electrical signal input to the waveguide phase shifter by the multi-channel optical signal output module 3003, is used as an argument for performing optimization by using a particle swarm optimization until O is observednThe optical power of the end is maximized.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention. Such variations, uses, or adaptations are intended to be within the meaning and range of equivalents of the general principles of the invention and include such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.
Claims (11)
1. A wavelength division multiplexing optical cross-connect system comprises a silicon-based optical chip and an automatic control device (105), wherein the silicon-based optical chip comprises M optical input couplers (101), M groups of N wavelength division multiplexers (102), N groups of MxM optical switch arrays (103) and M optical output couplers (104), the input ends of the M optical input couplers (101) and the M groups of N wavelength division multiplexers (102) are connected one by one, N wavelength division output ends of the N wavelength division multiplexers (102) are connected with the appointed input ends of the corresponding N groups of MxM optical switch arrays (103), M output ends of each MxM optical switch array (103) are respectively connected with the appointed multiplexing input ends of the M groups of N wavelength division multiplexers (102), the output ends of the M groups of N wavelength division multiplexers (103) are connected with the M optical output couplers (104) to output signal light, the automatic control device (105) is composed of a broad spectrum laser module (3001), an adjustable filter module (3002), a multi-channel electric signal output module (3003), a multi-channel optical power acquisition module (3004), an upper computer module (3005) and an optical switch module (3006); the output end of the broad spectrum laser module (3001) is connected with the input end of the adjustable filter module (3002) to perform band-pass filtering on broad spectrum light, the output end of the adjustable filter module (3002) is connected with all the optical input couplers (101) through an optical switch module (3006), the optical switch module (3006) is controlled by a routing path selection algorithm (5001) to switch optical signals to the specified optical input couplers (101), the input end of the multichannel optical power acquisition module (3004) is connected with the output ends of all the M paths of optical output couplers (104), the electrical signal output end of the multichannel electrical signal output module (3003) is connected with the N-wave long-wave wavelength division multiplexer (102) and all the electrical signal input ends of the M multiplied by M optical switch array (103), and the upper module (3005) is respectively connected with the broad spectrum laser module (3001), The adjustable filter module (3002), the multi-channel electric signal output module (3003), the multi-channel optical power acquisition module (3004) and the optical switch (3006) are connected through communication interfaces.
2. The wdm optical cross-connect system of claim 1, wherein the M-port optical input couplers (101) and the output couplers (104) couple optical signals to the system-on-chip using a grating coupler structure for vertical coupling or using an inverse tapered spot-size conversion structure for horizontal coupling.
3. The WDM optical cross-connect system according to claim 1, wherein the N WDM (102) is formed by connecting N double-micro-ring coupled Mach-Zehnder structures in series, i.e. the second output terminal of the previous stage unit and the first input terminal of the next stage unit are connected in sequence, and the first input terminal of the first stage and the second output terminal of the Nth stage are the optical input terminal and the optical output terminal of the WDM (102), respectively; the first output end of the double-ring coupling Mach-Zehnder structure on all the cascade structures is the wavelength division output end of the wavelength division multiplexer (102), the second input end of the double-ring coupling Mach-Zehnder structure is the multiplexing input end of the wavelength division multiplexer (102), the double-micro-ring coupling Mach-Zehnder structure is composed of two input waveguides (1001), two micro-ring resonators (1002), a 2 x 2 equiarm Mach-Zehnder interferometer (1003), four waveguide phase shifters (1004) and two optical output waveguides (1005), the two micro-ring resonators (1002) are respectively coupled with two arms of the equiarm Mach-Zehnder interferometer (1003), and coupling parameters are the same; two of the waveguide phase shifters (1004) are integrated on the micro-ring resonators (1002) and used for regulating and controlling the phase difference of the two micro-ring resonators (1002) to change the working wavelength and the working state of the device, and the remaining two of the waveguide phase shifters (1004) are integrated on two arms of a 2 x 2 equiarm Mach-Zehnder interferometer (1003)) and used for regulating and controlling the phase difference between the two arms to further improve the roll-off and extinction ratio of the device; the waveguide phase shifter (1004) adopts TiN thermal resistance or semiconductor heating structures and the like, and realizes waveguide phase shift through a thermo-optic effect; or a P-I-N structure is adopted, and waveguide phase shift is realized through a carrier dispersion effect; the electrical signal input end of the waveguide phase shifter (1004) is connected with the output end of a multi-channel electrical signal output module (3003) in the control device (105), and the two input waveguides (1001) and the two output waveguides (1005) are used as two input ends and two output ends of a double-ring coupling Mach-Zehnder structure.
