NL2021638B1 - Optical signal processing system - Google Patents
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- NL2021638B1 NL2021638B1 NL2021638A NL2021638A NL2021638B1 NL 2021638 B1 NL2021638 B1 NL 2021638B1 NL 2021638 A NL2021638 A NL 2021638A NL 2021638 A NL2021638 A NL 2021638A NL 2021638 B1 NL2021638 B1 NL 2021638B1
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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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
- G02B6/12009—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
- G02B6/12019—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes
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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
- G02B6/29346—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 wave or beam interference
- G02B6/2935—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means
- G02B6/29352—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means in a light guide
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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
- G02B6/29346—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 wave or beam interference
- G02B6/2935—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means
- G02B6/29352—Mach-Zehnder configuration, i.e. comprising separate splitting and combining means in a light guide
- G02B6/29355—Cascade arrangement of interferometers
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/21—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour by interference
- G02F1/225—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour by interference in an optical waveguide structure
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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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12159—Interferometer
Abstract
Optical signal processing system for processing at least one optical signal, including: -an input port (1) for receiving the signal; -an array of multi-mode interference couplers (Ml,M23) arranged for providing N Mach-Zehnder interferometer structures (MZIn) cascaded in series, the first of the cascaded Mach-Zehnder interferometer structures (MZI1) being connected to the input port (1), and each of the Mach-Zehnder interferometer structures being configured to provide a respective optical path difference; characterized in that the array of multi-mode interference couplers includes: - pairs of 1x2 multimode interference couplers (Ml), arranged such that a first input port and a second input port of a each Mach-Zehnder interferometer structure (MZIn) is provided by input ports of a pair of the 1x2 multimode interference couplers (Ml); wherein, in each Mach-Zehnder interferometer structure (MZIn), first output ports of respective first 1X2 multimode interference couplers are connected to respective input ports of subsequent 1X2 multimode interference couplers; Wherein each Mach-Zehnder interferometer structure (MZIn) includes a 2X3 multimode interference coupler (M23), wherein, in each Mach-Zehnder interferometer structure (MZIn), a second output port of each of the first 1X2 multimode interference couplers is connected to a respective input port of the respective 2X3 multimode interference coupler.
Description
Title: Optical signal processing system
The invention relates to an optical signal processing system for processing at least one optical signal.
Various detector systems are known from the prior art to process optical signals. Signals to be processed, or detected, can be e.g. sensor signals, concerning various types of sensors e.g. Fabry-Pérot cavity sensors, Fiber Bragg gratings, and/or modulated signals.
It is generally desired to detect such signals (e.g. signals having optical wavelength modulations) with high accuracy. In particular, it is preferred that both optical power modulation and signal phase can be determined. A standard approach is to measure an optical spectrum of the signal utilizing a spectrum analyzer, including electronically sampling the signal (digitalization), wherein the samples are electronically processed via an FFT (Fast Fourier Transform).
Sampling and electronic processing can lead to errors and loss of signal. The present invention aims to provide an improved means for optical signal processing. In particular, the invention aims accurate detection of an optical power modulation, wherein the phase can be determined, preferably independent of any fluctuating optical powers. Furthermore, it is desired to achieve this in case the signal, to be processed, includes multiple (mutually different) modulations.
According to an aspect of the invention, this is achieved by the features of claim 1.
Accordingly, there is provided an optical signal processing system for processing at least one optical signal, the system including:
-an input port for receiving the signal;
-an array of multi-mode interference couplers arranged for providing N Mach-Zehnder interferometer structures cascaded in series, the first of the cascaded Mach-Zehnder interferometer structures being connected to the input port, and each of the Mach-Zehnder interferometer structures being configured to provide a respective optical path difference;
wherein the array of multi-mode interference couplers includes:
- pairs of 1x2 multimode interference couplers, arranged such that a first input port and a second input port of a each Mach-Zehnder interferometer structure is provided by input ports of a pair of the 1x2 multimode interference couplers;
wherein, in each Mach-Zehnder interferometer structure, first output ports of respective first 1x2 multimode interference couplers are connected to respective input ports of subsequent 1x2 multimode interference couplers;
wherein each Mach-Zehnder interferometer structure includes a 2x3 multimode interference coupler, wherein, in each Mach-Zehnder interferometer structure a second output port of each of the first 1x2 multimode interference couplers is connected to a respective input port of the respective 2x3 multimode interference coupler.
In this way, the optical signal can be processed in an efficient manner, optically, in particular such that it can provide an optical Fourier Transform that also provides phase information. The optical structure of the system particularly does not include any active (e.g. electronic) components, wherein the FFT (Fast Fourier Transform), e.g. in the wavelength domain, can be achieved without complex FFT computer processing. In a preferred embodiment the system is configured to simultaneously detect the presence and/or a degree of a modulation frequency (i.e. in case of a modulated optical signal fed into the system), as well as a phase of that modulation frequency and preferably also an input power of the signal (i.e. a single power at or associated with respect to the input port of the system).
N is the positive integer number of Mach-Zehnder interferometer structures that is applied in the present optical processing structure. It is preferred that a relatively large number N of Mach-Zehnder interferometer structures is cascaded (in system according to claim 1), N for example being larger than 5 and preferably being larger than 10, for example 20 or more.
It should be observed that cascading MZIs (Mach-Zehnder interferometers) as such is known from the prior art, see for example the structures that are describedin US9140582B2 or US20090003838. However, those known structures lead away from the present invention and tackle different problems in a different manner.
According to a preferred embodiment of the present invention, each output port of the 2x3 multimode interference coupler can be connected to a respective terminal wave guide having a respective signal detector, e.g. a respective photodiode for providing a respective detector signal.
In this way, above-mentioned advantages can be achieved in a simple manner.
Also, the N Mach-Zehnder interferometer structures (MZIn) are preferably all configured to provide mutually different optical path differences. In this way, phase information (in particular concerning a modulated optical signal) can be determined
Preferably, the system includes at least one optical detector, connected to an output port of the system.
The optical detector can e.g. be or include one or more photodiodes or the-like as will be appreciated by the skilled person, wherein the detector can generate an electric detector signal (i.e. transform the optical signal into a respective electric signal) to be processed further by electronic signal processing means (e.g. a computer, processor or the-like).
According to a further embodiment, the system including an additional 1x2 multi-mode interference coupler, configured to provide said input port, wherein output ports of the additional 1x2 multi-inode interference coupler are connected to the input ports of a first pair of the 1x2 multimode interference couplers.
In this way, the input optical signal can be led into the subsequent optical components.
Additionally, the feeding of an optical signal to the optical processing structure can be achieved in various manners. In addition, in an example, the input port can be coupled to a plurality of signal sources, for example via an optical circulator.
As will be appreciated by the skilled person, the mentioned multimode interference couplers as such can be configured in various ways. For example, good results can be achieved in case the pairs of 1x2 multimode interference couplers have a split ratio x/y that is larger than 50/50, for example a 90/10 split ratio.
According to a further aspect of the invention, there is provided an equivalent system as the system that is defined by the features of claim 1, the equivalent system including: -an input port (1) for receiving the signal;
-a IxQ multimode interference coupler for optically connecting the input port to two sets of Q/2 waveguide structures (Rl, R2), Q preferably being an (even) integer >3, the first (Rl) of the waveguide structures providing mutually different (e.g. increasing) optical path differences and the second (R2) of the waveguide structures providing mutually constant optical paths, wherein output ports of the first and second waveguide structures are optically coupled to respective 2x3 multimode interference couplers for providing phase shifted convolution.
In this way, the above-mentioned advantages can be achieved as well, wherein the equivalent system can provide relatively low optical signal losses, in particular in case Q is relatively large. Also, for example, in case Q equals only 2, the second aspect of the invention can cover the first aspect, in particular in that the two sets waveguide structures can then include:
-an array of multi-mode interference couplers, the array including:
- pairs of 1x2 multimode interference couplers, wherein first output ports of respective first 1x2 multimode interference couplers are connected to respective input ports of subsequent 1x2 multimode interference couplers; wherein a second output port of each of the first 1x2 multimode interference couplers is connected to a respective input port of a said 2x3 multimode interference coupler. In this case, the first of the two sets of waveguide structures can be provided by one array of the 1x2 multimode interference couplers, providing corresponding additional optical path differences along the respective path. The second of the two sets of waveguide structures, can be provided by the other array of the 1x2 multimode interference couplers.
Further preferred embodiments are describedin the dependent claims. Non-limiting examples of invention will now be explained with reference to the drawings.