4. The wdm optical cross-connect system of claim 1, wherein the mxm optical Switch array (103) is comprised of a plurality of 2 x 2 optical Switch cells (2001), input-output waveguides (2002), and waveguide cross-junctions (2003) using topologies including, but not limited to, Benes, Crossbar, Switch and Select, DLN, and PILOSS; the 2 x 2 optical switch unit (2001) can adopt structures such as a Mach-Zehnder interferometer, a micro-ring resonator, a multimode interferometer or a double micro-ring coupling-Mach-Zehnder interferometer; the waveguide cross junction (2003) adopts a multi-mode interferometer or a multi-layer waveguide structure; the 2 x 2 optical switch unit (2001) is integrated with a waveguide phase shifter (2004) to realize waveguide phase shift, and the optical switch unit is adjusted to be in a cross state or a through state by adopting a thermo-optical effect or a carrier dispersion effect; the electrical signal input end of the waveguide phase shifter (2004) is connected with the output end of a multi-channel electrical signal output module (3003) in the control device (105).
5. The wdm optical cross-connect system of claim 1, wherein said broad spectrum laser module (3001) is capable of simultaneously outputting a stable optical signal over a specified wavelength range.
6. The wdm optical cross-connect system of claim 1, wherein said tunable filter module (3002) is configured to achieve stable optical bandpass filtering at a given center wavelength and bandwidth.
7. The wdm optical cross-connect system of claim 1, wherein said multichannel electrical signal output module (3003) is capable of outputting electrical signals of specified voltage or specified power at its output, respectively, said electrical signals being in the form of but not limited to dc or pwm electrical signals with adjustable frequency duty cycle.
8. The wdm optical cross-connect system of claim 1, wherein said multi-channel optical power collection module (3004) collects and displays average optical power values simultaneously in real time, and the collected optical power is used to calibrate the wavelength and routing paths of the system.
9. The wdm optical cross-connect system of claim 1, wherein the optical switch module (3006) is capable of switching an input optical signal to any of its designated output ports while maintaining a sufficiently large bandwidth and a sufficiently small insertion loss.
10. The wdm optical cross-connect system of claim 1, wherein the host module (3005) is capable of controlling the broad spectrum laser module (3001) to output an optical signal of a predetermined power; the controllable adjustable filtering module (3002) can be controlled to realize optical signal filtering according to the specified central wavelength and bandwidth; the multi-channel electric signal output module (3003) can be controlled to output an electric signal with certain voltage or power at a specified end; the optical power of the appointed end of the multi-channel optical power acquisition module (3004) can be acquired and uploaded in real time; the mutual communication can be realized through interfaces such as a serial port, a USB or a GPIB.
11. The WDM optical cross-connect system of claim 1, wherein the host module (3005) is implemented with an auto-calibration algorithm for N-wavelength WDM optical cross-connect system, which can be implemented by MATLAB, Python or Labview; the automatic calibration algorithm comprises a wavelength automatic alignment algorithm (4001) of an N wavelength division multiplexer (102) and a routing path selection algorithm (5001) of an M multiplied by M optical switch array (103); the wavelength automatic alignment algorithm (4001) is used for realizing the wavelength alignment of N different double-ring coupling Mach-Zehnder structures, and can be realized by adopting a machine learning auxiliary transmission spectrum identification algorithm; the method can also be realized by adopting an unconstrained search algorithm such as a hill climbing algorithm, a gradient descent method, a simplex method, a simulated annealing algorithm or a particle swarm optimization algorithm based on average light power under the condition of wide-spectrum optical signal input. A routing path selection algorithm (5001) of an M × M optical switch array is used for calibrating N M × M optical switch arrays (103) to a specified optical switching path, and can be achieved through violence search optimization of waveguide phase shifters one by one, or through simultaneous tuning of a plurality of waveguide phase shifters and adoption of group optimization methods such as particle swarm optimization, simulated annealing and bacterial foraging optimization.
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