Figure 1 schematically depicts a standard approach of optical signal processing;
Figure 2A schematically depicts an embodiment of an processing system according to a first aspect of the present invention;
Figure 2B shows a detail Q of Figure 2A;
Figure 3 shows a graph indicating a high correlation of a signal s that is in phase with an MZI free spectral range;
Figure 4 shows a graph indicating a low correlation of a signal s' that is not in phase with an MZI free spectral range;
Figure 5 shows some examples, of an ideal system, resembling input and output of the system;
Figure 6 schematically shows the system configured for measuring multiple cavities simultaneously; and
Figure 7 schematically depicts an embodiment of an processing system according to a second aspect of the present invention;
In this application, corresponding or similar features are denoted by corresponding or similar reference signs.
Figure 1 generally depicts a simultaneous measurement according to a standard approach, regarding three sensors Si, S2, S3, for example a Fabry-Pérot sensor, interferometer and intra cavity sensor. Respective free spectral ranges are of the three sensors are schematically depicted by FSR1, FSR2 and FSR3 respectively. A free spectral range (FSR) at the input IP of the system is represented by FSRO. Detector signals from the three sensors Si, S2, S3 are fed, e.g. via an optical circulator, to an optical spectrum analyzer OSA providing an output (optical spectrum) G. Usually, the optical spectrum analyzer OSA is configured to sample and digitally process the optical signal that is fed to the analyzer, using electronic sampling, wherein the samples are processed in a FFT (fast fourier transform). The digitizing of the optical signals has the possibility of introducing noise, leading to a reduction of accuracy of the end result of the subsequent signal processing steps.
Figures 2A, 2B schematically show a system H that includes a plurality of MZIs, the system being is configured for, basically, providing an optical output signal resembling FFT processing. In particular the system is configured such that the FSR ‘frequency; in an input signal convolves with the free spectral ranges present in each MZI creating an output resembling a fourier spectrum.
The optical signal processing system includes an input port 1 for receiving the optical signal.
Further, there is provided an array of multi-mode interference couplers Ml,M23 arranged for providing N Mach-Zehnder interferometer structures MZIn cascaded in series (wherein n=l, 2, 3, ...., N). In the present example, each of the MZIn structures provides a respective detector channel of the system, each detector channel in particular providing a first channel port, a second channel port and a third channel port (wherein the three channel ports are provided with respective detectors TW). Multimode interference (MMI) couplers as such and arranging such MMIs to form MZIs is commonly known to the skilled person in the field of optical signal processing (see also e.g. US2009/0003838).
As follows from the present drawings, the first of the cascaded Mach-Zehnder interferometer structures MZIi is connected to the input port
1. Each of the Mach-Zehnder interferometer structures is to provide a respective optical path difference OPD, wherein the OPDs of all of the Mach-Zehnder interferometer structures MZIn preferably differ from each other (as in the present embodiment). Providing the optical path difference OPD can be achieved in various ways (e.g. by providing physically longer paths between respective input/output ports) as will be appreciated by the skilled person.
In the drawing, only three of the MZIs (i.e. three on a first) of the cascade are shown. Preferably, N is at least 10, and more preferably at least 20.
Advantageously, the array of multi-mode interference couplers includes:
- pairs of 1x2 multimode interference couplers Ml, arranged such that a first input port 3 and a second input port 4 of a each Mach-Zehnder interferometer structure MZIn is provided by input ports of a pair of the 1x2 multimode interference couplers Ml.
As follows from the drawings, in each Mach-Zehnder interferometer structure MZIn, first output ports 6 of respective first 1x2 multimode interference couplers are connected to respective input ports of subsequent 1x2 multimode interference couplers;
Further, each Mach-Zehnder interferometer structure MZIn includes a 2x3 multimode interference coupler M23. In each Mach-Zehnder interferometer structure MZIn, a second output port 7 of each of the first 1x2 multimode interference couplers is connected to a respective input port of the respective 2x3 multimode interference coupler.
Further, each output port 9 of the 2x3 multimode interference coupler is connected to a respective terminal wave guide having a respective photodiode TW, the three photodiodes TW of each MZI structure providing respective phase signals Pi, P2, P3. The detectors TW are configured to transmit respective detector signals (e.g. via wired or wireless communication links, not shown, as will be appreciated by the skilled person) to a central signal processing unit D (e.g. a computer, digital signal processor or the like) for further signal processing.
In this example, the N Mach-Zehnder interferometer structures MZIn are all configured to provide different respective optical path differences.
According to a further embodiment, the pairs of 1x2 multimode interference couplers Ml can have a split ratio x/y that is larger than 50/50, for example split ratio of at least 90/10. _In the split ratio x/y, x is the amount of light that is transmitted from the input port 3, 4 of the MMI to its first output port 6, and y is the amount of light that is transmitted from the input port3, 4 of the respective MMI to its second output port 7 (as will be appreciated by the skilled person).
In the present example the system includes an additional 1x2 multi-mode interference coupler M2, configured to provide said input port 1, wherein output ports of the additional 1x2 multi-mode interference coupler M2 are connected to the input ports 3, 4 of a first pair of the 1x2 multimode interference couplers Ml. Advantageously, there is also an optical path difference present in the optical paths between the input ports 3, 4 of the first pair of the 1x2 multimode interference couplers Ml and the output ports of the multi-mode interference coupler M2.
During operation, one or more optical signals to be processed are fed into the cascaded MMI system via the input port 1. Optionally, the input port 1 is coupled to a plurality of signal sources or sensors Si, S2, S3, for example via an optical circulator, such as in Figure 6. Similar to the situation represented in Fig. 1, the plurality of signal sources or sensors Si, S2, S3 can have mutally different spectral ranges FSR1, FSR2, FSR3.
As follows from the above, the system H preferably includes a plurality of optical detectors TW , connected to the output ports of the cascaded MZI system to detect respective signals from the respective MZI channels, and e.g. to provide an electric or electronic detector signals associated therewith. The detectors TW can be configured in various ways, including e.g. one or more photodiodes and respective electronic signal processing means (e.g. a computer, digital signal processor or the-like). For example, each of the MZI structures can be provided with a single detector, having e.g. three respective photodiodes, for detecting the signals of the respective three output ports 9.
Referring to Figures 2A, 2B, and following from the above, the first embodiment generally provides a plurality (N) of cascaded MZls, providing different (in this case increasing) OPDs. The system is configured such that during operation, a 3-phase relation can be used to determine transmitted power (not relevant), visibility (the presence of modulation in the optical input signal), and -importantly- phase (the phase of said modulation). As will be clear to the skilled person, a resolution of the system can also be determined by a wavelength range of the input 1.
In particular, the presence of a wavelength dependent modulation is measured by the visibility’ of the MZls (and not the present power in the MZI). Basically, the system provides a coherence measurement of the input signal, convoluted with the nth MZI transfer function (n=l, 2, 3, ...., N). Each of the 3-phase MMIs M23 is configured to causes a phase shifted convolution, and when the integrated optical power fluctuates significantly with this phase shift, it indicates a high correlation with the respective MZls transfer function; resulting in an interferometric visibility.
Figures 3 and 4 show this in more detail. See also the section ‘algorithm herebelow, explaining the respective algorithm that can be used for calculating signal phases and visibility V.
In particular, figure 3 shows the free spectral range of an MZIn of the present system (Fig. 2A, 2B), with the 3-phase difference, being in phase with a signal s. The signal s is represented by a continuous (sinusoid) line, whereas the FSR is indicated by dashed lines. Figure 4 shows the free spectral range of the MZL, with the 3-phase difference, wherein the FSR is not in phase with a signal s’ (indicated by continuous sinusoid line).
In Figure 3, as a consequence of the signal s being in phase with the free spectral range of the MZI, the difference VIS in the integrated levels (i.e. visibility) is large. However, in Figure 4, since the signal s’ is not in phase, the difference in the integrated level VIS is small. In particular, the system can provide 'matching' of frequencies± in case a wave/frequency matches with that of an OFT (Optical Fourier Transform) MZI, it will be visible in the contrast.
The system of Figure 2 can achieve that the free spectral range ‘frequency’ in the input signal convolves with the FSRs present in each of the MZIs (MZIi. MZINn). This creates outputs that resemble Fourier transform spectra. Examples of possible inputs and outputs (in an idealized system) are shown in Figures 5A, 5B, 5C, 5D.
For example, as is indicated in Figure 5A, an input signal sa in the form of an impulse function can result in that at each FSR frequency an interference is measured, that is: all frequencies are present. This is associated with a high coherence length.
In Fig. 5B, a small bandwidth source signal as input signal Sb, e.g. a boxcar signal, results in that only low FSRs frequencies will ‘measure’ it (sync function). In this case there is a relatively low coherence length.
In Fig. 5C, a wavelength oscillation sc, in this case a sine wave (time period T), leads to one specific resonance.
In Fig. 5D, a comb input signal s<i (time period T) leads to a respective comb signal. Et cetera.
In a further embodiment, the transform has also a function in terms of optical Fourier transform time domain; for example, each OPD of the MZIs can have a delay time (e.g. 10 pm FSR corresponds to about 2.7 nsec). The analysis works in the same way as above, and can now be considered in time scale, MHz, or the-like.
The invention provides various advantages. For example, no active components have to be present in the analysis structure (i.e. the cascaded MZI structure). A straightforward processing or calculation on an output signal can provide swift and accurate measurement results. This can be achieved without having to use complex electronic FFT processing, since a FFT is basically carried out optically. Moreover, the system can simultaneously detect the presence or degree of a modulation frequency, the phase of a modulation frequency, and input power. For example, the system can be used to measure or monitor multiple cavities simultaneously, provided that the cavities are ‘separated in frequency’ (FSRs). This is schematically depicted in Figure 6. Therein, the system H is optically connected to a plurality of optical sensors (e.g. cavities) Si, S2, S3 having respective free spectral ranges FSR1, FSR2, FSR3. A dashed arrow ΔΤ represents the frequency separation of the free spectral ranges of the sensors Si, S2, S3. The connection is achieved e.g. via an optical circulator OC and splitter SPL. A light source LS (e.g. a broad spectrum light source, such as a superluminescent diode light source or a different source type) is provided to illuminate the sensors Si, S2, S3 for simultaneously providing respective sensor signals, to be led to the input port 1 of the optical signal processing system H. An optical output 10 of the system H provides the optically processed signal, which can be further processed to determine e.g. phase of modulation frequencies concerning the sensor signals that were input to the system H.
Figure 7 shows an embodiment of a second aspect of the present invention. The embodiment of Figure 7 is an equivalent of the example shown in Figure 1.
In particular, the second embodiment H' includes an input port 1 for receiving the optical signal to be optically processed. Further, there is provided a single IxQ multimode interference coupler M2' for optically connecting the input port to two sets of Q/2 waveguide structures Rl, R2, Q being an even integer >1 (in the present drawing, Q=4). In this example, the first Rl of the waveguide structures provides mutually increasing optical path differences dl and the second R2 of the waveguide structures provides mutually constant optical paths. As an example, indicated in Figure. 7, an optical path of a first waveguide structure of the first set Rl can be L0, wherein the optical path of a subsequent second waveguide structure of the first set Rl can be LO+dl, and so on for the further optical paths of the further subsequent waveguide structure of the first set Rl.
As follows from Figure 7, pairs of wave guide structures, each pair including one of the first set Rl and one of the second set R2, are connected to respective 2x3 multimode interference couplers M23' for providing phase shifted convolution. To that aim, output ports 17 of the first and respective second waveguide structures are optically coupled to input ports of respective 2x3 multimode interference couplers M23' (for example via respective intermediate waveguides sections as follows from the drawing), wherein the output ports 9 of those couplers M23' are connected to a respective terminal photo diode TW, for providing the phase shifted convolution.
It is preferred that a relatively large number of waveguide structures is available, For example, it is preferred that Q>5, and more preferably Q>9. For example, Q can be at least 20. In an extra advantageous embodiment, the system includes an arrayed waveguide grating (AWG), for example instead of the multimode interference coupler M2' at the input of the system.
As in Figure 2A, the system H’ can be coupled to a suitable detector for receiving and processing a respective optical output signal.
An advantage of the second embodiment is that optical losses are relatively low.
The systems Η, H’ can have many different applications. The system can be used e.g. for measuring or monitoring Fabry-Pérot fibre-tip temperature sensors, for measuring force tip Fabry-Pérot sensors, for sensing Fabry-Pérot cavities, for measuring absolute position interferometry gaps (possible multiple gaps), and/or for measuring or monitoring multiple ring resonator sensors and/or Optical Coherence Tomography (OCT).
For example, the invention can be used to measure an absolute position of an optical cavity (in a practical range of e.g. 1- 200 mm), by looking at or seeking a match of resonance compared to (e.g. on-chip) cavities. In addition, the system can acquire phase information on the resonance, in particular generating a relative submicron displacement resolution.
As is mentioned before, the system Η, H’ can include a central signal processing unit D for processing detector signals that are provided from the various MZI channels (i.e. from the respective detectors TW). Referring to Figures 2, 3 and 4, the following algorithm can be followed to calculate signal phase and the visibility of the signal, concerning each MZIchannel (the calculation e.g. being carried out be the afore-mentioned signal processing unit D):
The three-phase signal Pn concerning each MZI channel can be represented by:
= Pg (1 + V ‘ CGS( 0 “ φη)) (1) wherein Pn is a resulting signal of the interfering waves (arbitrary units, a.u.), Po isn the mean signal of the interference, (a.u.), V is the interferometric visibility, i.e. the contrast of interference (-), Φ is the interferometric phase (rad) and φη is the interferometric phase difference between channels. For the 3-phase relation these values are n/3 pi, wherein n=0, 2, 4.
From these signals (for each MZI-channel/structure) the phase can be calculated by:
wherein Pi is the interference signal at channel port 1 (concerning the first detector TWi of the respective MZI), i.e. (pi=0(rad.), wdierein P? is the interference signal at channel port 2 (concerning the second detector TW? of the respective MZI), i.e. (p2=2/3n (rad), wherein P3 is the interference signal at channel port 3 (concerning the third detector TW3 of the respective MZI),
i.e. (p3=4/3n (rad).
Herein, as will be clear to the skilled person, for each MZI channel the following holds: P2-P3 = sqrt(3)*sin(cp ) and 2P1-P2-P3 = 3*cos((p ).
Further, the sum of system detector signals (e.g. of detector photodiodes) is proportional to the mean signal of the interference:
(3)
The above-mentioned visibility V can be calculated by:
p,____py i
I ƒ I x~’ z --1
3P0 cos($) I
This holds for each of the channels, that is provided by the several (N) MZIs of the system.
Thus, each of those channels can be viewed to be a discrete pixel (system output result). Each of the channels can provide amplityde A, phase φ, and said visibility V, which corresponds to the particular OPD of the respective channel. It follows that, similar to a Fourier Transform, at a certain frequency (in this case certain respective OPD value), an amplitude (herein: visibility) and a phase (phase φ) are determined.
In a very basic embodiment, the system only includes a single channel (i.e. a single MZI structure and three respective outputs of detectors TWi, TW‘2, TWb), however, that will only provide a single pixel. It is much more preferred to use a plurality of channels, i.e. respective MZI structures having mutually different OPDs, providing a respective plurality of “pixels”.
Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments.
For example, as will be appreciated by the skilled person, the optical signal processing system Η, H’ can be partly or entirely implemented 5 in or on a photonic integrated circuit.
Claims (13)
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090003838A1 (en) | 2007-06-27 | 2009-01-01 | Lucent Technologies Incorporated | Optical Data Communication System Having Reduced Pulse Distortion and Method of Operating the Same |
| US9140582B2 (en) | 2009-05-27 | 2015-09-22 | Silixa Limited | Optical sensor and method of use |
-
2018
- 2018-09-14 NL NL2021638A patent/NL2021638B1/en active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090003838A1 (en) | 2007-06-27 | 2009-01-01 | Lucent Technologies Incorporated | Optical Data Communication System Having Reduced Pulse Distortion and Method of Operating the Same |
| US9140582B2 (en) | 2009-05-27 | 2015-09-22 | Silixa Limited | Optical sensor and method of use |
Non-Patent Citations (4)
| Title |
|---|
| D. HILLERKUSS ET AL: "Simple all-optical FFT scheme enabling Tbit/s real-time signal processing", OPTICS EXPRESS, vol. 18, no. 9, 26 April 2010 (2010-04-26), US, pages 9324, XP055600261, ISSN: 2161-2072, DOI: 10.1364/OE.18.009324 * |
| GABRIELLA CINCOTTI: "Generalized fiber Fourier optics", OPTICS LETTERS, OPTICAL SOCIETY OF AMERICA, US, vol. 36, no. 12, 15 June 2011 (2011-06-15), pages 2321 - 2323, XP001563657, ISSN: 0146-9592, [retrieved on 20110615], DOI: 10.1364/OL.36.002321 * |
| HALL TREVOR J ET AL: "Universal photonic integrated circuit architecture: The discrete Fourier Transform case", 2016 PHOTONICS NORTH (PN), IEEE, 24 May 2016 (2016-05-24), pages 1, XP032944487, DOI: 10.1109/PN.2016.7537881 * |
| TAKIGUCHI K ET AL: "Optical OFDM demultiplexer using silica PLC based optical FFT circuit", OPTICAL FIBER COMMUNICATION - INCUDES POST DEADLINE PAPERS, 2009. OFC 2009. CONFERENCE ON, IEEE, PISCATAWAY, NJ, USA, 22 March 2009 (2009-03-22), pages 1 - 3, XP031468064, ISBN: 978-1-4244-2606-5 * |
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